High-yield overview
APC Reconstruction for Massive Bone Loss
Allograft + implantBone stock + joint surface
Soft-tissueTendon/ligament reattachment to graft
Massive lossTumour / failed revision / periprosthetic
Graft complicationsNonunion, resorption, fracture, infection
Key features
What it is
PatternAn ALLOGRAFT-PROSTHETIC COMPOSITE combines a structural bulk ALLOGRAFT (restoring bone stock and, crucially, providing biological SOFT-TISSUE/TENDON reattachment) with a PROSTHESIS cemented/fixed into it (providing the articular surface) - used for MASSIVE SEGMENTAL bone loss.
Treatment
Indications
PatternMassive segmental bone/joint loss: after bone TUMOUR resection (limb salvage), failed REVISION arthroplasty with massive bone loss, and periprosthetic fracture/bone loss; common SITES are proximal femur, proximal tibia, proximal humerus and distal femur.
Treatment
Advantage & cost
PatternVersus a megaprosthesis, an APC restores BONE STOCK (host-allograft union) and allows SOFT-TISSUE attachment (abductors, extensor mechanism, rotator cuff/deltoid) - attractive in younger patients - but it is technically demanding, costly, and has ALLOGRAFT-specific complications (junctional NONUNION, RESORPTION, fracture, infection).
Treatment
Critical Must-Knows
- An allograft-prosthetic composite (APC) is a reconstruction that combines a structural bulk ALLOGRAFT with a PROSTHESIS: the allograft restores the missing segment of bone (bone stock) and provides a biological surface for SOFT-TISSUE and TENDON reattachment, while the prosthesis, cemented or fixed within the allograft, provides the articular (joint) surface - so the construct reconstructs both the bone and the joint.
- APCs are used for MASSIVE SEGMENTAL bone and joint loss that cannot be managed by standard implants: after bone TUMOUR resection (as part of limb salvage), in failed REVISION arthroplasty with massive bone loss, and in periprosthetic fracture with bone loss; common sites are the PROXIMAL FEMUR, PROXIMAL TIBIA, PROXIMAL HUMERUS and DISTAL FEMUR.
- The principal ADVANTAGE of an APC over a megaprosthesis (tumour endoprosthesis) alone is BIOLOGICAL: it restores host bone stock through host-allograft union and, critically, provides a biological attachment site for the SOFT TISSUES - for example the hip abductors at the proximal femur, the EXTENSOR MECHANISM (patellar tendon) at the proximal tibia, and the rotator cuff/deltoid/subscapularis at the proximal humerus - which can improve function and stability.
- These soft-tissue advantages are why an APC is often favoured at sites where tendon reattachment matters and in YOUNGER patients in whom preserving/restoring bone stock for the future is valuable, whereas a megaprosthesis offers faster reconstruction, immediate weight-bearing and no reliance on graft union (favoured in older/lower-demand patients or where rapid recovery is needed).
- The COMPLICATIONS are dominated by ALLOGRAFT-related problems: NONUNION at the host-allograft junction, allograft RESORPTION, allograft FRACTURE, and INFECTION (the allograft is avascular and at higher infection risk), plus the usual prosthetic complications (instability, loosening) and a small risk of disease transmission; reported series show good functional outcomes but a substantial complication burden, with union typically taking several months.
- OUTCOMES in selected patients are favourable - for example, in reverse shoulder arthroplasty for massive proximal humeral bone loss an APC gives substantial improvement in pain and motion with high (around 96% at 2-5 years) revision-free survival and reliable host-allograft union - but the technique is technically demanding and the high complication rate means careful patient selection, meticulous junction fixation/union, and infection vigilance are essential.
Clinical Pearls
- “APC = structural bulk ALLOGRAFT (restores bone stock + biological SOFT-TISSUE/tendon reattachment) + a PROSTHESIS (joint surface), for MASSIVE segmental bone loss (tumour, failed revision, periprosthetic).
- “Advantage over megaprosthesis: restores BONE STOCK + allows tendon attachment (abductors / extensor mechanism / cuff-deltoid) - favoured in younger patients / where soft-tissue attachment matters. Megaprosthesis = faster, immediate WB, no union needed (older/low-demand).
