High Yield Overview

REVISION TOTAL KNEE ARTHROPLASTY FOR ASEPTIC LOOSENING

Previous incision (use most lateral if multiple). Plan for possible extensile exposures: quadriceps snip, V-Y quadricepsplasty, or tibial tubercle osteotomy if severe stiffness or bone ingrowth | consultant

Critical Danger Structures

Popliteal Artery

Location: 10-15mm posterior to posterior tibial cortex, at INCREASED risk in revision from scar tissue, retraction difficulties, bone loss exposing vessels. Injury rate 0.1-0.2% versus 0.05% primary.

Protection: ALWAYS use broad posterior retractors (Hohmann-type) during tibial component removal and posterior cement extraction. Work anteriorly to posteriorly. Consider releasing tourniquet before posterior dissection if prolonged case.

Popliteal Vein

Location: Accompanies popliteal artery in neurovascular bundle, injury more common than arterial (venous bleeding, DVT formation).

Protection: Maintain posterior retractor protection throughout tibial work. Control bleeding immediately - direct pressure, careful suture repair required for vein injury to prevent DVT. Vascular consult if major injury.

Common Peroneal Nerve

Location: Winds around fibular neck 2-3cm distal to fibular head. INCREASED risk in revision (2-3% versus 0.5-1% primary) from scar tissue tethering, valgus correction, lateral releases, prolonged retraction, tourniquet time.

Protection: Minimize lateral dissection and releases. Gentle retraction. Limit tourniquet time (release at 2 hours if prolonged). Careful with valgus correction - gradual gap balancing. Consider nerve identification if severe valgus deformity requiring extensive lateral release.

Tibial Nerve

Location: Posterior to popliteal vessels in neurovascular bundle, at risk if extensive posterior dissection for cement removal or polyethylene extraction.

Protection: Use posterior retractors protecting entire neurovascular bundle. Limit posterior dissection. Work under direct visualization when removing posterior cement or osteophytes.

Patellar Blood Supply

Location: Medial and lateral geniculate arteries form peri-patellar anastomosis. Previous medial arthrotomy compromises medial supply. Lateral release further compromises perfusion leading to patellar necrosis or fracture.

Protection: Use most lateral previous incision to preserve medial blood supply. Avoid lateral release if possible - optimize femoral component rotation instead. If lateral release necessary, limited to distal third only with meticulous hemostasis.

Mnemonic

I Can't Manage Severe DefectsAORI Classification for Bone Defects

Memory Hook:AORI classification is MANDATORY knowledge for revision viva. Grade femur and tibia separately. Type 2B and 3 require stems bypassing defect by minimum 2 cortical diameters. Type 3 often needs metaphyseal cones - porous tantalum with 95% survivorship at 5 years.

Mnemonic

PSYCHConstraint Selection Criteria

Memory Hook:CCK (varus-valgus constrained) is MOST COMMON constraint level in revision for aseptic loosening because component loosening causes ligament attenuation from abnormal kinematics. CCK provides 2-4° more constraint than PS through taller post and deeper cam. Excellent outcomes: 90% survivorship at 10 years with proper stem fixation.

Indications & Patient Selection

Absolute Indications

Aseptic tibial component loosening: Progressive pain worse with weightbearing and activity, radiolucent lines greater than 2mm complete or incomplete zones, subsidence on serial radiographs, progressive varus or valgus deformity indicating platform tilting.

Aseptic femoral component loosening: Progressive pain, radiolucent lines at bone-cement interface (particularly complete radiolucent lines all zones concerning), component migration or rotation on serial films, condylar lift-off.

Polyethylene wear with extensive osteolysis: Large osteolytic lesions visible on radiographs (particularly tibial metaphysis or femoral condyles), impending periprosthetic fracture from severe bone loss, mechanical symptoms from loose bodies.

Component malposition or malalignment: Severe malalignment from index surgery (varus greater than 5°, valgus greater than 10°) causing accelerated wear and secondary loosening, severe flexion instability from femoral component excessive external rotation, patellar maltracking from component malrotation.

Relative Indications

Instability with component loosening: Giving way episodes, recurrent effusions, secondary bone loss from abnormal loading and micromotion. May be difficult to distinguish primary instability from instability secondary to loosening.

Pain with radiographic loosening: Progressive pain with radiographic evidence of loosening (radiolucent lines, migration) even without gross instability. Pain is subjective but combined with objective radiographic progression warrants revision.

Positioning and Preparation

Patient Position: Supine with operative leg free to flex 120° and extend fully. Foot of table dropped OR leg holder/post. Well-padded lateral thigh post at hip level. Bump under ipsilateral hip for 15-20° external rotation. Tourniquet proximal thigh (may need to avoid or release early if prolonged case greater than 2 hours). Leg draped free circumferentially including foot. Consider cell saver for blood management. Ensure fluoroscopy available and draped.

Surgical Approach: Previous incision (use most lateral if multiple). Plan for possible extensile exposures: quadriceps snip, V-Y quadricepsplasty, or tibial tubercle osteotomy if severe stiffness or bone ingrowth.

Incision: Use previous skin incision, preferentially most lateral scar to preserve medial blood supply. Excise previous scar if adherent or necrotic. May need to extend proximally 5-7cm above patella or distally 3-5cm below tubercle for exposure. Plan 15-20cm incision minimum for revision exposure.

Operative Technique

Step 1: Preoperative Planning and Infection Exclusion

Preoperative Planning and Infection Exclusion: CRITICAL - Exclude infection before any revision. Pre-op workup MANDATORY: (1) ESR and CRP (elevated suggests infection), (2) Knee aspiration under sterile technique - send for cell count with differential (greater than 3000 WBC or greater than 80% PMN suggests infection), culture aerobic/anaerobic/fungal (hold 14 days), (3) Consider alpha-defensin or synovial CRP if aspiration equivocal. Review ALL previous operative notes and implant details (manufacturer, sizes, constraint level). Review serial radiographs: AP, lateral, skyline - assess bone loss (AORI classification), component position, cement mantle, osteolysis extent. Template revision components, stems, augments, metal cones. Have implant company representative available with full revision system. Consent for: Extensile exposure (quad snip, V-Y, TTO), bone grafting, stems, augments, cones, possible conversion to hinged if severe bone loss or instability, possible two-stage if unexpected infection, blood transfusion.

