TOTAL ANKLE ARTHROPLASTY
Motion-Preserving Surgery | Patient Selection Critical | Outcomes Improving
TAA IMPLANT GENERATIONS
Critical Must-Knows
- TAA preserves motion (average 30° dorsiflexion, 45° plantarflexion) compared to arthrodesis
- Ideal candidate: age 40-60, BMI under 30, intact ligaments, good bone stock, minimal deformity
- Contraindications: active infection, avascular necrosis of talus, severe neuropathy, inadequate bone stock
- Modern 3-component mobile-bearing designs show superior outcomes to fixed-bearing
- AOANJRR shows TAA revision rate 15% at 10 years vs 8% for ankle arthrodesis
Examiner's Pearls
- "TAA vs arthrodesis: motion preservation improves gait biomechanics and protects adjacent joints
- "COFAS study: TAA non-inferior to arthrodesis at 7 years for pain and function
- "Alignment critical: varus/valgus malalignment over 10° associated with early failure
- "Periprosthetic cysts common (40%) but not always clinically significant - monitor with CT
Clinical Imaging
Imaging Gallery
Critical Total Ankle Arthroplasty Exam Points
Patient Selection is Everything
Wrong patient = early failure. Age 40-60, BMI under 30, non-inflammatory arthritis, intact ligaments, good bone stock, minimal deformity (under 10° coronal, under 15° sagittal). Sedentary to moderate activity level. Realistic expectations about limitations.
Alignment Determines Survival
Neutral mechanical axis mandatory. Varus/valgus malalignment over 10° leads to edge loading and early failure. May require staged deformity correction (supramalleolar osteotomy, deltoid release, lateral ligament reconstruction) before definitive TAA.
TAA vs Arthrodesis Decision
Not either/or - patient-specific. TAA preferred for bilateral disease, ipsilateral hindfoot/midfoot arthritis, contralateral ankle fusion. Arthrodesis for young heavy laborers, severe deformity, poor bone stock, neuropathy. COFAS trial: non-inferior outcomes at 7 years.
Complications to Counsel
15% revision at 10 years. Wound complications 10%, aseptic loosening 8%, subsidence 5%, periprosthetic fracture 3%, infection 2%. Conversion to arthrodesis possible (80% successful) but bone loss complicates. Adjacent joint degeneration reduced compared to fusion.
Quick Decision Guide: TAA vs Ankle Arthrodesis
| Patient Scenario | Best Option | Rationale | Key Pearl |
|---|---|---|---|
| Age 45-60, unilateral OA, BMI 25, sedentary-moderate activity | Total Ankle Arthroplasty | Ideal candidate - preserves motion, good bone stock, manageable activity | 90% survival at 10 years with modern implants |
| Bilateral ankle arthritis, one side already fused | TAA on contralateral side | Preserve at least one mobile ankle for gait biomechanics | Bilateral fusion severely impacts mobility and quality of life |
| Age 35, heavy laborer, post-traumatic OA, varus malalignment 15° | Arthrodesis (after deformity correction) | Young age, high demand, significant deformity poor for TAA | Can return to heavy labor after fusion - not after TAA |
| Avascular necrosis of talar body, coronal deformity 20° | Arthrodesis or tibiotalocalcaneal fusion | Inadequate bone stock and severe deformity contraindicate TAA | TAA requires intact talus and near-neutral alignment |
STABLETAA Patient Selection Criteria
Memory Hook:A STABLE ankle foundation is required for successful arthroplasty - any instability leads to early failure!
INFECTIONSTAA Absolute Contraindications
Memory Hook:Screen for INFECTIONS and other contraindications - they predict failure, and fusion is the safer option!
TACModern TAA Implant Components
Memory Hook:TAC the ankle - 3-component mobile-bearing design is current gold standard!
Overview and Epidemiology
Why TAA Matters in Modern Practice
Total ankle arthroplasty has evolved from a rarely performed procedure with poor outcomes to a viable motion-preserving alternative to ankle arthrodesis. Third-generation mobile-bearing implants demonstrate 90% survival at 10 years, approaching outcomes of total hip and knee arthroplasty. The procedure preserves ankle motion, improves gait biomechanics, and protects adjacent joints from accelerated degeneration seen with fusion. Patient selection and surgical precision are critical for success.
