High-yield overview
Complex arthroplasty procedure addressing failed primary TKR through systematic component revision and bone reconstruction | advanced
arthroplastySubspecialty
17Operative steps
5Danger zones
120-180minTypical duration
Critical Must-Knows
- AORI classification guides bone defect reconstruction: Type 1 (intact metaphysis) cement fill, Type 2A (contained) small augments, Type 2B/C (uncontained) metal augments or trabecular metal cones, Type 3 (massive loss) cones or hinged prosthesis.
- Constraint matching is critical: posterior-stabilised if MCL and LCL are intact, constrained condylar (CCK) if one collateral is deficient, rotating hinge if both are deficient or there is massive bone loss. Over-constraint increases interface stress and loosening; under-constraint causes recurrent instability.
- Extensor mechanism protection is paramount: never force patella eversion, use a quadriceps snip or tibial tubercle osteotomy if exposure is difficult, because patellar tendon avulsion is a catastrophic complication with poor salvage.
- Hybrid fixation is the international standard: cement the metaphyseal components and augments (cement augments to the component, never directly to bone), and use press-fit diaphyseal stems that bypass defects by a minimum of 100mm.
Clinical Pearls
- “A CT scan with metal-artefact reduction is invaluable for pre-operative planning: it defines three-dimensional bone loss, component position and rotation, and lets you template augments, cones and stems.
- “Joint line restoration within 5mm is critical for patellar tracking, flexion gap balance and functional outcome. Use the medial epicondyle-to-joint-line distance of about 30mm as the reference.
- “Trabecular metal cones for AORI Type 2C/3 defects are press-fit into the metaphyseal defect for structural support and biological fixation, with the component then cemented to the cone.
- “Two-stage revision is the most widely accepted standard for chronic infection: explant all components, place an antibiotic spacer, give organism-directed IV antibiotics, normalise inflammatory markers, then reimplant. Infection eradication is typically 80 to 90 percent.
When & Why
Across major arthroplasty registries (NJR, AJRR, AOANJRR, SHAR), the leading reasons for revision are infection, aseptic loosening and instability. Exact proportions vary by registry and era, but the rank order is broadly consistent worldwide. The indicative figures below reflect pooled registry experience. Aseptic loosening (around 25 to 30 percent of revisions)
- Progressive pain with weight-bearing activity
- Radiographic evidence of progressive radiolucency (greater than 2mm at the component-bone or component-cement interface)
- Component subsidence or migration
- Knee Society Score typically less than 60 points Instability (around 20 to 22 percent of revisions)
- Flexion instability: tight extension gap, loose flexion gap
- Extension instability: loose extension gap, tight flexion gap
- Mid-flexion instability: femoral component undersized or malrotated
- Global instability: inadequate constraint for ligamentous insufficiency Infection (around 15 to 25 percent of revisions)
- Acute (early post-operative under 4 weeks, or acute haematogenous with symptoms under 3 weeks): DAIR considered with mobile-bearing or liner exchange
- Chronic (over 4 weeks, established biofilm): two-stage revision is the most widely accepted standard; single-stage in selected cases
- Diagnosis follows MSIS/EBJIS/ICM criteria: elevated ESR/CRP, synovial leucocyte count over 1700 to 3000 cells per microL with over 65 to 80 percent PMN, positive culture, raised synovial alpha-defensin or leucocyte esterase
- Two-stage success (infection eradication) typically 80 to 90 percent; DAIR success more variable (around 50 to 70 percent, lower in chronic disease) Polyethylene wear and osteolysis (around 8 to 12 percent)
- Visible wear on radiographs
- Osteolytic lesions expanding
- Backside wear with mobile-bearing designs
- Address before catastrophic bone loss Periprosthetic fracture (around 5 to 8 percent)
- Supracondylar femur fracture (most common)
- Tibial plateau fracture
- Patellar fracture
- Su classification (femur, by location relative to the femoral component) and Felix classification (tibia) guide assessment; a loose implant or non-reconstructable fixation mandates revision rather than ORIF Other indications (around 8 to 10 percent)
- Component malposition causing pain, stiffness or instability
- Arthrofibrosis refractory to conservative management
- Unexplained pain after exclusion of infection and malalignment Pre-operative imaging
- Weight-bearing AP and lateral knee radiographs
- Merchant view for patellofemoral assessment
- Full-length hip-knee-ankle radiographs for alignment
- CT scan with metal-artefact reduction: invaluable for assessing three-dimensional bone loss, component rotation and planning reconstruction
- Consider SPECT-CT for a painful TKR without obvious cause
- MRI if there is extensor mechanism concern (tendon integrity) Laboratory investigation
- ESR and CRP are mandatory to exclude infection
- If elevated: knee aspiration (cell count, differential, culture)
- Consider alpha-defensin or PJI biomarkers if suspicion is high
- Optimisation targets: HbA1c less than 7.0 percent, albumin greater than 3.5g/dL, vitamin D greater than 30ng/mL Templating and implant planning
- Template component sizes (typically upsize 1 to 2 sizes from the primary)
- Plan augment requirements (5mm, 10mm, 15mm wedges or blocks)
- Determine stem lengths (typically 100 to 150mm press-fit)
- Consider the need for cones (Type 2C/3 defects)
- Assess constraint requirements based on ligamentous integrity
- Have back-up implants available (increased constraint, hinges)
Registry context for the indications
Large registries (AOANJRR, NJR, AJRR, Nordic registries) report cumulative revision of primary TKR around 4 to 6 percent at 10 years and roughly 8 to 10 percent at 15 to 20 years, with infection, aseptic loosening and instability as the dominant causes. Outcomes after revision are inferior to primary: re-revision risk is materially higher than primary revision risk, on the order of 10 to 18 percent by 5 to 10 years depending on indication (worst for infection and instability).
The Operation
The goal is to remove the failed components while preserving every millimetre of bone stock, reconstruct the bone defects with augments or cones matched to the AORI grade, restore the joint line and ligamentous balance, and select the least constraint that gives a stable knee. The exposure is the make-or-break phase of the case: a stiff, scarred revision knee that will not evert safely is exactly where patellar tendon avulsion happens, so the extensile-exposure decision (Steps 3 and 4 below) is the heart of the operation.