- “Complications are allograft-related: junctional NONUNION, RESORPTION, FRACTURE, INFECTION (avascular graft) - technically demanding, high complication burden, good outcomes in selected patients.
Biology Plus a Bearing
What & why
A bulk allograft (bone stock + soft-tissue/tendon attachment) plus a prosthesis (joint surface), for massive segmental bone loss (tumour, failed revision, periprosthetic).
The trade-off
Restores bone stock and tendon attachment (vs a megaprosthesis) - but is technically demanding with allograft complications (junctional nonunion, resorption, fracture, infection).
At a Glance Table
What is it?
- Answer
- Structural bulk allograft (bone stock + tendon attachment) with a prosthesis fixed inside it (joint surface)
Why choose it?
- Answer
- Restores bone stock and gives biological tendon-to-bone reattachment - a megaprosthesis gives neither
Who for?
- Answer
- Younger patients, and sites where tendon reattachment decides function (extensor mechanism, abductors, cuff)
Who not for?
- Answer
- Older or low-demand patients, poor union potential, absent tendon or motor nerve, active infection
Rate-limiting step
- Answer
- Union at the host-allograft junction - months of protected weight-bearing
Characteristic failure
- Answer
- Junctional nonunion; then resorption, fatigue fracture, infection
Overview and Epidemiology
- Where it sits. An APC is a salvage reconstruction for defects too large for standard revision implants. The competing options for the same defect are a megaprosthesis (endoprosthesis), a pure intercalary or osteoarticular allograft, arthrodesis, and - at the extreme - amputation.
- Who gets one. Two very different populations meet here: the young patient after tumour resection, in whom decades of future revision make bone stock precious, and the older patient with catastrophic periprosthetic bone loss after multiple failed revisions.
- Volume and expertise. These are low-volume, high-complexity operations concentrated in tumour and complex-revision units. Access to a tissue bank capable of supplying a size-matched structural allograft is a practical prerequisite, and availability varies markedly between health systems.
- The counselling reality. Complication rates are high by the standards of routine arthroplasty, and reoperation is common. That is accepted because the alternative is loss of the limb segment or its function - but it must be explicit in consent.
Concept, Indications & APC vs Megaprosthesis
Allograft for Bone and Tendon; Prosthesis for the Joint
An allograft-prosthetic composite (APC) combines a structural bulk allograft (which restores bone stock and provides a biological surface for soft-tissue/tendon reattachment) with a prosthesis fixed within it (providing the articular surface), to reconstruct massive segmental bone and joint loss - after tumour resection, failed revision arthroplasty, or periprosthetic bone loss - commonly at the proximal femur, proximal tibia, proximal humerus or distal femur. Its advantage over a megaprosthesis is biological: it restores bone stock (host-allograft union) and allows attachment of key soft tissues (hip abductors, the extensor mechanism at the proximal tibia, the cuff/deltoid at the proximal humerus), making it attractive in younger patients. The trade-off is that it is technically demanding, costly, and has allograft-related complications - junctional nonunion, resorption, fracture and infection (the graft is avascular).
Bone stock
- Allograft-prosthetic composite
- Restored (host-allograft union)
- Megaprosthesis
- Not restored (bone resected, replaced by metal)
Soft-tissue/tendon attachment
- Allograft-prosthetic composite
- Biological (tendon-to-allograft) - a key advantage
- Megaprosthesis
- Synthetic/limited (tendon-to-metal)
Speed / weight-bearing
- Allograft-prosthetic composite
- Slower (needs union)
- Megaprosthesis
- Faster; immediate weight-bearing
Best for
- Allograft-prosthetic composite
- Younger patients; sites needing tendon attachment; bone-stock restoration
- Megaprosthesis
- Older/lower-demand; rapid recovery; poor union potential
Main complications
- Allograft-prosthetic composite
- Junctional nonunion, resorption, allograft fracture, infection
- Megaprosthesis
- Aseptic loosening, infection, mechanical failure
Anatomy and Biomechanics of the Construct
- The load path. Load passes from the prosthesis, through the cement mantle inside the allograft, down the allograft segment, across the host-allograft junction, into host bone. Every one of those interfaces is a potential failure point, and the junction is the least forgiving because it is the only one that must heal biologically.
