Results Covering 20 Years Use of the Cement-free Zweymuller Alloclassic Total Endoprosthesis of the Hip Joint

PURPOSE OF THE STUDY From an initial group of 206 hips in 190 patients we carried out a retrospective clinical and radiological control of 74 hips in 72 patients covering a period of 20 years. MATERIAL AND METHOD Indications in 74 operated hips evidenced 48 x (64,9 %) primary and 26 x (35,1 %) secondary coxarthrosis. The average age at the time of operation was 53 years (37 years 68 years). All 72 patients with 74 hips received cement-free self-cutting Alloclassic screw cups of pure Titanium together with a cement-free square Alloclassic stem consisting of Titan-Aluminium-Niob alloy according to Zweymuller. Regarding the technique of operation we used the approach after Watson-Jones in the supine position. As prophylaxis against thrombosis 40 % of the patients received derivates of heparine and 60 % had anticoagulant therapy with cumarine. Prophylaxis against heterotopic ossifications were not carried out at this juncture in our department. RESULTS After an average post-operational examination lapse of 20 years we were able to examine 72 patients (37,9 %) with 74 hips (35,9 %) clinically and radiologically. Further classification of the 72 patients records 47 females and 25 males. The average age at the time of operation was 53 years and at the time of post-operational check-up to 74 years. For the clinical post-operational check-up (n = 74) we used the Harris Hip Score. Further evaluation shows 12 x (16,2 %) excellent results, 26 x (35,1 %) good and 29 x (39,2%) fair results. In 7 patients (9,5 %) we had to observe poor results because of multimorbidity, although also in these cases stability of TEP had been achieved. The radiological post-operational check-up of the 74 stable hips (35,9 A) shows an average excentric position of the head of 1,4 mm (0 mm up until 4 mm) compared with 1 mm after 10 years. Over an average of about 20 years we carried out an exchange of the inlay and the head because of excentric position of the head, which correlates to a rate of reoperation of 6,8 %. DISCUSION In 2000 and 2001 we published our 10 year results with cement-free Alloclassic screw cup and cement-free stem in 133 hips in 123 patients and compared our findings with those of other authors. After 10 years we saw only 3 % complications with cups and an overall re-operation rate of 6,7 %. The 20-year-results show in all cases stable components of both cups and stems. 5 patients (6,8 %) had to undergo re-operation with an exchange of inlay and head, whereby the components of the prosthesis themselves turned out to be stable. An average polyethylene abrasion of 1 mm after 10 years compares with a value of abrasion of 1,4 mm after 20 years. The 6,8 % rate of re-operation after 20 years indicates the excellent results of the use of cement-free Alloclassic total endoprosthesis system of the hip according to Zweymuller. CONCLUSIONS The biocompatible qualities of modern prosthesis material lead to a quicker and optimal bony incorporation of the prosthesis components. The excellent 20-year-results show a broad indicative spectrum, component stability of the prosthesis in all patients and therefore encourage the further use of cement-free hip implants in the future.