Reconstruction of a below-knee amputation stump using a sensate neurovascular foot skin flap: a case report

Article information

Arch Hand Microsurg. 2026;31(2):109-113

Publication date (electronic) : 2026 May 8

doi : https://doi.org/10.12790/ahm.25.0056

Hyungon Choi, Junghwan Yoo, Donghyeok Shin, Jeenam Kim, Myungchul Lee

Department of Plastic and Reconstructive Surgery, Konkuk University School of Medicine, Seoul, Korea

Corresponding author: Myungchul Lee Department of Plastic and Reconstructive Surgery, Konkuk University School of Medicine, 120-1 Neungdong-ro, Gwangjin-gu, Seoul 05030, Korea Tel: +82-2-2030-7639 Fax: +82-2-2030-5249 E-mail: mcle1999@gmail.com

Received 2025 December 15; Revised 2026 February 26; Accepted 2026 March 31.

Abstract

Introduction

Necrotizing fasciitis is a severe disease characterized by widespread, rapidly progressing soft-tissue inflammation along the fascia. It typically occurs after trauma or tissue infection, although it may develop in any body region; the extremities are a particularly common site [1]. If prompt and aggressive surgical treatment is not performed, necrotizing fasciitis can lead to severe clinical deterioration. The mortality rate varies across studies but is estimated at approximately 16% to 30% [2]. Because the infection spreads rapidly along fascial planes, the resulting defect may be extensive once infection control is achieved. Amputation has been reported in approximately 22% of cases [3].

A case of lower-extremity necrotizing fasciitis occurred in a 73-year-old female patient with a history of diabetes and arrhythmia. Herein, we present the reconstruction of the resulting defects. Because there were extensive soft-tissue defects from the ankle to the calf and pretibial area, both the complexity of the wound and functional considerations required careful evaluation. Regarding our patient’s wound, the tibia and adjacent muscles were exposed, and a free flap could be considered for coverage. However, because the patient’s advanced age and underlying comorbidities increased operative risk, a lengthy procedure was undesirable. Accordingly, we sought an alternative operative plan and coverage method. In this context, preserved foot skin was considered as a potential coverage option for the amputation stump. Ultimately, we proceeded with a sensate neurovascular foot skin flap following below-knee amputation.

This report was approved by the Institutional Review Board of Konkuk University Hospital (No. KUH 2026-01-024) and performed in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from the patient.

Case report

The patient presented to the emergency department on November 15, 2023, with worsening swelling of the left ankle and foot. Clinical examination revealed tenderness and erythema extending from the distal left foot to the thigh, along with petechiae on the dorsum of the foot. Laboratory investigations performed in the emergency setting showed a white blood cell count of 13,460/µL, an erythrocyte sedimentation rate of 97 mm/hour, a high-sensitivity C-reactive protein level greater than 32 mg/L, a quantitative D-dimer level of 0.67 mg/L, a procalcitonin level of 46.74 ng/mL, and a presepsin level of 518 pg/mL. Magnetic resonance images of the lower extremity demonstrated diffuse circumferential interstitial edema, leading to a clinical suspicion of cellulitis (Fig. 1). As a result, the patient was admitted for antibiotic therapy. By December 2, the high-sensitivity C-reactive protein level had decreased to 16 mg/L. However, on December 3, the patient experienced hematochezia (roughly 1,000 g) and developed dyspnea, followed by cardiac arrest. After resuscitation, ischemia developed in the lower extremity, and metabolic acidosis worsened due to hypovolemic shock. The patient ultimately developed necrotizing fasciitis of the lower leg (Fig. 2). Extensive necrosis from the dorsum of the foot to below the knee required four sequential debridements. Despite these procedures, a large skin and soft-tissue defect persisted (Fig. 3). Although the use of a free flap could have been considered for coverage, the patient’s advanced age and underlying disease made a long operative time undesirable. Therefore, an alternative operative plan was required, and additional preoperative consultations were conducted. Ultimately, amputation became unavoidable.

Fig. 1.

Imaging findings showing tissue changes on November 27, 2023. Diffuse circumferential interstitial edema was observed in the subcutaneous layer, with fluid-like signal intensity and decreased enhancement (arrow). Signal alterations were also noted in the intrinsic foot muscles around the calcaneus on magnetic resonance images: axial (A) and coronal (B) views.

Fig. 2.

Rapid progression of necrotizing fasciitis on December 4, 2023. (A) Tissue necrosis progressed after cardiac arrest. Necrosis involved the pretibial area and the dorsum of the foot. (B) Necrotizing fasciitis also extensively involved the calf and posterior ankle.

Fig. 3.

Clinical photographs obtained before below-knee amputation after serial debridement. The patient underwent the first (A) and second (B) debridements, during which considerable soft-tissue loss was noted. Four sequential debridements were performed from December 20 to 27, 2023.

Under general anesthesia, the necrotic skin and soft tissue of the lower leg were excised, and the tibia and fibula were removed below the knee. The course of the posterior tibial artery was identified with a Doppler device, confirming its passage past the flexor retinaculum to the plantar aspect of the foot and documenting circulation in the plantar foot skin measuring 20×10 cm. Necrotic skin and soft tissue of the foot, excluding the area with confirmed circulation, were debrided, and the toe and foot bones were excised. The plantar foot skin and soft tissue, with the neurovascular pedicle preserved, were used to cover the exposed tibia and fibula after amputation. To preserve the neurovascular pedicle, dissection over the metatarsal and calcaneal bone was necessary. The pedicle included the posterior tibial artery and vein, the nerve bundle, and a portion of the medial head of the gastrocnemius muscle. This muscle tissue provides protection against compression and kinking of the neurovascular structures, which is a known concern in island foot fillet flaps. The gastrocnemius muscle also contributed essential bulk for stump coverage. During the repair process, the plantar intrinsic muscles, fascia, and gastrocnemius were sutured to tissues adjacent to the tibia and fibula. All available skin on the flap was used to cover the stump. In a non-island fillet flap using dorsal foot tissue, coverage can be achieved more directly up to the knee joint. However, in this case, only the plantar tissue remained viable, necessitating flap transposition to achieve coverage below the knee.

