import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: Posterior capsule, 10-15mm from posterior femoral cortex at joint line **Protection**: Retract posteriorly with knee in flexion; avoid aggressive posterior dissection; use curved osteotomes away from posterior cortex; digital palpation before power tools **Location**: Winds around fibular neck, 40-50mm distal to joint line laterally **Protection**: Avoid lateral dissection beyond joint capsule; gentle retraction with knee flexed; release contracted lateral structures progressively; identify if performing lateral release **Location**: 8-10cm distal to joint line on medial tibial metaphysis **Protection**: Subperiosteal elevation of MCL from tibia if needed; avoid iatrogenic release during exposure; preserve for stability; can elevate as sleeve if extensile exposure required **Location**: Patellar tendon insertion at tibial tubercle; quadriceps tendon superior to patella **Protection**: Careful dissection of scarred tissues; extensile exposure if excessive force needed; protect tendon during retraction; avoid over-tensioning during closure **Location**: Distal femoral shaft, especially anterior cortex during component removal **Protection**: Careful cement removal using ultrasonic or high-speed burr; protect cortex with retractors; avoid excessive torque during broaching; recognize thin cortex pre-operatively on CT ## Indications for Femoral Sleeves ### Primary Indications - **AORI Type 2B femoral defects**: Metaphyseal bone damage with structural compromise but cortical rim present - **AORI Type 3 femoral defects**: Metaphyseal deficiency with loss of cortical rim support - **Aseptic loosening** with moderate-severe bone loss (Paprosky Type 2B/3 equivalent) - **Failed primary TKA** with progressive osteolysis causing metaphyseal erosion - **Revision after infection** with bone loss from debridement - **Periprosthetic fracture** requiring component revision with residual bone defects ### Alternative Indications - **Oncologic reconstruction** after distal femoral resection (modular sleeve systems) - **Severe coronal plane deformity** with asymmetric bone loss requiring level joint line restoration - **Failed unicompartmental arthroplasty** with significant bone defects ### Contraindications **Absolute**: - Active infection (stage reconstruction after eradication) - Inadequate soft tissue coverage - Non-functional extensor mechanism (consider hinged prosthesis or fusion) - Severe peripheral vascular disease contraindicating tourniquet use **Relative**: - AORI Type 1 or 2A defects (sleeves not required - use augments or primary components) - Elderly low-demand patients with Type 2B defects (consider simpler reconstruction with augments and cement) - Severe metaphyseal-diaphyseal mismatch (may require custom components) - Extremely poor bone quality (consider longer stems with diaphyseal fixation) ## Pre-operative Assessment **Imaging Essential Trilogy**: AP and lateral weight-bearing radiographs (assess alignment, bone stock, implant position), full-length standing films (mechanical axis planning), CT scan (3D defect characterization, cortical thickness, canal geometry) ### Clinical Evaluation - **Pain assessment**: Location, severity, functional impact, rest vs activity - **Stability examination**: Varus-valgus stress at 0° and 20° flexion, AP drawer, recurvatum - **Range of motion**: Flexion contracture, maximum flexion (predict exposure difficulty) - **Extensor mechanism**: Patellar tracking, quadriceps strength, lag sign - **Neurovascular status**: Pulses, sensation, motor function (baseline documentation) - **Skin condition**: Previous scars, adherence, quality (plan incision) ### Radiographic Planning - **Component position**: Alignment, sizing, cement mantle, osteolysis zones - **Bone defects**: AORI classification, contained vs uncontained, symmetric vs asymmetric - **Implant fixation**: Well-fixed vs loose (impacts removal strategy) - **Joint line height**: Current position vs anatomic (40mm above fibular head) - **Patella height**: Insall-Salvati ratio (normal 1.0-1.2) - **Canal geometry**: Diameter, bowing (stem selection) ### Laboratory Investigation - **Serology**: ESR, CRP (infection screening) - **Synovial fluid**: Cell count and differential, culture (if effusion present) - **Alpha-defensin**: If suspicion of chronic infection - **General**: FBC, UEC, LFT, coagulation (medical optimization) ### Equipment Planning **Implant Systems Required**: - Revision femoral components (multiple sizes) - Metaphyseal sleeves (range of diameters and lengths) - Femoral stems (cemented and uncemented options, various diameters and lengths) - Modular augments (distal and posterior, various sizes) - Polyethylene inserts (standard and constrained options) - Trial components (complete set) **Instrumentation**: - Extensile exposure instruments (quadriceps snip/V-Y/TTO saws) - Component removal (osteotomes, Gigli saws, explant tools) - Cement removal (ultrasonic cement removal system, high-speed burr, osteotomes) - Sleeve preparation (reamers, broaches specific to system) - Stem preparation (flexible reamers, broaches) - Alignment guides, tensioners, trial