– The ulnar collateral ligament (UCL) is one of the ligaments located on the inside of the elbow. The ulnar collateral ligament helps maintain the relationship between the bones in your forearm and arm.
For baseball and softball pitchers, the ulnar collateral ligament of the elbow provides stability to the elbow during the late cocking phase and early acceleration phase of pitching. The highest amount of force to the ligament occurs during pitching, when the elbow goes from flexion to rapid extension. It has been reported that every time a high velocity pitch is thrown, the UCL is placed at maximum tensile strength. Over time, with repetitive throwing, an injury to the elbow UCL can occur. The severity of a UCL injury may range from a partial thickness tear up to a full thickness tear.
Diagnostic testing to determine if a UCL injury is present has ranged from plain x-rays of the elbow, to stress x-rays, MRI without contrast and MRI with an arthrogram.
The gold standard to document that an ulnar collateral ligament injury is present on a stress x-ray is if an opening of greater than 3 mm is present medially. This increased distance or widening is a sign that a UCL injury is present.
A study published in the October 2014 Journal of Shoulder and Elbow Surgery authored by James R. Andrews M.D. and colleagues, compared patients that had surgical documentation of a complete tear of the ulnar collateral ligament. The researchers found that the stress x-rays obtained pre-operatively only revealed on average an opening of 0.6 mm compared to the healthy uninjured side. They found in athletes with a partial ulnar collateral ligament tear, stress x-rays of the elbow only opened up 0.1 mm.
They used a Telos stress device with 15 daN of pressure applied to the patients elbow prior to taking the film. After the Telos stress device was in place the x-ray was obtained. This allowed a standard and reproducible amount of force to be applied to each injured thrower’s elbow.
Stress x-rays of the elbow are not a good way to diagnosis ulnar collateral injuries of the elbow. It would be very difficult to measure such small incremental distances between the two x-rays with accuracy. These research findings suggest that an MRI / arthrogram is the most accurate diagnostic test to identify a UCL injury.