import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: 10-15mm posterior to posterior capsule, risk during posterior osteophyte removal and PCL release **Protection**: Maintain knee flexion when working posteriorly, avoid posterior capsule penetration, use retractors anteriorly, gentle soft tissue technique **Location**: 15-20mm from lateral joint line at fibular neck, risk during valgus correction and lateral releases **Protection**: Gradual correction of valgus deformity, avoid excessive lateral retraction, identify nerve in severe valgus (>20°), maintain knee flexion during releases **Location**: Tibial tubercle, risk during arthrotomy and patellar eversion **Protection**: Stay 1cm medial to tubercle with arthrotomy, adequate medial release before eversion, gentle technique, avoid forced eversion with tight tissues **Location**: 5-8mm from medial joint line, superficial and deep layers **Protection**: Staged subperiosteal releases from tibia, avoid inadvertent cutting, preserve superficial MCL if possible, check stability after each release **Location**: 4-6mm anterior to distal femur, risk during femoral sizing and anterior cut **Protection**: Avoid oversizing femoral component, correct flexion of cutting block, verify no anterior notching (causes supracondylar fracture risk) **Primary Indications** 1. **Symptomatic tricompartmental knee osteoarthritis** - Most common indication (90% of cases) - Failed conservative management minimum 3-6 months (NSAIDs, physiotherapy, weight loss, injections, bracing) - Kellgren-Lawrence Grade 3-4 radiographic changes - Significant functional impairment (WOMAC, Oxford Knee Score) - Pain affecting quality of life and activities of daily living 2. **Inflammatory arthritis** - 5-8% of cases - Rheumatoid arthritis with end-stage destruction - Psoriatic arthritis, ankylosing spondylitis - Often younger patients, may require bilateral staged procedures - Address medical optimization (DMARD management, steroid minimization) 3. **Post-traumatic arthritis** - 2-5% of cases - Following tibial plateau fractures, distal femur fractures - Significant cartilage loss and malalignment - May have bone defects requiring augments or stems - Higher complexity, increased revision rate 4. **Avascular necrosis with collapse** - 1-2% of cases - Secondary arthritis from spontaneous osteonecrosis (SONK) - Corticosteroid-induced AVN - Sickle cell disease, Gaucher disease - May have focal defects requiring augmentation 5. **Failed osteotomy** - 1-2% of cases - Progressive arthritis after high tibial osteotomy (HTO) or distal femoral osteotomy (DFO) - Technical challenges from altered anatomy - May require custom cutting guides or computer navigation **Contraindications** **Absolute:** - Active infection (local or systemic) - Inadequate bone stock for fixation - Absent extensor mechanism - Neuropathic arthropathy (relative - may consider hinged TKR) - Severe peripheral vascular disease with ischaemia **Relative:** - Previous septic arthritis (ensure eradicated, minimum 2 years post-treatment) - Psychiatric illness affecting compliance - Severe obesity (BMI >40 - increased complications, consider delay for weight loss) - Active malignancy - Immunosuppression (HIV, chemotherapy - increased infection risk) **Evidence-Based Thresholds**: Know the Australian PBS criteria - age >55 years (or younger if inflammatory arthritis), severe symptoms >3 months despite conservative treatment, Kellgren-Lawrence Grade 3-4. AOANJRR 2023 shows 97.4% survivorship at 10 years for primary TKR, with best results in age 65-75 years. **Clinical Assessment** - Pain severity, location, mechanical vs inflammatory - Functional limitation (stairs, walking distance, night pain) - Previous surgery, infections, trauma - Medical comorbidities (cardiac, respiratory, renal, diabetes) - Medications (anticoagulants, immunosuppression, steroids) - Social factors (home setup, support, rehabilitation access) **Physical Examination** - Gait pattern, walking aids requirement - Knee ROM (active and passive, document flexion contracture) - Coronal deformity (varus/valgus, correctability to neutral) - Ligament stability (MCL, LCL, PCL - affects implant choice) - Extensor mechanism integrity - Hip and ankle examination (exclude referred pain, assess overall limb alignment) - Vascular status (pulses, perfusion) - Skin condition (previous scars, infection risk) **Radiographic Assessment** **Standard Views:** 1. **Standing AP** - assess joint space narrowing, osteophytes, sclerosis, alignment 2. **Lateral** - assess patellofemoral joint, flexion contracture, tibial slope 3. **Skyline patella** - assess patellar tracking, arthritis 4. **Long leg alignment** (hip-knee-ankle) - measure mechanical axis deviation, plan correction **Templating:** - Measure mechanical axis (normal 0° ± 3°) - Anatomic axis typically 5-7° valgus - Assess bone defects (may require augments, stems) - Plan component sizes (femur, tibia, patella) - Identify extra-articular deformity (may require osteotomy) **Special Investigations** - CT scan if severe deformity, bone loss, or previous fracture (aids surgical planning, custom guides) - MRI if concern for osteonecrosis, infection - Joint aspiration if concern for infection (synovial WCC >3000, polymorphs >90%) - DEXA scan if osteoporosis concern (affects component fixation choice) **Medical Optimization** - HbA1c <7% (ideally <6.5%) in diabetics - Smoking cessation minimum 6 weeks pre-op - Weight loss if BMI >35 (every 5 units BMI increases infection risk 10%) - Dental clearance (treat caries, periodontal disease) - Urology review if chronic UTI - Dermatology if psoriasis, eczema - MRSA screening and decolonization if positive - Cardiology clearance