- Stress shielding within the graft. A long, stiff, cemented stem carries load past the allograft, so the graft is unloaded and remodels accordingly - contributing to the resorption seen over time. This is the same principle as femoral stress shielding, applied to dead bone with no capacity to respond.
- Why the stem should bypass the junction. A stem crossing the host-allograft junction acts as an internal splint, sharing load while union proceeds. The stem and the plate together protect the junction; neither alone is reliable.
- Soft-tissue mechanics. The reason to accept all of this is the tendon-to-bone attachment: tendon healing to allograft cortex recreates something close to a native enthesis, whereas tendon-to-metal relies on scar. That is why the extensor mechanism at the proximal tibia and the abductors at the proximal femur are the classic indications.
Key Point
Draw the load path: prosthesis → cement → allograft → junction → host. The junction is the only interface that must heal, so it is where the construct fails. The stem should bypass it as an internal splint, and the plate must not be relied on alone.
Classification Systems
- There is no APC-specific classification. What the examiner wants is that you classify the bone loss, because that is what selects the reconstruction.
- Paprosky (femoral and acetabular) is the standard language for revision arthroplasty bone loss; the severe grades - where metaphyseal bone is absent and the diaphysis is compromised - are where an APC or megaprosthesis enters the discussion.
- AAOS bone-deficiency classification distinguishes segmental from cavitary loss; an APC addresses massive segmental loss specifically.
- Enneking staging and the resection type frame the tumour case - whether the resection is intra-articular or extra-articular, and whether it is intercalary or osteoarticular, determines whether an APC is even applicable.
- By construct, distinguish the APC (allograft plus prosthesis) from a pure osteoarticular allograft (allograft including the joint surface, no implant) and an intercalary allograft (segment only, native joints preserved). Naming these correctly is a common viva discriminator.
Key Point
Asked to "classify", classify the defect: Paprosky for revision bone loss, AAOS segmental versus cavitary, Enneking and the resection type for tumour. Then name the construct precisely - APC versus osteoarticular allograft versus intercalary allograft - because they are different operations.
Clinical Assessment and Patient Selection
- Oncological status first. In the tumour patient, the reconstruction is subordinate to the resection: margins, staging and the systemic plan decide what is possible. A reconstruction that delays adjuvant therapy is the wrong reconstruction.
- Exclude infection. In failed revision arthroplasty, occult infection is the trap - implanting a large avascular allograft into an infected field is a predictable disaster. Inflammatory markers, aspiration and multiple intra-operative samples are mandatory before committing.
- Soft-tissue envelope and neurovascular status. Assess the abductors, extensor mechanism or cuff you are hoping to reattach. If the tendon is absent or the motor nerve is gone, the biological advantage of an APC disappears and a megaprosthesis becomes the more honest choice.
- Host factors that predict nonunion. Smoking, diabetes, malnutrition, corticosteroids, prior irradiation and chemotherapy all impair union at the junction - and chemotherapy is the norm in the very population most likely to receive an APC.
- Expectation and demand. The patient must accept protected weight-bearing for months and a genuine possibility of reoperation.
Chemotherapy, Radiation and the Junction
The tumour patient who most benefits from preserved bone stock is also the patient whose junction is least likely to unite: cytotoxic chemotherapy and prior irradiation both suppress the host biology on which union depends. Plan for it - maximise contact with a step-cut, add autograft, protect the construct longer, and counsel that union may take longer than the textbook several months.
Investigations and Preoperative Planning
- Plain radiographs, full-length and orthogonal, define the length of the defect and the quality of the remaining host bone.
- CT gives the cortical diameter and canal dimensions for size-matching the allograft and templating the stem, and assesses remaining host cortex at the intended osteotomy.
- MRI in the tumour case defines the soft-tissue extent and the resection level; in the revision case it is of limited value against metal.