Exam Pearl

Technical Tip: EXAM KEY - 'Before ANY revision TKA, I MUST exclude infection - this is non-negotiable. I obtain ESR, CRP, and knee aspiration for cell count and culture. Elevated CRP greater than 10 or synovial WBC greater than 3000 or greater than 80% PMNs highly suggests infection requiring two-stage revision. I review all previous operative notes to understand index procedure and implants used - manufacturer, sizes, constraint. I review serial radiographs assessing bone loss using AORI classification - femur and tibia graded separately 1, 2A, 2B, or 3. I template extensively planning stems, augments, and augmentation strategy. I ensure full revision system available intraoperatively. Consent includes extensile exposures, bone grafting, stems, augments, possible hinged prosthesis, possible two-stage if infection found.'

Dangers at this step

Proceeding to single-stage revision with occult infection - leads to persistent infection, treatment failure, worse outcomes than proper two-stage
Inadequate preoperative planning - intraoperative discovery of unexpected bone loss without implants available, case abandoned or compromised reconstruction
Not reviewing previous operative notes - unexpected findings, wrong implants ordered, prolonged case
Failing to consent for extensile exposures or complications - intraoperative difficulties with limited consent

Step 2: Approach Through Previous Incision

Approach Through Previous Incision: Use previous incision, preferentially most LATERAL scar if multiple to preserve medial blood supply. Excise previous scar completely if adherent or with poor edges. Sharp dissection through subcutaneous tissue to capsule - scar tissue often densely adherent. Create full-thickness flaps to capsule minimum 5mm. CRITICAL: In revision, skin is at much higher risk - previous surgery compromises blood supply, tension from swelling, thin flaps. Preserve ALL tissue possible. Identify previous arthrotomy site (usually medial parapatellar). Carefully develop plane between scar tissue and underlying implant using sharp dissection with scalpel - this prevents extensor mechanism injury. Release scar tissue from medial and lateral gutters, suprapatellar pouch, medial and lateral femoral condyles. Assess ability to evert patella - if difficult, STOP and plan extensile exposure.

Exam Pearl

Technical Tip: EXAM KEY - 'Revision approach uses previous incision, preferentially most lateral to preserve medial blood supply. Skin is at MUCH higher risk in revision - previous surgery, swelling, potential tension. I excise old scar and create full-thickness flaps minimum 5mm. I carefully develop plane between scar tissue and implant using SHARP dissection to prevent tearing extensor mechanism. I release gutters, suprapatellar pouch, and both condyles systematically. I assess patellar eversion - if difficult, I do NOT force but plan extensile exposure to protect extensor mechanism. Options include quadriceps snip (proximal lateral extension), V-Y quadricepsplasty (turndown), or tibial tubercle osteotomy. TTO is my preference for severe stiffness or well-fixed cementless components.'

Dangers at this step

Thin skin flaps less than 3mm - very high necrosis risk in revision, wound complications up to 10-15%
Forcing patellar eversion - patellar tendon avulsion, mid-substance rupture, patella fracture - CATASTROPHIC in revision
Aggressive traction on attenuated extensor mechanism - rupture requiring allograft reconstruction
Inadequate soft tissue release before attempting exposure - limits visualization, increases complication risk

Step 3: Extensile Exposure if Needed

Extensile Exposure if Needed: If unable to safely evert patella or gain adequate exposure, choose extensile technique: (1) QUADRICEPS SNIP (for moderate stiffness): Lateral extension of proximal arthrotomy at 45° from supralateral patella extending 4-5cm into vastus lateralis. Pros: Simple, effective, preserves blood supply. Cons: Risk of propagation into vastus. (2) V-Y QUADRICEPSPLASTY (for severe stiffness): Full-thickness V-shaped incision in quadriceps tendon extending 6-8cm proximally, advanced distally and closed as Y. Pros: Maximal exposure, preserves blood supply. Cons: Technically demanding, risk of quadriceps weakness. (3) TIBIAL TUBERCLE OSTEOTOMY (my preference for bone ingrowth or severe stiffness): Mark osteotomy 5-6cm long, 1cm wide, extending from 5cm distal to joint line proximally. Use thin osteotomes to create lateral and distal cuts, leaving medial soft tissue hinge. Complete with gentle elevation. Reflect tubercle with patellar tendon insertion proximally for exposure. Pros: Excellent exposure, protects extensor mechanism, allows lengthening if needed. Cons: Risk of fracture extension, non-union (5%), need for screw fixation at closure, NWB 6 weeks.

Exam Pearl

Technical Tip: EXAM KEY - 'Extensile exposure is often needed in revision - stiff knee, well-fixed components, patella baja. Options include quadriceps snip, V-Y quadricepsplasty, or tibial tubercle osteotomy. My preference is TTO for severe stiffness or cementless bone ingrowth because it provides excellent exposure while PROTECTING extensor mechanism. I mark 5-6cm long osteotomy starting 5cm distal to joint line, 1cm wide, using thin osteotomes creating lateral and distal cuts with medial soft tissue hinge. This allows proximal reflection of tubercle with intact patellar tendon. At closure, I fix with 2 screws (18mm bicortical) and 6 weeks NWB. TTO complications include fracture extension 5%, non-union 5%, but protects against patellar tendon avulsion which is catastrophic and very difficult to reconstruct.'

