Acetabular reinforcement ring in primary total hip arthroplasty: a minimum 10-year follow-up

INTRODUCTION: We report the results of a titanium acetabular reinforcement ring with a hook (ARRH) in primary total hip arthroplasty (THA), which was introduced in 1987 and continues to be used routinely in our center. The favorable results of this device in arthroplasty for developmental dysplasia and difficult revisions motivated its use in primary THA. With this implant only minimal acetabular reaming is necessary, anatomic positioning is achieved by placing the hook around the teardrop and a homogenous base for cementing the polyethylene cup is provided. MATERIALS AND METHODS: Between April 1987 and December 1991, 241 THAs with insertion of an ARRH were performed in 178 unselected, consecutive patients (average age 58 years; range 30-84 years) with a secondary osteoarthrosis in 41% of the cases. RESULTS: At the time of the latest follow-up, 33 patients (39 hips) had died and 17 cases had been lost to follow-up. The median follow-up was 122 months with a minimum of 10 years. Eight hips had been revised, leaving 177 hips in 120 living patients without revision. Six cups were revised because of aseptic loosening. Two hips were revised for sepsis. The mean Merle d'Aubigné score for the remaining hips was 16 (range 7-18) at the latest follow-up. For aseptic loosening, the probability of survival of the cup was 0.97 (95% confidence interval, 0.94-0.99). However, analysis of radiographs implied loosening in seven other cups without clinical symptoms. CONCLUSIONS: The results of primary THA using an acetabular reinforcement ring parallel the excellent results of these implants often observed in difficult primary and revision arthroplasty at a minimum of 10 years. Survivorship is comparable to modern cementless implants. Medial migration that occurs with loosening of the acetabular component seems to be prevented with this implant. Radiographic loosening signs can exist without clinical symptoms.