if significant CAD, valvular disease - Anemia correction (Hb >120 g/L, consider iron supplementation, EPO) - Active UTI (delay surgery, treat with culture-directed antibiotics) - Cellulitis, skin lesions (delay until resolved) - HbA1c >8% (defer for optimization) - Bacteremia from any source (identify and treat before proceeding) - Severe malnutrition (albumin <30 g/L, total lymphocyte count <1500) **Patient Position** - Supine on standard operating table - Lateral thigh support (prevents leg falling into varus during preparation) - Foot support allowing knee flexion to 90+ degrees (some surgeons use leg holder, others foot of bed) - Tourniquet on proximal thigh (ensure adequate padding) **Anesthesia** - General anesthesia OR spinal/epidural anesthesia - Consider regional block (femoral nerve block or adductor canal block) for post-op analgesia - Avoid complete motor block (need to assess extensor mechanism intra-op) **Tourniquet Application** - Inflate to 280-300mmHg (100mmHg above systolic BP) - Document tourniquet time (typical 60-90 minutes) - Minimize time <120 minutes (prolonged tourniquet >120 min increases complications) - Some surgeons avoid tourniquet (concerns about pain, VTE) but majority use for better visualization **Surgical Approach** - **Medial parapatellar arthrotomy** - gold standard for primary TKR (98% of cases in Australia) - Alternative approaches: midvastus, subvastus, lateral parapatellar (for valgus deformity) - Anterior midline skin incision allows access for revision surgery **Incision Planning** - Length: 5cm proximal to superior pole of patella to 2cm distal to tibial tubercle (typically 12-15cm) - Utilize previous scars if present (use most lateral if multiple scars, avoid multiple parallel incisions) - Ensure skin can be closed without tension (may need longer incision in obese patients) **Tourniquet Controversy**: AOANJRR data shows no difference in revision rates with or without tourniquet. RCTs show tourniquet reduces blood loss by 200-300mL but increases post-op pain and thigh swelling. Know both sides of debate - some surgeons release before closure to achieve hemostasis, others keep inflated until wound closed. ### Step 1: Exsanguination and tourniquet inflation Exsanguinate limb with Esmarch bandage from toes to thigh, then inflate tourniquet to 280-300mmHg. Document tourniquet inflation time. **Tourniquet Settings**: Pressure should be 100mmHg above systolic BP. Typical range 280-300mmHg. Pressures <250mmHg risk inadequate hemostasis, >350mmHg risk nerve injury. Always document time and pressure for medicolegal reasons. Risk of tourniquet palsy if >120 minutes, skin burns if poor padding, compartment syndrome if excessively tight. Check tourniquet function before starting surgery. --- ### Step 2: Skin incision Make anterior midline skin incision from 5cm proximal to superior pole of patella to 2cm distal to tibial tubercle. Deepen through subcutaneous fat to expose prepatellar bursa. **Incision Technique**: Midline incision preserves blood supply to both medial and lateral skin flaps (reduces skin necrosis risk). If previous scars present, use most lateral scar and excise old scar tissue. Avoid parallel incisions <5cm apart (skin necrosis risk). Avoid excessive skin flap undermining (>2-3cm from incision) - causes skin necrosis. Maintain full-thickness flaps including subcutaneous fat. Handle skin edges gently with skin hooks not forceps. --- ### Step 3: Develop subcutaneous flaps Develop full-thickness subcutaneous flaps medially and laterally to expose the extensor mechanism. Identify and excise prepatellar bursa. **Flap Development**: Develop flaps in plane just superficial to extensor mechanism. Include all subcutaneous fat with skin (preserves blood supply). Extend medially to MCL, laterally to lateral retinaculum. Use electrocautery for hemostasis. --- ### Step 4: Medial parapatellar arthrotomy Perform standard medial parapatellar arthrotomy: 1. Start 1cm medial to tibial tubercle 2. Extend proximally 1cm medial to medial border of patella 3. Curve obliquely into quadriceps tendon at junction of medial 1/3 and central 1/3 4. Extend 8-10cm into vastus medialis obliquus (VMO) **Arthrotomy Landmarks**: Staying 1cm medial to patella preserves lateral geniculate vessels (main blood supply to patella - enters at mid-lateral border). Inadequate proximal extension into VMO prevents safe patellar eversion. Some surgeons make small lateral release of retinaculum to aid eversion. Lateral geniculate artery enters patella at mid-lateral border. Medial parapatellar approach preserves this. Multiple previous surgeries may compromise blood supply - consider not resurfacing patella if concern for avascular necrosis. --- ### Step 5: Patellar eversion and exposure Evert patella laterally and externally rotate tibia. Flex knee to 90 degrees. Place Hohmann retractor under lateral femoral condyle to protect lateral structures. **Safe Eversion Technique**: Adequate medial release is essential - if cannot evert easily, extend arthrotomy proximally into VMO or perform small medial capsular release from tibia. Forced eversion risks patellar tendon avulsion (catastrophic complication). Some surgeons avoid eversion in stiff knees - dislocate patella laterally instead. Most common cause is forced eversion without adequate medial release. If avulsion occurs, requires immediate repair with suture anchors or transosseous tunnels + augmentation (Achilles allograft or synthetic mesh). Maintain 1cm margin from tubercle with all cuts and releases. --- ### Step 6: Excise anterior soft tissues Excise medial and lateral menisci, ACL, hypertrophic synovium, and osteophytes from anterior femur and tibia. Clear anterior compartment