RADIOLOGICAL EVALUATION ON ALLOGRAFTS RECONSTRUCTION IN ACETABULUM WITH REINFORCEMENT RING IN REVISION TOTAL HIP REPLACEMENT

Abstract

Management of severe acetabular bone loss at the time of revision total hip replacements (THR) remains has been one of the greater challenges for hip surgeon. Recently, many methods of acetabular reconstruction have been described and various materials are used for supplement of the bone stock deficiency in acetabular revision THR. The purpose of this study was to evaluate the midterm results of the using support ring with bone allografts in acetabular revision THR.

• From 1990 to 2005, forty-six acetabular revisions using supporting ring with bone allografts were performed at our institution. All patients were followed up for a minimum of three years with a mean follow-up of 7.5 years. Pre-operative radiological acetabular bone defects were assessed and classified by author’s classification (Itoman’s classification). Radiological analysis involved a general qualitative evaluation. The position of the acetabular reinforcement ring was measured on radiograms, taken immediately after revision surgery and again at the time of last follow-up. Using a MEM template, cranio-central migration and cup inclination angle were measured. Kaplan-Meier survivorship analysis was performed. The end point was revision because of mechanical loosening of the acetabular implant.

• We used thirty-six Ganz rings, six Müller rings, three Kerboull T-plate and two Burch-Schneider anti-protrusion cages. The acetabular bone defects were classified as: 10 hips Type B (central defect), 9 hips Type C (cranial defect), 27 hips Type D (cranial-central defect). Migration of acetabular component was defined as a change of > 5mm in the cranial or central direction of the cup or a change in the cup inclination angle of > 5° at the time of last follow-up. All the Eleven acetabular components which had defined as loose were Type D. One acetabular component was revised because of mechanical loosening, four were revised because of infection, and one was broken polyethylene liner. Kaplan-Meier survivorship of these reconstructions was 96.2 % at 10 years.

• Allograft reconstruction of acetabular bone defect in revision total hip replacement is beneficial procedure. The remaining pelvic bone is usually in poor condition, therefore, it is necessary to ensure primary fixation with the reinforcement ring with bone allografts.