UCL Tear: AI-Powered MRI Analysis

The T-sign is an MRI finding in which contrast material or fluid dissects between the distal footprint of the anterior band of the ulnar collateral ligament and the sublime tubercle of the ulna, creating a T-shaped appearance on coronal images. It is highly specific for a complete UCL avulsion from its ulnar attachment. Partial tears more commonly appear as intrasubstance signal abnormality or proximal humeral-side detachment without the T-sign. MRI arthrography improves sensitivity for partial tears compared to routine MRI.

Overhead throwing athletes, particularly baseball pitchers, are at greatest risk because the valgus torque generated during the late cocking and acceleration phases of pitching can approach or exceed the ultimate tensile load of the UCL. Cumulative microtrauma over years of high-pitch-count throwing leads to progressive attenuation and eventual tear. Gymnasts, volleyball players, and javelin throwers are also at elevated risk. Skeletally immature athletes may sustain a medial apophyseal avulsion rather than a true ligament tear.

Tommy John surgery is UCL reconstruction using a tendon graft, most commonly the palmaris longus or gracilis, woven through bone tunnels in the medial epicondyle and ulna using the docking technique or a figure-of-eight construct. Return to competitive throwing typically requires 12 to 18 months of rehabilitation. Studies in professional baseball pitchers report return-to-sport rates of approximately 80 to 90 percent, with many athletes returning to their previous or higher level of competition, though a subset experience residual elbow stiffness or ulnar nerve complications.