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, descends through popliteal fossa **At Risk**: Tibial cut (saw penetration posteriorly), posterior releases, posterior cement extrusion **Protection**: Stay anterior with oscillating saw during tibial cut, use retractors for posterior releases, extraperiosteal technique **Location**: Accompanies popliteal artery, slightly more superficial and medial **At Risk**: Same as artery - tibial cut, posterior releases, cement extrusion **Protection**: Same precautions as artery, recognize venous bleeding pattern (darker, continuous flow) **Location**: Winds around fibular neck 2-3cm distal to fibular head, most superficial at this point **At Risk**: Lateral post pressure, valgus correction stress, lateral releases (especially ITB), positioning injuries **Protection**: Pad lateral post carefully, gradual valgus correction (consider staged procedures if >20° deformity), gentle lateral releases staying anterior to fibular head **Location**: Posterior to popliteal vessels in neurovascular bundle, deep in popliteal fossa **At Risk**: Deep posterior releases, tourniquet compression, posterior cement extrusion **Protection**: Stay anterior during tibial cut, extraperiosteal posterior releases, limit tourniquet time <2 hours **Location**: Tibial tubercle insertion, 2-3cm distal to joint line **At Risk**: Arthrotomy extension over tibial tubercle, forceful patellar eversion, tibial preparation **Protection**: Stay ON BONE during arthrotomy at tubercle level, gentle patellar eversion (consider tibial tubercle osteotomy if severe stiffness), protect tubercle during tibial preparation ## Indications ### Absolute Indications - End-stage knee arthritis with bone-on-bone radiographic changes - Failed conservative management (6 months minimum: physio, weight loss, NSAIDs, injections) - Pain limiting activities of daily living (ADLs) - Patient understanding of procedure, realistic expectations, willing to comply with rehab ### Relative Indications - Inflammatory arthritis (RA, psoriatic arthritis) with joint destruction - Post-traumatic arthritis with malunion/nonunion - Osteonecrosis with collapse and secondary arthritis - Neuropathic arthropathy (Charcot knee) - consider higher constraint ### Contraindications **Absolute:** - Active infection (knee, systemic bacteremia) - Insufficient bone stock for fixation (consider stemmed components, bone grafting) - Absent extensor mechanism (consider arthrodesis or megaprosthesis) - Severe peripheral vascular disease (risk limb loss) **Relative:** - Poor skin condition (scarring, ulceration, stasis dermatitis) - Neuropathic joint requiring higher constraint - Morbid obesity (BMI >40) - higher complication rates - Young age (<55 years) - higher revision rates - Active smoking - wound complications 3x higher - Poorly controlled diabetes (HbA1c >8%) - infection risk ## Preoperative Planning ### Clinical Assessment - **History**: Pain pattern, functional limitation, previous treatments, injections - **Examination**: Deformity (varus/valgus), fixed flexion contracture, ROM, ligament stability, extensor mechanism integrity, skin condition, vascular status (pulses), neurological status - **Templating**: Determine component sizes, assess bone quality, plan for defects - **Medical optimization**: Cardiology clearance if indicated, optimize diabetes (HbA1c <8%), smoking cessation, dental clearance, nutritional status (albumin, pre-albumin) ### Radiographic Assessment - **Weight-bearing AP and lateral knee**: Joint space narrowing, osteophytes, subchondral sclerosis/cysts, bone defects - **Long leg alignment (hip-knee-ankle)**: Mechanical axis deviation, constitutional varus/valgus - **Skyline patella**: Patellofemoral arthritis, dysplasia, tilt/subluxation - **Assess**: Deformity magnitude, bone defects requiring grafting, extra-articular deformity, ligament competency ### Implant Selection - **Cruciate retention**: CR (cruciate-retaining) if intact PCL, PS (posterior-stabilized) if deficient PCL or >15° fixed flexion contracture - **Constraint level**: Standard for most primary TKR, semi-constrained if ligament incompetence, hinged for severe instability - **Fixation**: Cemented for most primary TKR (Gold standard), cementless in young active patients (controversial), hybrid (cementless femur, cemented tibia) rarely used - **Patellar resurfacing**: ALWAYS in inflammatory arthritis, significant wear, patellofemoral symptoms; SELECTIVE in others (surgeon preference varies) ### Patient Counseling - **Realistic expectations**: Pain relief 90-95%, improved function but NOT normal knee - **ROM expectations**: Target 0-120°, may not achieve full flexion - **Activity modification**: Avoid high-impact activities (running, jumping sports) - **Longevity**: 90% survival at 15-20 years, may require revision in lifetime - **Complications**: Infection 1-2%, VTE 2-4%, stiffness 5-10%, revision risk 5-10% at 10 years ## Positioning and Setup ### Patient Position - **Supine position** on operating table - **Operative leg free** to flex through full ROM (0-120°) - **Foot of table dropped** OR leg holder device attached to table - **Lateral post at hip level** (prevents leg falling off table during surgery) - **Small bump** under ipsilateral hip (15-20°) for external rotation of leg - **Tourniquet** applied high on thigh (proximal as possible to maximize working space) ### Tourniquet Management - **Inflation pressure**: 300mmHg or LOP (limb occlusion pressure) +100mmHg - **Exsanguination**: Elevate leg 2 minutes OR Esmarch bandage from toes to thigh (avoid if DVT risk) - **Time limit**: Maximum 2 hours (deflate if approaching limit for hemostasis, then re-inflate if needed) - **Deflation**: Before closure to achieve hemostasis, or after closure (surgeon preference) ### Draping - **Leg draped free** including foot (allows full ROM and alignment assessment) - **Waterproof barrier** beneath leg - **Clear drapes** optional (allows visualization of overall leg alignment) ### Equipment Check - **Instrumentation**: Complete TKR set, cutting guides, trials, spacer blocks - **Components**: Correct sizes available based on templating - **Cement**: 3rd generation antibiotic cement (gentamicin typical), mixing system - **Saw**: Oscillating saw with fresh blades - **Retractors**: Hohmann retractors for exposure, laminar spreaders for gap assessment - **Pulsatile lavage** for bone preparation ## Surgical Approach - Medial Parapatellar ### Landmarks and Skin Incision **Palpate and mark landmarks:** - Superior pole of patella - Inferior pole of patella - Tibial tubercle - Joint line (approximately 1cm below inferior pole patella) - Medial epicondyle of femur - Fibular head laterally **Skin incision:** - **Midline longitudinal incision** (CRITICAL for future revision surgery) - **Length**: 12-15cm (adjustable based on exposure needs, body habitus) - **Proximal extent**: 5cm above superior pole of patella - **Distal extent**: 2-3cm below tibial tubercle - **Deepens straight down** to capsule with full-thickness flaps **Rationale for midline:** - Allows flexibility for future revision (can extend proximally/distally) - Can access medial or lateral side through same incision - Preserves blood supply better than parapatellar skin incision - If previous incisions present: ALWAYS use most LATERAL incision (preserves medial blood supply) ### Arthrotomy - Medial Parapatellar **Step-by-step technique:** 1. **Proximal extension into quadriceps** (4-5cm): - Incise quadriceps tendon **2-3mm medial to patella** - Cut **in line with muscle fibers** (parallel to vastus medialis fibers) - Avoid cutting into muscle belly (bleeding, weakness) 2. **Along medial patellar border**: - Continue incision along medial border of patella - **Stay on bone** (protects medial blood supply) - Continue to inferior pole 3. **Patellar tendon and tibial tubercle** (MOST CRITICAL): - At inferior pole, curve slightly medially - Continue **2-3mm medial to patellar tendon** - At tibial tubercle: **STAY DIRECTLY ON BONE** (protects insertion) - Avulsion here is catastrophic complication 4. **Extension around medial tibia**: - Extend arthrotomy posteriorly along proximal medial tibia - Incise deep to MCL fibers - Allows patellar eversion ### Alternative Approaches (Know for Exam) **Subvastus approach:** - Vastus medialis elevated off intermuscular septum, not incised - Preserves quadriceps mechanism integrity - Better for patellar blood supply - Limited exposure in large patients or muscular individuals - Faster recovery, less anterior knee pain **Midvastus approach:** - Split vastus medialis obliquus in line with fibers - Compromise between medial parapatellar and subvastus - Slightly better quadriceps function than medial parapatellar - Still allows good exposure **Lateral parapatellar approach:** - Indicated for severe valgus deformity (>20°), previous lateral incisions - Through vastus lateralis - Allows better access to lateral structures for release - Risk of patellar devascularization higher ## Patellar Eversion and Exposure ### Gentle Patellar Eversion - Evert patella **laterally** with gentle traction (not forcefully) - Flex knee to 90° (facilitates eversion) - Release **medial gutter** to level of fat pad with electrocautery (creates pocket for everted patella) ### If Difficult Eversion - DO NOT FORCE **Options:** 1. **Lateral retinacular release** (CAREFUL - risk patellar devascularization) 2. **Subluxation instead of eversion** (displace laterally without full eversion) 3. **Tibial tubercle osteotomy** for severe stiffness or revision cases 4. **Convert to subvastus approach** if not too far into procedure ### Initial Assessment - Remove loose bodies and debris - Assess PCL integrity (if considering CR design) - Assess menisci and cartilage status - Identify osteophytes for removal ## Systematic Osteophyte Removal **REMOVE ALL OSTEOPHYTES BEFORE BONE CUTS** (affects soft tissue balance) ### Femoral Osteophytes - **Anterior osteophytes**: Rongeur or saw - **Medial/lateral osteophytes**: From