High Yield Overview

TOTAL KNEE ARTHROPLASTY - MEDIAL PARAPATELLAR APPROACH

Medial parapatellar arthrotomy (gold standard approach) | advanced

Critical Danger Structures

Popliteal Artery

Location: 10-15mm posterior to posterior capsule at joint line, closely adherent to bone in popliteal fossa, most at risk during posterior osteophyte removal

Protection: Avoid hyperextension greater than 10° during exposure, use curved osteotomes for posterior osteophyte removal, gentle posterior retraction with Hohmann retractors placed on bone, avoid excessive posterior condylar resection

Common Peroneal Nerve

Location: Wraps around fibular neck 20-30mm distal to fibular head laterally, tethered at fibular tunnel making it vulnerable to stretch injury during valgus correction

Protection: Minimize valgus correction force (limit to 15° correction acutely), graduated lateral releases rather than complete LCL release, warn patient preoperatively of neuropraxia risk (2-5% in severe valgus), consider staged correction if deformity greater than 20°

Saphenous Nerve and Infrapatellar Branch

Location: Main nerve crosses medial incision at joint line level, infrapatellar branch travels anteriorly across surgical field to supply skin over anterior knee and patellar tendon

Protection: Accept numbness as expected outcome (occurs in 30-50% patients), counsel preoperatively, avoid sharp transection (crush or cauterize nerve branches instead to prevent neuroma formation), vertical midline incision reduces branch injury compared to medial approaches

Medial Collateral Ligament

Location: Superficial MCL fibers insert 50mm below joint line on medial tibial metaphysis, deep MCL fibers insert directly on tibial plateau medial edge, both must be preserved or released in controlled fashion

Protection: Sequential graduated release starting with deep MCL (meniscotibial ligament) before superficial MCL, subperiosteal elevation technique preserves fiber continuity, never release superficial MCL insertion distally (causes valgus instability), release proximal fibers from medial epicondyle if needed for severe varus

Patellar Blood Supply (Lateral Genicular Arteries)

Location: Lateral superior and inferior genicular arteries form anastomosis supplying patella from lateral side, vulnerable to devascularization if arthrotomy too lateral or excessive lateral release

Protection: Arthrotomy incision 5mm medial to patella border preserves lateral blood supply, limit lateral retinacular release to minimum needed for eversion (avoid extensive 'pie-crusting'), maintain superior and inferior attachments, consider leaving patella unresurfaced if blood supply compromised

Mnemonic

ROTATIONROTATION - Femoral Component Rotational Landmarks

Mnemonic

BALANCEDBALANCED - Gap Balancing Technique in TKA

Indications

Primary Indications

Primary osteoarthritis - Most common indication (85% of TKAs), tricompartmental disease with pain and functional limitation despite conservative management
Inflammatory arthritis - Rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis with severe joint destruction
Post-traumatic arthritis - Following tibial plateau fracture, distal femur fracture, or patellar fracture with malunion/articular incongruity
Avascular necrosis - Multifocal or involving multiple compartments (medial and lateral femoral condyles)
Failed osteotomy - Progressive arthritis after high tibial osteotomy or distal femoral osteotomy

Secondary Indications

Failed unicompartmental knee arthroplasty - Progression to multicompartmental disease or component failure
Septic arthritis sequelae - Severe cartilage destruction after eradicated infection (two-stage approach if active)
Hemophilic arthropathy - Chronic hemarthrosis leading to joint destruction
Neuropathic arthropathy - Charcot joint with preserved sensation (controversial - higher failure rate)

Contraindications

Absolute Contraindications

Active infection - Local or systemic infection, requires two-stage revision if knee infected
Extensor mechanism dysfunction - Absent quadriceps function, prior quadriceps or patellar tendon rupture without successful repair
Neurovascular compromise - Severe peripheral vascular disease with ischemic leg, absent pulses (requires vascular surgery first)
Neuropathic joint with absent sensation - Charcot arthropathy with complete sensory loss (unacceptably high failure rate)

Relative Contraindications

Young active patient - Age less than 60 years with high activity demands (consider osteotomy or activity modification first)
Severe bone loss - May require metaphyseal augments, stems, or hinged prosthesis rather than standard TKA
Morbid obesity - BMI greater than 40 increases infection, wound complications, mechanical failure (optimize weight first)
Active smoking - Increases wound complications and infection (cessation 6 weeks preoperatively recommended)
Poor soft tissue envelope - Prior incisions, skin grafts, thin skin increases wound complications
Reflex sympathetic dystrophy/CRPS - Chronic pain syndrome predicts poor outcomes