to improve visualization. **Cruciate Management**: ACL always excised. PCL handling depends on implant choice - retain for cruciate-retaining (CR) design, sacrifice for posterior-stabilized (PS) design. If PCL deficient or attenuated, must use PS design or constrained implant. Remove all osteophytes to avoid overstuffing joint. --- ### Step 7: Distal femoral resection Establish distal femoral resection using intramedullary (IM) or extramedullary (EM) guide: - **Resection amount**: 9-10mm from less worn condyle (typically lateral in varus knee, medial in valgus knee) - **Alignment**: 5-7° valgus to anatomic axis (equals 0° to mechanical axis) - **Entry point for IM guide**: Center of intercondylar notch, anterior to origin of PCL **Mechanical vs Anatomic Axis**: Mechanical axis of femur is straight from hip center to knee center. Anatomic axis is 5-7° valgus to mechanical axis. Distal femoral cut is perpendicular to mechanical axis (=5-7° valgus to anatomic axis). IM guide uses anatomic axis so add 5-7° valgus, EM guide measures from hip center so 0° to mechanical axis. Risk of femoral fracture during guide insertion, fat embolism from IM canal pressurization. Contraindicated if severe femoral deformity, previous femoral fixation, hip arthroplasty with long stem. Use EM guide in these cases. --- ### Step 8: Proximal tibial resection Perform proximal tibial resection using extramedullary guide: - **Depth**: 10mm from less worn plateau (typically lateral in varus knee) - **Alignment**: Perpendicular to mechanical axis (0° coronal plane) - **Posterior slope**: 3-7° (match native slope, typical 5°) - **EM guide alignment**: Align with center of ankle joint **Tibial Resection Depth**: Minimum 2mm required for stable component seating. Typical 8-10mm total resection. In varus knee, resect 10mm from lateral plateau (worn medial may have only 2-4mm resection). Use stylus to verify depth before cutting. Preserve tibial tubercle attachment - stay >1cm medial to tubercle. Over-resection increases constraint forces (accelerates loosening, requires thicker poly). Under-resection leaves eburnated bone (poor cement penetration). Excessive posterior slope >7° increases flexion laxity and ACL stress in CR knee. Posterior slope <3° causes tight flexion gap and limited flexion. --- ### Step 9: Femoral component sizing and rotation Size femoral component to match anteroposterior dimension of distal femur. Establish femoral rotation using multiple landmarks: **Three Key Landmarks:** 1. **Posterior condylar axis** - Add 3° external rotation (accounts for normal 3° external rotation of lateral condyle) 2. **Transepicondylar axis** - Line from medial sulcus to lateral epicondyle (represents true 0° rotation) 3. **Whiteside's anteroposterior line** - Line from center of trochlear groove to center of intercondylar notch (perpendicular to this gives 0° rotation) Verify with flexion gap assessment - should be rectangular, parallel to tibial cut, equal medial-lateral dimensions. **Why Femoral Rotation Matters**: Internal rotation causes: (1) Patellar maltracking with lateral subluxation, (2) Trapezoidal flexion gap (tight lateral, loose medial = instability), (3) Anterior knee pain, (4) Increased polyethylene wear. External rotation >5° causes medial flexion gap tightness and medial patellar subluxation (rare). Aim for 3° external rotation to posterior condylar axis. If landmarks disagree by >5°, suggests bony dysplasia, hypoplasia (inflammatory arthritis), or previous fracture. In this case, prioritize: (1) Transepicondylar axis (most reliable), (2) Balanced rectangular flexion gap, (3) Posterior condylar axis +3° (least reliable in dysplasia). --- ### Step 10: Anterior, posterior, and chamfer femoral cuts Perform femoral cuts using sizing guide: - **Anterior cut** - Verify no anterior notching of cortex (causes supracondylar fracture risk) - **Posterior cuts** - Ensure complete resection of posterior condyles (prevents tight flexion gap) - **Chamfer cuts** - Anterolateral and anteromedial chamfers complete femoral preparation **Anterior Notching**: Occurs if femoral component oversized or cutting block placed in excessive flexion. Increases supracondylar fracture risk 5-fold. If notch occurs, consider downsizing component, using augments to avoid further resection, or prophylactic plate fixation if >3mm deep notch. --- ### Step 11: Soft tissue balancing and gap assessment Assess extension and flexion gaps using laminar spreaders or tensor device. Perform soft tissue releases as needed to achieve balanced rectangular gaps. **For Varus Deformity** (medial tightness) - Staged medial releases: 1. Release deep medial collateral ligament (dMCL) subperiosteally from tibia 2. Release posteromedial capsule 3. Release semimembranosus insertion 4. Release posterior oblique ligament (POL) 5. Check balance with spacers AFTER EACH RELEASE **For Valgus Deformity** (lateral tightness) - Staged lateral releases: 1. Release iliotibial band (ITB) from Gerdy's tubercle 2. Release popliteus tendon 3. Release lateral capsule posteriorly 4. Release lateral collateral ligament (LCL) if needed (rare, <5% of cases) 5. Identify and protect common peroneal nerve before extensive lateral release **Goal**: Equal medial-lateral laxity 1-2mm in both extension and flexion, rectangular flexion gap parallel to tibial cut. **Balancing Principles**: Tight extension gap = resect more distal femur or proximal tibia. Tight flexion gap = downsize femoral component or resect more posterior femur. Asymmetric gaps = soft tissue releases. Gap differential >2mm requires releases. Never accept instability - will cause early failure and patient dissatisfaction. Releasing too much (especially LCL in valgus knee