Porth's Essentials of Pathophysiology, 4e

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Musculoskeletal Function

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subsequent pain over a bone is common in fatigue frac- tures. Stress fractures in the tibia may be confused with “shin splints,” a nonspecific term for pain in the lower leg from overuse in walking and running, because they frequently are not apparent on x-ray films until 2 weeks after the onset of symptoms. 4,5 Pathologic stress fractures occur when normal stress is applied to bones that have been weakened by disease or tumors. 8 Fractures of this type may occur spontane- ously with little or no stress. The underlying disease state can be local, as with infections, cysts, or tumors, or it can be generalized, as in osteoporosis, Paget disease, or disseminated tumors. Classification Fractures usually are classified according to location, type, and direction or pattern of the fracture line 5,8 (Fig. 43-5). A fracture of the long bone is described in relation to its position in the bone—proximal, midshaft, and distal. Other descriptions are used when the frac- ture affects the head or neck of a bone, involves a joint, or is near a prominence such as a condyle or malleolus. The type of fracture is determined by its commu- nication with the external environment, the degree of break in continuity of the bone, and the character of the fracture pieces. A fracture can be classified as open or closed. When the bone fragments have broken through the skin, the fracture is called an open or compound fracture. In a closed fracture, there is no communication with the outside environment.

within the capsule of the hip joint. Intertrochanteric fractures occur in the metaphyseal region between the greater and lesser trochanter. Subtrochanteric fractures are those that occur just below the greater trochanter. The location of a hip fracture is important in terms of blood flow to the femoral head, which receives its blood supply from vessels that course proximally up the fem- oral neck 10 (see Fig. 43-4). Subtrochanteric and inter- trochanteric fractures that occur distal to these vessels do not usually disturb the blood supply to the femoral head, whereas femoral neck fractures, particularly those involving marked displacement, often disrupt the blood supply to the femoral head and are therefore associated with an increased incidence of complications (nonunion and avascular necrosis). Most hip fractures are diagnosed based on clinical findings and standard radiographs. A bone scan or MRI may be done when the radiograph is negative, but the clinical findings support the diagnosis of hip fracture. The primary goal of treatment for a hip fracture is a return to the preinjury level of function as soon as pos- sible. 8 Undisplaced or impacted fractures have a bet- ter prognosis in terms of healing and are often treated nonoperatively or by simple internal fixation to provide stability. Displaced intracapsular fractures in the elderly are usually best treated by surgical hip replacement and early mobilization. 5 Young, healthy people are treated by reduction of the fracture (if needed) and internal fixa- tion. This method allows for preservation of the femoral head, which in this age group is desirable because the long-term results are better than with prosthetic replace- ment. Intertrochanteric fractures are usually treated with open reduction and internal fixation. This allows for early ambulation by eliminating pain at the fracture site. Fractures A fracture represents a disruption in the continuity of a bone. 8,18,19 Normal bone can withstand considerable compression and shearing forces and, to a lesser extent, tension forces. A fracture occurs when more stress is placed on the bone than it is able to absorb. Grouped according to cause, fractures can be divided into three major categories: (1) fractures caused by sudden injury, (2) fatigue stress fractures, and (3) pathologic stress fractures. The most common fractures are those result- ing from sudden injury. The force causing the fracture may be direct, such as a fall or blow, or indirect, such as a massive muscle contraction or trauma transmitted along the bone. For example, the head of the radius or clavicle can be fractured by the indirect forces that result from falling on an outstretched hand. Stress fractures are incomplete fractures. 8,20 They may be described as either fatigue or pathologic frac- tures. Fatigue stress fractures occur when excess stress is applied to normal bone. They may occur in any weight- bearing bone, but they are most common in the metatar- sal, neck of the femur, calcaneus, tibia, fibula, and pelvis. Fatigue stress fractures typically occur in unconditioned athletes. Clinically, a history of unusual stress with

Proximal

Midshaft

Distal

Spiral

Oblique

Transverse

Impacted

Comminuted

Segmental

Butterfly

FIGURE 43-5. Classification of fractures. Fractures are classified according to location (proximal, midshaft, or distal), the direction of fracture line (transverse, oblique, spiral), and type (comminuted, segmental, butterfly, or impacted).