LONG TERM RESULTS OF 4,032 PRIMARY TOTAL HIP REPLACEMENTS FOR PRIMARY OSTEOARTHRITIS IN YOUNGER PATIENTS FROM THE FINNISH ARTHROPLASTY REGISTER

Abstract

Background: According to the mid-term results obtained from the previous registry-based studies, survival of cementless stems for aseptic loosening in younger patients with primary osteoarthritis has been better than the survival of cemented stems. However, it has not been clear if the endurance against aseptic loosening of cementless cups is comparable to that of cemented cups. The aim of the present study was to analyze population-based long-term survival rates of the cemented and cementless total hip replacements in patients under the age of fifty-five years with primary osteoarthritis in Finland.

Patients and Methods: Between 1980 and 2006, a total of 7310 primary total hip replacements performed for primary osteoarthritis in patients under the age of fifty-five years were entered in the Finnish Arthroplasty Registry. 4,032 of them fulfilled our inclusion criteria and were subjected to analysis. The implants included were classified in one of the three following groups: implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group #1); implants with a cementless, anatomic, proximally circumferentially porous-coated and/ or hydroxyapatite-coated stem with a porous-coated and/or hydroxyapatite-coated press-fit cup (cementless group #2); and a cemented stem combined with a cemented all-polyethylene cup (the cemented group).

Results: Cementless total hip replacements, as well as cementless stems and cups analyzed separately, had a significantly reduced risk of revision for aseptic loosening compared with cemented hip replacements. The 15-year survivorship of cementless stem groups for aseptic loosening was higher than that of cemented stems (89% and 90% vs. 72%). The 15-year survivorship of cementless press-fit porous-coated cups for aseptic loosening was higher than that of cemented cups (80% vs. 71%). When revision for any reason was the end point in survival analyses, however, there were no significant differences among the groups.

Conclusions: Both cementless stems and cementless cups have better resistance to aseptic loosening than cemented implants in long term follow-up in younger patients. Even if liner-exchange revisions are taken into account, the long-term survival of cementless total hip replacements is comparable to that of cemented implants.