Allograft Reconstruction after Bone Tumour Resection

Surgical Indications

Absolute Indications

• Diaphyseal or intercalary segmental defect after wide resection of bone sarcoma (osteosarcoma, Ewing sarcoma, chondrosarcoma) in a patient younger than 40-50 years who desires biologic reconstruction and restoration of bone stock
• Osteoarticular defect requiring joint surface and ligament reconstruction (proximal tibia, distal femur, proximal humerus) when the patient is young and high-demand
• Need for tendon or ligament attachment sites that cannot be achieved with a megaprosthesis (patellar tendon, hip abductors, rotator cuff)
• Patient preference for allograft after informed discussion of risks versus endoprosthetic reconstruction

Relative Indications

• Allograft-prosthesis composite (APC) when the joint surface is not reconstructible with osteoarticular allograft but soft-tissue attachment is still desired
• Revision of failed megaprosthesis where bone stock restoration is required for future longevity
• Aggressive benign tumours (giant cell tumour, chondroblastoma) with massive bone loss after curettage and resection

Contraindications

Absolute:

• Active infection at the resection site
• Inability to achieve wide surgical margins
• Patient non-compliance with prolonged protected weight-bearing (minimum 6 months)
• Severe immunocompromise or uncontrolled diabetes with high infection risk

Relative:

• Age greater than 60-65 years (megaprosthesis usually preferred for faster rehabilitation)
• Requirement for post-operative radiation (increases nonunion and fracture risk)
• Smoking or poor soft-tissue envelope that cannot be optimised

Evidence for Allograft Reconstruction

Structural Allograft Outcomes

• Fresh-frozen structural allografts achieve union in 60-80 percent of host-graft junctions when rigid fixation and autograft augmentation are used
• Osteoarticular allografts have higher complication rates (fracture, joint degeneration) than intercalary grafts but preserve the option for biologic joint reconstruction in young patients
• Allograft-prosthesis composites combine the advantages of both techniques and are particularly useful in the proximal tibia where patellar tendon reattachment is critical

Comparison with Megaprosthesis

• Megaprosthesis provides immediate stability and faster return to weight-bearing (6-12 weeks) but sacrifices bone stock and future revision options
• Allograft reconstruction offers superior long-term bone stock and the possibility of tendon/ligament attachment but requires 6-18 months of protected weight-bearing and carries a 20-40 percent major complication rate in the first two years
• In patients younger than 40 years with diaphyseal defects, many centres favour allograft or allograft-prosthesis composite when the soft-tissue envelope allows

Key Evidence

Relevant Anatomy for Allograft Reconstruction

Host-Graft Junction Biology

The success of structural allograft reconstruction depends on understanding that the graft is avascular. Union occurs by creeping substitution — host vessels and osteoblasts invade the graft from the junction, resorbing and replacing necrotic bone over months to years. The central portion of a long intercalary graft may remain avascular indefinitely.

Fixation Principles

• The fixation construct must span both host-graft junctions with sufficient working length on the host bone (minimum two cortical diameters) to resist bending and torsional forces during the prolonged healing period.
• Compression at the junction is achieved with lag screws or compression plating; any gap greater than 1 mm dramatically increases nonunion risk.
• When an intramedullary nail is used, it must be locked proximally and distally and the junctions must still receive supplemental plate or cerclage compression if possible.

Soft-Tissue Considerations

• The soft-tissue envelope after tumour resection is often compromised by the resection itself and by adjuvant therapy.
• Muscle flaps (gastrocnemius, soleus, latissimus) are frequently required to cover the allograft and provide a vascularised bed.
• Tendon reattachment (patellar tendon, hip abductors, rotator cuff) must be performed with heavy non-absorbable suture through drill holes or through the preserved soft-tissue sleeve on the allograft.

Osteoarticular Allograft Specifics

• Joint surface matching is critical — the donor must be size-matched on pre-operative CT and the articular cartilage must be preserved during implantation.
• Ligament reconstruction follows principles similar to revision arthroplasty or multi-ligament knee reconstruction.
• The joint capsule and ligaments are sutured to the corresponding structures on the allograft under appropriate tension.

Positioning and Preparation

Patient position: Supine on a radiolucent table with the entire limb prepared and draped free. A tourniquet is usually not used because of the length of the procedure and the need for proximal exposure. A bump under the ipsilateral buttock facilitates lateral access if needed.

Pre-operative planning: Size-matched fresh-frozen allograft is ordered from an accredited tissue bank after CT templating of both the defect and the contralateral limb. The graft is thawed in warm saline on the morning of surgery and cultured. Autograft is harvested from the iliac crest or obtained from reamings if an IM nail is used.

Consent: Discuss nonunion (10-30 percent), fracture (5-15 percent), infection (5-15 percent), disease transmission (less than 1 in 1 million), prolonged protected weight-bearing (6-18 months), and the possibility of graft removal and revision to megaprosthesis or amputation if complications occur.