Australian Epidemiology

According to AOANJRR 2023 Annual Report:

71,245 primary TKAs performed in Australia annually
93% survivorship at 15 years for cemented cruciate-retaining TKA
Cumulative revision rate 8.0% at 15 years (lower than hip - 8.7%)
Primary osteoarthritis accounts for 97% of primary TKAs
Mean age 69 years (range 40-90 years, increasing numbers younger than 60)

Step-by-Step Technique

Step 1: Position Supine, Apply and Inflate Thigh Tourniquet After Exsanguination

Position supine on standard table with foot support allowing knee flexion greater than 120°. Apply sterile thigh tourniquet. Exsanguinate limb with Esmarch bandage or elevation for 2 minutes. Inflate tourniquet to 100mmHg above systolic pressure (minimum 250mmHg, typically 300mmHg).

Exam Pearl

Technical Tip: Tourniquet pressure affects postoperative pain and complications - use lowest effective pressure (less than 350mmHg if possible), limit time to less than 90 minutes. Consider modern bloodless techniques (no tourniquet) which reduce pain and improve early ROM but increase operative time and blood loss. Release before closure for hemostasis identification.

Dangers at this step

Tourniquet-related complications: skin injury, nerve palsy (peroneal nerve most vulnerable), thromboembolic events
Compartment syndrome if tourniquet time exceeds 2 hours

Step 2: Mark Anatomical Landmarks and Midline Skin Incision

Mark patella borders (superior, inferior, medial, lateral edges), tibial tubercle, and joint line. Draw midline longitudinal incision from 5-6cm above superior pole of patella to 2cm below tibial tubercle (total length 12-15cm). Make sharp incision through skin and subcutaneous tissue to deep fascia, identifying and preserving prepatellar bursa plane.

Exam Pearl

Technical Tip: Midline vertical incision preserves medial and lateral blood supply to skin - reduces wound complications compared to medial or lateral parapatellar skin incisions. Critical principle in revision surgery where multiple incisions may exist (always use most lateral existing incision or create new midline if incisions more than 6cm apart).

Dangers at this step

Skin necrosis from excessive tension or undermining (keep skin flaps thick with subcutaneous fat)
Damage to prepatellar bursa causing persistent effusion
Injury to infrapatellar branch of saphenous nerve (unavoidable - counsel patient about numbness)

Step 3: Medial Parapatellar Arthrotomy: Quadriceps, Patella, Medial Plateau

Incise quadriceps tendon 5mm medial to midline starting 5cm proximal to patella. Continue distally along medial border of patella staying 5mm medial to edge, incorporating medial retinaculum. Curve distally at inferior pole to anteromedial tibial plateau, ending 5mm medial to tibial tubercle at level of joint line.

Exam Pearl

Technical Tip: Stay 5mm medial to patella edge (not directly on edge) to avoid patellar devascularization - patella blood supply derives from lateral superior and inferior genicular arteries forming extraosseous ring, with medial contributions minimal. Lateral blood supply must be preserved or risk patellar AVN and fracture.

Dangers at this step

Patellar devascularization if arthrotomy too lateral or aggressive lateral release performed
Damage to patellar tendon if incision extends too far distally or medially onto tendon substance

Step 4: Release Medial Soft Tissues Subperiosteally, Evert Patella Laterally

Perform subperiosteal elevation of medial meniscus, capsule, and deep MCL from proximal tibia using electrocautery or sharp dissection. Release fat pad (Hoffa's fat pad) from inferior pole of patella and anterior tibia. Evert patella laterally using gentle traction with Z-retractor or hand, displacing it onto lateral femoral condyle.

Exam Pearl

Technical Tip: If patella will not evert easily (resistance felt), STOP immediately and perform lateral retinacular release or extend arthrotomy into vastus lateralis - forced eversion causes patellar tendon avulsion from tibial tubercle or patellar fracture (catastrophic complications requiring immediate repair/reconstruction).

Dangers at this step

Patellar tendon avulsion from tibial tubercle (requires immediate repair with suture anchors or bone tunnels)
Patellar fracture (requires tension band wiring or fragment excision)

Step 5: Release Lateral Retinaculum if Patella Does Not Evert Easily

If patella resists eversion, extend arthrotomy proximally into vastus lateralis oblique fibers (creating inverted V) OR release lateral retinaculum from lateral patellar edge using electrocautery staying on bone. Release only minimum needed for safe eversion (typically 2-3cm). Avoid excessive release causing lateral patellar subluxation.