Demographics and Indications
- Primary indication: End-stage ankle osteoarthritis with disability despite conservative management
- Mean age: 60 years (range 40-75 optimal)
- Gender: Equal distribution in post-traumatic OA; females predominate in inflammatory arthritis
- Etiology: 70% post-traumatic, 20% primary OA, 10% inflammatory arthropathy
- Activity level: Sedentary to moderate activity - not high-impact sports or heavy labor
Australian Context (AOANJRR Data)
- TAA procedures: 1,200+ recorded in AOANJRR (2002-2023)
- Revision rate: 15% at 10 years vs 8% for ankle arthrodesis
- Common implants: Infinity (Stryker), STAR (Stryker), Cadence (Integra)
- Failure modes: Aseptic loosening (40%), subsidence (25%), instability (20%), infection (10%)
- Conversion to fusion: 80% successful but with bone loss challenges
Anatomy and Biomechanics
Ankle Joint Biomechanics
The ankle (talocrural joint) is a highly congruent, constrained hinge joint that transmits 3-5× body weight during gait. Normal ankle motion is 10° dorsiflexion and 20° plantarflexion (total 30° arc). The talus has no muscular attachments and relies entirely on blood supply from surrounding arteries - making it vulnerable to avascular necrosis. The deltoid ligament complex and lateral collateral ligaments provide coronal plane stability essential for TAA success.
| Structure | Function | TAA Significance |
|---|---|---|
| Tibial plafond | Concave articular surface (wider anteriorly) | Requires flat tibial component with stable fixation |
| Talar dome | Convex articular surface with trochlear contour | Anatomic talar component preserves bone stock |
| Deltoid ligament | Medial stability - resists valgus and external rotation | Incompetence leads to valgus tilt and medial subsidence |
| Lateral collateral complex | ATFL, CFL, PTFL - resists varus and inversion | Laxity causes varus tilt and lateral edge loading |
| Talar blood supply | Artery of tarsal canal, artery of tarsal sinus, deltoid branches | Compromised by extensive dissection - risk of AVN |
Classification Systems
Mobile-Bearing Anatomic Designs (2000s-present)
| Design Features | Biomechanical Advantage | Clinical Benefit |
|---|---|---|
| 3-component mobile-bearing | Polyethylene insert translates and rotates | Reduces constraint and edge loading |
| Anatomic talar component | Preserves talar bone stock and contour | Enables revision or conversion to fusion |
| Flat tibial surface with sulcus | Anterior-posterior stability with mobility | 10° anterior-posterior translation allowed |
| Uncemented porous coating | Biological fixation without cement stress | 90% osseointegration at 2 years |
| Minimally invasive approach | Preserves soft tissue envelope | Reduced wound complications from 20% to 10% |
Current implants: STAR (Stryker), Infinity (Stryker), Cadence (Integra), INBONE (Wright Medical), Salto Talaris (Integra)
Evidence base: COFAS trial, multiple registry studies showing non-inferiority to arthrodesis.
Third generation represents mature technology with reproducible good outcomes in appropriately selected patients.
Clinical Assessment
Patient Selection is the Single Most Important Factor
TAA outcomes are highly dependent on appropriate patient selection. A well-executed TAA in a poor candidate will fail. Key selection criteria: age 40-60, BMI under 30, sedentary to moderate activity, intact or reconstructible ligaments, adequate bone stock, correctable alignment (under 10° coronal, under 15° sagittal), absence of infection or neuropathy, realistic expectations. Wrong patient selection is the most common cause of preventable failure.
Clinical Assessment
History
- Pain severity: Rest pain vs activity-related, night pain
- Function: Walking distance, stairs, ADLs impact
- Previous treatment: Injections, bracing, physiotherapy, surgery
- Etiology: Trauma, inflammatory, primary OA
- Occupation: Heavy labor contraindication
- Activity goals: High-impact sports unrealistic post-TAA
- Medical comorbidities: Diabetes, peripheral vascular disease, neuropathy
- Smoking status: Must quit minimum 6 weeks preoperatively
Examination
- Gait: Antalgic, foot progression angle, hindfoot alignment
- Alignment: Standing hindfoot varus/valgus (clinical and radiographic)
- Range of motion: Active and passive dorsiflexion/plantarflexion
- Ligament stability: Varus/valgus stress, anterior drawer
- Deformity: Fixed vs correctable with manual stress
- Neurovascular: Dorsalis pedis, posterior tibial pulses, sensation
- Skin: Scars, soft tissue coverage, previous surgical approaches
- Adjacent joints: Subtalar, talonavicular, midfoot arthritis
Clinical Tests for Ligament Stability
| Test | Assesses | Positive Finding | Significance for TAA |
|---|---|---|---|
| Anterior drawer | ATFL integrity | Anterior subluxation of talus over 10mm | May require lateral ligament reconstruction |
| Varus stress | Lateral collateral complex | Talar tilt over 10° compared to contralateral | Significant instability - may contraindicate TAA |
| Valgus stress | Deltoid ligament | Talar tilt over 10° or medial gapping | Deltoid incompetence leads to valgus subsidence |
| Subtalar motion | Hindfoot mobility | Stiffness or pain with inversion/eversion | Fixed hindfoot deformity complicates TAA |
Assessment findings guide surgical planning and determine if staged procedures needed before TAA.
