TKA Periprosthetic Joint Infection

Wound:

• Erythema (diffuse vs localized)
• Swelling (effusion vs soft tissue edema)
• Sinus tract or draining wound (MAJOR criterion if communicates with prosthesis)
• Surgical scars (assess healing, any dehiscence)

Limb:

• Leg alignment (varus/valgus deformity suggests loosening)
• Muscle wasting (chronic infection impairs function)
• Skin changes (chronic venous stasis, dependent rubor)

Local temperature: Warmth over joint (compare to contralateral)

Effusion: Moderate to large effusion common in PJI (but also aseptic loosening)

Tenderness: Diffuse joint line tenderness (infection) vs focal (mechanical)

Lymphadenopathy: Inguinal nodes may be enlarged in chronic infection

Range of motion:

• Active and passive ROM (stiffness suggests infection or arthrofibrosis)
• Painful arc or end-range pain
• Loss of ROM compared to prior assessments (concerning for infection)

Stability:

• Varus/valgus stress (loosening vs intact collaterals)
• Anteroposterior drawer (implant stability)

Crepitus: Suggests polyethylene wear or loosening (not specific for infection)

Neurovascular assessment:

• Pulses (dorsalis pedis, posterior tibial)
• Sensation (common peroneal nerve distribution - dorsal foot)
• Motor (ankle dorsiflexion - common peroneal; plantarflexion - tibial)

Systemic examination:

• Temperature (fever in acute infection)
• Signs of sepsis (tachycardia, hypotension, confusion in severe cases)

Tests to order:

• CRP (threshold over 10 mg/L = 1 MSIS point)
• ESR (threshold over 30 mm/hr = 1 MSIS point)
• D-dimer (threshold over 860 ng/mL = 2 MSIS points) - ICM 2018 addition
• WCC (usually normal unless acute severe infection)

Interpretation:

• Sensitivity: CRP 80%, ESR 75%, D-dimer 89%
• Specificity: CRP 70%, ESR 65%, D-dimer 65%
• Non-specific: Elevated in inflammatory arthritis, recent surgery, obesity
• Normal CRP does NOT exclude PJI: 20% of chronic low-virulence CNS infections have normal CRP

Serial markers: Trend more useful than single value (rising CRP concerning even if under 10)

Plain radiographs (AP, lateral, skyline views):

• Lucency: Greater than 2mm periprosthetic lucency (suggests loosening, may be septic or aseptic)
• Progressive lucency: Serial films showing widening (infection or loosening)
• Periosteal reaction: New bone formation along femoral or tibial cortex (chronic infection)
• Subsidence: Component migration (loosening - cause unclear without aspiration)
• Sensitivity: 50% only (late finding)

Utility: Rules out obvious loosening/osteolysis but does NOT diagnose infection

Critical preparatory step: Antibiotic holiday minimum 2 weeks (ideally 6 weeks) before aspiration

Technique:

• Sterile prep (chlorhexidine, drape)
• Approach: Lateral or superolateral (avoids suprapatellar pouch - better yield)
• Volume: Aspirate minimum 3-5 mL for adequate culture and cell count
• Send: Cell count/differential, culture (aerobic + anaerobic + fungal if immunosuppressed, hold 14 days), alpha-defensin, leukocyte esterase

Synovial fluid analysis (MSIS scoring):

• WCC over 3000 cells/μL = 2 points
• PMN over 70% = 1 point (do NOT double-score with WCC - count only WCC 2 points)
• Alpha-defensin positive = 3 points (best single marker: 97% sens, 96% spec)
• Leukocyte esterase ++ = 3 points (point-of-care, + = 2 points)

Culture yield: 65-90% sensitivity (higher if adequate antibiotic holiday)

Dry tap: If aspiration yields no fluid, consider saline injection (5-10mL sterile saline, agitate knee, re-aspirate) to lavage joint and improve yield

Nuclear medicine:

• Bone scan (Tc-99m MDP): Sensitive (90%) but non-specific (50%) - positive in infection AND aseptic loosening
• Labeled WBC scan (In-111 or Tc-99m HMPAO): 85% sensitivity, 80% specificity for infection
• Combined WBC + sulfur colloid: Improves specificity to 85% (photopenic mismatch suggests infection)

PET-CT:

