Radiographic Progression of Osteoarthritis after Rotational Acetabular Osteotomy: Minimum 10-Year Follow-up Outcome According to the Tönnis Grade

Abstract

Background: Although satisfactory mid- to long-term results of rotational acetabular osteotomy for early osteoarthritis secondary to acetabular dysplasia have been reported, there is still controversy about the long-term effects of this surgery in more advanced osteoarthritis. The purpose of this study was to investigate the radiographic progression of osteoarthritic changes after rotational acetabular osteotomy in acetabular dysplasia according to the preoperative Tönnis grade and evaluate its effects after minimum 10-year follow-up.

Methods: We performed 71 consecutive rotational acetabular osteotomies in 64 patients with symptomatic acetabular dysplasia between November 1984 and April 2005. Of these, 46 hips (four hips with Tönnis grade 0, 30 with grade 1, and 12 with grade 2) whose clinical and radiographic findings were available after minimum 10-year follow-up were evaluated in this study. The mean age at the time of surgery was 39.0 years (range, 18 to 62 years) and the average follow-up duration was 17.3 years (range, 10.0 to 27.7 years). Clinical and radiographic evaluations were performed according to the preoperative Tönnis grade.

Results: The average Harris hip score improved from 71.8 (range, 58 to 89) to 85.1 (range, 62 to 98). The radiographic parameters also improved in all Tönnis grades after the index surgery. Although the improvement of radiographic parameters was not different between preoperative Tönnis grades, the incidence of osteoarthritic progression was significantly different between grades (zero in Tönnis grade 0, four in Tönnis grade 1, and 10 in Tönnis grade 2; p < 0.001). The mean age at the time of surgery was also significantly older in osteoarthritic progression patients (p < 0.002). Kaplan-Meier survivorship analysis, with radiographic progression of osteoarthritis as the endpoint, predicted a 10-year survival rate of 100% in Tönnis grade 0, 85.7% in Tönnis grade 1, and 14.3% in Tönnis grade 2 (p < 0.001).

Conclusions: The outcome of rotational acetabular osteotomy in most hips with Tönnis grade 0 and 1 was satisfactory after an average of 17 years of follow-up. The incidence of osteoarthritic progression was higher in Tönnis grade 2 and older age. Our results support that early joint preserving procedure is essential in the case of symptomatic dysplastic hips.

Keywords: Acetabular dysplasia; Hip; Osteoarthritis; Rotational acetabular osteotomy.

Fig. 1. The flow diagram shows how the final study cohort was determined based on inclusion and exclusion criteria. RAO: rotational acetabular osteotomy, FU: follow-up.

Fig. 2. Radiographic parameters for evaluation of the hip. A: Center-edge angle. B: Acetabular roof angle. The head lateralization index is calculated using the distance between the teardrop and the center of the femoral head (a) divided by the half value of the inter-teardrop distance (b).

Fig. 3. Anteroposterior radiographs of the right hip joint in a 47-year-old male. (A) The preoperative radiograph shows mild acetabular dysplasia with no sign of degenerative change (Tönnis grade 0). (B) The postoperative radiograph shows improvement of acetabular coverage over the femoral head. Note that the osteotomized fragment and grafted bone were fixed with three Kirschner wires. (C) The Radiograph obtained 26 years after rotational acetabular osteotomy shows maintenance of good coverage and no progression of osteoarthritis.

Fig. 4. Anteroposterior radiographs of the left hip joint in a 47-year-old female. (A) The preoperative radiograph shows moderate joint space narrowing with subchondral cyst in the femoral head (Tönnis grade 2). (B) The postoperative radiograph shows improvement of acetabular coverage over the femoral head. (C) The postoperative radiograph obtained 7 years after rotational acetabular osteotomy shows progression of osteoarthritis. (D) Total hip arthroplasty was performed 7.5 years after the index surgery due to progressive osteoarthritis.

Fig. 5. The Kaplan-Meier survivorship analysis demonstrates the cumulative probability of osteoarthritic progression according to the Tönnis grade.