Long-term Results of Hip and Knee Arthroplasties A Review of Population-based Results Obtained from the Finnish Arthroplasty Registry

Background: We reviewed the published papers reporting on long-term results of hip and knee arthroplasties based on the Finnish Arthroplasty Registry.

Methods: All articles published in international peer-reviewed orthopaedic journals were analyzed and results of those studies were summarized in this review article.

Results: Cementless total hip replacements, as well as cementless stems and cups analyzed separately, showed a significantly reduced risk of revision for aseptic loosening as compared to the cemented hip replacements in osteoarthritic patients aged less than 74 years. When all revisions were taken into account, however, there were no significant differences between the groups. In patients aged less than 64 years, none of the cemented or cementless total hip replacement designs studied yielded an excellent (>90%) 10-year survivorship. In patients aged 75 years and over, there were no significant differences between different total hip replacement concepts; all of them showed >90% survivorship at 10 years. In younger (<55 years) patients with rheumatoid arthritis, all-poly cementless cups showed a significantly better survivorship than modular cementless cups. On the knee side, unicondylar knee arthroplasties (UKAs) had a 60% and TKAs an 80% survival rate at 15 years with any revision as the end point. The overall survival of UKAs was significantly worse than that of TKAs (p<0.001). All three UKA designs studied had significantly poorer overall survival than the corresponding TKA designs from the same manufacturers. Of the UKA designs, the Oxford meniscal bearing had the highest survivorship of 81% at 10 years, while several TKA designs showed a 10-year survivorship exceeding 90%. In a theoretical cost-benefit analysis, the cost saved by lower implant prices and shorter hospital stay associated with UKA as compared to TKA did not cover the costs of the extra revisions.

Conclusions: Cementless total hip replacements have comparable long-term survivorship with cemented replacements in all age groups. In patients aged less than 74 years, cementless stems seem to produce better long-term survivorship than cemented ones. In patients aged 75 years and over, there were no significant differences in the results. Multiple wear-related revisions of the cementless cups in the present study indicate that excessive polyethylene wear is a significant clinical problem with modular cementless cups in all age groups. At a nation-wide level, UKA had a significantly poorer long-term survival than TKA. What is more, UKA did not have even a theoretical cost benefit over TKA in our study. Based on these results, we can not recommend the wide-spread use of UKA in treatment of unicompartmental OA of the knee.