Clinical Outcomes of Transmetatarsal Amputation in Patients with Diabetic Foot Ulcers Treated without Revascularization

Diabetic foot is a complicated syndrome that is comorbid with several diabetic complications, such as peripheral arterial disease (PAD) and peripheral neuropathy. It was reported that 10% of diabetic patients will develop this syndrome at least once during their lifetime [1]. Patients with diabetic foot ulcers (DFUs) may undergo minor or major amputation, which will have a considerable impact on patients’ life expectation, quality of life and economic burden. Among minor amputations, transmetatarsal amputation (TMA) appears to be the most convincing in terms of limb salvage rates and in maintaining foot and ankle biomechanics for DFU patients with forefoot necrosis and infection. Under current clinical practice, vascular intervention, anti-infection treatment, surgical operation and postoperative wound care have been performed. However, the reported TMA wound healing rates from multiple series were not good (range, approximately 40–70%) [2‐8].

Around half of patients with DFU have co-existing PAD [9, 10], which is considered the most significant limiting factor for healing of ischemic DFU [11]. Therefore, many researchers had implemented revascularization before the definitive surgical procedure or before final wound closure in DFU patients who needed partial foot amputation to improve ischemia. However, the postoperative limb salvage rates or healing rates in DFU subjects receiving revascularization were still low [3, 4, 6, 12]. DFU patients who have indications for TMA always have forefoot gangrene resulting from severe atherosclerotic lesions below the tibial arteries, microangiopathy, infection and severe comorbid conditions. Revascularization for these patients is, therefore, considered inappropriate or has limited effects after operation [13‐15].

Up to now, few published outcomes of DFU patients without revascularization existed. Therefore, we recruited DFU patients who were not candidates for revascularization who had undergone TMA to observe the outcomes.

Our study showed that the TMA patients treated without revascularization had deteriorated medical condition, mainly manifested in long durations of diabetes and foot ulcer, severe comorbidities and widespread malnutrition. However, we achieved a higher 3-year accumulated healing rate (64.9% in total; 61.8% in patients with PAD) and a lower 3-year accumulated mortality rate (24.7%) after a comprehensive treatment and postoperative care. This study provided a reference for the treatment of TMA patients who were not feasible for revascularization.

In contrast, the following were previously reported results on TMA in which most subjects received revascularization [3, 4, 6, 12]. Patients’ baseline characteristics were as follows: average age ranging from 55 to 64 years old, cardiovascular-related factors including smoking 18–56% [3, 4, 12], hyperlipidemia 17.6–51% [3, 4], hypertension 63–76% [4, 12] and cardiac disease 37–51% [4, 12] and other indicators [12], BMI 27.6 kg/m², heart failure 32% and renal insufficiency 21%. Outcomes included healing rate 43–62% [3, 6, 12], limb salvage rate 68% [4] and survival rate 67–82% and 35–69% at 1 and 3 years, respectively [3, 6, 12]. It is enough to observe that our research patients’ medical conditions were not better than those of these patients regardless of age, cardiovascular-related factors and other comorbidities. However, we achieved healing and survival rates comparable to the above studies. Maybe this favorable outcome is partially owing to medicine and rehabilitation (double-leg empty pedal bicycle movement is similar to intensive walking exercise) to improve lower extremity circulation during the entire study [15, 21], paying attention to the improvement of nutritional status [22, 23] and organ functions as well as proper HbA1c level [24].

In the above studies [3, 4, 6, 12], some patients had undergone revascularization, either endovascular or surgical, before amputation was performed. Study outcomes were based on patients who had and had not undergone revascularization. Some came to the conclusion that the need for revascularization was not associated with limb loss [4]. It is currently unclear how to identify those patients with PAD and DFU who are most likely to benefit from revascularization. Furthermore, there is debate about the selection of the correct revascularization technique [25]. We also learned that some studies on foot ulcers treated without revascularization while focusing on wound and comorbidity management yielded encouraging results. Marston et al. [26] reported 52% of limb ulcers in which 70.4% were diabetic and healed within 1 year of follow-up, and Elgzyri et al. [27] reported 50% of studied DFU patients healed either primarily (76%) or with a minor amputation (24%) of continuous follow-up until healing. It can be concluded from these studies that diabetic patients with ischemic foot ulcers not feasible for revascularization still have a possibility of healing.

PAD has been shown to be the significant predictor of ulcer healing in diabetic patients [11]. Pinzur et al. [28] reported a 92.2% healing rate after TMA with a minimum ABI of 0.5 in diabetic patients and serum albumin of 30 g/l. Pollard et al. [7] reported a palpable pedal pulse was a clinically significant predictor of healing after TMA. Marston et al. [26] reported ABI was independently associated with amputation at 1 year; 32% of limbs with an ABI < 0.5 and 43% of limbs with an ABI < 0.4 required amputation compared with 15% of limbs with an ABI 0.5–0.7. In the current study, ABI was closely associated with wound healing. The healing rate in patients with an ABI 0.7–0.9 was 87.8% and ABI 0.41–0.69 was 35.5%, but ABI ≤ 0.4 only 11.1%; 16 patients received above-the-ankle amputation, and half of them had an ABI ≤ 0.40. This suggested that patients with severe lower limb ischemia might be not feasible candidates for TMA. Instead, further amputation based on angiography might be performed.

The presence of DFU has to be recognized as a sign of multi-organ disease [29, 30], and a multidisciplinary treatment is the best way to improve the outcome [31, 32]. For TMA, receiving revascularization or not, the following methods should be considered as top priorities to facilitate the success of partial foot amputation procedures: teamwork that includes comprehensive medication therapy, wound care, rehabilitation exercise, and improving nutritional status and organ function.

There were several limitations to the study. First, it was a single-center observation, inevitably including selection bias. Second, although the principles of treatment are the same, comparison with other studies is difficult owing to differences in design, patient selection, definitions, follow-up time, specific treatment details and other confounding factors. Third, very few studies have been conducted on diabetic patients with the same question, and the sample size of our study was not large. We expect a TMA cohort of a bigger sample investigating this issue to be reported in the future.

Diabetic patients who were not candidates for revascularization who underwent TMA could achieve good wound healing rates with improved medical treatment, wound care plans, medical nutrition therapy and rehabilitation exercise. This study indicates that PAD and patients’ medical condition are crucial in the wound healing of TMA.