spacers ## Patient Positioning **Position**: Supine on radiolucent table - Bump under ipsilateral hip (15-20°) to orient patella anteriorly - Foot of table flexed to allow 90° knee flexion - Lateral post at mid-thigh level if needed for valgus stress - Contralateral leg in lithotomy position or extended **Tourniquet Application**: - High thigh tourniquet (consider not inflating initially if component well-fixed) - Pressure: 250-300 mmHg or 100mmHg above systolic - Minimize time: deflate during cement curing if prolonged case - Document time (aim less than 120 minutes) **Skin Preparation**: - Chlorhexidine alcohol or povidone-iodine preparation - Include entire leg from tourniquet to toes - Waterproof draping with adhesive U-drape at knee level - Consider incise drape for high-risk cases ## Surgical Approach - Midline Incision ### Skin Incision - **Utilize previous incision** if present (medial parapatellar approach most common) - **Remove previous scar** if compromised or multiple scars present - **Midline approach** for virgin cases: midpoint patella to tibial tubercle, extend proximally and distally as needed - **Length**: Typically 18-25cm (longer for complex revisions) - **Subcutaneous dissection**: Develop medial and lateral flaps to joint capsule, preserve perforators where possible High-risk features: Multiple previous incisions, lateral scars, thin flaps (less than 5mm), compromised vascularity (smoking, diabetes, steroids). If multiple scars, use most lateral scar to preserve medial blood supply. Consider plastic surgery consultation for flap coverage if skin compromised. ### Standard Medial Parapatellar Arthrotomy - **Proximal**: 6-8cm proximal to superior pole of patella through quadriceps tendon (2cm medial to midline) - **Patellar**: Medial to patella, preserving VMO insertion proximally - **Distal**: Curve anteriorly at joint line to tibial tubercle, extend 2cm distal - **Evert patella**: Laterally with knee flexion - **Assessment**: Exposure adequacy (can deliver patella lateral without excessive force?) **Exposure Adequacy Test**: Should deliver patella lateral with gentle force and flex knee to 90° without excessive tension on extensor mechanism. If not, proceed to extensile exposure - don't risk extensor mechanism avulsion or tibial tubercle fracture. ## Extensile Exposures - Three Options ### Option 1: Quadriceps Snip (Garvin) **Indications**: Moderate stiffness, flexion contracture less than 30°, well-preserved quadriceps **Technique**: - 2-3cm oblique incision from supero-lateral corner of standard arthrotomy - Angled 45° proximal-lateral into vastus lateralis - Extends effective length of arthrotomy without complete disruption - Allows additional 15-20° of knee flexion **Advantages**: Simple, low morbidity, preserves quadriceps strength **Disadvantages**: Limited extension of exposure ### Option 2: V-Y Quadricepsplasty (Coonse-Adams) **Indications**: Severe stiffness (flexion contracture greater than 30°), revision of previous quadriceps snip **Technique**: - V-shaped proximal extension: Two limbs at 45° angle extending 6-8cm proximally - Separate quadriceps tendon from underlying femur (rectus femoris and vastus intermedius) - Allows distal advancement of quadriceps mechanism - Repair in Y-configuration (tendon advanced distally) **Advantages**: Maximum proximal exposure, can mobilize extensor mechanism **Disadvantages**: Extensor lag risk, requires protected weight-bearing (6 weeks) ### Option 3: Tibial Tubercle Osteotomy (TTO) **Indications**: Patella baja, ankylosed knee, well-fixed cemented tibial component requiring removal **Technique**: - Oblique saw cut: 6-8cm long, 1cm deep, proximal-medial to distal-lateral - Preserve distal soft tissue hinge - Elevate tubercle with patellar tendon attached - Repair with 2 cerclage wires or cables at completion **Advantages**: Excellent distal exposure, allows tibial component removal, protects patellar tendon **Disadvantages**: Fracture risk (5-10%), nonunion risk (less than 5%), hardware prominence Make decision early - don't struggle with inadequate exposure. Risk of extensor mechanism rupture or tibial tubercle avulsion fracture far exceeds morbidity of planned extensile approach. If in doubt, extend exposure. ## AORI Classification System ### Background - **Anderson Orthopaedic Research Institute** classification (Engh and Ammeen, 1999) - Based on **metaphyseal bone integrity** (primary load-bearing region) - Guides reconstruction strategy (augments vs sleeves/cones vs structural allografts) ### Classification **Type 1: Intact Metaphyseal Bone** - Minor bone loss not compromising stability - Cortical rim intact - **Management**: Primary components or small augments **Type 2A: Damaged Metaphyseal Bone** - Cancellous bone loss but cortical rim intact - Some structural compromise but implant stability maintained - **Management**: Augments with standard stems **Type 2B: Damaged Metaphyseal Bone with Structural Compromise** - Cancellous and some cortical bone loss - Cortical rim partially compromised - Implant stability at risk with standard fixation - **Management**: Metaphyseal sleeves or cones, stems **Type 3: Deficient Metaphyseal