SLR - May 2019 - Elizabeth Chan

Renal Function as a Predictor of Early Transmetatarsal Amputation Failure

Reference: Ahn J, Raspovic KM, Liu GT, Lavery LA, Fontaine JL, Nakonezny PA, Wukich DK. Renal Function as a Predictor of Early Transmetatarsal Amputation Failure. Foot & Ankle Specialist. 2018 Dec; 20(10):1–13.

Scientific Literature Review

Reviewed By: Elizabeth Chan, DPM
Residency Program: The Jewish Hospital, Cincinnati, OH

Podiatric Relevance: Transmetatarsal amputation (TMA) is a common limb salvage procedure indicated for patients with nonhealing wounds secondary to ischemia or infection. Although peripheral arterial disease (PAD) has been shown to be an independent risk factor for TMA failure, previous studies evaluating the association between renal dysfunction (CKD or ESRD) and the need for proximal amputation have shown inconsistent results. Renal impairment has been known to affect wound healing and to increase risk for amputation and mortality; however, there have been limited studies on the role of CKD affecting TMA healing. The primary purpose of this study was to utilize a larger database compared to previous studies to assess the relationship between renal dysfunction and TMA failure during the 30-day postoperative period.

Methods:
This was a retrospective study of a total of 2,018 patients who underwent transmetatarsal amputations secondary to ischemia or lower-extremity infections identified in the American College of Surgeons National Surgical Quality Improvement Program database. Main exclusions included patients with TMAs not associated with PAD, infection (such as trauma, frostbite or burns) and/or complications of previous amputations. The primary outcome of interest was reamputation after TMA, which they defined as an unplanned reamputation at any level related to the primary TMA within the 30-day postoperative period. Secondary outcomes were also evaluated and included overall unplanned reoperation, readmission, major amputation and 30-day mortality.

Results: Out of 2,018 patients who received TMAs, 10.1 percent required reamputation, and of those, 43.3 percent were within 30 days. ESRD (defined as an eGFR < 15) was found to be an independent risk factor for reamputation. In fact, there were 100 percent increased odds of TMA failure with ESRD and 182 percent increased odds of 30-day mortality. A leukocytosis (WBC >10K) and the presence of an intraoperative deep infection were also shown to be independent risk factors for reamputation. However, this study did not find any progressive increase risk of TMA failure with worsening levels of GFR (CKD stages I-IV) prior to ESRD. Furthermore, dialysis and ESRD were associated with secondary outcomes, including more reoperations, major amputations, readmissions and 30-day mortality.

Conclusion: This study is one of the largest and most comprehensive retrospective cohort studies to date evaluating renal dysfunction and TMA failure. These results are critical because understanding these factors associated with TMA failure can identify patients’ risk level and can guide physicians to select the most appropriate initial amputation site to reduce the number of subsequent unplanned surgeries. These associated factors can also aid in guiding patient discussion toward more realistic expectations. While this study did not show a worsening risk of TMA failure as a function of declining GFR prior to ESRD, further studies with greater sample size evaluating CKD patients exclusively will likely be needed to show a correlation in TMA failure risk with progressive stages of CKD.  Knowledge of this type of clinical correlations will be useful for integrating nephrology and podiatric care. Future prospective studies will also be useful to identify risk factors for TMA failure in the postoperative period beyond 30 days. 

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