Chapter 18. The Forearm, Wrist, and Hand

At the completion of this chapter, the reader will be able to:

1. Describe the anatomy of the joints, ligaments, muscles, blood and nerve supply that comprise the forearm, wrist, and hand.

2. Describe the biomechanics of the forearm, wrist, and hand, including open- and close-packed positions, normal and abnormal joint barriers, and stabilizers.

3. Describe the purpose and components of the tests and measures for the forearm, wrist, and hand.

4. Describe the relationship between muscle imbalance and functional performance of the forearm, wrist, and hand.

5. Perform a comprehensive examination of the forearm, wrist, and hand, including palpation of the articular and soft-tissue structures, specific passive mobility and passive articular mobility tests, and stability tests.

6. Outline the significance of the key findings from the tests and measures and establish a diagnosis.

7. Summarize the various causes of forearm, wrist, and hand dysfunction.

8. Develop self-reliant intervention strategies based on clinical findings and established goals.

9. Evaluate the intervention effectiveness in order to progress or modify an intervention.

10. Plan an effective home program and instruct the patient in same.

A hand is a very personal thing. It is the interface between the patient and his or her world. It is an emblem of strength, beauty, skill, sexuality and sensibility. When it is damaged it becomes a symbol of vulnerability of the whole patient.

—Paul W. Brand (1914–2003)

In a sense, the shoulder, elbow, and wrist joints ( Fig. 18-1) are merely mechanical devices that contribute to the usefulness of the hand. 1The correct synchronization of these biological devices, coupled with patient motivation, produce a remarkable level of dexterity and precision.

The carpus, or wrist, represents a highly complex anatomic structure, comprising a core structure of 8 bones; more than 20 radiocarpal, intercarpal, and carpometacarpal (CMC) joints; 26 named intercarpal ligaments; and 6 or more parts of the triangular fibrocartilage complex (TFCC). 2While these structures can be differentiated anatomically, they are functionally interrelated with movement in one joint having an effect on the motion of neighboring joints. This relationship extends as far as the elbow.

The hand accounts for about 90% of upper limb function. 3The thumb, which is involved in 40–50% of hand function, is the more functionally important of the digits. 3The index and middle fingers are each involved in about 20% of hand function, and are the second most important, with the ring finger being the least important. The middle finger is the strongest finger and is important for both precision and power functions. 3

The following sections describe the respective bones, joints, soft tissues, and nerves, detailing both their individual and collective functions. For simplicity's sake, the forearm, wrist, and hand are separated into their various compartments.

Distal Radioulnar Joint

The distal radioulnar joint (DRUJ) plays an important role in wrist and forearm function. The DRUJ is a uniaxial pivot joint that joins the distal radius and ulna and an articular disk ( Fig. 18-1). The articular disk, known as the TFCC, assists in binding the distal radius and is the main stabilizer of the DRUJ (see next section). 4

At its distal end, the radius widens to form a broad concave articular surface. The articular surface has an ulnar inclination in the frontal plane, which averages 23 degrees, and a anterior (palmar) inclination in the sagittal plane, which averages 11 degrees. 5The distal end of the ulna expands slightly laterally into a rounded head and medially into an ulnar styloid process ( Fig. 18-1). The rounded head of the ulnar head contacts both the ulnar notch of the radius laterally and the TFCC distally. 6The ulnar styloid process is approximately one-half inch shorter than the radial styloid process, resulting in more ulnar deviation than radial deviation being available. 6The articular capsule, which attaches to the articular margins of the radius and ulna and to the disk enclosing the inferior radioulnar joint, is lax. Anterior (palmar) and posterior (dorsal) radioulnar ligaments strengthen the capsule anteriorly and posteriorly. Forearm supination tightens the anterior capsule and pronation tightens the posterior part, adding to the overall stability of the wrist. 7

The DRUJ functions to transmit the loads from the hand to the forearm.

Triangular Fibrocartilage Complex

The TFCC essentially comprises a fibrocartilage disk interposed between the medial proximal row and the distal ulna within the medial aspect of the wrist. 8The primary function of the TFCC is to enhance joint congruity and to cushion against compressive forces. Indeed the TFCC transmits about 20 percent of the axial load from the hand to the forearm. 7The broad base of the disk is attached to the medial edge of the ulnar notch of the radius, and its apex is attached to the lateral aspect of the base of the ulnar styloid process. The disk's anterior and posterior borders are thickened.

A number of ligaments originate from the TFCC and provide support to it. These include the ulnolunate and ulnotriquetral ligaments, the ulnar collateral and the radioulnar ligaments. Other structures that lend support to the TFCC include the following:

• The ulnocarpal ligaments.
• The sheath of the extensor carpi ulnaris (ECU) tendon, which is the only wrist tendon that broadly connects to the TFCC.

Both the superior and the inferior articular surfaces of the TFCC are smooth and concave. 8The disk separates the distal ulna from direct contact with the carpals but allows gliding between the carpals, disk, and ulna during forearm pronation and supination. 8, 9

The TFCC is innervated by branches of the posterior interosseous, ulnar, and posterior (dorsal) sensory ulnar nerves. 9

The Wrist

The wrist comprises the distal radius and ulna, eight carpal bones, and the bases of five metacarpals ( Fig. 18-1). The carpal bones lie in two transverse rows. The proximal row contains (lateral to medial) the scaphoid (navicular), lunate, triquetrum, and pisiform. The distal row holds the trapezium, trapezoid, capitate, and hamate.

Radiocarpal Joint

The radiocarpal joint, a biaxial ellipsoid joint, is formed by the large articular concave surface of the distal end of the radius, the proximal carpal row, and the TFCC. The lunate and triquetrum articulate with the TFCC. A radial styloid process projects distally from the lateral side of the radius. A cartilage-covered ulnar notch occupies the distal medial side of the radius. 10Posteriorly, a posterior (dorsal) (Lister's) tubercle arises near the center of the radius, forming a pulley around which the extensor pollicis longus (EPL) tendon passes. 9Lister's tubercle is a common site of attritional changes and potential tendon rupture. 11

The Carpals

Scaphoid

The scaphoid ( Fig. 18-1) is the largest of the proximal carpal row bones, and its shape resembles that of a boat or canoe (thus the old term navicular). 9The scaphoid bone links the proximal and distal carpal rows and helps provide stability to the wrist joint.

The scaphoid is tethered to the proximal carpal row by a number of strong ligamentous attachments, and two-thirds of its surface area is articular. The proximal surface of the scaphoid is convex and articulates with the radius. The medial surface is concave and articulates with the capitate. 10The articulating surface for the lunate is flat. The distal surface consists of two convex facets for articulation with the trapezium and trapezoid (the scaphotrapeziotrapezoid joint). 9The round tubercle on the inferolateral part of its anterior (palmar) surface serves as the attachment of the flexor retinaculum and the abductor pollicis brevis (APB). 10The blood vessels to this bone enter the scaphoid at or distal to the wrist. This configuration predisposes a fracture on the proximal aspect to aseptic necrosis. 12In addition, as the scaphoid plays a critical role in coordinating and stabilizing movements between the proximal and the distal rows of the carpals, damage to the intrinsic and extrinsic ligaments that support the scaphoid can result in persistent pain and dysfunction with loading activities. 13– 15

Lunate

The lunate ( Fig. 18-1) articulates between the scaphoid and the triquetrum in the proximal carpal row. Its smooth convex proximal surface articulates with the radius and the TFCC at the lunate fossa. 10Its lateral surface contains a flat semilunar facet for the scaphoid. The medial surface articulates with the triquetrum. The distal surface is deeply concave and articulates with the edge of the hamate in adduction and the medial aspect of the capitate. 10

Triquetrum

The triquetrum ( Fig. 18-1) is a pyramid-shaped bone. It articulates with the pisiform on its distal anterior (palmar) surface at the pisiform–triquetral joint. 10The almost square distal–medial surface of the triquetrum articulates with the concavo–convex surface of the hamate. The ulnar collateral ligament (UCL) attaches to the medial and posterior (dorsal) surfaces of the triquetrum. 10The proximal surface of the triquetrum articulates with the TFCC in full adduction. 9The lateral surface of the triquetrum articulates with the lunate.

Pisiform

The pisiform ( Fig. 18-1), as its name implies, is shaped like a “P” with a posterior (dorsal) flat articular facet for the triquetrum. 10The pisiform, formed within the tendon of the flexor carpi ulnaris (FCU), is a sesamoid bone and serves as an attachment for the flexor retinaculum, abductor digiti minimi (ADM), UCL, pisohamate ligament, and pisometacarpal ligament. The pisiform also functions to increase the flexion moment of the FCU. 9

As mentioned, the pisiform articulates with the anterior (palmar) surface of the triquetral and is thus separated from the other carpal bones, all of which articulate with their neighbors. The pisiform is closely related to the ulnar artery and nerve on its radial border, the nerve being the closer. 16

Trapezium

The trapezium ( Fig. 18-1) has a groove on its medial anterior (palmar) surface which contains the tendon of the flexor carpi radialis (FCR). 10To its margins are attached two layers of the flexor retinaculum. The opponens pollicis (OP) is between the flexor pollicis brevis (FPB) distally and the APB proximally. 10The lateral surface serves as an attachment site for the radial collateral ligament and capsular ligament of the first CMC joint. The distal articulating surface of the trapezium is saddle shaped. Medially, its concave surface articulates with the trapezoid, whereas more distally its convex surface articulates with the second metacarpal base. 10Proximally, its concave surface articulates with the scaphoid.

Trapezoid

The trapezoid ( Fig. 18-1) is small and irregular. The distal surface articulates with the grooved second metacarpal base. The medial surface articulates via a concave facet with the distal part of the capitate. The lateral surface of the trapezoid articulates with the trapezium, and its proximal surface articulates with the scaphoid bone. 10

Capitate

The capitate ( Fig. 18-1) is the most central and the largest of the carpal bones. Its distal aspect articulates with the third metacarpal base. Its lateral border articulates with the medial side of the second metacarpal base. 10The convex proximal head of the capitate articulates with the lunate and scaphoid. The medial surface of the head articulates with the lunate, and the lateral aspect of the head articulates with the scaphoid. 10Medially, the capitate articulates with the hamate.

With its central location, the capitate serves as the keystone of the proximal transverse arch. This arch is important to the prehensile activity of the hand. 9, 17, 18

Hamate

The hamate ( Fig. 18-1) is a cuneiform bone and contributes to the medial wall of the carpal tunnel. To the hook (hamulus) of the hamate is attached the flexor retinaculum. The hamate articulates with three carpal bones and two metacarpals. 9The medial surface articulates with the triquetrum and by association with the pisohamate ligament, the pisiform. The lateral surface articulates with the capitate. 10On its distal aspect the hamate articulates with the fourth and fifth metacarpal heads.

Midcarpal Joints

The midcarpal joint lies between the two rows of carpals. It is referred to as a “compound” articulation because each row has both a concave and a convex segment. Wrist flexion, extension, and radial deviation are mainly midcarpal joint motions. Approximately 50 percent of the total arc of wrist flexion and extension occur at the midcarpal level with more flexion (66 percent) occurring than extension (34 percent). 19

The proximal row of the carpals is convex laterally and concave medially. The scaphoid, lunate, trapezium trapezoid, and triquetrum present with a concave surface to the distal row of carpals. The scaphoid, capitate, and hamate present a convex surface to a reciprocally arranged distal row.

First CMC Joint

The thumb is the most important digit of the hand and greatly magnifies the complexity of human prehension. 20, 21Functionally, the sellar (saddle-shaped) CMC joint is the most important joint of the thumb and consists of the articulation between the base of the first metacarpal and the distal aspect of the trapezium.

The articular surfaces of the trapezium and the proximal end of the first metacarpal are reciprocally shaped. Three other adjacent articulations are functionally related to this joint, which include the joints between the trapezium and the scaphoid, the trapezium and the trapezoid, and the base of the first metacarpal and the radial side of the base of the second metacarpal. 20, 21

Motions that can occur at this joint include flexion/extension, adduction/abduction, and opposition, the latter of which includes varying amounts of flexion, internal rotation, and anterior (palmar) adduction (see “Biomechanics”). Although the joint capsule of the first CMC joint is large and relatively loose, motions at the joint are controlled and supported by muscle actions and by at least five ligaments: anterior oblique, ulnar collateral, intermetacarpal, posterior oblique, and radial collateral. In general, most of the thumb ligaments are placed on tension with abduction, extension, and opposition. 20, 21

Other CMC Joints

The distal borders of the distal carpal row bones articulate with the bases of the metacarpals, thereby forming the CMC joints. The CMC articulations of the fingers permit only gliding movements. The CMC joints progress in mobility from the second to the fifth, with the second and third metacarpal joints being relatively immobile, and thus the primary stabilizing joints of the hand. The fourth and fifth CMC joints are more mobile to permit the hand to adapt to objects of different shapes during grasping.

