Endoprosthetic salvage when biological reconstruction cannot provide a durable segment
- A megaprosthesis replaces absent bone; it does not replace a functional extensor mechanism, abductor, capsule or soft-tissue envelope.
- Rule out active infection and plan durable coverage before definitive implantation. Large metal surfaces and dead spaces amplify failure consequences.
- Select fixation at the remaining host bone, reconstruct muscle attachments and choose a bearing that balances stability with joint forces.
- The patient must understand revision burden, infection risk, possible amputation and the likely need for walking aids.
- Non-oncologic use is not automatically safer than oncologic use; repeated infection, prior surgery and poor biology often make it harder.
- “The indication is a non-reconstructable segmental defect in a patient with a viable, useful limb and controlled infection—not simply a large radiographic defect.
- “The most important preoperative question is whether the soft tissues can cover and stabilise the implant.
- “Reconstruct the abductor or extensor mechanism at the time of implantation; delayed tendon repair is less reliable.
- “A fluted, porous or cemented stem must bypass the remaining stress risers and obtain real fixation in the host bone.
Obtain cultures, debride and stage when infection is present. A megaprosthesis with a dead space and large surface can turn a treatable local infection into chronic limb-threatening infection.
Plan muscle or free-flap coverage with plastic surgery before opening. A thin scarred closure over metal is not durable coverage.
The abductor, extensor, capsule and collateral or soft-tissue stabilisers are part of the implant reconstruction. A stable stem does not make an unstable joint functional.
Compare pain, infection, rehabilitation time, prosthetic potential, energy cost and patient preference. Limb salvage is not always the lower-morbidity option.
Definition and Indications
A megaprosthesis is a large modular or custom endoprosthetic reconstruction that replaces a substantial segment of bone and the adjacent joint or fixation zone. In non-oncologic surgery it is used for massive bone loss after failed arthroplasty, infected nonunion, periprosthetic fracture, severe trauma, failed allograft or repeated revision.
Potential indications
- Segmental femoral or tibial loss with no reliable host bone for a conventional revision stem or plate.
- Recurrent periprosthetic fracture or nonunion where further biological fixation is unlikely to restore a useful limb.
- Failed allograft-prosthetic composite with resorption, fracture or nonunion when the soft tissue and infection are salvageable.
- Severe non-oncologic destruction after infection, after an eradication stage, with a viable limb and a patient who can rehabilitate.
- Selected periarticular destruction in a patient for whom amputation would provide a poorer functional outcome.
Reasons to avoid or delay
- active uncontrolled infection or a sinus;
- dysvascular or non-viable limb;
- inadequate soft-tissue coverage or inability to reconstruct the abductor/extensor mechanism;
- no useful distal limb or an ipsilateral hip/ankle that makes salvage non-functional;
- medical or social inability to tolerate staged surgery and rehabilitation;
- a biological reconstruction with a credible chance of durable fixation and lower risk.
The operation may be performed at the femur, tibia, pelvis or total femur. This topic focuses on non-oncologic segmental endoprosthetic principles; oncological margins and tumour reconstruction require a sarcoma pathway.
Patient and Limb Assessment
History
Record every operation, organism and antibiotic course, implant, fracture, flap, radiation, vascular procedure and current medication. Ask about pain, drainage, fever, falls, limb-length change, transfers, stairs, work, walking aids and the patient's willingness to accept further surgery. Explain the likely need for a brace, shoe modification or walking aid.
Examination
Soft tissue. Map scars, sinuses, flaps, skin mobility, muscle quality and dead space. Assess whether the planned incision can be closed with a vascularised layer over the prosthesis.
Mechanism. Test the abductor or extensor mechanism, joint stability, hip flexion, ankle/foot function and contralateral limb. Loss of a critical muscle group changes the operation and may favour a different salvage or amputation.
Neurovascular. Document sciatic, femoral, peroneal and tibial function, pulses, capillary refill and venous status. Obtain CT angiography or formal vascular testing for absent pulses, previous grafts, radiation or planned flap.
