Preoperative evaluation of the ulnar collateral ligament by magnetic resonance imaging and computed tomography arthrography. Evaluation in 25 baseball players with surgical confirmation.

A prospective study was completed on 25 baseball players with medial side elbow pain. They were evaluated preoperatively with both computed tomography arthrogram and magnetic resonance imaging examinations of the elbow to assess the ulnar collateral ligament. At surgery, 16 of 25 patients had an abnormal ulnar collateral ligament and 9 patients had a normal ulnar collateral ligament. The computed tomography arthrogram detected abnormalities in 12 of the 14 patients with ulnar collateral ligament tearing (sensitivity, 86%). The magnetic resonance imaging scan indicated abnormalities in 8 of 14 patients (sensitivity, 57%). The specificity of the computed tomography arthrogram was 91% and the magnetic resonance imaging was 100%. A newly described "T-sign" was seen on the computed tomography arthrogram in the patients with an undersurface tear of the ulnar collateral ligament. This represented the dye leaking around the detachment of the ulnar collateral ligament from its bony insertion but remaining contained within the intact superficial layer of the ulnar collateral ligament and capsule. Both the computed tomography arthrogram and the magnetic resonance imaging scan were accurate in diagnosing a complete tear of the ulnar collateral ligament preoperatively in all cases. The main advantage of the computed tomography arthrogram was in evaluating the partial undersurface tear.