Relationship between the carrying angle, medial instability of the elbow, and general joint laxity in high school...

An increase in carrying angle (CA) on the throwing side has been reported in professional baseball pitchers. However, no reports have investigated high school baseball pitchers, and the associated factors remain unknown. This study aimed to examine the difference in the CA between the throwing and nonthrowing sides in high school baseball pitchers and to investigate the association between the CA and medial instability of the elbow and general joint laxity (GJL).

We surveyed 216 high school baseball pitchers who underwent medical checkups during the 2023-24 off-season. All of them completed a self-administered questionnaire, including items associated with throwing-related elbow joint pain (caused directly by throwing and resulting in participation loss of at least one week), baseball playing history, and a self-satisfaction score (1-100) for pitching performance during the season. A physical examination was performed, which included the measurement of the CA and assessment of GJL using the Beighton score. In addition, the medial joint space (MJS) of the elbow was measured by ultrasound under rest and gravity stress.

All participants were male, with a mean age of 16.5 (±0.7) years. The mean baseball playing history was 8.5 (±2.0) years. The CA on the throwing side was significantly greater than that on the nonthrowing side (12.5 [±3.7]° vs. 11.8 [±3.8]°, P = .04). No clinical differences were found between the MJS on the throwing side and the MJS on the non-throwing side for at rest (3.6 [±0.7] mm vs. 3.5 [±0.6] mm, P = .04), gravity-stressed (4.2 [±0.7] mm vs. 3.8 [±0.6] mm, P < .001), and gap (0.5 [±0.4] mm vs. 0.3 [±0.3] mm, P < .001) measurements. There was no significant association between the CA, the MJS of the elbow, and the presence of GJL. Similarly, no association was found between CA and elbow pain.

There was a significant increase in the CA on the throwing side relative to the nonthrowing side in high school baseball pitchers. No significant association was found between the throwing-side CA and MJS, and the presence of general joint hypermobility and elbow disability in high school baseball pitchers.