Talonavicular Arthritis

1. Clinical Overview

Summary

Talonavicular (TN) arthritis represents pathological degeneration of the "Coxa Pedis" or "Hip of the Foot"—the critical ball-and-socket articulation formed between the head of the talus and the concave socket created by the navicular, spring ligament complex, and sustentaculum tali. This anatomically unique joint is responsible for 80-90% of all complex hindfoot motion, including the coupled movements of inversion, eversion, and transverse plane rotation that are essential for normal gait on uneven terrain. [1,2]

Consequently, arthritic degeneration of this joint is profoundly disabling, producing deep-seated midfoot pain and progressive rigid planovalgus deformity. The condition represents either the endpoint of chronic posterior tibial tendon dysfunction (PTTD Stage IV), a hallmark manifestation of rheumatoid arthritis, or idiopathic osteonecrosis (Müller-Weiss syndrome). [3,4]

Treatment options are predominantly surgical, with arthrodesis (fusion) being the definitive intervention. Due to the high non-union rates associated with isolated talonavicular fusion (10-15%) and the biomechanical interdependence with the subtalar joint, contemporary practice favors Double Arthrodesis (TN + Subtalar fusion), which provides superior deformity correction, higher union rates, and preservation of the lateral column. [5,6]

Key Facts

Acetabulum Pedis Architecture: The talonavicular joint is not a simple two-bone articulation. The "socket" (acetabulum pedis) is a composite structure formed by:

• Navicular articular surface (superior concavity)
• Superomedial calcaneonavicular (Spring) ligament (inferior floor)
• Sustentaculum tali (medial buttress) This tripartite suspension system distributes axial loads and permits multidirectional motion. [7]

The Motion Killer: Arthrodesis of the talonavicular joint effectively eliminates approximately 90% of subtalar joint motion due to biomechanical coupling via Chopart's joint locking mechanism. In contrast, isolated subtalar fusion permits retention of approximately 25% of talonavicular motion. [1,8]

The Rheumatoid Target: Among all foot and ankle joints, the talonavicular articulation is preferentially and earliest affected in seropositive rheumatoid arthritis, with involvement documented in 40-60% of RA patients. Progressive inflammatory synovitis leads to spring ligament attenuation, medial column collapse, and characteristic valgus drift. [9,10]

Clinical Pearls

"The Circle of Pain": Patients characteristically grasp their foot with a 'C-clamp' grip during history-taking—thumb positioned over the medial longitudinal arch (navicular tuberosity), fingers curled around the lateral border (sinus tarsi). They describe pain as "deep inside the center of the foot" rather than superficial or localized to a specific border.

"Ortho-Biologics Imperative": The talonavicular joint has the highest non-union rate among hindfoot fusions (10-15%) due to unfavorable biomechanical factors: small contact surface area (~2-3 cm²), high shear forces during gait, and frequent poor bone quality (osteopenia, cystic change in RA). Autologous bone grafting (iliac crest or calcaneal) combined with rigid dual-plane fixation (compression screws + dorsal neutralization plate) is mandatory to achieve successful arthrodesis. [11,12]

"Double Trouble—Double Benefit": Isolated talonavicular fusion in the setting of a valgus heel leaves residual subtalar malalignment, resulting in persistent pain, lateral column overload, and high mechanical failure rates. Double arthrodesis (TN + Subtalar) addresses the entire hindfoot as a unified mechanical block, permits powerful valgus correction through calcaneal translation, and paradoxically improves patient-reported outcomes compared to triple arthrodesis by preserving Chopart lateral column motion. [5,13]

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2. Epidemiology

Demographics

Prevalence: Isolated talonavicular arthritis accounts for 3-5% of all hindfoot arthritis presentations. However, combined TN and subtalar involvement is significantly more common, representing 60-70% of cases requiring hindfoot arthrodesis. [14]

Age Distribution:

• Post-traumatic: Younger patients (30-50 years) following navicular fractures or severe midfoot injuries
• Inflammatory (RA): Middle-aged patients (40-60 years) with established seropositive disease
• Degenerative/PTTD: Older demographic (55-75 years) with longstanding flatfoot deformity

Gender: Female predominance (3:1) in RA-associated and PTTD-related cases; male predominance in post-traumatic etiology. [3,9]

Etiology

Inflammatory Arthropathy (30-40%):

• Rheumatoid Arthritis: Seropositive RA preferentially targets the talonavicular joint, with synovitis-driven cartilage destruction and spring ligament incompetence
• Seronegative Spondyloarthropathies: Psoriatic arthritis, ankylosing spondylitis (less common)

Post-Traumatic (25-30%):

• Navicular fractures: Body fractures with articular extension
• Talar neck fractures: Comminution involving talar head articular surface
• Lisfranc injuries: High-energy mechanisms with Chopart extension
• Chronic lateral ankle instability: Repetitive inversion stress leading to abnormal kinematics

Biomechanical Deformity (25-30%):

• Posterior Tibial Tendon Dysfunction (PTTD): Stage IV disease defined by talonavicular arthritis in addition to medial column collapse
• Longstanding untreated adult-acquired flatfoot: Progressive valgus overload and articular wear

Idiopathic Osteonecrosis (5-10%):

• Müller-Weiss Syndrome: Spontaneous fragmentation and collapse of the navicular (typically lateral aspect) leading to talonavicular incongruity and secondary arthritis [4]

Other Causes (less than 5%):

• Crystal arthropathy (gout, pseudogout)
• Septic arthritis sequelae
• Neuropathic arthropathy (Charcot)

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3. Pathophysiology

Functional Anatomy

Joint Classification: Enarthrodial (ball-and-socket) synovial joint

Articular Geometry:

• Talar Head: Convex articular surface with three distinct facets (navicular, anterior calcaneal, spring ligament)
• Navicular Socket: Concave proximal articular surface complemented inferiorly by the fibrocartilaginous spring ligament
• Congruency: Approximately 80% of the talar head is covered by the navicular in neutral position (> 30% uncovering indicates subluxation) [15]

Biomechanical Role—The Keystone of Chopart's Joint:

The talonavicular and calcaneocuboid joints together constitute Chopart's joint, which functions as the critical link between the rigid hindfoot (talus-calcaneus) and the flexible midfoot/forefoot.

