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 tibial cortex at joint line **AT RISK**: Proximal tibial cut (posterior saw exit), posteromedial capsular releases, aggressive posterior osteophyte removal **PROTECTION**: ALWAYS use broad posterior retractors (Hohmann or curved Bennett) during tibial cut, stay anterior to posterior cortex, gentle sequential releases staying extraperiosteal **LOCATION**: Accompanies popliteal artery in neurovascular bundle, 10-15mm posterior to tibial cortex **AT RISK**: Same as artery - tibial cut, posterior releases. Venous injury MORE COMMON than arterial **PROTECTION**: Same protection as artery - posterior retractors mandatory, stay anterior, controlled releases **LOCATION**: Winds around fibular neck 2-3cm distal to fibular head laterally **AT RISK**: Lateral post compression, correction of severe valgus (more than 20°), lateral collateral releases, tibial tubercle osteotomy **PROTECTION**: Adequate lateral post padding, gradual valgus correction avoiding acute traction, cautious lateral releases, monitor nerve during correction **LOCATION**: Posterior to popliteal vessels, deep in popliteal fossa **AT RISK**: Well-protected but at risk if saw violates posterior cortex or deep uncontrolled posterior releases **PROTECTION**: Stay anterior during all tibial work, use posterior retractors, controlled extraperiosteal releases **LOCATION**: Inserts on tibial tubercle with broad attachment **AT RISK**: During medial arthrotomy extension distal to tubercle - avulsion is CATASTROPHIC complication **PROTECTION**: Stay DIRECTLY ON BONE when extending arthrotomy past tubercle, score periosteum sharply, NEVER undermine tendon insertion ## Patient Positioning **Supine Position**: Operative leg must be free to flex 120° and extend fully for alignment assessment - Drop foot of table 90° OR use leg positioner - Lateral thigh post at hip level (prevent leg adduction, well-padded for common peroneal nerve protection) - Small bump (towel roll) under ipsilateral hip for 15-20° external rotation - Tourniquet proximal thigh at 300mmHg or LOP + 100mmHg (typically 350-400mmHg) - Prepare and drape leg circumferentially including foot for ROM assessment and alignment checks ## Surgical Approach - Medial Parapatellar **Gold Standard Approach**: Used in 90% of primary TKA cases **Advantages**: - Excellent exposure of femur, tibia, patella - Preserves extensor mechanism integrity - Allows patellar eversion safely - Familiar anatomy and reproducible - Can be extended proximally or distally if needed - Facilitates future revision surgery **Incision Planning**: - Midline longitudinal skin incision 12-15cm length - Centered over patella - Extends from 5cm proximal to superior patellar pole to 2-3cm distal to tibial tubercle - Midline incision preserves blood supply to both medial and lateral skin flaps - Allows conversion to different exposures if needed - CRITICAL for revision surgery access **Positioning Pearl**: Leg must be completely free to move through full ROM for accurate alignment assessment. I use lateral post at hip level to prevent varus sag, and hip external rotation with bump to facilitate patella eversion. Tourniquet at LOP + 100mmHg balances hemostasis with nerve palsy risk. I limit tourniquet time to under 90 minutes. - Tourniquet longer than 2 hours increases nerve palsy and compartment syndrome risk exponentially - Common peroneal nerve compression from lateral post - ensure adequate padding (folded towels or gel pads) - Inadequate external rotation makes patella eversion difficult and risks avulsion - Exsanguination with Esmarch bandage in severe PVD can precipitate critical ischemia - use elevation only ## Systematic Osteophyte Removal **MANDATORY BEFORE ANY BONE CUTS** - Residual osteophytes cause soft tissue imbalance and interfere with cutting guides **Femoral Osteophytes**: 1. Anterior osteophytes from trochlea 2. Medial and lateral femoral condyles (circumferential) 3. Posterior femoral condyles 4. Intercondylar notch **Tibial Osteophytes**: 1. Peripheral osteophytes from medial and lateral plateaus 2. Tibial spines 3. Posterior tibia **Patellar Osteophytes**: - Peripheral rim osteophytes ## Proximal Tibial Cut - FOUNDATION **MOST CRITICAL CUT FOR ALIGNMENT** **Extramedullary Guide Alignment**: 1. **ANKLE**: Center of ankle joint (medial to lateral malleolus midpoint) OR 2nd metatarsal ray 2. **ANTERIOR**: Parallel to tibial tubercle and anterior tibial crest 3. **CORONAL**: Perpendicular to mechanical axis (0° varus/valgus) - verify with alignment rod hip to ankle 4. **SAGITTAL**: Posterior slope 3-7° (CR design 5-7°, PS design 3-5°) **Resection Depth**: 8-10mm from LEAST WORN plateau (usually lateral in varus OA, medial in valgus) **Execution**: - Secure cutting block with pins - Use broad posterior retractors (Hohmann or Bennett) to protect popliteal vessels - Stay ANTERIOR with oscillating saw to avoid neurovascular bundle - Extract bone and inspect surface for perpendicularity and slope **Tibial Cut Pearl**: This cut determines overall limb alignment - it's the foundation of the entire procedure. Extramedullary guide is more accurate than intramedullary in deformed tibiae. I verify coronal alignment with alignment rod from hip center to ankle center passing through knee center. Resecting 8-10mm from least worn plateau preserves bone stock and minimizes joint line elevation. ## Distal Femoral Cut **Intramedullary Guide Technique**: - Entry point 1cm anterior to PCL insertion in center of intercondylar notch - Align with femoral shaft axis (use alignment rod from piriformis fossa) - Drill entry hole with 3/8" drill - Insert IM rod to appropriate depth **Valgus Angle**: 5-7° (compensates for 6° anatomic valgus of distal femur, creates cut perpendicular to femoral mechanical axis) **Resection Depth**: 9-10mm from distal condyle (usually lateral condyle in varus knee) **Goal**: Equal resection from both condyles creates balanced rectangular extension gap ## Femoral Sizing and Rotation - CRITICAL **THREE REFERENCES MUST ALIGN**: 1. **Transepicondylar Axis (TEA)** - GOLD STANDARD - Line from medial epicondylar sulcus to lateral epicondylar prominence - Palpate medial sulcus posterior to MCL origin - Palpate lateral prominence on lateral epicondyle 2. **Whiteside's Line** - Perpendicular to AP axis - From deepest trochlear groove to center of intercondylar notch 3. **Posterior Condylar Axis + 3° External Rotation** - Should align with TEA and Whiteside's line **Priority**: If references conflict (dysplastic condyles, severe wear), PRIORITIZE TEA **Consequences of Malrotation**: - Internal rotation: Patellar maltracking, anterior knee pain, medial flexion gap tightness - Excessive external rotation (more than 5°): Lateral patellar subluxation, lateral flexion gap tightness ## Remaining Femoral Cuts - 4-in-1 Block **Cuts Performed**: 1. Anterior cut - CHECK FOR NOTCHING (must have 3-5mm bone anterior to cut) 2. Posterior condyle cuts - Determines flexion gap 3. Anterior chamfer 4. Posterior chamfer **CRITICAL CHECK**: Anterior femoral notching increases periprosthetic fracture risk 5-10 fold **If Notching Present**: Downsize femoral component or accept slight undercoverage ## Gap Balancing Principles **Goal**: Equal rectangular extension and flexion gaps throughout ROM **Extension Gap**: - Created by distal femoral resection + proximal tibial resection - Balanced by soft tissue releases - Should measure 9-10mm height (polyethylene thickness) - Equal medial-lateral tension **Flexion Gap**: - Created by posterior femoral resection + proximal tibial resection - Balanced by femoral component sizing/rotation + soft tissue releases - Should equal extension gap - Equal medial-lateral tension ## Varus Knee Balancing (80% of Primary TKAs) **Pathology**: Medial structures tight, lateral structures loose **Sequential MEDIAL Releases** (assess with laminar spreaders after each): 1. Deep MCL fibers from tibia (subperiosteal with osteotome) 2. Superficial MCL fibers ('pie-crusting' with 15-blade - multiple small cuts) 3. Pes anserinus tendons from proximal medial tibia 4. Semimembranosus from posteromedial corner 5. Posteromedial capsule **NEVER** completely release MCL - causes severe instability requiring constrained implant ## Valgus Knee Balancing (20% of Primary TKAs) **Pathology**: Lateral structures tight, medial structures loose **Sequential LATERAL Releases** (assess after each): 1. Lateral capsule and synovium 2. Popliteus tendon at femoral origin 3. Iliotibial band posterior fibers 4. Lateral head gastrocnemius 5. LCL - VERY CAUTIOUS, avoid complete release **LCL