• Emerging modality
• Sensitivity 85-95%, specificity 80-90%
• Expensive, limited availability
• Useful if aspiration non-diagnostic and high clinical suspicion

MRI: Limited by metal artifact. MARS (metal artifact reduction sequences) may help assess soft tissue but does NOT reliably diagnose PJI

Sample collection protocol:

• Minimum 5-6 tissue samples from different sites (capsule, bone-implant interface, femoral canal, tibial plateau, medial gutter, lateral gutter)
• Avoid superficial tissue (contamination risk)
• Send for: Aerobic culture, anaerobic culture, fungal culture (if immunosuppressed), permanent histology
• Hold cultures 14 days for slow-growing organisms

Frozen section histology:

• Threshold: Over 5 PMN/hpf in 5 high-power fields at 400x magnification = positive for infection
• Sensitivity 80-85%, specificity 90-95%
• Result in 20-30 minutes - allows intraoperative decision (proceed with reimplantation vs abort)

Permanent histology:

• Type II/III interface membrane (lymphocytic infiltration with PMN predominance)
• More sensitive than frozen section but delayed result (3-5 days)
• Useful for confirmation if frozen section borderline

Intraoperative purulence: MAJOR criterion (definite PJI) - if frankly purulent fluid/tissue encountered, infection confirmed regardless of cultures

Radical synovectomy:

• Remove ALL synovium (anterior, posterior, medial, lateral compartments)
• Debride interface membrane around components
• Remove cement if gross contamination visible
• Excise any devitalized tissue or hematoma

Polyethylene exchange:

• Mandatory exchange of modular polyethylene insert
• New insert from sterile tray (not re-sterilized used insert)
• Consider exchange of femoral component if modular cemented (controversial)

Volume: Minimum 6-9 liters normal saline pulsed lavage

Technique:

• Pulsed lavage to mechanically disrupt biofilm
• Avoid high-pressure jet (drives bacteria into bone)
• Change gloves, instruments after debridement before irrigation

No chlorhexidine, betadine, or antibiotic solutions (cytotoxic to tissue, no proven benefit).

Closure:

• Layered closure (capsule, subcutaneous, skin)
• No dead space

Drain:

• Consider closed suction drain for 24-48 hours
• Some evidence: Prolonged drainage (over 7 days) increases reinfection risk - remove early

Empiric (until cultures result):

• Vancomycin 15-20 mg/kg IV q12h (target trough 15-20 μg/mL)
• PLUS meropenem 1g IV q8h OR ceftazidime 2g IV q8h

Organism-specific (adjust based on culture):

• MSSA: Flucloxacillin 2g IV q6h + rifampicin 300-450mg PO q12h
• MRSA: Vancomycin (as above) + rifampicin
• Streptococcus: Penicillin G 3 million units IV q4h OR ceftriaxone 2g IV q24h
• GNR: Fluoroquinolone (ciprofloxacin 750mg PO q12h) + rifampicin (if E. coli, not Pseudomonas)

Duration:

• IV antibiotics: 2-6 weeks (debate ongoing - some centers 2 weeks, others 6 weeks)
• Oral suppression: 3-6 months with biofilm-active agent (rifampicin-based combinations)

Rifampicin importance: Penetrates biofilm, active against stationary-phase bacteria. NEVER use as monotherapy (resistance develops rapidly). Always combine with flucloxacillin, vancomycin, or fluoroquinolone.

Technique:

• Remove ALL foreign material (components, cement, sutures, cerclage wires)
• Use cement extraction tools, high-speed burr, osteotomes
• Preserve bone stock: Avoid aggressive bone removal unless grossly infected

Tissue sampling:

• 5-6 samples from capsule, bone-implant interface, femoral canal, tibial plateau
• Send for aerobic, anaerobic, fungal culture (hold 14 days)
• Send for histology (frozen section + permanent)

Radical debridement:

• Remove ALL synovium, interface membrane, granulation tissue
• Curette bone surfaces to expose bleeding bone
• Excise any necrotic or devitalized tissue
• Pulsed lavage 9-12 liters normal saline

Spacer type:

• Static (block) spacer: Block of antibiotic cement, NO articulation
• Articulating (mobile) spacer: Knee-shaped mold or commercial system (PROSTALAC, Spacer-K)

Comparison:

• Infection eradication: Equal (both 85-90%)
• Function: Articulating better range of motion, easier mobilization
• Bone loss: Static has more bone loss from immobilization
• Cost: Articulating more expensive (commercial systems $3000-5000)

Australian practice: Articulating spacers preferred in mobile patients due to better function and reduced bone loss during interval.