Exam Pearl

Technical Tip: Lateral release is direct extension of arthrotomy (open technique under direct vision), NOT separate percutaneous 'pie-crusting' procedure - pie-crusting causes hematoma formation, cannot control depth, and risks lateral genicular artery injury. Modern trend: minimize lateral release (needed in less than 10% primary TKAs with good femoral rotation).

Dangers at this step

Lateral superior genicular artery injury causing hematoma (requires ligation)
Excessive release causing lateral patellar instability (requires medial imbrication at closure)

Step 6: Remove Anterior Cruciate Ligament, Expose Tibial Plateau and Distal Femur

Excise ACL from femoral origin (lateral wall of intercondylar notch) and tibial insertion using curved scissors or electrocautery. Remove anterior horns of medial and lateral menisci. Clear soft tissue from anterior tibia and distal femur using periosteal elevator and electrocautery. Remove peripheral osteophytes from medial and lateral femoral condyles, medial and lateral tibial plateaus, and intercondylar region using osteotomes and rongeur.

Exam Pearl

Technical Tip: Peripheral osteophyte removal BEFORE bone cuts - creates space for saw blade oscillation preventing soft tissue injury, and prevents soft tissue impingement giving false sense of balance (soft tissue balancing should reflect true ligament tension, not osteophyte impingement). Medial and lateral gutters must be completely cleared.

Dangers at this step

MCL injury during medial osteophyte removal (stay on bone, subperiosteal technique)
Popliteal artery injury during posterior osteophyte removal (use curved osteotomes, avoid excessive force)

Step 7: Perform Tibial Cut: Perpendicular to Mechanical Axis, 3-7° Posterior Slope

Apply extramedullary or intramedullary tibial cutting guide aligned with mechanical axis (center of ankle to center of knee). Adjust varus-valgus to 0° (perpendicular to mechanical axis). Set posterior slope to 3-7° (typically 5°, match native slope). Set resection depth to 8-10mm from lateral plateau (least worn side) or per preoperative templating. Make tibial cut with oscillating saw ensuring complete cut without soft tissue interposition.

Exam Pearl

Technical Tip: Tibial slope is critical for knee biomechanics - excessive slope (greater than 7°) causes PCL impingement and flexion instability in CR knees, allows cam to slide off post in PS knees. Insufficient slope (less than 3°) causes hyperextension limitation and posterior cam-post impingement in PS knees. Native slope averages 7° (range 0-13°) - match within 2° for optimal kinematics.

Dangers at this step

Excessive resection causing bone loss and requiring thicker polyethylene (increases constraint and wear)
Popliteal artery injury during posterior cut completion (oscillate saw, do not plunge)

Step 8: Distal Femoral Cut: 5-7° Valgus from Anatomic Axis (Perpendicular to Mechanical Axis)

Insert intramedullary guide rod into femoral canal via entry point at intercondylar notch anterior to PCL insertion. Apply distal femoral cutting guide set at 5-7° valgus from femoral anatomic axis (typically 6°) to achieve perpendicular cut to mechanical axis. Set resection depth to 9-10mm from most worn condyle (measure both condyles, usually symmetric). Make distal femoral cut with oscillating saw.

Exam Pearl

Technical Tip: Valgus cut angle restores neutral mechanical alignment - femoral anatomic axis is 5-7° valgus to mechanical axis due to femoral shaft angulation. Excessive valgus cut (greater than 8°) causes medial laxity and varus instability. Insufficient valgus (less than 4°) causes residual varus alignment and medial overload. Adjust based on preoperative mechanical axis (more valgus in native valgus knee).

Dangers at this step

Fat embolism syndrome from femoral canal reaming (rare with modern small-diameter rods)
Femoral fracture if osteoporotic bone or aggressive reaming

Step 9: Assess Extension Gap and Perform Medial/Lateral Releases to Balance

Insert spacer blocks (typically 10mm thickness) between tibial and femoral cuts with knee in full extension. Apply varus and valgus stress assessing medial and lateral tightness. Goal: symmetric 1-2mm laxity medially and laterally (rectangular gap). For varus deformity with medial tightness: sequential medial release (deep MCL/meniscotibial ligament → posterior capsule → superficial MCL proximal fibers → pes anserinus). For valgus deformity with lateral tightness: sequential lateral release (ITB → lateral capsule → popliteus → LCL → lateral head gastrocnemius).

Exam Pearl

Technical Tip: Varus deformity balancing easier than valgus (medial structures more forgiving) - release deep MCL first (subperiosteal from tibia), then posterior capsule, finally superficial MCL if needed. Valgus deformity balancing difficult and risky - extensive lateral release including LCL required for severe deformity, warn patient preoperatively of common peroneal nerve palsy risk (2-5% with deformity greater than 15° valgus). Consider constrained implants if severe.