Dangers at this step

Quadriceps snip propagation into vastus lateralis muscle - difficult repair, quadriceps dysfunction
V-Y quadricepsplasty failure - quadriceps weakness, extension lag, poor function postoperatively
Tibial tubercle osteotomy fracture extension - propagates into tibial shaft, requires ORIF, prolonged NWB
TTO non-union 5% - persistent pain, requires revision fixation or bone grafting

Step 4: Component Extraction - Systematic Approach

Component Extraction - Systematic Approach: POLYETHYLENE FIRST: Remove poly liner - may be locked or loose from wear. Use extractor or osteotome carefully. ASSESS FIXATION: Test femoral and tibial components with gentle pressure and osteotome. FEMORAL COMPONENT: Usually less difficult. Insert thin flexible osteotomes at bone-cement interface starting anteriorly at cement-bone junction. Work circumferentially around component - medial, lateral, distal, posterior. Apply gentle impaction. Use component-specific extraction device or slap hammer. Protect condyles from fracture. TIBIAL COMPONENT: Often more difficult, larger bone-cement interface. Insert thin osteotomes at bone-cement interface peripherally 360°. Work posteriorly carefully to avoid popliteal vessels - use retractors. Once mobile, use extraction device or carefully lever out. PATELLAR COMPONENT if loose: Use thin osteotomes at cement-bone interface, gentle extraction. If well-fixed and tracking well, may consider RETAINING. Intraoperative frozen sections: Take 5-6 tissue samples from interface membrane for histology - greater than 5 PMN per high-power field suggests infection requiring conversion to two-stage.

Exam Pearl

Technical Tip: EXAM KEY - 'Component extraction in aseptic loosening is often easier than well-fixed cementless but requires care to prevent fracture. I remove poly first. I test component fixation - loose components may elevate easily. For femoral component, I insert thin flexible osteotomes at bone-cement interface starting anteriorly and work circumferentially releasing cement-bone junction. For tibial component with larger interface, I work peripherally 360° with osteotomes then posteriorly VERY carefully using retractors to protect popliteal vessels. I use extraction devices or slap hammer rather than aggressive levering which can fracture condyles. CRITICAL: I take 5-6 tissue samples from interface for frozen section - if greater than 5 PMN/HPF suggests occult infection requiring conversion to two-stage revision rather than proceeding. Well-fixed patellar component tracking well may be RETAINED to preserve bone stock.'

Dangers at this step

Periprosthetic fracture during extraction - femoral supracondylar, tibial plateau, condyle fractures. Weakened by osteolysis. May require ORIF or long stems.
Popliteal vessel injury during posterior tibial component removal - ALWAYS use retractors posteriorly
Proceeding with single-stage despite histologic evidence of infection - treatment failure, persistent infection
Aggressive levering causing uncontrolled fracture propagation into diaphysis

Step 5: Cement Removal and Membrane Debridement

Cement Removal and Membrane Debridement: After component extraction, remove ALL cement and interface membrane completely. FEMORAL CEMENT: Use thin osteotomes, curettes, high-speed burr, or ultrasonic cement removal system. Work systematically - anterior, medial condyle, lateral condyle, posterior condyles, intercondylar box. Preserve bone - avoid aggressive gouging. Remove all cement down to bleeding cancellous bone. TIBIAL CEMENT: Often more extensive. Use osteotomes peripherally, curettes centrally, high-speed burr for residual. CRITICAL: Complete cement removal required for optimal new cement interdigitation. MEMBRANE: Excise interface fibrous membrane completely - source of inflammatory mediators and poor bone quality. Curettage of sclerotic bone until punctate bleeding. IRRIGATION: Copious pulsatile lavage 6-9L removing all debris. BONE ASSESSMENT: After cement and membrane removal, assess bone defects - AORI classification: Type 1 (intact metaphyseal bone), Type 2A (damaged metaphysis, intact peripheral cortex), Type 2B (damaged metaphysis, deficient peripheral cortex), Type 3 (severe metaphyseal and epiphyseal damage). Document defects for reconstruction planning.

Exam Pearl

Technical Tip: EXAM KEY - 'Complete cement and membrane removal is ESSENTIAL for optimal revision fixation. I use combination of thin osteotomes, curettes, high-speed burr, and ultrasonic cement removal working systematically around femur and tibia. I preserve bone avoiding aggressive gouging - revision bone stock is precious. I excise interface membrane completely because it's source of inflammatory cytokines causing osteolysis and contains poor quality fibrous tissue preventing bone healing. After removal, I curettage sclerotic bone until punctate bleeding showing viable bone. I irrigate copiously with 6-9L pulsatile lavage. I then carefully assess bone defects using AORI classification - this guides reconstruction strategy. Type 1 minimal defect (cement and screws), Type 2A metaphyseal damage with intact rim (cement and screws), Type 2B metaphyseal damage with rim deficiency (augments or small cones), Type 3 severe defect (large cones, allografts, or custom).'

Dangers at this step

Incomplete cement removal - poor new cement interdigitation, early re-loosening of revision components
Overly aggressive cement removal - iatrogenic bone loss, fracture, cortical perforation
Retained fibrous membrane - prevents bone healing, source of continued osteolysis
Thermal necrosis from high-speed burr - cool with irrigation, use intermittent burring

Step 6: Bone Defect Assessment and Reconstruction Planning

Bone Defect Assessment and Reconstruction Planning: With knee in full extension, systematically assess bone defects FEMUR and TIBIA separately using AORI classification: FEMORAL ASSESSMENT: (1) Distal femur - intact versus cavitary defect versus segmental loss, (2) Posterior condyles - symmetric versus asymmetric loss, (3) Anterior cortex - intact versus notched versus deficient. TIBIAL ASSESSMENT: (1) Medial plateau - intact versus cavitary versus segmental, (2) Lateral plateau - usually better preserved, (3) Central metaphysis - cavitary defects common, (4) Peripheral cortical rim - intact versus deficient. RECONSTRUCTION OPTIONS: TYPE 1 (intact): Cement alone, possible screws for fixation. TYPE 2A (metaphyseal damage, intact rim): Cement with screws, possible small augments for contained defects. TYPE 2B (metaphyseal damage, deficient rim): Metal augments (wedge, block, custom), stems for load sharing. TYPE 3 (severe deficiency): Metaphyseal cones (porous tantalum or titanium), structural allograft, custom components, possible hinged prosthesis. STEMS: Add stem if AORI 2B or 3, or if anterior femoral cortex deficient. Stem diameter and length: Press-fit stems typically 100-150mm femur, 75-125mm tibia, diameter largest that fits canal without hoop stress fracture.

