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Endoprosthetic Reconstruction (Tumour Megaprosthesis)

Surgical technique guide for modular endoprosthetic replacement after segmental bone resection for primary bone sarcoma and metastatic disease - proximal femur, distal femur, proximal tibia, proximal humerus, Henderson failure modes, soft-tissue reconstruction

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By OrthoVellum Medical Education Team

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High-yield overview

Modular segmental replacement after resection for bone sarcoma or metastatic disease | advanced

Surgical Imaging

Distal femoral tumour endoprosthesis
Modular distal femoral tumour endoprosthesis with a hinged rotating knee — the commonest site, allowing immediate stability and early weight-bearing after segmental resection.Credit: AI-generated medical image · OrthoVellum
Proximal tibial endoprosthesis with gastrocnemius flap
Proximal tibial endoprosthesis: a medial gastrocnemius flap reconstructs the patellar tendon and extensor mechanism and provides soft-tissue cover — the key to function and infection control here.Credit: AI-generated medical image · OrthoVellum
Proximal femoral replacement
Proximal femoral replacement after resection, with the abductors reattached to the prosthesis — abductor reconstruction determines hip stability and gait.Credit: AI-generated medical image · OrthoVellum

Critical Decisions, Danger Structures and Exam Traps

Resection Margin Planning

The trap: Sizing the prosthesis from plain radiographs or a localised MRI. Intramedullary tumour and skip metastases extend beyond what radiographs show.

The fix: Plan resection on a whole-bone MRI with the staging biopsy tract included in the resection. A wide margin (Enneking) is the oncological priority — the reconstruction is secondary. Measure the planned osteotomy and order the implant length before theatre.

Biopsy Tract Contamination

Principle: The biopsy must be placed by (or in discussion with) the resecting surgeon, in line with the definitive incision, so the entire tract can be excised en bloc with the tumour.

Risk: A poorly placed or transverse biopsy contaminates compartments and neurovascular planes, converting a limb-salvage candidate into an amputation. Never delegate the biopsy to a non-tumour unit.

Proximal Tibia Extensor Mechanism

Location: Resection of the proximal tibia detaches the patellar tendon and tibial tubercle, destroying active knee extension.

The fix: Reconstruct the extensor mechanism (patellar tendon to prosthesis/tendon anchor) and rotate a medial gastrocnemius flap to reinforce it and provide soft-tissue coverage. Failure produces an extensor lag and a non-functional limb.

Proximal Femur Abductors and Dislocation

Principle: Resection sacrifices the abductor insertion on the greater trochanter and the hip capsule, leaving a high dislocation risk.

The fix: Reattach abductors to the prosthesis (trochanteric attachment device / mesh), use a dual-mobility or constrained/bipolar articulation, and consider capsular reconstruction. Restore offset and limb length to tension the soft tissues.

Periprosthetic Infection

Why it dominates: Large metal surface area, big dead space, immunosuppression from chemotherapy, irradiated tissue and long operative times all raise infection risk to roughly 10% overall.

Implications: Infection is the commonest reason for secondary amputation. Mitigate with silver-coated implants, muscle-flap coverage, meticulous haemostasis and dead-space management.

Endoprosthesis vs Amputation / Rotationplasty

Decision: Limb salvage is appropriate only when a wide margin can be achieved with preservation of a functional, sensate, vascularised limb.

Alternatives: Amputation or (in children with distal femoral tumours) rotationplasty give durable, low-maintenance function and may outperform a salvaged limb facing repeated reoperations. The honest discussion is an examiner favourite.