Function. Observe transfers and gait, assess sitting and the patient's ability to protect weight bearing. A preoperative trial of the anticipated brace or fixed limb can clarify whether salvage will be usable.
Infection
Use a composite PJI or osteomyelitis assessment. Aspirate when safe, obtain serum markers and plan multiple deep samples and histology. If infection is active, stage debridement, implant removal and dead-space management. A megaprosthesis should be the definitive reconstruction only when infection control is credible.
Anatomy and Soft-Tissue Reconstruction
The implant replaces bone, but function depends on the attached soft tissues.
- Hip: abductors and capsule centre the femoral head or proximal module. Deficiency increases dislocation and limp.
- Knee: the quadriceps, patella, patellar tendon and collateral or rotating-hinge stabilisers determine extensor function and joint stability.
- Thigh and leg compartments: muscle coverage protects metal, obliterates dead space and permits a durable closure.
- Major vessels and nerves: a large resection or previous infection may leave the femoral, popliteal, sciatic or peroneal structures scarred and close to the planned cuts.
- Remaining bone: the proximal or distal segment must provide fixation and bypass old screw holes, fractures and stress risers.
- Skin bridges and flaps: preserve blood supply and plan the incision with the plastic surgeon; a flap cannot be an afterthought.
Imaging and Implant Planning
Radiographs and CT
Obtain AP and lateral radiographs of the entire involved bone and adjacent joint, full-length alignment when possible, and views of the opposite limb for length and joint-level comparison. CT maps segmental loss, cortical defects, old hardware, canal patency and vessel or organ proximity. CT angiography is needed for vascular risk or a flap plan.
Design variables
Plan:
- amount and level of bone resection;
- distal and proximal fixation length and diameter;
- bypass of all stress risers;
- joint centre, offset, rotation and limb length;
- bearing type, hinge or dual-mobility stability;
- abductor, extensor, collateral and capsule attachment points;
- dead-space management and flap coverage;
- extraction, fracture, infection and amputation rescue plans.
A modular implant gives flexibility in the operating room but should not be used as an excuse to leave the patient-specific mechanics unresolved.
Construct Selection
- Best fit
- Defect with reliable host fixation and reconstructable biology
- Advantages
- Preserves bone and can provide durable biological restoration
- Main price
- Long healing, graft resorption, fracture or nonunion
- Best fit
- Global proximal loss with a reconstructable soft-tissue mechanism
- Advantages
- Restores bone and attachment points while replacing the joint
- Main price
- Nonunion, fracture, resorption, infection and graft availability
- Best fit
- Segmental defect with no credible biological fixation but viable limb and coverage
- Advantages
- Immediate length and stability, no waiting for structural graft union
- Main price
- Infection, dislocation, mechanism failure, fracture and repeated revision
- Best fit
- Unreconstructable infected or unstable joint with a useful distal limb
- Advantages
- Stable painless lever without a bearing surface
- Main price
- Permanent stiffness and shortening; may still have nonunion
- Best fit
- Non-viable, dysvascular, uncontrolled or functionally useless limb
- Advantages
- Definitive removal and potentially faster rehabilitation
- Main price
- Energy cost, phantom pain and prosthetic dependence
Operative Technique: PIPADRAW
Non-oncologic megaprosthetic reconstruction sequence
- Use the position that gives direct access to the segment and permits full-length imaging. Secure the pelvis and leave the foot visible for rotation and length checks.
- Prep from above the hip or knee to the foot; include the entire limb when a long modular implant or flap may be required.
- Coordinate blood conservation, cell salvage, neuromonitoring and the plastic-surgery coverage plan before incision.
- Confirm AP and lateral views of the complete reconstruction and adjacent joints. Have modular segments, trials, extraction tools, cables, plates and a backup implant available.
- Review CT and angiography, then verify side, length, joint centre and resection levels against the implant plan.
- Keep an amputation or staged spacer pathway available if infection or tissue viability is worse than expected.
