Evaluation of articular cartilage following rotational acetabular osteotomy for hip dysplasia using T2 mapping MRI.

BACKGROUND: Rotational acetabular osteotomy (RAO) is one of the surgical treatments for acetabular dysplasia, and satisfactory results have been reported. We evaluated the postoperative changes of articular cartilage and whether the pre-operative condition of the articular cartilage influences the clinical results using T2 mapping MRI.

METHODS: We reviewed 31 hips with early stage osteoarthritis in 31 patients (mean age, 39.6 years), including three men and 28 women who underwent RAO for hip dysplasia. Clinical evaluations including Japanese Orthopedic Association (JOA) score and Japanese Orthopedic Association Hip Disease Evaluation Questionnaire (JHEQ), and radiographical evaluations on X-ray were performed. Longitudinal qualitative assessment of articular cartilage was also performed using 3.0-T MRI with T2 mapping technique preoperatively, 6 months, and at 1 and 2 years postoperatively.

RESULTS: There was no case with progression of osteoarthritis. The mean JOA score improved from 70.1 to 93.4 points, the mean postoperative JHEQ score was 68.8 points, and radiographical data also improved postoperatively. We found that the T2 values of the cartilage at both femoral head and acetabulum increased at 6 months on coronal and sagittal views. However, they significantly decreased 1 and 2 years postoperatively. The T2 values of the center to anterolateral region of acetabulum negatively correlated with postoperative JHEQ score, particularly in pain score.

CONCLUSIONS: This study suggests that biomechanical and anatomical changes could apparently cause decreased T2 values 1-2 years postoperatively compared with those preoperatively. Furthermore, preoperative T2 values of the acetabulum can be prognostic factors for the clinical results of RAO.