Transmetatarsal Amputation Outcomes When Utilized to Address Foot Gangrene and Infection: A Retrospective Chart Review

Abstract

A transmetatarsal amputation (TMA) is a widely utilized procedure to address foot gangrene and infection. Although a common procedure, so too are the associated complications. The purpose of this review was to evaluate TMA healing and to explore if there were associated variables correlating with healed vs. failed to heal TMA sites. To do so, the Medical Department Orthopaedics Division Electronic Database, West Virginia University, College of Medicine was retrospectively searched to identify all cases of TMAs (CPT code 28805) during the period of January 2011 through June 2019, and those variables that might impact TMA healing. Then both univariate and multivariable logistic regression analyses were performed to investigate the associations between these variables and TMA healing, and sensitivity analyses were also conducted to determine if the results resisted the influence of one unmeasured confounder. There were 39 patients (41 procedures) who would undergo a TMA. The mean average patient age was 53 (range 29-73) years old. The median postoperative follow-up period was 617 (range 199-3632) days. TMA mortality data revealed 0 deaths at 30 days, 2 (5.1%) at 1 year, 8 (20.5%) at 5 years. In our study, 29 (70.7%) of the TMAs would achieve primary healing at a median of 31 (range 16-253) days. When comparing the TMA healed group to the failed to heal group the following independent variables were considered: diabetes mellitus, HgA1c >8%, neuropathy, peripheral arterial disease, chronic kidney disease, active smoking status, previous surgery, and a clean margin metatarsal bone pathology specimen positive for osteomyelitis. Of the aforementioned, only neuropathy (odds ratio [OR] = 0.056, 95% confidence interval [CI] = 0-0.501, p = .0062) and positive bone margin (OR = 0.144, 95% CI = 0.022-0.835, p = .0385) were found to be significant in univariate logistic regression analysis. In multivariable logistic regression analyses where the potential confounders age, gender, and body mass index were accounted for, of the 8 independent variables of interest, only neuropathy (OR = 0.037, 95% CI = 0-0.497, p = .0036) remained significantly associated with the healing status. Neuropathy was present in 17 (58.6%) of the healed TMAs and in 12 (100%) of the failed to heal TMAs. However, the positive bone margin failed to reach statistical significance (OR = 0.079, 95% CI = 0-1.39, p = .1331). Results from another multivariable logistic regression model where a quadratic term for age was added revealed that positive bone specimen correlated with the TMA healing status with significance (OR = 0.051, 95% CI = 0.001- 0.560, p = .0404). A positive clean margin bone specimen was found in 3 (10.3%) of the healed TMAs and in 4 (44.4%) of the failed to heal TMAs. The sensitivity analysis where current ulceration was used as an unmeasured confounder indicated that the results regarding the association between neuropathy or positive bone margin and TMA healing, though inconclusive, resisted the influence of this unmeasured confounder. Hopefully these findings will be a beneficial addition to the current TMA literature and as such, further assist with informed surgical decision making.