Comprehensive pre-operative imaging including pelvic MRI and CT angiogram. NPO for at least 8 hours. Blood product cross-matching and optimization of hemoglobin levels. Administration of prophylactic intravenous antibiotics and deep vein thrombosis prophylaxis. Informed consent regarding potential neurological or vascular deficits.
Immediate post-operative care in the Intensive Care Unit for hemodynamics monitoring. Strict pain management protocol including regional blocks or patient-controlled analgesia. Early physical therapy assessment and wound drainage management. Gradual weight-bearing protocol as directed by orthopedics and long-term rehabilitation.
Internal Hemipelvectomy: A Comprehensive Clinical Guide
Internal hemipelvectomy, also referred to as a periacetabular resection or pelvic internal hemipelvectomy, represents one of the most complex and radical orthopedic oncology procedures. Unlike a classic (external) hemipelvectomy, which involves the amputation of the lower extremity along with a portion of the hemipelvis, an internal hemipelvectomy preserves the limb while achieving a wide oncological resection of the pelvic ring.
This procedure requires a multidisciplinary approach, often involving orthopedic oncologists, vascular surgeons, plastic surgeons, and neurosurgeons. The primary objective is to achieve negative surgical margins (R0 resection) for malignant tumors involving the pelvis while maintaining functional ambulation.
1. Technical Specifications and Mechanism
The pelvic ring is an anatomically dense region containing vital neurovascular structures, viscera, and complex musculature. An internal hemipelvectomy involves the en bloc removal of all or part of the innominate bone.
Anatomical Zones of Resection
The procedure is generally categorized by the Enneking and Dunham classification system, which divides the pelvis into three zones:
* Zone I: The ilium (supra-acetabular).
* Zone II: The periacetabular region (the joint itself).
* Zone III: The pubis and ischium (infra-acetabular).
The Reconstruction Mechanism
Once the tumor is resected, the structural integrity of the pelvis must be restored. Because the pelvic ring is a weight-bearing structure, the reconstruction strategy depends on the zone resected:
1. Zone I Resection: Often requires iliac wing reconstruction using allograft or mesh to anchor the abductor muscles.
2. Zone II Resection: The most challenging, requiring reconstruction of the hip joint. Options include:
* Endoprosthetic Reconstruction: Custom 3D-printed metallic implants.
* Allograft-Prosthetic Composite (APC): Combining a massive bone allograft with a total hip arthroplasty.
* Saddle Prosthesis: A modular implant that "sits" on the remaining ilium.
* Biological Reconstruction: Utilizing vascularized fibular grafts or massive structural allografts.
2. Clinical Indications and Usage
Internal hemipelvectomy is reserved for patients where limb salvage is oncologically feasible and expected to result in better function than an amputation.
| Indication Category | Specific Conditions |
|---|---|
| Primary Bone Malignancies | Chondrosarcoma (most common), Osteosarcoma, Ewing Sarcoma. |
| Soft Tissue Sarcomas | High-grade Leiomyosarcoma, Undifferentiated Pleomorphic Sarcoma (UPS). |
| Metastatic Disease | Selected cases of solitary pelvic metastases with impending or pathological fracture. |
| Aggressive Benign Tumors | Giant Cell Tumor (GCT) of the bone, aggressive Desmoid tumors. |
Patient Selection Criteria
- Oncological: Absence of distant metastasis (in primary cases) and feasibility of obtaining wide surgical margins.
- Anatomical: The tumor must not involve the sciatic nerve or external iliac vessels in a way that precludes reconstruction or function.
- Physiological: The patient must be able to withstand a prolonged surgery (often 8–14 hours) and significant blood loss.
3. Pre-Operative Preparation
Preparation is intensive and requires a "Team-Based" surgical strategy.
Imaging Protocol
- MRI (Pelvis): To assess soft tissue extent and neurovascular involvement.
- CT (Pelvis/Chest/Abdomen): To assess bone destruction and rule out distant metastases.
- 3D Modeling: Pre-operative 3D printing of the patient’s pelvis is now standard to design custom cutting guides and implants.
Pre-Op Optimization
- Vascular Mapping: Angiography to identify the blood supply to the limb and tumor.
- Nutritional Support: High-protein diet and correction of anemia.
- Interventional Radiology: Embolization of the tumor’s feeding vessels 24–48 hours prior to surgery to minimize intraoperative hemorrhage.
4. The Surgical Procedure: Step-by-Step
- Positioning: Patient is typically placed in a lateral decubitus or semi-lateral position, depending on the tumor location (anterior vs. posterior).
- Incision: Large, utility-type incisions (e.g., Ilioinguinal, Smith-Petersen, or posterior "flaps") are used to maximize exposure.
- Dissection: Careful mobilization of the femoral, sciatic, and obturator nerves. The external iliac vessels are carefully retracted.