Chopart Locking Mechanism (Elftman and Manter's Model): [2]

• Heel Inversion: The axes of the TN and CC joints diverge (non-parallel), creating a rigid "locked" midfoot that provides a stable lever for push-off
• Heel Eversion: The axes become parallel, creating an "unlocked" flexible midfoot that accommodates ground irregularities during stance phase

Motion Contribution:

• Inversion/Eversion: 80-90% occurs at TN joint
• Transverse rotation: 70% occurs at TN joint
• Plantarflexion/Dorsiflexion: Minimal contribution (5-10°)

Load Transmission: The TN joint transmits approximately 2.5-3× body weight during normal gait, peaking at 5-6× body weight during running. [16]

Pathomechanics

Sagittal Plane Breach (PTTD Pathway):

In progressive posterior tibial tendon insufficiency, sequential biomechanical failure occurs: [3,17]

1. Primary Event: PTT degeneration → loss of dynamic arch support
2. Spring Ligament Failure: Chronic overload leads to superomedial calcaneonavicular ligament attenuation
3. Talar Head Plantarflexion: Unsupported talus "dives" plantarly and medially (plantar sag)
4. Navicular Dorsolateral Translation: Compensatory navicular displacement creates:
   • Increased contact pressure on dorsolateral aspect
   • Shear stress across incongruent joint surfaces
   • Progressive cartilage wear
5. Fixed Deformity: Capsular contracture and eventual bone-on-bone arthritis

Inflammatory Synovitis Pathway (Rheumatoid Arthritis):

RA demonstrates a distinct predilection for the TN joint: [9,10]

1. Synovial Proliferation: Pannus formation with inflammatory cytokine release (TNF-α, IL-1, IL-6)
2. Cartilage Degradation: Matrix metalloproteinase-mediated proteoglycan depletion
3. Bone Erosion: Osteoclast activation creating characteristic marginal erosions and subchondral cysts
4. Ligamentous Incompetence: Enzymatic degradation of spring ligament collagen
5. Secondary Deformity: Progressive valgus collapse secondary to medial restraint failure

Post-Traumatic Pathway:

Acute articular injury disrupts normal joint mechanics:

1. Articular Incongruity: Step-off or gap deformity from fracture malunion
2. Focal Overload: Abnormal contact stress distribution
3. Cartilage Degeneration: Progressive chondrocyte death and matrix breakdown
4. Subchondral Sclerosis: Bone response to abnormal loading
5. Osteophyte Formation: Marginal new bone formation

Molecular Pathophysiology

Exam Detail: Cartilage Degradation Cascade:

Articular cartilage breakdown in TN arthritis follows established osteoarthritis pathways:

• Chondrocyte Dysfunction: Increased production of matrix metalloproteinases (MMP-1, MMP-3, MMP-13) and aggrecanases (ADAMTS-4, ADAMTS-5)
• Proteoglycan Loss: Depletion of aggrecan reduces osmotic swelling pressure and shock absorption
• Collagen Network Disruption: Type II collagen degradation compromises tensile strength
• Pro-inflammatory Milieu: IL-1β and TNF-α upregulation drives catabolic metabolism
• Failed Repair: Inadequate chondrocyte synthetic response to mechanical injury [18]

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4. Clinical Presentation

Symptoms

Pain Characteristics:

• Location: Deep medial midfoot centered over navicular tuberosity; may radiate proximally to medial malleolus or distally along medial column
• Quality: Dull, aching, "bone-deep" pain (distinct from sharp superficial tendinitis pain)
• Exacerbating Factors:
  • Uneven ground, gravel, stairs
  • Prolonged standing or walking
  • Pushing off during gait
  • Single-leg heel rise (if flexible deformity remains)
• Relieving Factors: Rest, elevation, rigid footwear, bracing

Functional Limitations:

• Gait Disturbance: Antalgic gait with shortened stance phase on affected side; inability to walk on uneven terrain
• Deformity Awareness: "My arch has collapsed," "My foot rolls inward," "My ankle looks crooked"
• Footwear Difficulties: Inability to wear normal shoes; requires extra-depth or custom footwear

Associated Symptoms:

• Swelling: Dorsomedial prominence from osteophyte formation and synovitis
• Stiffness: Morning stiffness > 30 minutes (inflammatory), end-of-day stiffness (mechanical)
• Lateral Foot Pain: Compensatory lateral column overload (calcaneocuboid arthritis, peroneal tendinitis, sural nerve irritation)

Signs

Observation (Standing):

Alignment Assessment:

• Planovalgus Deformity: Loss of medial longitudinal arch height; increased calcaneal valgus (> 5-10°)
• "Too Many Toes" Sign: Viewing from behind, > 2 lateral toes visible due to forefoot abduction (normal: 1-1.5 toes visible) [3]
• Medial Prominence: Talar head palpable as medial bulge distal to medial malleolus
• Forefoot Supination: Compensatory forefoot varus to maintain plantigrade foot position

Gait Analysis:

• Heel Strike: Reduced shock absorption; may land in valgus
• Midstance: Prolonged foot-flat phase; loss of dynamic arch reconstitution
• Push-Off: Weak or absent push-off; externally rotated foot progression angle

Palpation:

Bony Tenderness:

• Talonavicular Joint Line: Maximal tenderness 2-3 cm distal and inferior to medial malleolus
• Navicular Tuberosity: Medial prominence often tender (traction spur, pressure from deformity)
• Sinus Tarsi: Lateral tenderness may indicate subtalar involvement

Soft Tissue Assessment:

• Posterior Tibial Tendon: Assess continuity, thickness, tenderness along course from medial malleolus to navicular insertion
• Spring Ligament: Deep palpation inferior to talar head (often impossible to directly assess)
• Medial Skin: Check for ulceration over prominent navicular tuberosity in severe valgus

Range of Motion (ROM):

Hindfoot Motion (isolate by stabilizing tibia with one hand, manipulating calcaneus with other):

• Inversion/Eversion: Markedly reduced or absent (compare to contralateral)
• Normal Values: Inversion 30-40°, Eversion 15-20°
• Pain Provocation: Passive inversion typically reproduces TN joint pain

Midfoot Motion:

• Assess at Chopart's Joint: Stabilize hindfoot, attempt to rotate forefoot
• Stiffness Pattern: Global midfoot stiffness suggests multi-level arthritis

Special Tests:

Single-Leg Heel Rise Test: [3,17]

• Technique: Patient stands on one leg and attempts to rise onto toes
• Positive Finding: Inability to perform (fixed deformity); ability to perform but pain (flexible deformity with compensation)
• Additional Observation: Heel should invert during heel rise; failure to invert indicates PTT incompetence or fixed hindfoot valgus

Navicular Drop Test:

• Technique: Mark navicular tuberosity position in sitting (non-weight-bearing) vs. standing (weight-bearing)
• Interpretation: > 10 mm drop indicates excessive motion (spring ligament insufficiency)
• Limitation: Not reliable in fixed rigid deformity

Vascular and Neurological Examination:

• Dorsalis Pedis and Posterior Tibial Pulses: Essential pre-operative assessment
• Sensation: Saphenous, superficial peroneal, sural nerve distributions
• Motor: Strength testing of tibialis anterior, posterior, EHL, FHL, peronei

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5. Investigations

Imaging

Plain Radiographs (Weight-Bearing ESSENTIAL): [15,19]

Non-weight-bearing films miss critical alignment and deformity assessment.

