Short- and medium-term results of the thrust plate prosthesis in patients with polyarthritis

The thrust plate prosthesis is an implant with metaphyseal fixation to the proximal femur, which leaves the diaphyseal bone untouched. Therefore, this implant is preferred in younger patients. It is dependent on good bone qua lity in the proximal femur Because the bone quality is reduced in patients with polyarthritis, this kind of endoprosthesis may have a higher failure r ate than conventional stemmed endoprostheses in these patients. Therefore, in patients with polyarthritis, even short- and medium-term results of the thrust plate prosthesis should be analyzed. In all, 47 thrust plate prosthe ses were implanted in 42 patients with polyarthritis (29 with rheumatoid ar thritis, 6 with juvenile chronic arthritis, and 7 with spondylarthritis) an d followed prospectively The average age at operation was 40.8 +/- 10.7 yea rs. Each patient was clinically and radiologically examined preoperatively, 3 and 6 months after the operation, and at the end of each postoperative y ear. The mean follow-up was 26.1 +/- 10.7 months. The clinical findings wer e evaluated using the Harris hip score. Radiologically, 8 different zones o f the thrust plate prosthesis were analyzed for radiolucencies. During the 1st year, the Harris hip score rose continuously from the preoperative aver age of 42.4 +/- 6.5 points to 78.8 +/- 10.3 points 3 months postoperatively , 82.3 +/- 9.8 points 6 months postoperatively, and 86.8 +/- 10.1 points 1 year after the operation. The subsequent examinations showed Harris hip sco re remained at the same level. Five patients (5 joints, 10.6%) had to under go a revision of the thrust plate prosthesis due to aseptic loosening in 3 and septic loosening in 2. Six prostheses (12.6%) showed radiolucencies, mo stly below the thrust plate in zones 1 and 2. Two of them were certainly ra diologically loose, which raised the failure rate to 7 of 47 (14.8%). The t hrust plate prosthesis improves function and alleviates pain in patients wi th polyarthritis to a satisfactory degree. Concerning the failure rate, thi s type seems to yield slightly worse results than cementless stemmed endopr ostheses in the some patient group. Due to the preservation of the diaphyse al bone of the femur and the possibility of an unproblematic change to a st emmed endoprosthesis, the thrust plate prosthesis can be recommended for yo unger patients with polyarthritis.