- Osteotomy: Using custom-made 3D cutting guides, the bone is cut at pre-planned margins.
- Resection: The tumor is removed en bloc.
- Reconstruction: The pelvic ring is stabilized using the chosen implant or graft. Soft tissue coverage is vital, often requiring a rotational flap (e.g., rectus abdominis or tensor fascia lata) to cover the dead space.
- Closure: Multi-layered closure with drains to prevent hematoma formation.
5. Post-Operative Recovery and Protocol
Recovery is measured in months, not weeks.
- Phase 1 (Days 1–7): Intensive Care Unit (ICU) monitoring, strict fluid management, and early mobilization of the non-operated limbs.
- Phase 2 (Weeks 2–6): Wound care, physical therapy (non-weight bearing on the affected side), and DVT prophylaxis.
- Phase 3 (Months 2–6): Gradual weight-bearing as determined by radiographic union of the grafts or stability of the implants.
- Phase 4 (Months 6+): Gait training, strengthening of the core and abductors.
6. Risks, Complications, and Contraindications
Potential Complications
- Infection: One of the most severe risks due to the size of the wound and deep tissue dissection (rates range from 10% to 25%).
- Neurovascular Injury: Permanent foot drop (sciatic nerve injury) or vascular compromise leading to limb ischemia.
- Implant Failure: Loosening, breakage, or dislocation of the pelvic prosthesis.
- Wound Dehiscence: Common due to the tension on large skin flaps.
- Massive Hemorrhage: Despite embolization, blood loss can exceed 2–5 liters.
Contraindications
- Involvement of the neurovascular bundle (e.g., tumor encasing the common iliac artery/vein).
- Poor soft tissue envelope (e.g., previous radiation therapy).
- Presence of metastatic disease that makes local control futile.
- Severe medical comorbidities (ASA physical status IV).
7. Alternative Treatments
When internal hemipelvectomy is not indicated, the alternative pathways include:
1. External Hemipelvectomy (Hindquarter Amputation): Necessary if the tumor involves the neurovascular bundle or if wide margins cannot be achieved otherwise.
2. Palliative Radiation/Chemotherapy: For patients who are not surgical candidates or have systemic disease.
3. Radiofrequency Ablation (RFA) / Cryoablation: For small, symptomatic lesions in patients who cannot tolerate major surgery.
8. Frequently Asked Questions (FAQ)
1. Is an internal hemipelvectomy the same as a hip replacement?
No. A hip replacement (total hip arthroplasty) removes the femoral head and acetabulum. An internal hemipelvectomy removes a large portion of the pelvic bone itself, requiring complex reconstruction of the pelvic ring.
2. Will I be able to walk again?
Most patients regain the ability to walk, though many require assistive devices (crutches or a cane) permanently, and some may have a persistent limp.
3. How long does the surgery last?
It is a major undertaking, typically lasting between 8 to 14 hours depending on the complexity of the reconstruction.
4. What is the most common tumor treated this way?
Chondrosarcoma is the most frequent indication, as it is often resistant to chemotherapy and requires wide surgical margins for local control.
5. Why is the risk of infection so high?
The pelvis is deep in the body, and the surgery creates a large "dead space" that is prone to fluid collection. Additionally, extensive soft tissue dissection compromises the blood supply to the overlying skin.
6. Do I need chemotherapy after the surgery?
This depends on the pathology. Osteosarcoma and Ewing Sarcoma patients typically require adjuvant chemotherapy, whereas Chondrosarcoma patients generally do not.
7. What happens to the nerves in the pelvis?
The sciatic nerve is the most vulnerable. Surgeons spend hours performing "nerve-sparing" dissection to ensure the patient maintains sensation and motor function in the leg.
8. Can I have an MRI after the reconstruction?
Yes, but the metallic implants may create artifacts on the MRI, which can make follow-up imaging for local recurrence more challenging. CT or PET scans are often preferred.
9. How long is the hospital stay?
Typically, patients remain in the hospital for 10 to 21 days, followed by inpatient or intensive outpatient rehabilitation.
10. What is the survival rate?
Survival is primarily determined by the tumor pathology and the presence of metastases, rather than the surgery itself. In localized disease, 5-year survival rates for high-grade sarcomas are significantly improved by achieving a wide surgical margin.
9. Conclusion
Internal hemipelvectomy remains a high-stakes, high-reward procedure. It represents the pinnacle of orthopedic oncology, balancing the aggressive nature of pelvic malignancies with the patient's desire for limb salvage and quality of life. While the recovery is rigorous and the complication profile is significant, the evolution of 3D-printed implants and refined surgical techniques continues to improve patient outcomes, making this procedure a viable and life-saving option for many.
Disclaimer: This guide is for educational purposes only and does not constitute medical advice. Surgical decisions should always be made in consultation with a board-certified orthopedic oncologist in a specialized tertiary center.