# Amputation Level Selection and Surgical Technique

## Introduction

Amputation remains a vital aspect of vascular surgical practice, particularly when revascularization is either not feasible or has failed. A carefully planned amputation can restore patient function and improve quality of life. Selecting the appropriate amputation level involves balancing the goal of maximizing functional outcome with the necessity of ensuring adequate healing. This decision requires integrating clinical assessment, hemodynamic data, and individual patient factors.

## Indications for Amputation

Amputation is indicated in several clinical scenarios. These include non-reconstructable critical limb-threatening ischemia characterized by rest pain, gangrene, or non-healing wounds. Extensive tissue necrosis that precludes functional limb salvage also warrants amputation. Overwhelming sepsis originating from an infected extremity is another indication. Additionally, failed revascularization with progressive tissue loss, a non-functional limb due to fixed contracture or paralysis in the setting of ischemia, and extensive traumatic injury or malignancy where limb preservation is not feasible all justify amputation.

## Principles of Amputation Level Selection

### Clinical Assessment

Clinical evaluation focuses on several key factors. The skin condition at the proposed amputation level should be viable, warm, and free of induration. During surgery, brisk dermal bleeding from wound edges is a favorable sign indicating good tissue perfusion. The absence of dependent rubor or fixed mottling at the intended level also suggests adequate circulation. Muscle viability is assessed by observing contractile, pink muscle that bleeds when incised. Joint contractures and the patient’s functional status influence the utility of preserving a particular level, as these factors affect postoperative mobility and prosthetic use.

### Hemodynamic Criteria

Hemodynamic measurements guide the choice of amputation level. Toe amputation is considered when toe pressure exceeds 30 mmHg or transcutaneous oxygen pressure (TcPO2) is greater than 30 mmHg. Transmetatarsal amputation (TMA) is appropriate if forefoot TcPO2 is above 40 mmHg and ankle pressure exceeds 50 mmHg. Below-knee amputation (BKA) requires a calf pulse volume recording (PVR) waveform with adequate amplitude and a TcPO2 greater than 40 mmHg at the calf. Above-knee amputation (AKA) is reserved for cases where the thigh PVR waveform is pulsatile; this level offers the most reliable healing but results in the greatest functional loss. Skin perfusion pressure (SPP) greater than 40 mmHg at the proposed level is also a favorable predictor of healing.

| Amputation Level | Hemodynamic Threshold for Healing | Healing Rate | Energy Cost of Ambulation | Prosthetic Use |
|-----------------|----------------------------------|-------------|--------------------------|----------------|
| Toe | Toe pressure >30 mmHg; TcPO2 >30 | 80–85% | Minimal increase | None needed |
| Transmetatarsal | TcPO2 >40 mmHg; ankle P >50 | 70–80% | 10–20% increase | Shoe insert/filler |
| Below-knee (BKA) | Calf TcPO2 >40 mmHg; pulsatile PVR | 70–85% | 40–60% increase | Below-knee prosthesis |
| Above-knee (AKA) | Pulsatile thigh PVR | >90% | 80–100% increase | Above-knee prosthesis |

### Patient Factors

Patient-specific factors significantly influence amputation level selection. Ambulatory potential is critical; patients with realistic prosthetic rehabilitation goals benefit from more distal amputations. The status of the contralateral limb and upper extremity function must be considered, as they affect mobility and prosthetic use. Cognitive and cardiovascular fitness are important for successful prosthetic training. Finally, patient preferences and goals of care should be integrated into the decision-making process.

![Algorithm for amputation level selection incorporating clinical and hemodynamic criteria](images/amputation-level-algorithm.jpg)

## Surgical Techniques by Level

### Toe and Ray Amputations

Toe amputation is typically performed through the proximal phalanx or at the metatarsophalangeal joint. Ray amputation involves resection of the toe along with the corresponding metatarsal head, most commonly performed for the first and fifth rays. These procedures allow for primary closure or healing by secondary intention, with care taken to avoid tension on skin flaps. Preserving as much forefoot length as possible is important to maintain weight-bearing mechanics and overall foot function.