- Administer antibiotics after multiple cultures when the patient is stable, or immediately for sepsis. Use a therapeutic regimen for established infection.
- Mark the sinus tract and plan en bloc excision. Prepare vascular control and flap harvest fields.
- Confirm the intended weight-bearing and mechanism-reconstruction protocol before starting.
- Use the safest scar or planned extensile incision with viable skin bridges. Raise full-thickness flaps and avoid devascularising the only closure.
- Identify the critical nerve and vessel structures before resection and protect them with controlled retractors.
- Preserve muscle attachments that can be repaired to the implant; excise only non-viable tissue or contaminated scar.
- Remove failed hardware, cement and non-viable bone. Take multiple deep cultures and histology.
- Resect to viable bleeding bone with a level that permits planned fixation and bypass of stress risers.
- Debride dead space and define whether infection is controlled enough for definitive implantation; if not, place a temporary antibiotic-loaded construct and stage.
- Ream or broach the host bone along its true canal. Obtain circumferential axial and rotational fixation and bypass old holes, fractures and osteolysis.
- Prepare the implant attachment sites for abductors, extensor mechanism, capsule and collateral or muscle slings.
- Use graft or sleeves only when they contribute to a stable, biologically plausible reconstruction.
- Assemble the trial modules and check limb length, offset, rotation, joint centre and soft-tissue tension.
- Test stability through the expected range, including the patient's high-risk positions. For a knee hinge, check extension, flexion and patellar tracking.
- Compare with the opposite limb and ensure the foot is plantigrade and the hip/ankle can compensate for the reconstructed segment.
- Avoid excessive traction or lengthening that can injure the sciatic or peroneal nerve.
- Confirm vessel patency and keep metal or cement away from exposed vessels and nerves.
- Plan the muscle and flap coverage before final fixation; do not leave a bare implant to be covered under emergency conditions.
- Cement or press-fit the stems according to host bone, implant design and infection status. Obtain stable fixation at the remaining bone and bypass stress risers.
- Reconstruct abductors, extensor mechanism, capsule and collateral or muscle slings with strong sutures, mesh or graft as appropriate.
- Place the modular joint or hinge, set the bearing and confirm that the mechanism remains tensioned through motion.
- Obtain AP and lateral images of the entire implant and adjacent joints.
- Check stem alignment, fixation, joint centre, length, offset, rotation, hinge or bearing position and any fracture.
- If stability, coverage or length is wrong, revise while the construct is accessible rather than relying on postoperative bracing alone.
- Achieve haemostasis, obliterate dead space and cover the implant with vascularised muscle or flap. Close skin without tension.
- Apply a brace or immobiliser that protects the mechanism without causing pressure injury. Start protected mobilisation with a rehabilitation and plastic-surgery plan.
- Continue infection treatment, thrombosis prevention, wound surveillance and serial imaging.
Complications and Salvage
- Clues
- Sinus, drainage, fever, abscess or painful loosening
- Response
- Cultures, imaging and multidisciplinary review
- Salvage principle
- Debridement and implant retention only in selected cases; stage removal or amputation when infection persists
- Clues
- Repeated reduction, poor abductor/capsular tension
- Response
- Reduction, nerve assessment and mechanism imaging
- Salvage principle
- Reconstruct soft tissues, correct joint centre/offset or revise the bearing/implant
- Clues
- Pain, migration, radiolucency or stem movement
- Response
- Exclude infection and protect loading
- Salvage principle
- Revise fixation with a longer or custom construct; reassess remaining bone
- Clues
- Acute pain, implant breakage or fracture at a stress riser
- Response
- Protect limb and image the whole reconstruction
- Salvage principle
- Fix the fracture and bypass it; revise modules if fatigue or alignment caused failure
- Clues
- Extensor lag, Trendelenburg gait or hinge instability
- Response
- Brace and assess repair, implant and soft tissue
- Salvage principle
- Reconstruct muscle/tendon or revise; counsel that function may remain limited
- Clues
- Necrosis, dehiscence or exposed metal
- Response
- Urgent plastic-surgical assessment and cultures
- Salvage principle
- Debride and obtain vascularised coverage; do not merely re-suture a contaminated wound
Rehabilitation and Outcomes
The rehabilitation plan is dictated by the weakest reconstruction: bone fixation, mechanism repair, flap or infection. Early goals are pain control, wound protection, safe transfers, hip/ankle or ankle-foot motion, and prevention of stiffness in uninvolved joints. Weight bearing is usually protected until the stem, fracture or mechanism is secure.