Stability for the CMC joints is provided by the anterior (palmar) and posterior (dorsal) CMC and intermetacarpal ligaments. While the trapezoid articulates with only one metacarpal, all of the other members of the distal carpal row combine one carpal bone with two or more metacarpals.

Metacarpophalangeal Joints

The five metacarpals resemble miniature versions of the long bones of the body, with elongated shafts and expanded ends. The metacarpophalangeal (MCP) joint of the thumb is a hinge joint. Its bony configuration, which resembles the interphalangeal (IP) joints, provides it with some inherent stability. In addition, support for the joint is provided by anterior (palmar) and collateral ligaments. The MCP joint of the thumb consists of a convex surface on the head of the metacarpal and a concave surface on the base of the phalanx. The area of the articulating surface is increased by the presence of a volar plate, which allows greater range of motion than would be available otherwise. Approximately 75–80 degrees of flexion is available at this joint. The extension movements as well as the abduction and adduction motions are negligible. Traction, gliding, and rotatory accessory movements are also present.

The second through fifth metacarpals articulate with the respective proximal phalanges within biaxial joints. Their widened, proximal bases articulate with the carpals and with one another in plane joints. 10Their biconvex distal heads are broader anteriorly than posteriorly, the significance of which is discussed later.

The MCP joints allow flexion–extension and medial–lateral deviation associated with a slight degree of axial rotation. The design of the MCP joint allows for great amplitude of movement, at the expense of stability.

Approximately 90 degrees of flexion is available at the second MCP, with the amount of available flexion progressively increasing toward the fifth MCP. Active extension at these joints is 25–30 degrees, while 90 degrees can be obtained passively. A loss of flexion and extension at the CMC joint of the little finger reduces the amount of opposition available, resulting in dysfunction of the prehensile pattern and difficulty in making a fist. 6Approximately 20 degrees of abduction/adduction can occur in either direction at the MCP, with more being available in extension than in flexion. Abduction–adduction movements of the MCP joints are restricted in flexion and free in extension.

The joint capsules are attached to the articular margins of the metacarpals and phalanges and surround the MCP joints. The joint capsule of these joints is relatively lax and redundant, but is endowed with collateral ligaments that pass posterior to the joint axis for flexion/extension of the MCP joints ( Fig. 18-11). Although, these collateral ligaments are lax in extension, they become taut in approximately 70–90 degrees of flexion of the MCP joint. 22

The posterior (dorsal) hood apparatus reinforces (or replaces) the posterior (dorsal) joint capsules. The fibrocartilaginous volar plates reinforce the anterior (palmar) aspects of the joints ( Fig. 18-12). The volar plates attach firmly to the phalangeal bases but connect only loosely to the metacarpal heads by membranous fibers. Their posterior (dorsal) surface contributes to the joint area, whereas their anterior (palmar) surface channels the finger flexor tendons. 23

The asymmetry of the metacarpal heads as well as the difference in length and direction of the collateral ligaments also explains the rotational movement of the proximal phalanx during flexion–extension and why the ulnar deviation of the digits normally is greater than the radial deviation. 23The rotary movements that occur are called conjunct rotations. The index finger has a conjunct rotation of internal rotation with abduction and flexion, whereas the ring and little finger each have a conjunct rotation of external rotation with abduction and flexion. The middle finger is not thought to have a conjunct rotation.

IP Joints

Adjacent phalanges articulate in hinge joints that allow motion in only one plane: sagittal. The congruency of the IP joint surfaces contributes greatly to IP joint stability. In addition, the IP joints are surrounded by joint capsules that are attached to the articular margins of the phalanges.

Proximal Interphalangeal Joint

The proximal interphalangeal (PIP) joint is a hinged joint capable of flexion and extension. The supporting ligaments and tendons provide the bulk of the static and dynamic stability of this joint as it travels through a normal range of 110 degrees. 22, 24– 27The capsule surrounding the articular surface of the joint is composed of the volar plate, lateral and accessory collateral ligaments, and extensor expansion.

The proximal IP joint is stable in all positions. The configuration of the volar plate allows it to function as a static restraint to hyperextension and to influence the mechanical advantage of the flexor tendons at the initiation of PIP joint flexion. 22The volar plate also increases the surface area. This allows for a greater range of motion than would be available otherwise.

The thick collateral ligaments (true and accessory) of the PIP joint combine with the volar plate to provide lateral stability: the collateral ligaments of the PIP joints are maximally taut at 25 degrees of finger flexion. 22For this reason, the IP joints are usually splinted in 25 degrees of flexion following surgery to prevent joint contractures. The splinting position is changed as the patient resumes function.

The flexor tendon system at the level of the PIP joint is less complex than the extensor mechanism and contributes very little to injuries about the PIP joint. 22

The phalangeal bases effectively form a sellar surface, with bone projections allowing for a wide range of accessory movements to accommodate the gripping of a large array of irregular surfaces.

The motions available at these joints consist of approximately 110 degrees of flexion at the PIP joints and 90 degrees at the thumb IP joint. Extension reaches 0 degrees at the PIP joints and 25 degrees at the thumb IP joint. Traction, gliding, and accessory movements also occur at the IP joints.

Distal Interphalangeal Joints

The distal interphalangeal (DIP) joint has similar structures as the PIP joint but less stability and allows some hyperextension. The motions available at these joints consist of approximately 90 degrees of flexion and 25 degrees of extension. Traction, gliding, and accessory movements also occur at the DIP joints.

Carpal Ligaments

Excessive migration of the carpal bones is prevented by strong ligaments ( Table 18-1) and by the ulnar support provided by the TFCC. The major ligaments of the wrist are depicted in Fig. 18-2.

The ligaments of the wrist provide support for the region. These ligaments can be divided into two types: extrinsic and intrinsic ( Table 18-1). The extrinsic anterior (palmar) ligaments provide the majority of wrist stability. The intrinsic ligaments serve as rotational restraints, binding the proximal row into a unit of rotational stability. 28The proximal row of carpals has no muscle insertions. Its stability depends entirely on the capsular and interosseous ligaments between the scaphoid, lunate, and triquetrum. 29The ligaments between the proximal and the distal carpal rows provide support, centering especially on the capitate. 10The midcarpal ligaments, which are longer than the interosseous ligaments, cross the midcarpal joint and connect bones of the distal and proximal rows on both the posterior (dorsal) and the anterior (palmar) surfaces. 9No midcarpal ligaments directly attach to the lunate.

Antebrachial Fascia

The antebrachial fascia is a dense connective tissue that encases the forearm and maintains the relationships of the tendons that cross the wrist. The fascia is firmly attached to the subcutaneous border of the ulna, from which it sends a septum to the radius. This septum divides the forearm into an anterior compartment and a posterior compartment (see Muscles of the Wrist and Forearm).

The Extensor Retinaculum

At the point where the tendons cross the wrist, there is a ligamentous structure called a retinaculum that appears to lay over the tendons and their sheaths ( Fig. 18-3). This retinaculum serves to prevent the tendons from “bowstringing” when the tendons turn a corner at the wrist. 30The extensor retinaculum extends from the lateral border of the distal radius across the posterior (dorsal) surface of the distal forearm onto the posterior surface of the distal ulna and ulnar styloid process. It then wraps part way around the ulna to attach to the triquetrum and pisiform bones. The retinaculum and the underlying bones form six tunnel-like structures called fibro-osseous compartmentson the dorsum of the wrist ( Fig. 18-3). The compartments, from lateral to medial, contain the tendons of

1. abductor pollicis longus (APL) and extensor pollicis brevis (EPB)

2. extensor carpi radialis longus (ECRL) and brevis (ECRB)

3. extensor pollicis longus (EPL)

4. extensor digitorum (ED) (four tendons) and extensor indicis (EI) (not shown)

5. extensor digiti minimi (EDM)

6. ECU.

As these tendons pass through the compartments, they are invested with synovial sheaths.

The posterior (dorsal) compartments serve to enhance the efficiency and effectiveness of the wrist and finger extensors (see “Extensor Hood”) ( Fig. 18-4). Proximal to the metacarpal heads, juncturae tendineae connect the four tendons of the ED muscles, limiting their independent motion. 6For example, flexion of the middle and little fingers restricts extension of the ring finger MCP joint because the juncturae tendineae pulls the ring finger extensor tendon distally. Conversely, extension of the ring finger exerts an extensor force upon its neighbors, such that they can be actively extended even if the middle and little finger extensor tendons are severed proximal to the juncturae. 6

The Flexor Retinaculum

The flexor retinaculum (transverse carpal ligament) spans the region between the pisiform, hamate, scaphoid, and trapezium, transforming the carpal arch into a tunnel, through which the median nerve and some of the tendons of the hand pass. ( Fig. 18-5) The proximal attachment of the retinaculum is at the tubercle of the scaphoid and the pisiform. The hook of the hamate and the tubercle of the trapezium serve as its distal attachment. The retinaculum also 6

• serves as an attachment site for the thenar and hypothenar muscles;
• helps maintain the transverse carpal arch;
• acts as a restraint against bowstringing of the extrinsic flexor tendons,
• protects the median nerve.

In the condition known as carpal tunnel syndrome (CTS), the median nerve is compressed in this relatively unyielding space (see “Intervention Strategies”). The structures that pass deepto the flexor retinaculum ( Fig. 18-5) include

• flexor digitorum superficialis (FDS),
• flexor digitorum profundus (FDP),
• flexor pollicis longus (FPL),
• flexor carpi radialis (FCR).

The structures that pass superficialto the flexor retinaculum include

• the ulnar nerve and artery,
• the tendon of the palmaris longus,
• the sensory branch (anterior (palmar) branch) of the median nerve.

Fibrous sheaths between the distal anterior (palmar) crease and the PIP joints bind the flexor tendons to the fingers. Some surgeons refer to the area where the sheaths contain two tendons as “no man's land.” 6

Carpal Tunnel

The carpal tunnel serves as a channel for the median nerve and nine flexor tendons ( Fig. 18-5). The floor of the tunnel is formed by the anterior (palmar) radiocarpal ligament and the anterior (palmar) ligament complex. As mentioned previously, the roof of the tunnel is formed by the flexor retinaculum. The radial and ulnar are formed by carpal bones (hook of hamate and trapezium, respectively). The median nerve divides into a motor branch and distal sensory branches within the tunnel.

Tunnel of Guyon

The tunnel of Guyon is located superficial to the flexor retinaculum, between the hook of the hamate and the pisiform bones. The anterior (palmar) carpal ligament, palmaris brevis muscle, and the anterior (palmar) aponeurosis form its roof. Its floor is formed by the flexor retinaculum (transverse carpal ligament), pisohamate ligament, and pisometacarpal ligament. 6The tunnel functions as a passageway for the ulnar nerve and artery into the hand.

Phalanges

The 14 phalanges each consist of a base, shaft, and head ( Fig. 18-1). Two shallow depressions, which correspond to the pulley-shaped heads of the adjacent phalanges, mark the concave proximal bases. Two distinct convex condyles produce the pulley-shaped configuration of the phalangeal heads. 6

Anterior (Palmar) Aponeurosis

The anterior (palmar) aponeurosis, which consists of a dense fibrous structure continuous with the palmaris longus tendon and fascia covering the thenar and hypothenar muscles, is located just deep to the subcutaneous tissue ( Fig. 18-5). The aponeurosis travels distally to attach to the transverse metacarpal ligaments and flexor tendon sheaths. The aponeurosis offers some protection for the ulnar artery and nerve, and digital vessels and nerves. From the central region of the palm, the aponeurosis continues toward the fingers and splits into four slips. As these slips approach the MCP joints, they split and wrap around the tendons of their respective digit. Dupuytren contracture is a fibrotic condition of the anterior (palmar) aponeurosis that results in nodule formation or scarring of the aponeurosis and which may ultimately cause finger flexion contractures (see “Intervention Strategies”).

Extensor Hood

At the level of the MCP joint, the tendon of the ED fans out to cover the posterior (dorsal) aspect of the joint in a hood-like structure ( Fig. 18-4). A complex tendon that covers the posterior (dorsal) aspect of the digits is formed from a combination of the tendons of insertion from the ED, EI, and EDM. The distal portion of the hood receives the tendons of the lumbricals and interossei over the proximal phalanx. The tendons of the intrinsic muscles pass anterior (palmar) to the MCP joint axes but posterior (dorsal) to the PIP and DIP joint axes ( Fig. 18-6). Between the MCP and the PIP joints, the complete, complex ED tendon (after all contributions have been received) splits into three parts: a central slip and two lateral bands 6:

• A central band.This band inserts into the proximal posterior (dorsal) edge of the middle phalanx.
• The lateral bands.These bands rejoin over the middle phalanx into a terminal tendon, which inserts into the proximal posterior (dorsal) edge of the distal phalanx. Rupture of the tendon insertion into the distal phalanx produces a “mallet” finger (see “Intervention Strategies”). The lateral bands, comprise fibers from both extrinsic and intrinsic tendons, are prevented from dislocating posteriorly (dorsally) by the transverse retinacular ligaments, which link them to the volar plates of the PIP joints. 6

The arrangement of the muscles and tendons in this expansion hood creates a cable-like system that provides a mechanism for extending the MCP and IP joints and allows the lumbrical and possibly interosseous muscles to assist in the flexion of the MCP joints.