- Infection work-up where any doubt exists: CRP/ESR, aspiration with culture and cell count, and a low threshold for further imaging.
- Tissue-bank liaison. The allograft must be ordered in advance and size-matched; confirm availability before scheduling. Have a fallback plan (megaprosthesis) if the graft is unusable at the time of surgery.
Management Algorithm
- Is there infection? If yes, eradicate first - staged, with a spacer. An allograft into an infected field will fail.
- Is the defect massive and segmental? If not, standard revision options (augments, cones, sleeves, impaction grafting) come first.
- Is the critical tendon present and innervated? Extensor mechanism, abductors, cuff. If yes, the biological attachment is the reason to consider an APC. If no, that advantage is theoretical - prefer a megaprosthesis.
- What is the patient's biology and life expectancy? Young, good union potential, decades ahead → APC to bank bone stock. Older, low demand, chemotherapy or irradiation, needs to walk now → megaprosthesis.
- Is a size-matched graft available? Confirm with the tissue bank before committing, and have the megaprosthesis on the shelf as a fallback.
- Can the patient comply with months of protected weight-bearing? If not, the construct will fail at the junction regardless of technique.
Surgical Technique
- Approach and exposure. Extensile, protecting the soft tissues you intend to reattach and the neurovascular structures; tag the tendons before resection so they can be found again.
- Resection. Perform the planned osteotomy at the templated level, preserving host periosteum and vascularity at what will become the junction.
- Prepare the allograft on a side table. Thaw and prepare the graft, ream and broach it, and cement the prosthesis into the allograft - done off the field this is quicker and gives better cement technique.
- Cut the junction. A step-cut or oblique osteotomy in both graft and host maximises contact area and gives rotational stability; size-match the cortical diameters.
- Assemble and fix. Reduce the composite to the host, ensuring the stem bypasses the junction, then apply a long plate under compression spanning it. Keep cement out of the junction.
- Graft the interface. Pack autograft around the junction; preserve any local vascularised tissue.
- Reattach the soft tissues. Repair tendon to the allograft - abductors, extensor mechanism, or cuff and subscapularis - and set the tension; at the shoulder this is where deltoid tensioning is restored.
- Assess stability and close over drains, with meticulous soft-tissue cover.
Cement in the Junction Guarantees a Nonunion
The single technical error that dooms the construct is allowing cement to extrude into the host-allograft junction. The prosthesis is cemented inside the graft; the junction is a biological interface that must heal. Cement there converts the rate-limiting step into an impossibility.
The Host-Allograft Junction: How You Get Union
Compress a Step-Cut, Graft It, Keep Cement Out
The whole construct hinges on union at the host-allograft junction. The principles:
- Keep the union biological: the prosthesis is cemented into the allograft, but the host-graft junction is left for bony union - cement must be kept out of the junction so it can heal.
- Maximise contact and stability: a step-cut (or oblique) osteotomy gives a larger contact surface and rotational stability than a transverse cut; add rigid fixation spanning the junction - a long plate (the prosthetic stem also bypasses it) under compression.
- Add biology: pack autograft / bone graft (and consider osteoinductive adjuncts) around the host-graft interface, and preserve the host periosteum and vascularity at the junction.
- Match and protect: size-match the allograft diameter to the host for cortical apposition, and protect weight-bearing until union, which typically takes several months - the junction is the commonest site of the characteristic nonunion.
(General nonunion management is covered in our Nonunion Management topic; the point here is the APC junction.)
Key Point
Union happens at the host-allograft junction: use a step-cut osteotomy, a long plate under compression (stem bypassing it), autograft at the interface, size-matched cortices, and keep cement out of the junction - then protect weight-bearing for several months. The junction is the commonest nonunion site.
Why the Allograft Behaves as It Does
Creeping Substitution, Processing and Immunology
- Creeping substitution: a bulk structural allograft is dead, non-living mineralised scaffold. It incorporates only by slow, incomplete revascularisation and remodelling from the host ends inward, so the central/mid-graft stays avascular dead bone for years. This is why union is slow, why the mid-graft can resorb and fatigue-fracture, and why the avascular graft is at higher infection risk (no blood supply to deliver immune cells or antibiotics).