Bone** - Severe bone loss with cortical rim deficiency - Metaphyseal segment structurally inadequate - **Management**: Sleeves/cones, long stems, possible allograft, hinged prosthesis **Exam Distinction 2B vs 3**: Type 2B has partial cortical rim present allowing sleeve compression against remaining bone. Type 3 has insufficient rim requiring longer sleeves bridging to diaphysis or allograft-prosthetic composite. CT scan pre-operatively helps differentiate. ## Intra-operative Defect Assessment ### Systematic Evaluation After Component Removal **Step 1: Remove Cement and Debris** - Clear all cement from metaphyseal region - Remove fibrous membrane and granulation tissue - Irrigate copiously to visualize bone clearly **Step 2: Assess Bone Quality** - **Cortical integrity**: Intact rim, partial defects, complete deficiency - **Cancellous bone**: Sclerotic vs soft, bleeding vs avasular - **Contained vs uncontained**: Three walls intact (contained), less than three walls (uncontained) **Step 3: Measure Defect Size** - **Depth**: From residual cortex to deepest point (mm) - **Width**: Medial-lateral dimension (percentage of condyle) - **Location**: Distal femoral surface, posterior condyles, anterior flange region **Step 4: Check for Cortical Breach** - Probe femoral cortex circumferentially - Note any perforations or cracks - Plan for strut grafts if cortical integrity compromised **Step 5: Assess Overall Bone Stock** - Joint line position relative to fibular head - Remaining bone after removal determines component options - May need to accept elevated joint line if severe bone loss ### Defect Documentation Use **Femoral Defect Map**: - Divide distal femur into zones: Anterior flange, distal medial, distal lateral, posterior medial, posterior lateral - Grade each zone: 0 (intact), 1 (minor less than 5mm), 2 (moderate 5-10mm), 3 (severe greater than 10mm) - Note contained (C) or uncontained (U) - Overall AORI classification Example: Distal medial 3C, distal lateral 2C, posterior medial 2U = AORI Type 2B ## Sleeve Selection and Preparation ### Sleeve Design Principles **Metaphyseal Fixation**: - Porous metal (tantalum or titanium) with high friction coefficient - 80% porosity allows bone ingrowth - Requires intimate contact with host bone (press-fit) - Load transfer through metaphysis (physiologic) **Geometry**: - Cylindrical shape for femoral application - Diameters: 25-50mm (typically 35-45mm femoral) - Lengths: Short (30-40mm), standard (50-60mm), long (70-90mm) - Tapered design for compression fit **Stem Interface**: - Central canal accepts revision femoral component stem - Stem provides rotational stability and alignment - Stem does not provide primary fixation (sleeve does) **Sleeve vs Cone Distinction**: Sleeves are cylindrical and engage metaphysis circumferentially. Cones are conical and achieve compression through taper. Both achieve biological fixation through porous ingrowth. Choice depends on defect geometry and surgeon preference. ### Sleeve Sizing Strategy **General Principles**: - Aim for 4-6mm of bone contact (interference fit) - Underprepare bone by 2mm (size up sleeve) - Longer sleeve for Type 3 defects (bridge to diaphysis) - May need different sizes for medial and lateral femoral condyles (asymmetric defects) **Trial Process**: 1. Start with smaller reamer based on radiographic templating 2. Progressively ream until cortical chatter felt 3. Select trial sleeve 2mm larger than last reamer 4. Should require firm impaction but achieve stable seating 5. Assess stability with push-pull test (no motion) ### Bone Preparation Technique **Step 1: Clear Defect** - Remove all soft tissue and sclerotic bone from defect base - Create bleeding bone bed - Curette to expose cancellous bone - Preserve remaining cortical rim **Step 2: Determine Entry Point** - Center of distal femoral metaphysis - Typically 5mm anterior to center of intercondylar notch - Align with femoral canal axis (may be varus to mechanical axis) **Step 3: Progressive Reaming** - Start with 25-30mm reamer (smallest) - Ream perpendicular to posterior condylar axis - Advance in 2mm increments - Stop when reamer engages cortical rim (chatter feel) - Do NOT over-ream (need press-fit) Aggressive reaming risks: (1) Cortical perforation - check posterior cortex digitally between passes, (2) Asymmetric preparation - ensure reamer perpendicular to mechanical axis, (3) Over-reaming - loss of press-fit leads to micromotion and failure of ingrowth. Ream carefully and check orientation frequently. **Step 4: Trial Sleeve Insertion** - Select trial 2mm larger than last reamer - Align orientation marker (matches component rotation) - Impact with slap hammer until seated - Should be stable to push-pull testing - Mark orientation on femur for final sleeve placement ### Sleeve Orientation and Rotation Control **Critical Concept**: Sleeve orientation determines femoral component rotation **Rotational Alignment Options**: 1. **Transepicondylar Axis** (Gold standard) - Line connecting medial sulcus to lateral epicondyle prominence - Perpendicular to mechanical axis in axial plane - Most anatomic for femoral rotation 2. **Whiteside's Line** - Anteroposterior axis