or superficial MCL in varus knee) causes gross instability requiring constrained implant or hinged knee. Always release in stages and check balance after each step. If severe deformity >20°, consider constrained condylar knee (CCK) rather than extensive releases. --- ### Step 12: Patellar preparation Resect patella using freehand technique or saw guide: - **Composite thickness**: Minimum 15mm bone + prosthesis (thinner = fracture risk) - **Resection technique**: Parallel to anterior patellar surface, aim for symmetric resection - **Peg placement**: Central in patella, avoid medial or lateral placement (causes maltracking) - **Thickness measurement**: Use caliper to measure native thickness, resect amount equal to patellar button thickness **Patellar Resurfacing Debate**: In Australia, 95% of surgeons routinely resurface patella (AOANJRR data). Non-resurfacing has 20-30% anterior knee pain rate vs 10% with resurfacing. If not resurfacing, denervate patella by drilling multiple 2mm holes and perform rim osteophyte excision. Avoid resurfacing if patella <20mm thick, previous patellar fracture, or avascular necrosis risk. Composite thickness <15mm increases fracture risk 10-fold. Eccentric reaming causes stress concentration and fracture. Over-resection cannot be corrected - if occurs, avoid patellar resurfacing and denervate instead. Intra-operative fracture requires cerclage wire fixation ± component removal. --- ### Step 13: Trial reduction and assessment Insert trial components with appropriate polyethylene thickness (typically 9-11mm): - **ROM**: Should achieve 0-5° hyperextension and 110-120° flexion minimum - **Stability**: Equal medial-lateral laxity 1-2mm in extension and flexion - **Patellar tracking**: Patella tracks centrally through full ROM without lateral subluxation - **No impingement**: No anterior femoral component impingement in hyperextension, no tibial polyethylene overhang - **No lift-off**: Flexion to 90° should not cause tibial component lift-off (indicates oversized femur or tight flexion gap) **Polyethylene Thickness**: Most common thickness 9-11mm. Thinner <9mm increases wear and deformation, requires tighter soft tissues (not ideal). Thicker >15mm indicates excessive bone resection or lax soft tissues, increases constraint forces and loosening risk. If need thick poly >15mm, assess for over-resection or ligament insufficiency - may need stems or constrained implant. Do not proceed to cementation until satisfied with ROM, stability, and tracking. Making adjustments after cementing is extremely difficult. If instability, identify pattern (flexion vs extension, medial vs lateral) and correct with releases, component changes, or increased constraint. --- ### Step 14: Component cementation Clean and dry all bone surfaces. Pulse lavage with 1-2L saline. Dry with suction and sponges. Mix antibiotic-loaded bone cement (gentamicin or tobramycin). **Cementation sequence:** 1. **Tibial component** - Apply cement to undersurface and stem, pressurize into tibial surface with finger, insert component, impact until fully seated, remove excess cement 2. **Femoral component** - Apply cement to undersurface, pegs, and intercondylar box, pressurize into all 5 surfaces (distal, anterior, posterior, chamfers), insert and impact component, remove excess cement especially from posterior condyles (blocks flexion if present) 3. **Patellar component** - Apply cement to undersurface, pressurize into patellar bone, insert and hold with clamp, remove excess cement **Maintain reduction** until cement sets (5-7 minutes). Verify no cement posterior to femoral component (use curved curette). Remove all cement from gutters. **Cement Technique**: Modern cement technique with pressurization, pulse lavage, and drying improves interface shear strength by 30-40%. Antibiotic cement reduces infection risk (meta-analysis shows 0.5% reduction in PJI). Cement restrictor not typically used in TKR (unlike THA) because tibial stem short. Cement sets in 5-7 minutes - avoid moving components during polymerization. Excess cement posterior to femur blocks flexion and must be removed. Cement in collateral ligament recesses causes heterotopic ossification and stiffness. Cement on articular surfaces causes third-body wear. Always remove excess cement before polymerization with curette. --- ### Step 15: Insert polyethylene bearing and final assessment Insert polyethylene bearing into tibial tray, reduce joint, perform final checks: - **ROM**: 0-120° minimum (document maximum flexion achieved) - **Stability**: Medial-lateral stability, no anteroposterior translation, no lift-off - **Patellar tracking**: Central tracking through full ROM, perform no-thumb test (should track centrally without manual pressure) - **No impingement**: Flex and extend fully without impingement If persistent lateral patellar maltracking despite correct femoral rotation, consider lateral retinacular release: - Release lateral retinaculum from proximal pole patella to lateral joint line - Use electrocautery to avoid bleeding - Avoid extensive release (increases medial subluxation risk and patellar AVN) Deflate tourniquet, achieve meticulous hemostasis with electrocautery. Close arthrotomy with strong absorbable suture (0 or 1 Vicryl) in figure-of-8 pattern. Close subcutaneous layer with 2-0 Vicryl. Close skin with clips, staples, or subcuticular 3-0 Monocryl. **Dressing**: Wool and crepe bandage, no drain (RCTs show no benefit, increased blood transfusion rate). Some surgeons use intra-articular injection (local anesthetic + morphine + ketorolac + adrenaline) for post-op analgesia. **No-Thumb Test**: Described by Insall - extend knee with patella everted, watch patella reduce as flex to 