The first step of treatment for diabetic foot wound is to evaluate, debride, and treat infection [3]. Missing timely management will lead to amputations and longer hospital days [26]. If symptoms and signs of infection are clinically suspected, proper treatment must be provided without delay. If superficial infection is suspected without systemic infection, antibiotic treatment along with non-weight bearing of the foot should be ensued. Optimal management of diabetic foot infection can potentially reduce incidence of major limb amputations and other related morbidities. All nonviable and infected soft tissue and bone should be excised during debridement. Milking along the proximal tendon can be helpful to identify and limit ascending infection. Tissue culture should be sent. Sufficient irrigation should follow after debridement to reduce bacterial count [4]. Recent advance in technology introduced a hydrosurgery system that allows to debride while preserving viable tissues and irrigate simultaneously, allowing reduced surgical time [15, 16]. Biodebridement such as maggot therapy has also been useful in clearing the necrotic tissue [10]. Application of negative pressure wound therapy has also played a role in reconstruction as they are used as an indicator and a wound preparation method of achieving clean wound with reasonable vascularity.

The understanding of vascular distribution of the foot, angiosome, helps to plan not only reconstruction but debridement [8]. When planning for reconstruction, one can avoid violating the angiosome territory when designing a local flap that may lead to flap breakdown [2]. Also by performing debridement according to the angiosome territory, one may enhance flap survival by increasing the chance for marginal vascularization from healthy surrounding angiosome territory.

Repetitive debridement should be performed as part of wound preparation for reconstruction while monitoring C-reactive protein for possible hidden infections and using it as an index for possible infection after reconstruction.

In our surgical algorithm, all patients considered for microsurgical reconstruction undergo a noninvasive CT angiogram to evaluate the vascular status. The CT angiogram provides information regarding general vascular anatomy of the lower extremity and shows atherosclerotic change of vessels which is useful information when choosing recipient vessels. The overview is important as collateral vessels may be the main trunk to the distal limb. Without this information, one may elevate the flap harvesting the main arterial source to the distal limb and cause limb ischemia. If vascular status is in doubt, then revascularization by angioplasty or bypass surgery is referred. Although preoperative angiograms may indicate intact anatomy of the artery to the foot, actual findings upon surgery can be different. In order to confirm the distal vascular flow, we use ultrasound duplex scans. A study by Kim et al. showed correlation of peak blood flow velocity over 40 cm/s to flap survival [18]. However, in an ongoing study at our center, we hypothesized that the preoperative measurement of flow will not influence the survival of the flap, but the perioperative flow will play a more important factor. For now, ultrasound duplex scan provides information in the selection of recipient vessels or to refer for vascular intervention when no recipient vessels can be identified. The transcutaneous oxygen measurement (TcPO2) also plays a role in our protocol. Measurement over 30 mmHg in normobaric oxygen is a relative predictive factor for successful healing, whereas pressure less than that of 30 mmHg is likely to follow an unfavorable course [7, 14]. The wound, if measured under this level after vascular intervention, was treated with hyperbaric oxygen. If peri-wound TcPO₂ measurements were over 30 mmHg, then further treatment including reconstructive procedures was planned; otherwise, amputations at according levels were performed. The ankle-brachial index (ABI) is not used as it is not reliable in diabetic patients due to the high incidence of calcified vessels causing falsely elevated values [13].

In diabetic patients, the most significant atherosclerosis occurs in the crural arteries often sparing the arteries of the foot [31]. Bypass to the dorsalis pedis or posterior tibial artery of the foot or angioplasty with or without stent placement procedures results in high success to restore perfusion pressure to the distal circulation of the foot reestablishing palpable pulse. The timing of when to perform reconstruction after vascular intervention is not clear. Reports have shown successful free flap transfer with simultaneous vascular reconstruction to salvage the limb [23]. But early bypass failures within 30 days are reported to be high [6, 29]. In our experience, partial flap loss or total loss was suddenly noted after 2–3 weeks in the cases combined with simultaneous or reconstruction following few days after vascular interventions. This may suggest that there should be a sufficient stabilization period after vascular intervention.

Reperfusion is most essential prior to microsurgery reconstruction. If vascular intervention fails and wound progresses, amputation is warranted.

Once an adequate debridement and reasonable vascular perfusion are achieved, in extensive and complex diabetic foot defects, reconstruction should be considered. In my experience, local flaps such as reverse sural, medial plantar, or lateral supramalleolar for large defects have not been as successful as free flap reconstruction. Especially when reconstructing diabetic foot with reduced vascular flow, the utilization of local flaps may breach the distal flow of the small collateral vessels. One must consider current vascular status as well as future flow where small collateral vessels may play an important role for distal circulation. In this sense my choice for moderate and large defects is the reconstructive microsurgery to transfer free flaps. Inclusion criteria from a meta-analysis of free tissue transfer in 528 diabetic patients in 18 studies suggest (1) lower limb defect which has not displayed any signs of granulation or healing despite adequate debridement or necrotic tissue and conservative treatment, (2) no significant renal function impairment, (3) no significant systemic illness likely to be exacerbated by multiple operations and prolonged rehabilitation, (4) previously ambulatory with the aim to restore a functional limb, (5) likely to engage with the significant physiotherapy required for return to normal living, and (6) peak flow velocity of >40 cm/s in the recipient artery. We generally agree with the suggested inclusion criteria except for the significant renal disease. In our experience, we have not found an increased risk for failure despite the fact that uremia may cause a decrease in cell-mediated immunity and impair wound healing [5, 22, 32]. But we did report a significant risk of 4.857 times higher odds for flap failure in patients using immunosuppressive agents after renal transplant (p < 0.041) [22].