Operative sequence
Step 1Position, tourniquet and tranexamic acid
- Supine on a radiolucent table, with a lateral thigh support to prevent external rotation and a foot support that allows full knee flexion; consider a bump under the hip if there is a fixed flexion contracture.
- Tourniquet at 280 to 300mmHg at the thigh. Consider deferring inflation given the longer operative time (2 to 4 hours); an alternative is a lower pressure (250mmHg) with intermittent deflation.
- Have electrocautery ready for meticulous haemostasis.
- Tranexamic acid 1 to 2g IV reduces blood loss by 30 to 50 percent.
Step 2Skin incision
- Use the previous midline incision if possible (preserves blood supply).
- If there are multiple scars, choose the most lateral (preserves medial blood supply).
- Extend proximally or distally as needed for exposure.
- Excise old scars if they are wide, non-viable or adherent.
- Consider plastic surgery input if the skin is compromised (multiple previous incisions, previous radiation).
Step 3Medial parapatellar arthrotomy and gutter recreation
- Incise through the previous arthrotomy scar; expect dense scar tissue and adhesions.
- Sharp dissection to recreate the medial and lateral gutters.
- Identify and protect the patellar tendon insertion throughout.
- Extend proximally into the quadriceps tendon if needed.
Step 4Extensile exposure decision (the safety step)
- Attempt patella subluxation with the knee flexed and the tibia externally rotated.
- DO NOT force eversion: the risk is patellar tendon avulsion.
- If there is excessive tension on the patellar tendon, perform an extensile approach rather than persisting.
- Quadriceps snip (most common): a 45-degree oblique incision from the superolateral patella into the vastus lateralis, extending the standard arthrotomy proximally and laterally so the patella everts without tension. It is repaired side-to-side with strong interrupted sutures and allows full weight-bearing post-operatively.
- Tibial tubercle osteotomy (TTO): reserve for severe patella baja or multiple previous surgeries. Osteotomise a tubercle 5 to 6cm long with an oscillating saw, reflect it medially with the patellar tendon attached, and fixate with two screws at completion. Protected weight-bearing for 6 weeks with a brace is required.
Step 5Remove the polyethylene insert first
- Facilitates access and joint mobility.
- Inspect the wear pattern, which gives clues to malposition and instability: eccentric wear suggests component malrotation, and posterior wear suggests flexion instability.
Step 6Femoral component removal (usually first)
- Usually easier to remove first.
- Insert thin flexible osteotomes at the component-cement interface and work circumferentially around the component.
- Use a Gigli saw technique at the cement-bone interface if needed.
- Apply longitudinal extraction force with a removal device.
- The goal is to preserve bone stock and minimise bone loss.
Step 7Tibial component removal
- May be more difficult with stems and keels.
- Use osteotomes at the component-cement interface.
- Avoid leveraging against bone, which causes fracture.
- Work around the keel or stem carefully.
- Be prepared for intra-operative tibial plateau fracture (5 to 10 percent incidence), managed with a longer stem extension (150 to 200mm).
Step 8Complete cement removal (critical step)
- Use a combination of thin osteotomes, curettes, a high-speed burr and ultrasonic cement removal.
- The posterior femoral cement is the most difficult to access: use right-angle curettes, a headlight and retractors for visualisation.
- Complete removal is essential for new component seating.
- Remove incrementally to avoid excessive bone loss.
- Pulse lavage to clear all debris.
Step 9Assess the defects and the ligaments
- Inspect all surfaces: distal, posterior, medial and lateral femur; medial, lateral and central tibia.
- Palpate bone quality and bleeding, measure defect depth and location, and photograph for documentation.
- Classify the defects by AORI grade (full table in Background and Evidence) to drive the reconstruction.
- Assess ligamentous integrity: MCL with valgus stress in extension and 30 degrees flexion, LCL with varus stress in extension and 30 degrees flexion, grading laxity 1+, 2+, 3+. Document the findings to guide constraint selection.
Step 10Restore the joint line and reconstruct the tibia
- Anatomic joint line sits 30mm distal to the medial epicondyle; use the lesser trochanter as a reference. Target restoration within 5mm. Proximal migration causes patella baja, flexion instability and anterior knee pain; distal migration causes impingement and mid-flexion instability.
- Prepare the tibia first with minimal resection (3 to 5mm), cutting perpendicular to the mechanical axis to viable bleeding bone.
- Type 2A or 2B tibial defects: 5 to 15mm metal wedge or block augments, cemented to the component (NOT to bone). Trial the construct to verify fit.
- Type 2C or 3 tibial defects: a trabecular metal cone (see the CONES mnemonic below).
- Tibial stems: 100 to 150mm press-fit, bypassing the defect by 4 to 5 cortical diameters (minimum 100mm). Hybrid fixation (press-fit diaphyseal stem with cemented metaphysis) is widely favoured; fully cemented stems remain an accepted alternative with poor bone quality or short canals. Offset stems are available for difficult anatomy.
Step 11Femoral reconstruction and rotation
- Minimal resection to viable bone (5 to 7mm cuts), re-establishing the distal femoral cut perpendicular to the mechanical axis (5 to 7 degrees valgus).
- Femoral rotation is critical for patellar tracking and flexion gap balance, using multiple landmarks: the transepicondylar axis (most reliable), Whiteside's line (AP axis), and the posterior condyles with 3 degrees external rotation.
- Type 2A or 2B femoral defects: metal wedge augments (posterior augments for posterior condyle defects, distal augments for condylar defects), cemented to the component.
- Type 2C or 3 femoral defects: trabecular metal cones on the same principles as the tibia.
Step 12Trial the construct
- Insert trial tibial and femoral components with augments and stems.
- Assess flexion and extension gaps (should be balanced with 1 to 2mm laxity).
- Check varus and valgus stability in extension and 30 to 90 degrees flexion; verify no lift-off medially or laterally.
- Test range of motion (target 0 to 110 degrees minimum) and assess patellar tracking (should centralise without lateral tilt).
Step 13Select the constraint
- Posterior-stabilised (PS): intact MCL and LCL (Grade 0 to 1+ laxity); AORI Type 1, 2A, 2B defects. Cam-post gives AP stability with the lowest constraint, lowest interface stress and lowest loosening risk.
