High incidence of posterior glenoid dysplasia of the shoulder in young baseball players.

Background: Rounding of the posterior glenoid rim is observed in young throwing athletes with internal shoulder impingement and is considered developmental dysplasia of the glenoid. The aim of our study was to determine the incidence rate of dysplastic changes of the glenoid within a group of 92 young baseball players.

Methods: The study group included 92 male baseball players, with a mean age of 14.63 years. Of these patients, 30 were diagnosed with Little Leaguer's shoulder and 62 with a painful baseball-throwing shoulder with no abnormal findings on x-ray. The posterior glenoid rim of the affected shoulder was compared with the contralateral nonpainful shoulder, with the 2 following outcomes measured on radiographs obtained using the modified Bernageau imaging method: the distance between the anterior and posterior glenoid rims and the presence or absence of dysplasia of the posterior glenoid rim.

Results: The mean distance between the anterior and posterior glenoid rims was significantly shorter in the painful shoulders (mean, 26 mm) than in the nonpainful shoulders (mean, 29 mm; P < .0001). Dysplasia of the posterior glenoid rim was identified in 89 painful shoulders (96.7%), with 9 cases (9.7%) identified on the unaffected contralateral side (P < .001). The presence of dysplasia was not correlated with the age at which baseball playing began.

Conclusion: The incidence of dysplasia of the posterior glenoid rim is high (96.7%) among young baseball players with a painful shoulder. The identified dysplasia may be related to impaired development of the inferior peripheral secondary glenoid ossification center due to repetitive throwing.