condyles and epicondylar regions - **Posterior femoral osteophytes**: Use curved osteotome, careful of popliteal vessels - **Intercondylar osteophytes**: From notch region ### Tibial Osteophytes - **Peripheral osteophytes**: Circumferentially around tibial plateau - **Intercondylar eminence**: If excessive, but preserve PCL insertion if CR design ### Patellar Osteophytes - **Inferior pole**: Common location - **Peripheral**: Around articular margin ### Meniscal and ACL Remnants - Remove meniscal remnants completely - Remove ACL remnant (or preserve if CR design and intact) - PCL: Preserve if CR design, remove if PS design ## Landmark Identification for Rotational Alignment **Critical for femoral component rotation:** ### Transepicondylar Axis (TEA) - GOLD STANDARD - **Medial epicondyle**: Epicondylar sulcus (most prominent point on medial epicondyle, palpable depression) - **Lateral epicondyle**: Lateral epicondylar prominence (most prominent point) - Line connecting these is **Transepicondylar axis** - Most accurate and reproducible reference - Not affected by posterior condylar wear ### Whiteside's Line (AP Axis) - **Proximal point**: Deepest point of trochlear groove (patellar groove) - **Distal point**: Center of intercondylar notch (between spines) - Line connecting these is **Anteroposterior axis of femur** - Femoral component should be perpendicular to this line - Can be affected by trochlear dysplasia ### Posterior Condylar Axis +3° External Rotation - Line connecting most posterior points of medial and lateral condyles - **+3° external rotation** from this line approximates TEA - Can be UNRELIABLE in: - Asymmetric posterior condylar wear (common in valgus knees) - Hypoplastic lateral condyle - Dysplastic condyles **If references are discrepant: PRIORITIZE TEA** ## Proximal Tibial Resection **MOST CRITICAL CUT FOR ALIGNMENT** ### Extramedullary Guide Setup **Distal alignment (ankle):** - Align to **center of ankle** (aim at 2nd ray of foot) - Typically just medial to tibialis anterior tendon - Creates **perpendicular cut to tibial mechanical axis** **Anterior alignment:** - Align to **tibial tubercle** anteriorly - OR medial 1/3 of tubercle in varus knees - Ensures correct anterior-posterior position **Coronal plane:** - Guide should be **perpendicular to mechanical axis** (0° varus/valgus) - Use level or electronic alignment if available - Verify alignment before cutting ### Posterior Slope **Amount of slope:** - **3-7° posterior slope** (match implant design requirements) - CR designs: Usually need MORE slope (5-7°) for rollback - PS designs: Usually need LESS slope (3-5°) as femoral cam provides rollback - Built into cutting guide - set dial appropriately **Verification:** - Check slope angle with guide in place - Adjust if needed before pinning ### Resection Amount **Determine from least worn side:** - Usually **lateral plateau** in varus knees (medial worn) - Usually **medial plateau** in valgus knees (lateral worn) - Measure from least worn side: resect **8-10mm** - This restores joint line appropriately - Mark resection level before cutting ### Cutting Technique **Pin extramedullary guide securely:** - 2-3 pins into tibial metaphysis - Verify alignment and slope before cutting - Recheck distal alignment to ankle after pinning **Oscillating saw technique:** - Begin cut anteriorly, progress posteriorly - **STAY ANTERIOR** (popliteal vessels 10-15mm posterior to posterior cortex) - Cut perpendicular in coronal plane - Maintain posterior slope in sagittal plane - Complete cut with thin saw blade if needed for posterior portion **Verify cut:** - Check perpendicular in coronal plane (0° varus/valgus) - Check posterior slope in sagittal plane (3-7°) - Ensure complete cut, no residual bone bridges ## Distal Femoral Resection ### Intramedullary Guide Setup **Entry point:** - **1cm anterior to PCL insertion** (if PCL still present) - **Center of intercondylar notch** medial-lateral - **In line with femoral canal** (not too anterior or posterior) - Use awl to create entry point through anterior cortex **Insert IM rod:** - Advance into femoral canal - Feel for endosteal contact (ensures central position) - In bowed femur: may need **anterolateral entry point** to avoid anterior cortex perforation ### Valgus Cut Angle **Set guide to 5-7° valgus:** - Compensates for **6° anatomic valgus** of distal femur - Creates cut **perpendicular to femoral mechanical axis** - Standard is 5-6° for most systems - Verify angle before pinning ### Resection Amount **Measure from distal condyles:** - Usually **9-10mm from prominent condyle** (typically lateral in varus knee, medial in valgus knee) - Goal: Equal resection from both condyles (verified after cut) - Adjust if asymmetric wear present - Mark resection level on both condyles ### Cutting Technique **Pin distal femoral cutting guide:** - Verify valgus angle (5-7°) - Verify resection amount both condyles - Pin securely to distal femur (2-3 pins) **Oscillating saw:** - Smooth, controlled cuts - Complete cut