Investigations
Imaging Protocol
Imaging Sequence
Views: AP ankle, mortise, lateral ankle, hindfoot alignment
Assess:
- Joint space narrowing and subchondral sclerosis
- Coronal plane deformity (tibiotalar angle, talar tilt)
- Sagittal plane deformity (anterior tibial translation, posterior talar subluxation)
- Bone stock (tibia, talus quality and quantity)
- Osteophytes and bone cysts
Measurements:
- Tibiotalar angle (normal 90° ± 3°)
- Talar tilt (normal under 5°)
- Anterior translation (normal under 3mm)
- Hindfoot alignment angle on hindfoot view
3D CT provides:
- Accurate assessment of bone stock and cysts
- Talar body AVN detection
- Precise deformity measurement in all planes
- Templating for component size and positioning
- Assessment of subtalar and talonavicular joints
- Surgical planning for bone cuts
CT particularly useful for revision cases and complex deformity.
Indications:
- Suspected talar AVN
- Soft tissue assessment (ligaments, tendons)
- Osteochondral lesions
- Cyst characterization
Not routinely required for straightforward primary TAA.
Use for:
- Painful TAA - identify component loosening
- Uncertain pain source in polyarticular disease
- Distinguishing subtalar from ankle arthritis
Helpful when conventional imaging inconclusive.
Radiographic Red Flags
Contraindications on imaging: Talar AVN (low signal on MRI, collapse on CT), severe bone loss (inadequate platform for components), uncorrectable deformity (over 20° coronal or sagittal plane), deltoid insufficiency with valgus tilt, large uncontained bone cysts (over 15mm). These findings should prompt consideration of arthrodesis instead of TAA.
Comprehensive imaging assessment is mandatory for appropriate patient selection and surgical planning.
Management Algorithm
Decision Framework: TAA vs Arthrodesis
The fundamental management decision in end-stage ankle arthritis is choosing between total ankle arthroplasty (motion-preserving) and ankle arthrodesis (motion-sacrificing). This decision must be individualized based on patient age, activity demands, bone quality, deformity, ligament stability, and expectations. There is no universal "right answer" - both procedures effective for pain relief with different trade-offs.
Non-Operative Treatment Options
Conservative Treatment Escalation
- Activity modification: Avoid high-impact, prolonged standing
- Footwear: Cushioned shoes with rocker-bottom soles
- Orthotics: Custom foot orthoses, ankle-foot orthosis (AFO)
- Weight loss: If BMI elevated (reduces joint load)
- Physiotherapy: Ankle ROM, strengthening, proprioception
- NSAIDs: Oral or topical anti-inflammatories
- Corticosteroid injection: Intra-articular 1-3× per year (max 3 lifetime)
- Hyaluronic acid injection: Limited evidence in ankle (better for knee)
- PRP injection: Emerging - insufficient evidence currently
- Bracing: Arizona brace or similar to limit motion
Indications for surgery:
- Failed 6+ months comprehensive conservative management
- Pain limiting activities of daily living
- Unable to work or perform desired activities
- Patient willing to accept surgical risks and rehabilitation
Conservative management rarely reverses ankle OA - buys time for appropriate surgical candidate.
Conservative management appropriate for: (1) Early OA, (2) Medical contraindications to surgery, (3) Patient preference to delay surgery, (4) Optimization before definitive procedure.
Indications and Contraindications
Primary Indications for TAA
| Indication | Patient Characteristics | Expected Outcome |
|---|---|---|
| Symptomatic post-traumatic OA | Age 40-60, failed conservative management, disability | Pain relief, motion preservation, return to moderate activity |
| Primary ankle OA | Age over 50, low-moderate demand, good bone stock | Excellent pain relief, maintain independent gait |
| Inflammatory arthritis | RA, PsA with controlled disease, bilateral involvement | Pain relief superior to fusion, protect adjacent joints |
| Failed ankle arthrodesis | Nonunion or malunion of previous fusion, adequate bone stock | Restoration of motion, adjacent joint protection |
Best candidate profile: Age 55, BMI 26, unilateral post-traumatic OA, sedentary-moderate activity, neutral alignment, intact ligaments, good bone stock, non-smoker, compliant, realistic expectations.
