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Researchers identify factors impacting mortality rate after total knee replacement

ND Clement. J Bone Joint Surg Br. 2012. Doi: 10.1302/0301-620X.94B2.28114

Issue: April 2012

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Researchers in the United Kingdom have found that age, American Society of Anesthesiologists grade, body mass index and rheumatoid disease all impact mortality rates following total knee replacement, according to the results of this study.

The researchers studied 2,428 patients during a span of 10 years, collecting a cohort of 1,127 men and 1,301 women with a mean age of 69.3 years. According to the abstract, each patient was allocated a predicted life expectancy that the researchers based on patient age and gender.

Clement and the other researchers reported 223 deaths during the study period, representing an overall survivorship of 99% at the 1-year mark, 90% at the 5-year mark and 84% at the 10-year mark. Gender was not found to have an impact on survival rates, the authors found, but mortality rates were found to increase with increasing age, American Society of Anesthesiologists grade, smoking, body mass index and rheumatoid arthritis.

“Patient mortality after TKR is predicted by their demographics,” the authors wrote. “These could be used to assign an individual mortality risk after surgery.”

Increased mortality after total knee replacement is the statement in this study. However, when I look carefully into the data, I will question whether it is really the knee replacement that makes the difference. The survival rate after 1 year was reported to 99% for these 2,400 patients — but after 5 and 10 years, 90% and 84%, respectively. The authors found age, ASA, smoking, BMI above 20kg/m2 and rheumatoid arthritis all to correlate with increased mortality, predicting mortality in 114 patients — and actually losing 217 after 10 years.

However, all their listed risks factors can, by themselves, increase the risk of dying earlier — whether having joint replacement or not. As the first year survival rates are very high (99%), the reason for dying 5 years to 10 years after joint replacement seems very little related to the surgery — but much more to their factual circumstance with being elderly, smoking, having a high BMI and being in a generally poor medical condition (ASA).

— Per Kjaersgaard-Andersen, MD
Chief Medical Editor
Orthopaedics Today Europe