Scapulothoracic joint function and its association with throwing-related injuries in collegiate baseball pitchers: a prospective cohort study.

BACKGROUND

Throwing-related shoulder and elbow injuries are common among collegiate baseball pitchers; however, prospective evidence on scapulothoracic (ST) joint function as a risk factor is limited. This study prospectively investigated whether ST joint stability was associated with throwing-related injuries.

METHODS

Twenty-seven collegiate pitchers were prospectively categorized into injury and noninjury groups during the 12-month follow-up. Scapular and trunk positional coordinates were recorded using a 3D scanner during preseason screening under 2 conditions: (1) 90° scapularplane abduction with the elbow flexed and palm on the head (elevation trial) and (2) the same position with manual resistance applied to the distal forearm (resistance trial). ST joint Euler angles were calculated, and ΔST angles between trials were derived to quantify scapular stability, with larger ΔST joint angle along X-axis values indicating excessive upward rotation during the resistance trial. Time-to-event analysis using Cox proportional hazards regression was performed with ΔST and age as predictors. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated.

RESULTS

A greater ΔST joint angle along X-axis was significantly associated with increased injury hazard; each 1° increase corresponded to a 34% higher risk (HR = 1.34, 95% CI: 1.04-1.72, P = .02). Age was also a significant predictor (HR = 3.60, 95% CI: 1.33-9.74, P = .01).

CONCLUSION

Excessive scapular upward rotation during a throwing resistance posture, quantified by the ΔST joint angle along X-axis, was significantly associated with an increased risk of throwing-related shoulder and elbow injuries in collegiate pitchers.