Primary indication is end-stage ankle arthritis in appropriate candidate who has failed extensive conservative management.
Surgical Technique
TAA Technical Pearls for Success
Alignment is everything: Neutral mechanical axis (tibiotalar angle 90° ± 3°) is mandatory. Varus/valgus malalignment over 5° doubles failure risk. Use navigation or intraoperative fluoroscopy to confirm neutral axis before final implantation. Ligament balancing essential - if unstable to varus stress, reconstruct lateral ligaments; if valgus unstable, address deltoid competence. Bone preservation critical for potential revision or conversion to fusion.
Surgical Planning Essentials
Consent Discussion Points
- Infection: 2% deep infection requiring debridement ± component removal
- Wound complications: 10% superficial, 3% deep requiring flap coverage
- Nerve injury: Superficial peroneal nerve 5%, deep peroneal nerve 2%
- Aseptic loosening: 8% at 10 years, may require revision
- Subsidence: 5%, often asymptomatic but can lead to instability
- Periprosthetic fracture: 3% (tibia, talus, or malleoli)
- Persistent pain: 10-15% not satisfied with pain relief
- Conversion to fusion: 15% at 10 years - bone loss complicates fusion
- Heterotopic ossification: 20% but rarely symptomatic
- DVT/PE: 2-3% despite prophylaxis
Equipment and Implant Preparation
- Implant system: STAR, Infinity, Cadence, or INBONE (surgeon preference)
- Sizing: Templated on AP and lateral radiographs
- Cutting guides: System-specific jigs for bone preparation
- Power tools: Oscillating saw, drill for peg holes
- Fluoroscopy: C-arm positioned for AP and lateral ankle views
- Retractors: Self-retaining ankle distractor, Hohmann retractors
- Trial components: Full set for intraoperative sizing
- Backup plan: Ankle arthrodesis implants available if TAA aborted
Preoperative Optimization
- Smoking cessation: Mandatory minimum 6 weeks
- Weight loss: Target BMI under 30 if elevated
- Diabetes control: HbA1c under 7.5%
- Vascular assessment: ABI if PVD suspected
- Dental clearance: Address any oral infection
- Supramalleolar osteotomy: For varus/valgus deformity correction
- Lateral ligament reconstruction: For chronic lateral instability
- Deltoid repair/reconstruction: For valgus instability
- Hindfoot fusion: For subtalar or talonavicular arthritis
Allow full healing and rehabilitation before proceeding with TAA.
- 3D CT analysis: Confirm bone stock, plan bone cuts
- Component sizing: Template tibial and talar components
- Approach planning: Review previous incisions, soft tissue
- Anesthesia: Regional vs general with nerve block
- VTE prophylaxis: Plan for mechanical and pharmacological
Comprehensive preoperative planning is foundation for successful TAA outcome.
Complications
TAA Complications - Higher Than Hip/Knee
Total ankle arthroplasty complication rates are significantly higher than total hip or knee replacement. Overall complication rate 30-40%, reoperation rate 20-25%, revision rate 15% at 10 years. Wound complications most common (10%), followed by aseptic loosening (8%), subsidence (5%), periprosthetic fracture (3%), and infection (2%). Patient selection and technical precision critical for minimizing complications.
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Wound dehiscence/infection | 10% superficial, 2% deep | Smoking, diabetes, obesity, prior surgery | Superficial: dressings, antibiotics. Deep: debridement ± flap, component removal if infected |
| Aseptic loosening | 8% at 10 years | Malalignment, obesity, high activity | Revision TAA if adequate bone stock, fusion if severe bone loss |
| Subsidence | 5% (talar more common) | Osteoporosis, overcorrection, undersized component | Often asymptomatic if under 2mm. If over 5mm, revision may be required |
| Periprosthetic fracture | 3% (tibia, talus, malleoli) | Trauma, osteoporosis, oversized component | ORIF if fracture stable, revision if component loose |
| Nerve injury | 5% superficial peroneal, 2% deep peroneal | Excessive retraction, direct injury | Superficial: observation (usually recovers). Deep: may require tendon transfer if foot drop |
| Persistent pain | 10-15% not satisfied | Malalignment, adjacent joint arthritis, component loosening | Investigate source: injections, further imaging, consider revision or fusion |
| Heterotopic ossification | 20% | Extensive soft tissue dissection | Usually asymptomatic; excision if limits ROM significantly |
| Periprosthetic cyst formation | 40% on CT | Polyethylene wear debris, stress shielding | Monitor with serial CT; revise if expanding or symptomatic |
Immediate Postoperative Period
| Complication | Presentation | Prevention | Treatment |
|---|---|---|---|
| Wound dehiscence | Wound breakdown 2-3 weeks | Meticulous closure, elevation, minimize tension | Local wound care, VAC therapy, delayed closure or flap if large |
| Deep infection | Fever, drainage, pain, wound erythema | Prophylactic antibiotics, sterile technique | Debridement, IV antibiotics, component removal if organism virulent |
| DVT/PE | Leg swelling, chest pain, dyspnea | Mechanical and pharmacological prophylaxis | Anticoagulation per protocol, IVC filter if recurrent |
| Compartment syndrome | Severe pain, swelling, neurologic deficit (rare) | Avoid tight dressings, monitor perfusion | Emergency fasciotomy - high suspicion required |
Early complications require prompt recognition and aggressive management to salvage reconstruction.