Antibiotic cement formulation:

• Base: 40g Palacos R cement (PMMA)
• Vancomycin: 4-6g (4g standard, 6g if MRSA or high bacterial load)
• Aminoglycoside: 3-4g tobramycin OR 3.6g gentamicin
• Maximum 10% antibiotic by weight to maintain mechanical strength

Rationale: Vancomycin (Gram-positive coverage) + aminoglycoside (Gram-negative + synergy). Achieves local concentrations 100x higher than systemic antibiotics, overcomes biofilm MIC.

Technique:

• Mix antibiotics into cement powder before adding liquid monomer
• Hand-mold or use commercial mold for articulating spacer
• Insert into femoral and tibial bone with gentle pressurization
• Allow full polymerization (10 minutes) before closure

Standard closure:

• Layered closure, closed suction drain 48 hours
• Splint in extension or slight flexion (articulating spacer allows early ROM)

Weight-bearing: Touch weight-bearing with walker (spacer is NOT designed for full load)

Approach:

• Same incision as Stage 1 (excise prior scar)
• Careful dissection to preserve extensor mechanism
• Remove spacer (may be adherent to bone - use gentle osteotomes)

Tissue sampling:

• 3-5 intraoperative cultures from synovium, bone surfaces
• Frozen section histology
• If positive cultures or over 5 PMN/hpf: ABORT reimplantation, place new spacer, extended antibiotics

Debridement:

• Remove residual spacer cement fragments
• Synovectomy of any granulation tissue
• Lavage 6-9 liters pulsed irrigation

Bone preparation:

• Often bone loss from infection and spacer interval
• May require stems (femoral and tibial) for stability
• Consider augments (blocks, wedges) for metaphyseal defects

Implant selection:

• Constrained condylar knee (CCK): Most common for PJI revisions (MCL/LCL deficiency from debridement)
• Rotating hinge: If severe bone loss, collateral deficiency, or extensor lag
• Stems: Long cemented stems (100-120mm) for stability in weakened bone
• Augments: Metal blocks or wedges for metaphyseal bone loss

Cemented vs uncemented:

• Cemented preferred in revision after PJI: Allows antibiotic cement use
• Antibiotic cement: Vancomycin 2g per 40g cement (lower dose than spacer, to preserve mechanical strength)
• Some controversy: Antibiotic cement at reimplantation reduces reinfection 10% vs 15% (marginal benefit)

Technique:

• Cement pressurization with stem centralizers
• Ensure adequate cement mantle (2-3mm)
• No tourniquet during cementation (optimize cement interdigitation)

Soft tissue challenges:

• Scarring from multiple surgeries
• Extensor mechanism may be attenuated
• Consider gastrocnemius flap if inadequate soft tissue coverage
• Skin closure: May require plastic surgery involvement for complex cases

Closure:

• Layered closure, closed suction drain 48 hours
• Knee immobilizer or hinged brace for 6 weeks (protect extensor mechanism)

Duration debate:

• Option 1: Organism-specific IV antibiotics 6 weeks (traditional)
• Option 2: No postoperative antibiotics if negative intraoperative cultures (emerging practice)
• Australian practice: Variable - many centers give 2-4 weeks organism-specific if cultures negative intraoperatively, 6 weeks if positive

Rationale for NO antibiotics: Stage 2 is a "clean" revision if infection eradicated. Prolonged antibiotics may increase C. difficile risk and antibiotic resistance without proven benefit.

Rationale FOR antibiotics: "Margin of safety" in high-risk host, resistant organisms, or positive intraoperative cultures (even if deemed contamination).

Approach: Use prior incision, excise wound edges if contaminated.

Arthrotomy: Standard medial parapatellar approach, evert patella.

Initial assessment: Assess polyethylene condition, implant stability (varus/valgus stress, AP drawer).