Exam Pearl

Technical Tip: EXAM KEY - 'Bone defect assessment is CRITICAL for reconstruction planning. I assess femur and tibia separately in full extension using AORI classification. FEMUR: Distal, posterior condyles, anterior cortex. TIBIA: Medial plateau (usually worse in varus loosening), lateral plateau, central metaphysis, peripheral rim. For TYPE 1 minimal defects, I use cement with screws. TYPE 2A with metaphyseal damage but intact rim, I use cement, screws, small augments for contained defects. TYPE 2B with rim deficiency, I use metal augments (wedge, block, or step augments) and stems for load sharing bypassing defect by 2 cortical diameters. TYPE 3 severe deficiency, I use metaphyseal cones (porous tantalum highly successful 95% at 5 years) or structural allograft. I add stems routinely for AORI 2B or 3, or if anterior femoral cortex deficient. Stems are press-fit, diameter largest that fits without hoop stress, length 100-150mm femur, 75-125mm tibia to bypass defect.'

Dangers at this step

Underestimating bone loss - inadequate reconstruction, early failure, subsidence
Overestimating bone stock - attempting cement-only reconstruction of deficient bone, failure
Stem too large diameter - hoop stress, intraoperative or postoperative periprosthetic fracture
Stem too short - inadequate fixation, undersized bypassing defect by less than 2 cortical diameters, failure

Step 7: Ligament Assessment and Constraint Planning

Ligament Assessment and Constraint Planning: After bone defect assessment, systematically assess LIGAMENT INTEGRITY: MCL: Most important. Apply valgus stress at 0° and 90° - assess opening. GRADE: Intact (less than 5mm opening), stretched (5-10mm), incompetent (greater than 10mm). LCL: Apply varus stress, assess. PCL: Usually absent or incompetent in loosening. Assess overall STABILITY: (1) Extension gap - measure with spacers, varus/valgus stress, (2) Flexion gap - measure, assess medial-lateral balance. DETERMINE CONSTRAINT LEVEL NEEDED: POSTERIOR-STABILIZED (PS): Intact MCL and LCL, balanced flexion-extension gaps, most revisions. VARUS-VALGUS CONSTRAINED (VVC) or CONSTRAINED CONDYLAR KNEE (CCK): MCL or LCL incompetent up to 10-15mm, flexion-extension gap imbalance less than 10mm, moderate bone loss with augments, most common in revision for loosening. ROTATING HINGE: Severe MCL or LCL incompetence greater than 15mm, massive bone loss requiring cones and stems, global instability, failed CCK. My threshold: MCL stretch greater than 10mm equals CCK. MCL incompetent greater than 15mm equals hinged. Consent patient preoperatively for possible hinged if severe instability.

Exam Pearl

Technical Tip: EXAM KEY - 'Ligament assessment determines constraint level required for stability. I systematically stress test MCL with valgus stress and LCL with varus stress at 0° and 90° flexion. MCL is most critical - if intact with less than 5mm opening, I can use PS revision implant. If MCL stretched 5-10mm or mildly incompetent, I use varus-valgus constrained (CCK) implant which has taller post and deeper cam providing 2-4° more constraint - this is MOST COMMON in revision for loosening with ligament attenuation. If MCL severely incompetent greater than 15mm opening, or global instability, I use rotating hinge prosthesis. PCL is usually absent or incompetent in loosening - not factor in decision. I measure flexion and extension gaps with spacers - if imbalanced greater than 10mm and not correctable with bone resection or soft tissue releases, I use CCK or hinge. Modern CCK implants with stems have excellent outcomes 90% survivorship at 10 years.'

Dangers at this step

Underestimating ligament incompetence - using PS when CCK needed, postoperative instability, dislocation
Overconstraining - using hinge when CCK adequate, transfers stress to bone-implant interface, loosening
Not testing ligaments under appropriate tension - false assessment, wrong implant choice
Assuming ligaments intact because patient stable preoperatively - loosening often associated with ligament attenuation from abnormal kinematics

Step 8: Femoral Bone Cuts and Augmentation

Femoral Bone Cuts and Augmentation: DISTAL FEMORAL CUT: Use intramedullary or extramedullary guide depending on bone loss and deformity. If using IM guide, may need larger diameter stem guide due to previous reaming. Cut perpendicular to mechanical axis (5-7° valgus from shaft). Resect minimum bone to achieve stable bleeding surface - typically 2-4mm more than primary to remove sclerotic bone. FEMORAL AUGMENTATION for defects: POSTERIOR CONDYLE ASYMMETRY (common): Use wedge augments - 5mm, 10mm, 15mm available. Build up deficient side (usually medial in valgus loosening, lateral in varus). DISTAL FEMORAL DEFECT: Step augments or block augments. SIZING AND ROTATION: Size femoral component - often need to downsize 1-2 sizes from primary due to bone loss. ROTATION using three references: TEA (gold standard), Whiteside's line, posterior condyles plus 3° ER (less reliable with asymmetric bone loss). POSTERIOR AND CHAMFER CUTS: Complete with cutting guides. Add STEM: Ream femoral canal sequentially, largest reamer that fits without excessive resistance. Trial stem - should be press-fit, stable without wobble. Stem length 100-150mm, bypass defects by 2 cortical diameters minimum.

Exam Pearl

Technical Tip: EXAM KEY - 'Femoral preparation in revision starts with distal cut perpendicular to mechanical axis. I resect minimum bone achieving stable bleeding surface - typically 2-4mm more than primary removing sclerotic bone. For posterior condyle asymmetry - very common in loosening - I use wedge augments 5-10-15mm building up deficient side to create equal flexion gap. I size femoral component often downsizing 1-2 sizes from primary due to bone loss. Rotation uses three references prioritizing TEA which is most reliable even with bone loss. I add stem in all significant revisions - ream femoral canal sequentially, press-fit stem, length 100-150mm bypassing defects by minimum 2 cortical diameters. Stem provides load sharing protecting bone-implant interface, reduces stress on augments, and improves rotational stability. I trial all components before final cementation ensuring proper sizing, rotation, and gap balance.'