- Processing trade-offs: fresh-frozen structural allograft (the usual choice) keeps mechanical strength and lowers - but does not abolish - immunogenicity; freeze-dried (lyophilised) reduces antigenicity and disease risk further but weakens the graft; irradiation/sterilisation lowers disease transmission but weakens the bone dose-dependently - so structural grafts are usually only lightly processed, trading a little disease risk for strength.
- Immunology and safety: donor screening and tissue-bank processing mitigate the small disease-transmission risk; routine HLA/blood-group matching is not needed for bone allograft, but some immunogenicity persists and may contribute to resorption.
(General bone-graft biology and incorporation are covered in our Bone Grafts topic; the point here is the structural-bulk-allograft behaviour that drives APC complications.)
Key Point
A bulk allograft is dead scaffold that incorporates by creeping substitution - slow and incomplete, from the ends in - so the mid-graft stays avascular: hence slow union, resorption, fatigue fracture and higher infection risk. Fresh-frozen keeps strength (some immunogenicity); irradiation/freeze-drying lower disease risk but weaken the graft; donor screening covers the small transmission risk.
Sites, Complications & Outcomes
Use the Soft-tissue Advantage; Respect the Graft Risks
- Site-specific soft-tissue advantage: proximal femur (abductor reattachment for stability/function), proximal tibia (extensor mechanism/patellar tendon reattachment - a major advantage over a megaprosthesis), proximal humerus (rotator cuff/deltoid/subscapularis repair - improves a reverse arthroplasty), distal femur.
- Achieve and protect union: secure host-allograft junction fixation (plate/compression) and biology; union typically takes several months, during which the construct is protected.
- Anticipate allograft complications: junctional nonunion, allograft resorption, allograft fracture, and infection (avascular graft, higher risk) - with a small disease-transmission risk; counsel and monitor.
- Select the patient: APC for younger patients / where tendon attachment matters; megaprosthesis where speed, immediate weight-bearing or poor union potential favour it.
- Outcomes: good function in selected patients (e.g. high revision-free survival and reliable union in proximal-humeral APC reverse arthroplasty), but a substantial complication burden demands expertise.
The Allograft Is the Strength and the Weakness
The defining feature of an allograft-prosthetic composite is that the allograft provides what a megaprosthesis cannot - restored bone stock and a biological surface for tendon and soft-tissue reattachment - but the same allograft is the source of the construct's characteristic complications, because it is avascular: it can fail to unite at the host-allograft junction, resorb, fracture, and is at higher risk of infection, with a small risk of disease transmission. So an APC should be chosen when its biological advantages genuinely matter - in younger patients, and at sites where tendon reattachment (the extensor mechanism, abductors, rotator cuff) is critical - and the surgeon must secure and protect the host-allograft junction to achieve union, respect the graft's fragility, and maintain infection vigilance. Where speed, immediate weight-bearing or poor union potential dominate, a megaprosthesis may be the better choice.
Complications and Their Management
- Junctional nonunion - the characteristic failure. Management is revision of the fixation with compression plus autograft, addressing any mechanical cause; the graft itself is usually retained if it is otherwise intact.
- Allograft resorption - progressive loss of graft substance, most marked where the graft is unloaded. Monitor radiographically; it may be asymptomatic, or may progress to fracture.
- Allograft fracture - a fatigue failure of dead bone, typically late and often at a stress riser such as a screw hole. Options are internal fixation, exchange of the graft, or conversion to a megaprosthesis.
- Infection - higher risk than routine arthroplasty because the graft is avascular and cannot be reached by host defences or systemic antibiotics. Treatment usually requires removal of the graft; salvage of an infected bulk allograft is rarely successful.
- Prosthetic complications - instability (especially proximal femoral and proximal humeral APCs where the soft-tissue tension is reconstructed), aseptic loosening and wear.
- Disease transmission - very small with modern donor screening and tissue-bank processing, but it must be mentioned in consent.