Release**: Last resort, complete release causes severe instability ## PCL Management (CR Designs) **Tension Assessment**: PCL should be SNUG but not TIGHT at 90° flexion **Too Tight**: - Limits flexion - Causes paradoxical anterior slide - Management: Release superficial PCL fibers or pie-crust PCL **Too Loose**: - Posterior sag - Flexion instability - Management: Consider thicker poly or PS design **Gap Balancing Pearl**: Extension and flexion gaps must be equal in height AND rectangular (equal medial-lateral tension) throughout ROM. For varus knee, I perform sequential medial releases with incremental assessment using laminar spreaders. Goal is balanced tension, not complete release. Overcorrection requiring constrained implant is a technical failure. ## Comprehensive Trial Assessment **SYSTEMATIC CHECKS BEFORE CEMENTING**: 1. **ALIGNMENT**: - Alignment rod from femoral head center to ankle center passes through knee center - Mechanical axis HKA 180° ± 3° (177-183°) 2. **STABILITY**: - Varus/valgus stress at 0° extension: less than 3mm opening - Varus/valgus stress at 90° flexion: less than 5mm opening (minimal physiologic laxity acceptable) 3. **ROM**: - 0° full extension (no flexion contracture) - MINIMUM 120° flexion (functional ROM) 4. **PATELLAR TRACKING**: - 'No thumb test' - patella tracks centrally WITHOUT manual pressure - No lateral subluxation or tilt throughout ROM 5. **JOINT LINE**: - Measure from inferior patellar pole to tibial cut: should be 10mm - Restore anatomic joint line within 8mm 6. **GAP BALANCE**: Reconfirm equal rectangular gaps 7. **NO IMPINGEMENT**: Deep flexion without posterior impingement ## Patellar Resurfacing **ALWAYS Resurface If**: - Inflammatory arthritis (RA, psoriatic arthritis) - Significant patellar wear with eburnation - Patellofemoral symptoms preoperatively - Patellar maltracking - Young active patient **Resurfacing Technique**: 1. Measure native patellar thickness with caliper (normal 24-26mm) 2. Apply patellar clamp or use freehand technique 3. Resect to leave MINIMUM 12-15mm residual thickness 4. Prepare patellar bone surface for component 5. Ensure median ridge aligns with trochlear groove 6. Check overall patellofemoral joint thickness equals or less than native 7. Cement with pressurization **Critical Thickness**: ABSOLUTE MINIMUM 12mm residual, less than 10mm significantly increases fracture risk ## Final Component Cementation **Bone Preparation**: - Pulsatile lavage with 3L minimum normal saline - Suction dry - Pack with sponges soaked in hydrogen peroxide or dilute adrenaline for hemostasis - Dry again thoroughly **Cement**: 3rd generation antibiotic-loaded bone cement (gentamicin or tobramycin) **CEMENTATION SEQUENCE**: 1. **TIBIA FIRST** (better cement penetration with gravity) - Apply cement to tibial cut and component undersurface - Pressurize into cancellous bone - Insert tibial baseplate in correct rotation - Hold with pressure 2. **FEMUR** (while tibial cement curing) - Apply cement to all femoral cut surfaces and component - Pressurize cement - Insert femoral component in correct rotation (verify TEA alignment) - Hold with pressure 3. **PATELLA** (while femoral cement curing) - Cement and insert - Hold with clamp **CRITICAL**: Remove ALL excess cement BEFORE curing, especially POSTERIORLY **Cement Cure**: Hold components under pressure until cement fully cured (8-12 minutes) ## Final Polyethylene and Closure **After Cement Cured**: - Remove trial polyethylene - Irrigate joint copiously with 3-6L normal saline (remove cement debris, bone fragments) - Insert FINAL polyethylene insert (locks with definitive click) **FINAL COMPREHENSIVE CHECKS**: 1. Full ROM 0-120° without restriction 2. Stable varus/valgus stress at 0° and 90° 3. Patella tracks centrally through ROM 4. No posterior impingement in deep flexion 5. Alignment rod confirms neutral mechanical axis **Tourniquet Release**: Achieve meticulous hemostasis with bipolar **CLOSURE**: - Repair medial parapatellar arthrotomy with interrupted figure-of-8 or simple interrupted #1 Vicryl - Ensure watertight closure (critical for extensor mechanism) - Close deep fascia with running 2-0 Vicryl - Subcuticular skin closure with running 3-0 Monocryl - Sterile dressing, compression dressing, TED stockings **Cementation Pearl**: Meticulous cement