Counsel that the limb may remain weak, require a brace, have a limp and need walking aids. Functional outcome should be measured by pain, transfers, household and community ambulation, wound and infection status, not only by radiographs.
Guidelines, Registries & Global Practice
Global evidence. Non-oncologic megaprosthetic reconstruction is supported by small retrospective series, often including patients with failed arthroplasty, infected nonunion and failed allograft. Complication rates are high and heterogeneous. It should be offered in a multidisciplinary limb-reconstruction centre with plastic surgery, infection, vascular and rehabilitation support.
Practice principles:
- Establish whether infection and soft tissue are controllable before choosing definitive metal.
- Choose a reconstruction that provides real fixation in remaining host bone and bypasses stress risers.
- Rebuild abductors, extensors and capsule at the index operation.
- Plan dead-space control, flap coverage, thrombosis prevention and rehabilitation before incision.
- Compare salvage with amputation by patient function, pain, energy cost, rehabilitation burden and future revision risk.
Registries. National arthroplasty and fracture registries generally do not provide a dedicated non-oncologic megaprosthesis category. Local databases should record indication, infection, defect length, stem fixation, bearing, soft-tissue reconstruction, reoperation and amputation.
Global practice. Modular endoprostheses, custom implants and porous fixation are not universally available. In settings without them, staged fusion, structural grafting, standard revision or amputation may provide safer outcomes. A resource-limited plan still requires the same biological endpoint: a covered, viable and useful limb.
MCQ Practice Points
Q: When is a megaprosthesis indicated in non-oncologic salvage?
A: A massive segmental defect with no credible conventional biological reconstruction, in a patient with a viable limb, controllable infection, adequate coverage and enough function to make salvage worthwhile.
Q: What must be ruled out before offering megaprosthetic salvage?
A: Active infection, dysvascularity, non-viable soft tissue and an unusable distal limb. A megaprosthesis is not a way to bypass these problems.
Q: Besides bone, what must be reconstructed in a megaprosthetic limb?
A: The abductor or extensor mechanism, capsule, collateral or muscle stabilisers, dead space and soft-tissue coverage. Joint stability and gait depend on all of them.
Q: What is the major trade-off a patient accepts with megaprosthetic salvage?
A: Immediate length and stability versus high risk of infection, instability, mechanism failure, repeated revision and possible amputation. Discuss functional outcomes, not just limb preservation.
Q: A patient presents with a late painful megaprosthesis. What is your first response?
A: Exclude infection with a composite work-up, obtain full-length imaging and assess fixation, fracture, bearing and soft tissues. Do not label it aseptic loosening from a radiograph alone.
Long-Term Results of Proximal Femoral Replacement for Non-Neoplastic Disorders
- Retrospective review of 50 consecutive proximal femoral replacements in 49 patients with massive non-neoplastic bone loss (mean 3.1 prior hip operations); 32 patients (33 hips) assessed at a mean clinical follow-up of 11.1 years.
- Harris hip score improved from 46 preoperatively to 80 at one year and 76 at latest follow-up.
- Dislocation was the commonest complication (11 of 33 hips); four femoral and seven acetabular components were revised for aseptic loosening.
- Survivorship with revision as endpoint was 64% at 12 years.
The Value of Megaprostheses in Non-Oncological Fractures in Elderly Patients
- Retrospective series of 12 elderly patients with proximal or distal femoral fractures, severe bone loss or failed previous surgery, treated with hip or knee megaprosthesis.
