Limb Salvage Surgery Principles

The Enneking surgical staging system is the most widely used classification for musculoskeletal tumours. It combines grade, compartmental status and metastases into a stage that guides both treatment and prognosis: the stage tells you the margin required and whether adjuvant therapy is needed.

Compartments. A tumour is intracompartmental (T1) while it stays within its anatomical compartment with the cortex intact, and extracompartmental (T2) once it has breached the cortex or extended into the soft tissues.

Benign tumours are staged too. Enneking's three benign stages run from latent to aggressive, and a stage 3 lesion may need margins similar to a low-grade malignancy:

• Stage 1 (latent) - static and asymptomatic, e.g. fibrous cortical defect
• Stage 2 (active) - symptomatic and growing, e.g. aneurysmal bone cyst
• Stage 3 (aggressive) - locally destructive, e.g. giant cell tumour

The Enneking margin classification names the plane of dissection relative to the tumour and its reactive zone, and local recurrence follows the margin directly. An intralesional margin, curettage through the tumour, contaminates the field and is acceptable only for benign lesions; wide is the minimum for sarcoma; radical, the whole compartment, is rarely performed now.

What a wide margin means in practice. The cuff is defined tissue by tissue:

• Bone - a minimum of 2cm beyond the tumour extent on MRI
• Soft tissue - a cuff of normal tissue, an uninvolved fascia or muscle layer
• Neurovascular bundle - the adventitia can be included if the vessels are not encased
• Joint - intra-articular resection if ligament involvement is suspected

Planned and achieved. The planned margin is the surgical intent; the achieved margin is what the pathologist confirms. A close margin, under 1mm, goes back to the MDT and may need adjuvant radiotherapy.

The American Joint Committee on Cancer (AJCC) system is used in some centres, more commonly for soft tissue sarcoma; Enneking remains the preference for bone sarcoma. Both incorporate grade and extent, and Enneking adds compartmental status, which is what matters surgically. The AJCC components:

• T - tumour size, T1 under 8cm and T2 over 8cm
• N - regional lymph nodes, rare for sarcoma
• M - distant metastases
• G - grade 1-3

How a bone sarcoma presents. Pain that is progressive, worse at night and not relieved by rest, over weeks to months. A palpable mass is present in 50%, and 5-10% present with a pathological fracture. The features that should raise the suspicion of malignancy:

• Night pain
• Progressive pain not responding to simple analgesia
• A mass increasing in size
• Constitutional symptoms, weight loss and fatigue
• Age-size mismatch, a large lesion in a young patient

Examination. Look at the mass, its location, size and any skin change, and at the limb for muscle wasting, length discrepancy and angular deformity. Palpate for size, consistency, mobility and tenderness and for the relation of the mass to the underlying bone, then check the neurovascular status distally. Examine the range of motion of the adjacent joints, the neurovascular examination in full because a tumour may compress or invade, and the lymph nodes, unusual for bone sarcoma but checked.

What the MDT decides. The team confirms the diagnosis, determines the stage, plans neoadjuvant therapy, decides between salvage and amputation, chooses the reconstruction and sets the follow-up protocol. Its essential members:

• Orthopaedic oncologist
• Medical oncologist
• Radiation oncologist
• Musculoskeletal radiologist
• Histopathologist
• Specialist nurse

Setting the margin. The plan is made on the MRI:

1. Review the MRI with the radiologist
2. Measure the intramedullary extent
3. Add a minimum of 2cm to the tumour extent to set the bone cut level
4. Plan the soft tissue cuff along the fascial planes
5. Assess neurovascular involvement

Whether the joint survives. Add the distance from the tumour edge to the joint line to the bone cut you have planned, and you know whether the joint can be preserved (an intercalary resection) or must be resected with the tumour (an articular resection). Joint preservation improves function when it is oncologically safe.

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Choosing the reconstruction. The factors that decide it:

• Patient age and growth potential
• Tumour location and the extent of resection
• Expected functional demands
• Available bone stock
• Soft tissue coverage
• Surgeon experience and resources

Planning the prosthesis. Custom or modular; sized from the imaging measurements; stem length and fixation type; and the constraint the joint will need.

Chemotherapy for osteosarcoma. Neoadjuvant chemotherapy is the standard of care and has improved overall survival from 20% to 65-70%. It treats micrometastatic disease, reduces the size of the tumour, which may enable limb salvage, and grades the tumour's response, which is prognostic. The standard protocol is MAP:

• Methotrexate, high-dose with leucovorin rescue
• Adriamycin (doxorubicin)
• Cisplatin (platinum)

Timing. Neoadjuvant chemotherapy runs for 10-12 weeks, surgery follows its completion, and adjuvant chemotherapy continues post-operatively.

Radiotherapy for soft tissue sarcoma. An adjunct to surgery, given pre-operatively (50Gy) or post-operatively (60-66Gy), it reduces local recurrence from 30% to 10-15%. For bone it is not standard in osteosarcoma, which is chemo-sensitive; it is considered for Ewing sarcoma, which is radiosensitive, and for close margins where re-excision is not possible.