Dangers at this step

Common peroneal nerve palsy from stretch injury during valgus correction (minimize acute correction, staged procedures if severe)
Vascular injury during posterior capsule release (popliteal artery adherent to posterior capsule)

Step 10: Size Femoral Component and Determine Rotation Using Three Landmarks

Measure anteroposterior dimension of distal femur using femoral sizing guide (anterior and posterior references). Select appropriate size avoiding notching anteriorly or overhang posteriorly (downsize if between sizes). Determine rotation using THREE landmarks: (1) Whiteside's line (anteroposterior axis from deepest trochlear groove to intercondylar notch), (2) Transepicondylar axis (line connecting medial and lateral epicondyles), (3) 3° external rotation from posterior condylar axis. Mark all three - should agree within 2°. If conflict, use combination (typically 3° external to posterior condyles, confirming parallel to Whiteside's line).

Exam Pearl

Technical Tip: Femoral rotation CRITICAL for patellar tracking and flexion gap balance - internal rotation causes patellar maltracking, lateral patellar pain, flexion instability, and is leading cause of TKA revision for pain. 3° external rotation to posterior condyles most reliable single landmark (posterior condyles easy to identify), confirmed by Whiteside's line (should be parallel). Transepicondylar axis most anatomic but difficult to palpate reliably. ALWAYS mark all three and use combination.

Dangers at this step

Internal rotation malrotation (causes patellar maltracking, flexion instability, chronic pain requiring revision)
Excessive external rotation (causes medial flexion laxity and instability)

Step 11: Make Anterior, Posterior, and Chamfer Femoral Cuts

Apply 4-in-1 cutting block to distal femur at determined size and rotation (secure with two pins into bone). Verify rotation alignment visually (Whiteside's line and transepicondylar axis). Make anterior cut first, then posterior cuts (medial and lateral condyles), then anterior and posterior chamfer cuts using oscillating saw. Remove cutting guide and bone fragments. Check cuts for completeness and accuracy.

Exam Pearl

Technical Tip: Posterior condylar cut defines flexion gap size - excessive resection opens flexion gap causing flexion instability, insufficient resection creates flexion tightness limiting range of motion. If posterior condyles worn asymmetrically (common in varus knees - medial condyle more worn), consider asymmetric resection to balance flexion gap, OR use posterior referencing system (resects equal amounts from both condyles, accepts flexion-extension gap mismatch, adjusts with insert thickness).

Dangers at this step

Incomplete cuts causing component malseating (rock on bone bridge)
Saw blade plunge injury to posterior capsule and popliteal vessels

Step 12: Assess Flexion Gap with Spacer Blocks, Confirm Symmetric Balance

Insert 10mm spacer blocks between tibial cut and femoral condyles with knee at 90° flexion. Apply varus and valgus stress checking medial and lateral gaps - should be equal (symmetric) and allow 1-2mm laxity (rectangular gap). Compare to extension gap (should be equal in size - both 10mm). If gaps unequal: flexion gap tighter than extension gap (downsize femoral component OR resect more posterior condyle OR release posterior capsule), extension gap tighter than flexion gap (resect more distal femur OR perform additional soft tissue release OR upsize insert).

Exam Pearl

Technical Tip: Flexion and extension gaps MUST be equal and rectangular (symmetric medial-lateral, equal size) - this is fundamental principle of gap balancing technique. Unequal gaps cause instability in one position (flexion or extension). Non-rectangular gaps (trapezoid) cause asymmetric loading and polyethylene wear. GOAL: 10mm ± 1mm equal and rectangular gaps in both flexion and extension.

Dangers at this step

Instability from overstuffing or understuffing joint (incorrect gap size or asymmetry)
Stiffness from excessive bone resection requiring thick inserts (increases constraint)

Step 13: Decide PCL Management: Retain (CR) or Sacrifice (PS)

Assess PCL integrity, quality, and tension. If PCL intact, functional, and provides appropriate tension in flexion: retain (cruciate-retaining design). If PCL deficient, worn, arthritic, or excessively tight: sacrifice (posterior-stabilized design). For PS: excise PCL from femoral origin and tibial insertion using sharp dissection. Prepare intercondylar notch by removing bone and soft tissue for cam-post mechanism (use sagittal saw for box cut). For CR: preserve PCL, balance tension with tibial slope (more slope relaxes PCL).

