The Impact of Obesity on the Outcome of Total Ankle Replacement

Background: 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.

Methods: This retrospective cohort study compared thirty-nine obese patients (those with a body mass index of ≥30 kg/m2) 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/m2) 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.

Results: 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/m2). 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/m2 for the obese group and 25.84 ± 3.00 kg/m2 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.

Conclusions: 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.

Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.