Tibiotalocalcaneal Arthrodesis (Hindfoot Nail)

Surgical Indications

Primary Indications for TTC Arthrodesis

• Combined tibiotalar AND subtalar arthritis — most common indication; isolated ankle or subtalar fusion will not address the patient's pain
• Failed total ankle replacement (TAR) with subtalar arthritis, talar component subsidence, or aseptic loosening where revision TAR is not feasible
• Charcot neuroarthropathy (Eichenholtz stage 2-3) of the hindfoot with instability, deformity, or ulceration — a load-sharing construct that bypasses both joints
• Avascular necrosis of the talus with collapse — either preserve the talus with structural graft bridging to the calcaneus, or perform talectomy with tibiocalcaneal arthrodesis
• Severe hindfoot deformity (post-traumatic varus, equinocavovarus, equinus contracture) that requires correction across both joints
• Failed prior ankle or subtalar arthrodesis with nonunion, malunion, or symptomatic adjacent joint disease
• Tumour resection of the talus requiring intercalary reconstruction

Relative Indications

• Salvage after failed TAR in a lower-demand patient where conversion to TTC nail is the definitive solution
• Talar body fracture with severe comminution not amenable to ORIF
• Severe post-traumatic hindfoot bone loss requiring bridging graft

Contraindications

Absolute:

• Active infection (osteomyelitis of the tibia, talus, or calcaneus) — must be cleared first with staged debridement
• Uncorrectable vascular insufficiency — check ankle-brachial pressure index; revascularise first
• Severe peripheral neuropathy with open ulceration through the planned incision — heal the wound first

Relative:

• Young, high-demand patient — consider staged ankle and subtalar fusion to preserve whatever hindfoot motion is possible
• Active Charcot with severe bone fragmentation (Brodsky 3B) — consider external fixation or staged management
• Smoker with poor healing — counsel about nonunion risk (up to 2-3x higher); consider bone graft adjuncts
• Severe osteoporosis (T-score less than minus 3) — consider plate-augmented construct or external fixation

Evidence for Operative Treatment

Outcomes of Primary TTC Arthrodesis

• A systematic review of retrograde hindfoot nailing for combined hindfoot pathology reports union rates of 70-90% in primary cases with modern compression/angle-stable nail designs
• Patient satisfaction exceeds 75% in most series, with substantial pain relief and improved function; gait analysis shows near-normal ankle power but loss of hindfoot inversion/eversion
• AOFAS scores improve from a mean of 30-40 preoperatively to 70-80 postoperatively in most series
• Time to union: 3-6 months in primary cases; up to 9-12 months in Charcot, AVN, and revision

Failed Total Ankle Replacement

• A meta-analysis of TAR failures converted to TTC nail reports union rates of 75-85%, with patient satisfaction approaching that of primary TTC
• Tibiotalocalcaneal nail is now considered the gold standard salvage for failed TAR with subtalar arthritis
• Bone loss from the explanted talar component often requires structural graft or bone substitute augmentation

Charcot Neuroarthropathy

• A multi-centre review of TTC nailing for Charcot reports union rates of 50-70%, with limb salvage rates exceeding 85% at 5 years
• Rocker-bottom deformity correction with the nail permits ulcer healing in 70-90% of patients
• Solid intramedullary constructs have largely replaced external fixation for Charcot hindfoot reconstruction
• A long hindfoot nail extending to the tibial metaphysis is preferred for stable load-sharing

Avascular Necrosis of the Talus

• AVN is a high-risk subset: union rates 50-70% in published series, lower than primary TTC
• Structural bone graft (autogenous iliac crest tricortical or femoral head allograft) bridging the tibial plafond to the calcaneus is often required
• Talectomy with tibiocalcaneal arthrodesis is a salvage option for severe AVN with collapse