through both condyles - **Protect collateral ligament origins** (1cm proximal to joint line) - Remove cut carefully **Verify cut:** - Check both condyles resected equally - Verify valgus angle appropriate - Ensure cut is smooth and flat ## Femoral AP Sizing and Rotation ### AP Sizing **Femoral sizing guide on distal cut:** - Size anteroposterior dimension of femur - Goal: **Avoid anterior overhang OR notching** - **Avoid oversizing**: Causes patellofemoral overstuffing, stiffness - **Avoid undersizing**: Causes flexion instability, posterior impingement **Anterior check:** - Should have **3-5mm bone anterior** to anterior flange - **NO notching** (increases fracture risk 10-fold) **Posterior check:** - Posterior femoral component should cover posterior condyles - Small amount of overhang acceptable (<2mm) - Avoid excessive overhang (impingement) ### Rotational Alignment - CRITICAL **Use all THREE references:** 1. **Transepicondylar axis (TEA)**: Femoral component parallel to this line 2. **Whiteside's line perpendicular**: Femoral component perpendicular to AP axis 3. **Posterior condylar axis +3° ER**: External rotation from posterior condyle line **Set cutting block rotation:** - Align to TEA primarily (most accurate) - Verify agreement with other two references - If discrepant: **PRIORITIZE TEA** - Typical: 3° external rotation from posterior condylar axis **Consequences of malrotation:** **Internal rotation:** - Patellar maltracking (medial tracking) - Anterior knee pain - Medial-side flexion gap tightness - Lateral-side flexion gap looseness **Excessive external rotation:** - Lateral patellar subluxation - Lateral flexion gap tightness - Medial flexion gap looseness ### 4-in-1 Cutting Block **Position block:** - Correct AP size determined above - Correct rotation determined above - Pin securely to distal femoral cut **Block determines:** - Anterior cut (anterior flange position) - Posterior cuts (both condyles) - Anterior chamfer cuts - Posterior chamfer cuts ## Remaining Femoral Cuts ### Anterior Cut **Critical check for notching:** - Should have **3-5mm bone anterior** to cut - If risks notching: Downsize femoral component OR accept slight anterior overhang **Oscillating saw:** - Complete anterior cut - Remove cut block after anterior cut to assess ### Posterior Cuts **Determines flexion gap:** - Equal posterior condyle resection creates rectangular flexion gap - Asymmetric resection creates trapezoidal gap - Cut both posterior condyles - Usually equal thickness both sides (8-10mm) ### Chamfer Cuts **Anterior and posterior chamfers:** - Beveled edges for component seating - Complete all chamfer cuts - Remove cutting block **Verify femoral preparation:** - Trial femoral component on prepared femur - Should sit flush without rocking - No anterior notching - Appropriate rotation (verify with alignment guides) ## Soft Tissue Balancing - Extension Gap ### Extension Gap Assessment **Insert spacer blocks:** - Select thickness based on planned poly (usually 9-10mm) - Insert between distal femur and proximal tibia - Extend knee fully (0°) - Apply varus and valgus stress **Goal: Rectangular extension gap** - Equal medial and lateral space - Tight enough to be stable (minimal opening with stress) - Loose enough to extend fully ### Varus Knee (80% of Primary TKR) **Pathology:** - Medial compartment worn, bone loss medially - Medial structures contracted (MCL, pes, posteromedial capsule) - Lateral structures stretched **Sequential MEDIAL release:** 1. **Deep MCL fibers** from proximal tibia (most effective) 2. **Superficial MCL** - staged release (mid-substance fibers, then full length) 3. **Pes anserinus** tendons (sartorius, gracilis, semitendinosus) 4. **Semimembranosus** tendon 5. **Posteromedial capsule** (CAREFUL - popliteal vessels posterior) **Technique:** - Release from tibial insertion (safer than femoral origin) - Use electrocautery or sharp dissection - Release in **stages** - reassess gap after each release - Use **laminar spreaders** to assess tension - Avoid complete MCL release (causes severe instability) ### Valgus Knee (20% of Primary TKR) **Pathology:** - Lateral compartment worn, bone loss laterally - Lateral structures contracted (LCL, popliteus, lateral capsule, ITB) - Medial structures stretched - Often deficient ACL/PCL **Sequential LATERAL release:** 1. **Lateral capsule and synovium** (release from tibia) 2. **Popliteus tendon** (at femoral or tibial insertion) 3. **Iliotibial band** - posterior fibers (PIE procedure - Proximal ITB, Ellipse lateral capsule) 4. **LCL** - VERY CAREFUL, consider leaving slightly tight vs complete release 5. **Lateral head gastrocnemius** - release origin if needed **Technique:** - Release from tibial side when possible - **VERY CAREFUL with LCL** - complete release causes severe instability - May need **higher constraint** (semi-constrained) if severe - Consider **staged correction** if >20° valgus deformity - Protect **common peroneal nerve** (2-3cm distal to fibular head) ### Fixed Flexion