Posterior Flap Hemipelvectomy: An Orthopaedic Masterclass in Pelvic Amputation

Introduction and Background

Despite the evolution of highly effective neoadjuvant chemotherapeutic regimens and sophisticated limb-sparing reconstructive techniques for the pelvis and hip, hindquarter amputation (hemipelvectomy) remains an essential, and often optimal, ablative surgical intervention. Primarily indicated for massive, multi-compartmental primary bone or soft-tissue sarcomas of the upper thigh, hip, or pelvis, this radical amputation also serves as a critical, life-saving maneuver for patients presenting with catastrophic pelvic trauma, uncontrollable lower extremity sepsis, or intractable palliation of fungating metastatic lesions.

Executing a hemipelvectomy demands an intimate, three-dimensional understanding of pelvic anatomy and a highly systematized surgical approach. The procedure carries significant intraoperative risks, primarily massive hemorrhage, and substantial postoperative morbidity. Early historical descriptions of hemipelvectomy correctly emphasized meticulous patient selection and aggressive, real-time volume resuscitation. Modern iterations of the procedure focus heavily on flap viability, oncologic margins, and postoperative rehabilitation.

Terminology and Classification of Hemipelvectomy

The nomenclature surrounding major pelvic amputations has historically been overly simplistic, leading to clinical confusion. Terms such as hindquarter amputation, interpelviabdominal amputation, and interinnominoabdominal amputation were previously used interchangeably. The advent of modern limb-salvage surgery necessitates a strict distinction between internal hemipelvectomy (preservation of the ipsilateral limb via pelvic resection) and external hemipelvectomy (true amputation). To avoid ambiguity, the Enneking/Dunham classification for pelvic resections should be utilized.

When discussing external hemipelvectomy, classification is dictated by the vascular pedicle and the tissue composition of the closing flap:

Posterior Flap Hemipelvectomy

This is the most common variant. It relies on a posteriorly based flap for closure.
* Classic Hemipelvectomy: Involves the complete amputation of the hemipelvis via disarticulation through the pubic symphysis anteriorly and the sacroiliac (SI) joint posteriorly. The common iliac vessels are divided. Closure is achieved with a posterior fasciocutaneous flap, as the gluteus maximus is devascularized and resected. This is typically reserved for massive tumors arising directly within the true pelvis.
* Modified Hemipelvectomy: Preserves the internal iliac (hypogastric) vessels and, specifically, the inferior gluteal artery. This permits the creation of a robust, vascularized myocutaneous posterior flap incorporating the gluteus maximus. The osteotomy is typically performed through the iliac wing or sciatic notch rather than the SI joint. It is the procedure of choice for massive thigh or hip tumors where limb salvage is contraindicated.

Alternative Flap Hemipelvectomies

• Anterior Flap Hemipelvectomy: Utilizes a myocutaneous pedicle flap based on the superficial femoral vessels and the anterior compartment of the thigh (quadriceps). It is indicated for tumors heavily involving the posterior buttock structures where a posterior flap is oncologically compromised.
• Extended Hemipelvectomy: Involves resection extending medially through the sacral ala and neural foramina, expanding the oncologic margin for tumors invading the SI joint.
• Compound Hemipelvectomy: Describes any hemipelvectomy requiring contiguous en bloc resection of visceral structures (e.g., bladder, rectum, prostate). Intraperitoneal approaches are often required for massive tumors filling the pelvic fossa.

Surgical Anatomy and Biomechanics

The anatomical density of the pelvis makes this procedure uniquely hazardous. The convergence of the gastrointestinal tract, genitourinary system, reproductive organs, and major neurovascular trunks within a rigid bony ring demands precise spatial awareness. Normal anatomical planes are frequently distorted by massive tumor volume or surrounding edema.