Key Evidence

Hindfoot Osteology and Joints

Tibiotalar (Ankle) Joint

• Formed by the distal tibial plafond and the medial/lateral malleoli articulating with the talar dome
• Mortise-shaped articulation with primary motion in sagittal plane (dorsiflexion-plantarflexion)
• The anterior capsule is thin and accessible; the posterior capsule is thicker and requires capsulotomy or release for deformity correction

Subtalar (Talocalcaneal) Joint

• Comprises anterior, middle, and posterior facets; the posterior facet is the principal weight-bearing surface
• Motion is primarily inversion-eversion with the axis running obliquely from posteromedial to anterolateral
• The sinus tarsi is the soft tissue corridor from lateral to medial between the talar neck and the posterior facet of the calcaneus — the key surgical approach to the subtalar joint

Hindfoot Axis and Alignment

• Mechanical axis of the tibia should pass through the central hindfoot on both AP and lateral views
• Hindfoot valgus of 5 degrees is the goal — small degrees of valgus are well tolerated; varus is not
• Tibial torsion and foot progression angle are preserved by careful nail entry and rotational control

Neurovascular Anatomy Around the Plantar Entry Portal

Lateral Plantar Neurovascular Bundle

• Arises from the posterior tibial neurovascular bundle beneath the flexor retinaculum
• Courses from the medial heel pad distally and laterally, deep to the abductor hallucis and superficial to the flexor digitorum brevis
• Passes laterally toward the base of the fifth metatarsal
• Lies MEDIAL to the nail entry trajectory if the entry incision is placed slightly lateral to the plantar midline

Medial Plantar Neurovascular Bundle

• Runs from the medial heel along the medial border of the plantar fascia
• Generally spared by a lateralised entry incision
• At risk with extensive medial dissection for tibial preparation or graft harvest
• Injury produces numbness of the medial sole and the great toe

Posterior Tibial Neurovascular Bundle

• Lies posterior to the medial malleolus, beneath the flexor retinaculum (tarsal tunnel)
• Branches into medial and lateral plantar nerves and vessels within the tarsal tunnel
• In a posterior approach to the ankle and subtalar joint, retractors placed posteriorly must be anterior to the bundle
• In an anterior or lateral approach, this bundle is at less direct risk

Sural Nerve

• Runs along the lateral border of the foot from posterior calf to the base of the fifth metatarsal
• At risk in a lateral transfibular or sinus tarsi approach
• Injury produces numbness of the lateral foot; neuroma can be problematic

Saphenous Nerve and Vein

• Run along the medial side of the foot anterior to the medial malleolus
• At risk with anterior medial portal placement for ankle arthroscopy
• Generally spared in the standard TTC approach

Muscular and Tendinous Anatomy

Achilles Tendon

• The principal plantarflexor of the ankle
• Often contracted in long-standing equinus deformity and Charcot
• Lengthening (percutaneous triple hemisection or open Z-lengthening) is frequently required to achieve a plantigrade foot
• TAL may be performed as the first step before joint preparation

Flexor Hallucis Longus

• Runs in a fibro-osseous tunnel along the posteromedial talus and inferior to the sustentaculum tali
• Passes between the medial and lateral tubercles of the posterior talar process (Vincent's syndrome area)
• At risk in a posterolateral approach to the subtalar joint
• In a posterior approach, FHL must be retracted medially to access the posterior facet

Peroneal Tendons

• Peroneus longus and brevis pass posterior to the lateral malleolus
• Peroneus longus runs beneath the cuboid; peroneus brevis inserts on the base of the fifth metatarsal
• At risk in a lateral transfibular or sinus tarsi approach — identify and protect

Posterior Tibial Tendon

• Runs posterior to the medial malleolus
• Insertion on the navicular tuberosity (main) and the plantar surfaces of the midfoot (accessory slips)
• Sacrificed in some salvage procedures; reconstruct or tenodese when possible

Bone Graft Harvest Sites

Ipsilateral Proximal Tibia

• Most convenient harvest site during the same procedure
• Reamings from the tibial preparation provide abundant cancellous graft
• Minimal additional morbidity

