REVIEW OF PERFORMANCE AND PROBLEMS OF METASUL HIP SYSTEM

Abstract

We report the review of performance and problems of Metasul Hip System with metallic sliding face during mean time of 11 years or longer.

Subjects and methods: Twenty-three joints in 22 patients. 17 females and 5 males treated using cementless Metasul THA in our hospital from November of 1995 to April of 1998 were selected as subjects. The mean age at the time of surgery was 59 years, and disease included degenerative hip disease in 16 joints, femoral head necrosis in 5 joints, and rheumatoid arthritis in 2 joints. Mean follow-up period was 11 years and 3 months. We have investigated clinical results (JOA score), stem fixation by radiography (Engh), setting angle of socket, and presence or absence of osteolysis by CT, and the poor cases after surgery and problems were clarified.

Results: Clinical results (JOA score) were improved from preoperative mean of 41.3 points to mean of 89.3 points at the time of investigation. Stem fixation examination by radiography (Engh) for bone ingrown resulted in 95% in ingrown and 5% in ingrown suspension, showing excellent fixation. The abduction angle of the socket was 38.8±4.5 degrees, and the anteversion angle was 14.6±7.7 degrees, revealing that precise surgery was conducted. There were no joints which showed loosening in stem or socket, but CT imaging showed osteolysis in 5 joints (22%) in the stem side and 12 joints (52%) in the acetabular side. Dislocation in Poly Liner occurred in 4 cases which needed revision surgery with accumulated survival rate of 82.6.

Summary: When cementless Metasul Hip System was used, fixation of stem/metal shell was excellent, but there were problems in thickness and fixation of Poly Liner. Due to augmentation of activity, backside wear occurred, and osteolysis or dislocation of the liner was induced. THA System such as M2a which improves these defects using metallic liner may be promising hereafter.