Missed adolescent acetabular apophyseal avulsion with late hip dislocation.

BACKGROUND: Chronic hip dislocation associated with acetabular apophyseal avulsion in adolescence is rare. Whilst superior acetabular rim fractures have a documented theoretical risk of hip instability, we have not found a case of chronic dislocation resulting from this.
METHODS: We report a case of a 12-year-old healthy boy who initially sustained a missed right acetabular apophyseal avulsion after falling from a quad bike. This was missed on the initial radiograph and a subsequent radiograph following weight bearing a few days later showed a hip dislocation that was also missed. Upon diagnosis at 6 weeks, he underwent open reduction but also required acetabuloplasty to stabilise the hip.
RESULTS: At 2 years follow-up, he was enjoying pain free swimming, cycling and walking. His Harris hip score was 87.
CONCLUSION: This case reinforces the need for recognition that in the patient presenting with knee or thigh pain, exclusion of hip pathology is required. It also explores the pitfalls of diagnosis associated with rare patterns of injury and the need for adequate investigations such as examination under anaesthetic, arthrography and MRI. The use of acetabuloplasty is shown to be a useful strategy for the unstable hip resulting from irreparable acetabular rim fracture.