30-40°. Should track centrally without manual pressure. If laterally subluxes, indicates maltracking - check femoral rotation, patellar component medialisation, tibial component internal rotation, and consider lateral release as last resort. **Vascular injury** (popliteal artery 0.03-0.2%): Immediate recognition critical (absent distal pulses, cold foot, pallor, prolonged capillary refill >3 seconds). Urgent vascular surgery consultation, on-table angiography, exploration and repair (primary repair, interposition graft, or thrombectomy), prophylactic fasciotomies if ischaemia time >4-6h. Limb salvage 80-90% if early recognition, amputation risk 10-20% if delayed. **Common peroneal nerve palsy** (0.5-2%, higher 2-5% in valgus correction): Document deficit immediately post-op, exclude tight dressing (remove bandages), exclude hematoma (ultrasound/MRI, decompress if present), observation (50-70% spontaneous recovery over 3-6 months). EMG/NCS at 3 months if persistent. Tendon transfers if permanent (tibialis posterior to dorsiflexors), AFO for functional support. **Immediate Post-operative Care (0-24 hours)** **Analgesia** - Multimodal approach: - Regional block (femoral nerve block or adductor canal block) - duration 12-24 hours - Oral analgesia: paracetamol 1g QID, oxycodone SR 10-20mg BD + IR 5-10mg q4h PRN - Consider intra-articular injection: local anesthetic + morphine + ketorolac + adrenaline (some surgeons, evidence mixed) - Avoid NSAIDs if using ketorolac, otherwise celecoxib 200mg BD (reduces opioid requirements) - IV patient-controlled analgesia (PCA) if inadequate oral control (rare) **VTE Prophylaxis** - Per Australian guidelines: - Chemical: LMWH (enoxaparin 40mg SC daily) OR DOAC (rivaroxaban 10mg daily, apixaban 2.5mg BD, dabigatran 220mg daily) - Start 12-24h post-op (avoid earlier - bleeding risk) - Duration: 35 days total - Mechanical: TED stockings bilateral, pneumatic compression for 5-7 days, early mobilization **Wound Care**: - Wool and crepe bandage, no drain (RCT evidence shows no benefit, increases transfusion) - Elevate leg on pillows (reduces swelling) - Inspect wound at 48 hours (check for hematoma, excessive drainage) - Cryotherapy (ice packs 20 min q2h for 48h) reduces swelling and pain **Mobilization**: - Day 0 or Day 1: sit out of bed, stand with physiotherapy - Weight-bearing as tolerated (WBAT) with walking frame - Cemented TKR allows immediate full weight-bearing **Drain Controversy**: Large RCT (>1000 patients) showed drains increase blood loss and transfusion rate without reducing hematoma or infection. Most Australian surgeons no longer use drains. If hematoma develops (tense swelling, limited ROM), manage conservatively unless tense (aspiration in sterile theatre if symptomatic). --- **Early Post-operative Phase (1-7 days)** **Physiotherapy** - Twice daily sessions: - Day 1: mobilize with walking frame WBAT, gentle ROM exercises (heel slides, quad sets, ankle pumps) - Day 2-3: progress to crutches or stick, stairs practice, increase ROM exercises - Goal: independent mobility, safe stairs, ROM 0-90° by discharge - CPM (continuous passive motion) NOT beneficial per RCT - no longer used **Criteria for Hospital Discharge** (typically 3-5 days): - Mobilizing safely with walking aid - Can manage stairs if relevant - Adequate pain control on oral analgesia - ROM minimum 0-70° (active extension, passive flexion) - No wound complications (dry, no excessive drainage) - Safe home environment (support, equipment arranged) **Discharge Planning**: - Walking frame or crutches (progress to stick at 2-4 weeks) - Home physiotherapy or outpatient physiotherapy referral - DVT education (leg swelling, calf pain - seek medical attention) - Wound care instructions (keep dry, clips/staples removal at 2 weeks) - Follow-up appointment 2 weeks (wound check) and 6 weeks (surgeon review) Do not discharge if: (1) Unstable mobility (high fall risk), (2) Inadequate pain control, (3) Wound concerns (excessive drainage, cellulitis), (4) Inadequate home support, (5) Medical issues (severe anemia Hb <70, acute confusion, chest infection, DVT/PE). Address issues before discharge or arrange inpatient rehabilitation. --- **Outpatient Rehabilitation Phase (1-12 weeks)** **Physiotherapy Goals**: - Week 1-2: WBAT with walking frame, ROM 0-90°, reduce swelling, wound care - Week 3-6: Progress to stick, ROM 0-110°, quad strengthening, gait re-education - Week 7-12: Independent mobilization, ROM 0-120°, functional exercises (stairs, squats), return to ADLs **ROM Milestones**: - 6 weeks: 0-90° minimum (required for ADLs) - 12 weeks: 0-110° goal (sit comfortably, stairs normally) - 6 months: maximum ROM achieved (average 0-120°, some achieve 130°) **Strengthening Exercises**: - Quadriceps sets, straight leg raises (avoid lag) - Heel slides, wall slides - Mini squats, step-ups - Stationary bike (start week 3-4) - Pool exercises (wait until wound healed >2 weeks) **Return to Activities**: - Driving: 6 weeks minimum (must be able to perform emergency stop, check insurance) - Sedentary work: 6-8 weeks - Active work: 3 months - Low-impact sports: 3-6 months (swimming, cycling, golf, walking) - High-impact sports: NOT recommended (running, tennis, basketball - accelerates wear) **Sports After TKR**: AAOS consensus - recommend low-impact sports (swimming, cycling, golf, doubles tennis, hiking), discourage high-impact (running, basketball, volleyball, skiing). Meta-analysis shows return to sport 80-90% for low-impact, 40-50% for high-impact. High-impact increases revision risk 2-fold. Most Australian surgeons advise against running. --- **Long-term Follow-up and Surveillance** **Clinic Review Schedule**: - 2 weeks: wound check, clips/staples removal, physiotherapy