Syme Amputation (Ankle Disarticulation)

Indication. A Syme amputation is an end-bearing ankle disarticulation used when the forefoot or midfoot is unsalvageable but the heel pad and its blood supply are pristine. The classic situations are: - Unsalvageable forefoot or midfoot infection or gangrene — severe diabetic foot sepsis that cannot be managed with a partial foot amputation.

• Severe distal foot trauma — crush or blast injuries where the forefoot cannot be reconstructed but the heel pad is uninjured.
• Forefoot or midfoot tumours where ankle disarticulation achieves adequate oncological margins.
• Congenital foot deformities (e.g. fibular hemimelia, severe untreated clubfoot) where a Syme provides a superior prosthetic base than the native deformed foot. Prerequisites for success. Before offering a Syme, three boxes must be ticked: - Vascular — a palpable posterior tibial pulse, Doppler biphasic flow, or TcPO2 greater than 30 mmHg. The posterior tibial artery is the sole supply to the heel pad through its medial calcaneal branches.
• Soft tissue — the heel pad skin must be completely intact, with no deep ulceration, necrosis or active infection, and healthy enough to bear full body weight.
• Functional — the patient must have the cognitive and physical capacity to engage with prosthetic rehabilitation. Contraindications. Absolute: absent posterior tibial artery flow (unless reconstructable by bypass), heel pad necrosis or deep ulceration, inadequate tissue oxygenation (TcPO2 less than 20 mmHg universally predicts failure), and ascending gas gangrene (which needs a higher open amputation for life salvage). Relative: severe neuropathy risking unrecognised heel trauma, and a bedbound non-ambulatory patient — a transtibial amputation often heals more reliably and faster in a severe dysvascular bedbound patient, even though a Syme is end-bearing and can assist with pivot transfers. The one decision that matters — one-stage or two-stage. Every Syme begins the same way, with ankle disarticulation. The only choice is whether to do the definitive malleolar resection and pad closure immediately, or stage it:

Consent specifically for the possibility of heel pad necrosis (which can mean revision to a transtibial amputation), heel pad migration, painful neuroma within the socket, wound infection (highest in diabetics with active sepsis), and the lifelong need for a specialised Syme prosthesis. Setup. Supine with a sandbag under the ipsilateral buttock to bring the leg to neutral and the lateral malleolus anteriorly. A thigh tourniquet may be used in trauma or congenital cases but is generally avoided in severe peripheral vascular disease to avoid further ischaemic insult. Prep and drape the entire leg from the knee down so alignment and rotation can be judged accurately.

The goal is to disarticulate at the ankle, deliver the calcaneus out of the heel pad by strictly subperiosteal dissection (protecting the pad's architecture and the posterior tibial artery), resect the malleoli flush and parallel to the ground, and anchor the pad squarely beneath the distal tibia so it becomes a durable end-bearing surface. The exposure — incision, anterior dissection and ankle disarticulation — is laid out in the first steps below; the calcaneal dissection is the technical heart of the operation.

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Rehabilitation | Phase | Timing | Management | Weight-bearing | |-------|--------|------------|----------------| | Early | 0–2 weeks | Rigid or semi-rigid cast applied in theatre; deep drain removed at 48 hours or when output is minimal; limb elevated | Strictly non-weight-bearing | | Intermediate | 2–6 weeks | Cast change at 10 to 14 days for wound check and suture removal (diabetics up to 3 weeks); re-cast snugly to shape the stump and control oedema | Remains non-weight-bearing until 6 weeks | | Late | 6 weeks and beyond | Once healed and the pad is stable (typically 6 to 8 weeks), refer to prosthetics for casting; gait training with a Syme prosthesis | Progression to full prosthetic weight-bearing | Instruct the patient never to rest the stump directly on the bed, which causes posterior pad migration. Prosthetic considerations - The Syme stump is naturally bulbous because the metaphyseal flare is preserved — this gives excellent suspension but needs a specialised socket (a medial window or expandable wall) for donning and doffing.

• A Syme amputation shortens the limb by about 5 to 7 cm (the combined height of the calcaneus and talus). The prosthesis must make up this height, which limits the vertical clearance for complex prosthetic feet — high-energy-return feet can be hard to fit.
• Because the native heel pad sits directly under the tibia, the stump is end-bearing and can take direct axial load — superior proprioception and the ability to walk short distances barefoot (e.g. to the bathroom at night), a major functional advantage over a transtibial amputation. Complications

Danger structures — what threatens the stump, and the fix

History. The operation was described by the Scottish surgeon James Syme in 1843 as an end-bearing alternative to a below-knee amputation. Wagner (1977) established the modern principles of patient selection and the critical preoperative vascular assessment, and Pinzur and Smith (1995) developed the two-stage modification specifically for the infected diabetic foot. Biomechanics — why the level matters. Three properties make the Syme level functionally superior to a transtibial amputation when it heals. Energy expenditure: ambulation with a Syme increases energy cost by only 10 to 15 percent above normal gait, compared with 20 to 40 percent for a transtibial amputation — a difference that matters for elderly or dysvascular patients with limited cardiopulmonary reserve. Proprioception: the preserved natural heel pad, with its thick fibrous septa and fat lobules, compresses and distributes load uniformly across the distal tibial metaphysis and gives excellent sensory feedback. Lever arm: the Syme stump is a very long lever arm for the prosthesis, reducing the force the quadriceps and hip extensors must generate to control the limb in stance. Evidence summary. The highest-level summary is the systematic review of Braaksma and colleagues (2018), which confirmed the Syme level's superior energy efficiency over transtibial amputation and reported overall healing rates with predictors of success and failure. In the diabetic, infected subgroup the randomised work of Pinzur, Smith and Osterman (1995) established the two-stage modification as the standard of care by showing significantly lower stump infection and failure rates. Functional and satisfaction data (Morrison 2020; Slater 2024) confirm high satisfaction and end-bearing capacity, and inform modern prosthetic foot selection for the bulbous Syme stump.