Exam Pearl

Technical Tip: CR vs PS debate remains controversial - AOANJRR shows equivalent outcomes at 15 years (8% revision rate both, no significant difference in survival). Choose based on PCL quality: deficient/worn/arthritic/tight → PS (provides intrinsic stability). Intact/functional/normal tension → CR (preserves native kinematics, more bone stock preservation, no cam-post wear). Both require different femoral components (NOT interchangeable) - must decide before femoral cuts.

Dangers at this step

PCL avulsion during retention attempt causing flexion instability (requires conversion to PS if recognized)
Incomplete PCL excision in PS causing impingement and limited flexion

Step 14: Prepare Patella: Resect to Uniform Thickness or Measured Resection

Measure patellar thickness at thickest point using caliper (record native thickness). Determine resection amount: goal to restore native thickness with composite (bone + button). Typically resect cartilage and bone leaving 12-15mm bone remaining. Use free-hand saw (cutting medial and lateral facets equally) OR patellar cutting guide (ensures uniform thickness). Prepare three peg holes for patellar button using drill or punch per implant specifications. Measure final bone thickness - should allow composite to equal native ± 2mm.

Exam Pearl

Technical Tip: Patellar thickness critical for patellofemoral mechanics - final composite thickness (remaining bone + patellar button) should equal native patellar thickness ± 2mm. Over-stuffing (composite too thick) causes increased patellofemoral contact pressure, pain, limited flexion, and maltracking. Under-stuffing (composite too thin) reduces extensor moment arm, causes fracture risk, and patellar clunk syndrome. Measure carefully - this affects patient satisfaction significantly.

Dangers at this step

Patellar fracture from excessive resection (less than 10mm bone remaining unacceptable)
Asymmetric resection causing button malposition and tracking problems

Step 15: Trial Components: Femur, Tibia, Insert, Patella - Assess Stability and Tracking

Insert all trial components (femur, tibia, insert thickness based on gap assessment, patella). Reduce knee and perform comprehensive assessment: (1) ROM - should achieve greater than 120° flexion, full extension without lift-off or hyperextension; (2) Stability - no MCL or LCL laxity in extension, symmetric laxity in flexion, stable throughout range; (3) Patellar tracking - patella should remain centered in trochlear groove throughout full ROM without lateral or medial subluxation or tilt; (4) No impingement - smooth motion without catching or crepitus.

Exam Pearl

Technical Tip: Trial phase is CRUCIAL - this is final opportunity to identify and correct problems before cementing. Specifically test patellar tracking through full ROM watching for lateral maltracking (indicates femoral component internal rotation requiring re-cutting) or lateral subluxation (indicates need for lateral release or component revision). If ROM limited (less than 110° flexion OR extension lag greater than 5°), must identify cause (component malposition, inadequate balancing, retained osteophytes) and correct - NEVER cement suboptimal trial result.

Dangers at this step

Cementing malpositioned components (cannot be easily corrected after cement cures)
Missing patellar maltracking indicating rotational error (leading cause of revision)

Step 16: Prepare Bone Surfaces: Pulse Lavage, Dry Thoroughly

Remove all trial components. Pulse lavage all bone surfaces (tibia, femur, patella) with minimum 3 liters normal saline at high pressure removing blood, marrow fat, and debris. Dry bone with multiple laparotomy sponges applying pressure until no blood visible (truly dry surface). Pack wounds with dry sponges. Consider epinephrine-soaked sponges (1:500,000 concentration) if continued oozing.

Exam Pearl

Technical Tip: Bone preparation is ESSENTIAL for cement fixation - wet bone prevents cement penetration causing early aseptic loosening. Modern third-generation cement technique requires completely dry bone surface for optimal cement interdigitation (penetration 2-5mm into cancellous bone). Use aggressive pulse lavage (removes debris), then aggressive drying (multiple sponge packs). Blood or fat on surface reduces cement penetration by 50%. Time spent on preparation directly affects long-term fixation.

Dangers at this step

Inadequate drying causing poor cement interdigitation and early loosening (most common technical error)
Excessive epinephrine causing systemic absorption and cardiovascular effects (limit to single application)

Step 17: Mix Bone Cement and Apply to All Surfaces (Tibia, Femur, Patella)

Mix bone cement (typically two batches - first batch for tibia and patella, second batch for femur) using vacuum mixing system if available (reduces porosity). Wait for appropriate viscosity (can form into ball without sticking to gloves - 'dough stage'). Load into cement gun. Pressurize cement into bone surface using gun technique. Apply generous cement to bone surface AND implant undersurface. Avoid excess (causes thermal necrosis).