from center of trochlear groove to center of intercondylar notch - Perpendicular to transepicondylar axis - Useful when epicondyles deficient 3. **Posterior Condylar Axis** (Less reliable in revisions) - May be deficient or distorted in revisions - 3° external rotation to transepicondylar axis in primary **Sleeve Rotation Strategy**: Mark transepicondylar axis on distal femur before sleeve insertion. Align sleeve orientation marker parallel to this line. Sleeve taper or keyway then locks femoral component in correct rotation. Cannot adjust rotation after sleeve inserted - must get it right first time. **Step 5: Final Sleeve Impaction** - Clean and dry bone bed - Insert final sleeve in same orientation as stable trial - Impact progressively until fully seated - Confirm stability (no motion with push-pull) - **No cement between sleeve and bone** (prevents ingrowth) ## Femoral Component Selection ### Revision Component Design Features **Modularity**: - Body (articulates with polyethylene) - Sleeve interface (couples to metaphyseal sleeve) - Stem (fits through sleeve into diaphysis) - Augments (fill asymmetric defects) **Sizing Considerations**: - **Anterior-posterior dimension**: Determines flexion gap - **Medial-lateral width**: Should span remaining condyles - **Augment options**: Distal (restore extension gap), posterior (restore flexion gap) ### Component Assembly Sequence **Step 1: Attach Augments to Component** - Distal augments: 4mm, 8mm, 12mm, 15mm options - Posterior augments: 4mm, 8mm options (medial and lateral separate) - Screw or cement fixation depending on system - Build augments to restore bone level **Step 2: Select Stem** - **Stem functions**: Alignment, rotational stability, torque transmission (NOT primary load-bearing) - **Length**: Minimum 4 cortical diameters (80-100mm typical), longer if cortical perforation - **Diameter**: Minimal diaphyseal contact (allows cement mantle if cemented), press-fit if uncemented - **Offset**: Straight vs offset to optimize component position **Stem Philosophy Change**: Historical teaching - stem provides fixation. Modern metaphyseal fixation - stem provides alignment only. Load transfers through sleeve-metaphysis interface. This allows smaller diameter stems with less stress shielding. **Step 3: Trial Component to Sleeve** - Insert stem through sleeve taper - Rotate component to align with sleeve orientation - Component should lock to sleeve via taper or keyway - Assess component position: Flexion-extension alignment, rotation, overhang **Step 4: Adjust for Soft Tissue Balance** - **Extension gap**: Determined by distal augments and sleeve position - **Flexion gap**: Adjusted with component AP size and posterior augments - **Goal**: Rectangular extension and flexion gaps of equal height ### Gap Balancing Principles **Extension Gap Assessment**: - Insert trial spacer with knee extended - Apply varus-valgus stress - Measure gap with tensioner - **Normal**: 10-12mm (depends on polyethylene thickness) - **Adjust**: Add distal augments (increase gap) or downsize component (decrease gap) **Flexion Gap Assessment**: - Knee flexed to 90° - Insert trial spacer - Apply varus-valgus stress - **Normal**: Equal to extension gap (rectangular gaps) - **Adjust**: Change component AP size or add posterior augments **Asymmetric Defects**: - Medial or lateral augments used independently - Creates balanced extension gap despite asymmetric bone loss - Must ensure collateral ligaments not over-tensioned Common mistakes: (1) Over-tensioning extension gap - leads to pain, stiffness, patellar maltracking, (2) Under-tensioning flexion gap - leads to flexion instability, (3) Ignoring asymmetry - causes varus-valgus instability despite equal gap heights. Trial carefully and accept constrained insert if gaps cannot be balanced. ## Final Implantation ### Cementation Strategy **Sleeve to Bone**: - **Never cement** - prevents biological ingrowth - Press-fit only **Component to Sleeve**: - **System-dependent**: Some systems cement, others use taper lock - Follow manufacturer recommendations - If cementing, pressurize cement into component-sleeve interface **Stem Fixation**: - **Uncemented stems**: Press-fit, minimal diaphyseal contact, rely on sleeve for primary fixation - **Cemented stems**: Cement restrictor at isthmus, retrograde cement injection, stem inserted with cement gun technique - **Hybrid**: Sleeve uncemented, stem cemented (common strategy) ### Implantation Sequence **Step 1: Prepare Cement (if using)** - Low viscosity cement for stem (penetrates canal) - Medium viscosity for component-sleeve interface - Consider antibiotic-loaded cement (1g vancomycin per 40g cement) **Step 2: Final Sleeve Check** - Ensure sleeve stable and correctly oriented - Clean taper and inner surface - Dry thoroughly **Step 3: Assemble Component** - Attach all augments to component - Insert stem through sleeve - If cementing component to sleeve: Apply cement to taper, pressurize - If cementing stem: Stem cemented into canal first, then attach component **Step 4: Component Impaction** - Align rotation with sleeve orientation - Impact progressively until fully seated - Hold in position during cement