- Constrained condylar knee (CCK): MCL OR LCL deficient (Grade 2+ one side); AORI Type 2C with ligamentous insufficiency. Larger post and deeper femoral box give varus-valgus stability while still allowing rotation. The most common constraint level in revision.
- Rotating hinge: both MCL and LCL deficient (Grade 2 to 3+ both sides); AORI Type 3 with massive bone loss; severe instability; fixed flexion contracture over 30 degrees with ligamentous insufficiency. Gives varus-valgus and AP stability with 5 to 7 degrees rotation, but the highest interface stress requires long stems (150 to 200mm) and carries higher loosening risk.
- Fixed hinge (rarely used): complete constraint, no rotation; reserved for tumour reconstructions and salvage, with very high loosening rates. Not recommended for standard revision.
Step 14Cement the final components (hybrid fixation)
- Hybrid fixation is the international standard: metaphyseal components cemented, stems press-fit, augments cemented to the component, cones press-fit to bone with the component cemented to the cone.
- Tibial cementation: assemble the augment-component-stem construct on the back table and cement the augments to the tibial component (allow to set); pulse lavage and dry the tibial surface and metaphyseal bone; inject cement into the tibial surface and augment-bone interfaces; insert the assembled construct with the press-fit stem; maintain reduction with sustained pressure; remove all excess cement (especially posterior). Polymerisation time is 7 to 10 minutes (longer than primary due to the larger cement volume).
- Femoral cementation: same principles; cement the augments to the femoral component first, pulse lavage and dry the bone, inject cement and insert the construct, verifying rotation and position, then remove excess cement from the posterior condyles and intercondylar notch.
Step 15Patellar management
- Assess the existing patellar component and bone stock.
- If loose: revise to an all-poly button maintaining 15mm composite thickness.
- If absent and bone is adequate (greater than 15mm): consider selective resurfacing.
- If severe bone loss (less than 12mm): trabecular metal patellar component or leave unresurfaced.
- Unresurfaced patella: denervate the rim and remove osteophytes.
Step 16Insert the polyethylene, reduce and achieve haemostasis
- Polyethylene thickness is typically 12 to 15mm (thicker than primary 9 to 11mm) to compensate for bone loss and ligamentous laxity.
- Lock the insert onto the tibial tray and verify the locking mechanism.
- Reduce the knee with controlled force, verify stability throughout ROM, check patellar tracking (no lateral tilt or subluxation) and confirm 0 to 110 degrees minimum ROM.
- Deflate the tourniquet if used; meticulous haemostasis with electrocautery.
- Tranexamic acid 1 to 2g IV (reduces transfusion rate by 40 to 50 percent); consider topical tranexamic acid in the joint (additional 1 to 2g in 50ml saline, 5 minute dwell time).
- Expected blood loss 500 to 800ml (higher than primary 300 to 500ml).
Step 17Closure
- Arthrotomy closure is critical for extensor mechanism continuity: strong absorbable suture (0 or 1 Vicryl), interrupted or figure-of-eight.
- Quadriceps snip repair: side-to-side with strong interrupted sutures (0 or 1 Vicryl or Ethibond), ensuring no gaps in vastus lateralis; full weight-bearing is allowed.
- TTO repair: reduce the tubercle to anatomic position and fixate with two 4.5mm cortical screws; assess stability by flexing the knee. Protected weight-bearing for 6 weeks with a hinged brace.
- Subcutaneous and skin: 2-0 Vicryl to subcutaneous tissue (minimise dead space), 3-0 Monocryl subcuticular or staples to skin, sterile dressing. Consider negative pressure wound therapy if high risk.
- Drains are controversial; some surgeons use a deep drain (removed at 24 to 48 hours), others avoid them as tranexamic acid is sufficient, with no clear evidence of benefit.
Mnemonic
CONESCONES — trabecular metal cone technique for Type 2C/3 defects
C
Contained AND uncontained defects
Type 2C/3 massive metaphyseal loss
O
Osseointegration
Porous tantalum allows biological fixation
N
Non-cemented to bone
Press-fit the cone into the reamed defect; cement the component to the cone, never the cone to bone
E
Extensive support
Structural foundation bypassing metaphyseal deficiency
S
Size appropriately
Cone diameter (25 to 55mm) fills the defect without overstuffing
Extensor mechanism protection
Patellar tendon avulsion is the most catastrophic complication in revision TKR, with extremely poor outcomes. Never force patella eversion. Perform a quadriceps snip or TTO liberally if exposure is difficult. Maintain a 15mm patellar composite thickness. Protect the blood supply to the patella and tendons with careful handling.
Match the constraint — avoid over- and under-constraint
Over-constraining increases interface stress and accelerates loosening. Under-constraining causes recurrent instability. Carefully assess ligamentous integrity after bone reconstruction, and match the constraint to the bone loss and soft-tissue envelope. When in doubt, trial the next level of constraint and reassess stability.
Gigli saw technique for well-fixed posterior cement
Pass a 0.035-inch guidewire posterior to the femur using a curved awl, thread the Gigli saw over the wire, and oscillate the saw at the cement-bone interface to preserve bone stock. It is especially useful for well-fixed posterior cement that is hard to reach with osteotomes.
Always cement the augment to the component, not to bone
Trial the augment-and-component construct together, remove excess cement before polymerisation, and let modular augments fill the defect precisely without over-resection. Cementing an augment directly to bone defeats the modular philosophy and compromises the reconstruction.
Cement technique pearls
Pulse-lavage and dry the surfaces thoroughly, inject cement into the bone surfaces AND the interfaces, insert the component before the cement becomes doughy, maintain reduction with sustained pressure for the entire polymerisation time (7 to 10 minutes), and remove ALL excess cement before it hardens, especially in the posterior regions.
Aftercare & Complications
Immediate post-operative care (0 to 48 hours)
- Multimodal analgesia: regional block (adductor canal block preferred over femoral to preserve quadriceps) plus oral paracetamol, NSAIDs if not contraindicated, and oxycodone for breakthrough pain.
- VTE prophylaxis: LMWH (enoxaparin 40mg SC daily) or a DOAC (rivaroxaban 10mg daily or apixaban 2.5mg BD) for 35 days, critical in revision given the higher risk.