Iliac Crest

• Tricortical structural graft for AVN, severe bone loss, or revision
• Higher donor site morbidity (pain, haematoma, infection) — counsel patient
• Anterior iliac crest preferred (less nerve injury risk than posterior)

Femoral Head Allograft

• Off-the-shelf structural graft for AVN, bone loss, or Charcot
• No donor site morbidity; risk of disease transmission essentially zero with modern screening
• Incorporation is slower than autograft

Preoperative Planning

Clinical assessment:

• Examine the foot in stance and during gait: identify the apex of deformity, the status of the skin, the presence of ulceration, and the integrity of the soft tissues
• Check the contralateral foot for reference alignment
• Assess the Achilles for contracture — Silfverskiold test (knee flexed and extended) to determine whether gastrocnemius recession alone is sufficient or a formal Achilles lengthening is required
• Document neurovascular status: posterior tibial and dorsalis pedis pulses, capillary refill, sensation
• In diabetics: check HbA1c, fasting glucose, nutritional status (albumin greater than 30 g/L, lymphocytes greater than 1500), and screen for Charcot with bilateral weight-bearing foot and ankle radiographs

Imaging:

• Weight-bearing AP, mortise, and lateral ankle radiographs
• Weight-bearing hindfoot alignment view (Saltzman view)
• CT to assess joint destruction, bone loss, and surgical planning
• MRI in suspected AVN (sagittal STIR/T1 to assess talar viability) or Charcot (assess oedema and fragmentation)
• Inflammatory markers and wound review if infection suspected

Consent:

• Specific risks: nonunion (10-30%), malunion, infection (5-10%), nerve injury, plantar wound problems, stress fracture at the nail tip (3-8%), DVT/PE, complex regional pain syndrome, need for revision
• Expected outcomes: pain relief, plantigrade foot, but loss of all hindfoot motion (inversion/eversion) and ankle motion; gait will be stiff but functional

Positioning and Preparation

Patient position: Supine on a radiolucent table with a bump under the ipsilateral hip to bring the foot into neutral rotation. A tourniquet is applied to the thigh and inflated after exsanguination. The leg is prepped and draped free from the knee distally. A small foot-rest or stack of towels under the calf raises the heel off the table and improves access to the plantar entry portal.

Image intensifier: Positioned on the contralateral side. Confirm AP and lateral views of the tibia, ankle, and calcaneus are obtainable before draping. The C-arm should swing freely from AP to lateral without repositioning the leg.

Anaesthesia: General or regional anaesthesia. Preoperative antibiotics (e.g. cefazolin 2 g IV) within 60 minutes of skin incision. Tranexamic acid may be used per local protocol.

Bone graft: Prepare the iliac crest or proximal tibia if structural graft is anticipated. Otherwise, tibial reamings are typically sufficient as cancellous autograft.

Step-by-Step Operative Technique

Step 1: Achilles Lengthening (if required)

• Perform a percutaneous triple hemisection Achilles lengthening or a formal open Z-lengthening FIRST
• Reassess ankle dorsiflexion with the knee in extension; aim for 5-10 degrees of dorsiflexion with the foot plantigrade
• If gastrocnemius contracture alone (positive Silfverskiold with knee flexed, neutral with extended knee but restricted dorsiflexion): perform a Strayer gastrocnemius recession

Step 2: Joint Preparation — Ankle (Anterior or Lateral Transfibular Approach)

Anterior approach (most common):

• Anterior longitudinal incision over the ankle joint, lateral to the extensor hallucis longus (EHL) tendon
• Identify and protect the deep peroneal nerve and anterior tibial artery (lie between EHL and extensor digitorum longus)
• Open the extensor retinaculum and retract the tendons medially or laterally
• Capsulotomy exposes the tibiotalar joint
• Remove the anterior osteophytes and cartilage with osteotomes, curettes, and a burr
• Use a lamina spreader to access the posterior cartilage