AP (Anteroposterior) View:

• Joint Space: Narrowing (less than 2 mm indicates loss of cartilage)
• Osteophytes: Dorsal and medial marginal osteophytes
• Subchondral Changes: Sclerosis, cysts (particularly in RA)
• Talar Head Uncovering: Lateral subluxation of navicular
  • "Measurement: Percentage of talar head uncovered laterally"
  • "Interpretation: > 30% = significant subluxation requiring reduction during fusion"
• Talonavicular Coverage Angle: Angle between medial and lateral articular edges (decreased in uncovering)
• AP Talus-First Metatarsal Angle: Normally 0-10°; increased angle indicates forefoot abduction

Lateral View:

• Meary's Angle (Talus-First Metatarsal Angle): [15]
  • "Measurement: Angle between longitudinal axis of talus and first metatarsal"
  • "Normal: 0-5° (collinear)"
  • "Interpretation: > 10° indicates flatfoot deformity; > 20° severe collapse"
• Calcaneal Pitch Angle: Angle between calcaneus and ground
  • "Normal: 20-30°"
  • "Low Pitch: less than 15° indicates flatfoot"
• Dorsal Talonavicular Beaking: Dorsal osteophyte at TN articulation indicating chronic subluxation and impingement
• Cyma Line Disruption: Smooth S-shaped curve formed by TN and CC joints is broken in subluxation

Hindfoot Alignment View (Saltzman View):

• Technique: Long axial hindfoot radiograph taken from behind with patient standing
• Purpose: Quantifies valgus/varus alignment of hindfoot relative to tibia
• Measurement: Tibial-calcaneal offset and angle

CT Scan (Computed Tomography): [12,20]

Indications:

• Surgical planning for arthrodesis
• Assessment of adjacent joint arthritis (subtalar, calcaneocuboid, naviculocuneiform)
• Bone quality evaluation (cysts, osteopenia)
• Post-traumatic cases to assess articular incongruity

Protocol: Thin-slice axial images (1-2 mm) with coronal and sagittal reconstructions

Key Findings:

• Articular Surface Mapping: Precise delineation of cartilage loss distribution
• Subchondral Cysts: Size and location (affects surgical planning for grafting)
• Bone Stock Assessment: Evaluate for osteopenia or bone loss requiring structural graft
• Adjacent Joint Disease: Particularly important to assess subtalar joint (coalition, arthritis)

MRI (Magnetic Resonance Imaging):

Indications (selective use):

• Young patients with pain but minimal radiographic changes (early arthritis)
• Assessment of spring ligament integrity
• Evaluation of PTT pathology
• Rule out osteonecrosis (Müller-Weiss), stress fracture, or occult trauma

Protocol: T1, T2, STIR sequences in all three planes

Key Findings:

• Cartilage Lesions: Focal defects or diffuse thinning
• Bone Marrow Edema: T2/STIR hyperintensity indicates active stress or inflammation
• Spring Ligament: Thickening, increased signal, discontinuity indicates degeneration [7]
• PTT: Longitudinal split tear, tenosynovitis, increased intrasubstance signal
• Synovitis: Joint effusion, synovial enhancement

Diagnostic Injection (Image-Guided):

Technique: Ultrasound or fluoroscopy-guided injection of local anesthetic +/- corticosteroid into TN joint

Indications:

• Pain source localization when clinical examination equivocal
• Multiple potential pain generators (TN vs. subtalar vs. ankle)
• Predict surgical benefit from arthrodesis

Interpretation:

• > 50% Pain Relief: Confirms TN joint as primary pain source
• less than 50% Relief: Consider alternative diagnosis or multi-level pathology

Laboratory Tests (Selected Cases):

Inflammatory Arthritis Workup (if RA suspected):

• Rheumatoid Factor (RF), Anti-CCP antibodies
• ESR, CRP (elevated in active inflammation)
• ANA, HLA-B27 (if seronegative spondyloarthropathy suspected)

Pre-Operative:

• CBC, coagulation profile
• Metabolic panel (renal function if NSAID use)
• HbA1c (diabetes control affects union rates)
• Vitamin D, calcium (optimize bone health)

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6. Classification Systems

Johnson and Strom Classification (Modified by Myerson) for PTTD: [17]

This classification is relevant as Stage IV PTTD = TN arthritis.

• Stage I: Tenosynovitis without deformity
• Stage II: Flexible flatfoot deformity (passively correctable)
  • "IIA: Forefoot varus less than 30%"
  • "IIB: Forefoot varus > 30%"
• Stage III: Fixed (rigid) flatfoot deformity
  • "IIIA: Isolated hindfoot arthritis (subtalar)"
  • "IIIB: Rigid forefoot varus"
• Stage IV: Fixed flatfoot + Talonavicular and/or Ankle Arthritis

Maceira Classification (Müller-Weiss Disease): [4]

• Stage 1: Radiographic changes without symptoms
• Stage 2: Spontaneous osteonecrosis with lateral navicular collapse
• Stage 3: Progressive subluxation with secondary TN arthritis
• Stage 4: Advanced degenerative changes with fixed deformity
• Stage 5: Pan-hindfoot arthritis

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7. Management Algorithm

                           MIDFOOT PAIN + PLANOVALGUS DEFORMITY
                                        ↓
                        WEIGHT-BEARING RADIOGRAPHS: TN ARTHRITIS
                                        ↓
                        ┌───────────────┴───────────────┐
                    ISOLATED TN                  MULTI-JOINT DISEASE
                  (No ST/CC/Ankle)              (TN + ST +/- CC +/- Ankle)
                        ↓                                ↓
                   CT SCAN ←─────────────────────────────┘
               (Confirm extent)
                        ↓
            ┌───────────┴───────────┐
        FLEXIBLE                 FIXED/RIGID
      (Passively Correctable)    (Contracted)
            ↓                         ↓
      CONSERVATIVE              CONSERVATIVE
            ↓                         ↓
    ┌──────┴──────┐              ┌────┴────┐
  UCBL         Arizona         Arizona    Rocker
 Orthosis     Gauntlet Brace    Brace    Bottom Shoe
    ↓              ↓                ↓         ↓
    └──────────────┴────────────────┴─────────┘
                    ↓
           ADEQUATE SYMPTOM CONTROL?
                    ↓
        ┌───────────┴───────────┐
       YES                     NO → SURGICAL INTERVENTION
        ↓                          ↓
   CONTINUE                   CT REASSESSMENT
 CONSERVATIVE                      ↓
                       ┌────────────┴────────────┐
                  ISOLATED TN              TN + ST +/- CC
                   ARTHRITIS            MULTI-LEVEL DISEASE
                       ↓                         ↓
              ISOLATED TN FUSION          ┌──────┴──────┐
              (High Non-Union Risk)   TN + ST      TN + ST + CC
              Consider Double          DOUBLE      TRIPLE
                   instead          ARTHRODESIS   ARTHRODESIS
                                   (Preferred)
                                        ↓
                            BONE GRAFT + RIGID FIXATION
                                        ↓
                              POST-OP IMMOBILIZATION
                                  (12 weeks)

