Abstract
Purpose: Double-tapered polished cemented femoral stems have demonstrated excellent long-term clinical results, but subsidence with cement mantle fracture, distal stress transfer and proximal stress shielding persist as problems. Adding a third taper from broad lateral to narrow medial purportedly reduces subsidence and improves proximal bone loading and preservation. We report our independent experience with a triple-tapered collarless polished cemented stem.
Methods: Between May 1999 and July 2001, 66 C-Stems (DePuy, Warsaw, IN, USA) were implanted in 45 females and 15 males, with a mean age of 67 years (R 35–86) and mean weight of 77 Kg (R 42–117). Diagnoses were OA in 62, RA in 1, AVN in 2 and fracture in 1. Average follow-up was 58 months (R 45–71).
Results: Harris hip scores improved from a mean of 43 (R17–100) to 84 (R 10–100). SF36 and WOMAC scores improved similarly. Six hips dislocated, but there were no reoperations. Subsidence was less than 1 mm in all cases. There was no radiographic stress shielding. Bone quality was maintained, especially in the critical medial calcar region, with positive bone remodeling along radial stress lines and improvement over time of some bone-cement interfaces.
Conclusions: The C-Stem, a triple-tapered collarless polished cemented stem, engages the surrounding cement mantle in an axially stable manner, minimizing subsidence to within the creep tolerances of cement. The radial stresses so generated favorably load the proximal bone, stimulating positive bone remodeling and eliminating stress-shielding. The clinical results at short to mid-term follow-up in this non-designer series are outstanding.
The abstracts were prepared by Orah Naor, IOA Co-ordinator and Secretary. Correspondence should be addressed to Israel Orthopaedic Association, PO Box 7845, Haifa 31074, Israel.
