The unstable elbow: An evidence-based approach to evaluation and management

### Pathoanatomy The pathoanatomy of an elbow dislocation can be thought of as a disruption of the circle of soft tissue or bone, or both, that begins on the lateral side of the elbow and progresses to the medial side in three stages (Fig. 1-A). In stage 1, the lateral collateral ligament is partially or completely disrupted (the ulnar part is disrupted). This disruption results in posterolateral rotatory subluxation of the elbow, which can reduce spontaneously (Fig. 1-B). Stage 2 involves additional disruption anteriorly and posteriorly. There is an incomplete posterolateral dislocation of the elbow in which the concave medial edge of the ulna rests on the trochlea. On a lateral radiograph of the elbow, the coronoid process appears to be perched on the trochlea. This dislocation can be reduced with use of minimal force or by the patient manipulating his or her own elbow. Stage 3 is subdivided into three parts. In stage 3A, all of the soft tissues around and including the posterior part of the medial collateral ligament are disrupted, leaving only the important anterior band (the anterior medial collateral ligament) intact. This permits posterior dislocation by a posterolateral rotatory mechanism. The elbow pivots on the intact anterior band of the medial collateral ligament. Reduction is accomplished by gentle manipulation of the elbow beginning with supination and valgus stress, temporarily recreating the deformity, followed by application of traction, varus stress, and pronation simultaneously. The intact anterior medial collateral ligament provides stability if the forearm is kept in pronation to prevent posterolateral rotatory subluxation during valgus stress-testing. Stage-3A instability is most commonly seen in the presence of fractures of the radial head and coronoid process. In stage 3B, the entire medial collateral complex is disrupted. Varus, valgus, and rotatory instability are all present following reduction. In stage 3C, the instability …