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8. Management: Conservative (Non-Operative)

Indications for Conservative Management

• Low-demand patients (elderly, sedentary lifestyle)
• Significant medical comorbidities (surgical risk outweighs benefit)
• Patient preference (informed refusal after discussion)
• Early/mild arthritis with acceptable pain control

Treatment Modalities

1. Orthotic Management: [3,14]

UCBL (University of California Biomechanics Laboratory) Orthosis:

• Design: Rigid polypropylene shell extending from heel to navicular; captures calcaneus in neutral position
• Mechanism: Corrects flexible hindfoot valgus by mechanically supporting medial arch
• Indications: Flexible deformity (Stage II PTTD) with early TN arthritis
• Limitations: Ineffective in fixed rigid deformity; requires extra-depth footwear

Arizona Gauntlet Brace (AFO):

• Design: Leather lace-up ankle-foot orthosis with dual uprights; encases ankle and hindfoot
• Mechanism: Rigid immobilization of ankle and hindfoot joints to eliminate painful motion
• Indications: Gold standard for rigid TN arthritis; effective pain control in non-surgical candidates
• Limitations: Bulky; requires larger shoe size; ankle stiffness limits function
• Evidence: Provides significant pain relief in 60-70% of patients with rigid hindfoot arthritis [14]

Custom-Molded AFO:

• Thermoplastic AFO molded in corrected hindfoot position
• Less bulky than Arizona brace but still requires larger footwear

2. Footwear Modifications:

• Rocker-Bottom Sole: ESSENTIAL to reduce push-off demand on painful TN joint by shifting ground reaction force anteriorly
• Extra-Depth Shoes: Accommodate orthosis and foot deformity
• Medial Posting: Mild cases with flexible deformity (limited benefit in rigid arthritis)
• Stiff Shank: Reduces midfoot motion

3. Pharmacological Management:

NSAIDs:

• Mechanism: COX inhibition reduces prostaglandin-mediated inflammation and pain
• Options: Ibuprofen 400-600 mg TID, Naproxen 500 mg BID, Diclofenac 50 mg TID
• Cautions: GI bleeding risk, cardiovascular events, renal dysfunction; avoid in CKD

Acetaminophen:

• First-line in elderly or those with NSAID contraindications
• 1000 mg QID (maximum 4 g/day)

Topical NSAIDs:

• Diclofenac gel applied to medial midfoot
• Lower systemic absorption; reduced GI/renal risk

4. Corticosteroid Injection (Image-Guided):

Technique:

• Ultrasound or fluoroscopy-guided injection to ensure intra-articular placement
• 40-80 mg methylprednisolone or 4-6 mg betamethasone + 1-2 mL 1% lidocaine

Efficacy:

• 50-70% experience short-term pain relief (3-6 months)
• Diminishing returns with repeated injections [14]

Limitations:

• Temporary relief only; does not alter disease progression
• Maximum 3 injections per year (cartilage toxicity risk)
• Contraindicated in infection, diabetes (hyperglycemia), Charcot arthropathy

5. Physical Therapy:

• Gait Training: Optimize gait mechanics to reduce TN joint loading
• Strengthening: Intrinsic foot muscles, tibialis posterior (if functional tendon remains)
• Range of Motion: Maintain ankle dorsiflexion to reduce compensatory midfoot stress
• Modalities: Ice, ultrasound, TENS (limited evidence but low risk)

6. Activity Modification:

• Avoid prolonged standing, uneven terrain, impact activities
• Weight loss (if obese) to reduce joint loading
• Low-impact aerobic exercise (swimming, cycling)

Expected Outcomes

Success Rate: 30-50% of patients achieve acceptable long-term symptom control with bracing [14]

Failure Predictors:

• High activity demands
• Severe deformity (Meary angle > 20°)
• Advanced arthritis (bone-on-bone)
• Young age (less than 50 years)

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9. Management: Surgical

Indications for Surgery

Absolute:

• Disabling pain refractory to 3-6 months of appropriate conservative management
• Progressive deformity with skin breakdown or ulceration
• Functional limitations incompatible with lifestyle/occupation

Relative:

• Moderate pain with high functional demands
• Patient preference for definitive treatment

Pre-Operative Planning

Radiographic Assessment:

• Weight-bearing radiographs: Define extent of deformity and arthritis
• CT scan: Map articular surfaces, assess adjacent joints, evaluate bone stock
• Alignment planning: Determine degree of correction needed (heel valgus, forefoot abduction)

Bone Quality Optimization:

• Optimize vitamin D (> 30 ng/mL), calcium supplementation
• Control diabetes (HbA1c less than 7%)
• Smoking cessation (minimum 6 weeks pre-op; nicotine profoundly impairs fusion)

Surgical Procedures

1. Isolated Talonavicular Arthrodesis

Indications: [11]

• Truly isolated TN arthritis (rare)
• No significant heel valgus deformity (less than 5°)
• Subtalar joint pristine on CT

Surgical Technique:

Approach:

• Medial Incision: 6-8 cm longitudinal incision centered over TN joint, midway between tibialis anterior and posterior tendons
• Superficial Dissection: Identify and protect saphenous vein and nerve
• Deep Dissection: Incise joint capsule; retract TA tendon dorsally, TP tendon plantarly

Joint Preparation:

• Cartilage Removal: Osteotomes, curettes, or power burr to remove all cartilage and sclerotic subchondral bone down to bleeding cancellous bone
• Preserve Architecture: Maintain navicular and talar bone stock; avoid excessive resection
• Feathering Technique: Create multiple small perforations in subchondral bone with 1.5 mm drill to enhance vascular ingrowth

Deformity Correction:

• Alignment Goals: Restore medial longitudinal arch; correct forefoot abduction; neutral hindfoot alignment
• Provisional Fixation: 2.0 mm K-wires hold reduction

Bone Grafting: [12]

• Autograft: Iliac crest corticocancellous or calcaneal cancellous
• Indications: Cystic bone, osteopenia, bone defects, revision surgery
• Technique: Pack graft into joint space after provisional fixation

Definitive Fixation:

• Option A (Screws Alone): Two 6.5 mm or 7.0 mm partially threaded cannulated screws (one from navicular to talar body; one from talar head to navicular)
• Option B (Plate + Screw): Dorsal locking plate + plantar compression screw (biomechanically superior) [12]

Outcomes:

• Union Rate: 85-90% (lower than double arthrodesis)
• Complications: 10-15% non-union rate; residual pain from uncorrected heel valgus
• Modern Practice: Increasingly replaced by double arthrodesis due to superior outcomes