Contracture **Additional releases if contracture persists after gap balancing:** **Posterior capsule release:** - Release posterior capsule from femoral insertion - Excise posterior osteophytes (often major contributor) - Release posterior fibers of collaterals **PCL recession (if CR knee):** - Can "pie crust" PCL (multiple small releases) - Consider converting to PS design if severe **Avoid:** - Excessive posterior tibial slope (increases instability) - Undersizing femoral component (worsens flexion gap balance) ## Soft Tissue Balancing - Flexion Gap ### Flexion Gap Assessment **Flex knee to 90°:** - Insert spacer blocks (same thickness as extension gap) - Apply varus and valgus stress - Assess medial and lateral opening **Goal: EQUAL to extension gap** - Extension gap = Flexion gap = "Balanced knee" - Both gaps rectangular (equal medial/lateral) - Thickness equals planned poly insert ### Flexion Gap TIGHT **Causes:** - Femoral component too large (AP dimension) - Insufficient posterior femoral resection - Tight posterior capsule - Flexed femoral component (excessive posterior slope on distal cut) **Solutions:** 1. **Downsize femoral component** (most common solution) 2. **More posterior femoral resection** (check anterior notching first!) 3. **Posterior capsular release** 4. **Thinner poly insert** (affects both gaps) ### Flexion Gap LOOSE **Causes:** - Femoral component too small (AP dimension) - Excessive posterior femoral resection - PCL deficiency or excessive recession (if CR knee) **Solutions:** 1. **Upsize femoral component** (most common solution) 2. **Thicker poly insert** (affects both gaps) 3. **More constrained implant** (if cannot balance with above) 4. **Augment posterior femoral condyles** (rarely needed in primary) ### PCL Balancing (CR Designs) **PCL tension assessment:** - Should be **snug but not tight** at 90° flexion - Too tight: Limits flexion, increases contact stress - Too loose: Paradoxical anterior slide, instability **Adjust if needed:** - Too tight: Recession (pie crust technique) or convert to PS - Too loose: Thicker poly or convert to PS ### Medial-Lateral Flexion Gap Balance **Assess with knee at 90°:** - Should be equal medial and lateral opening - Slightly more opening than extension gap acceptable **If asymmetric:** - **Medial tight/lateral loose**: Internal rotation of femoral component (revise rotation) - **Lateral tight/medial loose**: Excessive external rotation (revise rotation) - Can also use **collateral releases** but prefer correct rotation first ## Trial Components ### Insert Trial Components **Trial femoral component:** - Correct size and rotation determined above - Should sit flush on all cuts without rocking - No anterior overhang or notching **Trial tibial baseplate:** - Size to cover tibial cut without excessive overhang (<2mm) - Keel or stem aligned with tibial axis - Stable on tibial cut **Trial polyethylene insert:** - Thickness determined from gap balancing - Lock into tibial baseplate - Standard (CR/PS) or higher constraint as needed ### Comprehensive Trial Assessment **1. ALIGNMENT:** - **Mechanical axis check**: Alignment rod from femoral head to center of ankle - Should pass through **center of knee** (or slightly medial) - Correct any malalignment before final implantation **2. STABILITY:** - **Extension (0°)**: Varus/valgus stress - should be stable (minimal opening) - **Mid-flexion (30-60°)**: Stable throughout range - **Flexion (90°)**: Small amount laxity acceptable but no gross instability - **Anterior-posterior**: Drawer test at 90° (CR should be snug, PS stable) **3. RANGE OF MOTION:** - **Extension**: Should achieve 0° (no flexion contracture) - **Flexion**: Target **minimum 120°** (ideally matches or exceeds pre-op) - **Smooth motion** throughout range without catching or impingement **4. PATELLAR TRACKING:** - **"No thumb test"**: Remove thumb pressure, patella should track centrally through full ROM - At 30° flexion: Patella should be centered (not lateral subluxation) - At 90° flexion: Patella should engage trochlea centrally - If maltracking: Check femoral rotation first, lateral release last resort **5. JOINT LINE RESTORATION:** - Measure from medial epicondyle to joint line: should be **within 8mm** of anatomic - Measure from fibular head to joint line laterally - Elevation >8mm: Patella baja, extensor lag, poor function - Lowering: Patella alta, instability (rare) **6. FLEXION-EXTENSION GAP BALANCE:** - Recheck with spacer blocks throughout ROM - Should remain equal and rectangular - No opening >2mm with stress - No tightness limiting motion **7. SOFT TISSUE BALANCE:** - Equal tension medial and lateral - No excessive laxity or tightness - Smooth motion without sudden opening/closing **If any parameter unsatisfactory: REVISE before final implantation** ## Patellar Preparation ### Patellar Resurfacing Decision **ALWAYS resurface if:** - Inflammatory arthritis (RA, psoriatic arthritis, ankylosing spondylitis) - Significant patellar wear or eburnation - Patellofemoral symptoms