Dangers at this step

Excessive distal femoral resection - elevates joint line, causes patella baja, limits ROM
Using augments without stems - high stress on augment-bone interface, early failure, augment loosening
Stem too large - hoop stress fracture of femoral cortex intraoperatively or postoperatively
Femoral component internal rotation - patellar maltracking, medial flexion gap tightness, instability

Step 9: Tibial Bone Cuts and Augmentation

Tibial Bone Cuts and Augmentation: PROXIMAL TIBIAL CUT: Use extramedullary guide if bone loss not severe. If severe bone loss or deficient landmarks, use intramedullary guide or reference off femoral component in extension. Cut perpendicular to mechanical axis (0° varus/valgus), posterior slope 3-5° (less than primary - CCK/hinged don't need rollback). Resect minimum bone to stable surface - often 2-4mm more than primary. CRITICAL: Minimize resection to avoid joint line elevation greater than 8mm. TIBIAL AUGMENTATION: WEDGE AUGMENTS for peripheral defects - medial (varus loosening common), lateral, posterior. Available 5-10-15-20mm. BLOCK or STEP AUGMENTS for larger segmental defects. METAPHYSEAL CONES for Type 2B/3 defects - porous tantalum or titanium, press-fit into metaphysis, excellent bone ingrowth (95% at 5 years). Cone sizes 25-45mm diameter. TIBIAL SIZING: Size baseplate for maximum coverage without overhang - may need smaller than primary. STEM: Ream tibial canal - offset reamer if canal not centered under tibial cut. Press-fit stem 75-125mm length, largest diameter that fits, bypasses defect by 2 cortical diameters. Stem provides load sharing critical in revision.

Exam Pearl

Technical Tip: EXAM KEY - 'Tibial preparation is often more challenging than femoral due to greater bone loss. I cut proximal tibia perpendicular to mechanical axis with 3-5° posterior slope - less than primary because CCK and hinged implants don't rely on slope for rollback. I minimize resection achieving stable bleeding surface - critical to avoid joint line elevation. For peripheral defects very common in loosening, I use wedge augments medial or lateral building up deficient side. For larger Type 2B or Type 3 defects, I use metaphyseal cones - porous tantalum or trabecular titanium - which press-fit into metaphysis and achieve excellent bone ingrowth with 95% survivorship at 5 years in literature. I size tibial baseplate for maximum coverage without overhang, often smaller than primary. I add stem routinely in revision - ream with offset reamer if needed, press-fit stem 75-125mm bypassing defect 2 cortical diameters. Stem is critical for load sharing in revision.'

Dangers at this step

Excessive tibial resection - joint line elevation greater than 8mm, patella baja, extensor dysfunction, poor ROM
Inadequate resection - unstable sclerotic surface, cement doesn't interdigitate, early loosening
Augments or cones without stems - high interface stress, subsidence, early failure
Offset stem malposition - stem anterior or posterior cortex perforation, malalignment

Step 10: Gap Balancing with Constrained Implant

Gap Balancing with Constrained Implant: Insert trial components - femoral component with augments and stem, tibial component with augments and stem, trial poly (start with 10-12mm, thicker than primary). EXTENSION GAP: Full extension, insert spacers or trial poly. Assess height and stability. Should be stable to varus/valgus stress - constrained implant provides 2-4° more stability than PS. FLEXION GAP: 90° flexion, assess. Should equal extension gap height with CCK design. BALANCING: Unlike primary TKA, revision balancing focuses on AUGMENTS and STEMS more than soft tissue releases. EXTENSION TIGHT: (1) Resect more distal femur or proximal tibia (but avoid joint line elevation), (2) Downsize augments. EXTENSION LOOSE: (1) Larger augments, (2) Thicker poly. FLEXION TIGHT: (1) Downsize femoral component, (2) Reduce posterior augments. FLEXION LOOSE: (1) Upsize femoral component, (2) Increase posterior augments, (3) Thicker poly. ASYMMETRIC GAPS: Use asymmetric augments - build up deficient side medial or lateral. May need minimal soft tissue releases but avoid excessive - ligaments already attenuated.

Exam Pearl

Technical Tip: EXAM KEY - 'Gap balancing in revision differs from primary because I use augments and component sizing more than soft tissue releases - ligaments often attenuated and further releases risk requiring hinged implant. I trial components with augments and stems, starting with 10-12mm poly thicker than primary. I assess extension and flexion gaps - should be equal height with CCK design. For extension gap tightness, I can resect more bone if joint line not elevated, or downsize augments. For extension gap looseness, I use larger augments or thicker poly. For flexion gap issues, I adjust femoral component size and posterior augments. Asymmetric gaps medial-lateral are balanced with asymmetric wedge augments building up deficient side rather than releasing intact side. Goal is stable knee through ROM without excessive soft tissue releases that would require higher constraint level.'

Dangers at this step

Excessive soft tissue releases - MCL or LCL incompetence requiring conversion to hinged implant
Joint line elevation greater than 8mm from excessive resection - patella baja, poor ROM, dysfunction
Overstuffing joint - stiffness, pain, limited ROM worse than primary
Understuffing - instability despite constrained implant, early failure

Step 11: Comprehensive Trial Assessment

Comprehensive Trial Assessment: With all trial components, augments, stems, and poly in place, perform SYSTEMATIC ASSESSMENT: (1) ALIGNMENT: Alignment rod from femoral head to ankle should pass through knee center - neutral mechanical axis ± 3°. (2) STABILITY: Varus/valgus stress at 0° and 90° - CCK should be stable less than 3mm opening. If greater than 10mm opening, consider hinged. (3) ROM: Target minimum 0-90° in revision. 0° extension critical. Flexion greater than 90° acceptable, greater than 110° good. Don't overstuff trying to achieve 120° - causes stiffness and pain. (4) PATELLAR TRACKING: Assess throughout ROM. If patella maltracking, check femoral rotation, check patellofemoral overstuffing. May need lateral release if not previously done, but cautiously due to blood supply. (5) JOINT LINE: Measure from inferior pole patella to tibial cut - should be 10mm (8-12mm acceptable). Joint line elevation greater than 8mm concerning. (6) NO IMPINGEMENT: Deep flexion, check no impingement posteriorly on poly or stems. (7) STABILITY OF CONSTRUCT: Ensure stems stable, augments stable, no rocking of components. Any concerns - REVISE before cementing.

