Development of secondary ossification centres of the acromion in Japanese youth: a computed tomographic study

PURPOSE. To determine the age range when the secondary ossification centres of the acromion appear and fuse in Japanese youth using computed tomography (CT). METHODS. CT scans of 85 shoulders in 35 male and 14 female consecutive patients aged 6 to 20 (mean, 16) years were reviewed. No patient had pain or tenderness at the acromion. Appearance and fusion of the secondary ossification centres of the acromion were determined twice by an orthopaedist. A secondary ossification centre was considered to have appeared when a low-density line was noted at the juxta-epiphyseal area and to have fused when the line had disappeared. Intra-observer reliability was determined. RESULTS. The intra-observer reliability was 0.93. The secondary ossification centres of the acromion had appeared at around 10 years of age and had fused at around 15 years of age, with one exception. CONCLUSION. In these Japanese subjects, the secondary ossification centres of the acromion had appeared at around 10 years of age and had fused at 15 to 16 years.