preoperatively - Patellar maltracking or subluxation - Young active patient expecting high function **Selective resurfacing (surgeon preference):** - Minimal patellar wear - Good tracking - Older, low-demand patient - Patient preference after counseling **Rarely not resurface:** - Very thin patella (<15mm) - resurfacing risks fracture - Severe patellar dysplasia (may not accommodate button) ### Resurfacing Technique **Measure patellar thickness:** - Native thickness: typically **24-26mm** - Measure with caliper - Goal: Restore native thickness (bone + button = 24-26mm) **Patellar resection:** - Use **patellar clamp** to stabilize patella - Resect to leave **12-15mm residual bone** (MINIMUM 12mm) - Cut should be parallel to anterior surface - Avoid over-resection (<12mm increases fracture risk) **Prepare for patellar button:** - Drill holes for **3 pegs** (or central peg depending on design) - Match drill to implant system - Depth stops to avoid perforation through anterior cortex **Trial patellar button:** - Insert trial button - **Median ridge** should align with **trochlear groove** (center of trochlea) - Check rotation: Lateral facet should align with lateral trochlea - Check no overhang or malposition **Check patellofemoral thickness:** - Compare native thickness to resected bone + button thickness - Should be **equal or within 2mm** of native - Overstuffing causes pain, stiffness, reduced ROM - Understuffing rare with proper technique ## Final Component Cementation ### Bone Preparation **Pulsatile lavage:** - Irrigate all bone surfaces with **3L minimum** pulsatile lavage - Removes debris, blood, fat - Better cement penetration **Dry bone surfaces:** - Suction device and dry sponges - Bone should be dry but not desiccated - Some surgeons use **hydrogen peroxide** for hemostasis (controversial - may impair cement penetration) **Final check:** - Remove all debris and soft tissue - Expose cancellous bone - Check sizing one final time ### Cement Mixing **3rd generation antibiotic cement:** - Vacuum mixing system (reduces porosity) - **Gentamicin** typically (40mg per 40g cement powder) - Mix according to manufacturer guidelines (usually 2 minutes) - Mixing in cooled environment prolongs working time **Working time:** - Doughy phase ideal for insertion (not too liquid, not too firm) - Typically 3-5 minutes working time after mixing - Have all components ready before mixing cement ### Cement Application and Component Insertion **Order of insertion:** 1. **Tibial component FIRST** (better cement penetration in supine position with knee flexed) 2. **Femoral component SECOND** 3. **Patellar button THIRD** (if resurfacing) **Tibial component:** - Apply cement to **tibial cut surface** (thin layer) - Apply cement to **underside of tibial baseplate** - **Pressurize cement** into cancellous bone with finger or cement gun - Insert tibial component in correct rotation and alignment - Hold under firm pressure (can use spacer blocks and knee flexion to maintain pressure) **Femoral component:** - Apply cement to **all femoral cut surfaces** (distal, anterior, posterior, chamfers) - Apply cement to **femoral component** - **Pressurize cement** into cancellous bone - Insert in correct rotation (verify rotation marks) - Hold under firm pressure - Flex knee to apply pressure **Patellar button (if resurfacing):** - Apply cement to **patellar cut surface** - Apply cement to **peg holes** - Insert button ensuring correct rotation (median ridge alignment) - Hold under firm pressure (patellar clamp helps) ### Cement Cure **Remove excess cement:** - Remove ALL excess cement immediately (while still soft enough to remove but polymerized enough not to smear) - **Most critical**: Posterior cement (can cause impingement, popliteal vessel compression, wear particles) - Use curettes, rongeurs to remove excess - Check anterior, posterior, medial, lateral gutters **Snap trial poly:** - Protect articulating surfaces during cement cure - Apply pressure to components - Maintain correct alignment **Hold position:** - Maintain pressure on components **8-12 minutes** (cement cure time) - Knee flexed to 20-30° during cure - Remove excess cement as it extrudes **After cement cure:** - Remove trial poly - Check final cement interdigitation - Remove any remaining cement debris - Final irrigation ## Final Polyethylene Insertion **Remove trial poly:** - Carefully unlock from tibial baseplate **Final irrigation:** - **Copious irrigation** with 3L minimum pulsatile lavage - Remove all cement debris and bone fragments - Particulate debris causes third-body wear **Insert final polyethylene:** - Correct thickness from trialing - Lock securely into tibial baseplate - Verify locked (pull test) **Final comprehensive check:** 1. **Full ROM**: 0° extension to 120° flexion minimum 2. **Stability**: Varus/valgus stress at 0° and 90° - stable 3. **Patellar tracking**: Centrally throughout ROM, no thumb test 4. **No impingement**: Deep flexion smooth, no posterior impingement 5. **Leg alignment**: Mechanical