Rate of residual osteomyelitis after partial foot amputation in diabetic patients: a standardized method for evaluating bone margins with intraoperative culture.

The purpose of this study was to determine the rate of residual osteomyelitis after different foot amputations in diabetic patients with a standardized method of determining a clean bone margin. This retrospective observational pilot study evaluated 27 diabetic patients who had a forefoot amputation (toe, partial ray, or transmetatarsal) for osteomyelitis at our institution from January 1, 2010, to August 1, 2011. A standardized method was used intraoperatively to determine if bone margins were negative for residual osteomyelitis. Short-term outcomes were assessed. Negative outcomes included wound dehiscence, re-ulceration, re-amputation, or death. The overall rate of residual osteomyelitis was 40.7% (11/27 patients). Patients who underwent toe amputation with joint disarticulation had a positive margin culture rate of 23.1% (3/13). Patients who underwent partial metatarsal or transmetatarsal amputation had a positive margin culture rate of 57.1% (8/14). Although twice as frequent, this was not considered to be statistically significant (p = .1201). Overall, 48.1% (13/27) of patients were considered to have poor outcomes, and 9/11 (81.8%) patients with a positive bone margin had poor outcomes, whereas only 4/16 (25%) patients with a negative bone margin had poor outcomes. This difference was considered statistically significant (p = .0063). Although this is a pilot study, our results do confirm the high incidence of residual osteomyelitis with associated poor outcomes. Based on our data, we recommend routine standardized bone margin culture after thorough debridement and irrigation.