Hindquarter Amputation (External Hemipelvectomy)

Indication. A malignant tumour of the pelvis or proximal thigh for which limb-salvage surgery cannot achieve a wide margin while leaving a functional limb, in a patient fit enough to survive the procedure. The vast majority are high-grade bone or soft-tissue sarcomas (osteosarcoma, chondrosarcoma, Ewing sarcoma, malignant peripheral nerve sheath tumour, large high-grade soft-tissue sarcomas) or, less often, a locally advanced recurrence. The clinical scenarios fall into three groups:

The key decision — limb salvage or amputation? Before offering a hindquarter amputation, confirm at the sarcoma MDT that an internal hemipelvectomy with limb reconstruction is not feasible. Limb salvage is preferred whenever a wide margin can be achieved with a functional limb. Amputation becomes the answer only when resecting the structures a functional limb depends on — both the principal artery and vein to the limb, or the sciatic and femoral nerves together with the acetabulum — would leave a dysvascular, insensate, flail extremity. Palliative cases bypass this test: symptom control is the goal. Pre-operative assessment. Treat this as a major physiological insult. - Staging and margins: high-resolution MRI of the pelvis for local extent and the compartments involved; CT chest (and whole-body imaging) for metastases; review the biopsy with the pathologist to confirm grade and margins; mark the biopsy tract so it is excised en-bloc.

• Plan the flap on the imaging: does the tumour involve the gluteal region and its vessels? If the buttock is clear, plan a posterior (gluteal) flap; if not, plan an anterior (quadriceps) flap. The flap choice dictates which vessels are preserved and which are divided.
• Systemic preparation: anaesthetic review, optimise cardiorespiratory and nutritional status, exclude distant disease; group-and-crossmatch a large volume of blood and arrange a cell saver; bowel preparation and mark a stoma site in case the pelvic viscera are involved.
• Counsel fully — the functional loss (the limb and the pelvic stability on that side), the long recovery, phantom and stump pain, the psychosocial impact, prosthetic options (often limited), and the realistic chance of cure versus palliation. Setup. Lateral or semilateral decubitus on a beanbag, secured but able to be tilted intra-operatively; the limb and pelvis are prepped free so they can be manipulated. Large-bore intravenous access, an arterial line, a central line, a urinary catheter and a cell saver are mandatory. A general anaesthetic with an epidural is typical, with antibiotics at induction. The whole team — surgeon, assistant, anaesthetist and scrub nurse — is briefed: this is a long, bloody operation.

The goal: remove the lower limb together with the ipsilateral hemipelvis as a single specimen, achieving a wide margin, while leaving durable soft-tissue cover and protecting the pelvic viscera. Two osteotomies — through the pubic symphysis anteriorly and the sacroiliac joint posteriorly — release the hemipelvis from the ring, after the iliac vessels have been controlled and the ureter, bladder and bowel protected. The flap (posterior gluteal by default) is then rotated over the defect.

Rehabilitation | Phase | Timing | Focus | Key actions | |-------|--------|-------|-------------| | 1 | 0 to 2 weeks | Medical stabilisation; flap and wound survival | ICU monitoring; flap checks; analgesia including a gabapentinoid; VTE prophylaxis; gentle log-rolling | | 2 | 2 to 6 weeks | Wound healing and early mobility | Drain removal as output settles; supervised sitting and transfers; protect the flap from shear | | 3 | 6 to 12 weeks | Strengthening and independence | Wheelchair mobility mastered; core and upper-limb conditioning; stump desensitisation | | 4 | 3 to 6 months and beyond | Prosthetic consideration | Stump maturation; trial of a hindquarter (tiltable) prosthesis if motivated and fit; many patients elect ongoing wheelchair use | Walking with a hemipelvectomy prosthesis is energetically very expensive, because the pelvis on that side is gone and the prosthesis must span from the trunk to the floor; a substantial proportion of patients function best with a wheelchair and are fully independent in it. Phantom-limb and stump pain are common and deserve early, aggressive, multimodal management. Psychological support and contact with other amputees are part of the treatment, not an optional extra. Complications

Epidemiology. External hemipelvectomy is a rare operation performed only in specialist sarcoma centres. Its frequency has fallen steadily as limb-salvage surgery — internal hemipelvectomy with allograft, endoprosthetic or saddle reconstruction — has become safer and more widely available, so it is now reserved for the minority of tumours that genuinely cannot be resected with the limb. Most candidates are adults with high-grade pelvic or proximal-thigh sarcomas, and outcomes depend overwhelmingly on histology, grade, the margin achieved and the presence of metastatic disease rather than on the amputation itself. Pathoanatomy — why limb salvage sometimes fails. The pelvis is a ring that transmits the femoral nerve and the external iliac vessels into the lower limb and the sciatic nerve out through the greater sciatic notch. A tumour that encases the external iliac or femoral vessels, or the sciatic and femoral nerves, or that destroys the acetabulum and crosses compartments, cannot be excised with the limb intact while preserving a functional extremity. Resecting both the principal artery and vein, or both major nerves, leaves a dysvascular or anaesthetic limb that is a liability rather than an asset. In those patients, removing the limb with the hemipelvis gives the best chance of local control and a functional — if prosthetically demanding — outcome. Contrast with internal hemipelvectomy. Internal hemipelvectomy excises all or part of the hemipelvis for tumour but preserves the limb, reconstructing the pelvic ring or the hip as needed. It is the limb-salvage counterpart and the default whenever margins allow. The Enneking classification of pelvic resections — by the region resected — frames both operations.

A standard external hemipelvectomy therefore corresponds to an Enneking Type I plus II plus III resection performed with the limb, and the posterior cut is taken through the sacroiliac joint (becoming Type IV only if the tumour extends into the sacrum). Recognising this framework lets you discuss the operation in the language examiners use for pelvic oncology.