Exam Pearl

Technical Tip: EXAM KEY - 'Comprehensive trial assessment in revision is MANDATORY before final implantation. I systematically assess: (1) Alignment with rod from hip to ankle through knee - neutral ± 3°, (2) Stability with varus/valgus stress - CCK should be stable less than 3mm, if greater than 10mm may need hinged, (3) ROM targeting 0-90° minimum, don't overstuff trying for 120° which causes pain and stiffness, (4) Patellar tracking throughout ROM without maltracking, (5) Joint line within 8mm of anatomic measured from inferior pole patella, (6) No posterior impingement in flexion, (7) Construct stability - stems press-fit, augments stable, components seated flush. I accept lower ROM goals in revision - 0-90° functional, 0-110° very good. Overstuffing to achieve 120° causes pain and stiffness. Any concerns with trials, I revise before cementing because once cemented, no going back.'

Dangers at this step

Accepting instability at trial thinking it will improve - postoperative instability, dislocation, early failure
Overstuffing joint to achieve high flexion - pain, stiffness, limited functional ROM, dissatisfaction
Not checking patellar tracking - postoperative maltracking, anterior knee pain, revision
Proceeding with joint line elevation greater than 8mm - patella baja, extensor dysfunction, poor outcomes

Step 12: Final Cementation - Stems, Augments, Components

Final Cementation - Stems, Augments, Components: Remove all trial components. Prepare bone surfaces: Pulsatile lavage 6-9L (more than primary), dry meticulously with suction and sponges, pack with dilute adrenaline-soaked sponges for hemostasis. Mix cement - use MULTIPLE batches (typically 3-4 batches for revision with stems). CEMENTATION SEQUENCE: (1) STEMS FIRST: Hand-pressurize cement into femoral and tibial canals using cement gun or syringe, insert stems to final position while cement still doughy. Hold stable. (2) AUGMENTS: Apply thin cement layer to bone and augment surface, pressurize against bone, hold stable while femoral/tibial component cement cures. (3) TIBIAL COMPONENT: Cement to proximal tibia and component undersurface, pressurize cement into bone, insert component ensuring stem fully seated in cemented canal, proper rotation (aligned to tibial tubercle and 2nd ray). (4) FEMORAL COMPONENT while tibial curing: Cement all cut surfaces and component, pressurize, insert in proper rotation (TEA alignment), ensure stem seated in cemented canal. Hold under pressure. Remove ALL excess cement meticulously - especially at stem tips, augment edges, posteriorly. Use curette, sponge, suction. Cement cure 12-15 minutes (longer than primary, more cement mass). Insert trial poly protecting surfaces during cure.

Exam Pearl

Technical Tip: EXAM KEY - 'Cementation in revision is more complex than primary requiring meticulous technique. I prepare bone with copious lavage 6-9L and ensure completely dry - revision bleeding often more than primary. I use multiple cement batches typically 3-4 mixes. SEQUENCE: I cement stems first, hand-pressurizing cement into canals with gun and inserting stems while doughy. Then augments with thin cement layer pressurized to bone. Then tibial component ensuring stem fully seats in cemented canal. Then femoral component. CRITICAL: I remove ALL excess cement especially at stem tips where it causes stress risers, augment edges, and posteriorly. Cement mass is larger so cure time longer 12-15 minutes. I protect surfaces with trial poly during cure. Meticulous cement technique is ESSENTIAL for longevity - interfaces at stems, augments, and components all must achieve optimal fixation.'

Dangers at this step

Incomplete cement penetration - early loosening, failure of stems or augments or components
Cement extrusion at stem tips - stress riser, periprosthetic fracture risk, pain
Cement between augment and component - prevents seating, instability, early loosening
Retained cement debris - third-body wear, accelerated poly wear, osteolysis

Step 13: Final Polyethylene and Stability Check

Final Polyethylene and Stability Check: After cement fully cured, remove trial poly. Irrigate copiously 3-6L removing all cement debris. INSERT FINAL POLYETHYLENE: Thicker poly in revision than primary, typically 12-15mm minimum for stability. Locking mechanism should engage with definitive click - verify locked by trying to remove. FINAL COMPREHENSIVE ASSESSMENT: (1) ROM 0-90° minimum without restriction or impingement, (2) Stability - varus/valgus stress should be stable at 0° and 90° with CCK implant, (3) Patellar tracking centrally, (4) No impingement posterior in deep flexion, (5) Alignment rod confirms neutral axis, (6) Extension gap and flexion gap feel balanced. Document poly thickness used, component sizes, stem lengths, augments used. Take final intraoperative photos if available. CRITICAL: Before closure, take INTRAOPERATIVE RADIOGRAPHS (AP and lateral) if fluoroscopy available - confirm component position, alignment, stem position, no fractures, cement mantle adequate.

Exam Pearl

Technical Tip: EXAM KEY - 'After cement cure, I irrigate copiously and insert final poly - thicker than primary, typically 12-15mm minimum for stability in revision. I verify locking mechanism engaged. I perform comprehensive final assessment: ROM 0-90° minimum acceptable, stability with stress testing, patellar tracking, alignment, no impingement. I document all component details - sizes, stem lengths, augment sizes and positions - critical for future revision. I strongly advocate intraoperative radiographs with fluoroscopy if available - confirms component position, alignment, stem seating, no fractures, adequate cement mantle. This identifies problems while still in OR rather than discovering on postoperative films when cannot correct. Intraoperative XR should be standard in revision TKA.'

Dangers at this step

Poly not fully locked - dislodgement postoperatively, catastrophic failure, emergency surgery
Not verifying ROM and stability - postoperative stiffness or instability discovered late
Failing to take intraoperative radiographs - unrecognized malposition, fracture, or cement problems
Not documenting component details - future revision surgeon doesn't know what implants present

Step 14: Extensile Exposure Repair and Closure

Extensile Exposure Repair and Closure: If TIBIAL TUBERCLE OSTEOTOMY performed: Reduce tubercle to anatomic position. Fix with 2 x 4.5mm cortical screws (18mm bicortical purchase) - one proximal, one distal. Screws perpendicular to osteotomy, slight compression. Alternatively use cables or wire if osteoporotic bone. Verify stability of fixation - should be stable to gentle stress. If QUADRICEPS SNIP: Repair with interrupted #1 Vicryl figure-of-8 sutures, ensure strong repair. If V-Y TURNDOWN: Advance quadriceps distally, close in Y-configuration with interrupted #1 Vicryl, may have slight lengthening. Release tourniquet (if used - may have released earlier due to prolonged case). Achieve meticulous hemostasis - revision bleeds more than primary. Consider tranexamic acid 1-3g intra-articular. DRAIN: Consider closed suction drain in revision (higher bleeding risk) - remove at 24-48 hours or less than 30mL/8hrs. CAPSULAR CLOSURE: Repair arthrotomy with interrupted figure-of-8 #1 Vicryl - critical for extensor mechanism. Ensure watertight closure. Deep fascia with 2-0 Vicryl. Subcuticular skin with 3-0 Monocryl or staples. Sterile dressing, compression, TED stockings, ice.