Remove ALL synovium:

• Anterior compartment (suprapatellar pouch)
• Medial and lateral gutters
• Posterior compartments (difficult access - use curved curettes)
• Intercondylar notch

Interface debridement:

• Curette bone-implant interface (femoral component undersurface, tibial baseplate undersurface)
• Remove interface membrane and granulation tissue
• If gross purulence or cement contamination, consider cement removal (convert to 2-stage)

Technique: Aggressive synovectomy is KEY. Incomplete removal leaves biofilm reservoir leading to DAIR failure.

Remove modular insert:

• Unlock mechanism (varies by implant system)
• Remove polyethylene insert completely
• Inspect tibial baseplate and femoral component for damage

Insert new polyethylene:

• From STERILE UNOPENED tray (NOT re-sterilized used insert)
• Same thickness or adjust for soft tissue tension
• Lock securely into tibial baseplate

Rationale: Biofilm on polyethylene cannot be debrided. Bacteria absorbed into polyethylene matrix serve as infection reservoir. Exchange is MANDATORY - reduces failure rate 50%.

Volume: 9-12 liters normal saline pulsed lavage (minimum 6 liters).

Technique:

• Pulsed lavage with moderate pressure (NOT high-pressure jet - drives bacteria into bone)
• Change gloves, instruments, gown AFTER debridement BEFORE irrigation (avoid recontamination)
• No additives: Do NOT use chlorhexidine, betadine, or antibiotic solutions (cytotoxic to cartilage and tissue)

Goal: Mechanical biofilm disruption and bacterial washout.

Layered closure:

• Capsule (absorbable suture, watertight)
• Subcutaneous (eliminate dead space)
• Skin (absorbable subcuticular OR staples)

Drain: Closed suction drain for 24-48 hours (remove when output under 30mL/8h).

Dressing: Occlusive dressing for 48 hours minimum.

Approach: Prior incision, excise scar and any sinus tract en bloc.

Explantation:

• Remove polyethylene insert
• Remove femoral component (cemented: osteotomes, thin flexible saw; uncemented: slap hammer with offset attachments)
• Remove tibial component (cemented: osteotomes from periphery; uncemented: slap hammer)
• Extract ALL cement (high-speed burr, cement extraction tools, narrow osteotomes)

Goal: Remove ALL foreign material. Residual cement is biofilm nidus and leads to reinfection.

Preserve bone stock: Avoid aggressive bone removal unless grossly necrotic.

Sample sites (minimum 5-6 samples):

• Capsule (anterior and posterior)
• Bone-implant interface (femoral and tibial)
• Femoral canal (stem interface)
• Tibial plateau bone
• Any purulent or suspicious tissue

Send for: Aerobic, anaerobic, fungal culture (hold 14 days) + permanent histology.

Frozen section: Over 5 PMN/hpf in 5 hpf at 400x = infection confirmed.

Remove:

• ALL synovium (medial, lateral, posterior, intercondylar)
• Interface membrane (curette bone surfaces to bleeding bone)
• Granulation tissue, necrotic tissue, hematoma

Lavage: 9-12 liters pulsed irrigation normal saline.

Goal: Reduce bacterial burden to minimal levels before spacer insertion.

Formulation (per 40g Palacos R cement):

• Vancomycin 4-6g (4g standard, 6g if MRSA or high bioburden)
• Tobramycin 3-4g OR gentamicin 3.6g
• Maximum 10% antibiotic by weight (maintain mechanical strength)

Mixing: Add antibiotic powders to cement powder BEFORE adding liquid monomer. Mix thoroughly.

Spacer type:

• Articulating (mobile): Hand-molded knee-shaped mold OR commercial system (PROSTALAC, Spacer-K). Allows ROM during interval, reduces bone loss, better function.
• Static (block): Hand-molded block of cement. Immobilization (knee immobilizer), more bone loss, but simpler and cheaper.

Insertion technique (articulating):

• Mold femoral component shape (condyles, trochlea)
• Mold tibial platform
• Insert into bone with gentle pressurization (NOT full cement technique - spacer is temporary)
• Allow full polymerization (10 minutes) before manipulating knee
• Test ROM (should achieve 60-90 degrees flexion with articulating spacer)

Antibiotic release kinetics: Aminoglycoside elutes rapidly (peak 24-48h, high local concentration), vancomycin elutes slowly (sustained over 6-12 weeks).

