The appendicular skeletal structures include a set of long bones for both the upper and lower extremities. The special functions associated with these structures provide unique fracture and, thus, healing patterns. Since the lower extremity is weight bearing, specific approaches to fracture management which allow some level of early weight bearing have evolved to better minimize the secondary changes associated with immobilization and a non–weight-bearing status. As a general rule, lower extremity management is all about function (enable return to weight bearing and thus ambulation), whereas upper extremity management is more likely to include a level of attention to cosmesis. The long bones each have inherent patterns of loading related to their individual roles, and thus have specific patterns of injury. These will be addressed in each section of this chapter, primarily as fractures of the shafts of the long bones. Those fractures which include the articular portions of the bones are discussed in the chapters of their respective joints.
LONG BONE BIOLOGY AND FUNCTION
The long bones are designed to allow placement of the hand in space for function or movement of the body (ambulation) through the transmission and support of weight-bearing loads. These bones can be described in a variety of ways but can easily be perceived as specifically shaped (slightly bent) polyvinyl chloride (PVC) (cortical bone) pipes, firmly packed with dense clay (cancellous bone), and the ends of which have special smooth surfaces (articular covering) to allow them to be joined one to another. These structures receive “pure” loading (application of force) in four ways: tension, compression, bending, and torsion. Fractures are thus linked to each of these loading types: tension—avulsion injury, often soft tissue to bone; compression—compressed or impacted fractures; bending—transverse fractures; torsion—spiral fractures. Importantly, they may also have combination loading that provides combined patterns of fracture, resulting in oblique or oblique and transverse fractures. Displacement and whether the skin is intact are then added in the final fracture description. The radiographic presentation then is often very well predicted by the injury mechanism with the type and direction of load and the magnitude as well as velocity, all playing a role in the fracture (Figures 9-1 to 9-6).1
Avulsion fracture of medial epicondyle. Tension loading from musculotendinous units can separate the bony attachment point from the main portion of the bone to result in an avulsion fracture.
Impacted fracture of femoral neck. Beyond capacity compressive loading of the bone can result in an impact fracture. Note the shortening of the femoral neck in this radiograph.
Transverse fracture of femur. Bending forces imposed on long bones will typically result in a transverse fracture line across the long axis of the bone, ...