Ten-year mortality and revision after total knee arthroplasty in morbidly obese patients

Background — Although morbid obesity has been associated with early surgical complications after total knee arthroplasty (TKA), evidence of long-term outcomes is limited. We conducted a population-based study to determine the association between morbid obesity and 10-year survival and revision surgery in patients undergoing primary TKA.

Methods — A cohort study of 9817 patients aged 18-60 years treated with primary TKA from April 1, 2002 to March 31, 2007 was conducted using Ontario administrative health-care databases of universal health-care coverage. Patients were followed up for 10 years after TKA. Risk ratios (RRs) of mortality and TKA revision surgery in patients with body mass index > 45 kg/m² (morbidly obese patients) compared with body mass index ≤45 kg/m² (nonmorbidly obese) were estimated adjusting for age, sex, socioeconomic status, and comorbidities.

Results — About 10.2% (1001) of the cohort was morbidly obese. Morbidly obese patients were more likely to be female than nonmorbidly obese patients (82.5% vs 63.7%, P < .001) but otherwise similar in characteristics. Morbidly obese patients had higher 10-year risk of death than nonmorbidly obese patients (adjusted RR 1.50, 95% confidence interval 1.22-1.85). About 8.5% (832) of the patients had at least 1 revision procedure in the 10 years after TKA; revision rates did not differ by obesity (adjusted RR 1.09, 95% confidence interval 0.88-1.34).

Conclusion — Morbidly obese patients ≤60 years had a 50% higher 10-year risk of death but no difference in the risk of revision surgery. Results of this population-based study inform evidence-based perioperative counseling of morbidly obese patients considering TKA.