Magnetic resonance imaging in diagnosis of chronic posterolateral rotatory instability of the elbow.

Posterolateral rotatory instability of the elbow can be difficult to diagnose and requires a high degree of clinical suspicion. Cases of chronic posterolateral rotatory instability (symptoms present more than 1 year) may be an even more perplexing subgroup. This is a case report of a patient with a 30-year history of intermittent elbow instability. Clinical examination was equivocal, and magnetic resonance imaging was unable to define any ligamentous injury around the elbow. Examination under anesthesia and surgical findings were consistent with complete disruption of the lateral ulnar collateral ligament. The 12-month follow-up after surgical reconstruction showed complete resolution of symptoms. Posterolateral rotatory instability is a diagnosis largely made by examination under anesthesia. A thorough history and a high clinical suspicion are necessary to support the physician's decision to place the patient under anesthesia. Confirmation of a chronic tear of the lateral ulnar collateral ligament of the elbow with magnetic resonance imaging can be difficult and sometimes misleading.