Table 3.

Results of the Cox proportional hazards model

Variable (reference)	Hazard ratio*	95% CI
Bilateral operation (unilateral)	0.94	0.75–1.18
Cementless (cemented)	0.86	0.50–1.48
Hybrid (cemented)	1.21	0.89–1.63
Patellar resurfacing (no patellar resurfacing)	0.92	0.79–1.06
Antibiotic prophylaxis (no intravenous antibiotic prophylaxis)	0.78	0.49–1.23
Bone grafts (no bone grafts)	0.96	0.54–1.71
Femoral model, manufacturer [years when introductions in hospitals]
Duracon, Stryker [1998–2004] (reference model)	1.00
AGC V2, Biomet [1998–2004]	0.94	0.80–1.11
PFC Sigma, DePuy [1998, 1999, 2001–2004]	0.66	0.52–0.84
Nexgen® CR, Zimmer [1998–2004]	0.54	0.37–0.78
Arge, Implant Cast [1998–2002]	0.86	0.60–1.24
Nexgen LPS, Zimmer [1999–2004]	0.89	0.63–1.27
Maxim Primary, Biomet [1998–2000, 2002, 2004]	0.92	0.64–1.33
PFC Sigma Stabilized, DePuy [1998–2004]	0.68	0.42–1.09
Duracon Stabilizer Box, Stryker [1998–2004]	1.85	1.22–2.81
Genesis II, Smith & Nephew [1998–2004]	0.26	0.06–1.05
PFC, DePuy [1998]	0.89	0.40–2.02
Maxim PS, Smith & Nephew [1998, 2001, 2004]	1.47	0.72–3.02
AGC V2 Stabilized, Biomet [1998–2004]	1.25	0.53–2.97
Search Evolution, Aesculap AG [2001, 2002]	0.20	0.03–1.52
Duracon Modular TS, Stryker [1998–2004]	2.06	0.98–4.36
Search, Aesculap AG [1998]	2.51	1.20–5.24
Other models	0.94	0.59–1.52

* Adjusted with all factors listed in Table 1.