[Treatment of aseptic acetabular loosening by reconstruction combining bone graft and Müller ring. Actuarial analysis over 11 years].

INTRODUCTION: One reason for the limited longevity of total hip replacement is the progressive bone loss resulting from iterative loosenings of acetabular components. In the early 80's was developed an experience at our institution for revision surgery of aseptically failed cemented acetabular components using a Müller ring. At that time, this device was used in combination with structural grafts. This appeared to us to be the safest method to address severe acetabular destructions. We are now able to report long term results.

MATERIAL AND METHODS: We carried out a retrospective study on 81 cemented acetabular revision arthroplasties performed at our institution between 1981 and 1991. In all cases, there was a segmental or an important cavitary roof defect. Reconstruction of the acetabulum was performed using a superior structural bone graft combined with a Müller ring. Results are given with a mean follow up of 8 years (5-14 years), except in the survivor analysis, in which all patients were included.

RESULTS: There was 15 iterative aseptic loosenings of the acetabular component (in which 5 repeated revisions). Using iterative aseptic loosening of the acetabular component revised or not as an end point, the 10 year cumulative survival rate (CSR) was 0.72 +/- 0.14 and the 11 year CSR was 0.55 +/- 0.24. The position of the hip biomechanical center, the polyethylene thickness, or the type of the superior defect (segmental or cavitary) were not found to influence significantly roentgenographic results.

DISCUSSION: Reconstruction of severely destroyed acetabuli using this method gave satisfactory results within the first decade. However, the hip function could not be reliably maintained over 10 years. Mechanical failures were related to resorption of weight bearing structural bone grafts. Aseptic iterative loosenings are often moderately symptomatic and yearly roentgenographic controls are necessary to detect late migrations. The lack of long term follow up may result in major bone loss, which can impair the conditions of iterative acetabular reconstructions.