The below-knee amputation was completed with all defects closed directly. The tibial stump measured 7.5 cm in length distally. The length of the tibial stump was determined based on adequate soft tissue coverage without compromised perfusion. The posterior tibial artery-based flap survived completely without major complications (Fig. 4). Minor wound dehiscence occurred along the lateral margin of the flap, and the patient developed knee joint arthritis; both were successfully managed with local wound closure and arthroscopic debridement performed in collaboration with orthopedic surgery. After the stump was shaped and rounded with a compression elastic bandage, a prosthesis was fitted 3 months later. No ulceration occurred in the below-knee stump during follow-up, and no revision procedures were needed (Fig. 5). The wound healed well, and the patient ambulated with a prosthetic limb 6 months postoperatively. The timeline has been summarized in a table (Table 1). Regarding sensation, the patient reported adequate responses to light touch, cold, heat, and pain. The two-point discrimination test measured 30 mm.

Fig. 4.

Radiographic images obtained after below-knee amputation. The tibial stump measured 7.5 cm in distal length (A). The posterior tibial artery-based flap survived well, and the course of the neurovascular bundle is shown on computed tomographic angiography (arrow) (B). The two images were obtained on December 19, 2024 and April 24, 2025, respectively.

Fig. 5.

Postoperative images obtained 4 months after below-knee amputation. The sensate neurovascular foot skin flap survived after below-knee amputation. No ulceration developed in the below-knee stump during follow-up, and no revision procedures were required: anterior (A), lateral (B), posterior (C), and stump (D) views. Adequate coverage of the amputation stump is essential for postoperative rehabilitation.

Table 1.

The timeline of notable events and procedures for treating necrotizing fasciitis.

Discussion

This case highlights the potential complications that can arise in patients with diabetes and arrhythmia, including cellulitis and advanced necrotizing fasciitis. The patient’s presentation with petechiae and extensive skin and soft-tissue defects indicated a more severe infection that eventually required a radical operative approach. The use of plantar skin for reconstruction, along with preservation of the posterior tibial artery and nerve bundle, underscores the importance of reconstructive surgery following a below-knee amputation.

Preservation of the patient’s knee joint and adequate stump length in lower-extremity amputation are crucial for successful rehabilitation. In adults, the ideal bone length for a below-knee amputation stump is approximately 2.5 cm per 30 cm of body height [4]. When amputation is required, preservation of the knee should be pursued whenever feasible, as it offers mechanical advantages for gait rehabilitation and is associated with lower walking energy expenditure and improved functional outcomes [5]. However, when soft-tissue coverage is insufficient, a below-knee amputation may be complicated during postoperative wound management and prosthesis fitting. It may ultimately progress to the need for a thigh amputation.

Thus, if knee preservation is attempted, durable tissue coverage that provides protective sensibility to the stump is essential for successful prosthetic use. In this context, the use of tissue from amputated or non-salvageable limbs for reconstruction of complex defects (referred to as “spare part” surgery) offers the advantage of avoiding donor-site morbidity while enabling preservation of the knee.

An important consideration in lower limb amputation (LLA) is stump length, as individuals with LLA experience higher energy demands during walking and slower walking speeds compared with people without limb loss. The more proximal the level of amputation, the greater the gait morbidity and energy expenditure. Patients with above-knee amputation require approximately 65% more energy to walk at half the speed of non-amputees [5].

Therefore, every effort should be made to perform LLA, preserving the functional level as much as possible [6]. A below-knee amputation is functionally superior to an above-knee amputation because preservation of the knee joint facilitates ambulation [7]. Individuals with above-knee amputation are more likely to be non-ambulatory after one year, and above-knee amputation is associated with significantly higher postoperative mortality rates than below-knee amputation [8].

In attempting to perform a below-knee amputation, the goal was to retain at least 8 cm of tibial length for coverage purposes [9]. However, necrosis had progressed to the area adjacent to the knee in our case. The lower leg exhibited a substantial skin and soft-tissue defect, with viable tissue limited to the plantar region of the foot. The absence of intact skin on the lower leg made the use of a non-island flap impractical, necessitating the creation of an island flap [10]. Because necrosis extended from the lower leg to the entire dorsum of the foot and ankle, a plantar skin and soft-tissue flap was selected rather than a dorsal flap. The patient was 155 cm tall and weighed 50 kg, and the preserved 7.5 cm long tibial stump did not cause adverse events during functional rehabilitation.

In a previous report, pedicled non-islanded foot fillet flaps have been utilized to cover below-knee amputation stump [6]. The non-island pattern can be a safe and viable option; however, preservation of the neurovascular bundle and surrounding muscle in an island flap can also provide adequate coverage with plantar intrinsic muscles, fascia, and skin.

This case report highlights the complications that can develop in patients with diabetes and arrhythmia, resulting in necrotizing fasciitis. Ultimately, the patient required a below-knee amputation because of extensive skin and soft-tissue destruction. The use of plantar skin for adequate coverage and the preservation of the posterior tibial artery and nerve bundle underscore the importance of detailed planning in reconstructive surgery. In summary, the pedicled plantar flap represents a valuable reconstructive option that avoids microvascular anastomosis and can be particularly useful for below-knee stump reconstruction in select cases.

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