Stretching or laxity of these supporting structures allows “bowstringing” of the lateral bands, which transmit excessive extension force to the PIP joint. 6

The oblique retinacular ligament (Landsmeer ligament) assists in the extensor hood mechanism. The ligament attaches between the PIP volar plate, where it is anterior (palmar) to the PIP joint axis, and the terminal tendon, where it is posterior (dorsal) to the DIP joint axis. This relationship to the PIP and DIP joints is essentially the same as that of the intrinsic muscles (lumbricals and interosseous) to the MCP and PIP joints—when the PIP joint extends, the oblique retinacular ligament exerts a passive extensor force on the DIP joint, and when the PIP joint flexes, it allows the DIP joint to flex. 31

PIP joint position also may influence DIP joint position through lateral band action. The lateral bands normally slip palmarly upon PIP joint flexion, decreasing the excursion required for full DIP joint flexion. If scar tissue tethers the lateral bands so that they do not move palmarly, then simultaneous full flexion at both the PIP and the DIP joints is not possible. 6

Synovial Sheaths

Synovial sheaths can be thought of as long narrow balloons filled with synovial fluid, which wrap around a tendon so that one part of the balloon wall (visceral layer) is directly on the tendon, while the other part of the balloon wall (parietal layer) is separate. 30During wrist motions, the sheaths move longitudinally, reducing friction.

At the wrist, the tendons of both the FDS and the FDP are essentially covered by a synovial sheath and pass posterior (dorsal) (deep) to the flexor retinaculum. The FDP tendons are posterior (dorsal) to those of the FDS.

In the palm, the FDS and FDP tendons are covered for a variable distance by a synovial sheath.

At the base of the digits, both sets of tendons enter a “fibro-osseous tunnel” formed by the bones of the digit (head of the metatarsals and phalanges) and a fibrous digital tendon sheath on the anterior (palmar) surface of the digits.

Flexor Pulleys

Annular (A) and cruciate (C) pulleys restrain the flexor tendons to the metacarpals and phalanges and contribute to fibro-osseous tunnels through which the tendons travel. 11The A1 pulley arises from the MCP joint and volar plate; A2 from the proximal phalanx; A3 from the PIP joint volar plate; A4 from the middle phalanx; and A5 from the DIP joint volar plate. 11The C1 pulley originates near the head of the proximal phalanx; C2 near the base of the middle phalanx; and C3 near the head of the middle phalanx. 11

The pulley system of the thumb includes the A1 arising from the MCP joint anterior (palmar) plate, A2 from the IP joint anterior (palmar) plate, and the oblique pulley from the proximal phalanx. 11

Anatomic Snuffbox

The anatomic snuffbox ( Fig. 18-7) is a depression on the posterior (dorsal) surface of the hand at the base of the thumb, just distal to the radius. This structure can be observed during active radial abduction of the thumb. The radial border of the snuffbox is formed by the tendons of the APL and EPB, while the ulnar border is formed by the tendon of the EPL. Along the floor of the snuffbox are the deep branch of the radial artery and the tendinous insertion of the ECRL. Underneath these structures, the scaphoid and trapezium bones are found.

The bones and soft tissues of the hand form a number of functional arches of the hand that provide a perfect balance of force distribution in an equiangular spiral. The arches of the hand, which are all concave palmarly, serve to enhance prehensile function. This prehensile function is best illustrated by the ability of the human hand to grasp an egg. A number of arches are commonly recognized:

• The transverse arch.The proximal, relatively immobile transverse arch is formed within the anterior (palmar) concavity of the carpal bones. 6This carpal arch, deepened by the anterior (palmar) projections of the scaphoid and trapezium laterally and the pisiform and hamate medially, should correspond to the concavity of the wrist. The distal transverse arch is more mobile and is defined by the alignment of the metacarpals. This arch allows the hand to adapt to objects held in the palm. 11
• The metacarpal arch.This arch, formed by the metacarpal heads, is a relatively mobile transverse arch.
• The longitudinal arch.This is specifically the arch of the middle finger and the arch of the index finger. The longitudinal arch, which contributes to powerful gripping, spans the hand lengthwise, with its keystone at the MCP joints. 6
• The oblique arches.These arches are formed by the thumb in opposition to the other fingers.

Muscles of the Wrist and Forearm

The muscles of the forearm, wrist, and hand ( Table 18-2) ( Figs. 18-8, 18-9, and 18-10) can be subdivided into 19 intrinsic muscles and 24 extrinsic muscles. 4The intrinsic muscles are located entirely within the hand; they arise and insert within the hand. The extrinsic muscles, whose muscle bellies lie proximal to the wrist, originate in the forearm and insert within the hand. The flexors, which are located in the anterior compartment, flex the wrist and digits while the extensors, located in the posterior compartment, extend the wrist and the digits.

The design of the extrinsic and intrinsic muscle groups provides for a large number of muscles to act on the hand without excessive bulkiness. The extrinsic tendons enhance wrist stability by balancing flexor and extensor forces and compressing the carpals.

The amount of tendon excursion determines the available range of motion at a joint. To calculate the amount of tendon excursion needed to produce a certain number of degrees of joint motion involves an appreciation of geometry. A circle's radius equals approximately 1 radian (57.29 degrees). The mathematical radius, which is equivalent to the moment arm, represents the amount of tendon excursion required to move the joint through 1 radian. 32For example, if a joint's moment arm is 10 mm, the tendon must glide 10 mm to move the joint 60 degrees (approximately 1 radian) or 5 mm to move the joint 30 degrees (½ radian). 11

Anterior Compartment of the Forearm

Superficial Muscles

Pronator Teres

The pronator teres is described in Chapter 17.

Flexor Carpi Radialis

The FCR originates from the medial humeral epicondyle as part of the common flexor tendon. It inserts on the anterior surface and base of the second metacarpal, possibly providing a slip to the third metacarpal. The FCR is innervated by the median nerve and functions to flex and radially deviate the wrist.

Palmaris Longus

The inconsistent palmaris longus arises from the medial humeral epicondyle as part of the common flexor tendon and inserts on the transverse carpal ligament and anterior (palmar) aponeurosis. It receives its innervation from the median nerve. The function of the palmaris longus is to flex the wrist, and it may play a role in thumb abduction in some people. 18

Flexor Carpi Ulnaris

The FCU arises from two heads. The humeral head arises from the medial humeral epicondyle as part of the common flexor tendon, while the ulnar head arises from the proximal portion of the subcutaneous border of the ulna. The FCU inserts directly onto the pisiform, the hamate via the pisohamate ligament, and onto the anterior surface of the base of the fifth metacarpal, via the pisometacarpal ligament. The FCU is innervated by the ulnar nerve and functions to flex and ulnarly deviate the wrist.

Intermediate Muscle

Flexor Digitorum Superficialis

The FDS has a three-headed origin. The humeral head arises from the medial humeral epicondyle as part of the common flexor tendon. The ulnar head arises from the coronoid process of the ulna. The radial head arises from the oblique line of the radius. The FDS inserts on the middle phalanx of the medial four digits via a split, “sling” tendon. This muscle is innervated by the median nerve and serves to flex the proximal and middle IP joints of the medial four digits and assist with elbow flexion and wrist flexion. The FDS possesses tendons that are capable of relatively independent action at each finger.

Deep Muscles

Flexor Pollicis Longus

The FPL has its origin on the ventral surface of the radius, medial border of the coronoid process of the ulna, and the adjacent interosseous membrane. It inserts on the distal phalanx of the thumb. The FPL is innervated by the anterior interosseous branch of the median nerve, and it functions to flex the thumb.

Flexor Digitorum Profundus

The FDP arises from the medial and anterior (ventral) surfaces of the proximal ulna, the adjacent interosseous membrane, and the deep fascia of the forearm. The FDP inserts on the base of the distal phalanges of the medial four digits. The FDP has a dual nerve supply: the medial two heads are supplied by the ulnar nerve, while the lateral two heads are supplied by the anterior interosseous branch of the median nerve. The FDP functions to flex the DIP joints, after the FDS flexes the second phalanges, and assists with flexion of the wrist. The tendons of the FDS and FDP are held against the phalanges by a fibrous sheath. At strategic locations along the sheath, the previously mentioned five dense annular pulleys (designated A1, A2, A3, A4, and A5) and three thinner cruciform pulleys (designated C1, C2, and C3) prevent tendon bowstringing. 33

Unlike the FDS tendons, the FDP tendons cannot act independently. To isolate the PIP joint flexor function of these two muscles, a clinician holds the adjoining finger(s) in extension while the patient attempts to flex the finger being tested. This anchors the profundus muscle of the finger being tested distally and allows the superficialis muscle to act alone at the PIP joint.

Tendinous connections between the FDP and the FPL are a common anatomic anomaly, which have been linked to a condition causing chronic forearm pain, called Linburg syndrome, 34although the association is by no means conclusive. 35

Pronator Quadratus

The pronator quadratus arises from the anterior (ventral) surface and distal quarter of the ulna and inserts on the anterior (ventral) surface and distal quarter of the radius. The muscle functions to pronate the forearm, and it is innervated by the anterior interosseous branch of the median nerve. The pronator quadratus is well-designed biomechanically as an effective torque producer and a stabilizer of the DRUJ—its line of force is oriented almost perpendicular to the forearm's axis of rotation. 36

Posterior Compartment of the Forearm

Superficial Muscles

Extensor Carpi Radialis Longus

The ECRL takes its origin at the supracondylar ridge of the humerus about 4–5 cm proximal to the epicondyle, and the thickest part of the muscle is proximal to the elbow joint. The ECRL inserts on the base of the second metacarpal and functions to extend and radially deviate the wrist. It also plays a role in elbow flexion, losing a part of its wrist action when the elbow is flexed. 23

Extensor Carpi Radialis Brevis

The ECRB arises from the common extensor tendon on the lateral epicondyle of the humerus (see Chap. 17) and from the radial collateral ligament. It inserts on the posterior surface of the base of the third metacarpal bone and receives its nerve supply from the posterior interosseous branch of the radial nerve. The muscle stretches across the radial head during forearm pronation, resulting in increased tensile stress when the forearm is pronated, the wrist is flexed, and the elbow is extended. The more medial location of the ECRB compared to the ECRL makes it the primary wrist extensor, but it has also a slight action of radial deviation.

ED and EDM

The ED arises from the lateral humeral epicondyle, part of the common extensor tendon, while the EDM arises from a muscular slip from the ulnar aspect of the ED muscle. The ED inserts on the lateral and posterior (dorsal) aspect of the medial four digits, while the EDM inserts on the proximal phalanx of the fifth digit. Both muscles are innervated by the posterior interosseous branch of the radial nerve. While the ED functions to extend the medial four digits, the EDM extends the fifth digit.

Extensor Carpi Ulnaris

The ECU arises from the common extensor tendon on the lateral epicondyle of the humerus and the posterior border of the ulna. It inserts on the medial side of the base of the fifth metacarpal bone. It is innervated by the posterior interosseous branch of the radial nerve. The ECU is an extensor of the wrist in supination and primarily causes ulnar deviation of the wrist in pronation, working in synergy with the FCU to prevent radial deviation during pronation. 23

Extension of the wrist is dependent on three muscles:

• ECRL
• ECRB
• ECU

The ECRB and ECRL are commonly considered to be similar muscles, but in fact they differ in many respects and have very different moment arms of extension. 37The ECRB, because of its origin on the epicondyle, is not affected by the position of the elbow, so that all of its action is on the wrist, making it the most effective extensor of the wrist (because it has the greatest tension and the most favorable moment arm). 23Taken together, both ECR tendons comprise about 10 percent of the muscle mass of the forearm and 76 percent of the muscle mass of the extensors of the wrist. 38The ECRL has longer muscular fibers, mostly at the level of the elbow. The ECRL only becomes a wrist extensor after radial deviation is balanced against the ulnar forces of the ECU.

The ECU, the antagonist of EPL, has the weakest moment of extension, which becomes zero when the wrist is in complete pronation.

Deep Muscles

Abductor Pollicis Longus

The APL arises from the posterior (dorsal) surface of the proximal portion of the radius, ulna, and interosseous membrane and inserts on the ventral surface of the base of the first metacarpal. The APL is innervated by the posterior interosseous branch of the radial nerve and functions in abduction, extension, and external rotation of the first metacarpal.

Extensor Pollicis Brevis

The EPB arises from the posterior (dorsal) surface of the radius and interosseous membrane, just distal to the origin of the APL. It inserts on the posterior (dorsal) surface of the proximal phalanx of the thumb via the extensor expansion. The EPB is innervated by the posterior interosseous branch of the radial nerve and functions to extend the proximal phalanx of the thumb.