Key Point
Group the complications as graft (nonunion, resorption, fracture, infection) versus implant (instability, loosening, wear). The one that changes the whole plan is infection: an infected bulk allograft usually has to come out, because there is no blood supply to deliver antibiotics into dead bone.
Postoperative Care and Rehabilitation
- Weight-bearing is protected until there is radiographic evidence of union at the junction - a matter of months, not weeks - then advanced progressively.
- The tendon repair sets the early rehabilitation. Where the extensor mechanism, abductors or cuff have been reattached to the graft, the repair is protected in a brace or sling with a staged range-of-motion protocol; active loading of that tendon is deferred, because the repair is to relatively inert cortical bone.
- Radiographic surveillance continues for years, watching the junction for union and the graft for resorption or fracture; this is not a construct that is discharged at one year.
- Antibiotic prophylaxis and vigilance. A low threshold for investigating a painful or warm construct is appropriate given the infection consequences.
- Function returns slowly. Counsel that meaningful functional gain is measured over many months.
Outcomes and Prognosis
- Function. In selected patients an APC gives good functional scores and, at the shoulder, meaningful gains in pain and motion - the cited proximal-humeral series reported around 96% revision-free survival at 2-5 years with reliable union (see Evidence below).
- Union. Union at the junction is the rate-limiting step and is generally achieved, but takes months; the cited series reported a mean of around 7 months at the humerus.
- Survivorship falls with time. These are constructs with a cumulative complication burden - resorption and fatigue fracture are late events, so short-term series flatter them. Counsel in decades, not years, for a young patient.
- Registry evidence is limited. National arthroplasty registries (NJR, AJRR, AOANJRR, SHAR) capture conventional and revision arthroplasty well but record very small numbers of APCs, so the evidence base is institutional series rather than registry data. Be explicit about that limitation if asked for "the evidence".
Evidence & Key Studies
Evidence
APC reconstruction for massive proximal humeral bone loss in reverse shoulder arthroplasty
Sanchez-Sotelo J, Wagner ER, Sim FH, Houdek MT • Journal of Bone and Joint Surgery (Am) (2017)
Key Findings:
- An allograft-prosthetic composite restores proximal humeral bone, restores humeral length, allows deltoid tensioning and provides for repair of the rotator cuff and subscapularis - improving strength and stability in reverse arthroplasty.
- In 26 reverse arthroplasties (primary and revision) using an APC, pain, elevation and external rotation improved significantly, with no revision for host-allograft nonunion (mean union 7 months) and a 2-5 year revision-free survival of 96%.
- APCs are costly, technically demanding and can be compromised by allograft resorption, but are safe and effective for massive proximal humeral bone loss in selected patients.
Evidence
Resurfaced allograft-prosthetic composite for distal femur reconstruction in children with bone tumour
Errani C, Tanzi P, Ferra L, Campanacci L, Donati DM, Manfrini M • European Journal of Orthopaedic Surgery & Traumatology (2021)
Key Findings:
- A resurfaced allograft-prosthetic composite preserved bone stock and the proximal tibial physis after distal femoral sarcoma resection in children, minimising limb-length discrepancy at skeletal maturity.
- Patients who retained the original reconstruction had excellent function (MSTS ~29.5) and good knee motion, but complications (deep infection requiring removal, allograft fracture) occurred in 2 of 4.
- APC is a viable bone- and physis-preserving option in selected young patients despite a high risk of complications.
Evidence Attribution
The biological advantages of an APC (restoring bone, restoring length, allowing deltoid tensioning and rotator-cuff/subscapularis repair), the good functional outcomes with reliable host-allograft union (96% revision-free survival, mean union 7 months) and the concern of allograft resorption come from the cited Sanchez-Sotelo proximal-humeral series; the bone- and physis-preserving advantage in children after tumour resection and the high complication rate (infection, allograft fracture) from the cited Errani distal-femur series. The APC-versus-megaprosthesis trade-offs, the site-specific soft-tissue (extensor mechanism, abductor) advantages, and the allograft-related complication profile (junctional nonunion, resorption, fracture, infection) are standard, well-established teaching. (See also our Megaprosthesis / Endoprosthetic Replacement and Limb Salvage topics.)