- Mechanical prophylaxis: TED stockings and pneumatic compression devices for 5 to 7 days.
- Cryotherapy for swelling and pain control.
- Drain removal at 24 to 48 hours if used (expect higher output than primary). Wound inspection at 48 hours. Weight-bearing and mobility (day 0 to 1 onwards)
- Standard revision: immediate weight-bearing as tolerated from day 0 to 1.
- Tibial tubercle osteotomy: protected weight-bearing with a hinged brace for 6 weeks, then progress.
- Periprosthetic fracture: depends on fixation stability, may need protected weight-bearing.
- Early mobilisation with physiotherapy twice daily; expect slower progress than primary TKR. No evidence for CPM benefit. Inpatient and outpatient rehabilitation
- Inpatient stay typically 5 to 7 days (longer than primary 3 to 5 days): intensive physiotherapy twice daily, gait re-education, stairs practice, with discharge once safely mobile and pain-controlled.
- Outpatient rehabilitation over 3 to 6 months (more intensive and prolonged than primary): emphasis on ROM restoration (realistic goal 0 to 110 degrees, not 0 to 120 degrees), quadriceps and hamstring strengthening, gait and balance, functional activities, and pool therapy once the wound has healed (3 to 4 weeks). Follow-up and return to activities
- Wound review at 2 weeks (remove staples or sutures); surgeon review at 6 weeks with clinical assessment and radiographs (AP, lateral, Merchant) to assess alignment, component position and TTO healing; then 3, 6 and 12 months; annual or biennial lifelong (higher re-revision rates than primary).
- Return to activities: sedentary work 8 to 12 weeks (longer than primary 6 weeks); active manual labour 4 to 6 months; driving (right knee) 6 to 8 weeks; low-impact activities (swimming, cycling, walking) 6 to 9 months. Avoid high-impact activities (running, jumping sports), which accelerate wear and loosening. Expected outcomes and patient counselling
- Pain relief in 70 to 80 percent (versus 85 to 90 percent primary); ROM typically 0 to 110 degrees (versus 0 to 120 degrees primary); Oxford Knee Score 28 to 32 (versus 38 to 42 primary); satisfaction 70 to 80 percent (versus 85 to 90 percent primary).
- Ongoing pain without loosening in 15 to 25 percent (versus 10 to 20 percent primary). Re-revision risk about 12 percent at 5 years and 18 percent at 10 years. Functional outcomes are inferior to primary TKR, so realistic expectations are essential.
Infection (3 to 5 percent superficial, 2 to 4 percent deep PJI after aseptic revision, 10 to 15 percent after septic revision) — the most common indication for re-revision; higher than primary due to longer operative time, increased tissue trauma and compromised soft tissues
- Recognition
- Clinical: wound drainage, erythema, fever, persistent pain. Laboratory: CRP over 10mg/L or ESR over 30mm/hr suspicious. Aspiration: over 3000 WBC per microL, over 80 percent PMN, positive culture. Alpha-defensin or synovial CRP if equivocal
- Prevention
- Pre-operative: exclude infection before an aseptic revision (aspiration, inflammatory markers), optimise diabetes (HbA1c less than 7 percent), smoking cessation, dental clearance, treat UTI. Intra-operative: prophylactic antibiotics (cefazolin 2g or vancomycin 15mg/kg, re-dose every 4 hours), antibiotic cement, minimise operative time, meticulous haemostasis. Post-operative: wound care, early mobilisation, drain removal under 48 hours
- Management
- Acute under 3 weeks: DAIR (debridement, component retention, polyethylene exchange, 6 weeks IV antibiotics) with 40 to 50 percent success. Chronic over 3 weeks: two-stage revision (explant all components, antibiotic spacer, 6 to 8 weeks IV antibiotics, reimplant when ESR/CRP normalised) with 70 to 80 percent success. Multiple failed revisions: arthrodesis or amputation. Suppressive antibiotics if unfit for surgery
Aseptic re-loosening (10 to 15 percent at 10 years) — progressive pain and radiolucency; the tibial component more often than the femoral; a second revision is more complex with worse bone stock
- Recognition
- Progressive pain with weight-bearing, rest pain in severe cases, decreased function. Radiographic: progressive radiolucency greater than 2mm at the interface, migration or subsidence, component fracture. Exclude infection (aspiration, ESR/CRP)
- Prevention
- Optimal cement technique (pulse lavage, pressurisation, 2 to 5mm mantle), viable bleeding bone, adequate defect reconstruction (augments, cones, allograft), stems bypassing defects by 100mm minimum, correct alignment (mechanical axis 0 degrees plus or minus 3 degrees), constraint matched to bone loss and ligamentous integrity
- Management
- Confirm aseptic (aspiration, inflammatory markers, PET if uncertain). Assess bone loss (usually AORI Type 2C/3 at re-revision). Re-revise with increased constraint and reconstruction (likely cones, structural grafts, longer 150 to 200mm stems, possibly hinges). Outcomes worse than first revision (about 70 percent versus 82 percent 10-year survival). Consider arthrodesis after multiple failures
Instability (5 to 10 percent after revision, versus 1 to 2 percent primary) — the second most common indication for re-revision; patterns include flexion, extension, global and mid-flexion instability
- Recognition
- Patient reports the knee giving way, difficulty descending stairs, instability on pivoting. Examination: varus/valgus laxity on stress testing, anteroposterior translation, recurvatum. Radiographic assessment of alignment, component position and joint line. EUA: systematic gap assessment in extension and 90 degrees flexion
- Prevention
- Restore joint line within 5mm (30mm medial epicondyle reference), balance flexion and extension gaps (1 to 2mm laxity), correct asymmetric bone loss with augments, establish correct femoral rotation (transepicondylar axis), match constraint to ligamentous integrity, adequate polyethylene thickness (12 to 15mm), trial stability before final implantation
- Management
- Exclude infection. Assess the pattern with EUA and radiographs. Flexion instability: thicker poly, increase posterior offset, increase constraint. Extension instability: thicker poly, increase distal offset, increase constraint. Global instability: inadequate constraint, re-revise up (PS to CCK to hinge). Mid-flexion instability: femoral malrotation, revise the femoral component. Outcomes variable, recurrent instability common (20 to 30 percent)
Periprosthetic fracture (5 to 10 percent intra-operative, 1 to 2 percent post-operative at 10 years) — supracondylar femur most common, then tibial plateau and patella; higher risk than primary due to osteoporosis, bone loss, stress risers and removal trauma
