The impact of obesity on the outcome of total ankle replacement.

Abstract

Obese patients have a slightly higher proportion of revision and infection following knee or hip replacement, but functional improvement is equivalent to that of normal-weight patients. We compared outcomes of total ankle replacement for end-stage ankle arthritis in obese and normal-weight patients. This retrospective cohort study compared thirty-nine obese patients (those with a body mass index of ≥30 kg/m(2)) at a mean follow-up time of 3.76 years and forty-eight non-obese patients (those with a body mass index of <30 kg/m(2)) at a mean follow-up time of 3.92 years after total ankle replacement. Outcome measure scores (Ankle Osteoarthritis Scale [AOS] and Short-Form 36 [SF-36]) were collected preoperatively and at least two years postoperatively. Complication and revision data were collected by manual chart audits. Statistical analyses were performed with use of t tests, Wilcoxon signed-rank tests, and Mann-Whitney U tests. Survival analysis was conducted with use of the Kaplan-Meier method. The two cohorts had similar demographic characteristics. Ten (26%) of thirty-nine patients in the obese group were morbidly obese (having a body mass index of >40 kg/m(2)). There were thirty-nine patients in the obese group and forty-eight patients in the non-obese group. The mean body mass index (and standard deviation) was 36.28 ± 5.43 kg/m(2) for the obese group and 25.84 ± 3.00 kg/m(2) for the non-obese group. The obese group had significantly worse preoperative SF-36 Physical Component Summary scores (p = 0.01) than the non-obese group. Preoperatively to postoperatively, both obese and non-obese patients demonstrated significant improvements (p < 0.001) in AOS pain, AOS disability, and SF-36 Physical Component Summary scores, and the changes in these scores were similar for both groups. The SF-36 Mental Component Summary scores did not change significantly (p = 0.30) in either group. There was no significant difference (p = 0.48) in the proportion of complications or revisions between the groups. Although obese patients had increased disability and worse function preoperatively, total ankle replacement significantly and similarly improved pain and disability scores in both obese and non-obese patients, with no significant difference in the proportion of complications. We therefore maintain that total ankle replacement is a reliable treatment option for patients with end-stage ankle arthritis, including those who are obese. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.