2. Double Arthrodesis (TN + Subtalar) [5,6,13]

The Contemporary Gold Standard for TN Arthritis with Deformity

Rationale:

• Addresses entire hindfoot as mechanical unit
• Permits powerful valgus correction via calcaneal translation
• Higher fusion rates (> 95%) due to larger surface area and stable construct
• Preserves calcaneocuboid joint (lateral column motion and length)
• Equivalent deformity correction to triple arthrodesis with fewer complications [5,13]

Evidence: Prospective comparative studies demonstrate equivalent AOFAS scores and radiographic correction between double and triple arthrodesis, with shorter operative time and lower lateral column pain in double arthrodesis group. [6,13]

Surgical Technique:

Approach:

• Single Medial Incision: Extended longitudinal incision from medial malleolus to naviculocuneiform joint
• Dual Incision: Medial (TN access) + lateral (subtalar access) if significant lateral correction needed

Talonavicular Preparation: (as above)

Subtalar Preparation:

• Access: Either through medial wound extension posteriorly OR separate lateral oblique sinus tarsi incision
• Capsulotomy: Open posterior and middle facets
• Cartilage Removal: Denude all articular surfaces; fish-scale subchondral bone to bleeding bed
• Deformity Correction: Translate calcaneus medially to reduce valgus; evert forefoot to reduce supination

Provisional Fixation: Multiple K-wires to hold entire hindfoot in corrected position

Definitive Fixation: [12]

• TN Joint: Dorsal plate +/- compression screw (as above)
• Subtalar Joint: Two 6.5-7.5 mm screws from calcaneus into talar body (parallel or divergent configuration)
• Alternative: Large-fragment locking plate spanning both joints

Bone Grafting: Recommended for all cases (large surface area to heal)

Outcomes: [5,6,13]

• Union Rate: 95-98%
• AOFAS Hindfoot Score: Mean improvement 35-45 points (pre-op ~45 → post-op 80-85)
• Patient Satisfaction: 85-92% satisfied or highly satisfied
• Return to Activity: 4-6 months for full unrestricted activity

3. Triple Arthrodesis (TN + Subtalar + Calcaneocuboid)

Indications:

• Multi-Level Arthritis: Radiographic or CT evidence of calcaneocuboid arthritis
• Severe Rigid Deformity: Massive valgus collapse requiring three-dimensional correction
• Salvage: Post-traumatic or neuromuscular deformity

Technique: Similar to double arthrodesis but with addition of calcaneocuboid joint fusion

Advantages:

• Most powerful correction of severe deformity
• Addresses all symptomatic Chopart/hindfoot joints

Disadvantages: [13]

• Longer operative time
• Higher non-union rate at CC joint (10-15%)
• Lateral column shortening and stiffness
• Greater long-term ankle arthritis risk

Outcomes:

• Union Rate: 85-90% (lower due to CC non-union)
• Functional Outcomes: Similar to double arthrodesis but higher lateral foot complaints

4. Adjunct Procedures (Commonly Combined)

Gastrocnemius Recession or Achilles Lengthening:

• Indication: Equinus contracture (ankle dorsiflexion less than 10° with knee extended)
• Rationale: Tight gastrocnemius drives forefoot into varus; correcting equinus reduces compensatory midfoot stress

Peroneal Tendon Procedures:

• Peroneus brevis tenodesis (if subluxation or tear)

Medial Malleolar Osteotomy:

• Improve surgical exposure in complex cases
• Reattach with screws at case conclusion

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10. Post-Operative Management

Immobilization Protocol (Standard): [5,11]

Phase 1: Weeks 0-6 (Strict Non-Weight-Bearing):

• Immobilization: Below-knee cast or CAM walker boot
• Weight-Bearing: Strict NWB with crutches or knee scooter
• DVT Prophylaxis: Aspirin 81 mg daily or enoxaparin if high risk
• Elevation: Leg elevated above heart as much as possible
• Wound Care: Suture removal at 2-3 weeks (if dry, healed incision)

Phase 2: Weeks 6-12 (Progressive Weight-Bearing):

• Radiographs: Week 6 X-rays to assess early healing
• Weight-Bearing: Progressive weight-bearing in CAM boot if callus visible
  • "Weeks 6-8: 25-50% WB"
  • "Weeks 8-10: 50-75% WB"
  • "Weeks 10-12: 75-100% WB"
• Physical Therapy: Ankle ROM exercises, gait training

Phase 3: Weeks 12-16 (Return to Shoe):

• Radiographs: Week 12 X-rays to confirm union
  • "Union Criteria: Bridging trabeculae across ≥3 cortices on orthogonal views"
• Footwear: Transition to supportive walking shoe with stiff sole
• Physical Therapy: Strengthening, proprioception, gait normalization

Phase 4: 4-6 Months (Return to Full Activity):

• Gradual return to desired activities
• Avoid high-impact sports indefinitely

Enhanced Recovery Protocols (Surgeon-Dependent):

Some surgeons advocate for:

• Bone Stimulation: Pulsed electromagnetic field (PEMF) or low-intensity pulsed ultrasound (LIPUS) to enhance fusion (limited evidence)
• Teriparatide (PTH): Off-label use in high-risk patients (osteoporosis, smokers) for 6-8 weeks post-op to enhance bone formation

---

11. Complications

Intra-Operative

Neurovascular Injury (less than 1%):

• Saphenous Nerve: Most at risk during medial approach; may cause numbness over dorsomedial foot
• Sural Nerve: Lateral approach for subtalar fusion
• Posterior Tibial Artery/Nerve: Deep to PTT; at risk with aggressive retraction

Fracture:

• Navicular fracture during screw insertion (osteoporotic bone)
• Talar neck stress fracture (excessive screw penetration)

Early Post-Operative (less than 3 Months)

Wound Complications (5-10%): [11,13]

• Delayed Healing: Particularly in RA patients, diabetics, smokers
• Superficial Infection: Cellulitis; treat with oral antibiotics
• Deep Infection: Osteomyelitis; requires surgical debridement, IV antibiotics, potential hardware removal
• Wound Dehiscence: Poor soft tissue envelope; may require flap coverage

Venous Thromboembolism (1-2%):

• DVT, PE (rare)
• Prophylaxis essential: early mobilization, chemoprophylaxis

Late Post-Operative (> 3 Months)

Non-Union (5-15% for isolated TN; less than 5% for double arthrodesis): [11,12]

Definition: Failure to achieve radiographic union by 6 months

Risk Factors:

• Patient: Smoking (RR 3.5), diabetes (RR 2.1), RA (RR 2.5), obesity, poor nutrition
• Surgical: Inadequate cartilage removal, poor bone quality, insufficient fixation, lack of bone graft
• Biological: Avascular necrosis, infection

Presentation: Persistent pain, tenderness over fusion site, hardware loosening on X-ray