- Recognition
- Intra-operative: audible crack, visible fracture line, component instability. Post-operative: sudden pain, inability to bear weight, deformity. Classify: Lewis and Rorabeck Type I (non-displaced, stable implant), Type II (displaced, stable implant), Type III (loose implant)
- Prevention
- Gentle component removal (thin flexible osteotomes, no aggressive levering), complete cement removal before extraction, treat osteoporosis pre-operatively (bisphosphonates, teriparatide if severe), avoid anterior femoral notching, adequate stem lengths (bypass defects and stress risers by 100mm), consider prophylactic cerclage wires if high-risk
- Management
- Intra-operative small non-displaced: continue with a longer stem (150 to 200mm bypassing the fracture by 100mm minimum), plus cerclage wires if needed. Large or displaced: ORIF with a locking plate, then revise with longer stems, or stage (ORIF first, revision once healed at 3 to 6 months). Post-operative Type I: non-operative with a hinged brace. Type II: ORIF with locking plate and longer stems. Type III: re-revision with longer stems, or distal femoral replacement if severe comminution. Union 80 to 85 percent (lower than primary PPF)
Extensor mechanism complications (1 to 3 percent) — patellar tendon avulsion (most catastrophic), quadriceps rupture, patellar fracture, persistent extensor lag; devastating functional impact and very difficult to salvage
- Recognition
- Patellar tendon avulsion: intra-operative recognition, inability to extend the knee, palpable defect. Quadriceps rupture: palpable suprapatellar defect, patella baja, inability to straight-leg raise. Patellar fracture: pain, crepitus, radiographic fracture. Persistent lag: inability to fully extend actively despite passive extension
- Prevention
- NEVER force patella eversion. Adequate medial and lateral releases before subluxation. Perform a quadriceps snip or TTO liberally if exposure is difficult. Maintain a 15mm patellar composite. Protect the patellar blood supply. Assess patella height pre-operatively (patella baja is high-risk)
- Management
- Patellar tendon avulsion: immediate recognition and repair, usually augmented with an Achilles allograft or synthetic mesh (Marlex, GraftJacket) plus tibial tubercle fixation; protected or non-weight-bearing 8 to 12 weeks; outcomes guarded (50 to 70 percent residual extensor lag). Quadriceps rupture: acute repair with augmentation, V-Y turndown or allograft for chronic. Patellar fracture: brace if non-displaced, ORIF tension band or fragment removal if displaced. Chronic extensor lag: tolerate if mild (10 to 20 degrees); reconstruction has poor outcomes
Stiffness (8 to 12 percent, ROM under 90 degrees flexion) — higher than primary (3 to 5 percent) and harder to treat; often multifactorial (component malposition especially femoral internal rotation, patellofemoral overstuffing, improper joint line, arthrofibrosis)
- Recognition
- ROM under 90 degrees limiting function (cannot rise from a chair or climb stairs). Radiographic: assess component position (femoral rotation on CT), joint line height, patellofemoral overstuffing, anterior femoral notching. CT is essential to assess femoral component rotation, the most common cause of stiffness in revision
- Prevention
- Avoid component malposition, restore the joint line within 5mm, complete cement removal, remove all osteophytes and scar, soft-tissue balancing, aggressive physiotherapy from day 1 with adequate pain control and regional analgesia, and patient compliance
- Management
- Early under 12 weeks: intensive physiotherapy, MUA at 8 to 12 weeks if a plateau is reached (lower success than primary: 50 to 60 percent versus 60 to 80 percent, ROM improvement 10 to 20 degrees versus 20 to 40 degrees, higher complication risk including fracture and rupture). Late over 12 weeks: arthroscopic or open arthrolysis with scar release, revision of malpositioned components (femoral rotation most common; revise if over 10 degrees malrotation). Persistent stiffness after arthrolysis: may need to accept limited ROM if stable and pain-free
Venous thromboembolism (DVT 2 to 4 percent, PE 1 to 2 percent, fatal PE 0.2 to 0.3 percent) — higher than primary due to longer operative time, greater tissue trauma and older, more comorbid patients
- Recognition
- DVT: calf swelling, pain, warmth (Homan's sign unreliable); Wells score risk stratification; confirm with venous duplex ultrasound (sensitivity and specificity around 95 percent). PE: sudden dyspnoea, chest pain, tachycardia, hypoxia, tachypnoea; confirm with CTPA (gold standard) or V/Q scan if contrast is contraindicated. D-dimer is elevated but non-specific post-operatively
- Prevention
- Mechanical prophylaxis (TED stockings day 0 until mobile, pneumatic compression devices intra-operative and for 5 to 7 days), early mobilisation, chemical prophylaxis (LMWH enoxaparin 40mg daily or DOAC rivaroxaban 10mg daily or apixaban 2.5mg BD for 35 days, extended prophylaxis critical), adequate hydration, consider an IVC filter if previous VTE and anticoagulation is contraindicated
- Management
- DVT: confirm with ultrasound, therapeutic anticoagulation (LMWH bridge to warfarin INR 2 to 3 for 3 to 6 months, or DOAC rivaroxaban 15mg BD for 21 days then 20mg daily, or apixaban 10mg BD for 7 days then 5mg BD); calf DVT typically anticoagulate 6 to 12 weeks. PE: confirm with CTPA, therapeutic anticoagulation, consider thrombolysis or embolectomy if massive PE with haemodynamic compromise; IVC filter if anticoagulation is contraindicated. Higher morbidity and mortality in revision patients
Viva & Exam Focus
Mnemonic
REVISEREVISE — critical steps in revision TKR
R
Remove components, preserving bone stock
Thin flexible osteotomes at the interfaces
E
Eliminate ALL cement
Complete removal is essential for new component seating
V
Visualise the bone defects
AORI classification guides the reconstruction strategy
I
Integrity assessment
MCL and LCL status determine the constraint level needed
S
Stems bypass the defects
100mm minimum press-fit; hybrid fixation is the standard
E
Extensor mechanism protection
Never force eversion; use a quadriceps snip if needed
Popliteal artery
- Location
- 10 to 15mm posterior to the posterior tibial cortex, even closer with posterior bone loss
- How to protect it
- Maintain knee flexion when working posteriorly, use retractors, gentle cement removal, avoid aggressive posterior osteotome use
- Risk
- 0.1 to 0.3 percent injury rate (3 to 10x higher than primary), devastating if unrecognised
Common peroneal nerve
- Location
- Around the fibular neck, at risk with lateral exposure and valgus correction
