Keywords: elbow, UCL, throwing injury (PubMed Search)
29 yo baseball pitcher presents with right medial elbow pain. He felt a painful “pop” and could not continue to throw (due to loss of speed and control). Also notes mild paresthesias in 4th and 5th digits.
Ulnar collateral ligament (UCL) injury
Sprain of the UCL of the elbow can occur either as an acute injury or as the result of chronic excessive valgus stress due to throwing. This injury is seen in javelin throwers and baseball pitchers. Most recently, Angels superstar Shohei Ohtani suffered a torn UCL.
While traditionally this injury pattern was thought to occur in older, high-level pitchers (high velocity throwing), we are increasingly seeing this in younger athletes.
The repeated valgus stress of pitching leads to micro tearing and inflammation of the ligament. Over time, this leads to scarring and calcification and then ligament rupture.
This injury is more likely to happen in pitchers who “open up too soon” in their throwing motion. Fatigue related changes seen first in leg and core mechanics cause pitchers to open up earlier, increasing stress to the shoulder and the UCL of the elbow. Other risk factors include high velocity pitching, insufficient recovery time, and chronic overuse. The importance of proper pitching mechanics is very important as players whose pitching motion produces greater elbow valgus loads and shoulder external rotation torque are at increased risk for UCL tears.
Approximately one half of the torque generated during a fastball pitch is transmitted to the UCL. Well developed muscles about the elbow can dissipate enough energy that acute tearing is rare.
The athlete with a UCL sprain will complain of medial elbow pain that increases during the acceleration phase of throwing.
On examination, there is localized tenderness directly over the UCL:
Stress testing of the UCL causes both pain and demonstrates laxity.
Moving Valgus Stress Test:
Place elbow in the “90/90” position. Apply a valgus stress while ranging elbow through full arc of flexion and extension. A positive test will reproduce apprehension, pain or instability at the UCL origin between 70 and 120 degrees.