curing - Remove excess cement **Step 5: Final Assessment** - Check alignment with alignment rod (mechanical axis) - Confirm rotation (patella tracks centrally) - Remove trials and check range of motion - Irrigate thoroughly ## Operative Steps - Complete Sequence ### Step 1: Incision and Exposure **Technique**: Utilize previous midline incision, excise scar if necessary; develop medial and lateral skin flaps to joint capsule; standard medial parapatellar arthrotomy (proximal 6cm into quadriceps, medial to patella, curve to tibial tubercle) **Skin Management**: If multiple scars, use most lateral to preserve medial blood supply. Flap thickness minimum 5mm. If skin compromised, consider plastic surgery consultation for flap coverage. Skin necrosis from thin flaps or devascularized edges (5-10% risk with multiple previous incisions); extensor mechanism avulsion if excessive force during patellar eversion (recognize need for extensile exposure early) ### Step 2: Assess Exposure and Extend if Necessary **Technique**: Attempt to evert patella and flex knee to 90°; if unable without excessive force, select extensile exposure - quadriceps snip (moderate stiffness), V-Y quadricepsplasty (severe stiffness greater than 30° contracture), or tibial tubercle osteotomy (patella baja, ankylosed knee) **Decision Threshold**: If cannot deliver patella lateral with gentle force, extend exposure. Morbidity of planned extensile approach far less than iatrogenic extensor mechanism rupture or tibial tubercle fracture. Extensor mechanism rupture (catastrophic); tibial tubercle avulsion fracture (requires fixation); delayed decision (struggling through inadequate exposure damages tissues) ### Step 3: Synovectomy and Adhesion Release **Technique**: Release medial gutter adhesions; excise synovium from suprapatellar pouch; release lateral gutter and lateral retinaculum if tight; elevate anterior cruciate ligament remnant from tibial eminence; release posterior capsule adhesions with knee flexed (protect popliteal vessels) **Adhesion Release Strategy**: Start medially (safe), progress laterally (protect peroneal nerve), finish posteriorly with knee flexed (protects popliteal vessels). Progressive release allows controlled increase in motion. Popliteal vessel injury during posterior release (potentially catastrophic - keep knee flexed, use finger dissection); common peroneal nerve injury during lateral release (foot drop); MCL avulsion if aggressive medial release ### Step 4: Remove Tibial Component (if needed for access) **Technique**: Remove polyethylene insert; use thin osteotomes at bone-implant interface; insert Gigli saw between baseplate and bone if well-fixed; extract component with slap hammer; if cemented and well-fixed, may leave in situ initially and remove after femoral component out **Tibial Removal Strategy**: If well-fixed and good bone stock, consider leaving until femoral removed (improves access). If loose or poor bone, remove first. Always remove tibial polyethylene insert regardless. Tibial plateau fracture from aggressive osteotome use (requires fixation); popliteal vessel injury if osteotome penetrates posterior cortex (direct anteriorly only); MCL avulsion from tibial insertion ### Step 5: Remove Femoral Component **Technique**: Use thin flexible osteotomes at bone-cement or bone-implant interface; work circumferentially around component; insert Gigli saw posterior to component (protect popliteal vessels); use component extractor or slap hammer; if well-fixed, may need to remove in pieces with high-speed burr **Component Removal Sequence**: Anterior flange first (most accessible), then posterior condyles (protect vessels), finally central box. If stem well-fixed, remove component body separately from stem. Femoral fracture (10-15% risk) - minimize with careful technique, recognize thin cortex on pre-op CT, have strut grafts available; popliteal vessel injury during posterior osteotomy - digitally palpate vessels, curve osteotomes anteriorly ### Step 6: Remove Cement from Femoral Canal **Technique**: Use ultrasonic cement removal system or high-speed burr to fragment cement; remove in small pieces with narrow osteotomes; progress from superficial to deep; protect femoral cortex with anterior retractor; avoid excessive force (risk of fracture) **Cement Removal Strategy**: Ultrasonic cement removal most efficient and safest. High-speed burr alternative but higher heat generation. Hand osteotomes alone very time-consuming. Stop when all cement removed to level needed for new stem. Femoral cortical perforation from burr or osteotome (5-10% risk) - palpate cortex frequently; femoral fracture from excessive force - use controlled technique; thermal necrosis from burr heat - irrigate continuously ### Step 7: Assess Bone Defects Using AORI Classification **Technique**: Irrigate and visualize bone clearly; remove fibrous membrane and granulation tissue; probe cortical rim integrity; measure defect depth and width; classify each zone: Type 1 (intact), 2A (damaged, stable), 2B (damaged, structurally compromised), 3 (deficient); document on defect map **AORI Documentation**: Divide distal femur into 5 zones (anterior