- How to protect it
- Gradual deformity correction, avoid forced lengthening, identify the nerve if severe valgus, warn the patient pre-operatively
- Risk
- 2 to 5 percent palsy rate (4 to 10x higher than primary), especially with hinged prostheses
Patellar tendon
- Location
- Anterior insertion at the tibial tubercle, vulnerable during patella eversion
- How to protect it
- Never force eversion, adequate medial and lateral releases, perform a quadriceps snip or TTO if difficult, maintain a 15mm patellar composite
- Risk
- 1 to 3 percent avulsion rate, a catastrophic complication with 50 to 70 percent residual extensor lag
Collateral ligaments
- Location
- MCL femoral origin 3 to 4mm proximal and posterior to the medial epicondyle; LCL at the lateral epicondyle
- How to protect it
- Careful soft-tissue handling through scar, avoid overzealous release, assess integrity and match the constraint
- Risk
- Iatrogenic injury requires increased constraint and impacts stability and outcomes
Posterior capsule
- Location
- Posterior to the femoral condyles and tibial plateau
- How to protect it
- Gentle cement removal, controlled flexion during exposure, retractor placement under direct vision
- Risk
- Disruption causes instability, bleeding and potential vascular injury
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
Viva scenarioModerate
Clinical prompt
“A 68-year-old woman presents 8 years after a primary TKR with progressive medial knee pain, difficulty ascending stairs, and a sense of the knee giving way. Radiographs show a well-fixed tibial component but progressive radiolucency around the femoral component with some subsidence. ESR is 12, CRP is 8. How would you approach this case?”
Viva scenarioAdvanced
Clinical prompt
“You are 45 minutes into a revision TKR for aseptic loosening. You have just removed the components and all cement. As you assess the bone defects, you note massive medial tibial plateau loss with the defect extending to the cortical rim, and both femoral condyles have significant uncontained defects with some involvement of the posterior cortex. The MCL feels slightly lax on valgus stress testing. How do you classify these defects and what is your reconstruction strategy?”
Viva scenarioModerate
Clinical prompt
“During exposure for a revision TKR, you have performed a standard medial parapatellar arthrotomy. The knee is very stiff and scarred from previous surgery. As you attempt to evert the patella, you encounter significant resistance. Your assistant is applying lateral traction. What do you do at this moment, and what are your options to improve exposure safely?”
Exam day cheat sheet
Revision total knee replacement — exam-day essentials
Indications
- Aseptic loosening (around 25 to 30 percent across registries): progressive pain, radiolucency greater than 2mm, component migration
- Instability (around 22 percent): flexion, extension, global or mid-flexion patterns requiring re-revision
- Infection (around 15 to 25 percent): acute (early post-op or acute haematogenous) DAIR; chronic two-stage revision is the most accepted standard
- Polyethylene wear and osteolysis (around 12 percent): address before catastrophic bone loss
- Periprosthetic fracture (around 8 percent): Lewis and Rorabeck Type III with a loose implant
- Component malposition, arthrofibrosis, unexplained pain after an exclusion workup
Key anatomy
- Popliteal artery: 10 to 15mm posterior to the posterior tibial cortex, closer with bone loss
- Common peroneal nerve: around the fibular neck, 2 to 5 percent palsy risk (4 to 10x higher than primary)
- Patellar tendon: insertion at the tibial tubercle, 1 to 3 percent avulsion risk if eversion is forced
- MCL origin: 3 to 4mm proximal and posterior to the medial epicondyle; assess integrity for constraint
- LCL origin: lateral epicondyle; injury requires increased constraint to a CCK or hinge
Critical steps
- Pre-operative CT: assess three-dimensional bone loss (AORI), component rotation, plan reconstruction
- Exclude infection: aspiration is mandatory even with normal ESR/CRP before an aseptic revision
- Exposure: medial parapatellar, NEVER force eversion, quadriceps snip or TTO if difficult
- Component removal: thin flexible osteotomes at the interfaces, preserve bone stock, Gigli saw for cement
- Complete cement removal: pulse lavage, curettes, high-speed burr, ultrasonic — essential for seating
- AORI classification: Type 1 cement fill, 2A small augments, 2B/C metal augments or cones, 3 cones or hinges
- Restore joint line: within 5mm of anatomic (30mm medial epicondyle reference)
- Femoral rotation: transepicondylar axis, Whiteside's line, posterior condyles plus 3 degrees external
- Constraint matching: PS if MCL/LCL intact, CCK if one deficient, hinge if both deficient
- Hybrid fixation: cement metaphyseal components and augments, press-fit stems 100 to 150mm bypassing defects
Danger zones
- Popliteal artery posterior: maintain knee flexion working posteriorly, use retractors, gentle cement removal
- Common peroneal nerve laterally: gradual valgus correction, avoid forced lengthening, identify if severe
- Patellar tendon anteriorly: never force eversion, adequate releases, quadriceps snip or TTO if needed
- MCL and LCL: careful handling through scar, assess integrity, match constraint to deficiency
- Posterior capsule: gentle cement removal, controlled flexion, retractors under direct vision
Technique pearls
- CT is invaluable: three-dimensional bone loss, component rotation, surgical planning with the right implants
- AORI guides reconstruction: Type 1 cement, 2A small augments, 2B/C cones or large augments, 3 cones or hinges
- Trabecular metal cones: press-fit to bone for Type 2C/3, cement the component to the cone, never the cone to bone
- Joint line restoration is critical: 30mm medial epicondyle to the joint line, affects tracking and stability
- Constraint matching: PS for intact ligaments, CCK for one deficient, hinge for both — avoid over-constraining
- Cement augments to the component: never cement augments directly to bone, allows modular reconstruction
- Stems bypass defects by 100mm minimum: press-fit preferred, 150 to 200mm if a hinge is used for increased stress
- Thicker polyethylene in revision: 12 to 15mm versus 9 to 11mm primary, compensates for bone loss and laxity
Complications
- Infection 2 to 15 percent: DAIR acute under 3 weeks (40 to 50 percent success), two-stage chronic (70 to 80 percent success)
- Aseptic re-loosening 10 to 15 percent at 10 years: inadequate fixation, bone loss, malalignment
- Instability 5 to 10 percent: mismatch of constraint to ligaments, malrotation, joint line issues