Treatment:

• Asymptomatic: Observe (fibrous union may be functional)
• Symptomatic: Revision arthrodesis with autograft, rigid fixation, bone stimulation; consider biologics (BMP-2 off-label)

Malposition (3-5%): [13]

Varus Malunion:

• Cause: Overcorrection of valgus; aggressive lateral translation
• Consequence: Lateral foot overload, pain, stress fractures (5th metatarsal), painful gait
• Prevention: Intra-operative alignment checks with fluoroscopy
• Maxim: "Better to err on the side of slight valgus than any varus"

Residual Valgus:

• Undercorrection of deformity; persistent heel valgus
• Lateral subfibular impingement pain

Excessive Forefoot Abduction:

• Lateral column impingement; calcaneocuboid arthritis

Hardware Complications (5-10%):

Prominence/Irritation:

• Dorsal plate causing shoe irritation
• Treatment: Shoe modification vs. hardware removal after union (> 12 months)

Loosening/Breakage:

• Usually indicates non-union
• Requires revision surgery

Adjacent Segment Disease (10-20% at 10-15 years): [1,8]

Ankle Arthritis:

• Altered biomechanics post-fusion increases tibiotalar contact stress
• Incidence increases with time: ~2% at 5 years, ~10-15% at 10 years, ~20% at 15 years
• Presentation: Anterior ankle pain, decreased dorsiflexion, radiographic joint space narrowing
• Treatment: Conservative (bracing, injection) vs. ankle arthrodesis or arthroplasty

Calcaneocuboid Arthritis:

• Lateral column overload (particularly after triple arthrodesis)
• Less common after double arthrodesis (lateral column preserved)

Naviculocuneiform Arthritis:

• Increased stress at midfoot-forefoot junction

Chronic Pain (5-10%):

Etiologies:

• Incomplete pain relief despite solid fusion (multi-factorial pain generators)
• Adjacent joint arthritis
• Sural neuralgia (lateral approach)
• Complex regional pain syndrome (CRPS)—rare but devastating

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12. Prognosis and Long-Term Outcomes

Functional Outcomes

Patient-Reported Outcome Measures (PROMs): [5,6,13]

AOFAS Hindfoot Score:

• Pre-operative: 40-50 (severe disability)
• Post-operative (2 years): 75-85 (good to excellent function)
• Mean Improvement: 35-40 points

MOXFQ (Manchester-Oxford Foot Questionnaire):

• Significant improvement in pain, walking, and social interaction domains
• Mean post-op scores 25-35 (lower = better; maximum dysfunction = 100)

SF-36 (Quality of Life):

• Improvement in physical function and bodily pain domains
• Mental health scores often unchanged

VAS Pain Scores:

• Pre-operative: 7-8/10
• Post-operative: 2-3/10

Activity Level

Return to Work: [11,13]

• Sedentary: 3-4 months
• Light Duty: 4-6 months
• Heavy Labor: 6-9 months (some patients unable to return)

Recreational Activities:

• Walking: Unlimited (pain-free in 80-85%)
• Hiking: Possible on even terrain; uneven terrain remains challenging
• Running: Generally not recommended; high-impact stress on ankle and adjacent joints
• Sports: Low-impact (golf, swimming) possible; high-impact sports (tennis, basketball) discouraged

Satisfaction Rates

Overall Satisfaction: 85-92% of patients report being satisfied or highly satisfied with surgery [5,6]

Would Repeat Surgery: 88-94% report they would undergo the procedure again

Dissatisfaction Factors:

• Persistent pain (adjacent joint disease, CRPS)
• Stiffness beyond expectations
• Prolonged recovery (many patients underestimate 6-12 month timeline)
• Residual deformity or cosmetic concerns

Long-Term Sequelae

Adjacent Joint Arthritis: See Complications section above

Gait Alterations: [1,8]

• Reduced hindfoot motion compensated by increased ankle and midfoot motion
• Slightly shortened stride length
• Decreased cadence on uneven terrain
• Overall gait efficiency reduced by ~10-15% compared to normal

Contralateral Foot Overload:

• Increased stress on opposite foot may accelerate arthritis

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13. Evidence and Guidelines

Landmark Studies

Astion et al. (1997) - Motion of the Hindfoot After Simulated Arthrodesis: [1]

Study Design: Cadaveric biomechanical study

Key Findings:

• Isolated TN fusion eliminates 90% of subtalar motion (coupled mechanics)
• Isolated subtalar fusion reduces TN motion by only 25%
• Demonstrates biomechanical interdependence justifying double arthrodesis approach

Clinical Implication: Fusing TN joint alone creates a functionally rigid hindfoot; adding subtalar fusion adds minimal additional stiffness but provides deformity control and higher union rates.

Sammarco et al. (2009) - Double Arthrodesis for Adult Acquired Flatfoot: [5]

Study Design: Retrospective case series (N=33 feet, mean follow-up 4.2 years)

Key Findings:

• Mean AOFAS score improvement: 41 (pre-op) → 82 (post-op)
• Union rate: 97% (32/33)
• Significant correction of radiographic parameters (Meary angle, heel valgus)
• Preservation of calcaneocuboid joint (lateral column function)

Clinical Implication: Established double arthrodesis as effective alternative to triple arthrodesis for Stage III/IV PTTD and TN arthritis.

Knupp et al. (2021) - Double vs Triple Arthrodesis Comparative Study: [13]

Study Design: Prospective comparative cohort (N=23, double=13, triple=10, 12-month follow-up)

Key Findings:

• No statistically significant difference in AOFAS scores or radiographic correction between groups
• Both groups achieved 100% union by 4 months
• Mean operative time shorter in double arthrodesis (not statistically significant)
• Equivalent deformity correction

Clinical Implication: Double arthrodesis achieves equivalent outcomes to triple arthrodesis while preserving lateral column; should be preferred unless CC joint is arthritic.

Arbab et al. (2024) - Isolated Talonavicular Arthrodesis Outcomes: [11]

Study Design: Retrospective case series (N=18, mean follow-up 14.5 months)

Key Findings:

• Mean MOXFQ improvement: 65.3 (pre-op) → 28.5 (post-op)
• Non-union rate: 5.6% (1/18 required revision)
• Six-week NWB protocol
• Patient satisfaction high in appropriately selected cases (isolated TN arthritis without deformity)

Clinical Implication: Isolated TN fusion can achieve good outcomes in carefully selected cases with truly isolated arthritis and minimal deformity.

