THE CLS STEM IN PRIMARY THA. LONG-TERM RESULTS AND SURVIVORSHIP ANALYSIS OF A TAPERED, GRIT-BLASTED, PRESS-FIT FEMORAL PROSTHESIS.

Abstract

Background: This report presents the long term (over 20 years) experience with the use of a grit-blasted, press-fit femoral prosthesis.

Methods: The first 300 consecutive primary THA procedures using a collarless, three-dimensional tapered, straight, titanium alloy stem with a grit-blasted surface (performed in 299 patients) were evaluated up to twentytwo years. A cementless all-polyethylene socket in 80 percent of the cases, were used. Radiographic evaluation, performed by an independent observer using a zonal analysis method, included assessment of component migration, Engh’s implant-bone femoral fixation score, implant-bone demarcations, and periprosthetic osteolysis. The average duration of long-term radiographic follow-up was 12.6 years (range; 10 to 16 years).

Results: At last examination only five hips were lost to follow-up and 84 patients were deceased. The femoral revision rate was 7 percent (two hips for aseptic loosening, five hips for septic loosening, and twelve hips with osseointegrated stems for severe progressive femoral osteolysis) and the acetabular revision rate was 28% (revised for either socket migration or progressive peri-acetabular osteolysis or both). Survivorship, based on any revision (femoral or acetabular) was 89% at ten years and 65% at twenty years; survivorship of the femoral component was 95% at ten years and 89% at twenty years. The incidence of femoral periprosthetic osteolysis, was 47%, with 5% of distal endosteal osteolysis. Radiographic femoral implant-bone fixation was stable, bone-ongrowth in 97%; stable, fibrous-fixation in 1%.

Conclusions: The grit-blasted, press-fit, collarless, tapered femoral component continued to perform well clinically and radiographically up to twenty years of follow-up despite the challenging environment of peri-prosthetic osteolysis associated with the acetabular component design. This implant is still in use virtually without design modifications. This study demonstrates the durability of the results of the grit-blasted femoral component and indicates that such an implant offers a viable alternative for fixation without bone cement.