Exam Pearl

Technical Tip: EXAM KEY - 'If TTO performed, I reduce to anatomic position and fix with 2 screws - 4.5mm cortical, 18mm bicortical, perpendicular to osteotomy with slight compression. Alternatively cables in osteoporotic bone. I verify fixation stability. Patient will be NWB 6 weeks protecting TTO healing. I release tourniquet and achieve meticulous hemostasis - revision cases bleed more than primary due to extensive dissection. I consider drain in most revisions removing at 24-48 hours. Capsular closure is critical - interrupted figure-of-8 #1 Vicryl ensuring strong extensor mechanism repair. Subcuticular skin closure preferred over staples for cosmesis and lower infection risk. Compression dressing and DVT prophylaxis mandatory.'

Dangers at this step

TTO fixation inadequate - nonunion (5%), proximal migration, extensor mechanism dysfunction
Inadequate hemostasis - large hematoma, increased infection risk, drainage requiring evacuation
Weak capsular repair - extension lag, poor quadriceps function, patella baja
Wound complications much higher in revision 5-10% - infection, dehiscence, necrosis

Step 15: Postoperative Protocol and Follow-up

Postoperative Protocol and Follow-up: IMMEDIATE: DVT prophylaxis LMWH or factor Xa inhibitor for 6 weeks minimum (higher risk in revision). Multimodal analgesia including nerve block, periarticular injection, IV/PO analgesics. Ice, elevation, TED stockings. Drain removal 24-48 hours. DAY 1: Early mobilization with physio - if TTO, NWB 6 weeks with walker. If no TTO, WBAT with walker. Active ROM, CPM may be beneficial in revision. WEEK 2: Wound check, suture/staple removal. Continue DVT prophylaxis, physio, ROM exercises. WEEK 6: Clinical exam, AP and lateral radiographs - assess alignment, component position, no loosening, TTO healing if performed. If TTO healed, advance to WBAT. If no TTO, wean from walker to cane. MONTH 3: ROM goals 0-90° minimum functional, 0-110° very good in revision. Don't push for 120° - causes pain. MONTH 6: Return to low-impact activities if ROM and strength adequate. FOLLOW-UP: More frequent than primary - 2 weeks, 6 weeks, 3 months, 6 months, 1 year, then annually for life. Annual radiographs monitoring for loosening, osteolysis, subsidence, component migration. Educate patient: Lower ROM expectations than primary, longer recovery 6-12 months for maximal improvement, higher revision rate (approximately 5% at 5 years versus 1% primary), activity modifications (avoid high-impact).

Exam Pearl

Technical Tip: EXAM KEY - 'Postoperative protocol for revision TKA differs from primary. DVT prophylaxis for 6 weeks minimum - higher thromboembolic risk. If TTO performed, patient is NWB 6 weeks protecting osteotomy - walker, touchdown only. Radiographs at 6 weeks confirm TTO healing before WBAT. If no TTO, WBAT immediately but with walker longer than primary due to larger surgery. ROM goals are LOWER than primary - 0-90° minimum functional, 0-110° very good. I do NOT push for 120° which causes overstuffing, pain, and stiffness. Recovery is longer - maximal improvement 6-12 months versus 3-6 months primary. Follow-up more frequent - annual radiographs monitoring for loosening, subsidence, radiolucent lines greater than 2mm, component migration. Patient counseling critical: Lower expectations for ROM and function than primary, longer recovery, higher revision rate 5% at 5 years, activity modifications avoiding high-impact.'

Dangers at this step

Weightbearing on unhealed TTO - nonunion, proximal migration, failure requiring revision
VTE higher risk in revision - longer surgery, more tissue trauma, maintain prophylaxis 6 weeks
Unrealistic patient expectations - dissatisfaction despite successful revision, counsel preoperatively
Infection risk higher 3-5% versus 1-2% primary - vigilant monitoring for pain, fever, drainage

Complications

Additional Complications:

Neurovascular injury (0.2-0.5%): Common peroneal nerve palsy (2-3%) - foot drop, AFO and observation. Popliteal artery injury (0.1-0.2%) - immediate vascular repair or bypass, high amputation risk if delayed. Popliteal vein injury (0.2%) - repair to prevent DVT and venous congestion.
Venous thromboembolism higher rate (4-6%): Longer surgery, more trauma, previous surgery. Extended prophylaxis 6 weeks minimum, early mobilization, mechanical compression.
Component malalignment or malposition (2-4%): Stem malposition (anterior or posterior cortex perforation), component rotation error causing maltracking or instability, varus/valgus malalignment. May require early revision if severe symptoms or accelerated wear.

Post-operative Care

IMMEDIATE (Day 0): DVT prophylaxis LMWH or factor Xa inhibitor 6 weeks minimum (higher VTE risk). Multimodal analgesia with nerve block, periarticular injection, IV then PO medications. Ice, elevation, compression, TED stockings. Closed suction drain 24-48 hours.

DAY 0-1: Early mobilization with physio - if TTO performed, NWB (toe-touch only) 6 weeks with walker. If no TTO, WBAT with walker. Active ROM, ankle pumps, quadriceps sets. CPM may be beneficial in revision (controversial - some evidence for improved early ROM).

WEEK 2: Wound check, remove sutures/staples. Continue DVT prophylaxis, physio, ROM targeting 0-90°. If TTO, continue NWB. Monitor for wound complications (higher risk 5-10%).