Layered closure: Capsule, subcutaneous, skin.

Drain: Closed suction 48 hours.

Immobilization: Knee immobilizer OR hinged brace locked in extension (if static spacer). Articulating spacer allows immediate ROM.

Weight-bearing: Touch weight-bearing with walker (spacer NOT designed for full load - fracture risk).

Approach: Same incision (excise prior scar), careful dissection (extensor mechanism preservation).

Remove spacer: May be adherent to bone - use gentle osteotomes, avoid fracture or excessive bone removal.

Tissue sampling: 3-5 intraoperative cultures from synovium and bone surfaces.

Frozen section: If over 5 PMN/hpf OR positive cultures → ABORT reimplantation, place new spacer, extend antibiotics.

Debridement: Remove residual spacer cement fragments, any granulation tissue.

Lavage: 6-9 liters pulsed irrigation.

Bone assessment:

• Often bone loss from infection and spacer interval
• Classify defects (Anderson Orthopaedic Research Institute classification: Type 1 intact metaphyseal bone → Type 3 severe metaphyseal and diaphyseal bone loss)

Bone preparation:

• Broach/ream to bleeding bone
• Size for stems if bone loss present
• Plan for augments (metal blocks/wedges) if metaphyseal defects

Implant type (based on bone loss and soft tissue integrity):

• Posterior-stabilized (PS): If minimal bone loss, intact collaterals (rare after PJI)
• Constrained condylar knee (CCK): Most common for PJI revisions (accommodates MCL/LCL deficiency from debridement)
• Rotating hinge: If severe bone loss, complete collateral deficiency, or extensor mechanism dysfunction

Stems: Long cemented stems (100-150mm) for stability in weakened bone. Offset stems if deformity or bone loss.

Augments: Metal blocks or wedges for metaphyseal bone defects (femoral or tibial). Secure with screws or cement.

Fixation: Cemented preferred after PJI (allows local antibiotic delivery). Antibiotic cement: Vancomycin 2g per 40g cement (lower than spacer dose to preserve mechanical strength).

Technique: Full cement technique with pressurization, stem centralizers, ensure 2-3mm cement mantle.

Challenges: Scarring from multiple surgeries, extensor mechanism attenuation, skin closure under tension.

Extensor mechanism: If attenuated or deficient, consider allograft augmentation or accept extensor lag with chronic brace.

Soft tissue coverage: If inadequate skin/subcutaneous tissue, gastrocnemius flap (medial head - easier; lateral head - better coverage). Coordinate with plastic surgery.

Closure: Layered (capsule, subcutaneous, skin). Drain 48h. Knee immobilizer or hinged brace for 6 weeks (protect extensor mechanism).

Antibiotics: Continue empiric IV antibiotics (vancomycin + meropenem OR ceftazidime) until cultures result, then switch to organism-specific.

Drain management: Remove closed suction drain at 24-48h when output under 30mL/8h.

Wound care: Occlusive dressing intact for 48h minimum. Inspect at 48h for erythema, drainage.

Mobilization: Day 0 or Day 1 - sit to stand, ambulation with walker. Full weight-bearing as tolerated (implant retained, stable).

ROM: Start passive ROM exercises Day 1 (CPM OR physiotherapy). Goal: Maintain preoperative ROM.

DVT prophylaxis: Aspirin 100mg daily OR rivaroxaban 10mg daily for 14 days. Mechanical prophylaxis (TED stockings, foot pumps).

Antibiotics:

• IV organism-specific for 2-6 weeks (debate: some centres 2 weeks, others 6 weeks)
• Common regimens: (MSSA) Flucloxacillin 2g IV q6h + rifampicin 450mg PO q12h. (Strep) Penicillin G 3M units IV q4h OR ceftriaxone 2g IV q24h.
• Outpatient parenteral antibiotic therapy (OPAT): PICC line, home IV administration OR daily infusion clinic visits

Clinical monitoring:

• CRP weekly (should decline by 50% at 2 weeks post-DAIR - if not, DAIR failing)
• Wound inspection weekly (no persistent drainage)
• Pain and function assessment

Physiotherapy: Progressive ROM and strengthening. Goal: 0-110 degrees by 6 weeks.

Weight-bearing: Full weight-bearing, progress from walker to cane to independent.