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
Viva scenarioStandard
Clinical prompt
“What is an allograft-prosthetic composite and when is it used?”
Viva scenarioStandard
Clinical prompt
“What are the complications of an APC, and how does it compare with a megaprosthesis?”
MCQ Practice Points
- An APC = structural bulk allograft plus a prosthesis; an osteoarticular allograft has no implant; an intercalary allograft replaces a shaft segment with native joints preserved.
- The advantage over a megaprosthesis is biological: restored bone stock and tendon-to-bone reattachment.
- The commonest characteristic complication is nonunion at the host-allograft junction.
- The prosthesis is cemented into the allograft; the junction is left cement-free to unite.
- A bulk allograft incorporates by creeping substitution - slow and incomplete, from the ends inward - so the mid-graft remains avascular dead bone, explaining resorption, fatigue fracture and infection risk.
- Fresh-frozen preserves strength; irradiation and freeze-drying reduce disease and antigenicity risk but weaken the graft dose-dependently.
- HLA and blood-group matching are not required for bone allograft.
- Infected bulk allograft usually requires removal - antibiotics cannot reach dead bone.
- The classic site-specific advantages: extensor mechanism (proximal tibia), abductors (proximal femur), cuff and deltoid tensioning (proximal humerus).
Guidelines, Registries & Global Practice
- No dedicated guideline governs APC use. Practice is directed by tumour-service MDT consensus and institutional series rather than by a society guideline, which is itself an examinable point: be honest that this is expert-consensus territory.
- Registries under-capture it. NJR, AJRR, AOANJRR and SHAR describe conventional and revision arthroplasty in large numbers but record very few APCs, so registry survivorship curves do not answer this question.
- Tissue-bank access decides practice globally. Where a bone bank capable of supplying a size-matched structural allograft exists, an APC is a real option; where it does not, the practical choice narrows to a megaprosthesis - so availability, not surgeon preference, often determines the reconstruction offered.
- Regulation of tissue banking varies, which is why donor screening and processing standards - and therefore the residual disease-transmission risk - are not identical between countries.
Mnemonics & Memory Aids
Mnemonic
APC
A
Allograft (bone stock + soft-tissue/tendon attachment) - the biology
P
Prosthesis fixed within it (the joint/articular surface)
C
Composite for massive segmental loss (tumour/revision/periprosthetic) - Complications: nonunion, resorption, fracture, infection
Hook:APC: Allograft (bone + tendon attachment), Prosthesis (joint surface), Composite for massive loss (Complications: nonunion/resorption/fracture/infection).
Mnemonic
NRFI
N
Nonunion at the host-allograft junction - the characteristic failure
R
Resorption of the unloaded mid-graft
F
Fracture - fatigue failure of dead bone, often late, often at a screw hole
I
Infection - avascular graft, usually needs removal
Hook:NRFI - the four graft complications, in the order you will be asked for them.
Mnemonic
STEP the junction
S
Step-cut osteotomy - contact area and rotational stability
T
Tension the soft tissues; reattach tendon to graft
E
Exclude cement from the junction - it must heal biologically
P
Plate under compression, with the stem bypassing the junction
Hook:STEP: the four things that decide whether the junction unites.
Exam day cheat sheet
Allograft-Prosthetic Composite - Exam Day Cheat Sheet
What it is
- Structural bulk allograft + prosthesis
- Allograft: restores bone stock + biological soft-tissue/tendon attachment
- Prosthesis: provides the articular (joint) surface
Indications & sites
- Massive segmental bone/joint loss: tumour resection, failed revision, periprosthetic loss
- Sites: proximal femur, proximal tibia, proximal humerus, distal femur
- Younger patients / where tendon reattachment matters
APC vs megaprosthesis
- APC: restores bone stock + tendon attachment; slower (needs union)
- Megaprosthesis: faster, immediate weight-bearing, no union needed
- Choose by age/demand, soft-tissue needs, union potential
Complications
- Allograft: junctional nonunion, resorption, fracture, infection (avascular)
- Small disease-transmission risk; + prosthetic instability/loosening
- Good outcomes in selected patients but high complication burden