WEEK 6: Clinical and radiographic assessment - AP, lateral, skyline radiographs assess alignment, component position, stem position, no subsidence or radiolucent lines, TTO healing if performed (bridging callus on XR). If TTO healed, advance to WBAT with walker. If no TTO, wean from walker to cane.

MONTH 3: ROM goals 0-90° minimum functional in revision, 0-110° very good. Do NOT overstuff or push for 120° - causes pain and stiffness. Quadriceps strengthening, proprioception exercises.

MONTH 6-12: Gradual return to low-impact activities (walking, swimming, cycling, golf) if ROM and strength adequate. Avoid high-impact activities (running, jumping, pivoting sports) - higher loosening risk.

FOLLOW-UP: More intensive than primary - 2 weeks wound check, 6 weeks, 3 months, 6 months, 1 year, then annually for life. Annual radiographs monitor for loosening (progressive radiolucent lines greater than 2mm, subsidence, component migration), osteolysis, stem fracture.

Patient education: Recovery longer than primary (maximal improvement 6-12 months versus 3-6 months), lower ROM expectations (0-110° excellent in revision versus 0-120° primary), higher re-revision rate (approximately 5% at 5 years versus 1% primary), activity modifications lifelong (avoid high-impact).

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 68-year-old presents with progressive pain 8 years after primary TKA. Radiographs show complete radiolucent lines around tibial component with 3mm subsidence on serial films. How do you exclude infection before proceeding with revision?"

EXCEPTIONAL ANSWER

Infection exclusion is MANDATORY before any revision - proceeding with occult infection leads to treatment failure. My systematic approach: PREOPERATIVE WORKUP: (1) Serology - ESR and CRP. Elevated levels (CRP greater than 10 mg/L, ESR greater than 30 mm/hr) are concerning but non-specific - can be elevated in aseptic loosening. Normal levels do NOT exclude infection. (2) Knee aspiration under sterile technique - CRITICAL test. Send for cell count with differential (greater than 3000 WBC or greater than 80% PMN highly suggests infection), Gram stain (low sensitivity), culture aerobic/anaerobic/fungal (hold minimum 14 days). (3) If aspiration equivocal (WBC 1500-3000 or 65-80% PMN), I use advanced tests: Alpha-defensin (high specificity for infection 97%), synovial CRP greater than 10 mg/L suggests infection, or next-generation sequencing if culture-negative but high suspicion. INTRAOPERATIVE: Even with negative preoperative workup, I ALWAYS take 5-6 tissue samples from interface membrane for frozen section - greater than 5 PMN per high-power field on frozen section indicates infection requiring conversion to two-stage revision. If frozen section positive, I abort single-stage, perform thorough debridement, place antibiotic spacer, and plan two-stage approach.

VIVA SCENARIOStandard

EXAMINER

"Explain the AORI classification for bone defects and how it guides your reconstruction strategy in revision TKA."

EXCEPTIONAL ANSWER

AORI (Anderson Orthopaedic Research Institute) classification grades bone defects femur and tibia SEPARATELY - critical because reconstruction differs: TYPE 1 - Intact metaphyseal bone with minor defects only. Reconstruction: Cement and screws sufficient. Example: Small cavitary defect in tibial metaphysis, peripheral cortical rim intact. TYPE 2A - Damaged metaphyseal bone but peripheral cortical rim intact. Reconstruction: Cement, screws, small augments for contained defects. Example: Moderate osteolysis with cavitary defects but rim provides support. TYPE 2B - Damaged metaphyseal bone with deficient peripheral cortical rim. Reconstruction: REQUIRES metal augments (wedge, block, or step augments) PLUS stems for load sharing. Stems bypass defect by minimum 2 cortical diameters (typically 100-150mm femur, 75-125mm tibia). Example: Severe varus loosening with medial tibial plateau collapse, rim deficiency. TYPE 3 - Severe metaphyseal and epiphyseal deficiency. Reconstruction: Metaphyseal cones (porous tantalum or trabecular titanium press-fit into metaphysis - excellent bone ingrowth, 95% survivorship at 5 years), structural allograft, custom components, possible hinged prosthesis if massive bone loss. Example: Multiple previous revisions with severe bone loss. The classification GUIDES RECONSTRUCTION: Type 1 needs cement only. Type 2A needs cement and small augments. Type 2B NEEDS stems and augments. Type 3 NEEDS cones or allografts with stems. I assess femur and tibia separately because often different grades.

VIVA SCENARIOStandard

EXAMINER

"How do you determine what level of constraint is needed in revision TKA? A patient has aseptic loosening with moderate varus deformity - walk me through your constraint decision."

EXCEPTIONAL ANSWER

Constraint level based on LIGAMENT INTEGRITY and GAP BALANCE assessed after component removal and cement debridement. Systematic assessment: LIGAMENT TESTING: (1) MCL - Most critical. Apply valgus stress at 0° and 90° flexion. Grade opening: Intact less than 5mm, stretched 5-10mm, incompetent greater than 10mm. (2) LCL - Apply varus stress, assess. (3) PCL - Usually absent or incompetent in loosening, less important because using PS or CCK construct. GAP ASSESSMENT: Measure extension and flexion gaps with spacers, assess medial-lateral balance and overall stability. CONSTRAINT SELECTION: POSTERIOR-STABILIZED (PS): MCL and LCL intact with less than 5mm opening, balanced gaps - UNCOMMON in revision for loosening because component loosening causes ligament attenuation from abnormal kinematics. CONSTRAINED CONDYLAR KNEE (CCK): MCL or LCL attenuated 5-10mm opening OR mildly incompetent 10-15mm opening OR flexion-extension gap imbalance less than 10mm not correctable with bone resection - MOST COMMON in revision for loosening. CCK has taller post and deeper cam providing 2-4° more varus-valgus constraint than PS. Excellent outcomes: 90% survivorship at 10 years with proper stem fixation. ROTATING HINGE: Severe MCL or LCL incompetence greater than 15mm opening OR global instability OR massive bone loss requiring large cones and stems OR failed CCK. For varus loosening case: Test MCL with valgus stress after cement removal - if MCL stretched 5-10mm, I use CCK. If MCL incompetent greater than 15mm from chronic varus loading, I use rotating hinge.