High Yield Overview

REVISION TOTAL KNEE REPLACEMENT (RTKR)

Complex arthroplasty procedure addressing failed primary TKR through systematic component revision and bone reconstruction | advanced

Critical Danger Structures - 5 Key Anatomical Zones

Popliteal Artery

Location: 10-15mm posterior to posterior tibial cortex, even closer with posterior bone loss

Protection: Maintain knee flexion when working posteriorly, use retractors to protect posterior structures, gentle cement removal technique, avoid aggressive posterior osteotome use

Risk: 0.1-0.3% injury rate (3-10x higher than primary), devastating if unrecognized

Common Peroneal Nerve

Location: Around fibular neck, at risk with lateral exposure and valgus correction

Protection: Gradual deformity correction, avoid forced lengthening, identify nerve if severe valgus, warn patient pre-operatively

Risk: 2-5% palsy rate (4-10x higher than primary), especially with hinged prostheses

Patellar Tendon

Location: Anterior insertion at tibial tubercle, vulnerable during patella eversion

Protection: NEVER force eversion, adequate medial/lateral releases, perform quadriceps snip or TTO if difficult, maintain 15mm patellar composite

Risk: 1-3% avulsion rate, catastrophic complication with 50-70% residual extensor lag

Collateral Ligaments

Location: MCL femoral origin 3-4mm proximal/posterior to medial epicondyle, LCL at lateral epicondyle

Protection: Careful soft tissue handling with scar tissue, avoid overzealous releases, assess integrity and match constraint

Risk: Iatrogenic injury requires increased constraint, impacts stability and outcomes

Posterior Capsule

Location: Posterior to femoral condyles and tibial plateau

Protection: Gentle cement removal, controlled flexion during exposure, retractor placement under direct vision

Risk: Disruption causes instability, bleeding, and potential vascular injury

Mnemonic

REVISEREVISE - Critical Steps in Revision TKR

Mnemonic

CONESCONES - Trabecular Metal Cone Indications and Technique

Indications for Revision TKR

Aseptic Loosening (28% of revisions per AOANJRR)

Progressive pain with weight-bearing activity
Radiographic evidence of progressive radiolucency (>2mm at component-bone or component-cement interface)
Component subsidence or migration
Knee Society Score typically <60 points

Instability (22% of revisions)

Flexion instability: tight extension gap, loose flexion gap
Extension instability: loose extension gap, tight flexion gap
Mid-flexion instability: femoral component undersized or malrotated
Global instability: inadequate constraint for ligamentous insufficiency

Infection (21% of revisions)

Acute post-operative infection <3 weeks: DAIR considered
Chronic infection >3 weeks: two-stage revision gold standard
Elevated ESR/CRP, positive aspiration (>3000 WBC, >80% PMN)
Two-stage success rate 70-80%, DAIR 40-50% in revision setting

Polyethylene Wear and Osteolysis (12%)

Visible wear on radiographs
Osteolytic lesions expanding
Backside wear with mobile-bearing designs
Address before catastrophic bone loss

Periprosthetic Fracture (8%)

Supracondylar femur fracture (most common)
Tibial plateau fracture
Patellar fracture
Lewis and Rorabeck Type III requires revision with loose implant

Other Indications (9%)

Component malposition causing pain, stiffness, or instability
Arthrofibrosis refractory to conservative management
Unexplained pain after exclusion of infection and malalignment

Pre-operative Planning

Imaging Assessment

Weight-bearing AP and lateral knee radiographs
Merchant view for patellofemoral assessment
Full-length hip-knee-ankle radiographs for alignment
CT scan with metal artifact reduction: invaluable for assessing 3D bone loss, component rotation, planning reconstruction
Consider SPECT-CT for painful TKR without obvious cause
MRI if extensor mechanism concern (tendon integrity)

Laboratory Investigation

ESR and CRP mandatory to exclude infection
If elevated: knee aspiration (cell count, differential, culture)
Consider alpha-defensin or PJI biomarkers if high suspicion
Optimization: HbA1c <7.0%, albumin >3.5g/dL, vitamin D >30ng/mL