progress - 6 weeks: clinical assessment, ROM measurement, radiographs (AP, lateral, skyline) - 6 months: clinical review, functional assessment - 1 year: clinical review, radiographs (baseline for future comparison) - 2 years: clinical review ± radiographs - 5 years: clinical and radiographic review - Every 5 years lifelong: surveillance (detect asymptomatic loosening early) **Radiographic Assessment**: - AP and lateral weight-bearing views - Assess alignment (mechanical axis should be 0° ± 3°) - Assess component position (femoral flexion, tibial slope, rotation if needed) - Look for lucent lines (>2mm progressive lucency suggests loosening) - Look for osteolysis (focal bone loss suggests particle disease) - Compare to previous radiographs (progressive migration, subsidence, radiolucency) **Patient Education - Lifelong**: - Antibiotic prophylaxis: controversial but most Australian surgeons recommend for dental procedures, invasive procedures (colonoscopy, cystoscopy), any infection (treat promptly) - Seek medical attention for: persistent pain (exclude infection, loosening), swelling, redness, drainage, systemic symptoms (fever) - Avoid excessive weight gain (increases wear and loosening risk) - Low-impact activities only - Metal detectors: TKR may trigger - carry implant card **Expected Outcomes** (AOANJRR 2023 + literature): - Survivorship: 97.4% at 10 years, 94.0% at 15 years, 89.7% at 20 years - Revision rate: 0.5-0.7% per year - Most common causes of revision: infection (26%), aseptic loosening (24%), instability (12%), pain (10%), patellar complications (8%) - Patient satisfaction: 80-85% very satisfied, 10-15% satisfied, 5% dissatisfied - Pain relief: excellent in 75%, good in 20%, poor in 5% - Functional improvement: 80-90% return to desired activities (low-impact) - ROM: average maximum flexion 115-120° (range 90-135°) Patient should seek immediate medical attention for: (1) Acute severe pain (exclude fracture, dislocation, acute infection), (2) Fever + joint pain (exclude infection), (3) Acute leg swelling (exclude DVT), (4) Chest pain/SOB (exclude PE), (5) Wound drainage >3 weeks post-op (exclude infection), (6) Acute loss of ROM (exclude hematoma, infection). Early recognition prevents complications. **AOANJRR 2023 Data - Australian Registry Evidence** **Implant Survivorship**: - Primary TKR: 97.4% at 10 years, 94.0% at 15 years, 89.7% at 20 years - Best survivorship: age 65-75 years (97.8% at 10 years) - Younger patients <55 years: 94.2% at 10 years (higher revision rate due to activity level and longer life expectancy) - Older patients >75 years: 98.1% at 10 years (lower revision rate but higher mortality) **Implant Design - Cruciate Retention**: - Cruciate-retaining (CR): 54% of primary TKR in Australia, 97.3% survivorship at 10 years - Posterior-stabilized (PS): 43% of primary TKR, 97.5% survivorship at 10 years - No significant difference in revision rates (CR vs PS equally successful) - CR advantages: preserves native PCL (better proprioception, rollback), less bone resection, easier revision - PS advantages: more predictable kinematics, corrects flexion contracture, better for PCL-deficient knees (RA, previous trauma) - Choice based on surgeon preference and patient factors (no level 1 evidence favoring either) **Fixation Method**: - Cemented: 97% of TKR in Australia, 97.4% survivorship at 10 years (gold standard) - Uncemented: 2% of TKR, 93.8% survivorship at 10 years (significantly higher revision rate) - Hybrid (cemented tibia, uncemented femur): 1%, 95.2% survivorship at 10 years - AOANJRR conclusion: cement all components in primary TKR (uncemented not recommended) **Patellar Resurfacing**: - Resurfaced: 95% of TKR in Australia, 97.3% survivorship at 10 years - Non-resurfaced: 5% of TKR, 97.1% survivorship at 10 years (no significant difference in revision for aseptic loosening) - However: non-resurfaced has 20-30% anterior knee pain vs 10% with resurfacing - Secondary patellar resurfacing required in 5-8% of non-resurfaced knees - AOANJRR recommendation: routine resurfacing preferred (reduces secondary resurfacing procedures) **Registry vs RCT Evidence**: AOANJRR provides large-scale real-world data (>1 million TKRs) with long-term follow-up, but observational (selection bias). RCTs provide higher quality evidence but smaller numbers and shorter follow-up. For TKR, registry data drives Australian practice - cemented fixation, routine patellar resurfacing, CR and PS both acceptable. --- **Major Controversies in TKR** **1. Alignment Philosophy - Mechanical vs Kinematic** **Mechanical Alignment** (traditional, 95% of Australian surgeons): - Goal: neutral mechanical axis (0° ± 3° HKA angle) - Distal femoral cut perpendicular to mechanical axis (5-7° valgus to anatomic axis) - Proximal tibial cut perpendicular to mechanical axis (0° coronal, 3-7° posterior slope) - Creates rectangular extension and flexion gaps - Long-term evidence: 97.4% survivorship at 10 years (AOANJRR) - Advantages: proven long-term outcomes, equalizes load distribution, straightforward technique - Disadvantages: creates non-anatomic alignment (constitutional varus in 30%), may cause stiffness **Kinematic Alignment** (emerging, <5% of Australian surgeons): - Goal: restore native joint line and limb alignment (match pre-arthritic anatomy) - Distal femoral and proximal tibial cuts match native joint surfaces - May result in constitutional varus or valgus (up to 5-6°) - Requires patient-specific cutting guides or robotic assistance - Short-term RCTs show improved ROM, lower pain, better function vs mechanical alignment - Long-term data lacking (longest follow-up 10 years, small numbers) - Concerns: will varus/valgus alignment increase polyethylene