BackgroundElevated body mass index (BMI) is a known perioperative risk factor for complications such as delayed wound healing and infection. However, there is a gap in understanding how elevated BMI impacts outcomes after posttraumatic lower extremity (LE) microvascular reconstruction.MethodsA retrospective review was performed at a level 1 trauma center between 2007 and 2022 of patients who underwent posttraumatic microvascular LE reconstruction. Demographics, flap/wound details, complications, and outcomes were recorded. Patients were stratified into BMI Center for Disease Control categories.ResultsA total of 398 patients were included with an average BMI of 28.2 +/- 5.8. Nearly half (45%) of LE defects were located in the distal third of the leg, 27.5% in the middle third, and 34.4% in the proximal third. Most reconstructions utilized muscle-containing flaps (74.4%) compared with fasciocutaneous flaps (16.8%). Surgical approaches included free flaps (47.6%) and local flaps (52.5%). Class III obese patients were significantly more likely to be nonambulatory than nonobese patients (OR: 4.10, 95% CI 1.10-15.2, p = 0.035). At final follow-up, 30.1% of patients with Class III obesity were ambulatory, requiring either wheelchairs (42.3%) or assistance devices (26.9%). There were no significant differences in complication rates based on obesity status (0.704). The average follow-up time for the entire cohort was 5.8 years.ConclusionsBMI is critical for patient care and surgical decision-making in LE reconstruction. Further research is warranted to optimize outcomes for higher BMI patients, thereby potentially reducing the burden of postoperative complications and enhancing overall patient recovery.