Abstract
Background
Aseptic loosening is rare with most cementless tapered stems in primary total hip arthroplasty (THA), however different factors can modify results. We ask if the shape and technique of three current different femoral components affects the clinical and radiological outcome after a minimum follow-up of ten years.
Methods
889 cementless tapered stems implanted from 1999 to 2007 were prospectively followed. Group 1 (273 hips) shared a conical shape and a porous-coated surface, group 2 (286 hips) a conical splined shape and group 3 (330 hips) a rectangular stem. Clinical outcome and anteroposterior and sagittal radiographic analysis were compared. Femoral type, stem position, femoral canal filling at three levels and the possible appearance of loosening and bone remodelling changes were assessed.
Results
No thigh pain was reported in unrevised patients. Mean Harris Hip score was lower for patients in group 3 for pain and function at 6 months, two years and at latest follow-up. The survival rate of not having revision of the stem for any cause was 98.5% (95% CI 98.8–100) for group 1 at 12 years, 99.3 % ((95% Confidence Intervals (CI) 97.9–100) for group 2 at 16 years and 97.7% (95% (CI) 94–100) for group 3 at 14 years, and (log rank= 0.109). Thirteen stems from the latter were revised for aseptic loosening. No revision for aseptic loosening was found in the other designs. After controlling all confounding factors, the risk for aseptic loosening in group 3 was related to a lower femoral canal filling (p=0.039, Hazard Ratio (HR):0.918, 95% Confidence Interval (CI):0.846–0.996) and a stem position outside neutral limits in the sagittal alignment (p=0.048, HR:3.581, 95% CI:1.010–12.696).
Conclusions
Conical tapered cementless stems are more reliable than rectangular straight designs in primary THA after ten years
