The number of patients with total hip replacements (THRs) and total knee replacements (TKRs) has increased. The materials which prostheses are made of, release particles with possible carcinogenic effect. The purpose was to investigate the influence of the implant itself and its specific features ─ the bearing surface and the material of the stem of THRs itself, and the combination of the material of femoral and tibial components of TKRs, and finally the use of bone cement ─ on cancer incidence.
In the retrospective cohort study we identified 11.230 patients with total hip and knee replacements (THKRs), performed at the Valdoltra Orthopaedic Hospital from September 1st 1997 to December 31st 2009. The patient data were linked to the national cancer and population registries. The standardized incidence ratios (SIR) and the Poisson regression relative risks (RR) were calculated for all and specific cancers.
The general cancer risk in our cohort was comparable to the population risk. The united cohorts showed even lower risk. In comparison with the whole population the risks of prostate cancer and of kidney cancer were higher in the THRs cohort. In the same cohort there were lower risks of hematopoietic and lymphatic tumors, and the risks of gastrointestinal and lung cancers. The risk for all cancers combined as well as for the prostate and skin cancers, shown by Poisson analysis, was higher in the metal-on-metal (MoM) group compared to nonMoM group. The risk of kidney cancer was higher in TKRs cohort. However, there was a lower risk of gastrointestinal and lung cancers. The risk of prostate cancer was statistically significantly higher in cemented TKRs. The Poisson analysis did not show significant differences between TKRs features.
The risk of prostate, kidney and central nervous system cancers was higher in the united THKRs cohort. In this group, there were lower risks of hematopoietic and lymphatic tumors, and the risks of gastrointestinal, lung, pancreatic and skin cancers. The risk for all cancers combined as well as for lung and skin, shown by Poisson analysis, was lower in patients with only TKRs. The Poisson analysis did not show significant differences between patients with both, THR and TKR, and those with only THRs.
We found a positive association between metal-on-metal bearings of the THRs, and specific cancers. That is why the orthopedic surgeon should thoroughly reconsider the decision of implanting the THR with this kind of bearing couple. In this study, we also confirmed that the Valdoltra Arthroplasty Registry can be an effective and professional template for the proposed National Arthroplasty Registry of Slovenia.
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