Exam Pearl

Technical Tip: Third-generation cement technique per AOANJRR reduces aseptic loosening from 10% to less than 2% at 10 years: (1) Pulsatile lavage removing debris; (2) Complete bone drying; (3) Pressurized cement application using gun (increases interdigitation depth); (4) Cement on BOTH bone and implant surfaces (creates cement mantle); (5) Component insertion before cement polymerization (allows extrusion of excess). Modern cementing is MANDATORY in Australia - cementless TKA has 2× revision rate per AOANJRR and should be avoided except research protocols.

Dangers at this step

Cement extrusion into soft tissues causing thermal injury or heterotopic ossification
Air entrainment creating porosity and weakening cement (use vacuum mixing)

Step 18: Insert Tibial Component First, Then Femoral Component, Then Patellar Button

Impact tibial tray ensuring full seating on cut surface and correct rotational alignment (tibial tubercle and second toe - medial third of tibial tubercle alignment). Insert femoral component ensuring full seating on all five cuts (distal, anterior, posterior medial and lateral, chamfers) and correct rotation (previously determined). Impact patellar button ensuring three pegs fully seated and button centered on patella. Remove excess cement immediately BEFORE polymerization using curette and sponge (easier than after curing).

Exam Pearl

Technical Tip: Component insertion sequence: tibia first (easier to position), then femur (seats on distal cut), then patella (smallest component). Remove excess cement continuously during polymerization (6-8 minutes) using curette - posterior cement extrusion can cause popliteal vein thrombosis or nerve compression. Maintain component position during cure (NO MOVEMENT - movement creates poor cement mantle). Common error: allowing component to shift during cure causing malposition or incomplete seating.

Dangers at this step

Component malpositioning if moved during cement cure (incomplete seating, rotation error)
Posterior cement extrusion causing popliteal vessel or nerve compression

Step 19: Insert Polyethylene Tibial Insert, Reduce Knee, Confirm ROM and Stability

After cement fully polymerized (8-10 minutes), snap polyethylene tibial insert into tibial tray confirming secure fixation with locking mechanism engaged (test by attempting to dislodge). Reduce knee with traction and gentle manipulation bringing patella into trochlear groove. Take knee through full ROM confirming: greater than 120° flexion, full extension to 0°, no impingement, stability throughout, patellar tracking centered. Perform final stability testing with varus-valgus stress in extension and flexion.

Exam Pearl

Technical Tip: Final assessment before closure - if ROM limited (less than 110° flexion OR extension lag greater than 5°) or instability detected at this point, must identify and correct cause (may require component revision if cemented poorly). Flexion less than 110° predicts poor functional outcome and patient dissatisfaction - cannot be easily corrected postoperatively. Extension lag greater than 5° causes abnormal gait and anterior knee pain. CANNOT leave operating room with suboptimal result - address now or patient suffers long-term.

Dangers at this step

Polyethylene insert dislodgement if locking mechanism not engaged (catastrophic mechanical failure)
Unrecognized instability causing early failure and patient dissatisfaction

Step 20: Release Tourniquet, Achieve Meticulous Hemostasis

Deflate tourniquet and wait 5-10 minutes for vasoreactive hyperemia response. Systematically identify and cauterize all bleeding vessels with bipolar electrocautery (or ligature if large vessels). Particular attention to medial and lateral gutters, quadriceps, and capsular edges. Consider topical hemostatic agents (tranexamic acid-soaked gauze, thrombin-based agents) for diffuse ooze.

Exam Pearl

Technical Tip: Hemostasis after tourniquet release reduces postoperative bleeding, hematoma formation, and infection risk - hematoma increases deep infection risk 3-fold. Systematic approach: identify arterial bleeders first (pulsatile), then venous bleeders (steady), then capillary ooze. Tranexamic acid 15mg/kg IV given at closure (per Australian eTG guidelines) reduces total blood loss by 30% and transfusion rate by 50% - consider routine use unless contraindicated (renal failure, thrombotic history).

Dangers at this step

Popliteal vascular injury (check distal pulses before closure - if absent, immediate exploration required)
Hematoma formation increasing infection risk and causing stiffness

Step 21: Copious Irrigation and Consider Drain Placement (Controversial)

Irrigate joint thoroughly with 3 liters normal saline removing all debris, cement particles, and blood clot. Suction until clear return. Drain placement remains controversial - traditional practice uses deep intra-articular drain removed at 24 hours, modern evidence shows no benefit and possible increased infection risk. AOANJRR data neutral on drain use. Acceptable to omit if excellent hemostasis achieved.

