Ankle Arthrodesis

Primary Indications

Absolute Indications

• End-stage tibiotalar osteoarthritis (primary, post-traumatic, or rheumatoid) with failed conservative management (minimum 3–6 months of NSAIDs, physiotherapy, intra-articular injection, ankle-foot orthosis)
• Tibiotalar OA following failed ORIF with retained or removed metalwork and joint destruction
• Charcot neuroarthropathy of the ankle with instability or ulcer risk
• Ankle instability with severe arthritis or after failed ligamentous reconstruction with arthritic change
• Failed total ankle replacement with inadequate bone stock for revision TAR

Relative Indications

• Avascular necrosis of the talus with joint involvement
• Septic arthritis with residual tibiotalar destruction (staged: eradicate infection, then fuse)
• Ankle tumour resection requiring reconstruction with fusion
• Severe coronal or sagittal deformity not correctable by realignment osteotomy alone

Contraindications

• Active deep infection (relative — staged approach possible)
• Severe ipsilateral hindfoot or midfoot arthritis limiting compensatory motion
• Contralateral lower limb amputation (fusion prevents compensatory gait adaptation)
• Unrealistic patient expectations regarding functional outcome

Optimal Fusion Position

The four-point position is non-negotiable and must be confirmed fluoroscopically:

Sagittal plane — 0° (neutral): Neutral dorsiflexion aligns ankle joint reaction force through the tibia. Even 5° of equinus shifts loading to the forefoot, increases knee flexion demand, and is perceived as a functional leg length shortening.

Coronal plane — 5° valgus: Slight hindfoot valgus maintains the subtalar axis of compensation. Varus fusion is poorly tolerated, causing lateral border overload, peroneal tendon stress, and sural nerve symptoms.

Axial rotation — 5–10° external rotation: Must match the contralateral limb. Assessed clinically by comparing the second-toe axis. Excess external rotation causes compensatory knee external rotation stress; internal rotation causes patellofemoral pain.

Sagittal translation — mild posterior shift: Positioning the talus slightly posterior under the tibia shortens the anterior lever arm and reduces stress on the midfoot during terminal stance. Anterior talar subluxation increases midfoot loading significantly.

Key Evidence

Arthroscopic vs Open Arthrodesis

Townshend et al. (2013): Multicentre comparative case series of 60 patients (30 arthroscopic, 30 open) followed for 2 years. The primary outcome (Ankle Osteoarthritis Scale) and SF-36 physical component improved significantly in both groups; improvement was significantly greater and hospital stay shorter in the arthroscopic group, while complications, surgical time and radiographic alignment were similar.

Zvijac et al. (2002): Retrospective series of 21 arthroscopically assisted fusions; 20 of 21 (95%) united at a mean of 8.9 weeks. The single failure had extensive talar avascular necrosis (approximately 50% of the talus), reinforcing AVN and deformity as relative contraindications to the arthroscopic technique.

Ogilvie-Harris et al. (1993): 19 arthroscopically assisted fusions in ankles with minimal/no deformity, fixed with three percutaneous cannulated screws; 17 of 19 united (2 non-unions), with excellent or good results in 16. Established arthroscopic technique as viable for non-deformed arthritic ankles.

Current Recommendation: Arthroscopic arthrodesis is preferred for end-stage ankle OA without significant deformity (generally less than 15°) or talar AVN. Open technique is required for major deformity correction, Charcot arthropathy, bone loss requiring graft, or revision procedures.

Long-term Outcomes After Fusion

Coester et al. (2001): 23 patients with isolated post-traumatic ankle arthrodesis followed a mean of 22 years (longest follow-up reported). Ipsilateral subtalar, talonavicular, calcaneocuboid, naviculocuneiform, tarsometatarsal and first MTP arthritis were all significantly more severe than the contralateral side (each p less than 0.01), with significantly worse activity limitation, pain and disability — establishing accelerated adjacent-joint degeneration as the long-term cost of fusion. The knee was not significantly affected.

Hendrickx et al. (2011): Single-centre retrospective study of 60 patients (66 ankles) fused with a two-incision, three-screw technique. Primary union rate 91% (six required re-arthrodesis), mean AOFAS 67 and 91% satisfaction at a mean 9-year follow-up; significant radiographic progression of arthritis was seen in all adjacent joints.

