Professional Pitchers Display Differences in Ulnar Collateral Ligament Morphology and Elbow Gapping Following UCLR Compared to Uninjured Pitchers

OBJECTIVES: Ulnar collateral ligament reconstruction(UCLR) of the elbow has received much attention given the rise in incidence among all pitchers. Recent studies have demonstrated stress ultrasonography is a critical tool in the evaluation of the UCL. . No study, has dynamically evaluated the UCL in uninjured professional pitchers under stress, nor has any study evaluated the ability of UCL reconstruction (UCLR) to restore normal kinematics. The purpose of this study was to compare ulnohumeral gapping and UCL thickness in both uninjured professional pitchers and those who had undergone UCLR during a moving valgus stress test. We hypothesized that the UCL will be thicker and the ulnohumeral joint will display adaptive gapping in D arms compared to ND arms. Furthermore we hypothesized that UCLR would restore gapping and UCL morphology. METHODS: Ultrasonography was used to assess the UCL of 70 asymptomatic professional baseball pitchers during spring training (history of UCLR, n=6). A 5-MHz linear-array transducer was used to capture images of the dominant (D) and non-dominant (ND) throwing elbows at the maximal cocking position under two loaded conditions within the moving valgus stress test arc:(1) gravity stress and (2)-10 lbs of valgus force using a dynamometer. Ulnohumeral gapping and UCL thickness was measured on sagittal images using the OsiriXTM platform. All measures displayed reliability with intraclass correlation coefficients (ICC) ranging from ICC(2,1)=0.94 -0.98 with Standard error of measure (SEM) of 0.14-0.26 mm for intra-rater and ICC(2,k)= 0.82-0.87; SEM=0.38-0.65mm for inter-rater reliability. Separate mixed model ANOVAs(side X UCL) were used to compare pitchers’ D and ND arm variables between those with UCLR to those who never had a UCL injury.(α=0.05) RESULTS: The D arms of uninjured pitchers demonstrated increased gapping compared to ND arm (5.4 ± 1.2vs4.7± .86 p=0.001) Players with a UCLR demonstrated decreased gapping compared to both the ND and uninjured D arms of professional pitchers. (2.6±2.9 vs 4.2±1.2; P=0.002), Furthermore, the UCLR elbows demonstrated greater D arm ligament thickness when compared to D arms in pitchers without UCL injury history(.17±.07vs.11 ±.08;P=0.03). CONCLUSION: This is the first study to our knowledge evaluating stress ultrasonography of the UCL during the moving valgus stress test in professional pitchers. Our data demonstrates that the UCLR results in a thicker, stiffer construct with less medial elbow gapping than even the normal condition. Using ultrasound to evaluate the UCL it was shown to be reliable, more efficient and provides a clinically feasible method to assess UCL thickness, loaded joint gapping, and stiffness post-UCLR. Future studies may consider this approach to evaluate surgical techniques and graft types for UCL reconstruction