Exam Pearl

Technical Tip: Drain debate - traditional orthopedic teaching recommends routine drain use to prevent hematoma, but modern randomized trials show NO benefit for infection prevention, blood loss reduction, or ROM improvement. Potential HARM: drains may increase infection risk via retrograde contamination, and require handling/removal increasing nursing time. Current Australian practice: selective drain use (drain only if concerned about hemostasis or patient on anticoagulation), otherwise avoid. If used: single deep drain, remove at 24 hours maximum.

Dangers at this step

Drain-related infection from retrograde contamination (bacteria track along drain)
Drain retention causing chronic sinus tract formation

Step 22: Repair Arthrotomy: Medial Capsule, Quadriceps, Subcutaneous, Skin

Close medial arthrotomy with continuous No.1 Vicryl suture ensuring watertight closure (start distally at tibial plateau, work proximally to quadriceps). If quadriceps tendon extended proximally, repair with interrupted figure-of-8 No.1 Vicryl sutures. Close subcutaneous layer with 2-0 Vicryl interrupted or running suture. Close skin with staples (faster, equivalent outcomes to sutures) OR subcuticular 3-0 Monocryl for cosmesis. Apply sterile compression dressing with bulky gauze.

Exam Pearl

Technical Tip: Watertight arthrotomy closure prevents wound leakage and reduces infection risk - use continuous locking suture for security and tissue apposition. If tissue quality poor (inflammatory arthritis, revision surgery, chronic steroid use), use interrupted mattress sutures for stronger hold. Modern evidence supports early dressing removal (24-48 hours) to allow wound inspection rather than traditional 5-7 day occlusive dressing. Compression dressing reduces swelling and hematoma.

Dangers at this step

Wound dehiscence from inadequate closure or excessive tension (requires immediate re-closure)
Persistent leakage indicating intra-articular communication (increases infection risk dramatically)

Step 23: Post-operative: Immediate ROM Exercises, Mobilize Day 1, VTE Prophylaxis

Remove bulky dressing at 24 hours, apply lighter dressing. Begin ROM exercises immediately (continuous passive motion machine OR physiotherapy-directed active-assisted ROM - CPM no longer routinely recommended per modern evidence). Mobilize weight-bearing as tolerated with walking frame day 1, progress to crutches/stick by day 2-3. VTE prophylaxis per Australian eTG guidelines: enoxaparin 40mg subcutaneous daily × minimum 14 days, consider extending to 35 days for high-risk patients (prior VTE, thrombophilia, cancer). Alternative: aspirin 100mg daily × 35 days (equivalent efficacy per recent trials, lower bleeding risk).

Exam Pearl

Technical Tip: Early ROM is CRITICAL for preventing arthrofibrosis and stiffness - goal is 90° flexion by discharge (day 3-4), 110° by 6 weeks. If less than 90° at 6 weeks despite intensive physiotherapy, consider manipulation under anesthesia (MUA) - MUA effective if performed before 12 weeks, less effective after (scar maturation). Delayed mobilization and ROM initiation increases stiffness risk, VTE risk, muscle atrophy, and worse functional outcomes. Modern enhanced recovery protocols emphasize immediate mobilization same day of surgery.

Dangers at this step

Arthrofibrosis/stiffness from delayed ROM (most common complication 5-10%)
VTE (DVT/PE) despite prophylaxis (symptomatic VTE 2-5%, fatal PE 0.1-0.2%)

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"You are performing a primary TKA via medial parapatellar approach. After completing the bone cuts and trialling the components, you notice the patella tracks laterally during the last 30° of extension. What is the most likely cause and how would you address this intraoperatively?"

EXCEPTIONAL ANSWER

The most likely cause of lateral patellar maltracking in terminal extension is femoral component internal rotation malposition. I would systematically assess and address this as follows: First, I would verify femoral component rotation by examining the trial component position relative to the three rotational landmarks: (1) Whiteside's line (AP axis) - the component should be parallel, (2) transepicondylar axis - component should align, (3) posterior condylar axis - component should be 3° externally rotated. If the component is internally rotated, I must revise the femoral cuts. Second, I would remove the trial femoral component and re-mark all three landmarks. Third, I would make new femoral cuts at correct rotation (3° external to posterior condyles, confirming parallel to Whiteside's line). Fourth, after making corrected cuts, I would re-trial components and reassess patellar tracking through full range of motion. The patella should now track centrally without subluxation. If tracking is improved but mild lateral tracking persists, I would consider limited lateral retinacular release (2-3cm from lateral patellar edge). However, femoral component malrotation MUST be corrected primarily - lateral release alone will not solve internal rotation malposition and leads to chronic pain and eventual revision. Alternative causes to consider if rotation is correct: patellar button malposition (off-center, tilted), excessive patellar thickness (over-stuffing), inadequate lateral release if patella was tight during eversion. However, maltracking specifically in terminal extension is pathognomonic for femoral component internal rotation.