Lateral transfibular approach (for combined ankle-subtalar disease or when an anterior approach is contraindicated):

• Oblique incision over the distal fibula, continuing distally toward the sinus tarsi
• Osteotomise the fibula 6-8 cm proximal to the tip and reflect it distally with the anterior talofibular and calcaneofibular ligaments intact (or detach the ligaments and reattach through bone tunnels later)
• Provides excellent access to both the tibiotalar and subtalar joints

Step 3: Joint Preparation — Subtalar Joint

• Use the sinus tarsi approach (3-4 cm incision over the sinus tarsi from the tip of the lateral malleolus toward the fourth metatarsal base)
• Identify the fat pad in the sinus tarsi and excise it
• Open the capsule of the posterior facet
• Remove cartilage from the posterior facet with curettes and a high-speed burr
• Denude the middle and anterior facets through the same incision or a separate medial approach if required
• Fish-scale the subchondral plate to bleeding bone on both sides

Step 4: Plantar Entry Portal

• Palpate the plantar hindfoot and identify the weight-bearing surface of the heel pad
• Make a 3-4 cm transverse or short oblique incision slightly LATERAL to the midline of the heel pad, centred over the calcaneal tuberosity
• Dissect bluntly through subcutaneous fat; identify the lateral plantar neurovascular bundle medially and retract it
• Incise the plantar fascia in line with its fibres and split the intrinsic foot muscles (flexor digitorum brevis) in line with the incision
• Identify the calcaneal tuberosity and the posterior facet of the calcaneus
• Place a guide wire under AP and lateral fluoroscopy at the junction of the posterior and middle facets of the calcaneus, in line with the tibial canal
• Confirm on AP view: guide wire should lie in the centre of the tibial plafond
• Confirm on lateral view: guide wire should lie in line with the tibial shaft axis, slightly posterior to the centre of the talar body

Step 5: Reaming and Nail Selection

• Ream sequentially over the guide wire, starting at 8 mm and increasing in 0.5-1 mm increments
• Ream to 1 mm greater than the chosen nail diameter
• Reaming collects cancellous autograft in the bone-sieve
• Confirm reaming trajectory on AP and lateral fluoroscopy at each step
• Select a nail length such that the proximal tip rests in the tibial metaphysis (long nails 180-300 mm reduce stress fracture risk at the nail tip)
• Select a nail diameter based on the reamed canal (typically 10-13 mm)

Step 6: Correction of Alignment

• Before nail insertion, CORRECT the hindfoot to a plantigrade position
• Aim for: hindfoot valgus 5 degrees, neutral forefoot, tibial axis through the central hindfoot
• Address any residual equinus (Achilles lengthening already performed)
• Use a medial or lateral translation of the calcaneus relative to the tibia as needed
• Hold the position with the guide wire and provisional K-wires during reaming
• Confirm alignment with AP and lateral fluoroscopy before final nail insertion

Step 7: Bone Grafting

• Pack cancellous autograft (tibial reamings or iliac crest) into the tibiotalar and subtalar joints BEFORE nail insertion
• For AVN, severe bone loss, or Charcot: add structural graft (tricortical iliac crest, femoral head allograft) bridging the tibial plafond to the calcaneus
• Consider bone morphogenetic protein (BMP) adjunct in Charcot, AVN, or revision
• Distribute graft circumferentially around the nail after insertion

Step 8: Nail Insertion

• Insert the chosen nail over the guide wire
• Confirm depth on lateral fluoroscopy — the proximal tip should sit in the tibial metaphysis
• Confirm trajectory on AP fluoroscopy — the nail should be centred in the tibial canal
• Remove the guide wire
• Confirm rotational alignment before locking

