SLR - May 2023 - Jasmeet Chawla, DPM
Title: Risk Factors for a Failed Transmetatarsal Amputation in Patients with DiabetesReference: Ron I, Kyin C, Peskin B, Ghrayeb N, Norman D, Ben-Kiki T, Shapira J. Risk Factors for a Failed Transmetatarsal Amputation in Patients with Diabetes. J Bone Joint Surg Am. 2023 Mar 21. doi: 10.2106/JBJS.22.00718. Epub ahead of print. PMID: 36943915.
Level of Evidence: Therapeutic level III
Scientific Literature Review
Reviewed By: Jasmeet Chawla, DPM
Residency Program: NYU Langone - Brooklyn
Podiatric Relevance: With the increased prevalence of uncontrolled diabetes and subsequent forefoot ulcerations requiring amputation, transmetatarsal amputations (TMA) have become a widely utilized limb salvage option. This level of amputation allows for preservation of a viable weight bearing construct allowing for efficient energy expenditure during ambulation, facilitating better function. Disadvantages of this level of amputation include increased revision rates in high risk patient population and failures requiring proximal amputation. This study aimed to define risk factors for TMA failure in diabetic patients, defined as below knee amputation (BKA) or above knee amputation (AKA). The authors hypothesized that factors related to the laboratory parameters, infection related factors, history of vascular interventions, and comorbidity status would be predictive of TMA failure.
Methods: This retrospective cohort study includes data from a single tertiary trauma center. 341 patients who underwent primary TMA were identified and included in the study. Patients were divided into two groups - successful versus failed TMA. Failed TMA were defined as requiring eventual BKA or AKA. Emphasis was placed on the Charlson Comorbidity Index (CCI), to estimate 10 year survival, and Norton Score which stratified ulcer risk. Outcome variables included morbidity rate, failure rate, and time to failure.
Results: The results of this study demonstrated kidney function, measured by creatinine levels and estimated glomerular filtration rate (eGFR), were significantly worse in patients who had failed TMA. Laboratory values (C-reactive protein, leukocyte count, albumin) were not significant between groups. The percentage of patients with vascular procedures, history of dialysis and/or kidney transplant were higher in the failed TMA group. CCI threshold value was determined to be > 7.5 and patients who were above this threshold (85 patients) had increased TMA failure rate by 2.7-fold. Of the 85 patients with CCI > 7.5, 61 (71.8%) patients had failure after initial amputation. Of the 256 patients with CCI < 7.5, only 124 (48.4%) patients had failure of initial amputation. CCI was a determinant of lower extremity survival time, as patients with a CCI <7.5 had a median time of 178 months until TMA failure whereas those with CCI > 7.5 had a median time of 1.13 months until initial amputation failure.
Conclusions: Risk factors for TMA and variables associated with failure were determined to be lower blood hemoglobin levels, prior vascular procedures, lower renal function (defined by creatinine, eGFR, dialysis, or history of kidney transplant), and higher CCI. Upon analysis of risk factors, hemoglobin A1c and smoking were not considered to be risk factors for TMA failure which we consider to be unexpected. Limitations of this study included it being retrospective with potential bias due to one institution and surgical approach. Future studies may be needed to determine if morbidity, noted to be higher in patients who underwent revisional surgery, was due to the initial surgery or their comorbidities and medical conditions upon presentation. Overall, this article helps in emphasizing the importance of CCI in predicting potential complications/failure of a TMA in addition to correlating renal function to TMA success rate.