Mnemonic

Modes 1 to 5HENDERSON — The 5 Megaprosthesis Failure Modes

Mnemonic

S.A.L.V.A.G.ESALVAGE — Limb Salvage Planning Checklist

Indications

Primary Bone Sarcoma

  • Osteosarcoma and Ewing sarcoma — the classic indications in children and young adults; reconstruction follows wide resection after neoadjuvant chemotherapy
  • Chondrosarcoma — surgical resection is the mainstay (chemo/radio-resistant); endoprosthesis after segmental resection
  • High-grade spindle-cell sarcoma of bone, dedifferentiated chondrosarcoma

Aggressive Benign / Metastatic Disease

  • Metastatic bone disease with extensive bone loss or impending/pathological fracture not amenable to internal fixation (especially solitary renal/thyroid metastasis with good prognosis)
  • Aggressive giant cell tumour with joint destruction unsuitable for curettage
  • Failed prior reconstruction with massive bone loss (revision megaprosthesis)

Common Anatomical Sites

  • Distal femur — the commonest site for tumour megaprosthesis (rotating-hinge knee)
  • Proximal femur — bipolar or total-hip articulation; abductor reattachment critical
  • Proximal tibia — highest infection risk; extensor mechanism and gastrocnemius flap mandatory
  • Proximal humerus — commonest upper-limb site; shoulder stability/abduction limited
  • Total femur — massive disease or failed prior segmental reconstruction

Pre-operative Planning

Staging and Imaging

  • Whole-bone MRI — defines intramedullary tumour extent, soft-tissue mass, neurovascular involvement and skip lesions; the resection length is planned from this
  • CT chest (pulmonary metastases) and bone scan / PET-CT for systemic staging
  • Plain radiographs of the whole bone for templating and contralateral length comparison
  • Biopsy — image-guided core or open, tract in line with the definitive incision, planned for en-bloc excision

Templating and Implant Selection

  • Measure the resection length from the planned osteotomy (wide margin from tumour edge on MRI)
  • Restore limb length and joint offset templated against the contralateral limb
  • Order a modular system so segment length and articulation can be adjusted intra-operatively
  • Plan fixation (cemented vs uncemented stem; compress-type fixation; extracortical bridging)

Clinical Pearl

Exam framing: 'My priority is an oncologically adequate wide margin planned on the whole-bone MRI, with the biopsy tract excised en bloc. The reconstruction is secondary to the resection. I template the resection length and restore limb length and offset against the contralateral side, and I choose a modular system so I can fine-tune intra-operatively. I discuss limb salvage versus amputation or, in a child with a distal femoral tumour, rotationplasty, at the multidisciplinary tumour board.'

Endoprosthesis vs Biological Reconstruction Options


Clinical Decision Scenarios

Use these scenarios to practise clinical reasoning and management decisions

CLINICAL SCENARIOAdvanced

CLINICAL PROMPT

"A 16-year-old presents with a high-grade osteosarcoma of the distal femur. After neoadjuvant chemotherapy, how do you decide between an endoprosthetic reconstruction and the alternatives, and how do you plan the operation?"

PRACTICAL APPROACH
My first priority is oncological — I confirm staging with a whole-bone MRI, CT chest and PET/bone scan, and I confirm that a wide (Enneking) margin can be achieved while preserving a functional, sensate, vascularised limb. The reconstruction is always secondary to an adequate resection. **Decision-making**: The realistic options are a modular distal femoral endoprosthesis, a biological reconstruction (osteoarticular allograft, allograft-prosthetic composite, vascularised fibula for intercalary defects), or amputation/rotationplasty. In a 16-year-old I would discuss all of these at the multidisciplinary tumour board. An endoprosthesis gives immediate stability, early weight-bearing and reproducible function, allowing a prompt return to chemotherapy — but in a young patient it commits them to a lifetime of revisions for loosening, structural failure and infection. I would honestly discuss rotationplasty, which can give durable high-level function in an active young patient with fewer lifetime reoperations. **Planning**: I template the resection length from the MRI-defined intramedullary extent plus a margin, exclude skip lesions, and plan to excise the biopsy tract en bloc through an extensile approach. I restore limb length and offset against the contralateral side using a modular rotating-hinge knee. I plan fixation (cemented for early weight-bearing, or uncemented with extracortical bone bridging/HA collar to reduce aseptic loosening) and an infection-prevention strategy including a silver-coated implant where indicated. **Operative sequence**: en-bloc tumour and biopsy-tract excision protecting the popliteal neurovascular bundle, planned osteotomy with margin assessment, canal preparation and stem fixation, modular assembly to restore length, trial and reduction, soft-tissue reconstruction and layered closure over a drain. I co-ordinate rehabilitation with the chemotherapy schedule.
CLINICAL SCENARIOAdvanced

CLINICAL PROMPT

"Why does the proximal tibia have the worst outcomes of all endoprosthetic sites, and how do you specifically address this in your reconstruction?"