Extensor Pollicis Longus

The EPL arises from the posterior (dorsal) surface of the midportion of the ulna and interosseous membrane. It inserts on the posterior (dorsal) surface of the distal phalanx of the thumb via the extensor expansion. The EPL is innervated by the posterior interosseous branch of the radial nerve. It functions in extension of the distal phalanx of the thumb and is thus involved in extension of the middle phalanx and the MCP joint of the thumb.

Extensor Indicis

The EI arises from the posterior (dorsal) surface of the ulna, distal to the other deep muscles, and inserts on the extensor expansion of the index finger. It is innervated by the posterior interosseous branch of the radial nerve and is involved in extension of the proximal phalanx of the index finger.

Muscles of the Hand

The muscles of the hand ( Fig. 18-11) are those that originate and insert within the hand and are responsible for fine finger movements.

Short Muscles of the Thumb

Abductor Pollicis Brevis

The APB arises from the flexor retinaculum and the trapezium bone and inserts on the radial aspect of the proximal phalanx of the thumb. It is innervated by the median nerve and functions to abduct the first metacarpal and proximal phalanx of the thumb.

Flexor Pollicis Brevis

The FPB arises from two heads. The superficial head arises from the flexor retinaculum and the trapezium bone, while the deep head arises from the floor of the carpal canal. The FPB inserts on the base of the proximal phalanx of the thumb. The superficial head receives its innervation from the median nerve, while the deep head is innervated by the ulnar nerve. The FPB functions to flex the proximal phalanx of the thumb.

Opponens Pollicis

The OP arises from the flexor retinaculum and the trapezium bone and inserts along the radial surface of the first metacarpal. The OP is innervated by the median nerve and functions to flex, rotate, and slightly abduct the first metacarpal across the palm to allow for opposition with each of the other digits.

Adductor Pollicis (AP)

The AP arises from two heads. The transverse head originates from the ventral surface of the shaft of the third metacarpal, while the oblique head originates from the trapezium, trapezoid, and capitate bones, and the base of the second and third metacarpal bone. The AP inserts on the ulnar side of the base of the proximal phalanx of the thumb and is innervated by the deep branch of the ulnar nerve. The AP functions to adduct the thumb and aids in thumb opposition.

Short Muscles of the Fifth Digit

Abductor Digiti Minimi

The ADM arises from the pisiform bone and the tendon of the FCU. It inserts on the ulnar aspect of the base of the proximal phalanx of the fifth digit, together with the flexor digiti minimi (FDM) brevis. It is innervated by the deep branch of the ulnar nerve and functions to abduct the fifth digit.

Flexor Digiti Minimi

The FDM originates from the flexor retinaculum and the hook of the hamate bone. It inserts on the ulnar aspect of the base of the proximal phalanx of the fifth digit, together with the ADM. It is innervated by the deep branch of the ulnar nerve and functions to flex the proximal phalanx of the fifth digit.

Deep branches of the ulnar artery and nerve enter the thenar mass and course into the deep region of the hand by passing between the ADM and the FDM.

Opponens Digiti Minimi (ODM)

The ODM arises from the flexor retinaculum and the hook of the hamate bone and inserts on the ulnar border of the shaft of the fifth metacarpal bone. It is innervated by the deep branch of the ulnar nerve and functions to provide a small amount of flexion and external rotation of the fifth digit.

Interosseous Muscles of the Hand

The interossei muscles of the hand are divided by anatomy and function into anterior (palmar) and posterior (dorsal) interossei.

Anterior (Palmar) Interossei

The three anterior (palmar) interossei have a variety of origins and insertions. The first interosseus originates from the ulnar surface of the second metacarpal bone and inserts on the ulnar side of the proximal phalanx of the second digit. The second anterior (palmar) interosseus arises from the radial side of the fourth metacarpal bone and inserts into the radial side of the proximal phalanx of the fourth digit. The third anterior (palmar) interosseus originates from the radial side of the fifth metacarpal bone and inserts into the radial side of the proximal phalanx of the fifth digit. The anterior (palmar) interossei are innervated by the deep branch of the ulnar nerve, and each muscle functions to adduct the digit to which it is attached toward the middle digit. The anterior (palmar) interossei also function to extend the distal and then the middle phalanges.

Posterior (Dorsal) Interossei

The four posterior (dorsal) interossei have a similar varied origin and insertion as their anterior (palmar) counterparts. The posterior (dorsal) interossei originate via two heads from adjacent sides of the metacarpal bones. The first posterior (dorsal) interosseus muscle inserts into the radial side of the proximal phalanx of the second digit. The second inserts into the radial side of the proximal phalanx of the third digit. The third inserts into the ulnar side of the proximal phalanx of the third digit and the fourth inserts into the ulnar side of the proximal phalanx of the fourth digit. The posterior (dorsal) interossei receive their innervation from the deep branch of the ulnar nerve. The posterior (dorsal) interossei abduct the index, middle, and ring fingers from the midline of the hand.

Lumbricals

The lumbrical muscles are usually four small intrinsic muscles of the hand that originate from the FDP tendons and insert into the posterior (dorsal) hood apparatus. Occasionally, more than four lumbricals are found in one hand. 39

During contraction, they pull the FDP tendons distally, thus possessing the unique ability to relax their own antagonist. 6They function to perform the motion of IP joint extension with the MCP joint held in extension and can assist in MCP flexion. 23

The lumbrical muscles also serve an important role in the proprioception of the hand, providing feedback about the position and movement of the hand and finger joints. 6

In instances of lumbrical spasm or contracture, attempts to flex the fingers via the profundus result in transmission of force through the lumbricals into the extensor apparatus, producing extension rather than flexion. 6A “lumbrical plus” deformity occurs if there is excessive lumbrical force or if there is imbalance of opposing forces, which produces exaggerated lumbrical action (i.e., MCP joint flexion and IP joint extension). 6

The lumbricals have dual innervation. Lumbricals I and II are innervated typically by the median nerve, while the third and fourth lumbricals are innervated by the ulnar nerve.

Neurology

The three peripheral nerves that supply the skin and muscles of the wrist and hand include the median, ulnar, and radial nerves ( Fig. 18-12).

Median Nerve

The median nerve enters the forearm by coursing anteriorly through the medial aspect of the cubital fossa and passing deep to the lacertus fibrosis, between the heads of the pronator teres muscle. Below the elbow, muscular branches leave the nerve and innervate the FCR, palmaris longus, and pronator teres muscles. The anterior interosseous branch innervates the pronator quadratus, FPL, and the FDP to the index finger and middle fingers and sometimes the ring finger.

Approximately 8 cm proximal to the wrist, the median nerve gives off a sensory branch, the anterior (palmar) cutaneous nerve that passes superficial to the flexor retinaculum and remains outside the carpal tunnel. This nerve innervates the skin in the central aspect of the palm, over the thenar eminence. The rest of the median nerve passes distally to the wrist, where it enters the carpal tunnel, which passes deep to the flexor retinaculum.

The nerve enters the hand through the carpal tunnel, deep to the tendon of the palmaris longus and in between the tendons of the FPL and FDS (the more radial of the two). From this point, the nerve divides into two branches: a motor branch which passes posterior (dorsal) to the flexor retinaculum and a sensory branch.

Motor Branch

This short branch enters the thenar eminence, where it usually supplies the APB and OP muscles, the FPB (occasionally), and the first and second lumbrical muscles.

Sensory Branch

The sensory anterior (palmar) digital branch innervates the anterior (palmar) surface and posterior (dorsal) aspect of the distal phalanges of the thumb, second and third fingers, and the radial half of the forefinger.

A number of median nerve entrapment syndromes exist (refer to “Peripheral Nerve Entrapment”), each with their own clinical features and functional implications. For example, entrapment of the median nerve in the carpal tunnel may result in numbness, pain, or paresthesia of the fingers and thumb and may severely hinder a patient's ability to perform precision maneuvers due to loss of critical sensory and motor function in the thumb, index, and middle fingers.

Ulnar Nerve

The ulnar nerve has been referred to as the nerve of fine movements of the hand. The ulnar nerve originates from the inferior roots of the brachial plexus (C 8–T 1). Two branches of the ulnar nerve arise in the midforearm:

1. The anterior (palmar) cutaneous branch.The anterior (palmar) cutaneous branch supplies a portion of the skin over the hypothenar eminence.

2. The posterior (dorsal) cutaneous branch.About 8–10 cm proximal to the ulnar styloid process, the posterior (dorsal) cutaneous branch of the ulnar nerve splits from the main trunk. The posterior (dorsal) cutaneous branch terminates into two posterior (dorsal) digital branches that supply sensation to the posterior (dorsal) and ulnar aspect of the middle phalanx of the ring and little fingers. 40

Before reaching the wrist, the ulnar nerve branches to innervate the FDP and the FCU.

At the wrist, the ulnar nerve emerges just lateral to the tendon of the FCU as it passes superficial to the flexor retinaculum. The ulnar nerve passes into the hand via the tunnel of Guyon, where it divides into its superficial and deep terminal branches. The deep (motor) branch supplies the FDM, ADM, ODM, AP, palmaris brevis, third and fourth lumbricals, deep head of the FPB, and the interossei. The superficial branch, which is primarily sensory with the exception of its innervation to the palmaris brevis, divides into three branches. 40The first of these three branches is a sensory branch to the ulnar aspect of the little finger, and the second is a sensory branch to the central ulnar anterior (palmar) area. The third branch, often referred to as the common digital nerve, innervates the fourth intermetacarpal space. The common digital nerve further divides into two proper digital nerves supplying the ulnar portion of the ring finger and the radial portion of the little finger. 40

A number of ulnar nerve entrapment syndromes exist (refer to “Peripheral Nerve Entrapment”), each with their own clinical features and functional implications.

Radial Nerve

As the radial nerve enters the cubital fossa, it typically splits into a superficial and deep branch. The superficial branch typically courses distally along the lateral border of the forearm under cover of the brachioradialis muscle and tendon. At the wrist this branch divides into four to five digital branches, which provide cutaneous and articular innervation. The cutaneous innervation includes the lateral two-thirds of the dorsum of the hand and the posterior (dorsal) lateral 2½ fingers to the proximal phalanx.

All of the motor branches of the radial nerve are located in the forearm. The deep branch (posterior interosseous nerve) typically penetrates the anterior (ventral) surface of, and passes through, the supinator muscle. It reaches the deep region of the posterior forearm by passing through the arcade of Fröhse. The nerve courses subcutaneously from the midportion of the forearm to an area adjacent to the styloid process of the radius and terminates on the posterior aspect of the wrist.

Vasculature of the Wrist and Hand

The brachial artery bifurcates at the elbow into radial and ulnar branches, which are the main arterial branches to the hand ( Fig. 18-13).

Radial Artery

The radial artery is formed from the lateral branch of the bifurcation of the brachial artery. The artery gives off branches in the proximal portion of the forearm that form an anastomosis around the elbow joint. It runs distally under the cover of the brachioradialis muscle. Just proximal to the wrist, it is located between the brachioradialis and the FCR tendons. A small branch called the superficial anterior (palmar) artery leaves the radial artery 5–8 mm proximal to the tip of the radial styloid, passes between the FCR and the brachioradialis, and continues distally to contribute to the superficial anterior (palmar) arch, which supplies the thenar mass. The radial artery has seven major carpal branches: three posterior (dorsal), three anterior (palmar), and a final branch that continues distally (see below).

Ulnar Artery

The ulnar artery originates as the medial branch from the bifurcation of the brachial artery. It too gives off branches in the proximal portion of the forearm that form an anastomosis around the elbow joint. The artery passes posterior (dorsal) to the ulnar head of the pronator teres and courses distally deep to the FDS, at which point it passes in the groove between the FCU and FDP, in the company of the ulnar nerve. In the proximal portion of the forearm, the artery gives off a common interosseous branch. The artery bifurcates, giving rise to the anterior and posterior interosseous arteries, which provide blood to structures in the deep anterior and posterior compartments of the forearm. The artery emerges at the wrist, just lateral to the tendon of the FCU. It then passes through the tunnel of Guyon and enters the superficial compartment of the hand. At the level of the carpus, the ulnar artery gives off a latticework of fine vessels that span the posterior (dorsal) and anterior (palmar) aspects of the medial carpals. Proximal to the end of the ulna, there are three branches: a branch to the posterior (dorsal) radiocarpal arch, one to the anterior (palmar) radiocarpal arch, and one to the proximal pole of the pisiform and to the anterior (palmar) aspect of the triquetrum. 41

Vascular Arches of the Hand

Posterior (Dorsal) Arches

The posterior (dorsal) arches are connected longitudinally at their medial and lateral aspects by the ulnar and radial arteries. They are connected centrally by the posterior (dorsal) branch of the anterior interosseous artery. There are three posterior (dorsal) transverse arches: the radiocarpal, the intercarpal, and the basal metacarpal 41:

• Posterior (dorsal) radiocarpal.The radiocarpal arch is supplied by branches of the radial and ulnar arteries and the posterior (dorsal) branch of the anterior interosseous artery.
• Posterior (dorsal) intercarpal.The posterior (dorsal) intercarpal arch has a variable supply, which can include the radial, ulnar, and anterior interosseous arteries.
• Basal metacarpal.The basal metacarpal arch is supplied by perforating arteries from the second, third, and fourth interosseous spaces. It contributes to the vascularity of the distal carpal row through anastomoses with the intercarpal arch.

