TKA patients have increased mortality over the long-term, despite better initial survivorship

Researchers found an inverse relationship between age and mortality, with younger patients having increased mortality.

Total knee arthroplasty patients initially have a higher survivorship than the general population but, after about 12 years, mortality increases and survivorship becomes significantly lower, according to a study by researchers in Sweden.

Otto Robertsson, MD, PhD, and colleagues at Lund University Hospital, reviewed data from the Swedish Arthroplasty Register for 65,515 patients who underwent total knee arthroplasty (TKA) between 1975 and 2003 and compared their long-term mortality with the general, normal population.

The researchers also reviewed data on causes of death for a subset of 57,979 patients treated between 1980 and 2002, "because this information was only available for this period," the authors wrote.

Both groups had a mean age of 71 years at the time of surgery, according to the study, published in the British edition of the Journal of Bone and Joint Surgery.

Overall, the 65,515 total patients had a total follow-up of 431,139 person-years. The researchers found that, overall, TKA patients initially had a higher survival rate than expected. However, after approximately 12 years, mortality rates increased and survival became lower than expected.

The subgroup of 57,979 patients had a total follow-up of 382,427 person-years. "Because of the progressive increase in the number of operations per year and because most operations are performed on elderly patients, only a minority of 11,741 (20.3%) had a follow-up exceeding 10 years," the authors wrote.

"Therefore the overall mortality and the cause-specific mortality in terms of standardized mortality ratios indicated a generally increased longevity for the study population," they wrote.

However, the researchers found an inverse relationship between age and mortality. "Patients younger than 55 years ... had a statistically significant increase in total mortality, while patients older than 65 years had a statistically significant decrease," the authors wrote.

Circulatory system diseases represented the major causes of death among patients younger than 55 years, while patients aged 55 years and older had a significantly reduced mortality from most causes, the authors noted.

"Further analysis showed that the increased long-term mortality primarily reflected an increased mortality in younger age groups rather than an increased mortality among all patients after longer follow-up. The longer the follow-up was, the greater the proportion of patients operated on at a young age," they wrote.

The authors noted that the increased cardiovascular mortality observed among younger patients needs further investigation to determine whether it could be related to osteoarthritis or its treatment.

"However, we feel that the observation that [TKA] under the age of 50 years for osteoarthritis is linked to an increased mortality should be a reason for increased general awareness of health problems among these patients," they wrote.

For more information:
Robertsson O, Stefánsdóttir, A, Lidgren L, Ranstam J. Increased long-term mortality in patients less than 55 years old who have undergone knee replacement for osteoarthritis. J Bone Joint Surg Br. 2007;89-B:599-603.