AORI Classification Assessment

Type 1: Intact metaphyseal bone (minor defects)
Type 2A: Damaged metaphyseal bone, contained defect one side
Type 2B: Uncontained defect one condyle
Type 2C: Uncontained defects both condyles
Type 3: Severe metaphyseal damage affecting collateral attachments

Templating and Implant Planning

Template component sizes (typically upsize 1-2 from primary)
Plan augment requirements (5mm, 10mm, 15mm wedges/blocks)
Determine stem lengths (typically 100-150mm press-fit)
Consider need for cones (Type 2C/3 defects)
Assess constraint requirements based on ligamentous integrity
Have backup implants available (increased constraint, hinges)

Exam Pearl

Australian Context: AOANJRR data shows cumulative revision rate 9.2% at 15 years for primary TKR, with infection (28%), aseptic loosening (28%), and instability (22%) as leading causes requiring revision. Re-revision rate after first revision is 12% at 5 years, 18% at 10 years.

Post-operative Protocol and Rehabilitation

Immediate Post-operative Care (0-48 Hours)

Multimodal analgesia: regional block (adductor canal block preferred over femoral to preserve quadriceps) plus oral paracetamol, NSAIDs if not contraindicated, oxycodone for breakthrough pain
VTE prophylaxis: LMWH (enoxaparin 40mg SC daily) or DOAC (rivaroxaban 10mg daily or apixaban 2.5mg BD) for 35 days - critical in revision given higher risk
Mechanical prophylaxis: TED stockings and pneumatic compression devices for 5-7 days
Cryotherapy for swelling and pain control
Drain removal at 24-48 hours if used (expect higher output than primary)
Wound inspection at 48 hours

Weight-Bearing and Mobility (Day 0-1 Onwards)

Standard revision: immediate weight-bearing as tolerated from day 0-1
Tibial tubercle osteotomy: protected weight-bearing with hinged brace for 6 weeks, then progress
Periprosthetic fracture: depends on fixation stability, may need protected weight-bearing
Early mobilization with physiotherapy twice daily
Expect slower progress than primary TKR
No evidence for CPM benefit

Inpatient Phase (Typically 5-7 Days)

Longer hospital stay than primary (3-5 days)
Intensive physiotherapy twice daily
Gait re-education with walking aids
Stairs practice before discharge
Pain control optimization
Discharge when mobile safely and pain controlled

Outpatient Rehabilitation (3-6 Months)

More intensive and prolonged than primary
Emphasis on ROM restoration (realistic goal 0-110° not 0-120°)
Quadriceps and hamstring strengthening critical
Gait re-education and balance training
Functional activities practice
Pool therapy beneficial (once wound healed 3-4 weeks)

Follow-up Schedule

Wound review at 2 weeks (remove staples/sutures)
Surgeon review at 6 weeks: clinical assessment, radiographs (AP, lateral, Merchant), assess alignment, component position, healing of TTO if performed
Then 3 months, 6 months, 12 months
Annual or biennial follow-up lifelong (higher re-revision rates than primary)

Return to Activities Timeline

Sedentary work: 8-12 weeks (longer than primary 6 weeks)
Active manual labor: 4-6 months
Driving (if right knee): when safe control 6-8 weeks
Low-impact activities: 6-9 months (swimming, cycling, walking)
Avoid high-impact activities: running, jumping sports accelerate wear and loosening

Expected Outcomes and Patient Counseling

Pain relief: 70-80% achieve good pain relief (vs 85-90% primary)
ROM: typically 0-110° (vs 0-120° primary)
Oxford Knee Score: 28-32 (vs 38-42 primary)
Patient satisfaction: 70-80% (vs 85-90% primary)
Ongoing pain without loosening: 15-25% (vs 10-20% primary)
Re-revision risk: 12% at 5 years, 18% at 10 years
Realistic expectations essential for satisfactory outcome
Functional outcomes inferior to primary TKR

Major Complications in Revision TKR

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 68-year-old woman presents 8 years after primary TKR with progressive medial knee pain, difficulty ascending stairs, and a sense of the knee 'giving way'. Radiographs show a well-fixed tibial component but progressive radiolucency around the femoral component with some subsidence. ESR is 12, CRP is 8. How would you approach this case?"