Osteology and Bony Landmarks

The pelvic ring functions as a load-bearing conduit between the axial skeleton and the lower extremities. Key osteotomies/disarticulations occur at the pubic symphysis, the SI joint, or the iliac wing. Intraoperative navigation relies heavily on palpable bony landmarks: the iliac crest, anterior superior iliac spine (ASIS), ischial tuberosity, and greater trochanter. Internally, the lumbosacral plexus is localized via the anterior SI joint, the sciatic nerve and gluteal vessels exit via the greater sciatic notch, and the urethra traverses inferior to the pubic symphysis.

Vascular Anatomy and Flap Perfusion

Vascular ligation dictates the functional classification of the amputation. The abdominal aorta bifurcates at L4, yielding the common iliac arteries, which further bifurcate at the S1 level into the external and internal iliac (hypogastric) arteries. The left-sided aorta dictates that the arterial tree remains anterior to the venous system throughout the pelvis.
* Classic Hemipelvectomy: Requires ligation of the common iliac artery/vein.
* Modified Hemipelvectomy: Requires precise identification and preservation of the internal iliac artery to maintain perfusion to the gluteus maximus via the inferior gluteal artery. Ligation of the common iliac in a classic hemipelvectomy deprives the posterior flap of muscular perfusion, relying solely on random-pattern fasciocutaneous supply, which drastically increases the rate of postoperative flap necrosis.

Pelvic Viscera and Gastrointestinal Tract

The bladder, urethra, and prostate (in males) lie in close proximity to the pubic symphysis. Catheterization with a large balloon is mandatory for intraoperative identification. The prostatic venous plexus is a source of massive, difficult-to-control hemorrhage. Ureters cross the iliac vessels from lateral to medial and must be actively protected; peristalsis aids in their identification. The sigmoid colon (during left-sided procedures) and the rectum must be mobilized and protected during the division of the pelvic floor (levator ani and coccygeus muscles).

Indications and Contraindications

Hemipelvectomy is an operation of magnitude and finality, reserved for scenarios where lesser resections would result in oncologic failure or systemic demise.

Unresponsive Sarcomas Involving Multiple Compartments

The primary indication is a nonmetastatic bone or soft tissue sarcoma (e.g., chondrosarcoma, osteosarcoma, pleomorphic sarcoma) that has failed neoadjuvant therapies or is too massive for limb-sparing surgery. Tumors involving the sciatic nerve and posterior buttock may necessitate an anterior flap hemipelvectomy, whereas massive anterior thigh tumors require a posterior flap.

Contamination of Surrounding Structures

Inappropriate, poorly planned biopsies or unplanned intralesional excisions ("whoops" procedures) can contaminate multiple anatomic compartments. Similarly, pathologic fractures of the proximal femur with massive hematoma tracking can contaminate vast tissue volumes, precluding safe limb salvage and necessitating amputation.

Nonviable Extremity Precluding Limb Salvage

Elderly patients with severe peripheral vascular disease, or patients with fungating, superinfected sarcomas, may not tolerate or heal from complex limb-sparing reconstructions. Additionally, very young, skeletally immature patients with massive tumors may be better served by hemipelvectomy to avoid the profound limb-length discrepancies and multiple revision surgeries associated with expandable endoprostheses.

Palliation and Nononcologic Indications

While rare, palliative hemipelvectomy may be indicated for intractable pain from lumbosacral plexus invasion, uncontrollable hemorrhage, or massive fungation in metastatic disease (e.g., solitary renal cell carcinoma metastasis). Nononcologic indications include catastrophic pelvic crush injuries, open hemorrhaging pelvic fractures, or chronic, life-threatening pelvic osteomyelitis/decubiti in paraplegic patients.

Preoperative Evaluation and Imaging

Rigorous staging and anatomic mapping are non-negotiable. Routine staging requires computed tomography (CT) of the chest and total body bone scintigraphy (or PET-CT) to rule out distant metastasis.