Operative Steps — Intercalary Allograft (Distal Femur Example)

Step 1: Wide Resection

Perform the planned wide resection of the bone tumour through the appropriate approach (anterolateral femoral shaft or medial parapatellar as indicated). Obtain frozen section confirmation of margins. Measure the defect length and diameter precisely. Protect the neurovascular bundle throughout.

Step 2: Allograft Preparation

On the back table, trim the thawed allograft to the exact length required with an oscillating saw under irrigation. Create step-cut or oblique ends to increase surface area and rotational stability at the junctions. Drill any planned screw holes or tendon attachment sites before implantation. Culture the graft.

Step 3: Host-Graft Junction Preparation

Freshen the host bone ends with a saw to bleeding bone. If an IM nail is planned, ream the host canal to accept the largest possible nail. If plate fixation is used, contour the plate(s) to the host and graft before final insertion.

Step 4: Graft Insertion and Fixation

Insert the graft and achieve compression at both junctions. Apply the spanning fixation construct (dual compression plates in different planes or locked IM nail with supplemental plate). Confirm that at least two cortical diameters of host bone are engaged on each side. Impact autograft around both junctions.

Step 5: Soft-Tissue and Tendon Reconstruction

Reattach any resected tendons or ligaments to the allograft using heavy non-absorbable suture through drill holes. If a muscle flap is required, perform or coordinate the flap coverage before closure. Close the wound over drains with meticulous haemostasis.

Step 6: Intra-operative Assessment

Obtain intra-operative radiographs to confirm alignment, fixation length and junction compression. Check that the limb is stable through a full range of motion and that any joint reconstruction is congruent.

Osteoarticular Allograft Specific Considerations

• Joint surface matching is confirmed on the back table before implantation.
• Ligament and capsule reconstruction is performed under appropriate tension with the knee or shoulder in the reduced position.
• For proximal tibial osteoarticular allograft, the patellar tendon is reattached to the allograft tibial tubercle with transosseous sutures or anchors.

Allograft-Prosthesis Composite (APC) Technique

When the joint surface cannot be reliably reconstructed with osteoarticular allograft, a cemented prosthesis is implanted into the allograft on the back table. The composite is then fixed to the host bone with the same junction principles. The patellar tendon or other soft tissues are attached to the allograft portion of the composite.

Post-operative Protocol

Early Phase (Day 0-6 weeks)

• Protected weight-bearing: Touch-down or partial weight-bearing (10-20 kg) with crutches or walker for minimum 6 weeks, often 3-6 months depending on radiographic progress
• Wound care: Drains removed at 48 hours; monitor closely for erythema or drainage; early plastic surgery input if flap compromise suspected
• Antibiotics: 24-48 hours of IV antibiotics; extend if chemotherapy-induced neutropenia or flap coverage performed
• DVT prophylaxis: Mechanical and pharmacologic prophylaxis for the duration of restricted weight-bearing
• Range of motion: Begin gentle active-assisted ROM immediately; avoid aggressive stretching across the junctions

Union Monitoring

• Serial radiographs at 6 weeks, 3 months, 6 months, 9 months, 12 months and then every 6 months until union
• CT scan if plain radiographs are equivocal at 9-12 months
• Union defined as bridging callus on two orthogonal views without radiolucent line at either junction
• Continue protected weight-bearing until union confirmed

Return to Function

• Full weight-bearing: Once radiographic union achieved (typically 6-18 months)
• Strengthening: Progressive resistance exercises once full weight-bearing allowed
• Return to sport: Generally discouraged for high-impact activities; low-impact activities (swimming, cycling) may be permitted after union
• Surveillance: Continue oncologic follow-up with local and systemic imaging per protocol

Special Case: Allograft-Prosthesis Composite (APC)

Indications and Advantages

APC is chosen when the joint surface cannot be reliably reconstructed with osteoarticular allograft but the surgeon still desires biologic tendon attachment. The cemented prosthesis is implanted into the allograft on the back table, then the composite is fixed to the host with the same junction principles.

Post-operative Differences

• Immediate stability of the prosthetic joint allows earlier protected weight-bearing than osteoarticular allograft
• Tendon reattachment to the allograft portion still requires protection until soft-tissue healing (6-12 weeks)
• Long-term surveillance for both prosthetic loosening and host-graft junction union is required

Special Case: Managing Nonunion

Decision Making

Nonunion is declared only after 12 months (or 18 months in patients who received chemotherapy or radiation) with no radiographic progress. Low-grade infection must be excluded by aspiration or biopsy before revision.

Revision Strategy

• Revision compression plating with autograft (iliac crest or vascularised fibula)
• Exchange nailing with compression and autograft if IM nail was used initially
• Consider bone stimulator or anabolic agents (teriparatide) in recalcitrant cases
• If multiple revisions fail or infection is present, convert to megaprosthesis or consider amputation