EXCEPTIONAL ANSWER

This case represents likely aseptic loosening of the femoral component with possible evolving instability, requiring systematic evaluation before proceeding to revision. My approach would be: First, exclude infection despite normal inflammatory markers - knee aspiration is mandatory (cell count with differential, culture, consider alpha-defensin). Even with ESR 12 and CRP 8, infection can present with low-grade markers, and this is the most important differential. Second, complete imaging assessment - weight-bearing AP and lateral radiographs to assess bone loss and component position, full-length alignment radiographs hip-to-ankle, and critically a CT scan with metal artifact reduction to assess 3D bone loss (AORI classification), femoral component rotation (malrotation can cause pain and instability), and plan reconstruction strategy. Third, clinical examination under anaesthesia to assess stability patterns - varus/valgus stress testing at 0° and 30° flexion, anteroposterior drawer at 90°, assess for flexion versus extension versus global instability. This guides constraint requirements. Fourth, classify bone defects using AORI classification from CT - likely Type 2B (uncontained defect one condyle given subsidence) requiring metal augments, or Type 2C (both condyles) requiring larger augments or trabecular metal cones. Fifth, assess ligamentous integrity after bone reconstruction planning - if MCL and LCL intact can use posterior-stabilized design, if one deficient need CCK constraint, if both deficient need rotating hinge. Sixth, surgical planning - medial parapatellar approach, likely need quadriceps snip given previous surgery, careful femoral component removal preserving bone stock, complete cement removal, reconstruct bone defects with augments (5-15mm wedges if Type 2B) or cones (if Type 2C), use press-fit stem 100-150mm bypassing defects, restore joint line within 5mm using 30mm medial epicondyle reference, correct femoral rotation using transepicondylar axis. Expected outcome: 82% 10-year survival for first revision, functional improvement in 70-80%, but patient counseling that ROM goals are 0-110° not 0-120°, ongoing pain possible in 15-25%, re-revision risk 12% at 5 years.

VIVA SCENARIOStandard

EXAMINER

"You are 45 minutes into a revision TKR for aseptic loosening. You have just removed the components and all cement. As you assess the bone defects, you note massive medial tibial plateau loss with the defect extending to the cortical rim, and both femoral condyles have significant uncontained defects with some involvement of the posterior cortex. The MCL feels slightly lax on valgus stress testing. How do you classify these defects and what is your reconstruction strategy?"

EXCEPTIONAL ANSWER

This represents extensive bone loss requiring systematic classification and reconstruction planning. The tibial defect is AORI Type 2B or 2C - medial plateau loss to cortical rim indicates uncontained defect, and if lateral plateau also involved it would be Type 2C. The femoral defects affecting both condyles with posterior cortex involvement are AORI Type 2C or possibly Type 3 if the defects compromise collateral ligament attachments. The MCL laxity suggests we are approaching Type 3 territory. My reconstruction strategy would be: First, for the tibia with Type 2C defect - I would use a trabecular metal cone. The cone provides structural support for massive metaphyseal defects. I would ream the tibial metaphyseal cavity to create a hemispherical defect matching the cone size (likely 35-45mm diameter), impact the cone press-fit into the defect to achieve primary stability, verify the cone is stable, then cement the modular tibial component to the superior flat surface of the cone. A press-fit stem of 100-150mm would bypass the metaphyseal defect and cone by at least 100mm into the diaphysis. Second, for the femur with Type 2C defects both condyles - I would likely also use trabecular metal cones bilaterally, or potentially large metal augments (15mm wedges or blocks) if the defects are not too extensive. If the posterior cortex involvement is severe, cones may be necessary. These would be press-fit into reamed metaphyseal defects, and the modular femoral component cemented to the cones. A long femoral stem (100-150mm) would bypass the cones into the diaphysis. Third, addressing the MCL laxity - this is critical for constraint selection. After the bone reconstruction with cones, I would reassess MCL and LCL integrity with trial components in place. If MCL remains Grade 2+ lax (5-10mm opening on valgus stress), I would increase constraint to a CCK (constrained condylar knee) which has a larger post and deeper femoral box providing varus-valgus stability. If both MCL and LCL are Grade 2-3+ lax, I would need a rotating hinge which provides varus-valgus stability while allowing some rotation. Fourth, ensuring adequate fixation for the increased constraint - with CCK or hinge, longer stems are required (150-200mm minimum) to distribute the increased interface stress to the diaphysis. Fifth, polyethylene thickness would likely be 15mm to compensate for the ligamentous laxity and bone loss. The hybrid fixation technique would involve press-fit stems, cemented cones (cement component to cone, not cone to bone), and cemented metaphyseal components. Realistic expectations with this extent of bone loss include 0-90° to 0-110° range of motion, 10-year survival approximately 70-75%, and higher re-revision risk.

