Over a period of eight years, we implanted a total of 76 cementless hip prostheses in patients with rheumatoid arthritis. The clinical results of 47 patients (70 hips) increased from a mean Harris Hip Score of 33 to 85 after an average of 49 months (range 1-11 years). One threaded cup has had to be revised because of loosening, and one stem because of femoral fracture. At the latest follow-up, 88% of Hofer-Imhof threaded cups had complete bone ingrowth (Type 0); 10% had near-complete bone ingrowth with minimal radiolucency in one third of the bone contact area (Type 1), and 2% had radiolucency in two thirds of the bone contact area (Type 2). Hemispherical push-in cups showed significantly more radiolucency around the cup. For the stems (Uni, Zweymüller SL), 83% showed no radiolucency (Type 0); 17% had radiolucency only very proximally (Type 1). Minor remodelling (Type 1) occurred in 60% of the femoral shafts; 30% had moderate femoral density loss (Type 2), and 10% had severe bone loss and cortical thinning (Type 3). There was no correlation between marked shaft atrophy and clinical symptoms. With regard to radiolucency and remodelling, there was no significant difference between the two types of stem used. Cementless hip arthroplasty using titanium implants has an excellent outcome in the medium term.

Permanent secondary stability of the uncemented femoral stem of hip prostheses can only be achieved once primary rotational and axial stability has been ensured. Rotational stability means that the stem is resistant to the articular forces that induce rotation around the implant's longitudinal axis. The 10-year survival rates of two uncemented conical shaped stems with decisively different proximal shapes were significantly different (Schenker SK 63.9%, Zweymüller SL 97.0%). The shapes were analyzed biomechanically by testing rotational stability in a silicone model. A reduction in the mediolateral height of the metaphyseal part by one-third led to a 20% smaller angle of ascent (P < 0.01), which indicated lower resistance. The proximally broader (mediolateral) prosthesis therefore proved to have better rotational stability. The study confirms that aseptic stem loosening is attributable to the design of the proximal part of the prosthesis.

We have reviewed 142 Miller-Galante I (MG I) total knee arthroplasties (TKAs) with a follow-up of 56 months, and compared these with the outcome of 219 Miller-Galante II (MG II) TKAs with a follow-up of 36 months. In the MG II TKAs we found markedly lower revision rates, higher postoperative Hospital for Special Surgery (HSS) scores, less retropatellar pain and better patellar centring without patellar resurfacing. The higher revision rate in MG I TKAs was mainly due to the need to revise the metal-backed patellae.

Between January 1986 and December 1988, we implanted 220 conical-shaped Zweymueller threaded cups in 202 patients whose average age was 65 (33-83) years. The average thickness of the polyethylene (PE) insert was 8.0 (5.4-11.9) mm. In 142 cases, the corresponding femoral head was a 32 mm Al2O3 head. We followed 157 patients for a mean of 9.2 (1-16) years. Nine cups were revised and ten PE inserts replaced after an average of 11.9 (10-13.3) years. With cup revision alone considered as failure, the survival rate after 13 years was 89%. When both cup and insert revisions were considered failures, the survival rate decreased to 72% after 13 years. Patients younger than 60 years had a significantly higher rate of insert revision. Cup size 55 showed significantly more revisions in comparison to larger sizes. Using Cox regression model, neither gender, body mass index, nor material were risks factors leading to cup revision.

In a randomized, parallel group study, we evaluated the efficacy of a 4-day versus an 8-day course of indomethacin (50 mg, 3 times per day), given as prophylaxis against heterotopic ossification after cementless total hip arthroplasty in 209 patients with arthrosis. Patients receiving the prophylaxis for 8 days had less (p = 0.03) severe heterotopic bone formation.