Posterolateral Rotatory Instability

Posterolateral rotatory instability (PLRI) is the most common type of chronic lateral elbow instability. It has been well-defined in the literature by O'Driscoll and others since 1991, yet our understanding of the pathophysiology and biomechanical abnormalities associated with this injury is still evolving. PLRI is part of a spectrum of injury to the soft tissues of the lateral elbow, primarily the lateral ulnar collateral ligament, usually following a traumatic elbow injury, such as an elbow dislocation. There are three stages of PLRI: (1) posterolateral subluxation, (2) incomplete dislocation with the coronoid lodged beneath the trochlea, and (3) complete dislocation of the elbow joint with the coronoid located behind the humerus.

In children, the elbow is the most commonly dislocated major joint, whereas in adults, the elbow is the second most commonly dislocated joint, after the shoulder. Dislocations represent about 10% to 25% of all elbow injuries. Like other upper extremity injuries, elbow dislocations can occur from direct trauma, a FOOSH (fall on an outstretched hand) injury, or a strong directional or levering force on the elbow. Elbow dislocations typically occur in children older than 13 years, after the physes around the elbow are closed. However, it is not uncommon to sustain a combined elbow fracture and dislocation. The highest incidence of elbow dislocations is in the under-20 age-group, and the majority are associated with sports activity. In general, prompt closed reduction of simple elbow dislocations results in favorable outcomes; however, when residual instability persists despite a period of proper immobilization, then significant dysfunction can develop. Complications include loss of range of motion (ROM), structural instability, nerve palsies, and muscular weakness.

Other causes of PLRI include apparent “elbow sprains,” prior tennis elbow release, radial head excision, and multiple corticosteroid injections in [Page 1116]the lateral elbow. Finally, PLRI has been associated with congenital or acquired cubitus varus deformities, which can develop secondary to supracondylar fractures in children.