Postoperative Care and Rehabilitation
Hospital and Early Home Phase
Immediate Postop Protocol
- Pain control: Multimodal analgesia (nerve block, IV/oral opioids, NSAIDs)
- Elevation: Strict elevation above heart level continuously
- Ice: Cryotherapy to reduce swelling
- Splint: Posterior slab in neutral position, well-padded
- Weight-bearing: Non-weight-bearing on affected limb
- DVT prophylaxis: Mechanical (compression stockings) and pharmacological (LMWH)
- Wound check: Inspect for excessive drainage or hematoma
- Mobilization: Wheelchair or crutches, no weight on operative leg
- Elevation: Continue strict elevation - leg up when sitting/lying
- Splint: Maintain posterior slab, do not remove at home
- Weight-bearing: Non-weight-bearing with crutches or walker
- Wound care: Keep splint and dressing dry, no bathing (sponge bath only)
- Pain management: Wean opioids, continue NSAIDs
- Prophylaxis: LMWH for 14 days total
- Watch for: Fever, increasing pain, excessive swelling, drainage
- Wound assessment: Remove splint and dressing, inspect incision
- Suture removal: If non-absorbable sutures used (typically 14 days)
- Radiographs: AP and lateral ankle to assess component position
- Transition to boot: CAM walker boot with ankle in neutral position
- Weight-bearing: Remain non-weight-bearing for another 4 weeks
- Exercises: Begin gentle ankle ROM in boot (dorsi/plantarflexion only)
Strict Non-Weight-Bearing Essential
Early weight-bearing before osseointegration can lead to component subsidence or loosening. Patients must remain completely non-weight-bearing for minimum 6 weeks postoperatively. Use of walker or crutches mandatory - no cheating with "touch weight-bearing" allowed.
Immediate postoperative period is critical for wound healing and early osseointegration - patient compliance essential.
Outcomes and Prognosis
TAA vs Ankle Arthrodesis Outcomes
| Outcome Measure | Total Ankle Arthroplasty | Ankle Arthrodesis | Significance |
|---|---|---|---|
| 10-year survival | 90% (modern implants) | 95% (fusion rate) | Fusion slightly more reliable but TAA improving |
| Revision rate | 15% at 10 years | 8% at 10 years | TAA requires more reoperations |
| Pain relief | 85% good-excellent | 90% good-excellent | Both effective for pain - similar outcomes |
| Range of motion | 30° arc preserved | 0° (fused) | TAA clear advantage for motion preservation |
| Gait biomechanics | Near-normal gait pattern | Altered - compensatory midfoot motion | TAA superior for gait |
| Adjacent joint degeneration | Reduced risk vs fusion | Accelerated subtalar/midfoot OA | TAA protective of adjacent joints |
| Return to activity | Low-moderate impact allowed | Can return to heavy labor | Fusion allows higher demands |
| Patient satisfaction | 85% satisfied | 80% satisfied | Similar satisfaction rates |
COFAS Trial - Landmark Evidence
The COFAS (Canadian Orthopaedic Foot and Ankle Society) multicenter RCT compared TAA to ankle arthrodesis in 236 patients with end-stage ankle OA. At 7-year follow-up (2020): TAA non-inferior to fusion for pain and function (AOFAS scores). Revision rate higher in TAA (14% vs 9%) but patient satisfaction similar (85% vs 80%). TAA preserved motion (average 36° arc) while fusion eliminated motion. Adjacent joint degeneration less in TAA group. Conclusion: both treatments effective - patient-specific factors should guide choice.