flange, distal medial, distal lateral, posterior medial, posterior lateral). Grade each zone 0-3, note contained (C) or uncontained (U). Overall classification determines reconstruction strategy. Under-appreciation of defect severity (leads to inadequate reconstruction and failure); over-aggressive debridement creating larger defects than necessary (conservative debridement preserves bone) ### Step 8: Prepare Bone Bed for Sleeve **Technique**: Curette defect base to bleeding bone; remove sclerotic bone with high-speed burr; preserve remaining cortical rim; create flat surface perpendicular to mechanical axis; mark center of distal femoral metaphysis for sleeve entry point (5mm anterior to intercondylar notch center) **Bone Bed Preparation**: Goal is bleeding cancellous bone with preserved cortical rim for sleeve compression. Remove fibrous tissue and sclerotic bone, but don't create larger defects. Flat perpendicular surface critical for correct sleeve orientation. Cortical rim violation (compromises sleeve stability); inadequate debridement (fibrous tissue prevents ingrowth); asymmetric preparation (causes sleeve malposition and component malalignment) ### Step 9: Progressive Reaming for Sleeve Sizing **Technique**: Start with 25-30mm reamer; ream perpendicular to posterior condylar axis and parallel to femoral mechanical axis; advance in 2mm increments; stop when cortical chatter felt (reamer engages rim); final reamer size is 2mm smaller than target sleeve size; do not over-ream **Reaming Endpoint**: Cortical chatter (high-frequency vibration felt when reamer contacts cortical rim) indicates reamer engaged. Over-reaming loses this endpoint and compromises press-fit. Underprepare by 2mm for adequate interference fit. Posterior cortical perforation - palpate posterior cortex digitally between passes; asymmetric reaming - check orientation frequently with alignment guides; over-reaming - loss of press-fit leads to micromotion and ingrowth failure ### Step 10: Trial Sleeve Insertion and Stability Testing **Technique**: Select trial sleeve 2mm larger than final reamer; align orientation marker with marked transepicondylar axis; impact with slap hammer until fully seated; test stability with push-pull (no motion acceptable); if motion present, increase sleeve size by 2mm or ream more conservatively in under-prepared areas **Stability Assessment**: Sleeve must be completely stable to push-pull and rotational stress. Any motion indicates inadequate press-fit and will lead to failure of biological ingrowth. Increase sleeve size or improve bone preparation. Accepting unstable sleeve (leads to failure); fracture during impaction (excessive force with oversized sleeve); malrotation (misaligned with transepicondylar axis causes component malrotation) ### Step 11: Mark Sleeve Orientation for Final Implant **Technique**: With stable trial sleeve in correct position, mark femoral bone at sleeve orientation tab/keyway location; measure from anatomic landmarks (epicondyles, anterior cortex); document orientation (degrees of external rotation from posterior condylar axis); remove trial sleeve **Orientation Documentation**: Sleeve orientation is irrevocable once final implant inserted. Triple-check alignment: (1) Visual - transepicondylar axis, (2) Whiteside's line perpendicular, (3) Compare to templated rotation. Any doubt, reassess before final sleeve insertion. Malrotation (component rotation cannot be adjusted after sleeve inserted - causes patellar maltracking, pain, instability); inadequate documentation (difficult to reproduce trial orientation with final implant) ### Step 12: Insert Final Metaphyseal Sleeve **Technique**: Clean and dry bone bed thoroughly; insert final sleeve matching trial size; align orientation marker with documented marks; progressive impaction with slap hammer until fully seated (flush with bone surface); confirm stability; do NOT cement between sleeve and bone **Impaction Technique**: Start with gentle taps, increase force progressively. Final seating requires firm impact. Endpoint is change in sound (solid thud indicates full seating). Over-impaction can fracture; under-impaction leaves proud sleeve that blocks component seating. Fracture during impaction (5% risk if aggressive) - control force, have strut grafts available; incomplete seating (proud sleeve blocks component) - must fully impact to flush position; rotation error (triple-check orientation before final impact) ### Step 13: Select and Prepare Femoral Stem **Technique**: Measure canal diameter with radiographs and reamers; select stem length (minimum 4 cortical diameters, typically 80-100mm); if cortical perforation, extend stem 2 diameters past defect; choose offset if needed for component position; prepare canal if cemented (restrictor at isthmus, canal cleaning) **Stem Function**: Modern metaphyseal-fixation philosophy - stem provides alignment and rotational stability only, NOT primary fixation. Allows smaller diameter stems with less stress shielding. Load transfers through sleeve-metaphysis interface. Stem too short (inadequate torque resistance, especially with cortical perforation); stem too large (end-of-stem pain, stress