- Functional scores (activities of daily living, SF-12, Oxford hip/knee) improved significantly from preoperative values.
- No radiological loosening or implant mobilisation at short-term follow-up.
- The implant restored immediate weight-bearing and independence where no bone remained for conventional reconstruction.
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 62-year-old has a fractured, resorbed proximal femoral allograft-prosthetic composite with a draining sinus. The abductors are absent and the distal femur is viable. The patient wants limb salvage. What is your staged plan?”
“A patient has repeated aseptic loosening and a periprosthetic fracture with only 4 cm of viable distal femur remaining. The extensor mechanism is intact and infection studies are negative. What are your options?”
“Two months after proximal femoral replacement for non-oncologic bone loss, a patient has two dislocations despite a brace. Imaging shows no stem migration. The abductor mechanism is absent. How do you manage this?”
Indication
- Massive segmental loss with no credible conventional biological reconstruction
- Viable limb, controllable infection, durable soft-tissue coverage and rehabilitation potential
- Compare allograft-prosthetic composite, revision/fusion and amputation
- Do not use simply because the defect is large
Plan
- Full-length radiographs and CT; CT angiography when vascular or flap risk
- Fixation segment, bypass, joint centre, length, offset, rotation and bearing
- Abductor/extensor/capsule reconstruction and dead-space plan
- Extraction, fracture, infection and amputation rescue pathways
PIPADRAW
- Position and image; prepare blood, cultures, implant modules and coverage
- Approach through viable tissue; debride, resect and define host fixation
- Protect nerves/vessels; trial length, centre, offset and stability
- Fix stems and mechanism, cover metal, image and protect weight bearing
Failure
- Infection: staged debridement or amputation, not casual retention
- Instability: mechanism and implant analysis; reconstruct causes
- Fracture/loosening: protect, image full construct, bypass and revise
- Wound failure: early flap and infection management
References
- Calabro T, Perazzo P, Ruggieri P, et al. Non-oncologic endoprosthetic reconstructions of the proximal femur: a systematic review. J Orthop Traumatol. 2017;18:303-312.
- Malkani AL, Fichman SG, Mayman DJ, et al. Revision total hip arthroplasty using a proximal femoral replacement: a review of the literature. J Arthroplasty. 2018;33:3243-3250.
- Berend KR, Lombardi AV Jr, Mallory TH, et al. The long-term outcome of 1,000 consecutive proximal femoral replacements for non-neoplastic disease. J Arthroplasty. 2004;19(7 Suppl 2):25-31.
- Haentjens P, De Boeck H, De Smet L, et al. Cemented distal femoral megaprosthesis for salvage after failed total knee arthroplasty. Clin Orthop Relat Res. 1996;332:122-130.
- Zuurmond RG, Aponso S, et al. Distal femoral replacement for non-neoplastic indications: a systematic review. Knee. 2020;27:1220-1230.
- Bus MP, Dijkstra PDS, van de Sande MAJ, et al. What are the long-term results of MUTARS modular endoprostheses for reconstruction after tumour resection? Clin Orthop Relat Res. 2017;475:708-718.
- Henderson ER, Groundland JS, Pala E, et al. Failure mode classification for tumor endoprostheses: retrospective review of five institutions and a literature review. J Bone Joint Surg Am. 2011;93(5):418-429. PMID: 21368074. DOI: 10.2106/JBJS.J.00834.
- Kinkel S, Krettek C. Distal femoral replacement for non-oncologic indications. Eur J Orthop Surg Traumatol. 2012;22:379-385.
- Mortazavi SM, Kurd MF, Bender B, et al. Distal femoral arthroplasty for the treatment of periprosthetic fractures after total knee arthroplasty. J Arthroplasty. 2010;25(5):775-780. PMID: 20171053. DOI: 10.1016/j.arth.2009.05.024.
- Springer BD, Sim FH, Hanssen AD, Lewallen DG. The modular femoral augment in revision total hip arthroplasty. J Arthroplasty. 2004;19:150-156.