Advanced Imaging Modalities

• Standard Radiographs: Provide the baseline assessment of osseous destruction. Anteroposterior (AP) pelvis, Judet views, inlet, and outlet views are standard.
• CT and MRI: CT excels in defining cortical bone destruction, SI joint involvement, and visceral proximity (with oral/IV/rectal contrast). MRI is the gold standard for defining intramedullary tumor extent, soft tissue compartmental involvement, and neurovascular encasement.
• Angiography: Critical for flap planning. In older patients, silent aortoiliac atherosclerotic disease can compromise flap viability. Angiography delineates the common iliac bifurcation and allows for preoperative tumor embolization to mitigate catastrophic intraoperative blood loss.
• Venography: Indicated if there is clinical suspicion of venous obstruction or tumor thrombus (frequently seen in large pelvic chondrosarcomas), which must be managed meticulously to prevent fatal intraoperative pulmonary embolism.

Biopsy Principles

The biopsy tract must be considered contaminated and must be excised en bloc with the tumor. For posterior flap hemipelvectomies, the biopsy must be placed anteriorly or laterally, strictly avoiding the posterior gluteal tissues. The operating orthopedic oncologist must dictate the biopsy trajectory.

Preoperative Planning and Patient Positioning

Thorough mechanical bowel preparation and broad-spectrum perioperative antibiotics (covering aerobic skin and anaerobic bowel flora) are mandatory. The patient is placed in a "floppy lateral" or modified semisupine position. This allows the surgeon to dynamically roll the patient to access the anterior abdomen/retroperitoneum, the perineum, and the posterior gluteal region without re-draping.

Detailed Surgical Approach and Technique

The procedure is systematically executed in five distinct operative phases.

Phase 1: Anterior Retroperitoneal Approach

The procedure begins with an ilioinguinal incision. The abdominal musculature is detached from the iliac crest and the inguinal ligament. The peritoneum is bluntly swept medially to expose the retroperitoneal space. The ureter is identified and retracted medially with the peritoneum. The major vascular structures are isolated.
* For a Classic Hemipelvectomy, the common iliac artery and vein are doubly ligated and divided.
* For a Modified Hemipelvectomy, the internal iliac (hypogastric) artery is carefully preserved, and the external iliac artery and vein are ligated.
The psoas muscle and femoral nerve are then transected high in the pelvis.

Phase 2: Perineal Incision and Symphyseal Disarticulation

The incision is extended medially from the pubic tubercle, down the inferior pubic ramus toward the ischial tuberosity. The ischiorectal fossa is developed. A malleable retractor is placed behind the pubic symphysis to protect the bladder and the urethra (identified via the indwelling Foley catheter). The symphysis is divided using a heavy scalpel, osteotome, or cutting electrocautery.

Phase 3: Posterior Flap Elevation and Retrogluteal Exploration

The patient is rolled anteriorly. The posterior incision is made, extending from the posterior superior iliac spine (PSIS), along the iliac crest, down the greater trochanter, and curving posteriorly to join the perineal incision.
* In a Classic Hemipelvectomy, the gluteus maximus is resected with the specimen, leaving only a fasciocutaneous flap. The abdominal musculature is released completely to the paraspinal muscles, identifying the iliolumbar ligament as a guide to the superior SI joint.
* In a Modified Hemipelvectomy, the gluteus maximus is elevated off its insertion on the femur and reflected superiorly, preserving its vascular pedicle.

Phase 4: Detachment of Pelvic Floor Musculature

With the surgeon standing between the patient's abducted legs, the hip is manipulated (flexed and abducted) to place the pelvic floor under tension. The levator ani and coccygeus muscles are systematically clamped, ligated, and transected from anterior to posterior, moving from the pubic ramus toward the SI joint. The rectum is gently swept medially using a sponge-stick to prevent iatrogenic enterotomy.

