CBC Mathys and CLS Spotorno stems: similar in design, different in outcomes. A comparative study of clinical and radiological differences.

INTRODUCTION

Total hip arthroplasty (THA) is a highly successful orthopedic intervention, with non-cemented stems like the CLS Spotorno and CBC Mathys being widely used. While these stems share a similar tapered design, they may produce different clinical and radiological outcomes. This study aims to compare clinical outcomes (Merlé-D'Aubigné scale) and radiological results between the CBC (Mathys) stem and the CLS Spotorno stem, specifically evaluating cortical hypertrophy, radiolucency, stem subsidence, and implant survival.

MATERIALS AND METHODS

A retrospective 1:1 matched cohort study was conducted, including 344 THA patients (172 with CBC Mathys, 172 with CLS Spotorno) treated between 2010 and 2019. Radiological assessment included cortical hypertrophy, radiolucency, and stem subsidence using MEDICAD software. Clinical outcomes were evaluated via the Merlé-D'Aubigné scale. Stem survival was analyzed using Kaplan-Meier curves.

RESULTS

Baseline demographics were similar in both groups. Cortical hypertrophy occurred in 42.4% of the CBC Mathys group, significantly higher than the 4.6% in the CLS Spotorno group (p = 0.03). Radiolucencies were more frequent in the CBC Mathys group (55.2%) compared to CLS Spotorno (18.6%) (p = 0.03). No significant differences in stem subsidence were observed (p = 0.68). The average time of cortical hypertrophy appearance and radiolucency was 12.97 (SD: 15.51) and 13.48 (SD: 15.57) months, respectively. At final follow-up, four CBC Mathys stems were revised due to aseptic mobilization, resulting in a 97.6% survival rate, compared to 100% in the CLS Spotorno group (p = 0.182).

CONCLUSION

The CBC Mathys stem exhibited higher incidences of cortical hypertrophy and progressive radiolucency, suggesting biomechanical and tissue response differences compared to the CLS Spotorno stem. These radiological findings correlated with a slightly reduced survival rate for the CBC Mathys stem over six years, are already observable in many cases by the end of the first year, warranting further investigation into long-term clinical outcomes.