- Periprosthetic fracture 5 to 10 percent intra-operative: gentle removal, longer stems, ORIF if needed
- Extensor mechanism 1 to 3 percent: patellar tendon avulsion catastrophic (50 to 70 percent residual extensor lag)
- Stiffness 8 to 12 percent: component malposition (femoral rotation), overstuffing, MUA 50 to 60 percent success
- VTE 2 to 4 percent DVT, 1 to 2 percent PE: extended prophylaxis 35 days, mechanical plus chemical essential
- Chronic pain 15 to 25 percent: exclude infection, assess alignment, position and balance; guarded re-revision outcomes
Post-op protocol
- Analgesia: adductor canal block, multimodal oral analgesia (paracetamol, NSAIDs, opioid breakthrough)
- VTE prophylaxis: LMWH or DOAC for 35 days extended, mechanical compression for 5 to 7 days
- Weight-bearing: immediate WBAT day 0 to 1 UNLESS a TTO was performed (then protected WBAT 6 weeks with a brace)
- Mobilisation: physiotherapy twice daily, slower progress than primary, discharge typically 5 to 7 days
- Rehabilitation: intensive outpatient 3 to 6 months, ROM goal 0 to 110 degrees (not 0 to 120), quadriceps strengthening
- Follow-up: 2 weeks wound, 6 weeks radiographs, then 3, 6 and 12 months, then annual lifelong (higher re-revision risk)
- Return to work: sedentary 8 to 12 weeks, active 4 to 6 months, low-impact activities 6 to 9 months only
Exam tips
- Know the AORI classification cold: Type 1/2A/2B/2C/3 with the specific reconstruction for each level
- Constraint matching algorithm: PS (ligaments intact), then CCK (one ligament deficient), then hinge (both deficient)
- Extensor mechanism protection is paramount: never force eversion, low threshold for a quadriceps snip or TTO
- Two-stage revision for infection: explant all, spacer, 6 to 8 weeks IV antibiotics, normalise markers, reimplant
- Joint line restoration: 30mm medial epicondyle reference, within 5mm critical for tracking and stability
- Trabecular metal cones: press-fit to bone for Type 2C/3 defects, cement the component to the cone
- Realistic expectations: 70 to 80 percent satisfaction (versus 85 to 90 percent primary), 0 to 110 degrees ROM, 12 percent re-revision at 5 years
- Registry data (AOANJRR, NJR, AJRR, Nordic): infection, aseptic loosening and instability are the leading revision causes worldwide
Background & Evidence
Epidemiology. Across the major arthroplasty registries (AOANJRR, NJR, AJRR, Nordic), cumulative revision of a primary TKR runs around 4 to 6 percent at 10 years and roughly 8 to 10 percent at 15 to 20 years. Infection, aseptic loosening and instability are the dominant drivers of revision worldwide, with proportions varying by registry and era but a broadly consistent rank order. Outcomes after revision are inferior to primary in every dimension: re-revision risk is on the order of 10 to 18 percent by 5 to 10 years (worst for infection and instability), pain relief and satisfaction run 70 to 80 percent (versus 85 to 90 percent primary), and realistic ROM is 0 to 110 degrees rather than 0 to 120. Pathoanatomy. Bone loss in the failed TKR accumulates from osteolysis behind loose components, from the mechanical trauma of component and cement removal, and from the original failure mode (wear, infection, fracture). The collateral ligament attachments on the femoral epicondyles are the key determinant of constraint: as bone loss erodes the condyles toward Type 3, the ligaments lose their anchorage and a more constrained prosthesis becomes necessary.
1
- Description
- Intact metaphyseal bone with minor surface damage; cancellous bone exposed but structural integrity maintained
- Reconstruction
- Cement fill alone; standard technique on both femur and tibia
2A
- Description
- Damaged metaphyseal bone, contained defect of one condyle or plateau with an intact cortical rim
- Reconstruction
- Cement fill or small augments (5mm); bone graft can incorporate
2B
- Description
- Uncontained defect of one femoral condyle or one tibial plateau; cortical rim deficient, cannot contain cement
- Reconstruction
- Metal wedge or block augments (5 to 15mm) cemented to the component
2C
- Description
- Uncontained defects of both condyles or both plateaus; more extensive metaphyseal loss but collateral attachments still intact
- Reconstruction
- Large metal augments or trabecular metal cones
3
- Description
- Massive metaphyseal defect affecting the collateral ligament attachments; severe bone loss compromising stability
- Reconstruction
- Trabecular metal cones, metaphyseal sleeves, hinged prosthesis, or tumour prosthesis for extreme cases
Posterior-stabilised (PS)
- Indication
- Intact MCL and LCL (Grade 0 to 1+); AORI Type 1, 2A, 2B
- Notes
- Cam-post gives AP stability; lowest constraint, lowest interface stress and loosening risk
Constrained condylar knee (CCK)
- Indication
- MCL OR LCL deficient (Grade 2+ one side); AORI Type 2C with ligamentous insufficiency
- Notes
- Larger post and deeper box give varus-valgus stability while allowing rotation; the most common constraint level in revision
Rotating hinge
- Indication
- Both MCL and LCL deficient (Grade 2 to 3+ both sides); AORI Type 3 with massive bone loss; severe instability; fixed flexion contracture over 30 degrees with ligamentous insufficiency
- Notes
- Varus-valgus and AP stability with 5 to 7 degrees rotation; highest interface stress, requires long stems (150 to 200mm), higher loosening risk
Fixed hinge (rarely used)
- Indication
- Tumour reconstructions and salvage situations only
- Notes
- Complete constraint, no rotation; very high loosening rates; not recommended for standard revision
Key evidence. The AORI system (Engh and Ammeen) remains the universal language for grading bone loss and directly drives the reconstruction algorithm tested in vivas. Porous tantalum cones press-fit into Type 2C and 3 metaphyseal defects provide mechanical support and durable biological fixation: the consecutive series of Spinello and colleagues showed 91.7 percent survivorship free of all-cause revision at a median 33 months with a cone plus a long uncemented diaphyseal-engaging stem, and the midterm series of Rajgopal and colleagues confirmed complete radiographic osseointegration with no loosening or migration at a mean 9-year follow-up. Hossain and colleagues reinforced that constraint must be matched to ligamentous integrity and bone loss rather than defaulting to the least constraint, and confirmed infection as the dominant driver of both revision and re-revision. The International Consensus Meeting on Periprosthetic Joint Infection (Parvizi, Gehrke, Chen) underpins the infection workup mandated before any aseptic revision and the two-stage management pathway for chronic PJI.