The decision. Limb salvage is appropriate when:

• A wide margin is achievable
• The major neurovascular bundle is not encased, and the neurovascular structures are preserved or reconstructible; major vessel reconstruction is possible if needed
• The reconstruction is technically feasible, an appropriate reconstruction is available, and there is adequate soft tissue for coverage
• The expected functional outcome exceeds amputation
• The patient understands and accepts the risks and complications

When amputation is the better operation. The relative indications:

• Neurovascular encasement requiring sacrifice of the bundle
• Pathological fracture with haematoma contamination; a fracture without haematoma spread, where margins remain feasible, favours salvage
• Extensive skip metastases; salvage may still be possible if all are resectable
• Extensive soft tissue extension precluding reconstruction
• Infection compromising the reconstruction
• A very young child facing an extensive resection
• An expected flail, insensate or painful limb, or a functional outcome from salvage worse than amputation
• Patient factors: age, comorbidities and expectations, or a preference for a definitive procedure and the needs of an active lifestyle

The workhorse. Modular endoprosthetic reconstruction is the most common reconstruction for periarticular tumours, at the distal femur, proximal tibia, proximal femur and proximal humerus, and the choice whenever immediate stability and early mobilisation are required. It gives immediate stability and weight bearing without donor site morbidity, predictable outcomes, and a modular system that can be customised. The price is mechanical complications, loosening and breakage, infection, a limited lifespan of 70-80% survival at 10 years, and multiple revisions likely in a young patient.

Distal femoral replacement, step by step.

1. Incision - extensile anterior or medial approach, excising the biopsy track
2. Tumour resection - wide margin including a cuff of normal muscle
3. Bone cut - at the level planned from the MRI
4. Canal preparation - ream to accept a cemented or press-fit stem
5. Prosthesis assembly - the modular system allows length adjustment
6. Soft tissue reconstruction - medial gastrocnemius flap for coverage
7. Extensor mechanism - suture the quadriceps to the prosthesis if needed
8. Closure - layered, over a drain

Technical points. Avoid stripping soft tissue beyond the resection margins. A gastrocnemius flap is essential for coverage at the proximal tibia. Most tumour prostheses use a constrained hinge, and hydroxyapatite collars may improve soft tissue attachment.

Osteoarticular allograft. Replaces the joint with a biological articular surface, and is rarely used now because of its complication rates: cartilage degeneration is universal at 10 years, fracture occurs in 20-25% and nonunion in 15-20%, and infection runs at a rate similar to an endoprosthesis.

Intercalary allograft. For diaphyseal defects where the joints can be preserved, combined with internal fixation by plate or nail. It is a biological reconstruction with the potential to incorporate and it preserves both adjacent joints, but nonunion runs at 15-25% and fracture at 15-20%, healing is prolonged, and weight bearing is protected for 6-12 months.

Allograft-prosthetic composite (APC). Combines biological bone stock with a prosthetic joint and gives the soft tissues an allograft to attach to, which is why it is particularly useful at the proximal femur and proximal humerus. The prosthesis is cemented into the allograft off the table, the composite is implanted and fixed to host bone, and the tendon attachments are sutured to the allograft. Beyond better soft tissue attachment than a prosthesis alone, it leaves bone stock for future revision and may reduce dislocation through attachment of the greater trochanter.

Vascularised fibular graft. Living bone with its own blood supply, taken on the peroneal artery as a pedicled or free graft. It suits intercalary defects that preserve both joints, can be combined with an allograft as a dual-strut construct, and keeps its growth potential in children. It remodels and hypertrophies and carries a low infection risk; against that stand technically demanding microsurgery, prolonged protection while it hypertrophies over 1-2 years, size mismatch in a large defect, and donor site morbidity. The graft is inset into the medullary canal or laid alongside the allograft, anastomosed to local vessels, and combined with a plate or external fixation.

Distraction osteogenesis. For intercalary defects, particularly in children, and an alternative to bone transport: a ring fixator, a corticotomy at the appropriate level and gradual lengthening at 1mm a day, over months of treatment.

Who needs one. The skeletally immature patient with a periarticular tumour whose expected limb length discrepancy is greater than 2-3cm.

The designs. Three types, differing in how much surgery each lengthening needs:

• Non-invasive expandable - lengthened electromagnetically from outside the limb, in clinic or radiology, with no additional surgery for lengthening; the STANMORE and Repiphysis systems are examples
• Minimally invasive - a small incision reaches the lengthening mechanism, less surgery than the traditional types
• Traditional (modular replacement) - an operation for each lengthening, with a higher complication rate

What to tell the family. 15-20 lengthening procedures may be needed, each carrying its own risk, and the overall complication rate is 50-70% over childhood; the failure modes are infection, fracture and mechanism failure. Modern non-invasive designs reduce the interventions but do not eliminate them. Rotationplasty is the alternative to put beside it, a single procedure with excellent function and significant body image concerns, and both options are discussed thoroughly with the family.