wear and aseptic loosening? - Proponents argue: restores natural kinematics, better soft tissue balance, less releases required - Critics argue: unproven long-term, may increase medial/lateral overload, technically demanding **Current Australian Practice**: Mechanical alignment remains gold standard until long-term kinematic alignment data available. Some surgeons adopt restricted kinematic alignment (allow 0-3° varus/valgus, not >3°). --- **2. Tourniquet Use - To Use or Not to Use** **Pro-Tourniquet** (70% of Australian surgeons): - Reduces blood loss by 200-300mL (multiple RCTs) - Improves visualization (dry field, easier cement technique) - Reduces operative time by 5-10 minutes - Concerns about increased post-op pain and thigh swelling are minor **Anti-Tourniquet** (30% of Australian surgeons): - Increased post-op pain (VAS 1-2 points higher in first 24h) - Increased thigh swelling and stiffness - Theoretical concerns about VTE risk (venous stasis) - Blood loss difference minimal if meticulous hemostasis - No difference in infection or wound complications **Evidence**: Multiple RCTs show no difference in clinical outcomes (infection, ROM, function) at 1-2 years. Cochrane review 2020 concluded: "tourniquet use reduces blood loss and transfusion but increases post-op pain - patient and surgeon preference should guide decision." AOANJRR shows no difference in revision rates with or without tourniquet. **Compromise Approach**: Use tourniquet for bone cuts and cement setting, then deflate and achieve hemostasis before closure (combines benefits of dry field with reduced pain/swelling). --- **3. Cruciate Retention - CR vs PS Design** **Cruciate-Retaining (CR) - 54% of Australian TKR**: - Preserves native PCL (better proprioception in theory) - Less bone resection (no intercondylar box, easier revision) - More "natural" kinematics (femoral rollback) - Requires intact functional PCL (contraindicated if deficient) - May develop PCL wear and synovitis over time **Posterior-Stabilized (PS) - 43% of Australian TKR**: - More predictable kinematics (cam-post mechanism provides rollback) - Corrects flexion contracture more effectively - Better for PCL-deficient knees (RA, previous trauma, ligament laxity) - Increased bone resection (intercondylar box) - Cam-post wear and fracture reported (rare <1%) - Patellar clunk syndrome 1-2% (hypertrophic nodule catches on femoral box) **Evidence**: AOANJRR shows no difference in revision rates (CR 2.6% vs PS 2.5% at 10 years). Multiple RCTs show no difference in ROM, function, or patient satisfaction. Cochrane review 2013: "no clear difference between CR and PS designs." Surgeon preference and patient factors (PCL integrity, deformity, bone quality) should guide choice. **Examiner Perspective**: Know both designs well - describe indications for each. CR preferred if normal PCL and mild deformity. PS preferred if PCL deficient, severe flexion contracture (>15°), inflammatory arthritis (PCL often attenuated), revision (provides more constraint). Either acceptable in primary OA with intact PCL - no "right" answer, defend your choice with evidence. --- **4. Patellar Resurfacing - Always, Never, or Sometimes?** **Always Resurface** (95% of Australian surgeons, AOANJRR recommendation): - Reduces anterior knee pain (10% vs 20-30% in non-resurfaced) - Reduces secondary resurfacing procedures (0.5% vs 5-8%) - Minimal additional operative time (<5 minutes) - Minimal additional cost - RCTs show no difference in function but lower pain with resurfacing - Australian practice: routine resurfacing unless contraindication (patella too thin <20mm, AVN risk) **Selective Resurfacing** (some surgeons, common in Europe): - Resurface if: severe patellar arthritis, inflammatory arthritis, patella alta/baja, patellar maltracking - Do not resurface if: minimal patellar arthritis, young patient, patella thin <20mm - Requires careful assessment and patient selection - Risk: 5-8% require secondary resurfacing (additional surgery) **Never Resurface** (rare, <1% of Australian surgeons): - Avoid patellar complications (fracture, AVN, maltracking) - Denervate patella instead (drill multiple 2mm holes, rim osteophyte excision) - Evidence: RCTs show no difference in function but higher pain scores - Most surgeons abandoned this approach **Evidence**: Cochrane review 2012 analyzed 18 RCTs (>5000 patients): resurfacing reduces anterior knee pain (RR 0.63, 95% CI 0.52-0.77) and secondary resurfacing procedures (RR 0.13, 95% CI 0.08-0.21). No difference in infection, revision, or function. AOANJRR recommendation: routine resurfacing is appropriate. --- **5. Component Fixation - Cemented vs Uncemented** **Cemented** (97% of Australian TKR, gold standard): - Proven long-term outcomes (97.4% survivorship at 10 years) - Immediate fixation (allows early weight-bearing) - Works in all bone quality (including osteoporotic) - Antibiotic-loaded cement reduces infection risk - Disadvantages: cement extrusion, cement debris, revision more difficult **Uncemented** (2% of Australian TKR, not recommended): - Theoretical advantages: bone-implant interface, easier revision, avoid cement debris - Requires good bone quality for osseointegration - AOANJRR data: significantly higher revision rate (6.2% vs 2.6% at 10 years) - Used in some younger patients (<55 years) but evidence lacking - Most Australian surgeons avoid uncemented TKR **Hybrid** (1% of Australian TKR): - Cemented tibia (better fixation in softer tibial bone) - Uncemented femur (harder distal femoral bone) - AOANJRR: higher revision rate than all-cemented (4.8% vs 2.6%) - Not recommended **Evidence**: AOANJRR 2023 shows clear superiority of cemented fixation. No role for uncemented or hybrid in