Tibiotalar Joint Anatomy

Bony Anatomy

• Tibial plafond: The distal tibial articular surface, slightly wider anteriorly. The mechanical axis of the tibia is approximately 3° of valgus relative to the anatomical axis, informing fusion position.
• Talar dome: Wider anteriorly (trapezoidal shape), which is why the talar dome is unconstrained in plantarflexion — clinically relevant to joint preparation techniques.
• Medial malleolus: Posterior colliculus (deep deltoid attachment) and anterior colliculus (superficial deltoid); preserve or osteotomise for medial approach exposure.
• Lateral malleolus: Extends 1 cm more distal than medial malleolus; may be preserved (fibula-sparing lateral approach) or removed (transfibular approach) depending on deformity and fixation plan.

Anterior Ankle Relations

• Anterior interval: Extensor hallucis longus (EHL) medially, extensor digitorum longus (EDL) laterally define the safe anterior interval.
• Dorsalis pedis artery: Lies in the EHL–EDL interval. Must be identified, mobilised, and retracted medially with EHL for anterior approach.
• Deep peroneal nerve: Runs immediately lateral to DP artery; vulnerable to both retraction and screw placement through anterior plate.
• Anterior ankle capsule: Thin structure reflected with soft-tissue flaps; the fat pad in the anterior gutter must be removed to access joint surfaces fully.

Lateral Ankle Relations

• Superficial peroneal nerve: Anterolateral branch pierces deep fascia 10–12 cm above lateral malleolus; dorsal cutaneous branches cross the anterolateral portal site — tense the nerve with plantarflexion and inversion before marking portals.
• Sural nerve and short saphenous vein: Run posterior to the fibula; at risk with posterolateral portal placement and during sinus tarsi approach.
• Peroneal tendons: Run in the peroneal groove posterior to lateral malleolus; retracted or protected during lateral approach.

Medial Ankle Relations

• Great saphenous vein and saphenous nerve: Anterior to medial malleolus; at risk with anteromedial portal and medial malleolus osteotomy.
• Posterior tibial neurovascular bundle: Deep to flexor retinaculum posterior to medial malleolus; not at risk from standard approaches but vulnerable in excessive medial dissection.

Subtalar Joint

• Lies immediately inferior to the tibiotalar joint, separated by the interosseous talocalcaneal ligament in the sinus tarsi. Must be assessed pre-operatively; concomitant symptomatic subtalar arthritis may require tibiotalocalcaneal fusion rather than isolated ankle fusion.

Positioning and Preparation

Patient Position: Supine with a sandbag under the ipsilateral hip to bring the foot into a neutral rotational alignment. A padded tourniquet applied to the thigh. Image intensifier positioned on the contralateral side for unobstructed AP and lateral views.

Pre-operative Landmarks: Mark the course of the superficial peroneal nerve (plantarflexion and inversion test), dorsalis pedis pulse, and the medial and lateral malleoli before tourniquet inflation.

Tourniquet: Elevated to 100 mmHg above systolic pressure. Deflate before closure to ensure haemostasis, especially before anterior plate application.

Arthroscopic Ankle Arthrodesis

Step 1: Portal Placement

Anteromedial portal: Just medial to the tibialis anterior tendon, approximately 1 cm above the joint line. Use an 18-gauge needle first to confirm intra-articular position and aspirate joint fluid. Skin incision only, blunt dissection to capsule, introduce 4.0 mm 30° arthroscope.

Anterolateral portal: Lateral to the EHL tendon, at the same joint-line level. Create under direct arthroscopic vision using transillumination. This working portal receives the shaver and burr. Key safety: dorsiflex the foot to open the anterior compartment; plantarflexion and inversion before portal marking will reveal the superficial peroneal nerve.

Posterolateral portal (accessory): 1 cm above the tip of the fibula, posterior to it. Must avoid sural nerve posteriorly. Used for posterior gutter débridement.

Step 2: Cartilage Débridement

Systematic progression using a 4.0 mm full-radius shaver then 4.0 mm abrader burr:

• Anterior gutter — remove all fibrotic synovium, anterior osteophytes with 4.0 mm burr
• Central tibial plafond — débride to bleeding cancellous bone in systematic medial-to-lateral sweeps
• Medial and lateral gutters
• Posterior tibial surface — requires posterolateral portal or appropriate curved instruments
• Talar dome — full-surface débridement to cancellous bleeding bone. Complete removal of all remaining cartilage is mandatory for union

Technical Pearl: A 2.0 mm drill or Kirschner wire used to drill multiple 5 mm-deep holes in the subchondral plate (fish-scale or Russian technique) increases bleeding surface area and augments fusion potential.