PRACTICAL APPROACH
The proximal tibia combines the two biggest problems in limb salvage: a thin, poorly vascularised soft-tissue envelope and loss of active knee extension. **Infection**: The anteromedial tibia is covered only by thin subcutaneous tissue and skin, often previously irradiated, over a large metal implant with substantial dead space — so the proximal tibia has the highest periprosthetic infection rate of any site. Infection is the dominant Henderson Type 4 failure mode and the leading cause of secondary amputation. **Extensor mechanism**: Resection detaches the patellar tendon and tibial tubercle, abolishing active extension and risking a disabling extensor lag (Henderson Type 1 soft-tissue failure). **How I address it**: I reconstruct the extensor mechanism by securing the patellar tendon to the prosthesis or a tendon anchor, then I rotate a medial gastrocnemius flap. This single flap does two jobs — it reinforces the extensor reconstruction and provides robust vascularised soft-tissue coverage over the implant, directly attacking both the extensor lag and the infection risk. I would also use a silver-coated implant, meticulous dead-space management and haemostasis, prophylactic antibiotics, and a rotating-hinge articulation. Post-operatively I protect the extensor repair in an extension brace and delay active flexion until the repair is secure, and I co-ordinate timing with chemotherapy to minimise wound complications during myelosuppression.
CLINICAL SCENARIOAdvanced

CLINICAL PROMPT

"Take me through the Henderson classification of endoprosthetic failure and explain why it is useful in clinical practice and the exam."

PRACTICAL APPROACH
The Henderson classification is the universal language for reporting failure of limb-salvage endoprosthetic reconstruction. It describes five modes. **Type 1 — Soft-tissue failure**: dislocation, tendon or extensor mechanism failure, and aseptic wound problems. This is the early, function-limiting mode — for example abductor failure at the proximal femur and extensor lag at the proximal tibia. **Type 2 — Aseptic loosening**: failure of fixation at the bone-implant interface, recognised by pain, radiolucent lines and implant migration. It is reduced by extracortical bone bridging, hydroxyapatite collars and compress-type fixation. **Type 3 — Structural failure**: fracture of the implant, a modular junction or the periprosthetic bone — a true mechanical breakage. **Type 4 — Infection**: the dominant catastrophic mode, around 10% overall, worst at the proximal tibia and after chemo/radiotherapy. It is the leading cause of secondary amputation and is mitigated by silver-coated implants and muscle-flap coverage. **Type 5 — Tumour progression**: local recurrence or extracompartmental progression, usually within the first few years, requiring re-resection or amputation. **Why it is useful**: Types 1-3 are mechanical and Types 4-5 are non-mechanical, which immediately frames management. It standardises reporting across centres and registries so outcomes are comparable, it guides the differential when a reconstruction fails, and in the viva it gives me a structured, complete answer to 'how can this fail?' — I can move logically from soft tissue, to fixation, to structure, to infection, to recurrence, attaching prevention and management to each.

Endoprosthetic Reconstruction (Tumour Megaprosthesis) — Exam Day Summary

Clinical summary

Evidence Base

Failure mode classification for tumor endoprostheses: retrospective review of five institutions and a literature review

Level III
Henderson ER, Groundland JS, Pala E, et al. • J Bone Joint Surg Am
Clinical Implication: Provides the standardised, anatomy-aware language for reporting megaprosthesis failure; because failure mode varies by site, outcomes should be reported per anatomic location rather than pooled.
Verify on PubMed (PMID 21368074)

Classification of failure of limb salvage after reconstructive surgery for bone tumours: a modified system including biological and expandable reconstructions

Level V
Henderson ER, O'Connor MI, Ruggieri P, et al. • Bone Joint J
Clinical Implication: The current reference framework for reporting and comparing limb-salvage failure across endoprosthetic, allograft, composite and expandable reconstructions.
Verify on PubMed (PMID 25371453)

