SLAP Tear (Not Repair) Decreases Pitcher Trunk Rotation

It is the superior labrum, anterior to posterior tear itself, not the surgical repair that causes a decrease in trunk rotation at foot contact in baseball pitchers, according to a new study.

In the study, “Decreased Trunk Rotation at Foot Contact in Professional Baseball Pitchers with Prior, Conservatively Managed Superior Labrum Anterior and Posterior Tears: A Propensity-Score Matched Analysis,” the researchers compared kinematic and kinetic parameters between fully recovered professional pitchers with prior shoulder injury treated conservatively with those professional pitchers with no prior shoulder injury.

The study was published online November 13, 2021in the journal Arthroscopy.

Twenty-six fully recovered professional baseball pitchers with a history of shoulder injury treated conservatively were 4:1 propensity-scored matched by age, height, weight, handedness, and ball velocity to pitchers with no prior injury history.

For the study, the baseball pitchers with a history of shoulder injury pitched eight to ten fastball pitches using 3D-motion capture (480 Hz). All shoulder injuries took place within one to four years based on biomechanical evaluation and were severe enough to keep pitchers from playing anywhere between one to 12 months.

Twenty-two kinematic and 11 kinetic parameters were compared between the two groups. In addition, sub-analysis comparisons of pitchers with prior superior labrum anterior-posterior (SLAP) injury as well as rotator cuff tendinitis were also performed.

Overall, the most commonly reported injury was SLAP tears (42.3%), with rotator cuff tendinitis/shoulder impingement the next (26.9%).

The 26 prior injured pitchers showed no significant differences in kinematic and kinetic factors compared with the control group. However, the SLAP tear subgroup did demonstrate significantly less trunk rotation at foot contact compared to control (34.1±4.9 vs. 39.2±10.2°, p=0.0075).

“Fully recovered professional baseball pitchers with shoulder injuries treated conservatively showed no significant differences in kinetics or kinematics compared to their propensity-matched counterparts, suggesting shoulder injury alone may not greatly alter pitching mechanics. However, while prior groups have demonstrated a decrease in trunk rotation at foot contact after surgical repair for SLAP tear, our study suggests that this kinematic change may alternatively originate with the injury itself,” the authors wrote.

“Understanding the etiology of biomechanical adaptations by pitchers after injury can better aid clinicians and coaching staff in providing individualized and specific care to the throwing athlete,” they added.