Long-term results of total hip arthroplasty using Charnley Elite-Plus stem and the effect of stem geometry on radiographic distal femoral cortical hypertrophy.

Abstract

The Elite-Plus stem has two shape variations: roundback and flanged. The correlation between the radiographic results and stem geometry has not been previously investigated. The objective of this study was to evaluate the long-term primary total hip arthroplasty results using Elite-Plus stems, and the effect of stem geometry on radiographic distal femoral cortical hypertrophy. We retrospectively evaluated, radiographically, 156 patients (173 hips) who underwent total hip arthroplasty between April 1998 and November 2005, and were followed up for >5 years, postoperatively. Radiographic factors affecting distal femoral cortical hypertrophy were analysed using multivariable logistic regression analysis. The mean follow-up period was 11.6 (5-17.8) years. During follow-up, femoral components were revised in 7 hips; one was revised due to aseptic loosening. Another femoral component was loosened and waiting for revision. The 10- and 15-year survival rates for aseptic stem loosening were 100% and 98.1% (95% CI: 92.5-99.5), respectively. Distal femoral cortical hypertrophy occurred in 23 hips (14.8%), and more often with roundback type (34.1%) than with flanged type (7.2%). Distal femoral cortical hypertrophy was observed in 34.8% of hips with valgus alignment, 11.3% with neutral alignment, and 12.5% with varus alignment. Multivariable logistic regression analysis showed that roundback stem shape and valgus stem alignment significantly affected the occurrence of distal femoral cortical hypertrophy. The Elite-Plus stem has excellent long-term clinical and radiographic results in Japanese patients. The occurrence of distal femoral cortical hypertrophy significantly depends on the shape and alignment of Elite-Plus stems.