SLR - September 2015 - David Vieweger

The Impact of Obesity on the Outcome of Total Ankle Replacement

Reference: Bouchard M, Amin A, Pinsker E, Khan R, Deda E, Daniels TR. The Impact of Obesity on the Outcome of Total Ankle Replacement. J Bone Joint Surg Am. 2015 June 3;97(11):904-910.

Scientific Literature Review

Reviewed By: David Vieweger, DPM
Residency Program: Medstar Washington Hospital Center, Washington, D.C.

Podiatric Relevance: Although the increasing impact of obesity on the prevalence of chronic diseases is well documented, its importance in the outcomes of orthopaedic procedures has been understated. Extensive research has previously demonstrated higher instances of implant failure and infection in total hip and knee arthroplasty. However, such data on total ankle replacement (TAR) is lacking. The purpose of this study was to investigate outcomes and complications in total ankle replacement between an obese and non-obese patient cohort.

Methods: This retrospective cohort study identified patients who underwent TAR between May 2002 and November 2010. Patients completed an Ankle Osteoarthritis Scale (AOS) and Short Form-36 (SF-36) preoperatively and at least two years postoperatively. Complications and revisions were recorded. The inclusion criteria was eighteen years of age or older, diagnosis of end-stage ankle arthritis and had undergone primary TAR. Exclusion criteria included coronal plane deformity of 10 degrees or greater, charcot arthropathy, postinfectious arthritis, neurologic disorders affecting gait, ipsilateral lower limb surgery within the past twelve months, or TAR converted from ankle arthrodesis. The Mobility, HINTEGRA, and STAR implants were used. The authors measured the outcome of the AOS and the SF-36 Physical Component Summary and Mental Component Summary scores.

Results: Thirty-nine patients who qualified as obese (BMI >30 kg/m2) and 48 patients who qualified as non-obese (BMI <25 kg/m2) were included. The mean BMI of the obese group was 36 kg/m2 and was 26 kg/m2 for the non-obese group. Twenty-six percent of the obese patients had a BMI >40 kg/m2 and were considered morbidly obese. The mean age at time of surgery was 62 in both groups and the mean follow-up length was nearly four years in both groups. There was no difference in preoperative and postoperative AOS pain scores. Each group demonstrated significant improvement in preoperative to postoperative AOS pain scores (35.7 points for the obese group and 33.8 points for the non-obese group). There was no difference in preoperative or postoperative AOS disability scores between groups. However, there was significant improvement in AOS disability scores following TAR (40.5 points in the obese group and 32.6 points in the non-obese group). The preoperative SF-36 PCS score was significantly worse for the obese patients (29.5 points) than the non-obese patients (34.5 points). However, post-operatively, the mean scores were similar (39.2 for obese group and 40.3 for non-obese group). The SF-36 MCS demonstrated no change from preoperative to postoperative score in either group, nor was the change significant from one another. The proportion of complications within each group was similar and included metal component revision, polyethelene liner exchange, and deep infection.

Conclusions: Despite the worse preoperative functional scores in obese patients, TAR was found to yield similar pain and disability relief in both obese and non-obese patients with few complications. However, a small patient population and relatively short follow-up limit this study significantly. Although sparse in comparison to total hip and knee arthroplasty, the orthopaedic literature on the influence of obesity on outcome of TAR continues to grow. Based on this study, podiatric surgeons can feel comfortable that complications of ankle replacement surgery are not significantly greater in their obese patients with excellent functional becoming the norm. However, further studies are needed to elucidate the influence of obesity on the total ankle replacement. 

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