Elbow instability.

Elbow instability is a spectrum from subluxation to dislocation, with corresponding clinical and pathologic features and therapeutic implications. A classification that unifies these aspects is presented. Posterolateral rotational displacement of the ulna (with the radius) on the humerus appears to be the common mechanism. Acute dislocations can be reduced in supination and tested for valgus stability in pronation. Treatment is determined by the stability following reduction. When there are fractures, the principle is to fix the bones so that the only limitation is the ligaments and then to repair them if the elbow is not stable enough to permit early motion. The three prerequisites for stability of the ulnohumeral articulation are an intact joint surface, anterior medial collateral ligament, and ulnar part of the lateral collateral ligament. Recurrent instability is usually due to insufficiency of the ulnar part of the lateral collateral ligament complex, the lateral ulnar collateral ligament (LUCL), with attenuation of the other secondary soft tissue constraints on the lateral side. Reconstruction of the lateral ulnar collateral ligament typically corrects the problem. Chronic dislocations are treated by similar techniques after releasing contractures and resurfacing the joint with biologic tissue if it is irreversibly damaged.