Transmetatarsal Amputation Results in Higher Frequency of Revision Surgery and Higher Ambulation Rates Than Below- Knee Amputation

Abstract

Category: Diabetes; Midfoot/Forefoot; Trauma; Other Introduction/Purpose: The level of amputation in patients with severe lower extremity pathology often presents a challenge. Surgeons are often confronted with deciding between a transmetatarsal amputation (TMA) or below-knee amputation (BKA). Certainly, in cases where patients are candidates for a TMA, the decision might seem rather straightforward. However, the literature has demonstrated that minor foot amputations, like TMAs, often have high rates of revision and often necessitate a higher level of amputation. This study compared revision rates, need for higher level of amputation, post-operative ambulatory rates, and the demographics between patients undergoing either TMA or BKA. Methods: This was a retrospective analysis of patients who underwent BKA or TMA and received follow-up care at a single academic medical center from January of 2013 to May of 2021. Demographic and medical historical data was collected and compared between patients undergoing BKA or TMA. A binary logistic regression model was used to evaluate independent predictors for necessitation of revision surgery and/or higher levels of amputation between the two groups. Secondary outcomes included hospital length of stay, as well as ambulatory and wound status at last patient follow-up. Statistical significance was defined as p<.05. Results: A total of 367 patients underwent either BKA (n=293) or TMA (n=74). On binary logistic regression, significant independent predictors of needing surgical revision were undergoing TMA (OR 2.29, CI 1.23-4.27, p=.009) and peripheral arterial disease (PAD) (OR 2.28, CI 1.12-4.6, p=.023). Similarly, significant independent predictors of needing higher level amputation were undergoing TMA (OR 4.4, CI 2.01-9.63, p<.001) and presence of PAD (OR 6.18, CI 2.12- 17.98, p<.001). Secondary outcomes showed that more TMA patients were ambulatory (56.8%) on last follow-up compared to BKA patients (30.9%). Hospital length of stay was significantly greater in the BKA group (17.3 +- 21.2) vs the TMA group (13.6 +- 10.9) (p=.04). There was no significant difference between BKA and TMA groups with respect to healed incisions at last follow-up (58.3% and 51.4% respectively). Conclusion: This study found transmetatarsal amputations to have a higher risk of re-operation and need for revision amputation compared to below-knee amputations. Transmetatarsal amputations had a higher chance of returning patients to independent ambulation. These findings are consistent with the literature suggesting higher reoperation rates in minor foot amputations. Patients with peripheral arterial disease are at a higher risk of revision surgery and higher-level amputation with both operations warranting further vascular work-up for patients with severe PAD and absent pulses.