Preliminary Results of Uncemented Metal on Metal Total Hip Replacement Arthroplasty

Choy, Won Sik; Lee, Kwang Won; Kim, Whoan Jeang; Kim, Ha Yong; Kim, Young Wan; Hwang, In Sung; Hwang, In Sik

Abstract

Particulate wear debris(polyethylene, polymethylmethacrylate and metal particles, or combination of these) can initiate aseptic loosening. To eliminate polyethylene debris and reduce the total amount of wear, metal on metal bearings(Metasul) which were made of a wrought Co-28Cr-6Mo-0.2C alloy, were introduced. From May 1994 total hip replacements using a Metasul metal on metal articulation were performed by the authors. 34 patients with 40 hips with minimum follow-ups during 24 months were analysed in this study. The mean follow up period was 31 months(ranging from 24 to 47 months). We used Armor cups and standard cups as acetabular comporients and SL stems, CLS stems and cone stems as femoral components. Preoperative average Harris hip score of 48 points became postoperatively 93(from minimum 81 to maximum 100). And there were slight and occasional thigh pains in 2 cases(5%). There were no revisions for the early aseptic loosening of femoral stems or stem failures. Radiologic evaluation which revealed mild calcar atrophy was developed in 33 cases(82.5%), revealing cortical hypertrophy in 10 cases(25%). Osteolysis was not noted around the prosthetic stem nor around the cup. Radiolucent lines were found in 9 cases of femoral components(22.5%) and in 1 case of acetabular component(2.5%) and subsidence of more than 3mm in 1 case of femoral components(2.5%) were also found. There was 1 case of definitive loosening of acetabular component(2.5%). These also showed that endosteal bone formation adjacent to femoral prosthesis was developed in 22 cases(55%) but no distal pedestal and stem shift occurred. The short-term but satisfactory results of the contemporary metal on metal articulation investigated in this study were encouraging and warrant continued study.