technique is critical for long-term fixation and survivorship. I cement tibia first for better penetration with gravity, pressurize cement into cancellous bone for mechanical interlock, and remove ALL excess cement before curing. Posterior cement extrusion can compress popliteal vessels or cause impingement. ## Immediate Postoperative (Day 0-1) **DVT Prophylaxis**: - LMWH (enoxaparin 40mg daily) OR - Factor Xa inhibitor (rivaroxaban 10mg daily) OR - Aspirin 325mg BID (per AAOS guidelines) - Duration: 6 weeks minimum - TED stockings and intermittent pneumatic compression **Analgesia**: - Multimodal approach: acetaminophen, NSAIDs, opioids as needed - Consider nerve block or periarticular injection - Ice and elevation **Early Mobilization**: - Active ROM exercises - Ankle pumps - Quadriceps sets - Straight leg raises - CPM machine optional **Weight Bearing**: IMMEDIATE WBAT (weight bearing as tolerated) with cemented TKA and intact extensor mechanism ## Week 1-2 **Physiotherapy Goals**: - 90° flexion by 2 weeks - 0° full extension by 2 weeks - Stair climbing with rail - Transition from walker to cane **Week 2**: Wound check, remove sutures if non-absorbable ## Week 2-6 **ROM Goals**: - Target 120° flexion by 6 weeks - Maintain 0° extension - Quadriceps strengthening critical **Week 6 Assessment**: - Clinical evaluation - Baseline radiographs (AP, lateral, skyline) - Clear for driving if right knee (must be off narcotics, adequate quadriceps control) - Return to sedentary work ## Month 3-12 **Month 3**: - ROM should plateau at 120° flexion, 0° extension (90% achieve this) - Return to low-impact activities (swimming, cycling, golf, walking) **Month 6-12**: - Return to higher-impact activities as tolerated (hiking, doubles tennis) - AVOID high-impact running and jumping ## Long-Term Follow-Up **Schedule**: - 2 weeks (wound check) - 6 weeks - 3 months - 1 year - Then ANNUALLY for life **Annual Radiographs**: Monitor for loosening (progressive radiolucent lines more than 2mm concerning) ## References 1. Insall JN, Binazzi R, Soudry M, Mestriner LA. Total knee arthroplasty. Clin Orthop Relat Res. 1985;(192):13-22. PMID: 3967412. [Foundational work on total knee arthroplasty technique and alignment principles] 2. 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. [Critical study establishing importance of femoral component rotation for patellar tracking] 3. 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. [Described Whiteside's line as reference for femoral rotation] 4. Berger RA, Rubash HE, Seel MJ, Thompson WH, Crossett LS. Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis. Clin Orthop Relat Res. 1993;(286):40-47. PMID: 8425366. [Established transepicondylar axis as gold standard for femoral rotation] 5. Ranawat CS, White PB, West S, Ranawat AS. Clinical and radiographic results of attune and PFC sigma knee designs at 2-year follow-up: a prospective matched-pair analysis. J Arthroplasty. 2017;32(2):431-436. PMID: 27665240. [Modern outcomes data for primary TKA with measured resection technique] 6. Fehring TK, Odum S, Griffin WL, Mason JB, Nadaud M. Early failures in total knee arthroplasty. Clin Orthop Relat Res. 2001;(392):315-318. PMID: 11716402. [Analysis of early complications including instability, stiffness, and infection] 7. Mihalko WM, Whiteside LA, Krackow KA. Comparison of ligament-balancing techniques during total knee arthroplasty. J Bone Joint Surg Am. 2003;85-A Suppl 4:132-135. PMID: 14652403. [Comparison of gap balancing versus measured resection techniques] 8. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. [Australian-specific registry data on TKA outcomes, revision rates, and implant survivorship] 9. Therapeutic Guidelines Ltd. eTG Complete [digital]. Melbourne: Therapeutic Guidelines Limited; 2023. [Australian antibiotic prophylaxis and VTE prevention guidelines for arthroplasty] 10. Dennis DA, Komistek RD, Colwell CE Jr, et al. In vivo anteroposterior femorotibial translation of total knee arthroplasty: a multicenter analysis. Clin Orthop Relat Res. 1998;(356):47-57. PMID: 9917666. [Kinematic analysis demonstrating importance of gap balancing for proper knee function]

Primary Total Knee Arthroplasty - Standard Measured Resection Technique

Primary Total Knee Arthroplasty - Standard Measured Resection Technique