Porth's Essentials of Pathophysiology, 4e

Disorders of the Skeletal System: Trauma, Infections, Neoplasms, and Childhood Disorders 1083

C h a p t e r 4 3

static stabilizers, which control patellar tracking; that is, the movement of the patella within the femoral troch- lea. 15 The disorder, also called “runner’s knee,” occurs most frequently in young adults and is often associated with jogging, volleyball, and basketball. Persons with this disorder typically complain of pain, particularly when climbing stairs or sitting with the knees bent. The pain is usually difficult to localize, and swelling of the knee is not characteristic of the disorder. Occasionally, the person experiences weakness of the knee. Diagnosis is usually based on history and physical examination. Radiography may be used as an adjunct to the history and physical. Treatment consists of relative rest and physical therapy. 15 Reduction of loading of the patellofemoral joint and surrounding tissues is the first step to reduce pain. Inappropriate or excessively worn footwear may contribute to the problem and need to be replaced. Although a variety of braces, sleeves, and straps have been used in treatment of the disorder, stud- ies have found no significant benefit from their use. Hip Injuries The hip is a ball-and-socket joint in which the femo- ral head articulates deeply in the acetabulum. 10 The proximal part of the femur consists of a head, neck, and greater trochanter. The vascular anatomy of the femo- ral head, which receives its main blood supply from the lateral and medial circumflex femoral arteries and the obturator artery, is of critical importance in any disorder of the hip (Fig. 43-4). Disease or injuries that compro- mise blood flow may damage the viability of the femoral head and lead to avascular necrosis or osteonecrosis. Dislocations of the Hip. Dislocations of the hip in which the femoral head is displaced from the acetabu- lum are commonly the result of severe trauma and are

usually posterior in direction. They typically result from the knee being struck while the hip and knee are in a flexed position. 8 This force drives the femoral head out of the acetabulum posteriorly. Anterior dislocations are less common and usually result from a force on the knee with the thigh abducted. Hip dislocation is an emergency. 5,8 The disorder is typically accompanied by severe pain and inability to move the lower extremity. In the dislocated position, great tension is placed on the blood supply to the femo- ral head and avascular necrosis may result. To prevent this complication, early reduction is indicated. Weight bearing is usually limited after reduction to prevent the dislocation from reoccurring and allow healing to occur. Fractures of the Hip. Hip fracture is a major public health problem in the Western world, particularly among the elderly. 16–18 It results in hospitalization, disability, and loss of independence. Risk factors for hip fracture include physical inactivity, excessive consumption of alcohol, use of certain psychotropic drugs, residence in an institution, visual impairment, and dementia. 16 Osteoporosis is an important contributing factor. Most hip fractures result from falls. Occasionally, the person may actually fracture the hip before falling, the fracture representing the completion of an incomplete break. The characteristics of the fall (the direction, site of impact, and protective response) and environmental factors are recognized as important influences for the risk of hip fracture from a fall. A hip fracture usually involves the proximal femur. Such fractures are commonly categorized according to the anatomic site in which they occur. 9,16–18 Femoral neck fractures are located in the area distal to the femoral head but proximal to the greater and lesser trochanters and are considered intracapsular because they are located

Head

Ilium (coronal section)

Fibrous capsule

Articular cartilage

Synovial membrane

Acetabular fossa

Greater trochanter

Obturator artery

Synovial membrane Fibrous capsule Lateral circumflex femoral artery

Ligament of head of femur

Artery to head of femur (acetabular branch of obturator artery)

FIGURE 43-4. Blood supply of the head and neck of the femur (anterior view). A section of the bone has been removed from the femoral neck. (Modified from Moore KL, Agur AM, Dalley AF. Essential Clinical Anatomy. 4th ed. Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams &Wilkins; 2010:380.)

Acetabular labrum

Neck of femur

Lesser trochanter

Medial circumflex femoral artery

Retinacular folds