The effect of obesity on revision total knee arthroplasty: a retrospective cohort study

Obesity has been linked to higher rates of postoperative complications, delayed wound healing, reoperation, and re-revision rate following revision total knee arthroplasty (RTKA). This study examined the impact of obesity across various weight classes on RTKA outcomes: healthy weight (body mass index [BMI] < 25); overweight (BMI 25 to 29.9); class I obesity (BMI 30 to 34.9); class II obesity (BMI 35 to 39.9); class III, type 1 obesity (BMI 40 to 44.9); class III, type 2 obesity (BMI 45 to 49.9); and severe class III obesity (BMI ≥ 50).

We retrospectively reviewed an institutional database of patients who underwent RTKA over a period of 15 years. Data on demographics, re-revision rate, RTKA survivorship, postoperative complications, mortality rate, readmissions, 90-day costs, and functional outcomes were collected. Comparisons among BMI groups were made with Kruskal-Wallis tests for non-normal data and χ² and Fisher exact tests for categorical data.

A total of 550 patients were included in the study, categorized into 7 BMI groups. The overall re-revision rate was 17%, with the BMI 45 to 49.9 (hazard ratio [HR] 2.4, p = 0.028) and BMI ≥ 50 (HR 2.8, p = 0.007) groups experiencing the highest risk. Implant survival in these groups declined to 70% at 4 years and 40% at 10 years, which was significantly lower than in patients with a lower BMI (p = 0.001). Secondary outcomes revealed that a BMI ≥ 50 was associated with higher 90-day readmission, superficial and deep infection rates, and increased 90-day costs (all p < 0.05), whereas functional improvements following RTKA were comparable across BMI groups (all p > 0.05).

A BMI of 45 to 49.9 and ≥ 50 are risk factors for re-revision, postoperative infection, and readmission rates and increase the 90-day costs associated with RTKA.