The effect of obesity on post-operative complications and functional outcomes after surgical treatment of torsional ankle fracture: A matched cohort study

Abstract

Background: Obesity is a growing public health concern. While diabetes mellitus is associated with obesity and is a risk for infection and other complications, effects of obesity on outcomes remains less clear. The purpose was to determine effect of obesity on complications, secondary operations, and functional outcomes after surgical treatment of ankle fracture.

Methods: 955 adult patients treated surgically for torsional ankle injury were reviewed. Obese patients (body mass index (BMI) ≥30), and patients without obesity were matched for age, sex, race, diabetes, and fracture pattern. Patient reported outcomes, measured by Foot Function Index (FFI) and Short Musculoskeletal Function Assessment (SMFA), were obtained after 12 months.

Results: 632 patients (316 obese [mean BMI 36.7] and 316 non-obese [mean BMI 25.5]) with mean age 44.6 years were analyzed. Each group was 52.5% female, and 6.6% had diabetes mellitus. 75.6% of fractures in each group were AO/OTA type 44B and 24.4% were 44C. Non-obese patients were more likely tobacco users (63.3% vs 40.2%, p<0.001). Obese patients trended toward more dislocations (41.8% vs 35.4%, p=0.10), with similar rate of open fracture. Obese patients trended toward more complications (28.5% vs 22.5%. p=0.08) and wound healing problems (4.7% vs 2.2%, p=0.08) with similar rates of secondary procedures. Total FFI scores were higher (worse) for obese patients (35.4 vs 28.5, p=0.03); subcategory scores for disability and activity limitation were worse (p=0.03 and p=0.04, respectively), and obesity was associated with worse SMFA bothersome (31.0 vs 23.6, p=0.02) and mobility scores (41.8 vs 32.5, p=0.008), with a trend towards worse SMFA dysfunction scores in obese patients (29.7 vs 24.7, p=0.06).

Conclusions: Obesity is associated with worse functional outcomes by FFI and SMFA surveys. Contributions of baseline limitations to these poor scores in obese patients remain unclear. Injury characteristics were similar between obese and non-obese patients, though obese patients may be more prone to dislocations. A trend was noted for obese patients to experience more complications and wound healing issues, although rates of secondary operations were no different.

Level of evidence: III.