Anterior (Palmar) Arches

Similar to the posterior (dorsal) vascularity, the anterior (palmar) vascularity is composed of three transverse arches: the anterior (palmar) radiocarpal, the anterior (palmar) intercarpal, and the deep anterior (palmar) arch 41:

• Anterior (palmar) radiocarpal.This arch supplies the anterior (palmar) surface of the lunate and triquetrum.
• Anterior (palmar) intercarpal.This arch is small and is not a major contributor of nutrient vessels to the carpals.
• Deep anterior (palmar).This arch contributes to the radial and ulnar recurrent arteries and sends perforating branches to the posterior (dorsal) basal metacarpal arch and to the anterior (palmar) metacarpal arteries.

The wrist is the key joint of the hand and contains several segments whose combined movements create a total range of motion that is greater than the sum of its individual parts. 23The osteokinematics of the wrist are limited to two degrees of freedom: flexion–extension and ulnar–radial deviation ( Fig. 18-14). Wrist circumduction—a full circular motion made by the wrist—is a combination of these movements. 42The apparent axial rotation of the palm—called pronation and supination—occurs at the proximal and DRUJs, with the hand moving with the radius, not separately from it. 42

Pronation and Supination

The true axis for pronation–supination at the wrist may be situated anywhere between the radial and ulnar styloid, resulting in not one, but many pronation–supination axes. 43, 44

• Approximately 75–90 degrees of forearm pronation is available. During pronation, the concave ulnar notch of the radius glides around the peripheral surface of the relatively fixed convex ulnar head. Pronation is limited by the bony impaction between the radius and the ulna.
• Approximately 85–90 degrees of forearm supination is available. Supination is limited by the interosseous membrane and the bony impaction between the ulnar notch of the radius and the ulnar styloid process.

Congruency of the DRUJ surfaces is maximal at midrange of motion, although the joint is not considered to be truly locked in this position. 6At this position, the TFCC is maximally stretched and the interosseous membrane is relatively lax.

The proximal and DRUJs are intimately related biomechanically, with the function and stability of both joints dependent on the configuration of, and distance between, the two bones. This configuration and distance maintains ligament and muscle tension. 45A change in the length of the ulna of as little as 2 mm results in a change in the transmission of forces of 5–40 percent. 46

Movement of the Hand on the Forearm

Due to the morphology of the wrist, movement at this joint complex involves a coordinated interaction between a number of articulations. These include the radiocarpal joint, the proximal row of carpals, and the distal row of carpals. All of these joints permit motion to occur around two axes: anterior–posterior in flexion–extension, and transverse in radial and ulnar deviation. Wrist extension is accompanied by a slight radial deviation and pronation of the forearm. Wrist flexion is accompanied by a slight ulnar deviation and supination of the forearm.

A number of concepts have been proposed over the years to explain the biomechanics of wrist motion. 47– 60The essential kinematics of the sagittal plane involve the mechanism of the carpal bone motions related to the central column of the wrist formed by the series of articulations among the radius, lunate, capitate, and third metacarpal bone. 42Within this concept

• the radiocarpal joint is represented by the articulation between the radius and lunate composed of the radius, scaphoid, trapezoid, trapezium, and the column of the thumb;
• the CMC joint is assumed to be a rigid articulation between the capitate and the base of the third metacarpal;
• The ulnar or medial compartment of the midcarpal joint is represented by the articulation between the lunate and capitate. This column strongly supports the movements in the central column, while simultaneously anchoring the wrist to the radius. 48

Under the column concept, the radial and ulnar columns are proposed to move with the central column due to mutual displacements between the proximal facets of the scaphoid and lunate. In addition, the proximal carpals are considered to move at the radiocarpal and midcarpal levels. 23, 49

Flexion and Extension Movements of the Wrist

The movements of flexion and extension of the wrist are shared between the radiocarpal articulation and the intercarpal articulation in varying proportions. 19The arthrokinematics are based on synchronous convex-on-concave rotations at the radiocarpal and midcarpal joints. 42

• During wrist extension, most of the motion occurs at the radiocarpal joint (66.5 percent or 40 degrees versus 33.5 percent or 20 degrees at the midcarpal joint) and is accompanied with slight radial deviation and pronation of the forearm. 19
• During wrist flexion, most of the motion occurs in the midcarpal joint (60 percent or 40 degrees, versus 40 percent or 30 degrees at the radiocarpal joint) and is accompanied with slight ulnar deviation and supination of the forearm. 19

Extension

At the radiocarpal joint, extension occurs as the convex surface of the lunate rolls posteriorly (dorsally) on the radius and simultaneously slides anteriorly (palmarly). 42Rotation directs the lunate's distal surface in an extended, posterior (dorsal) direction. At the midcarpal joint, the head of the capitate rolls posteriorly (dorsally) on the lunate and simultaneously slides in an anterior (palmar) direction. 42When the wrist is extended, the radiolunotriquetral and radiocapitate ligaments are stretched and tension develops within the wrist and finger flexor muscles. Tension within the structures stabilizes the wrist in its close-packed position of extension. 42, 61, 62

Loss of active extension in the wrist constitutes a considerable functional impairment, including the following 23:

• A reduction in grip strength.
• Changes in muscle length-tension relationships, which has serious implications when considering the action of the extrinsic muscles of the hand. For example, the strength of the thumb and finger flexors requires normal motion and function of wrist extension.

Flexion

The arthrokinematics of wrist flexion are similar to those described in extension, but occurs in a reverse fashion.

Frontal Lateral Movements of the Wrist

Like flexion and extension, the movements of ulna and radial deviation of the wrist are shared between the radiocarpal articulation and the intercarpal articulation in varying proportions ( Fig. 18-15). 19The amount of deviation is approximately 40 degrees of ulnar deviation and 15 degrees of radial deviation. There is a physiological ulnar deviation at rest, which is easily demonstrated clinically and radiographically.

Ulnar Deviation

Ulnar deviation occurs primarily at the radiocarpal joint. 62When the hand is observed at rest, there is a physiological ulnar deviation. During ulnar deviation, the radiocarpal and midcarpal joints contribute fairly equally to the overall motion ( Fig. 18-15). 42At the radiocarpal joint, the scaphoid, lunate, and triquetrum roll ulnarly and slide a significant distance radially. 42Ulnar deviation of the midcarpal joint occurs primarily from the capitate rolling ulnarly and sliding slightly radially. 42Ulnar deviation is limited by the radial collateral ligament. 62Although ulnar deviation brings the triquetrum into contact with the TFCC, the lack of direct ulnar-triquetral articulation permits a greater range of ulnar deviation. The muscle with the best biomechanical advantage to produce ulnar deviation of the wrist in pronation is the ECU. 23

Radial Deviation

Radial deviation at the wrist occurs through similar arthrokinematics as described for ulnar deviation ( Fig. 18-15). 42Radial deviation occurs primarily between the proximal and the distal rows of the carpal bones. The motion of radial deviation is limited by impact of the scaphoid onto the radial styloid and the UCL. The APL and EPB are best suited to produce radial deviation of the wrist. 23

A number of studies have examined the necessary range of motion at the wrist to perform functional activities. These studies report that at least 5 degrees of wrist flexion, 35 degrees of wrist extension, 10 degrees of radial deviation, and 15 degrees of ulnar deviation are needed to perform common personal care activities comfortably. 63, 64Less motion is required for 90 percent of personal care activities: 5 degrees of flexion, 6 degrees of extension, 7 degrees of radial deviation, and 6 degrees of ulnar deviation. 65

Wrist Movements and the Digits

The position of the wrist in flexion or extension influences the tension of the long or “extrinsic” muscles of the digits. The position of the wrist also has important repercussions on the position of the thumb and fingers. Neither the flexors nor the extensors of the fingers are long enough to allow maximal range of motion at the wrist and the fingers simultaneously. 23In fact, due to the restraining action of the long antagonistic muscles, complete flexion of the fingers is possible only if the wrist is in approximately 20 degrees of extension, which corresponds to the optimal position for hand function. 23Thus the movements of the wrist reinforce the action of the extrinsic muscles of the fingers, and are synergistic with the more powerful digital flexors. As the wrist position changes, the functional lengths of the digital flexor tendons change and the resultant forces in finger flexion vary. In order for grip to be effective and have maximal force, the wrist must be stable and positioned in slight extension and ulnar deviation. 23

Articulations of the Fingers

There are notable differences between the IP and MCP articulations of the digits and even between the articulations at the same level for each digit. 23These differences are produced by

• the shape of the articulations;
• the orientation of the articular surface;
• the synovial insertion;
• the disposition of the collateral ligaments;
• the degree of play in the volar plate.

These elements determine the degree of mobility and stability of these articulations and the orientation of the distal segments. As the thumb pulp pronates in opposition, the pulps of the fingers supinate in external rotation when the MCP joints flex, or when the index finger moves radially. These variations in orientation allow for optimal use of the finger pulps for functional tasks of the hand (see Functional Position of the Hand). 23

Thumb Movements

The first CMC joint is a saddle joint. The characteristic feature of a saddle joint is that each articular surface is concave in one diameter and convex in the other. Within the first CMC joint, the longitudinal diameter of the articular surface of the trapezium is generally concave from an anterior (palmar) to posterior (dorsal) direction, while the transverse diameter is generally convex along a medial to lateral direction. The proximal articular surface of the first metacarpal is reciprocally shaped to that of the trapezium. This articular relationship produces the following ( Fig. 18-16):

• Thumb flexion and extension occur around an anterior–posterior axis in the frontal plane that is perpendicular to the sagittal plane of finger flexion and extension. In this plane, the metacarpal surface is concave, and the trapezium surface is convex. Flexion is accompanied by a conjunct rotation of internal rotation of the metacarpal. Extension is accompanied bya conjunct rotation of external rotation of the metacarpal. A total range of 50–70 degrees is available.
• Thumb abduction and adduction occur around a medial–lateral axis in the sagittal plane that is perpendicular to the frontal plane of finger abduction and adduction. During thumb abduction and adduction, the convex metacarpal surface moves on the concave trapezium. Abduction is accompanied by a conjunct rotation of internal rotation. Adduction is accompanied bya conjunct rotation of external rotation. A total range of 40–60 degrees is available.
• Opposition of the thumb involves a wide arc motion comprising sequential anterior (palmar) abduction and flexion from the anatomic position, accompanied by internal rotation of the thumb. Retroposition of the thumb returns the thumb to its anatomic position, a motion that incorporates the elements of adduction with extension and external rotation of the metacarpal.

Normal Ulnar Inclination of the Fingers

A normal ulnar inclination of the fingers occurs at the MCP joints due to a number of factors 23:

• Asymmetry of the metacarpal heads and the collateral ligaments.
• Tendon factors: the extrinsic tendons, extensors, and flexors cross into the hand on the ulnar side of the longitudinal axis of the MCP joint.
• Muscle factors: the intrinsic muscles have a predominantly ulnar inclination and predominate over those with a radial inclination.
• The physiologic action of the thumb, which in lateral grip pushes the fingers in an ulnar direction.

The inclination is most marked in the index finger, less in the middle and little fingers, and almost nonexistent in the ring finger. The ulnar inclination is normally limited by the capsuloligamentous resistance at the MCP joints and by the action of the interosseous muscles, which act in a radial direction. 23The weakness of these stabilizing elements, particularly in rheumatoid arthritis (RA), allows the ulnar inclination to be accentuated, resulting in pathologic ulnar deviation.

Functional Position of the Hand

Grips

The grip is typically divided into following stages 67, 68:

• Opening of the hand.
• Positioning and closing of the fingers to grasp an object and adapt to the object's shape.
• Controlled approach and purposeful closing of the fingers and/or palm. The amount of force exerted is determined by the weight, surface characteristics, and fragility of the object. 69
• Maintenance and stabilization of the grip. This phase is not used in precision tasks.
• The release of the object.

Two major types of grips have been recognized: power grip and the precision or prehension grip.

Power Grip

The power grip involves the use of force to stabilize an object in the hand. The strength and power of a grip comes from a combination of

• thumb adduction,
• isometric flexion,
• an approximation of the thenar and hypothenar eminences,
• intact function of the ulnar side of the hand.