Periprosthetic infection in patients treated for an orthopaedic oncological condition

Level IV
Jeys LM, Grimer RJ, Carter SR, Tillman RM • J Bone Joint Surg Am
Clinical Implication: Quantifies infection as the dominant catastrophic complication (Henderson Type 4) and the leading driver of secondary amputation, and supports two-stage revision over debridement alone.
Verify on PubMed (PMID 15805215)

Lower limb reconstruction in tumor patients using modular silver-coated megaprostheses with regard to perimegaprosthetic joint infection

Level IV
Schmolders J, Koob S, Schepers P, et al. • Arch Orthop Trauma Surg
Clinical Implication: Supports silver-coated implants as one element of an infection-prevention bundle in high-risk tumour reconstruction, alongside flap coverage and dead-space management.
Verify on PubMed (PMID 27783140)

Survival, complications and functional outcomes of cemented megaprostheses for high-grade osteosarcoma around the knee

Level IV
Zhang C, Hu J, Zhu K, Cai T, Ma X • Int Orthop
Clinical Implication: Validates patellar-tendon reattachment plus medial gastrocnemius flap at the proximal tibia and confirms the distal femur outperforms the proximal tibia for implant survival and function.
Verify on PubMed (PMID 29427125)

A system for the functional evaluation of reconstructive procedures after surgical treatment of tumors of the musculoskeletal system (MSTS score)

Guideline
Enneking WF, Dunham W, Gebhardt MC, et al. • Clin Orthop Relat Res
Clinical Implication: The standard, internationally comparable functional outcome score for reporting limb-salvage and ablative tumour reconstructions.
Verify on PubMed (PMID 8425352)

References

  1. Henderson ER, Groundland JS, Pala E, et al. (2011). Failure mode classification for tumor endoprostheses: retrospective review of five institutions and a literature review. J Bone Joint Surg Am. PMID 21368074. DOI 10.2106/JBJS.J.00834. — Original description of the five-mode Henderson failure classification (2174 patients, 534 failures) used universally for reporting megaprosthesis failure.

  2. Henderson ER, O'Connor MI, Ruggieri P, et al. (2014). Classification of failure of limb salvage after reconstructive surgery for bone tumours: a modified system including biological and expandable reconstructions. Bone Joint J. PMID 25371453. DOI 10.1302/0301-620X.96B11.34747. — ISOLS-modified Henderson classification incorporating biological and expandable reconstructions.

  3. Jeys LM, Grimer RJ, Carter SR, Tillman RM (2005). Periprosthetic infection in patients treated for an orthopaedic oncological condition. J Bone Joint Surg Am. PMID 15805215. DOI 10.2106/JBJS.C.01222. — Series of 1240 tumour prostheses: 11.0% infection, 37% of infected cases requiring amputation; tibial/pelvic site and radiotherapy as risk factors.

  4. Schmolders J, Koob S, Schepers P, et al. (2016). Lower limb reconstruction in tumor patients using modular silver-coated megaprostheses with regard to perimegaprosthetic joint infection: a case series, including 100 patients and review of the literature. Arch Orthop Trauma Surg. PMID 27783140. DOI 10.1007/s00402-016-2584-8. — Silver-coated lower-limb megaprostheses with 10% periprosthetic joint infection, lower than historical non-silver controls.

  5. Zhang C, Hu J, Zhu K, et al. (2018). Survival, complications and functional outcomes of cemented megaprostheses for high-grade osteosarcoma around the knee. Int Orthop. PMID 29427125. DOI 10.1007/s00264-018-3770-9. — Extensor mechanism reconstruction with medial gastrocnemius flap; distal femur five-year implant survival (86.1%) superior to proximal tibia (66.9%); mean MSTS 22.9 of 30.

  6. Enneking WF, Dunham W, Gebhardt MC, et al. (1993). A system for the functional evaluation of reconstructive procedures after surgical treatment of tumors of the musculoskeletal system. Clin Orthop Relat Res. PMID 8425352. — Description of the MSTS functional outcome scoring system.