The hip joint is a ball-and-socket joint composed of the head of the femur and the acetabulum. This articulation has many palpable bony landmarks. The proximal femur consists of a femoral head and neck as well as a greater and lesser trochanter (Fig. 18–1). The anterosuperior iliac spine and the greater trochanter are easily palpated laterally, and the pubic symphysis lies medially. The hip joint is capable of a very wide range of motion.
The neck-shaft angle should be evaluated in all suspected fractures. Normal angle is 120 to 130 degrees.
The joint is enclosed in a capsule that has attachments to the rim of the acetabulum and the femoral neck. Three ligaments are formed by capsular thickenings: the iliofemoral ligament, which is located anteriorly; the pubofemoral ligament, which is located inferiorly; and the ischiofemoral ligament, which is located posteriorly. Additional support is provided by the labrum acetabulare, a thick band of cartilage surrounding and extending out from the acetabulum and adding depth to the cavity. A flat, thin-shaped ligament, the ligamentum teres, attaches the head of the femur to the acetabulum centrally.
The muscles surrounding the hip joint are large and powerful. They can be divided into three main groups—anterior, medial, and posterior. The anterior muscles include the iliopsoas, tensor fasciae latae, sartorius, and quadriceps femoris. Muscles within the medial compartment adduct the thigh and include the pectineus; gracilis; obturator externus; and adductor magnus, brevis, and longus. Posterior muscles extend the hip and include the semitendinosus, semimembranosus, and biceps femoris.
It is essential that one clearly understands the precarious vascular supply to the proximal femur. The vascular anatomy consists of three main sources, listed in order of importance (Fig. 18–2).
The vascular ring around the base of the femoral neck sends intracapsular vessels (retinacular vessels) important in maintaining perfusion to the femoral head.
Femoral circumflex and retinacular arteries
Vessel of the ligamentum teres
The femoral circumflex arteries surround the base of the femoral neck and give rise to retinacular arteries that ascend up to supply the femoral head. Disruption of the retinacular blood vessels results in avascular necrosis (AVN) of the femoral head in 84% of cases.1 In occult, nondisplaced fractures of the femoral neck, the retinacular vessels are not disrupted, and early diagnosis should prevent complications.
Routine radiographs including anteroposterior (AP) and external rotational views (i.e., rolled or frog-leg lateral) are adequate in most cases (Fig. 18–3). A cross-table, lateral view is obtained in a patient with a suspected fracture in place of the external rotational view. This radiograph ...