Mid-Term Results of Total Hip Arthroplasty with the CementLess Spotorno (CLS) System

Abstract

Except for those reported by the designers, there are no published mid-term results of the use of the CementLess Spotorno (CLS) Total Hip Arthroplasty system. We present the results of (1) a ten to seventeen-year follow-up prospective cohort study of this system, and (2) retrospective analyses of factors influencing clinical and radiographic outcomes. We studied a series of 102 consecutive CLS arthroplasties with a minimal duration of follow-up of ten years. Indications for the procedures were osteoarthritis (n = 90), rheumatoid arthritis (n = 8), and femoral head osteonecrosis (n = 4). The Merle d'Aubigné-Postel score, polyethylene wear, and radiographic status were recorded at regular intervals. Survival analyses, repeated-measures analysis of variance, and a nested case-control study (with the cases having early revision due to aseptic cup loosening within ten years after the index procedure and the controls having no early cup revision) were used for evaluation. There were fourteen revisions, including nine due to aseptic cup loosening. The ten-year Kaplan-Meier survival rate was 92.2% (95% confidence interval [CI] = 86.9 to 97.5) with revision for any reason as the end point. The fifteen-year survival rate was 78.4% (95% CI = 63.9 to 92.9) with revision for any reason as the end point, 81.6% (95% CI = 66.7 to 96.5) with revision due to aseptic cup loosening as the end point, and 99.0% (95% CI = 97.0 to 100.0) with revision due to aseptic stem loosening as the end point. The average amount of polyethylene wear at the time of final follow-up was 1.92 mm (range, 0.6 to 4.3 mm). The wear rate in the cases was significantly higher than that in the controls (0.31 vs. 0.16 mm/yr, p < 0.001). Factors with a significant effect on polyethylene wear were age at surgery (a 0.3-mm increase per every ten years younger, p = 0.001) and a larger head component (an effect of 0.53 mm for the 32 vs. the 28-mm component; p < 0.0001). Male sex had an effect of -0.66 point (p = 0.07) on the final Merle d'Aubigné-Postel score. The results of this CLS system, particularly with regard to the femoral stem, are comparable with those with other reliable cementless systems. Nevertheless, the prevalence of aseptic acetabular cup loosening in the second decade after the operation demonstrates a potentially substantial problem with regard to long-term survival. A high polyethylene wear rate, male sex, a younger age at the time of surgery, and a 32-mm head component size are related to inferior clinical outcomes and a higher risk of implant revision.