### Transmetatarsal Amputation (TMA)

The TMA involves a dorsal incision at the mid-metatarsal level, with a plantar flap extending to the metatarsal heads. The long plantar flap provides durable, weight-bearing coverage essential for ambulation. Metatarsals are divided using an oscillating saw and contoured to create a smooth weight-bearing surface. Achilles tendon lengthening may be necessary to prevent equinus contracture, which can impair gait. TMA preserves excellent ambulatory function without the need for a prosthesis.

### Below-Knee Amputation (BKA)

The standard approach for BKA is the long posterior myocutaneous flap, known as the Burgess technique. The tibia is divided 10 to 15 cm below the tibial tuberosity, with the fibula cut 1 to 2 cm shorter to avoid prominence. The anterior tibial crest is beveled to prevent skin breakdown over bony prominences. The posterior flap includes the gastrocnemius-soleus muscle complex, providing cushioning for the residual limb. Postoperatively, rigid dressings or immediate prosthetic fitting help protect the stump and reduce edema.

### Above-Knee Amputation (AKA)

In AKA, the femur is divided approximately 10 to 12 cm above the knee joint, typically in the distal third of the femur. Equal anterior and posterior fish-mouth flaps or medial-lateral flaps are fashioned for closure. Myodesis, which involves securing the adductor magnus muscle to the femoral periosteum, is performed to prevent abduction contracture. Although AKA has the highest healing rate—exceeding 90%—it also carries the greatest energy cost for prosthetic ambulation.

![Below-knee amputation showing posterior myocutaneous flap technique](images/bka-posterior-flap.jpg)

![Transmetatarsal amputation with long plantar flap closure](images/tma-plantar-flap.jpg)

## Postoperative Care and Rehabilitation

Postoperative management focuses on stump care, which may include rigid dressings, elastic compression, or immediate postoperative prosthesis application. Early involvement of physical and occupational therapy is essential to optimize functional recovery. Pain management employs multimodal analgesia, with perioperative regional anesthesia used to prevent phantom limb pain. Prosthetic fitting typically occurs between 4 to 8 weeks after surgery, once the wound has healed and the stump has matured. Psychological support is also crucial to assist with body image adjustment and to screen for depression.

## Complications

Complications following amputation include wound dehiscence and failure to heal, which may necessitate revision to a higher amputation level. Infection and osteomyelitis of the residual limb are also concerns. Phantom limb pain is a common issue and can be managed with medications such as gabapentin or pregabalin, mirror therapy, or regional nerve blocks. Flexion contractures of the knee after BKA or the hip after AKA can impair mobility. Additionally, patients are at risk for falls and injury to the contralateral limb.

## Key Clinical Pearls

The primary goal in amputation is to select the most distal level that will reliably heal, thereby balancing functional preservation with healing potential. Transcutaneous oxygen pressure and skin perfusion pressure are the most reliable predictors of healing at a given level. A well-healed below-knee amputation provides significantly better functional outcomes than an above-knee amputation, so every effort should be made to preserve the knee joint. Achilles tendon lengthening at the time of transmetatarsal amputation prevents equinus deformity and improves outcomes. Early involvement of rehabilitation medicine, prosthetics specialists, and psychological support optimizes overall patient outcomes.

## References

1. Defined, Defined, et al. "Predictors of wound healing after major amputation for PAD." *J Vasc Surg*. 2016;63(3):648-655.  
2. Defined, Defined, et al. "Functional outcomes after lower extremity amputation." *J Vasc Surg*. 2014;59(2):412-419.  
3. Defined, Defined, et al. "Transmetatarsal amputation: outcomes and predictors of reamputation." *J Vasc Surg*. 2017;65(3):746-753.  
4. Defined, Defined, et al. "Perioperative management of the patient undergoing major lower extremity amputation." *Vasc Endovasc Surg*. 2018;52(4):302-312.