Acetabular epiphysis-labrum entrapment following traumatic anterior dislocation of the hip in children

Traumatic anterior dislocations of the hip during childhood are rare injuries. Although a concentric reduction can usually be achieved with closed techniques, open reduction is occasionally required. We recently treated two children, 10 and 13 years of age, with nonconcentric closed reductions following traumatic anterior dislocation sustained 6 weeks and 6 months previously, respectively. Preoperative evaluation revealed intraarticular entrapment of the acetabular epiphysis and its contiguous labrum as the cause of the nonconcentric reduction. This was confirmed at surgery. Although displacement of the acetabular epiphysis has not been previously described, it is probably a common source for cartilaginous and osteocartilaginous fragments that have been recognized at open reduction following both traumatic anterior and posterior hip dislocations in children. Damage to this secondary center of ossification does not appear to affect adversely further growth and development of the acetabulum.