Phase 5: Sacroiliac Disarticulation and Specimen Delivery

The final tethering structures are the anterior capsule of the SI joint and the lumbosacral nerve trunks. The SI joint is opened anteriorly using a broad osteotome. (Opening the joint posteriorly earlier in the case risks massive presacral venous plexus hemorrhage). The sacral nerve roots are sharply divided.
* If a Modified Hemipelvectomy is planned, an osteotomy is performed through the iliac wing, exiting at the greater sciatic notch, rather than disarticulating the SI joint.

Phase 6: Hemostasis, Drain Placement, and Closure

Following specimen extraction, meticulous hemostasis of the presacral and epidural veins is achieved. The psoas stump should be oversewn to prevent postoperative bleeding. Epineural catheters (e.g., Marcaine infusion pumps) are placed adjacent to the transected femoral nerve and lumbosacral plexus to mitigate phantom limb pain. Large-bore (28-gauge) chest tubes are placed to active suction. The myocutaneous or fasciocutaneous flap is rotated anteriorly and sutured to the abdominal wall fascia.

Pearls and Pitfalls in Surgical Management

Preoperative Optimization

• Hematologic: Correct chemotherapy-induced myelosuppression using erythropoietin and G-CSF. Ensure massive transfusion protocols are active; anticipate blood loss equal to 1-2 times the patient's total blood volume.
• Nutritional: Implement hyperalimentation in cachectic patients to optimize wound healing potential.

Intraoperative Execution

• Vascular Control: If the tumor encases major vessels, secure proximal control on the aorta or common iliacs immediately upon entering the retroperitoneum.
• Bowel Protection: A purse-string suture placed around the anus preoperatively minimizes intraoperative fecal contamination.

Postoperative Care

• Gastrointestinal: Prolonged retroperitoneal dissection and narcotic use guarantee a paralytic ileus. Maintain nasogastric decompression and strict NPO status for 5-7 days. Initiate total parenteral nutrition (TPN) early.
• Wound Care: Utilize compressive dressings (Ace wraps) over the stump to eliminate dead space. Retain surgical staples for a minimum of 3-4 weeks to prevent catastrophic wound dehiscence.

Complications and Management

Flap Necrosis

Ischemic necrosis of the posterior flap is the most devastating local complication, occurring in up to 50% of classic hemipelvectomies due to the reliance on random dermal perfusion after common iliac ligation. Modified hemipelvectomies drastically reduce this risk. Early recognition of demarcating necrosis requires aggressive surgical debridement and potential coverage with alternative flaps (e.g., vertical rectus abdominis myocutaneous [VRAM] flap).

Infection

Infection rates approximate 15%, driven by extensive dead space, proximity to the perineum, and systemic immunosuppression. Avoidance of retroperitoneal hematoma via large-bore suction drains is critical. Deep infections require radical debridement, washout, and prolonged targeted antimicrobial therapy.

Neurologic and Urologic Deficits

Division of the sacral plexus abolishes unilateral innervation to the bladder and genitalia, leading to transient bladder atony and impotence. Contralateral innervation typically compensates within 1 to 3 months. Post-void residual monitoring is required upon Foley removal.

Phantom Limb Sensation and Pain

Virtually all patients experience phantom limb sensation, which can be more debilitating than the physical loss of the limb. Multimodal analgesia, including perioperative regional nerve blocks, gabapentinoids, and early aggressive physiatry intervention, are standard of care.

Postoperative Rehabilitation and Outcomes

Functional recovery is heavily dependent on preoperative functional status, patient motivation, and early integration of physiatry. Ambulation begins early with a walker or crutches.

Once the wound is mature, patients are fitted for a hemipelvectomy prosthesis (typically a Canadian bucket-type socket). Patients who retain a portion of the iliac wing (modified hemipelvectomy) achieve superior prosthetic suspension and weight transfer compared to those with complete SI disarticulations. While prostheses require high energy expenditure—often relegating elderly or obese patients to wheelchair reliance—they provide essential truncal support, allow for prolonged standing, and free the upper extremities for activities of daily living. Long-term oncologic survivors frequently

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