axis confirmed through knee center 6. **Smooth motion**: No catching or clicking throughout ROM ## Tourniquet Release and Hemostasis **Release tourniquet:** - After cement cure and final checks - OR after closure (surgeon preference) - Have vasopressors ready (hypotension common) **Achieve meticulous hemostasis:** - Identify bleeding vessels - Electrocautery for hemostasis - Avoid excessive cautery (tissue damage, delayed healing) **Tranexamic acid (TXA):** - Consider **intra-articular injection** 1-3g in 100mL saline - Proven to reduce blood loss by 30-50% - Leave in joint 5 minutes then drain - Contraindications: Previous VTE, coronary stents <1 year, stroke ## Closure ### Capsular Closure - CRITICAL **Medial parapatellar arthrotomy:** - Repair with **interrupted #1 Vicryl** sutures - Critical for extensor mechanism integrity - Ensure strong repair at tibial tubercle (site of avulsion risk) - Tension-free closure (no excessive tightness limiting flexion) **Running closure option:** - Some surgeons prefer running #1 Vicryl - Ensure secure knots proximally and distally **Check patella:** - Reduce patella back into trochlear groove - Should sit centrally without lateral subluxation ### Deep Layer **Subcutaneous closure:** - 2-0 Vicryl to subcutaneous tissues - Minimize dead space - Avoid excessive tension ### Skin Closure **Subcuticular closure:** - 3-0 or 4-0 Monocryl running subcuticular - Better cosmesis than staples - Equal infection rates to staples **Skin glue or Steri-Strips:** - Reinforce closure - Waterproof dressing **Drains (controversial):** - Author does NOT routinely use drains (increased infection risk, no benefit in modern TKR with TXA) - If used: Remove at 24 hours, <400mL output ### Dressing **Sterile dressing:** - Absorptive dressing - Waterproof outer layer - Leave in place 48-72 hours **Compression:** - TED stockings or compression bandage - Reduces swelling **Ice:** - Cryotherapy pads if available - Reduces pain and swelling ## Immediate Post-operative (0-2 weeks) ### Day 0 (Day of Surgery) - **Analgesia**: Multimodal (epidural or adductor canal block, IV/PO opioids, acetaminophen, NSAIDs) - **DVT prophylaxis**: Chemical (aspirin 325mg BID, LMWH, or factor Xa inhibitor per protocol) + mechanical (TED stockings, SCDs) - **Physio**: Ankle pumps, quadriceps sets, straight leg raises (if able) - **Ice/elevation**: Cryotherapy pads, leg elevated - **Wound**: Check dressing, monitor for excessive drainage ### Day 1 - **Mobilization**: Sit edge of bed, stand with walker - **Weight bearing**: WBAT immediately (cemented TKR allows full weight bearing) - **ROM exercises**: Active-assisted ROM with physio, CPM machine if available (controversial) - **Target**: 60° flexion, 0° extension (or pre-op limitation) ### Days 2-7 - **Progressive mobilization**: Walk with walker/frame, increase distance daily - **Stairs**: With assistance and handrail - **ROM**: Target 90° flexion by discharge, maintain full extension - **Discharge criteria**: Adequate pain control on oral meds, safe mobilization with aid, ROM 0-90°, wound dry ### Week 2 - **Wound check**: 10-14 days, remove sutures/staples if used (subcuticular can stay) - **ROM**: Target 90° flexion minimum, working toward 110° - **Mobilization**: Walker or cane, stairs with rail - **Radiographs**: AP, lateral, skyline knee (assess component position, alignment) ## Early Recovery (2-6 weeks) ### Weeks 2-6 - **Physio**: Progressive ROM exercises, strengthening (quad sets, SLR, hip abduction/adduction) - **ROM targets**: 0° extension (mandatory), 110-120° flexion - **Mobilization**: Wean from walker to cane (typically 4-6 weeks) - **Return to driving**: 4-6 weeks RIGHT knee (when off narcotics, adequate quad control for emergency braking), 2-3 weeks LEFT knee ### Week 6 Post-op Visit - **Clinical exam**: ROM (expect 0-110° minimum), wound healed, no effusion, stable to stress - **Radiographs**: Weight-bearing AP, lateral, skyline (baseline for future comparison) - **Activity**: Progress to ADLs, light household duties - **Return to work**: Sedentary work 6-8 weeks, light physical work 8-12 weeks ## Intermediate Recovery (6-12 weeks) ### Weeks 6-12 - **Physio**: Continue strengthening, proprioception exercises, balance training - **ROM target**: 0-120° by 12 weeks (final ROM typically achieved by 3-6 months) - **Activities**: Walking unlimited distance, swimming (wound sealed), stationary bike - **Return to work**: Physical work by 12 weeks (if job allows modification) ### 3 Month Post-op Visit - **Clinical**: ROM should be near maximum (0-120° typical), no pain at rest, minimal pain with activity - **Radiographs**: Not routine unless clinical concern - **Activity clearance**: Low-impact sports (golf, swimming, cycling, doubles tennis), no high-impact ## Long-term (>3 months) ### 6-12 Months - **Maximal improvement**: ROM, strength, function (90% improvement by 6 months, 100% by 12 months) - **Return to activities**: Low-impact unlimited, defer high-impact running/jumping - **Annual follow-up**: Clinical exam, radiographs to screen for loosening ### Lifelong Precautions - **Activity modification**: Avoid high-impact sports (running, jumping, contact sports) - increases wear and loosening risk - **Recommended activities**: Walking, swimming, cycling, golf, doubles tennis, dancing - **Dental prophylaxis**: Controversial. AAOS 2015: NOT routinely recommended for dental procedures. Consider in high-risk (immunosuppressed, previous prosthetic joint infection, inflammatory arthritis, malnourished, diabetes, hemophilia) - **Infection vigilance**: Any infection elsewhere in body should be treated aggressively (UTI, pneumonia, cellulitis) - **Fall prevention**: Most common cause of periprosthetic fracture - **Annual radiographs**: Screen for osteolysis and loosening (can be asymptomatic) ### Expected Outcomes - **Pain relief**: 90-95% achieve significant pain relief - **Satisfaction**: 80-85% satisfied (lower than THA - importance of realistic expectations) - **ROM**: Average 0-120° (depends on pre-op ROM) - **Function**: Significant improvement in walking, stairs, ADLs - **Implant survival**: 90-95% at 10 years, 80-85% at 20 years ## References 1. **Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) Annual Report 2023**. Adelaide: AOA; 2023. Comprehensive Australian registry data on TKR outcomes, survival rates, and revision causes. Reports 95.5% survival at 10 years for primary cemented TKR, with aseptic loosening and infection as leading revision causes. 2. **Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system**. *Clin Orthop Relat Res.* 1989;(248):13-14. Seminal paper establishing the Knee Society Score (KSS) for objective assessment of TKR outcomes. Separates knee score (pain, stability, ROM) from function score (walking, stairs) to distinguish implant performance from patient factors. 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. Describes Whiteside's line (anteroposterior axis from trochlear groove to intercondylar notch) as reference for femoral component rotation. Demonstrates perpendicular alignment to this line produces optimal patellar tracking. 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. Landmark study establishing transepicondylar axis as gold standard for femoral rotation. Shows TEA alignment produces optimal patellar tracking and flexion gap balance, more reliable than posterior condylar axis. 5. **Ritter MA, Davis KE, Meding JB, Pierson JL, Berend ME, Malinzak RA. The effect of alignment and BMI on failure of total knee replacement**. *J Bone Joint Surg Am.* 2011;93(17):1588-1596. Demonstrates mechanical axis alignment within 3° of neutral (HKA 177°±3°) critical for implant longevity. Malalignment >3° varus or valgus significantly increases revision rates and accelerates polyethylene wear. 6. **Hofmann AA, Plaster RL, Murdock LE. Subvastus (Southern) approach for primary total knee arthroplasty**. *Clin Orthop Relat Res.* 1991;(269):70-77. Describes subvastus approach elevating vastus medialis off intermuscular septum without incising quadriceps mechanism. Reports faster recovery, better quadriceps function, less anterior knee pain vs medial parapatellar approach, though limited exposure in muscular/obese patients. 7. **Emerson RH Jr, Head WC, Peters PC Jr. Soft-tissue balance and alignment in medial unicompartmental knee arthroplasty**. *J Bone Joint Surg Br.* 1992;74(6):807-810. Early description of gap balancing technique for soft tissue balancing in knee arthroplasty. Emphasizes equal rectangular extension and flexion gaps as foundation for stable, well-aligned knee. 8. **Lombardi AV Jr, Berend KR, Adams JB. Why knee replacements fail in 2013: patient, surgeon, or implant?**. *Bone Joint J.* 2014;96-B(11 Suppl A):101-104. Contemporary analysis of TKR failure modes. Reports instability (21% of revisions), aseptic loosening (16%), infection (16%), and polyethylene wear (10%) as leading causes, with technical errors (component malposition, malalignment, soft tissue imbalance) contributing to majority. 9. **Australian Orthopaedic Association. Guidelines for VTE Prophylaxis in Total Joint Replacement Surgery** (updated 2022). Australasian evidence-based guidelines. Recommend aspirin 300mg daily as acceptable prophylaxis for standard-risk patients, with LMWH or factor Xa inhibitors for higher-risk patients (previous VTE, thrombophilia, malignancy). Emphasize mechanical prophylaxis and early mobilization. 10. **Ranawat CS, White PB, West S, Ranawat AS. Clinical and radiographic outcomes of attune and PFC sigma knee designs at 2-year follow-up: a prospective matched-pair analysis**. *J Arthroplasty.* 2017;32(2):431-436. Modern comparison of contemporary TKR designs showing 95-98% survival at 2 years with excellent functional outcomes (mean KSS knee score >90, function score >80). Highlights importance of surgical technique and gap balancing over implant design for short-term outcomes.

Primary Total Knee Replacement - Comprehensive Technique

Primary Total Knee Replacement - Comprehensive Technique