The Van Nes rotationplasty. The tumour-bearing segment of distal femur or proximal tibia is resected, the remaining distal limb is rotated 180 degrees, and the foot, now facing posteriorly, fits into a prosthesis with the ankle working as the "knee". It is offered for distal femoral or proximal tibial tumours in children, as the alternative to an above-knee amputation and to the repeated procedures of a growing prosthesis.

What it offers. A biological reconstruction in living tissue with growth potential preserved and no implant-related complications, in a single definitive procedure; the ankle provides a powered "knee". Function is superior to an above-knee amputation and equivalent or better than a tumour prosthesis in young patients, with return to high-level activities including sport and MSTS scores typically 80-90%.

What it costs. The cosmetic appearance of the backward-facing foot and the psychological adjustment it demands, which can be challenging for some patients, particularly adolescents. It needs a highly motivated patient and family and is not universally accepted culturally; many patients nevertheless prefer its functional advantages to the complications of limb salvage or the limitations of amputation.

Five ways a tumour prosthesis fails. The Henderson classification sorts endoprosthetic failure into five types and is the frame for any account of the complications. Reoperation for any cause runs at 30% at 10 years, and patients are counselled about it before consent.

Reading the table. The most common Type 1 failure is the extensor mechanism at the proximal tibia. Type 2 loosening is progressive and presents with pain and a radiographic lucency; Type 3 risk increases with time and with the patient's activity level.

Why it is so much commoner. Deep infection after a tumour endoprosthesis is much higher than the 1-2% seen after primary arthroplasty, and the reasons lie in the operation itself:

• A large dead space after resection
• Chemotherapy-induced immunosuppression, which also impairs healing
• Radiotherapy fibrosis of the soft tissues
• Prolonged surgery
• Poor soft tissue coverage
• Metalwork and allograft, which are foreign bodies

How it presents and what to do. Acute infection presents with wound breakdown, fever and sepsis; chronic infection with persistent pain and a sinus. Early infection with a stable implant can be treated by DAIR (debridement, antibiotics, implant retention); chronic infection with biofilm needs a two-stage revision; amputation follows a failed two-stage revision or uncontrollable sepsis.

Periprosthetic fracture. Stress risers, poor bone quality and trauma are the risk factors; treatment is ORIF, with stem revision if the stem is loose.

Aseptic loosening. Presents with activity-related pain. Press-fit stems may loosen earlier; cemented stems are more predictable initially.

Implant breakage. At the hinge mechanism, the stem or the modular junctions, and it may present with sudden instability. Modern designs have improved it.

Extensor mechanism failure. The particular problem of proximal tibial resection, where the patellar tendon has to be reattached to the prosthesis and fails at the rate in the Henderson table. Consider a gastrocnemius rotational flap.

Hip dislocation. After proximal femoral resection; reduced by reconstruction of the greater trochanter with an APC, and managed with a constrained liner if recurrent.

Neurovascular injury. The peroneal nerve is at risk in proximal tibial resection.

Local recurrence. Occurs at the rates set out in the margin table, wide margins at one end and marginal or contaminated margins at the other. Re-stage locally and distantly, re-resect if feasible, amputate if margins cannot be achieved, and palliate if the disease is metastatic.

Global Epidemiology

Primary bone sarcomas are rare worldwide, with osteosarcoma the commonest primary bone malignancy. Large registry analyses (SEER) historically described a bimodal age distribution, but contemporary US data (Kar et al., J Bone Oncol 2024) show the incidence is now unimodal, with a single consistent peak in the second decade of life and no reproducible second peak in older adults (DOI). National-population datasets from high-income settings show low absolute case numbers; Australian national figures report approximately 200 new bone sarcomas annually, with osteosarcoma accounting for roughly one-third. The distal femur remains the single commonest site requiring limb salvage globally.

Guideline Comparison

International guidelines are highly concordant: centralised care in a specialist sarcoma centre, multidisciplinary team (MDT) decision-making, image-guided core biopsy with track excision, and limb salvage with wide margins whenever oncologically safe.

The ESMO-EURACAN-GENTURIS-PaedCan bone sarcoma guideline (Strauss et al., Ann Oncol 2021) is the most comprehensive international standard, recommending referral to a reference centre before biopsy, neoadjuvant MAP chemotherapy for high-grade osteosarcoma, and wide surgical margins (DOI).

Registry & Access Considerations

The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) primarily captures primary and revision arthroplasty; tumour endoprostheses are a distinct subset whose higher revision rates reflect salvage surgery in young patients facing life-threatening disease. For global interpretation, long-term tumour endoprosthesis data are therefore drawn mainly from high-volume sarcoma-centre series (e.g. the Royal Orthopaedic Hospital cohorts) rather than national arthroplasty registries.

Treatment protocols are globally aligned around neoadjuvant MAP chemotherapy and wide resection; the MAP agents (methotrexate, doxorubicin, cisplatin) are widely available in high-income settings. Access for regional and remote patients can carry substantial travel burdens, which strengthens the case for single-procedure options such as rotationplasty where appropriate.

Differential Diagnosis