Transition to oral:

• After 2-6 weeks IV, switch to oral suppression for 3-6 months
• Biofilm-active agents: Rifampicin combinations (NEVER rifampicin monotherapy - resistance develops in days)
• (MSSA) Rifampicin 450mg PO q12h + flucloxacillin 1g PO q6h
• (Strep) Amoxicillin 1g PO q8h (rifampicin not required)
• (GNR E. coli) Ciprofloxacin 750mg PO q12h + rifampicin 450mg PO q12h

Monitoring: CRP monthly, clinical assessment monthly. Rising CRP = DAIR failure, consider 2-stage.

Function: Return to activities of daily living by 3 months. Avoid high-impact sports lifelong.

Follow-up: 3 months, 6 months, 12 months, then yearly.

Assessment: Pain, function, ROM, stability. CRP annually.

Radiographs: Yearly to assess for loosening or progressive lucency (late failure).

Education: Prompt reporting of acute pain, swelling, fever (acute hematogenous infection risk lifelong).

Antibiotics: Continue IV antibiotics (organism-specific if cultures available, empiric if pending).

Immobilization: Knee immobilizer (static spacer) OR hinged brace unlocked for ROM (articulating spacer).

Weight-bearing: Touch weight-bearing only with walker (spacer not designed for full load - fracture risk 10-25%).

Drain: Remove at 48h.

Duration: 6 weeks IV organism-specific antibiotics (some centres 2-4 weeks for virulent organisms with rapid response).

OPAT: PICC line, home IV OR daily clinic.

Monitoring: Weekly CRP (should normalize to under 10 by 6 weeks). Clinical assessment weekly (no pain, drainage, erythema).

Mobilization: Limited weight-bearing (touch weight-bearing with walker). Articulating spacer allows ROM exercises (goal: 60-90 degrees maintained).

Complications: Spacer fracture, dislocation, persistent drainage (see Complications section). Return to OR if needed.

Concept: 2-week antibiotic-free interval before Stage 2 to assess for infection recurrence off antibiotics.

Practice variable: Some centres routinely do antibiotic holiday, others do NOT (proceed to Stage 2 at 6-8 weeks if CRP normalized without holiday).

Rationale for: Unmasks infection suppressed by antibiotics (CRP rebound suggests persistent infection).

Rationale against: Delays reimplantation, no evidence improves eradication rates.

Australian practice: Variable. Trend is NO routine holiday if clinical/serologic resolution clear.

Criteria for Stage 2 readiness:

1. CRP normalized (under 10 mg/L, some accept under 20 if downtrending)
2. Clinical resolution (no pain, swelling, erythema, drainage)
3. Adequate soft tissue coverage (no open wounds, good skin quality)
4. Medical optimization (HbA1c under 7%, albumin over 3.5, smoking cessation)

Aspiration of spacer: Controversial. Some centres routinely aspirate before Stage 2, others do NOT (false-positive rate 10-20% due to spacer irritation). Australian trend: NO routine aspiration if clinical/serologic clear.

Radiographs: Assess spacer position, bone stock, plan for stems/augments at Stage 2.

Antibiotics: Controversial. (Option 1) No antibiotics if cultures negative intraoperatively. (Option 2) 2-4 weeks organism-specific. (Option 3) 6 weeks if positive cultures.

Immobilization: Knee immobilizer OR hinged brace locked for 6 weeks (protect extensor mechanism, prevent dislocation if constrained implant).

Weight-bearing: Touch weight-bearing with walker initially (protect fixation and extensor mechanism).

Drain: Remove at 48h.

Brace: Locked knee immobilizer OR hinged brace locked in extension during ambulation. Unlock for ROM exercises under physiotherapy supervision.

Weight-bearing: Progress to partial weight-bearing (50%) by 2 weeks, weight-bearing as tolerated by 6 weeks.

ROM: Passive ROM exercises (CPM OR physiotherapy) in brace unlocked. Goal: 0-90 degrees by 6 weeks (accept less - scarring limits motion).

Antibiotics: If given, IV 2-6 weeks then discontinue (no long-term suppression after successful 2-stage).

Monitoring: CRP at 2 weeks, 6 weeks (should remain low). Rising CRP suggests reinfection - investigate urgently.

Brace: Wean off immobilizer at 6 weeks if extensor mechanism intact, wound healed.