The power grips include the following:

• Hook grasp.This grasp involves all or the second and third fingers (the IP joint only for the IP and MCP joints of the fingers) and is controlled by the forearm flexors and extensors ( Fig. 18-17).
• Fist grasp.In this grasp the hand moves around a narrow object ( Fig. 18-18)
• Cylindrical grasp.In this grasp, the thumb is used and the entire hand wraps around an object ( Fig. 18-19)
• Spherical grasp.This grasp involves the hand moving around a spherical object as it moves into position ( Fig. 18-20)

Participation of the intrinsic muscles follows specific patterns in the various power grips. For example,

• the hook grip involves the fourth posterior (dorsal) interosseus, fourth lumbrical, and the ADM;
• the spherical grip involves all of the interossei (except the second), the ADM, and the fourth lumbrical. 70, 71

Precision Grip

In the precision grip, the muscles primarily function to provide exact control of finger and thumb position, so the position of the handled object can be changed either in space or about its own axis. 67, 71Due to the higher levels of sensory input required during these tasks, the areas with the most sensory receptors are used. A number of precision grips are recognized 23, 62:

• Pulp-to-pulp pinch,in which the pad of the thumb is opposed to the pad of one or more fingers ( Fig. 18-21).
• Lateral prehension,where the anterior (palmar) aspect of the thumb presses against the radial aspect of the first phalanx of the index finger ( Fig. 18-22).
• Tip prehension,in which the extreme tip of the thumb pad is opposed to the tip of the index or middle finger.
• Three-fingered pinch(thumb, index finger, and middle finger), as in sprinkling herbs, and multi-fingered pinch ( Fig. 18-23).
• Five-fingered pinch,as in picking up a face towel ( Fig. 18-24).

The radial side of the hand and the MCP joints are involved more in the precision or prehensile types of grips. 23, 62

Different grip patterns are used regularly during daily functional activities ( Table 18-3). 1, 72

Elucidating the cause of forearm, wrist, and hand pain can be challenging. The examination must include all regions that may contribute to the symptoms of forearm, wrist, and hand pain or numbness. This requires a sound knowledge of differential diagnosis and often incorporates an examination of the entire upper kinetic chain, including the cervical and thoracic spine.

The common pathologies for the forearm, wrist, and hand and their interventions are detailed after the “Examination” section. An understanding of both is obviously necessary. As mention of the various pathologies occurs with reference to the tests and measures and vice versa, the reader is encouraged to switch between the two.

History

The assessment of the forearm, wrist, and hand begins by recording a detailed history to help focus the examination. All relevant information must be gathered about the site, nature, behavior, and onset of the current symptoms. This should include information about the patient's age, hand dominance, avocational activities, and occupation.

In addition to those questions covered in Chapter 4, the following questions should be asked:

• When did the symptoms occur?The date of injury is particularly important, especially as simple traumatic arthritis of the wrist does not last more than a few days if the wrist is rested.
• Was there a mechanism of injury?If the problem is trauma related, the clinician should ascertain the following:
  • The forces applied. For example, a rotational force applied to the wrist region may lead to a fracture of the radius and dislocation of the distal end of the ulna (Galeazzi fracture).
  • Where and when the injury occurred.
  • The position of the wrist and hand at the time of the trauma. For example, a fall on the outstretched hand (FOOSH) injury can lead to a lunate dislocation, Colles fracture, or scaphoid fracture.
  • Whether the environmental conditions were clean or dirty (if a wound is present).
  • Whether there was an accompanying “pop” or “click.”
  • Whether swelling occurred.

If the problem is nontrauma related, the onset of pain or sensory change, swelling, or contracture should be ascertained.

• Are there any local areas of tenderness?Localized tenderness may indicate a carpal fracture, particularly of the scaphoid. Scaphoid fractures are associated with a load applied to the radial side of the palm when the wrist is in extreme extension, 77and can be ongoing sources of pain and dysfunction (refer to “Intervention Strategies”). Pain along the radial aspect of the wrist and forearm is a common symptom for several pathoanatomical diagnoses, including de Quervain disease, intersection syndrome, intercarpal instabilities, scaphoid fracture, superficial radial neuritis, C6 cervical radiculitis/radiculopathy, and arthrosis of the first CMC, intercarpal, or radiocarpal joints. 78
• How does the patient rate his or her pain?The patient's perception of their pain can be measured using a visual analog scale.
• What is the behavior of the symptoms?The clinician should note the sequence of symptoms, the level of functional impairment, the progression of symptoms, the time of day the symptoms are worse, and whether the symptoms appear to be posture related or work related. Knowledge of the past behavior of previous wrist, hand, and finger disorders and their interventions can help in assessing the nature and prognosis of the patient's current problem.
• Which hand is the dominant hand (DH) of the patient?Dysfunction of the DH can be very disabling, so inquiries concerning the functional demands of the patient must be made.

Systems Review

A complete review of the medical history and general health of the patient should be included along with a review of systems, and the presence of other orthopaedic, neurologic, or cardiopulmonary conditions. An upper quarter scanning examination is performed to provide an overview of the upper extremity, the direction for a more detailed examination, and to rule out referral from the cervical, thoracic, shoulder girdle, and elbow joints.

The clinician should be able to determine the suitability of the patient for physical therapy. All inflammatory conditions, whether infectious or not, are accompanied by diffuse pain or tenderness with movement. RA often affects this region with more severity and frequency than elsewhere. Therefore questions concerning other joint involvement and general debility must be asked. The presence of CTS, which is usually felt more at night, may also indicate RA.

If the clinician is concerned with any signs or symptoms of a visceral, vascular, neurogenic, psychogenic, spondylogenic, or systemic disorder that is out of the scope of physical therapy (see Chapter 5), the patient should be referred back to their physician.

Tests and Measures

Observation

The physical examination should begin with a general observation of the patient's posture—especially the cervical spine, the thoracic spine, and the position of the hand in relation to the body. For example, is the arm held against the chest in a protective manner, does the arm swing during the gait pattern, or does it just hang loosely? The patient's hands can be highly informative ( Table 18-4). Although very subtle, the DH tends to be larger than the nondominant hand. The posture and alignment of the involved wrist and hand are examined. Wrist angulation into ulnar deviation increases shearing in the first posterior (dorsal) compartment. This angulation can predispose the patient to de Quervain syndrome (see “Intervention Strategies”). 79A prominence of the distal ulna may indicate DRUJ instability. 80The posture of the hand should be analyzed. The clinician should observe how the patient appears to relate to the involved hand and if or how the patient attempts to use the hand. 11The contour of the anterior (palmar) surface, including the arches, should be examined. If a finger is involved, its attitude should be observed. Digital deformities are the hallmark of RA. 81

A visual inspection of the involved wrist and hand is made and is compared with the uninvolved side. The clinician inspects for lacerations, surgical scars, masses, swelling, or erythema.

• Scars should be examined for degree of adherence, degree of maturation, hypertrophy (excess collagen within the boundary of the wound), and keloid (excess collagen that no longer conforms to wound boundaries).
• The location and type of edema should be noted. Edema, the accumulation of fluid in the intercellular spaces, is a common consequence of surgery or injury to the hand. A determination is made as to whether the swelling is generalized or localized, hard or soft. Anterior effusion over the flexor tendons at the wrist may indicate rheumatoid tenovaginitis. Swelling that persists more than a few days following trauma probably suggests a carpal fracture. Localized swelling accompanied by redness and tenderness may indicate an infection. Measuring edema is an important part of the physical examination of individuals with conditions affecting the wrist and hand. Volumetry, a clinical application of Archimedes principle of water displacement as a measure of volume, is considered the gold standard for measuring hand size. 82This method involves lowering the limb into a water-filled Plexiglass or metal tank (the volumeter) and measuring the amount of water displaced. 83The reliability and validity of volumetric measurements is well established. 82However, this method is time consuming and requires specialized equipment. An alternative method of measuring is the figure-of-eight method. Compared to volumetric method, the figure-of-eight method is more practical for clinical use as the procedure takes less time to perform and requires equipment that is less expensive and is readily available in most clinical settings. 82The correct application of the tape is described in Table 18-5. Leard and colleagues 82reported the figure-of-eight method to be a reliable and valid measure of hand size in individuals with conditions affecting the hand.

The swan-neck deformity is one of the most frequently encountered deformities of the fingers (see “Intervention Strategies”). 81When it occurs at the thumb it is referred to as a zigzag deformity. Any other finger deformities such as mallet finger and boutonniere (see “Rheumatoid Arthritis”) are noted ( Table 18-6). Other hand deformities include the following:

• Ulnar drift.The classic deformity of ulnar shift and ulnar deviation is associated with RA (although it can occur in other conditions) and the MCP joints. The deformity occurs due to the cumulative effects of various factors. Initially, the MCP joint capsule and ligamentous structures are stretched by the proliferation of the synovium, which loosens the collateral ligaments and decreases joint stability (see “Rheumatoid Arthritis”).
• Extensor plus.This deformity results from either shortening of the extensor communis tendon or adherence of the tendon to the first part of the proximal phalanx at the extensor hood. It results in the inability to flex the PIP and MCP joints simultaneously, although each joint can be flexed normally individually.
• Myelopathy hand.This deformity, which is characterized by a loss of power in abduction and extension of the ulnar fingers, is caused by cervical spinal cord pathology in conjunction with cervical spondylosis. 86Confirmation of this finding is made when lower motor neuron findings are seen at the level of the lesion while upper motor neuron findings are seen below the level of the lesion.

The nails should be inspected to see if they are healthy and pink ( Table 18-7). Local trauma to the nails seldom involves more than one or two digits. The nails should be checked for hangnail infection or whether they appear ridged, which could indicate a RA dysfunction. Clubbed nails are an indication of hypertrophy of underlying structures. The presence of a paronychia or a pale paronychia should prompt the clinician to probe the axilla and neck lymph nodes for tenderness and swelling. Beau lines are transverse furrows that begin at the lunula and progress distally as the nail grows. They result from a temporary arrest of growth of the nail matrix occasioned by trauma or systemic stress. 87With the knowledge that nails grow about 0.1 mm/day, by measuring the distance between the Beau lines and the cuticle, one may be able to approximately determine the date of the stress. For example, if the distance is 5 mm, the stress event occurred approximately 50 days before. Spoon nails (koilonychias) may occur in a form of iron deficiency anemia (Plummer–Vinson syndrome), coronary disease, and with the use of strong detergents. 87Clubbing of the nails, characterized by a bulbous enlargement of the distal portion of the digits, may occur in association with cardiovascular disease, subacute endocarditis, advanced cor pulmonale, and pulmonary disease. 87

Finger color should be observed. Fingers that are white in appearance might indicate Raynaud disease. Blotchy or red fingers might indicate liver disease. Blue fingers may indicate a circulatory problem.

Intrinsic muscle fibrosis is characterized by stiffness at the IP joints. On flexion of the MCP joint, extension of the fingers becomes tight and flexion is restricted. On extension of the MCP joint, flexion of the IP joints is possible.

• Adhesions proximal to the MCP joint allow lumbrical action (i.e., MCP flexion and PIP and DIP joint extension).
• Adhesions distal to the MCP joints result in the ability to extend the MCP and flex the PIP and DIP joints, but there is no extension possible in the fingers.

Palpation

Palpation of the wrist and hand is an integral component of the physical examination. Palpation may be performed separately or with the range-of-motion tests. Fortunately, most of the structures are superficial ( Fig. 18-25), so a sound knowledge of surface anatomy is essential. The findings from palpation can often be confirmed using a specific special test (see “Special Tests”). Palpation of the following muscles, tendon, insertions, ligaments, capsules, and bones should occur as indicated and be compared with the uninvolved side for tenderness and/or swelling.

Trapezium

The trapezium is located immediately proximal to the base of the first metacarpal bone, just distal to the scaphoid. The tubercle of the trapezium lies anteriorly at the base of the thenar eminence. It can be made more prominent by opposing the thumb to the little finger and ulnarly deviating the wrist. Tenderness over this carpal may indicate scaphotrapezial arthritis secondary to scaphoid instability. 13

Thumb CMC Joint

To examine the thumb CMC joint, the clinician palpates carefully along the shaft of the thumb metacarpal down to its proximal flare. Just proximal to this flare is a small depression where the CMC joint is located. By applying direct radial and ulnar stresses to the joint, the clinician can determine the overall stability of the joint as compared to the other thumb. Tenderness here is usually indicative of degenerative arthritis.

EPB, APL, and FCR Tendons

The EPB and APL tendons make up the first extensor compartment on the dorsum of the wrist and together form the radial border of the anatomic snuffbox. The APL is the first prominent tendon medially. Prominence of these tendons can be enhanced by extending and radially abducting the thumb. Tenderness over these tendons may indicate de Quervain tenosynovitis. Just medial to the APL is the radial artery with the FCR tendon, which inserts on the second metacarpal, situated medially.

Flexor Retinaculum

The flexor retinaculum, which can be palpated just medial to the FCR, transforms the carpal arch into the carpal tunnel. It is attached medially to the pisiform and hook of the hamate and laterally to the tubercle of the scaphoid and tubercle of the trapezium. Its proximal edge is at the distal crease of the wrist. The retinaculum can be the location for a retinacular cyst which, because of its firmness, is frequently mistaken for a bony spur.

