DISLOCATION OF ELBOW JOINT
Dislocations of the elbow joint are the most common dislocations after those of the shoulder and finger joints. Swelling, pain, and pseudoparalysis of the arm are acute signs and symptoms of dislocation, and elbow deformity is visible on both clinical and radiographic examinations.
Acute elbow dislocations are classified as anterior or posterior, with the direction determined by the position of the radius and ulna relative to the humerus. In addition to the anterior or posterior direction of dislocation, the forearm bones can also be displaced medially or laterally. Posterior elbow dislocations are by far the most common type and usually result from a fall on an outstretched hand. The rare, but extensively studied, anterior dislocation of the elbow is usually an open injury and may lacerate the brachial artery. Rarely, the radius and ulna dislocate in different directions, an injury called a “divergent” dislocation.
Dislocations of the elbow result in a pattern of ligamentous injury that depends on the direction of dislocation. For posterior dislocations, the ligamentous injury typically starts laterally, disrupting the lateral collateral ligament complex first; it then moves medially, disrupting the anterior and posterior joint capsule, followed by the medial collateral ligament complex. Elbow dislocations are sometimes accompanied by fractures as well, including fractures of the medial or lateral epicondyle, olecranon, radial head or neck, or coronoid process of the ulna. As discussed previously, the combined injury pattern of an elbow dislocation associated with both a radial head fracture and a coronoid fracture has been termed a terrible triad injury.
Fracture-dislocations of the elbow, especially displaced fractures of the olecranon, coronoid process, and radial head, often require surgical fixation to ensure longterm stability and function of the joint. An avulsed medial epicondyle can become wedged inside the joint during reduction of the dislocation. Only occasionally can closed manipulation free the avulsed fragment from within the joint; arthrotomy is usually needed to remove the fragment and return it to its anatomic position.
Reduction Of Dislocation Of Elbow Joint
A posterior dislocation of the elbow is reduced with distal traction. While an assistant secures the proximal humerus, the examiner applies traction in the line of the forearm, holding the forearm supinated, and then gently flexes the elbow joint to allow the humerus to reduce into the olecranon fossa. If the elbow is reduced immediately after dislocation, complete muscle relaxation may not be needed; if treatment is delayed, conscious sedation, axillary block, or general anesthesia is used to induce complete muscle relaxation. Radiographs should be obtained after reduction to confirm that the elbow joint is concentrically aligned. The neurovascular status of the distal limb is checked both before and after reduction. Any changes or abnormalities suggest entrapment of a nerve or vessel during reduction, which must be relieved promptly to prevent a long-term deficit.
After the initial reduction, the examiner moves the elbow through a full range of motion to assess its stability and to check for crepitus in the joint. Crepitus strongly suggests loose fracture fragments in the joint. If the elbow remains stable through a full range of motion, it is immobilized in 90 degrees of flexion in a posterior splint. The neurovascular status of the limb is monitored frequently while the elbow is splinted to ensure that a deficit does not develop. Most isolated elbow dislocations are treated with splint immobilization for a short period of time (1 to 2 weeks) before beginning range-of-motion exercises. The exercises should be gentle initially but as active as symptoms permit. The physician’s assessment of the degree of stability after reduction helps determine what range of motion to allow and when to begin the exercise program.
Elbow dislocations cause few long-term complications. By far the most common is residual joint stiffness, particularly loss of extension. Although some degree of stiffness almost always persists, early active motion can minimize this problem. The older the patient, the earlier active elbow movement should be started.
Myositis ossificans, another complication of elbow dislocation, results from muscle injury at the time of dislocation. Myositis ossificans is more likely to develop after severe injuries, such as those that are high energy or associated with fractures, and when treatment has been delayed. Early passive motion is discouraged in patients with dislocation and muscle injury because excessive muscle stretching may precipitate the development of myositis.
Recurrent dislocations after an isolated elbow dislocation are uncommon and are thought to be due to extensive collateral ligament damage (medial and lateral) or an occult fracture. Surgery to repair or reconstruct the collateral ligaments may be necessary in this situation.