Outcomes of Limb-Sparing Surgery for Osteomyelitis in the Diabetic Foot: Importance of the Histopathologic Margin

Background. Diabetes mellitus affects up to 14% of Americans. Infection of the diabetic foot is a common complication, which may lead to amputation. If infection extends to involve bone, the risk of amputation is increased 4-fold. Presence of osteomyelitis at the histopathologic margin of resection portends a poor prognosis in osteomyelitis outside the setting of the diabetic foot. We aimed to assess the association of a positive histopathologic margin with the outcome of osteomyelitis in the diabetic foot. Methods. Medical records were reviewed for all patients who underwent below-ankle amputation for osteomyelitis of the diabetic foot. Patients who had at least 1 year of follow-up, a histopathologic diagnosis of osteomyelitis, and a comment on whether the margin was involved were included. Results. Thirty-nine of 66 (59%) cases had remission of osteomyelitis at 12 months. When comparing cases with remission with those who experienced recurrence in the 12 months of follow-up, there were no statistically significant differences in age, glycosylated hemoglobin, duration of antimicrobial therapy, Infectious Diseases Society of America class, or presence of osteomyelitis at the histopathologic margin. Among cases with a negative histopathologic margin, 29/48 (60.4%) were free of disease at 1 year, compared with 10/18 (55.6%) cases with a positive histopathologic margin (P =.72). Remission was significantly more frequent in cases undergoing amputation at the digit level (66.7%) compared with amputation at the metatarsal level (40.7%) (P =.045). Conclusions. Osteomyelitis of the diabetic foot at the histopathologic margin of resection was not associated with increased risk of treatment failure. Resection at the level of the digit was associated with a lower risk of failure than at the metatarsal level.