SATISFACTORY 20 YEARS RESULTS FOR CEMENTED PRIMARY HIP PROSTHESES IN THE NORWEGIAN ARTHROPLASTY REGISTER – BUT CONCERN IS RAISED OVER SOME OF THE NEWER IMPLANTS

Abstract

Background: Few studies have compared long-term survival for different types of cemented primary total hip arthroplasties, and prostheses are still used without adequate knowledge of their endurance.

Patients and Methods:We compared the 10 most used prosthesis brands cemented with Palacos or Simplex in primary THAs reported to the Norwegian Arthroplasty Register in 1987–2007, totaling 62305 operations. Survival analyses with revision as endpoint (any cause or aseptic loosening) were performed with Kaplan-Meier and multiple Cox regression analyses. Risk estimates were established for different time intervals after the primary operation (0–5 years, 6–10 years, > 10 years).

Results: At 20 years, the Kaplan-Meier estimated revision per cent with any revision as endpoint was 15 % (95 % CI: 14–17), and with revision due to aseptic loosening as endpoint, 11 % (9.8–13). The adjusted revision percentage for aseptic loosening at 10 years could be established for 7 of the prostheses and varied from 0.4 % (0.0–0.8) for the Lubinus SP (I, II) to 6.6 % (4.1–9.0) for the Reflection all poly/Spectron-EF (cup/stem) combination. Only Charnley, Exeter, Titan and Spectron/ITH could be compared beyond 10 years. While long-term results were similar for these stems, Exeter (RRcup = 1.7, p = 0.001) and Spectron (RRcup = 2.4, p = 0.001) cups had higher revision rates due to aseptic loosening than Charnley cups. Comparing Charnley with prostheses with shorter follow-up, we observed an increased revision risk for aseptic loosening in the 6–10 year time interval also for Reflection all poly/Spectron-EF (RRcup = 5.5, p< 0.001; RRstem = 2.4, p< 0.001), Elite/Titan (RRcup = 7.5, p< 0.001; RRstem = 5.4, p< 0.001) and for the cup in the Reflection all poly/ITH combination (RRcup = 2.1, p = 0.03). Only the Lubinus SP had statistically significant better results than the Charnley prosthesis (RRcup = 0.2, p = 0.09; RRstem = 0.1, p = 0.01). Since several of the prostheses were introduced in recent years, analyses were also performed on operations from 1998 and onwards. Except for Lubinus SP that now had results similar to that of Charnley, differences in survivorship as compared with Charnley were enhanced. This was mainly due to a marked improvement in results for the Charnley prosthesis.

Conclusion: We observed in the Norwegian Arthroplasty Register clinically important differences among cemented prosthesis brands and identified inferior results for previously undocumented prostheses. Overall results at 20 years were, however, satisfactory according to international standards.