Systematic Reviews and Meta-Analyses

Jung et al. (2015) - Outcomes of Hindfoot Arthrodesis: [20]

Findings:

• Pooled union rate for TN fusion: 88% (isolated), 94% (double arthrodesis)
• Complication rates: 15-25% overall; 8-12% major complications
• Patient satisfaction: 80-90% across all hindfoot arthrodesis procedures

Professional Society Guidelines

American Academy of Orthopaedic Surgeons (AAOS) - Management of Adult Flatfoot:

Recommendations (Strength of Recommendation):

• Weight-bearing radiographs mandatory for diagnosis and surgical planning (Strong)
• Orthotic management should be attempted before surgery in flexible deformities (Moderate)
• Arthrodesis is the preferred surgical treatment for fixed flatfoot with arthritis (Strong)
• Choice between double and triple arthrodesis should be based on extent of arthritis (Moderate)

European Foot and Ankle Society (EFAS) - Hindfoot Arthrodesis:

Consensus Statements:

• Bone grafting recommended for all hindfoot arthrodeses to enhance union rates
• Smoking cessation essential pre-operatively (minimum 6 weeks)
• Post-operative NWB for 6 weeks is standard of care
• Adjacent joint arthritis surveillance recommended long-term

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14. Special Populations

Rheumatoid Arthritis

Pathophysiology: Inflammatory synovitis preferentially targets TN joint; spring ligament enzymatic degradation leads to progressive valgus collapse. [9,10]

Surgical Considerations:

• Poor Bone Quality: Osteopenia, cystic subchondral changes require structural bone grafting
• Wound Healing: Immunosuppressive medications (methotrexate, biologics) may impair healing
  • "Methotrexate: Hold for 2 weeks pre-op and 2 weeks post-op (coordinate with rheumatology)"
  • "Biologics (TNF-α inhibitors): Hold for 1-2 dosing cycles pre-op; resume after wound healed"
• Infection Risk: Slightly elevated (3-5% vs. 1-2% in non-RA)
• Hardware Selection: Locking plates preferred due to poor bone purchase with standard screws

Outcomes: Comparable pain relief and satisfaction to non-RA patients, but higher complication rates (non-union 12-15%, wound complications 8-10%). [10]

Diabetic Patients

Pre-Operative Optimization:

• Glycemic Control: Target HbA1c less than 7% (ideally less than 6.5%) prior to elective surgery
• Vascular Assessment: Palpable pulses mandatory; consider non-invasive vascular studies if questionable perfusion
• Neuropathy Evaluation: Monofilament testing; peripheral neuropathy increases non-union and Charcot risk

Surgical Considerations:

• Extended Immobilization: Consider 8-12 weeks NWB (vs. 6 weeks) due to slower healing
• Bone Grafting: Liberal use of autograft or allograft
• Infection Prophylaxis: Extended antibiotic prophylaxis (24-48 hours post-op)
• Wound Surveillance: Close follow-up for wound breakdown

Outcomes: Higher non-union (10-15%) and infection (5-8%) rates compared to non-diabetics; overall satisfaction similar if complications avoided.

Müller-Weiss Disease

Background: Spontaneous osteonecrosis and fragmentation of navicular (usually lateral aspect) leading to progressive collapse and secondary TN arthritis. [4]

Unique Surgical Considerations:

• Bone Loss: Navicular fragmentation often requires structural bone grafting (tricortical iliac crest) to restore medial column height
• Extended Fusion: Talonavicular-cuneiform fusion (rather than isolated TN) may be needed if navicular bone stock inadequate
• Fixation Challenges: Bridging plates spanning talus to cuneiform bypass fragmented navicular

Outcomes: Good pain relief but higher non-union rates (10-15%) due to poor bone quality; bone grafting essential.

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15. Differential Diagnosis

When evaluating a patient with medial midfoot pain and planovalgus deformity, consider:

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16. Future Directions and Emerging Therapies

Biological Augmentation

Growth Factors:

• BMP-2 (Bone Morphogenetic Protein): Off-label use in high-risk non-unions; concerns about heterotopic ossification and cost
• PRP (Platelet-Rich Plasma): Autologous platelet concentrate applied to fusion site; limited evidence for efficacy in hindfoot fusion
• Stem Cells (Mesenchymal): Bone marrow aspirate concentrate (BMAC); early research shows promise but no high-quality RCTs

Teriparatide (PTH 1-34):

• Off-label use post-operatively in osteoporotic patients to enhance bone formation
• Limited evidence; high cost

Advanced Fixation Technology

Patient-Specific Instrumentation (PSI):

• 3D-printed cutting guides based on pre-operative CT to optimize joint preparation and alignment
• Early studies show improved accuracy but unclear clinical benefit

Intramedullary Devices:

• Hindfoot fusion nails (retrograde calcaneal-talar-tibial rods) for simultaneous ankle + hindfoot fusion
• Primarily used in salvage scenarios (failed prior fusion, AVN, severe deformity)

Motion-Preserving Alternatives

Talonavicular Joint Replacement:

• Theoretical concept; no commercially available implant
• Challenges: Small joint size, complex multi-planar motion, high loads, poor bone stock in arthritic patients
• Currently experimental; unlikely to become clinical reality in near future

Interposition Arthroplasty:

• Soft tissue (tensor fascia lata, dermal allograft) placed between debrided joint surfaces
• Historical reports show high failure rates; not recommended

Predictive Analytics and AI

Machine Learning Models:

• Algorithms to predict non-union risk based on patient factors (smoking, diabetes, bone quality) and surgical variables
• May guide decisions on bone grafting, fixation type, biologics use

Gait Analysis:

• Pre-operative gait labs to predict post-operative functional outcomes
• Identify patients who may not benefit from surgery (central neurological gait disorders, severe hip/knee pathology)

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17. Patient Education and Shared Decision-Making

The Condition Explained

To Patient/Family:

"The talonavicular joint is like the 'universal joint' or 'ball-and-socket' of your foot. It's located deep in the middle of your foot and is responsible for most of the side-to-side tilting motion that allows you to walk on uneven ground like gravel, grass, or cobblestones.

In your case, this joint has worn out—the cartilage (smooth cushion) has broken down, and now the bones are rubbing together. This is causing your deep, aching pain and is why your foot has flattened out and rolled inward.

This wear-and-tear can happen from:

• Years of stress from a weak tendon (posterior tibial tendon)
• Inflammatory arthritis like rheumatoid arthritis that attacks the joint
• An old injury to the foot that never healed properly
• Or sometimes, we don't know why (idiopathic)"

Treatment Options Explained

Conservative (Non-Surgical):

"We can try to manage your pain without surgery using:

1. A rigid brace (Arizona brace) that holds your foot and ankle completely still—like a cast you can take off. This stops the painful motion and helps most people feel better, but it's bulky and you'll need larger shoes.

2. Special shoes with a rocker-bottom sole that reduces stress on the joint.

3. Medications like anti-inflammatories (ibuprofen, naproxen) or acetaminophen for pain.

4. Injections of cortisone into the joint to reduce inflammation—this is temporary relief, usually 3-6 months.

The reality: Bracing works well for about 30-50% of patients long-term. It doesn't fix the problem—it just controls the pain. If you're young, active, or have severe arthritis, bracing often isn't enough."

