Intra-acetabular localisation of an osteochondroma causing subluxation of the hip joint

INTRODUCTION: Intra-acetabular localisation of an osteochondroma causing subluxation of the hip joint is a rare entity in children suffering from multiple hereditary exostoses. In literature only 6 operatively treated cases have been reported. CASE: We add the case of an 8-year-old boy with an intraarticular exostosis of the left acetabulum causing subluxation of the hip. Using an anterolateral approach to the hip joint this exostosis was removed surgically together with some extraarticular exostoses of the proximal femur. The hip could be re-centered in combination with an additional varus derotation osteotomy of the proximal femur. Intraoperatively the femoral head was only subluxated to minimise the risk of avascular necrosis. After a follow-up of two years the patient has complete remission of symptoms and there is no evidence of avascular necrosis radiologically with good remodelling of the left hip. CONCLUSION: The operative treatment of an intraarticular exostosis of the hip joint is a difficult and risky surgical procedure. The reported open surgical procedure allowed resection of the intraarticular exostosis in combination with therapy of additional pathologies of the proximal femur.