Step 9: Locking Screws

• Place proximal locking screws in the tibia through the targeting guide — typically 2 screws (one in each of two planes)
• Place distal locking screws in the calcaneus and talus through the targeting guide
• For rotational control, use at least 2 calcaneal screws in different planes
• If the nail has a talar screw option, place it for additional fixation
• Confirm screw lengths on fluoroscopy — bicortical purchase in the calcaneus, avoid screw tip protrusion into the plantar soft tissues

Step 10: Wound Closure and Dressing

• Irrigate all wounds copiously
• Close the anterior or lateral approach in layers — joint capsule, extensor retinaculum (if divided), subcutaneous tissue, skin
• Close the sinus tarsi incision in layers
• Close the plantar incision in layers — the deep intrinsic muscle layer, the plantar fascia, subcutaneous tissue, skin
• Apply a sterile non-adherent dressing and a well-padded posterior splint in neutral position

Post-operative Protocol

Early Phase (Day 0-14)

• Splint: Posterior plaster splint in neutral position, well-padded
• Elevation: Strict elevation for 48-72 hours; foot above heart level
• Analgesia: Multimodal — paracetamol, NSAIDs (if no contraindication), opioids as required
• Antibiotics: Perioperative dose (cefazolin 2 g IV) within 60 minutes of incision; 1-2 further doses per local protocol
• VTE prophylaxis: Mechanical (foot pumps) immediately; chemical per risk assessment
• Wound review: At 48-72 hours; remove the splint, inspect the plantar and other wounds, replace dressing
• Non-weight-bearing: Strict NWB on the operated leg for 6-12 weeks depending on indication (Charcot and AVN often require 3 months)

Intermediate Phase (Weeks 2-12)

• Suture removal: 10-14 days for skin sutures; absorbable sutures may be left
• Cast or boot: Transition to a removable boot or short-leg cast at 2-3 weeks once wounds healed
• Radiographs: At 6 weeks and 12 weeks; assess for early union (bridging trabeculae, no lucency)
• CT scan: At 3-6 months if union uncertain on radiographs and the patient is symptomatic
• Weight-bearing: Progressive WB in boot at 6-8 weeks for primary cases; Charcot and AVN remain NWB until CT confirms union
• Swelling management: Compression stocking; elevate when at rest

Return to Function

• Light activities: From 6-8 weeks (sitting work)
• Driving: Right foot: 8-12 weeks minimum; left foot (automatic): 4-6 weeks
• Return to work: Office work 8-12 weeks; manual work 4-6 months
• Recreational walking: From 3-4 months
• Sport: Low-impact (swimming, cycling) from 6 months; high-impact (running) often not advisable after TTC fusion

Long-term Follow-up

• Radiographs: At 6 months, 12 months, then annually for 3 years
• CT: At 6-9 months for union confirmation
• Functional assessment: AOFAS or FAAM score at 12 months
• Monitor for: Stress fracture at the nail tip (years 1-3), adjacent joint arthritis (years 3+), implant irritation (loosening, screw pain)

Special Case: Failed Total Ankle Replacement (TAR)

Why TAR Failure Leads to TTC Nail

• Modern TAR has 10-year survivorship of 80-90% in most series, but a proportion fail
• Common failure modes: talar component subsidence, polyethylene wear, aseptic loosening, deep infection, and progression of subtalar arthritis
• When revision TAR is not feasible (bone loss, infection, severe deformity, or surgeon/patient preference), TTC nail is the gold standard salvage

Key Technical Points

• Plan for talar bone loss — the explanted talar component may leave a large defect
• Use a long hindfoot nail to the tibial metaphysis for stable load-sharing
• Structural bone graft (femoral head allograft or iliac crest autograft) to fill the talar defect
• In two-stage revision for infection: first stage — explant TAR, antibiotic cement spacer, 6-8 weeks IV antibiotics; second stage — TTC nail with structural graft
• Counsel the patient that TTC fusion is a definitive salvage — no further revision options

