Early MRI and intraoperative findings in rapidly destructive osteoarthritis of the hip: A case report

• Magnetic resonance imaging of our rapidly destructive hip osteoarthritis case showed a bone-marrow edema pattern not only in the femoral head but also in the acetabulum.
• The concentration of stress on the subchondral bone due to inversion of the acetabular labrum may lead to fracture of the femoral head and acetabulum beneath the cartilage.
• Inversion of the acetabular labrum may be a mechanism of rapidly destructive hip OA.

IntroductionThe pathophysiology of rapidly destructive hip osteoarthritis (OA) of the hip is still unclear. Also, there have been only few reports on the initial stage of the disease. We report a case of an initial-stage rapidly destructive hip OA, documented by magnetic resonance imaging and intraoperative findings.Presentation of caseA 77-year-old woman reported left hip pain without any antecedent trauma. Initial radiographs showed no obvious abnormality. After 4 months of conservative therapy, radiographs showed progressive joint-space narrowing and T1-weighted magnetic resonance images revealed a bone-marrow edema pattern not only on the femoral head but also on the lateral side of the acetabulum. Then during total hip arthroplasty, we found extensive inversion of the anterosuperior portion of the acetabular labrum, and the location was mostly consistent with the bone-marrow edema lesions in the femoral head and acetabulum.DiscussionSeveral theories for the etiology of rapidly destructive hip OA have been proposed, including idiopathic chondrolysis, abnormal immunoreaction, intra-articular deposition of hydroxyapatite crystals, and subchondral insufficiency fracture. One of the reasons rapidly destructive hip OA is still considered idiopathic is the lack of reports regarding the initial stage of the disease. Our report is the first to demonstrate magnetic resonance imaging for initial-stage disease with intraoperative findings before collapse of the femoral head.ConclusionInversion of the acetabular labrum may be a mechanism of rapidly destructive hip OA.