Denying Obese Patients Knee Replacements Groundless

A new study has found that the benefits of total knee arthroplasty (TKA) are apparent in obese as well as non-obese patients, and there seems no justification for withholding surgery from obese patients solely on the grounds of their body mass index (BMI).

Researchers at the University of Southampton (United Kingdom) and the University of Bristol (United Kingdom) followed-up 325 patients from three English health districts approximately six years after TKA, along with 363 controls selected from the general population. Baseline data, collected by interview and examination, included age, sex, comorbidity, BMI, functional status, and preoperative radiographic severity of osteoarthritis. Functional status at follow-up was assessed by a postal questionnaire. Predictors of change in physical function were then analyzed by linear regression.

The results showed that at the beginning of the follow-up, the patients said they had significantly worse mobility than those in the comparison group, scoring an average of 20 compared with 89. However, by the end of the study, there was a stark contrast in mobility among those who had and had not had the surgery; mobility score rose three points among those who had had surgery, but fell 36 points among those who had not had a TKA. In addition, among those over the age of 75 who had not had the surgery, mobility score fell 40 points.

Improvement in physical function tended to be greater in patients with more severe radiological disease of the knee, and was less in those who reported pain at other joint sites at baseline. When the researchers restricted their analysis to participants who were obese, the improvements persisted, and BMI did not appear to be a significant factor in this improvement. The study was published in July 2008, issue of the Annals of the Rheumatic Diseases (ARD).

"The long term improvement in physical function that we observed in patients who have undergone knee replacement surgery is striking when set against the decline that occurred in the comparison group,” concluded lead author physiotherapist Janet Cushnaghan, MSC, MCSP, of the University of Southampton, and colleagues. "These benefits extend to patients who are obese and, provided appropriate selection criteria are applied with regard to fitness for surgery, there seems no justification for withholding knee replacement surgery from patients who are obese.”

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University of Southampton
University of Bristol