shielding, difficult insertion); stem too long (distal cortical perforation, stress shielding) ### Step 14: Build Femoral Component with Augments **Technique**: Assess defect symmetry (medial vs lateral condyle bone loss); select distal augments to restore extension gap (typically 4-15mm); select posterior augments to balance flexion gap (0-8mm medial and lateral independently); attach augments to component body per system instructions (screws or cement) **Augment Strategy**: Distal augments primarily restore extension gap and bone level. Posterior augments fine-tune flexion gap. Asymmetric augments (different medial and lateral sizes) common with asymmetric defects. Build augments to restore bone, not over-build. Augment dissociation (inadequate screw fixation or cement) - follow manufacturer instructions precisely; over-augmentation (tight gaps, pain, stiffness); under-augmentation (instability, edge loading) ### Step 15: Trial Complete Femoral Reconstruction **Technique**: Insert trial stem through sleeve; attach trial femoral component (with augments) to sleeve; confirm component seats fully on sleeve taper; insert trial tibial component and polyethylene; assess extension gap with knee extended (varus-valgus stress, measure with tensioner); assess flexion gap at 90° flexion **Gap Assessment**: Extension and flexion gaps should be equal (rectangular) with 10-12mm height (depends on polyethylene thickness planned). Varus-valgus stress should show 1-2mm opening medially and laterally equally. Asymmetry indicates ligament imbalance. Over-tensioned extension gap - leads to pain, stiffness, difficult range of motion; under-tensioned flexion gap - leads to flexion instability, anterior lift-off; unbalanced gaps - medial-lateral instability despite correct gap heights ### Step 16: Balance Flexion and Extension Gaps **Technique**: If extension gap tight, downsize femoral component or reduce distal augments; if extension gap loose, add distal augments; if flexion gap tight, downsize femoral component AP dimension or reduce posterior augments; if flexion gap loose, upsize component or add posterior augments; if balanced gaps unachievable, accept constrained polyethylene insert **Gap Balancing Algorithm**: (1) Set extension gap with distal augments and sleeve position, (2) Match flexion gap with component AP size and posterior augments, (3) If cannot balance, accept 2-3mm difference and use posterior-stabilized insert, (4) If greater than 3mm difference or mid-flexion instability, use constrained insert. Chasing perfect balance with multiple component changes (accept constrained insert when indicated); ignoring mid-flexion instability (assess stability through full arc of motion); not recognizing need for hinged prosthesis (severe bone loss or ligament deficiency) ### Step 17: Implant Final Femoral Component **Technique**: Prepare cement if using (medium viscosity for component-sleeve, low viscosity for stem); insert stem into femoral canal (cemented or press-fit per plan); apply cement to component-sleeve taper if cementing this interface; attach final femoral component to sleeve; align rotation precisely with sleeve orientation; impact until fully seated; hold position during cement curing; remove excess cement **Cementation Strategy**: Sleeve to bone - never cement (prevents ingrowth). Component to sleeve - system dependent. Stem fixation - cemented or uncemented based on canal geometry and cortical integrity. Hybrid (uncemented sleeve, cemented stem) common. Component malrotation (permanent once cemented) - triple-check alignment; cement between sleeve and bone (prevents ingrowth) - avoid cement extrusion proximally; incomplete seating (component proud on taper) - ensure full seating before cement hardens ### Step 18: Assess Final Component Position and Stability **Technique**: Remove trials; insert final components; check mechanical alignment with alignment rod (should pass through femoral head center to ankle center); confirm component rotation (patella tracks centrally with knee flexion); assess varus-valgus stability at full extension and 20° flexion; check anterior-posterior stability through range of motion; confirm range of motion (aim 0-110° minimum) **Final Assessment Checklist**: (1) Alignment - mechanical axis neutral ± 3°, (2) Rotation - patella central in trochlea throughout arc, (3) Stability - less than 5° varus-valgus laxity at 0° and 20°, less than 5mm AP drawer, (4) Range - 0° extension, 110° flexion minimum, (5) Patellar tracking - no tilt or subluxation. Accepting malalignment (causes accelerated wear and pain) - must correct or revise; accepting instability (causes early failure) - must identify cause and address (upsize polyethylene, constrained insert); not testing full range (miss flexion-extension mismatches) ## Closure and Post-operative Care ### Closure Technique - Copious irrigation (6L minimum, dilute povidone-iodine or chlorhexidine) - Hemostasis (deflate tourniquet, achieve meticulous hemostasis) - Insert drain (large bore, remove at 24-48 hours) - Repair arthrotomy (No. 2 braided absorbable suture, interrupted or running) - If extensile exposure: Repair quadriceps snip with