VIVA SCENARIOStandard

EXAMINER

"You have completed a primary TKA and achieved good intraoperative range of motion (0-130° flexion) with stable components. However, on postoperative day 3, the patient can only flex to 70° and has significant pain. What are your differential diagnoses and management approach?"

EXCEPTIONAL ANSWER

This patient has developed early postoperative stiffness with significant loss of range of motion compared to intraoperative assessment. My differential diagnosis in order of likelihood is: (1) Inadequate pain control limiting patient participation in physiotherapy, (2) Component malpositioning causing impingement (most commonly femoral component too large, over-stuffed patellofemoral joint, or excessive tibial slope), (3) Hematoma causing mechanical block to motion, (4) Quadriceps inhibition from pain or femoral nerve block residual effect, (5) Patient factors (anxiety, fear of pain, lack of motivation), (6) Early infection causing pain and effusion. My management approach would be systematic: First, assess pain control - if inadequate, optimize multimodal analgesia (paracetamol, NSAIDs, opioids, consider femoral nerve catheter). Second, perform clinical examination assessing for: wound complications (infection), joint effusion (hematoma or hemarthrosis), extensor lag (quadriceps function), and passive vs active ROM (distinguishing mechanical block from muscle inhibition). Third, obtain AP and lateral radiographs checking component position, patellar height, and joint space. Fourth, check inflammatory markers (ESR, CRP) - if elevated consider infection or hematoma. If pain controlled and no mechanical cause identified, intensive supervised physiotherapy with therapist-assisted ROM exercises (gentle manipulation, continuous passive motion). If large hematoma identified on exam or ultrasound causing mechanical block, consider aspiration (send for culture). If no improvement with 48 hours of optimized pain control and intensive physiotherapy, return to operating room for examination under anesthesia (EUA) - assess ROM, if improves under anesthesia confirming pain as limiting factor continue conservative management, if ROM still limited suggesting mechanical cause, perform arthroscopy identifying and treating cause (remove hematoma, débride adhesions, assess component position). If component malpositioning identified, revision may be required.

VIVA SCENARIOStandard

EXAMINER

"A 58-year-old patient with severe valgus deformity (20° valgus alignment) requires TKA. What are the specific challenges and risks of this case compared to varus deformity, and how would you counsel the patient preoperatively? Describe your surgical strategy for soft tissue balancing."

EXCEPTIONAL ANSWER

Severe valgus deformity (greater than 15°) presents significantly greater technical challenges and risks compared to varus deformity in TKA, and requires specific preoperative counseling and surgical planning. The key challenges are: (1) Lateral soft tissue contractures including ITB, lateral capsule, popliteus, LCL, and lateral head of gastrocnemius requiring extensive release for gap balancing, (2) Lateral bone deficiency requiring augmentation or bone grafting, (3) Common peroneal nerve at high risk of traction injury during acute correction (2-5% palsy risk with deformity greater than 15° valgus), (4) Patella alta and extensor mechanism lateralization making patellar tracking difficult. My preoperative counseling would specifically address: Inform patient of higher complication rate compared to neutral alignment, specifically 2-5% risk of common peroneal nerve palsy causing foot drop (may be permanent, requiring AFO), possibility of staged correction if deformity greater than 20° (initial correction to 10° valgus, staged second TKA 3-6 months later for final correction), potential need for constrained implants (varus-valgus constrained or hinged) if instability persists despite soft tissue balancing, longer operative time and potentially greater blood loss, longer rehabilitation due to extensive soft tissue releases. My surgical strategy would be: First, complete exposure and peripheral osteophyte removal - release lateral structures extraarticularly before bone cuts (ITB, lateral capsule). Second, perform standard bone cuts (tibial cut perpendicular to mechanical axis, femoral cut at appropriate valgus - may need 8-9° due to native anatomy). Third, assess extension gap - valgus deformity will show lateral tightness and medial laxity. Fourth, perform sequential lateral release in following order: (a) Release lateral capsule and popliteus from proximal tibia, (b) Release LCL from lateral femoral epicondyle, (c) Release lateral head of gastrocnemius, (d) Consider ITB lengthening (Z-plasty) or release. Fifth, reassess extension gap after each release step - goal is symmetric rectangular gap. Sixth, assess flexion gap and balance as standard. Seventh, if instability persists despite maximum releases, convert to constrained implant (varus-valgus constrained or hinged). Eighth, minimize acute correction force on nerve - consider bent-knee position during closure to relax peroneal nerve.