Step 3: Positional Assessment and Provisional Fixation

Confirm fusion position using fluoroscopy before final fixation:

• AP view: 5° valgus confirmed by alignment of tibial and talar axes, medial clear space closed
• Lateral view: Neutral dorsiflexion (anterior cortex of tibia and anterior talar neck in line), mild posterior translation of talus

Provisional fixation: Two 2.0 mm K-wires placed percutaneously across tibiotalar joint to hold position during definitive screw insertion. Confirm position with image intensifier.

Step 4: Screw Fixation

Standard two-screw construct (most commonly used):

Medial malleolar screw: Start point on medial face of medial malleolus, directed laterally and slightly anteriorly into talar body. 6.5 mm or 7.3 mm cannulated partially threaded screw. The thread must cross the joint line fully and purchase the talar body for compression.

Lateral malleolar screw: Start point on lateral face of fibula at the level of the tibial plafond (or through distal tibia anterolaterally), directed medially across the joint into the talar body or neck. Avoid the subtalar joint.

Optional third anterior screw: From the anterior distal tibia, directed posteriorly across the joint — provides rotational control and anti-corrosion fixation. Most useful in revision or high-demand patients.

Final fluoroscopy: AP and lateral views to confirm screw position, compression, and correct fusion alignment.

Open Ankle Arthrodesis — Anterior Approach

Step 1: Incision

Longitudinal incision 10–12 cm centred over the anterior ankle, lateral to the tibialis anterior tendon. Deepen through deep fascia in the EHL–TA interval. Identify and protect the dorsalis pedis artery and deep peroneal nerve immediately lateral to EHL — mobilise and retract medially. Divide the ankle capsule transversely, elevate anterior periosteum.

Step 2: Joint Preparation

Resect tibial plafond and talar dome with a sagittal saw using a flat cut technique, removing sufficient bone to achieve flat apposing surfaces. Retain as much bone length as possible — over-resection shortens the limb and increases strain on adjacent joints. Alternatively, use the cup-and-cone reamer technique to preserve contoured surfaces and maximise contact area.

Critical: Use a femoral distractor or large laminar spreader to open the joint for posterior surface preparation. The posterior tibial margin must be débrided and will not be reached without adequate distraction.

Step 3: Deformity Correction

Correct coronal and sagittal deformities by differential bone resection before fixation. Wedge resections of tibial plafond or talar dome allow correction of varus/valgus and equinus deformities.

Fibula osteotomy (transfibular approach option): The distal fibula is osteotomised 5–7 cm above the joint line, reflected distally on its soft tissue attachments, and used as onlay bone graft after joint preparation. This extensile approach gives excellent joint visualisation for large deformities.

Step 4: Fixation

Compression screw construct: Two crossed 6.5–7.3 mm partially threaded cannulated screws from medial and lateral malleoli as described above. For revision, deformity, or Charcot cases, supplementary fixation options include:

• Anterior blade plate or locking plate: Applied to anterior tibia after neurovascular bundle retraction; provides multiplanar stability and is preferred for Charcot arthropathy or bone loss scenarios
• Retrograde intramedullary nail (tibiotalocalcaneal nail): Indicated for combined ankle and subtalar fusion, severe Charcot, revision, or elderly osteoporotic bone — provides axial compression and rotational stability

Step 5: Bone Grafting

Autograft (iliac crest or local cancellous bone from reamed cavities) packed into the joint space where gaps exist. Consider demineralised bone matrix or synthetic graft to augment. Bone graft is mandatory in revision cases and avascular necrosis scenarios.

Step 6: Closure

Copious irrigation. Deep fascial layer closed without tension. Subcutaneous and skin closure over suction drain. In high-risk wound patients, consider leaving deep fascia open or performing delayed primary closure at 48–72 hours.