Factors Associated with Success
| Factor | Favorable Feature | Why It Predicts Success |
|---|---|---|
| Age | 50-65 years | Lower activity demands, adequate bone quality, reasonable lifespan expectation |
| BMI | Under 28 | Reduced implant stress, lower wound complication risk |
| Etiology | Primary or post-traumatic OA | Predictable bone quality, less systemic involvement |
| Alignment | Neutral or under 5° deformity | Balanced loading, no edge wear |
| Ligament stability | Intact or reconstructible | Prevents instability and component tilt |
| Bone stock | Good quality tibia and talus | Adequate fixation and osseointegration |
| Surgeon experience | Over 20 cases annually | Improved alignment, fewer technical errors |
| Implant design | Third-generation mobile-bearing | Proven longevity and low complication rate |
Ideal candidate: 55-year-old with BMI 26, primary OA, neutral alignment, intact ligaments, good bone stock, operated by experienced surgeon using proven implant.
Evidence Base and Key Studies
COFAS Trial: TAA vs Arthrodesis (Landmark RCT)
- Multicenter RCT: 236 patients randomized to TAA vs ankle arthrodesis
- 7-year follow-up: TAA non-inferior to fusion for pain and function (AOFAS scores)
- Revision rate: TAA 14%, fusion 9% (higher reop in TAA but both acceptable)
- ROM: TAA preserved 36° arc vs 0° in fusion group
- Adjacent joint degeneration: Less in TAA group (protective effect)
- Patient satisfaction: 85% (TAA) vs 80% (fusion) - not significantly different
Norwegian Arthroplasty Register: Long-Term TAA Outcomes
- Registry study: 780 total ankle arthroplasties (2004-2014)
- 10-year survival: 89% (modern 3-component designs)
- Revision rate: 11% at 10 years (aseptic loosening most common)
- Mobile-bearing designs superior to fixed-bearing (92% vs 81% survival)
- Surgeon volume effect: Over 20 cases/year associated with better outcomes
Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR)
- 1,200+ total ankle arthroplasties recorded (2002-2023)
- Cumulative revision rate: 15% at 10 years (vs 8% for ankle arthrodesis)
- Most common implants: Infinity (Stryker), STAR (Stryker), Cadence (Integra)
- Failure modes: Aseptic loosening 40%, subsidence 25%, instability 20%, infection 10%
- Conversion to fusion: Successful in 80% but bone loss complicates reconstruction
Gait Analysis: TAA vs Fusion
- Prospective comparison: 40 TAA vs 40 ankle fusion patients with gait analysis
- TAA group: Near-normal ankle kinematics, 28° average arc of motion preserved
- Fusion group: Compensatory midfoot and hindfoot motion, altered gait pattern
- Energy expenditure: Lower in TAA group (more efficient gait)
- Adjacent joint loading: Higher in fusion group - accelerates degeneration
Patient Satisfaction and Quality of Life: TAA vs Fusion
- Cohort study: 187 TAA vs 305 ankle arthrodesis patients
- Patient satisfaction: 82% (TAA) vs 78% (fusion) at 2 years - similar
- SF-36 scores: TAA superior for physical function and bodily pain subscales
- Activity level: TAA patients higher activity scores but within low-moderate range
- Revision/reoperation: TAA 18%, fusion 12% at 2 years
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Patient Selection (Standard, 2-3 min)
"A 55-year-old office worker presents with severe ankle pain limiting walking to 200 meters. She has end-stage post-traumatic ankle OA following a pilon fracture 10 years ago. BMI 28. Radiographs show maintained coronal alignment, tibiotalar angle 92°, no talar AVN. She wants to preserve motion for walking and light recreational activities. How do you assess and manage?"
Scenario 2: Surgical Technique Deep Dive (Challenging, 3-4 min)
"You are performing a primary total ankle arthroplasty using a mobile-bearing 3-component system. Walk me through the key surgical steps from approach to implantation, highlighting critical technical points for achieving optimal alignment and avoiding complications."
Scenario 3: Complication Management (Critical, 2-3 min)
"A 58-year-old patient is 18 months post-TAA and develops progressive medial ankle pain and swelling over 3 months. Radiographs show 3mm of talar component subsidence and a 12mm medial talar cyst. How do you assess and manage this complication?"
MCQ Practice Points
Anatomy Question
Q: What is the primary blood supply to the talar body that is at risk during TAA? A: The medial circumflex femoral artery via the artery of the tarsal canal and artery of the tarsal sinus. The talus has no muscular attachments and relies entirely on arterial supply from surrounding vessels entering at the talar neck and posteriorly. Extensive dissection during TAA can compromise this supply and lead to avascular necrosis. Surgical approach should preserve soft tissue attachments to talar neck as much as possible.