Hamate

The hook of the hamate is palpated just distal and radial (in the direction of the thumb web space) to the pisiform on the anterior (palmar) aspect. Locating the hamate can be made easier if the clinician places the middle of the distal phalanx of the thumb on the pisiform, with the thumb pointing between the web space between the index and long finger. The clinician flexes the IP joint of the thumb and presses into the hypothenar eminence to feel the firm hook. The hook of the hamate is concave laterally, and the ulnar nerve's superficial division, which is just lateral and proximal to the hook, can be rolled on it. Tenderness over this carpal is common, and so the clinician should compare findings with the other side. Severe tenderness could indicate a fracture of the hamate, especially if associated with a FOOSH injury or a missed hit swing of a racket or bat. 88The FCU tendon surrounds the hamate as it inserts on the pisiform.

Pisiform

The pisiform is located on the flexor aspect of the palm, on top of the triquetrum, at the distal crease. Tenderness of this structure may indicate pisotriquetral arthritis or inflammation of the FCU tendon. 4The pisiform may be fractured from a direct fall or blow to the hypothenar aspect of the hand.

Triangular Fibrocartilage Complex

The TFCC is located distal to the ulnar styloid and proximal to the pisiform. Tenderness over this structure indicates an injury to the TFCC. 4

Ulnar Head and Styloid Process

The ulnar head forms a rounded prominence on the ulnar side of the wrist, which is easily palpated on the posterior aspect of the hand with the forearm in pronation. 80The ulnar styloid process is ulnar and distal to the head of the ulna. It is best located with the forearm in supination.

Radial Styloid Process

The radial styloid process is larger and rounder than the ulnar styloid process. It is best palpated at the most proximal point of the anatomic snuffbox (see below), during radial abduction of the thumb. With simultaneous radial deviation of the wrist, this prominence becomes visible. Tenderness over the styloid, especially with radial deviation, may indicate contusion, fracture, or radioscaphoid arthritis. 89

Lister's Tubercle

This is a small bony prominence on the posterior (dorsal) and distal end of radius. It is found by sliding a finger proximally from a point between the index and the middle fingers. Just distal to Lister's tubercle is the joint line of the scaphoid and radius. The ECRL and ECRB tendons travel radial to Lister's tubercle and insert on the base of the second and third metacarpals. The extensor digitorum communis (EDC) tendon travels ulnarly to Lister's tubercle. Radial to Lister's tubercle and proceeding further radially are the tendons of the ECRB, ECRL, EPB, and APL.

Scaphoid

The scaphoid is palpated just distal to the radial styloid in the anatomic snuffbox. The neck of the scaphoid is located on the floor of the anatomic snuffbox. Palpation can be made easier by positioning the wrist in ulnar deviation. The scaphoid may be grasped and moved passively by firm pressure between an opposed index finger and thumb applied to the anterior (palmar) surface and anatomic snuffbox simultaneously. In most individuals, the scaphoid is mildly tender to palpation, but those with a scaphoid fracture, nonunion, or scaphoid instability have severe discomfort (see “Special Tests”). 2, 90

Lunate

The lunate is located just distal and ulnar to Lister's tubercle with the wrist flexed and is immediately proximal to, and in line with, the capitate. The mobile lunate can be felt to glide posteriorly (dorsally) with extension. It is the most commonly dislocated carpal and the scapholunate articulation is the most common area for carpal instability. Scapholunate synovitis (posterior (dorsal) wrist syndrome) or a scapholunate ligament injury presents with tenderness or fullness in this region. 2Tenderness specific to the lunate can indicate Kienböck disease or osteonecrosis of the lunate. 91, 92

Capitate

The capitate is localized by palpating proximally over the posterior (dorsal) aspect of the third metacarpal until a small depression is felt. While palpating in this depression, as the wrist is flexed, the clinician should feel the capitate, the central bone of the carpals, move posteriorly (dorsally). Tenderness in this depression may indicate scapholunate or lunotriquetral instability, or capitolunate degenerative joint disease.

Second and Third Metacarpals

The base of the second and third metacarpals and the CMC joints are localized by palpating proximally along the posterior (dorsal) surfaces of the index and long metacarpals to their respective bases. 80A bony prominence found at the base of the second or third metacarpal may be a carpal boss, a variation found in some individuals due to hypertrophic changes of traumatic origin. 80

Triquetrum

The triquetrum is located by radially deviating the wrist while palpating just distal to the ulnar styloid. With ulnar deviation, the triquetrum articulates with the TFCC, which functions as a buffer between the styloid and the triquetrum. Tenderness and swelling in the triquetral hamate region are often present with midcarpal instability, which occurs when the anterior (palmar) triquetral–hamate–capitate ligament is ruptured or sprained. 93

Tunnel of Guyon

The tunnel of Guyon is located in the space between the hamate and the pisiform. 6

Carpal Tunnel

The distal wrist crease marks the proximal edge of the carpal tunnel. The boundaries of the carpal tunnel are as follows:

• Radial:scaphoid tubercle and trapezium.
• Ulnar:pisiform and hamate.
• Posterior (dorsal):the carpal bones.
• Anterior (palmar):transverse carpal ligament.
• Proximal:antebrachial fascia.
• Distal:distal edge of the retinaculum at the CMC level, FCR, and scaphoid tubercle.

PIP Joints

Palpation of the PIP joint offers important information. Palpation of the joint over four planes (posterior (dorsal), anterior (palmar), medial, and lateral) allows assessment of point tenderness over ligamentous origins and insertions that is highly suggestive of underlying soft-tissue disruption. 22In cases in which the joint is grossly swollen and tender, this part of the examination may provide more accurate information several days after the injury. 22

Active Range of Motion (AROM), Then Passive Range or Motion with Overpressure

The gross motions of wrist, hand, finger, and thumb flexion, extension, and radial and ulnar deviations are tested ( Fig. 18-14), first actively and then passively ( Table 18-8). Horger 94conducted a reliability study to determine (a) the intrarater and interrater reliability of goniometric measurement of active and passive wrist motions under clinical conditions and (b) the effect of a therapist's specialization on the reliability of measurement. The results indicated that measurement of wrist motion by individual therapists is highly reliable and that intrarater reliability is higher than interrater reliability for all active and passive motions. 94Interrater reliability was generally higher among specialized therapists for reasons not immediately apparent from this study. 94With the exception of pain, identified sources of error were found to have surprisingly little effect on the reliability of measurement. 94

Any loss of motion compared with the contralateral, asymptomatic wrist and hand should be noted.

During measurement of motion, one must be aware that finger joint positions may affect wrist joint ranges (and vice versa) due to the constant length of the extrinsic tendons that cross multiple joints. Forearm pronation and supination can have a similar impact on joint ranges. For example,

• greater wrist flexion occurs with finger extension than with finger flexion because the ED tendons are not stretched maximally;
• less deviation range of motion is available when the wrist is fully extended or flexed.

Thus during the examination, the clinician should maintain all joints in a consistent position (usually neutral), except the one being measured. In addition, the clinician should identify wrist and finger joint position when measuring the strength of related muscles.

Somatic dysfunction of the wrist permits motion toward the dysfunction; motion away from the dysfunction will be restricted.

Fanning and folding of the hand is performed by palpating the anterior (palmar) surface of the pisiform, scaphoid, hamate, and trapezium with the index and middle fingers and the posterior (dorsal) surface of the capitate with the thumbs as the hand is alternately fanned and folded. During these motions, the clinician should note the quantity and quality of the conjunct rotations. An absence of the conjunct rotations may indicate an intercarpal dysfunction.

The uninvolved joint should always be examined first. This allows for a determination of the normal function, allays the patient's anxiety, and allows for a true comparison of function. 4During palpation, the clinician should be on the alert for any thickening over tendons, tenderness, or areas of fluctuation. 4During active and passive testing, the presence of crepitus must be determined. The presence of crepitus with motion may indicate a tendon sheath synovitis or vaginitis.

Pronation and Supination

Pronation and supination of the wrist on the forearm will provisionally test the TFCC and the proximal and DRUJs. Full forced pronation–supination without evoking pain eliminates the DRUJ and the TFCC as potential sources of the patient's complaints. 2Normal ranges for pronation and supination are approximately 85–90 degrees with approximately 75 degrees occurring in the forearm articulations and the remaining 15 degrees the result of wrist action. The normal end feel for these motions is tissue stretch, although in cachexic patients, the end feel of pronation may be bone to bone.

Radial and Ulnar Deviation

Normal radial deviation is approximately 15 degrees, while normal ulnar deviation is between 30 and 45 degrees. The normal end feel for these motions is bone to bone.

Wrist Flexion

The normal range of motion of wrist flexion is 80 to 90 degrees with an end feel of tissue stretch. According to Watson, 2any loss of passive wrist flexion is a sign of underlying organic carpal pathology. To determine whether painful wrist flexion is due to a problem between the scaphoid and radius, or the scaphoid and the trapezium and trapezoid, the wrist is placed in full flexion, with the posterior (dorsal) surface of the hand resting on the treatment table. The clinician pushes on the scaphoid and second metacarpal in a posterior (dorsal) direction. An increase in pain with this maneuver may indicate a problem at the scaphoid–radius articulation.

If there is no increase in pain with this maneuver, the wrist is placed in a neutral position with regard to flexion and extension. The clinician stabilizes the trapezium and trapezoid and pushes the scaphoid posteriorly (dorsally). An increase in pain with this maneuver may indicate a problem at the trapezium/trapezoid–scaphoid articulation.

To determine whether the painful wrist flexion is due to a problem between the capitate and the lunate or the lunate and the radius, the wrist is placed in full flexion. The clinician pushes the lunate in an anterior (palmar) direction. An increase in pain with this maneuver may indicate a problem at the capitate–lunate articulation. If the pain is not increased with this maneuver, the wrist is placed in full flexion and the clinician pushes the lunate in a posterior (dorsal) direction. An increase in pain with this maneuver may indicate a problem at the lunate–radius articulation. A decrease in pain with this maneuver may indicate a problem at the capitate–lunate articulation.

Wrist Extension

The normal range of motion for wrist extension is 70–90 degrees with an end feel of the tissue stretch. According to Watson, 2any loss of passive wrist extension is a sign of underlying organic carpal pathology. To determine whether the pain with wrist extension is due to a problem between the scaphoid and the radius or the scaphoid and the trapezium/trapezoid, the wrist is positioned in full extension with the palm positioned on the table. The clinician pushes on the radius in an anterior (palmar) direction, thus increasing the amount of wrist extension. An increase in pain with this maneuver may indicate a problem at the scaphoid–radius articulation. If this maneuver does not increase pain, the wrist is positioned as before. The clinician now pushes on the radius in a posterior (dorsal) direction. A decrease in pain with this maneuver may indicate a problem at the scaphoid–radius articulation. An increase in pain with this maneuver may indicate a problem at the scaphoid and trapezium/trapezoid articulation.

This is confirmed by placing the wrist as before in full extension and pushing on the scaphoid in a posterior (dorsal) direction. A decrease in pain with this maneuver indicates a problem between the scaphoid and the radius, whereas an increase in pain with this maneuver indicates the problem is between the scaphoid and the trapezium/trapezoid.

The clinician fixes the scaphoid and pushes the trapezium/trapezoid in an anterior (palmar) direction. A decrease in pain with this maneuver may indicate a problem at the scaphoid–trapezium/trapezoid articulation. If the pain remains unchanged with this maneuver, the problem is likely to be at the scaphoid–radius articulation. To confirm this hypothesis, the scaphoid can be pushed in an anterior (palmar) direction while the wrist is maintained in the position of full extension. This should increase the pain if the hypothesis is correct.

To determine whether pain is due to a problem between the capitate and lunate or the lunate and radius, the wrist is positioned in full extension, with the palm of the hand on the table. The clinician pushes on the radius in an anterior (palmar) direction. An increase in pain with this maneuver indicates a problem at the capitate–lunate articulation.

If the pain is increased by pushing the lunate and capitate in an anterior (palmar) direction, this may indicate a problem at the lunate–radius articulation.

If fixing the lunate and pushing the capitate in an anterior (palmar) direction (a relative motion of the lunate posteriorly [dorsally] in relation to the capitate) increases the pain, the problem is likely at the capitate–lunate articulation.

Thumb

The following motions are tested in varying degrees of wrist flexion and extension:

• CMC abduction, adduction, flexion, extension, and opposition ( Fig. 18-16). During opposition, the clinician should observe for the conjunct rotation component of the motion.
• MCP and IP flexion and extension.

Fingers

It should never be assumed that lack of full active flexion or extension of the PIP is merely secondary to joint pain or fusion, because closed rupture of the middle slip of the extensor hood is easily missed until the appearance of a boutonniere deformity. 22During flexion of the fingers, the overall area of the fingers should converge to a point on the wrist corresponding to the radial pulse. This can only occur if the index finger flexes in a sagittal plane and all the others in an increasingly oblique plane. A skyline view of the knuckles is made. In full flexion, a posteriorly (dorsally) subluxed capitate may be seen as a local swelling on the back and middle of the flexed wrist.

Total active motion of the fingers is the sum of all angles formed by the MCP, PIP, and DIP joints in simultaneous maximum active flexion, minus the total extension deficit at the MCP, PIP, and DIP joints (including hyperextension at the IP joints) in maximum active extension.