VIVA SCENARIOStandard

EXAMINER

"During exposure for a revision TKR, you have performed a standard medial parapatellar arthrotomy. The knee is very stiff and scarred from previous surgery. As you attempt to evert the patella, you encounter significant resistance. Your assistant is applying lateral traction. What do you do at this moment, and what are your options to improve exposure safely?"

EXCEPTIONAL ANSWER

This is a critical decision point in revision TKR where the wrong action can lead to catastrophic patellar tendon avulsion. I would IMMEDIATELY stop any forced eversion - this is the single most important action. Patellar tendon avulsion is the most devastating complication in revision TKR with extremely poor outcomes (50-70% residual extensor lag, inability to straight-leg raise), and it is caused by forced patella eversion. My systematic approach would be: First, STOP all traction on the patella. Reassess the situation. Determine why the patella will not evert - is it tight medial and lateral gutters with scar tissue, is it tight superior tissue, is there patella baja from previous surgery, or is there quadriceps scarring? Second, perform additional medial and lateral releases using sharp dissection. Recreate the medial gutter by sharply releasing adhesions between the medial femoral condyle and the medial soft tissues. Recreate the lateral gutter similarly. Extend the medial arthrotomy proximally into the quadriceps tendon if needed. Take down all adhesions sharply to improve mobility. Third, flex the knee maximally and externally rotate the tibia while attempting gentle lateral subluxation (not eversion) of the patella. Sometimes with maximal flexion and rotation, you can displace the patella laterally enough to access the joint without true eversion. Fourth, if after these maneuvers the patella still will not subluxate without excessive tension on the patellar tendon, I would proceed with an extensile approach. The two main options are quadriceps snip (my preferred first choice) or tibial tubercle osteotomy. Fifth, quadriceps snip technique - I would make a 45-degree oblique incision from the superolateral pole of the patella extending proximally and laterally into the vastus lateralis muscle for 3-4cm. This effectively lengthens the extensor mechanism and allows patella eversion without tension on the patellar tendon. At closure, repair side-to-side with strong interrupted sutures (0 or 1 Vicryl or Ethibond), and full weight-bearing is allowed post-operatively with no restrictions. Sixth, if quadriceps snip is insufficient (rare), or if there is severe patella baja, I would perform a tibial tubercle osteotomy. Using an oscillating saw, create a tubercle osteotomy 5-6cm long, 1cm thick, hinge medially and reflect with the patellar tendon attached. At closure, reduce the tubercle and fix with two 4.5mm cortical screws. This requires protected weight-bearing for 6 weeks and a hinged brace. The key principle is: never force the patella eversion - identify and release tight structures, and if still unable to safely evert, perform extensile approach without hesitation. The morbidity of quadriceps snip or TTO is minor compared to the catastrophic outcome of patellar tendon avulsion.