Porth's Essentials of Pathophysiology, 4e

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Musculoskeletal Function

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is not sufficient to permit strong tendon pulls for 6 to 8 weeks. 6 During the healing process, there is a danger that muscle contraction will pull the injured ends apart, causing the tendon to heal in the lengthened position. There is also a danger that adhesions will develop in areas where tendons pass through fibrous channels, such as in the distal palm of the hands, rendering the A dislocation is the abnormal displacement of the artic- ulating surfaces of a joint such that surfaces are not in contact. It usually follows a severe trauma that disrupts the holding ligaments. Dislocations are seen most often in the shoulder and acromioclavicular joints. A sublux- ation is a partial dislocation in which the bone ends in the joint are still in partial contact with each other. Dislocations can be congenital, traumatic, or patho- logic. Congenital dislocations occur in the hip or knee. Traumatic dislocations occur after falls, blows, or rota- tional injuries. For example, auto accidents often cause dislocations of the hip and accompanying acetabular fractures because of the direction of impact. In the shoul- der and patella, dislocations may become recurrent, especially in athletes. They recur with the same motion but require less and less force each time. Less common sites of dislocation, seen mainly in young adults, are the wrist and midtarsal region. They usually are the result of direct force, such as a fall on an outstretched hand. Pathologic dislocation in the hip is a late complication of infection, rheumatoid arthritis, paralysis, and neuro- muscular diseases. Diagnosis of a dislocation is based on history, physical examination, and radiologic findings. The symptoms are pain, deformity, and limited movement. The treatment depends on the site, mechanism of injury, and associated injuries such as fractures. Dislocations that do not reduce spontaneously usually require manipulation or surgical repair. Immobilization is necessary for several weeks after reduction of a dislocation to allow healing of the joint structures. In dislocations affecting the knee, alter- natives to surgery are isometric quadriceps-strengthening exercises and a temporary brace. Shoulder and Rotator Cuff Injuries The shoulder is a complex series of joints that produces extraordinary range of motion but lacks stability. This instability, combined with its relatively exposed posi- tion, makes the shoulder extremely vulnerable to inju- ries including fractures, dislocations, and degenerative processes such as rotator cuff disorders. 5,8,9 The shoulder is composed of three bones: the scapula, the clavicle, and the humerus 10 (Fig. 43-2). The scapula is a thin bone that articulates widely and closely with the chest wall. It also articulates with the humerus by way of its small, shallow glenoid cavity and with the clavicle at the acromion process. The clavicle, which is held firmly in place by ligaments at the sternum and acromion, forms the only bony connection between the axial skeleton and the upper extremity. Clavicle fractures tendon useless. Dislocations

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Grade 2

ligament and anterior cruciate ligament) and elbow (the ulnar side). As with a strain, the soft tissue injury that occurs with a sprain is not evident on the radiograph. An MRI is the most sensitive test for evaluation of a soft tissue injury. The treatment of muscle strains and ligamentous sprains involves rest, ice, compression, and elevation (RICE). 5 For an injured extremity such as the ankle, elevation of the injured body part followed by local application of cold may be sufficient. Compression, accomplished through the use of adhesive wraps, helps to reduce swelling and provide support. For a muscle strain, the affected joint is immobilized until the pain and swelling have subsided. In a sprain, the affected joint is immobilized for several weeks. Immobilization may be followed by graded active exercises. Early diag- nosis, treatment, and rehabilitation are essential in pre- venting chronic ligamentous instability. Healing of the dense connective tissues in tendons and ligaments is similar to that of other soft tissues. If prop- erly treated, injuries usually heal with the restoration of the original tensile strength. Repair is accomplished by fibroblasts from the inner tendon sheath or, if the tendon has no sheath, from the loose connective tissue that surrounds the tendon. 6,7 Capillaries infiltrate the injured area during the initial healing process and sup- ply the fibroblasts with the materials they need to pro- duce large amounts of collagen. Formation of the long collagen bundles occurs within the first 2 weeks, and although tensile strength increases steadily thereafter, it Grade 4 FIGURE 43-1. Degrees of sprain on the medial side of the right knee: grade 1, mild sprain of the medial collateral ligament; grade 2, moderate sprain with hematoma formation; grade 3, severe sprain with total disruption of the ligament; and grade 4, severe sprain with avulsion of the medial femoral condyle at the insertion of the medial collateral ligament. Grade 3