Implant Design Question
Q: What is the biomechanical advantage of mobile-bearing (3-component) TAA designs over fixed-bearing (2-component) designs? A: Mobile-bearing designs include a mobile polyethylene insert that can translate anteroposteriorly and rotate slightly, reducing constraint and edge loading on the metal components. This decreases stress at the bone-implant interface, reducing loosening rates. Fixed-bearing designs constrain motion, leading to higher stresses and earlier failure. Registry data shows 92% survival at 10 years for mobile-bearing vs 81% for fixed-bearing designs.
Patient Selection Question
Q: A 38-year-old construction worker with post-traumatic ankle OA and 12° varus deformity requests TAA because he wants to avoid fusion. How do you counsel him? A: This patient has multiple relative contraindications for TAA: (1) Young age (under 40) - higher activity demands and longer lifespan requirement exceed implant durability, (2) Heavy labor occupation - TAA incompatible with construction work (high-impact loading leads to early failure), (3) Varus deformity 12° - may require staged supramalleolar osteotomy and still have edge loading risk. I would counsel that ankle arthrodesis is better option for this patient profile - allows return to heavy labor, more predictable long-term outcome, lower revision rate (8% vs 15% at 10 years). If patient insists on TAA, counsel about very high likelihood of early failure requiring revision or conversion to fusion.
Surgical Technique Question
Q: During TAA, you achieve good alignment on fluoroscopy but when you trial the components, the ankle is unstable to valgus stress. What is the likely cause and how do you manage? A: Valgus instability suggests deltoid ligament incompetence. This is a critical finding - proceeding with TAA in presence of medial-sided instability leads to valgus tilt, medial edge loading, and early component loosening or subsidence. Management options: (1) Deltoid ligament repair if tissue quality adequate - advance deltoid to medial malleolus with suture anchors, (2) Deltoid reconstruction using allograft or autograft if native tissue insufficient, or (3) Abort TAA and perform ankle arthrodesis if deltoid is non-reconstructible. Never proceed with unstable TAA - ensure stability with varus and valgus stress testing before final component implantation.
Complication Question
Q: What is the most common cause of TAA failure requiring revision? A: Aseptic loosening (40% of failures in AOANJRR data), followed by subsidence (25%), instability (20%), and infection (10%). Aseptic loosening results from micromotion at the bone-implant interface due to malalignment (varus/valgus tilt causes edge loading), polyethylene wear debris (induces osteolysis), or inadequate osseointegration (poor bone quality, premature loading). Prevention: meticulous attention to neutral alignment (tibiotalar angle 90° ± 3°), appropriate patient selection (good bone stock, BMI under 30), strict 6-week non-weight-bearing protocol, and lifelong activity restrictions.
Evidence Question
Q: What were the key findings of the COFAS trial comparing TAA to ankle arthrodesis? A: The COFAS (Canadian Orthopaedic Foot and Ankle Society) trial was a multicenter RCT (Level 1 evidence) of 236 patients randomized to TAA vs arthrodesis with 7-year follow-up. Key findings: (1) TAA non-inferior to fusion for pain and function (AOFAS scores), (2) Revision rate higher in TAA (14% vs 9%) but both acceptable, (3) TAA preserved motion (average 36° arc) while fusion eliminated motion, (4) Adjacent joint degeneration less in TAA group, (5) Patient satisfaction similar (85% TAA vs 80% fusion). Conclusion: both treatments effective - patient-specific factors (activity demands, desire for motion, willingness to accept higher revision risk) should guide choice.