primary TKR in Australia. Cement all components. **Robotic-Assisted TKR** (increasing use, 10-15% of Australian TKR): - Robotic arm-assisted (Mako, ROSA, Navio systems) - Improves component positioning accuracy (alignment within 1-2° of plan vs 3-5° with conventional) - May reduce outliers (malalignment >3°) - Short-term RCTs show no difference in clinical outcomes vs conventional - Long-term data lacking - Significantly increased cost (>$5000 per case) - Learning curve (20-30 cases to proficiency) - Question: will improved accuracy translate to better long-term survivorship? Unknown. **Computer Navigation** (5-10% of Australian TKR): - Improves mechanical axis alignment (reduces outliers >3° from neutral) - Meta-analysis shows reduced malalignment risk but no difference in clinical outcomes - Additional operative time (15-20 minutes) - Pin site complications (infection, fracture) 1-2% - Cost considerations - Most surgeons reserve for complex cases (severe deformity, previous fracture, extra-articular deformity) **Patient-Specific Instrumentation** (PSI) - Declining use: - Pre-operative MRI or CT creates patient-specific cutting guides - Eliminates need for IM/EM guides (avoid IM canal violation, fat embolism risk) - RCTs show no difference in alignment or outcomes vs conventional - Increased cost, planning time, and logistics - Most surgeons abandoned PSI **Highly Cross-linked Polyethylene** (XLPE): - Reduces wear rate by 30-50% vs conventional polyethylene - Proven in THA (reduces osteolysis and aseptic loosening) - In TKR: limited data, concerns about reduced fatigue strength (knee higher contact stress than hip) - May benefit younger, higher-demand patients - Long-term TKR data needed (>10 years) **Custom Off-the-Shelf Implants**: - Wider range of sizes (reduced overhang, better fit) - Gender-specific implants (narrower femoral component for females) - RCTs show no clinical benefit over standard implants - Marketing more than substance **Predictive Analytics and AI**: - Machine learning algorithms predict optimal component size, position, soft tissue balancing - Intra-operative sensors provide real-time feedback on gap balancing, ligament tension - Early stage technology, future potential **Examiner Question on Robotics**: "Does robotic TKR improve outcomes?" Answer: "Short-term RCTs show improved accuracy of component positioning (reduced outliers) but no difference in clinical outcomes (pain, function, ROM) at 1-2 years. Long-term data on survivorship lacking. Significantly increased cost. May reduce revision rate if malalignment is a factor, but mechanical alignment TKR already has 97% survivorship at 10 years, so incremental benefit likely small. Appropriate for complex cases or surgeon preference, but not essential for good outcomes." ## References 1. **Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR)**. Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. Available from: https://aoanjrr.sahmri.com/annual-reports-2023 2. **Insall JN, Binazzi R, Soudry M, Mestriner LA**. Total knee arthroplasty. Clin Orthop Relat Res. 1985;(192):13-22. PMID: 3967412. *Classic description of gap balancing technique and measured resection principles* 3. **Berger RA, Crossett LS, Jacobs JJ, Rubash HE**. Malrotation causing patellofemoral complications after total knee arthroplasty. Clin Orthop Relat Res. 1998;(356):144-153. PMID: 9917679. *Landmark study showing internal rotation femoral component causes 70% of patellar maltracking* 4. **Whiteside LA, Arima J**. The anteroposterior axis for femoral rotational alignment in valgus total knee arthroplasty. Clin Orthop Relat Res. 1995;(321):168-172. PMID: 7497664. *Description of Whiteside's line for femoral rotation* 5. **Krackow KA, Mihalko WM**. The effect of medial release on flexion and extension gaps in cadaveric knees: implications for soft-tissue balancing in total knee arthroplasty. Am J Knee Surg. 1999;12(4):222-228. PMID: 10626913. *Biomechanical study of staged medial releases and gap changes* 6. **Parvizi J, Tan TL, Goswami K, Higuera C, Della Valle C, Chen AF, Shohat N**. The 2018 Definition of Periprosthetic Hip and Knee Infection: An Evidence-Based and Validated Criteria. J Arthroplasty. 2018;33(5):1309-1314. PMID: 29551303. *International consensus criteria for PJI diagnosis (Musculoskeletal Infection Society)* 7. **Abdel MP, Morrey ME, Jensen MR, Morrey BF**. Increased Long-Term Survival of Posterior Cruciate-Retaining Versus Posterior Cruciate-Stabilizing Total Knee Replacements. J Bone Joint Surg Am. 2011;93(22):2072-2078. PMID: 22262378. *Large single-center study comparing CR vs PS designs - no difference in survivorship* 8. **Calliess T, Bauer K, Stukenborg-Colsman C, Windhagen H, Budde S, Ettinger M**. PSI kinematic versus non-PSI mechanical alignment in total knee arthroplasty: a prospective, randomized study. Knee Surg Sports Traumatol Arthrosc. 2017;25(6):1743-1748. PMID: 26685685. *RCT showing kinematic alignment improved ROM and pain vs mechanical alignment at 2 years* 9. **Smith AJ, Elkins MD, Bingham JS, et al**. The Effect of Tourniquet Use on Outcomes in Total Knee Arthroplasty: A Systematic Review and Meta-analysis. J Arthroplasty. 2020;35(7):1981-1990. PMID: 32127254. *Meta-analysis of tourniquet use - reduces blood loss but increases pain, no difference in clinical outcomes* 10. **Australian Orthopaedic Association**. Venous Thromboembolism Prevention in Orthopaedic Surgery - Clinical Practice Guideline. 2020. Available from: https://www.aoa.org.au/education-and-research/clinical-practice-guidelines *Australian national guidelines for VTE prophylaxis - LMWH or DOAC × 35 days recommended*

Primary Total Knee Replacement (TKR)

Primary Total Knee Replacement (TKR)