A normal value for total AROM in the absence of a normal contralateral digit for comparison is 260 degrees, based on 85 degrees of MCP flexion, 110 degrees of PIP motion, and 65 degrees of DIP motion. 95

A comparison of active and passive motion indicates the efficiency of flexor and extensor excursion and/or degree of muscle strength within the available passive range of motion (PROM). 95Instances of greater passive than active motion may indicate a limited tendon glide due to adherence of the tendon to surrounding structures or relative lengthening of the tendon due to injury or surgery, weakness, or pain. 95

Due to the multitude of joints and multiarticular muscles found in the hand, the clinician may need to differentiate between various structures in order to determine the cause of a motion restriction (see “Special Tests”). 95For example, adherence of the extrinsic flexors is tested by passively maintaining the fingers and thumb in full extension while passively extending the wrist. In the presence of flexor tightness, the increasing flexor tension that develops as the wrist is passively extended will pull the fingers into flexion. Adherence of the extensor tendons is simply a reverse process. The digits are passively maintained in full flexion while the wrist is passively flexed. If tension pulling the fingers into extension is detected by the clinician's hand as the wrist is brought into flexion, extrinsic extensor tightness exists.

Strength Testing

Isometric tests are carried out in the extreme range, and if positive, in the neutral range. These isometric tests must include the interossei and lumbricals. The straight plane motions of wrist flexion, extension, and ulnar and radial deviation are tested initially. Pain with any of these tests requires a more thorough examination of the individual muscles. The clinician should be able to extrapolate hand placements for these tests by noting the anatomy of these muscles from the figures. The muscles controlling wrist extension (see Chapter 17), wrist flexion (see Chapter 17), radial deviation, and ulnar deviation are tested first.

Wrist

FCR/FCU

During the testing of these muscles, substitution by the finger flexors should be avoided by not allowing the patient to make a fist. The clinician applies the resistive force into extension and radial deviation for the FCU, and extension and ulnar deviation for the FCR.

ECRL/ECRB

Any action of the EDC should be ruled out by having the patient make a fist while extending the wrist. The clinician applies the resistive force on the dorsum of the second and third metacarpals, with the force directed into flexion and ulnar deviation.

Extensor Carpi Ulnaris

The ECU is tested by having the patient make a fist in wrist extension, while the clinician applies resistance on the ulnar dorsum of hand, with the force directed into flexion and radial deviation.

Thumb

APL/APB

The forearm is positioned midway between pronation and supination, or in maximal supination. The MCP and IP joints are positioned in flexion. The muscles are tested with anterior (palmar) abduction of the thumb in the frontal plane for the longus and in the sagittal plane for the brevis.

Opponens Pollicis

The forearm is positioned in supination and the posterior (dorsal) aspect of the hand rests on the table. The patient is asked to touch the finger pads of the thumb and little finger together. Using one hand, the clinician stabilizes the first and fifth metacarpals and the palm of the hand. With the other hand, the clinician applies a force to the distal end of the first metacarpal in the opposite direction of opposition (retroposition).

FPL/FPB

The forearm is positioned in supination and supported by the table, and the hand is positioned so that the posterior (dorsal) aspect rests on the table. The thumb is adducted. The longus is tested by resistance applied to the distal phalanx, whereas both heads of the brevis are tested by resistance applied to the proximal phalanx.

Adductor Pollicis

This muscle is tested by having the patient hold a piece of paper between the thumb and radial aspect of the index finger's proximal phalanx while the clinician attempts to remove it. If weak or nonfunctioning, the IP joint of the thumb flexes during this maneuver due to substitution by the FDP (Froment sign).

Extensor Pollicis Longus/EPB

Both of these muscles can be tested with the patient's hand flat on the table, palm down, and asking the patient to lift only the thumb off the table. To test each individually, resistance is applied to the posterior (dorsal) aspect of the distal phalanx for the EPL while stabilizing the proximal phalanx and metacarpal and to the posterior (dorsal) aspect of the proximal phalanx for the EPB while stabilizing the first metacarpal.

Intrinsics

Lumbricals

The four lumbricals are tested by applying resistance to the posterior (dorsal) surface of the middle and distal phalanges, while stabilizing under the proximal phalanx of the finger being tested. The anterior (palmar) and posterior (dorsal) interossei act with the lumbricals to achieve MCP flexion coupled with PIP and DIP extension.

Anterior (Palmar) Interossei

The three anterior (palmar) interossei adduct the second, fourth, and fifth fingers to midline.Resistance is applied by the clinician to the radial aspect of the distal end of the proximal phalanx of the second, fourth, and fifth fingers, after first stabilizing the hand and fingers not being tested.

Posterior (Dorsal) Interossei/ADM

The four posterior (dorsal) interossei abduct the second, third, and fourth fingers from midline. The ADM abducts the fifth finger from midline.

The intrinsic muscles are tested in the frontal plane to avoid substitution by the extrinsic flexors and extensors. Resistance is applied by the clinician to the ulnar aspect of the distal end of the proximal phalanx of each of the four fingers, after first stabilizing the hand and fingers not being tested.

Fingers

Flexor Digitorum Profundus

This muscle is tested with DIP flexion of each digit, while the MCP and PIP are stabilized in extension and wrist neutral. Due to the variability of nerve innervation for this muscle group, each of the fingers can be tested to determine whether a peripheral nerve lesion is present. The index finger is served by the anterior interosseous nerve, the middle finger by the main branch of the median nerve, and the ring and little finger by the ulnar nerve.

Flexor Digitorum Superficialis

There is normally one muscle tendon unit for each finger; however, an absent flexor digitorum superficialis to the little finger is common. The clinician should only allow the finger to be tested to flex by firmly blocking all joints of the nontested fingers, with the wrist in neutral.

ED/Extensor Indicis Proprius

There is only one muscle belly for this four-tendon unit. These three muscles are the sole MCP joint extensors. With the wrist in neutral, the strength is tested with the metacarpals in extension and the PIP/DIP flexed. The extensor indicis proprius can be isolated by positioning the index finger and hand in the “number one” position—the index finger in extension with other fingers clenched in a fist. The EDM muscle is tested with resistance of little finger extension with the other fingers maintained in a fist.

To isolate intrinsic muscle function, the patient is asked to actively extend the MCP joint and then to attempt to actively extend the PIP joint. Because the ED, EI, and EDM tendons are “anchored” at the MCP joint by active extension, only the intrinsic muscles can now extend the PIP joint. 17To test the terminal extensor tendon function, the clinician stabilizes the middle phalanx and asks the patient to extend the DIP joint. 11

Flexor Digiti Minimi

The forearm is positioned in supination and the posterior (dorsal) aspect of the hand rests on the table. The clinician stabilizes the fifth metacarpal and the palm with one hand, and then applies resistance to the anterior (palmar) surface of the proximal phalanx of the fifth digit with the other hand.

Opponens Digiti Minimi

The forearm is positioned in supination and the posterior (dorsal) aspect of the hand rests on the table. The patient is asked to touch the finger pads of the thumb and little finger together. Using one hand, the clinician stabilizes the first and fifth metacarpals and palm of the hand. With the other hand, the clinician applies a force to the distal end of the fifth metacarpal in the opposite direction of opposition (retroposition).

Grip Strength

A loss of grip or pinch is a measurable factor used in the determination of permanent disability by compensation boards in some states. 96

The assessment of grip strength ( Fig. 18-26) and pinch strength ( Fig. 18-27) is used to assess function of the hand, using a dynamometer. The average values for grip strength are given in Table 18-9. Normal grip strength, which provides statistical analysis of males versus females. 97The mean value for the nondominant hand can be calculated from the values of the DH and the ratio.

A number of protocols using a sealed hydraulic dynamometer, such as the Jamar dynamometer ( Fig. 18-26) (Asimow Engineering Co., Santa Monica, CA), have been shown to be accurate, reliable, and valid in measuring grip strength. 98, 99These dynamometers register force in pounds per square inch, or kilopound per square centimeter, and have adjustable handles to accommodate any sized hand, or any hand that may have a limitation of finger joint motion. 100

Studies have demonstrated that the second handle setting of the Jamar dynamometer allows for the maximum grip strength from the patient. 100, 101The widest grip uses mostly the profundus muscles. At the narrowest grip, the profundus and superficialis muscle excursion are fully used, preventing much in the way of their contribution to the overall grip strength. 96, 100

Unfortunately, these tests are not purely objective, as they rely on the sincerity of effort from the patient. 102Thus a number of tests have been introduced in an attempt to aid in the detection of insincerity of effort:

• The five-position grip strength test.96This test uses the Jamar dynamometer and uses the five handle settings to measure grip strength at the five different grip widths. In normal and motivated patients, maximum grip strength occurs at the second or third grip width. The maximum grip strength, recorded at the first or fifth width setting, is supposed to be indicative of an insincerity of effort, although the reliability of the five-position grip strength test has been questioned. 101, 103
• The rapid exchange grip test, rapid simultaneous grip strength tests.The first test was developed by Lister. 104Both of these tests use the Jamar dynamometer and compare the maximum grip strength during a five-position static grip strength test, with the maximum grip strength recorded when gripping the dynamometer repeatedly at a fast rate (80 times per minute). 105, 106In normal and motivated patients the static measure of grip strength of grip strength should be approximately 15 percent greater than the dynamic measure, while in patients demonstrating insincerity of effort, the dynamic measure is equal to or greater than the initial static measure. 106The rapid exchange and the rapid simultaneous grip strength tests are time consuming and frequently performed erroneously in the clinical setting. 102
• The rapid repeat test.The patient is seated with their arm by their side, the elbow in 90 degrees of flexion, and the forearm and wrist in neutral. The dynamometer, set at the second handle setting, is supported by the clinician and the patient alternately grips with both right and left hands on ten occasions, or until the patient has to stop due to fatigue or discomfort. This test has been found to be an unreliable discriminator of true and faked hand weakness. 102

It is probably wise to combine the results of different grip strength tests before making any decisions. 107

Functional Assessment

The hand serves many important functions that allow us to interact with others and the environment. In addition to providing a wealth of sensory information, the hand functions to grasp objects.

Hand functions have been further categorized by adding the terms graspand prehension. These terms are used to describe functions of power or precision. 20, 21

The functional positionof the wrist is the position in which optimal function is likely to occur. 62, 108This position involves wrist extension of between 20 and 35 degrees, ulnar deviation of 10 to 15 degrees, slight flexion of all of the finger joints, midrange thumb opposition, and slight flexion of the thumb MCP and IP joints. 62In this position, which minimizes the restraining action of the long extensor tendons, the pulps of the index finger and thumb are in contact.

A number of motions can be used to quickly assess hand function, including the following:

1. Opposition of the thumb and little finger.

2. Padto pad mobility of the thumb and other fingers. The majority of the functional activities of the hand require at least 5 cm of opening of the fingers and thumb. 109

3. The ability to make three different fists:

•     a. The hook fist (placing fingertips onto MCP joints).
•     b. Standard fist.
•     c. Straight fist (placing fingertips on the thenar and hypothenar eminences). The ability to flex the fingers to within 1–2 cm of the distal anterior (palmar) crease is an indication of functional range of motion for many hand activities. 109

The functional range of motionfor the hand is the range in which the hand can perform most of its grip and other functional activities ( Table 18-10).

The percentage losses of digital function are as follows: thumb, 40–50%; index finger, 20%; long finger, 20%; ring finger, 10%; little finger, 5%. Loss of the hand is 90% of the upper extremity and 54% of the whole person.

Function of the digits is related to nerve distribution. Flexion and sensation of the radial digits, important in precision grips, are controlled mainly by the median nerve, whereas flexion and sensation of the ulnar digits, important to the power grip, are controlled by the ulnar nerve. The muscles of the thumb, used in all forms of gripping, are controlled by both the median and the ulnar nerves. The release of a grip or opening of the hand is controlled by the radial nerve. A loss of the relationship between the thumb and the index finger results in an inability to perform fine motor skills that involve pulp-to-pulp pinch, as well as functions that require power.

Hand Disability Index 84

The patient is asked to rate the following seven questions on a scale of zero to three, with three being the most difficult.

• Unable to perform task = 0
• Able to complete task partially = 1
• Able to complete task but with difficulty = 2
• Able to perform task normally = 3

Are you able to do the following:

1. Dress yourself, including tying shoelaces and doing buttons?

2. Cut your meat?

3. Lift a full cup or glass to your mouth?

4. Prepare your own meal?

5. Open car doors?

6. Open jars that have previously been opened?

7. Turn taps on and off?

A variety of evaluation tools have been devised for the hand, and they can be categorized into assessments of the neurovascular system, range of motion, sensibility, and function ( Table 18-11). 109

Dexterity tests include the following:

Minnesota Rate of Manipulation Test

This test, which primarily measures gross coordination and dexterity, consists of following five functions:

1. Placing

2. Turning

3. Displacing

4. One-hand turning and placing

5. Two-hand turning and placing

The activities are timed and compared with the time taken by the other hand and then compared with normal values. 109, 110