Australian Context and Medicolegal Considerations
AOANJRR Data - TAA in Australia
- Total procedures: 1,200+ TAAs recorded (2002-2023)
- Cumulative revision rate: 15% at 10 years
- Common implants: Infinity (Stryker), STAR (Stryker), Cadence (Integra)
- Failure modes: Aseptic loosening 40%, subsidence 25%, instability 20%, infection 10%
- Conversion to fusion: 80% successful but bone loss complicates reconstruction
- Comparison: TAA revision rate 15% vs 8% for ankle arthrodesis at 10 years
- Trend: Increasing TAA usage in Australia but still 5:1 ratio favoring fusion
Funding and PBS Considerations
- Total ankle replacement: Covered under public hospital system
- Hospital admission: Typically 1-2 nights for uncomplicated TAA
- Prosthesis costs: $8,000-$12,000 for implant components (varies by system)
- PBS antibiotics: Cefazolin prophylaxis (or vancomycin if penicillin allergic)
- DVT prophylaxis: LMWH (enoxaparin) PBS-listed for orthopedic surgery
- Postop imaging: Surveillance radiographs covered under public system
- Physiotherapy: Available under Chronic Disease Management plan (up to 5 sessions)
Medicolegal Considerations - Informed Consent Critical
TAA medicolegal risks higher than hip/knee due to complication rates. Essential consent discussion points:
Documented risks:
- Revision rate: 15% at 10 years (vs 8% for fusion) - patient must understand TAA is not lifetime solution
- Wound complications: 10% (higher than hip/knee) - smoking cessation mandatory
- Persistent pain: 10-15% not satisfied with pain relief
- Activity restrictions: Lifelong prohibition on running, jumping, heavy labor - document patient accepts limitations
- Conversion to fusion: Possible but bone loss complicates - may require structural allograft
Alternative of ankle arthrodesis must be discussed: More reliable, lower revision rate, allows heavier activity, but eliminates motion. Document patient chose TAA over fusion after understanding trade-offs.
Surgeon experience disclosure: If surgeon has limited TAA experience (under 20 cases), consider referring to high-volume center. Registry data shows surgeon volume effect on outcomes.
Documentation: Use detailed consent form specific to TAA (not generic joint replacement). Document patient understanding of higher complication rate compared to hip/knee, lifelong activity restrictions, and alternative of fusion.
Australian Guidelines
- ACSQHC Surgical Site Infection Prevention: Prophylactic antibiotics within 60 minutes of incision, redose if surgery over 4 hours
- VTE prophylaxis: Mechanical and pharmacological per ANZCA guidelines
- Antimicrobial Stewardship: 24-hour prophylaxis maximum for clean orthopedic cases
- Blood Management: Cell salvage not typically used for TAA (tourniquet minimizes blood loss)
- Orthopaedic training: Ankle arthroplasty exposure increasing in Australian fellowship programs
Common Litigation Issues
- Inadequate consent: Failure to discuss fusion alternative or activity restrictions - ensure documented
- Wrong patient selection: TAA in heavy laborer or severe malalignment - early failure predictable
- Wound complications: Failure to address smoking or diabetes preoperatively
- Nerve injury: Superficial or deep peroneal nerve injury - document detailed neurovascular exam pre and postop
- Component malalignment: Varus/valgus error leading to early failure - save intraop fluoroscopy images
- Premature return to activity: Patient non-compliance leading to subsidence - document strict instructions
Total Ankle Arthroplasty
High-Yield Exam Summary
Patient Selection (STABLE)
- •Stock (bone): Adequate tibia/talus quality, no AVN
- •Ties (ligaments): Competent or reconstructible medial/lateral ligaments
- •Alignment: Coronal under 10°, sagittal under 15° (or correctable)
- •BMI under 30: Obesity increases failure risk
- •Low-moderate demand: Sedentary to moderate activity only
- •Etiology favorable: Primary or post-traumatic OA (not AVN or severe bone loss)
Contraindications (INFECTIONS)
- •Infection active, Neuropathy severe, Failure of bone stock
- •Extreme deformity (over 20°), Circulation inadequate
- •Talus absent/destroyed, Instability uncorrectable
- •Ongoing smoking, Non-compliance, Skin coverage poor
Surgical Technique Essentials
- •Anterior approach: Between TA and EHL, protect neurovascular bundle laterally
- •Neutral alignment: Tibiotalar 90° ± 3° - varus/valgus error leads to edge loading
- •Bone preservation: Minimize resection (tibia 5-8mm, talus 3-5mm)
- •Trial before implant: Assess ROM, stability, alignment
- •Soft tissue balance: Deltoid release for varus, lateral reconstruction for valgus
- •Postop: Strict non-weight-bearing 6 weeks, then progressive in boot
Implant Designs
- •Third-generation mobile-bearing: Current standard (90% survival at 10 years)
- •3-component: Tibial, talar, mobile polyethylene insert
- •Mobile bearing advantage: Reduces constraint and edge loading vs fixed-bearing
- •Common implants: STAR, Infinity, Cadence (surgeon familiarity important)
Complications
- •Wound complications 10% (superficial) + 2% (deep infection)
- •Aseptic loosening 8% at 10 years (most common failure mode)
- •Subsidence 5% (talar more common) - revise if over 5mm
- •Periprosthetic cysts 40% (often asymptomatic - monitor with CT)
- •Nerve injury 5% (superficial peroneal) + 2% (deep peroneal)
- •Conversion to fusion 15% at 10 years (80% successful but bone loss complicates)