Purpose: To compare the survivorship, at 15 years, of cemented versus cementless fixation of press-fit condylar primary total knee replacements.
Methods: A prospective randomised consecutive series of 501 primary knee replacements received either cemented (219 patients, 277 implants) or cementless (177 patients, 224 implants) fixation. All operations were performed either by, or under the direct supervision of, a single surgeon (PJG). Patients were followed up to establish the rate of implant survival. No patients were lost to follow up. Revision was defined as further surgery, irrespective of indication, that involved replacement of any of the three original components. Life table analysis was used to assess survival. Cox’s proportional hazards regression analysis was used to compare the cumulative survival rates for the two groups.
Results: Altogether 44 patients underwent revision surgery (24 cemented vs. 20 cementless). 11 cases were revised secondary to infection, 26 were revised due to aseptic loosening and 7 cases were revised for other reasons (instability, anterior knee pain, polyethylene wear, patellar malallignment). At time of analysis a further 7 had revision planned.
For cemented knees 15-year survival=80.7% (95%CI, 71.5–87.4), 10-year survival=91.7 (95%CI, 87.1–94.8). For cementless knees 15-year survival=75.3% (95% CI, 63.5–84.3), 10-year survival=93.3% (95%CI, 88.4–96.2). There was no difference between these two groups.
When comparing the covariates (operation, sex, age, diagnosis, side), there was no significant difference between operation type (Hazard ratio=0.83 (95%CI, 0.45–1.52) p=0.545), side of operation (HR=0.58 (95%CI, 0.32–1.05) p=0.072), age (HR=0.97 (95%CI, 0.93–1.01) p=0.097), diagnosis (OA vs. non OA, (HR=1.25 (95%CI,0.38–4.12) p=0.718). However, there was a significant gender difference (Males vs. Females (HR=2.48 (95%CI, 1.34–4.61) p=0.004).
The worst case scenario was calculated to include those patients that have also been listed for revision. Cemented 15-yr survival = 78.3%, (95%CI, 68.9–85.4), cementless 15-yr survival = 72.0%, (95%CI, 59.9–81.5).
Conclusion: This single surgeon series, with no loss to follow up, provides reliable data of the revision rates of the most commonly used total knee replacement. The survival of the press-fit condylar total knee replacement remains good at 15 years irrespective of the method of fixation. This information is useful for strategic health authorities when establishing future requirements for revision knee surgery.