Weight-bearing: Full weight-bearing, progress to cane then independent.

Physiotherapy: Quadriceps strengthening (critical - extensor lag common after 2-stage). Hydrotherapy beneficial.

ROM: Active ROM exercises. Goal: 0-100 degrees by 12 weeks (accept 90 - scar tissue limits gains).

Radiographs: 6 weeks and 12 weeks to assess fixation, lucency, alignment.

Timeline: Full recovery 6-12 months (longer than uncomplicated primary TKA).

Function: Knee Society Score 70-80 (vs 90+ for uncomplicated primary). Accept functional limitations (stiffness, activity restrictions).

ROM: Final ROM 90-100 degrees average (vs 120 for primary TKA). Manipulation under anesthesia at 6-12 weeks if under 70 degrees and interfering with function.

Activities: Return to low-impact activities (walking, swimming, cycling). Avoid high-impact sports lifelong.

Surveillance: 3, 6, 12 months, then yearly. CRP annually. Radiographs yearly for 5 years.

Standard regimen:

• Cefazolin 2g IV (3g if patient weight over 120kg)
• Timing: Within 60 minutes before incision (ideally 30-60 minutes)
• Redosing: If surgery duration over 4 hours OR blood loss over 1500mL, give second dose intraoperatively

Penicillin allergy (non-anaphylactic):

• Cefazolin still acceptable (10% cross-reactivity, but severe reactions rare)

Penicillin allergy (anaphylaxis history):

• Vancomycin 15mg/kg IV (infuse over 1 hour - start 90-120 minutes before incision) PLUS
• Gentamicin 5mg/kg IV (single dose)

MRSA colonization known:

• Vancomycin 15mg/kg IV PLUS cefazolin 2g IV (dual coverage superior to vancomycin alone)

Duration: Single dose is standard. NO prolonged prophylaxis beyond 24 hours (increases C. diff and resistance without reducing PJI).

Antiseptic choice:

• Chlorhexidine-alcohol (2% chlorhexidine + 70% isopropyl alcohol) is superior to povidone-iodine
• Reduces SSI by 40% vs iodine (RCT evidence)

Application:

• Two separate applications with dry time (3 minutes each)
• Prep wide field (hip to ankle for knee)
• Do NOT use chlorhexidine near mucous membranes or eyes (ototoxicity, neurotoxicity if enters joint accidentally)

Hair removal:

• Clipping only if hair interferes with incision (do NOT shave - microabrasions increase infection)
• Clip immediately before surgery (NOT night before - allows bacterial regrowth)

Laminar flow: Reduces airborne bacterial count 90% vs conventional ventilation. Standard in Australia for arthroplasty.

Traffic control: Minimize door openings (each opening disrupts laminar flow for 5 minutes). Limit personnel to essential staff.

Body exhaust suits: Controversial. Some evidence of reduced infection, but uncomfortable and expensive. Not universally adopted.

Temperature: Maintain patient normothermia (over 36°C core temperature). Hypothermia increases infection risk 30% via vasoconstriction and impaired neutrophil function.

Minimize operative time: Each additional 30 minutes increases PJI risk 15%. Efficient technique without rushing.

Gentle tissue handling: Avoid excessive retraction, cautery. Preserve blood supply to skin edges.

Hemostasis: Meticulous hemostasis reduces hematoma (substrate for bacterial growth). Use of tranexamic acid (TXA) reduces blood loss and hematoma formation - may reduce PJI risk (emerging evidence).

Wound irrigation: 3-6 liters pulsed lavage before closure. Normal saline only (no chlorhexidine, betadine, antibiotics - cytotoxic).

Closure: Layered closure (capsule, subcutaneous, skin). Avoid dead space. Skin closure: Absorbable subcuticular suture OR staples (similar infection rates).

Debate:

• Proponents: Reduces hematoma (substrate for infection)
• Opponents: Foreign body, retrograde bacterial entry, no proven benefit

Evidence: Meta-analysis shows no difference in PJI with or without drains.

Australian practice: Variable. Many surgeons use closed suction drain for 24-48 hours, remove when output under 30mL/8hr.

Consensus: If drain used, remove early (under 48 hours). Prolonged drainage (over 7 days) increases PJI risk 3-fold.