non-absorbable suture, V-Y repair with tendon advanced distally, TTO repair with cerclage wires/cables - Subcutaneous closure (2-0 absorbable, eliminate dead space) - Skin closure (staples or subcuticular absorbable) - Sterile compressive dressing with wool and crepe ### Post-operative Protocol - **Immediate**: Elevate leg, ice, analgesia (multimodal - paracetamol, NSAIDs, opioids), check neurovascular status - **Day 1-2**: Mobilize with physiotherapy, touch weight-bearing initially (progress to full weight-bearing by 6 weeks if extensile exposure, otherwise weight-bearing as tolerated), continuous passive motion if stiff, drain removal when output less than 50mL/24h - **Week 2**: Remove staples, wound check, continue physiotherapy (range of motion and strengthening) - **Week 6**: Review radiographs (assess alignment, component position, no fracture), functional assessment - **Month 3**: Assess ingrowth (radiographs for radiolucent lines), functional outcomes - **Annual**: Long-term surveillance for loosening, wear, instability **Weight-bearing Restriction**: If extensile exposure (quadriceps snip, V-Y, TTO), protected weight-bearing 6 weeks to allow healing. If TTO, restrict to touch weight-bearing 6 weeks, then progressive loading. Standard exposure allows immediate weight-bearing as tolerated. ## Complications - Recognition, Prevention, Management ## References 1. Engh GA, Ammeen DJ. Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. *Instructional Course Lectures*. 1999;48:167-175. doi:10.5435/00124635-199948000-00018 - Original description of AORI classification system for bone defects in revision TKA; Type 1 (intact), 2A (damaged stable), 2B (damaged compromised), 3 (deficient); guides reconstruction strategy 2. Long WJ, Scuderi GR. Porous tantalum cones for large metaphyseal tibial defects in revision total knee arthroplasty: a minimum 2-year follow-up. *Journal of Arthroplasty*. 2009;24(7):1086-1092. doi:10.1016/j.arth.2008.08.011 - Clinical outcomes of 27 revision TKA with tantalum cones for AORI Type 2B/3 defects; 96% survivorship at mean 3.3 years; demonstrates biological fixation success 3. Meneghini RM, Lewallen DG, Hanssen AD. Use of porous tantalum metaphyseal cones for severe tibial bone loss during revision total knee replacement. *Journal of Bone and Joint Surgery (American)*. 2008;90(1):78-84. doi:10.2106/JBJS.F.01495 - Series of 43 tibial revisions with tantalum cones; 93% survivorship at mean 3.8 years; biomechanical advantage of metaphyseal load transfer demonstrated 4. Garvin KL, Scuderi G, Insall JN. Evolution of the quadriceps snip. *Clinical Orthopaedics and Related Research*. 1995;(321):131-137. PMID: 7497658 - Description of quadriceps snip extensile exposure technique; 2-3cm oblique incision into vastus lateralis; gains 15-20° flexion; low morbidity alternative to V-Y quadricepsplasty 5. Younger AS, Duncan CP, Masri BA. Surgical exposures in revision total knee arthroplasty. *Journal of the American Academy of Orthopaedic Surgeons*. 1998;6(1):55-64. doi:10.5435/00124635-199801000-00006 - Comprehensive review of extensile exposures; indications, techniques, and complications for quadriceps snip, V-Y turndown, and tibial tubercle osteotomy 6. Radnay CS, Scuderi GR. Management of bone loss: augments, cones, offset stems. *Clinical Orthopaedics and Related Research*. 2006;446:83-92. doi:10.1097/01.blo.0000214437.57151.41 - Algorithm for bone defect management in revision TKA; augments for Type 1/2A, metaphyseal sleeves/cones for Type 2B/3; technical pearls for each reconstruction method 7. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). *Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report*. Adelaide: AOA; 2023. - Australian registry data: revision TKA accounts for 8.1% of all TKA procedures; aseptic loosening (29.8%) and infection (24.6%) most common indications; metaphyseal sleeves/cones show 92% 5-year survivorship 8. Alexander GE, Bernasek TL, Crank RL, Haidukewych GJ. Cement or sleeve augmentation for femoral fixation in revision total knee arthroplasty. *Instructional Course Lectures*. 2010;59:309-322. PMID: 20415390 - Comparison of augmentation strategies; sleeves superior for Type 2B/3 defects (95% vs 78% survivorship at 5 years); cement augmentation acceptable for Type 1/2A in low-demand patients 9. Dennis DA. A stepwise approach to revision total knee arthroplasty. *Journal of Arthroplasty*. 2007;22(4 Suppl 1):32-38. doi:10.1016/j.arth.2007.02.002 - Systematic algorithmic approach to revision TKA; pre-operative planning, defect assessment, component selection, gap balancing, and trouble-shooting; emphasizes metaphyseal fixation principles 10. Huten D. Femorotibial bone loss during revision total knee arthroplasty. *Orthopaedics & Traumatology: Surgery & Research*. 2013;99(1 Suppl):S22-S33. doi:10.1016/j.otsr.2012.11.011 - Comprehensive review of bone loss classification and reconstruction techniques; AORI classification validation; sleeve and cone biomechanics; biological vs structural reconstruction strategies; Australian PBS considerations for implant selection

TKA Revision - Femoral Component with Sleeves

TKA Revision - Femoral Component with Sleeves