Outcomes

• Union rate 75-85%
• Patient satisfaction 75-85% — comparable to primary TTC
• Functional improvement (AOFAS) similar to primary TTC despite more complex surgery

Special Case: Charcot Neuroarthropathy

Staging and Decision-Making

• Eichenholtz stage 1 (development): swelling, erythema, no deformity — conservative management with total contact cast
• Eichenholtz stage 2 (coalescence): fragmentation, subluxation — consider TTC nail if deformity progresses
• Eichenholtz stage 3 (reconstruction): consolidation with residual deformity — TTC nail is the primary reconstruction
• Brodsky classification: type 1 (midfoot, most common); type 2 (subtalar/Chopart); type 3A (ankle); type 3B (ankle with calcaneal involvement)

Key Technical Points

• Long hindfoot nail extending to the tibial metaphysis
• Adjunctive bone graft — autogenous (proximal tibia or iliac crest) or BMP
• May require adjunctive plate fixation for severely comminuted joints
• Correction of rocker-bottom deformity: lengthening of the Achilles, plantar fascia release, and bony realignment
• Staged procedure: first stage — debridement, infection workup, offloading; second stage — TTC nail after soft tissue healing

Outcomes

• Union rate 50-70%
• Limb salvage rate 85-90% at 5 years
• Patient satisfaction 70-80% — high given the alternative is amputation
• Higher complication rate than primary TTC (up to 30%)

Postoperative Management

• Strict NWB for 3 months in Charcot — long enough to allow the bone to consolidate
• Use of a Charcot restraint orthotic walker (CROW) boot or total contact cast during the transition to weight-bearing
• Long-term custom-molded foot orthosis
• Strict glycaemic control (HbA1c less than 7.5%)

Special Case: Avascular Necrosis of the Talus

Aetiology and Preoperative Assessment

• Post-traumatic (talar neck fracture, talar body fracture, dislocation)
• Idiopathic
• Secondary to corticosteroid use, sickle cell, alcohol, or systemic disease
• MRI is the investigation of choice — STIR/T1 sequences show the extent of necrosis and the viability of the talar body
• Ficat-Arlet classification of AVN can be applied to the talus

Surgical Options

• Core decompression (early AVN without collapse) — core track through the talar neck
• Tibiotalocalcaneal arthrodesis with structural graft — the talus is preserved as a scaffold; structural graft bridges the tibial plafond to the calcaneus
• Talectomy with tibiocalcaneal arthrodesis — the talar body is excised; the nail fuses the tibia directly to the calcaneus
• Total talar replacement — emerging; long-term data limited

Outcomes

• Union rate 50-70% with TTC nail and structural graft
• Talectomy with tibiocalcaneal arthrodesis: 70% union
• Function is comparable to other TTC indications
• Counsel patient about high nonunion rate and possible revision

Special Case: Tibiotalocalcaneal vs Isolated Ankle + Subtalar Fusion

When to Fuse Both Joints

• Documented arthritis of BOTH joints
• Failed isolated fusion with symptomatic adjacent joint disease
• Charcot hindfoot
• Severe deformity requiring correction across both joints
• AVN of the talus

When to Consider Staged or Isolated Fusion

• Isolated tibiotalar arthritis with normal subtalar joint — consider ankle arthrodesis alone
• Isolated subtalar arthritis with normal ankle — consider subtalar arthrodesis alone
• Young, high-demand patient with combined disease — consider staged fusions to preserve some hindfoot motion
• TAR with subtalar arthritis in a young patient — consider TAR with isolated subtalar fusion to retain some ankle motion

Functional Trade-off

• TTC fusion: loss of ALL ankle and subtalar motion; stiff but functional gait
• Staged ankle + subtalar fusion: still loses both motions; the practical difference is the order of surgery, not the final motion
• TAR + subtalar fusion: retains ankle sagittal motion; subtalar motion is sacrificed
• A young patient with combined disease who undergoes TTC fusion is committed to a stiff hindfoot for life