References
Evidence
Classification and preoperative radiographic evaluation: knee (AORI classification)
Engh GA, Ammeen DJ • Orthop Clin North Am (1998)
Key Findings:
- Defined the Anderson Orthopaedic Research Institute (AORI) bone-defect classification for femur (F) and tibia (T): Type 1 intact metaphyseal bone, Type 2 damaged metaphysis (2A one condyle/plateau, 2B both), Type 3 deficient metaphysis with collateral or extensor compromise.
- Linked defect type to reconstruction: Type 1 cement, Type 2 augments or graft with stems, Type 3 structural allograft or hinge constructs.
- Emphasised preoperative templating of stem size, augments and constraint, and preparing for the worst-case scenario intra-operatively.
Clinical implication: The AORI system remains the universal language for grading bone loss in revision TKR and directly drives the reconstruction algorithm (cement, augment, cone, hinge) tested in vivas.
Evidence
Management of bone loss: augments, cones, offset stems
Radnay CS, Scuderi GR • Clin Orthop Relat Res (2006)
Key Findings:
- Porous tantalum cones press-fit into Type 2 and Type 3 metaphyseal defects provide mechanical support and potential long-term biologic fixation.
- Technique: cement the core component into the cone, with stem extensions (75 to 200mm, press-fit or cemented depending on residual bone) and offset stems for canal mismatch.
- Cones may eliminate the need for extensive bone grafting or structural allograft in large cavitary defects.
Clinical implication: Establishes the modern construct philosophy: cone press-fit to host bone for metaphyseal fixation, component cemented to cone, stem engaging the diaphysis.
Evidence
The use of tantalum cones and diaphyseal-engaging stems in tibial component revision: a consecutive series
Spinello P, Ruberte Thiele RA, Zepeda K, Giori N, Indelli PF • Knee Surg Relat Res (2022)
Key Findings:
- 36 aseptic tibial revisions reconstructed with a single trabecular metal cone plus a long (100 or 155mm) uncemented diaphyseal-engaging stem.
- Knee Society Score improved from 29.7 to 86 points; all cones osteointegrated and any radiolucent lines were under 2mm and non-progressive.
- Survivorship free of all-cause component revision was 91.7 percent at a median 33-month follow-up; the single failure was for periprosthetic joint infection.
Clinical implication: Supports hybrid fixation (uncemented diaphyseal stem plus porous metaphyseal cone) as a reliable construct for managing tibial bone loss in revision TKR.
Evidence
Midterm outcomes of tantalum metal cones for severe bone loss in complex primary and revision TKA
Rajgopal A, Kumar S, Aggarwal K • Arthroplast Today (2021)
Key Findings:
- 62 complex primary and revision TKAs with severe distal femoral and proximal tibial bone loss managed with tantalum cones, mean follow-up 108.5 months.
- Range of motion and Knee Society Score improved substantially in both primary and revision cohorts with complete radiographic osteointegration of cones.
- No loosening or migration at final follow-up, confirming durable metaphyseal fixation in AORI Type 2 and 3 defects.
Clinical implication: Provides midterm (around 9 year) durability evidence for tantalum cones, justifying their use over cement-only reconstruction for severe metaphyseal defects.
Evidence
Midterm assessment of causes and results of revision total knee arthroplasty
Hossain F, Patel S, Haddad FS • Clin Orthop Relat Res (2010)
Key Findings:
- 349 revision TKAs across posterior-stabilised, condylar-constrained and rotating-hinge implants; infection was the most common reason for both failure and re-revision.
- Functional scores and range of motion improved irrespective of constraint type; overall 10-year survivorship was 90.6 percent.
- Rotating-hinge constructs achieved satisfaction and survivorship comparable to less-constrained designs when used for the correct indication (gross instability or massive bone loss).
Clinical implication: Reinforces matching constraint to ligamentous integrity and bone loss rather than defaulting to the least constraint, and confirms infection as the dominant driver of revision and re-revision.
Evidence
Proceedings of the International Consensus Meeting on Periprosthetic Joint Infection (ICM)
Parvizi J, Gehrke T, Chen AF • Bone Joint J (2013)
Key Findings:
- Provided consensus diagnostic criteria for PJI (combinations of elevated ESR/CRP, synovial leucocyte count and differential, positive culture, and histology) used internationally alongside MSIS and EBJIS definitions.
- Addressed prophylaxis, debridement thresholds, spacer use and timing of reimplantation in staged revision.
- Standardised terminology and management pathways across centres worldwide.
Clinical implication: Underpins the infection workup mandated before any aseptic revision and the two-stage management pathway for chronic PJI.
Evidence
Hip, Knee and Shoulder Arthroplasty: 2023 Annual Report
Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) • AOA Annual Report (2023)
Key Findings:
- Reports cumulative revision of primary TKR around 4 to 6 percent at 10 years, with infection, aseptic loosening and instability as the leading causes of revision.
- Revision outcomes are inferior to primary, with re-revision risk materially higher than primary revision risk.
Clinical implication: Provides the worldwide epidemiological frame for the indications for revision TKR and the benchmark for counselling patients on expected outcomes.