Specific Management Pearls

Managing Non-Union

• CT scan mandatory — plain radiographs underestimate non-union. Look for cortical bridging in at least three cortices on thin-cut CT to declare union.
• Check for infection as a cause: ESR, CRP, white cell count; aspiration if hardware loosening evident
• Modifiable risk factors must be addressed before revision: enforce smoking cessation, optimise glycaemic control (HbA1c below 8%), address nutritional deficiencies
• Revision fixation options: compression plating preferred for adequate bone stock; retrograde tibiotalocalcaneal nail for bone deficiency or Charcot

Arthrodesis vs Total Ankle Replacement

This is a high-yield viva topic — see VivaScenario 3 for full discussion. Key differentiating factors:

• Fusion is more durable, more predictable, and indicated for bone loss, Charcot, severe deformity, infection history, and high-demand activities
• TAR preserves motion and protects adjacent joints but requires better bone stock, intact ligaments, near-normal alignment, and lower activity demand
• Modern TAR survival is approximately 85–90% at 7–10 years (National Joint Registry and contemporary series such as Clough & Ring 2021), approaching hip and knee replacement survival at equivalent time points; Daniels (COFAS 2014) reported comparable patient-reported outcomes to fusion with higher reoperation rates

Immediate Post-operative Phase (0–2 Weeks)

Immobilisation

• Well-padded below-knee backslab or split cast applied in theatre
• Elevation above heart level for first 48–72 hours — critical to reduce swelling and wound tension
• Non-weight-bearing strictly; mobilise with crutches or frame
• Wound check at 48–72 hours; drain removed at 24–48 hours

Pain Management

• Multimodal analgesia: paracetamol, NSAIDs (use with caution in Charcot / renal impairment), opioids for breakthrough
• Popliteal nerve block gives 12–24 hours of effective post-operative analgesia — reduces early opioid requirements
• Neuropathic pain (burning, electric character): gabapentin or pregabalin from day 1 in patients with pre-existing neuropathy

Early Monitoring

• Neurological check (sensation lateral foot — sural nerve; dorsum — superficial peroneal nerve) day 1
• Vascular check — capillary refill, DP pulse (Doppler if concern)
• Wound inspection at 2 weeks; suture removal

Intermediate Phase (2–6 Weeks)

Casting and Weight-Bearing

• Convert from backslab to circumferential below-knee cast at 2-week wound check
• Continue strict non-weight-bearing for 6 weeks in most patients
• Exception: open technique with plate or retrograde nail in Charcot patients — protected weight-bearing in cast or total contact cast from week 2 may be considered to prevent osteoporosis and pressure ulceration

Arthroscopic Versus Open Protocol

• Arthroscopic technique: progressive weight-bearing in removable boot from 6 weeks with radiographic evidence of bridging
• Open technique / Charcot: continue non-weight-bearing to 8–10 weeks before progressive loading

Progressive Weight-Bearing Phase (6–12 Weeks)

Weight-Bearing Advancement

• Week 6: Begin protected weight-bearing in removable CAM boot if radiographs show early bridging
• Week 8–10: Progress to full weight-bearing in boot, discard crutches
• Week 10–12: Transition to supportive footwear with custom orthosis for first 6 months

Physiotherapy

• Ankle is fused — formal ankle physiotherapy not required; however hip and knee strengthening essential to compensate
• Balance and proprioception rehabilitation with eyes-closed single-leg stance
• Gait retraining: antalgic gait correction, hip extension strengthening for push-off substitution

Long-term Follow-up and Union Assessment

Radiographic Union Criteria

• Minimum three cortices bridged on plain radiographs
• CT scan at 12 weeks if plain radiograph appearance equivocal — gold standard for union assessment
• Clinically: no pain on tibiotalar stress testing and no tenderness at fusion site

Follow-up Schedule

• 2 weeks: wound check, suture removal, cast change
• 6 weeks: radiographs, weight-bearing decision
• 12 weeks: CT if union uncertain, boot-to-shoe transition
• 6 months: final radiographic union confirmation, custom orthosis review
• 12 months: assess adjacent joint symptoms (subtalar, talonavicular)
• Annual: screen for progressive adjacent joint arthritis

Return to Activity

• Driving: 12 weeks minimum (right ankle fusion patients should be assessed individually for brake reaction time)
• Sedentary work: 6–8 weeks
• Light manual work: 12–16 weeks
• Heavy manual labour: 6 months minimum
• Low-impact sport (cycling, swimming): 4–6 months
• Running and high-impact sport: generally not recommended after bilateral fusion; unilateral fusion may allow jogging at 12 months

Warning Signs Requiring Urgent Review

• Increasing pain and swelling beyond expected post-operative course (deep infection)
• Progressive wound breakdown or discharge
• Worsening neurological symptoms (compartment syndrome, nerve injury)
• Loss of pin/screw fixation (hardware failure on radiograph)