Sonographic Evaluation of Supraspinatus Cross-sectional Area in Collegiate Baseball Players

Abstract

To establish the normal thickness of the supraspinatus tendon in collegiate baseball players with the use of ultrasound and to determine whether there are any significant differences between the dominant and nondominant supraspinatus thickness. A cross-sectional observational study. An outpatient clinical setting. Twelve healthy, asymptomatic collegiate pitchers between the ages of 19 and 22 years. Sonographic evaluation of 12 asymptomatic pitchers (9 right-hand dominant and 3 left-hand dominant) between the ages of 19 and 22 years was performed in a transverse plane (short axis) and longitudinal view (long axis) of their right and left shoulders. Maximum thickness was measured in both the long- and short-axis views. On the long-axis view, measurement was taken at the point where there was maximal height observed at the footprint insertion. Mixed-model analysis of variance was used to test for differences in tendon thickness across factors. Post hoc contrasts were performed with a Tukey adjustment for the P values. The mean ± SD values, side-to-side difference, and difference between dominant and nondominant values were calculated and statistically analyzed for differences. An ultrasound examination showed a significant 3-way interaction (P = .038) for view by side of hand dominance. Post hoc contrasts revealed that supraspinatus tendon thickness for right-handed pitchers in the long-axis view on the right side showed a mean value of 8.0 ± 0.32 mm versus the long-axis view on the left side of 6.5 ± 0.34 mm (P = .006) and the short-axis view on the right of 7.4 ± 0.40 mm versus the short-axis view on the left of 6.1 ± 0.26 mm (P = .036). Supraspinatus tendon thickness for left-handed pitchers in the long-axis view on the left side showed a mean value of 7.5 ± 0.59 mm versus the long-axis view on the right side of 5.9 ± 0.56 mm (P = .137) and the short-axis view on the left of 6.5 ± 0.45 mm versus the short-axis view on the right of 6.5 ± 0.68 mm (P = .999). A database of normal values for supraspinatus tendon thickness in collegiate baseball pitchers has been developed. The results are consistent with expectations when the dominant side is compared with the nondominant side for right-handed pitchers with increased tendon thickness noted on the dominant side. There was no side-to-side difference found in left-hand dominant pitchers.