Surgical (Fusion):

"Surgery involves fusing (permanently stiffening) the worn-out joint. We remove the damaged cartilage, position the bones correctly, and use screws and sometimes a metal plate to hold them together while they heal into one solid bone—like a broken bone healing.

Why fusion? Unlike hip or knee arthritis where we can replace the joint with an artificial one, the talonavicular joint is too small and complex for a replacement. Fusion is the only reliable way to eliminate the pain.

Which joints need to be fused?

We'll do a CT scan to see exactly which joints are worn out:

• Isolated fusion: If only the talonavicular joint is arthritic (rare), we fuse just that one joint.
• Double fusion (RECOMMENDED): We fuse both the talonavicular AND subtalar joints together. Even if the subtalar joint isn't badly worn out, fusing it along with the talonavicular joint gives us better control to correct your foot alignment, has a higher success rate, and doesn't make you any stiffer (since the talonavicular joint controls most of the motion anyway).
• Triple fusion: If the third joint (calcaneocuboid) on the outside of your foot is also arthritic, we fuse all three.

The Surgery: What to Expect

The Operation:

• Duration: 2-3 hours
• Anesthesia: General anesthesia + nerve block (your foot will be numb for 24-48 hours)
• Incision: One or two cuts on the inside (and sometimes outside) of your foot, about 6-8 cm long
• Bone graft: We usually take a small piece of bone from your pelvis or heel to pack into the fusion site to help it heal (adds 15-20 minutes)
• Hospital stay: Usually overnight (23-hour observation) or outpatient same-day surgery

The Recovery (This is the hard part—be prepared):

• Weeks 0-6: Your foot is in a cast or boot and you CANNOT put any weight on it. You'll need crutches or a knee scooter. This is critical—walking on it can cause the fusion to fail.

• Weeks 6-12: We'll take X-rays to check healing. If it's progressing, you can start putting weight on your foot in the boot, gradually increasing over 6 weeks.

• Weeks 12-16: Transition out of the boot into a regular supportive shoe with a stiff sole.

• 4-6 months: Gradual return to normal activities. The bone is usually fully healed by 4-6 months.

The Sacrifice:

• You will lose the side-to-side tilting motion of your foot. It will be stiff.
• Walking on flat, even ground (sidewalks, tile floors) will feel nearly normal.
• Uneven terrain (hiking, gravel, sand) will always be more challenging.
• You won't be able to run or do high-impact sports.

The Gain:

• The deep, aching pain should be 80-90% better or completely gone.
• Your foot will be straight and stable—no more collapsing arch.
• You'll be able to walk without a brace and wear normal shoes.

Risks and Complications

Common (5-15%):

• Non-healing (non-union): The bones don't fuse together. More likely if you smoke, have diabetes, or osteoporosis. May require a second surgery.
• Numbness: The nerve on the inside of your foot may be irritated, causing a numb patch. Usually permanent but not painful.
• Hardware irritation: The screws or plate may poke and require removal after the bone heals (second small surgery).

Uncommon (1-5%):

• Infection: Wound infection requiring antibiotics or surgery to clean it out.
• Blood clot: DVT (leg clot) or PE (lung clot)—rare but serious.
• Malposition: Foot heals in wrong position (too tilted in or out); may need revision surgery.

Long-term (years later):

• Adjacent joint arthritis: The ankle or other joints may wear out faster because they're compensating for the stiff hindfoot. Happens in 10-20% of patients over 10-15 years.

Success Rates

• Pain relief: 85-92% of patients report significant pain improvement.
• Satisfaction: 85-92% would do the surgery again.
• Return to activity: Most patients return to walking, light recreation, and work by 6 months.

Decision-Making Questions

Questions to Ask Yourself:

1. Is my pain severe enough that I'm willing to accept a stiff foot and 3-6 months of recovery?
2. Am I willing and able to be non-weight-bearing on crutches for 6 weeks?
3. Have I given bracing a fair trial (3-6 months)?
4. What are my goals? (Pain relief? Return to work? Hiking? Just walking around the house?)

Red Flags to NOT Have Surgery:

• Very low activity level (bedbound, wheelchair-dependent)
• Severe medical problems making surgery risky
• Active smoking (dramatically increases non-union risk—quit first)
• Unrealistic expectations (expecting to run marathons)

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18. Viva Voce and Examination Preparation

High-Yield Viva Questions

Q1: What percentage of hindfoot motion is lost after isolated talonavicular fusion, and why?

A: Approximately 90% of subtalar joint motion is lost after isolated talonavicular fusion due to the biomechanical coupling between the TN and subtalar joints via Chopart's joint locking mechanism. When the talonavicular joint is rigidly fused, the subtalar joint can no longer function independently due to shared axes of rotation. In contrast, isolated subtalar fusion only reduces talonavicular motion by approximately 25%, demonstrating the dominant role of the TN joint in hindfoot kinematics. [1,8]

Q2: Describe the "acetabulum pedis" and its clinical significance.**

A: The acetabulum pedis is the socket component of the talonavicular ball-and-socket joint. It is a tripartite structure composed of:

1. Navicular proximal articular surface (superior and dorsal coverage)
2. Superomedial calcaneonavicular (spring) ligament (inferior floor and medial support)
3. Sustentaculum tali (medial buttress)

This composite architecture distributes high axial loads (2.5-3× body weight) and permits multidirectional motion. The spring ligament is particularly critical—its failure in PTTD or RA leads to loss of the inferior support, causing the talar head to plantarflex ("sag"), resulting in navicular dorsolateral translation, incongruity, and progressive arthritis. [7,17]

Q3: What is the primary indication for double arthrodesis over triple arthrodesis in talonavicular arthritis?

A: The primary indication is to spare the calcaneocuboid (CC) joint when it is radiographically and clinically non-arthritic. Prospective comparative studies demonstrate that double arthrodesis (TN + subtalar) achieves equivalent deformity correction and functional outcomes to triple arthrodesis (TN + subtalar + CC) while:

• Preserving lateral column length and motion
• Reducing operative time
• Lowering non-union risk (CC joint has highest non-union rate at 10-15%)
• Decreasing lateral foot pain and stiffness

Double arthrodesis is the preferred procedure unless the CC joint shows significant arthritis on pre-operative CT scan. [5,6,13]

Q4: Which structures are at risk during a medial approach to the talonavicular joint?

A:

• Superficial:
  • Great saphenous vein (dorsal to incision)
  • Saphenous nerve (sensory; runs with vein; injury causes dorsomedial foot numbness)
• Deep:
  • Tibialis anterior tendon (dorsal border of exposure; must be retracted dorsally)
  • Tibialis posterior tendon (plantar border; must be retracted plantarly)
  • Posterior tibial neurovascular bundle (deep and plantar; at risk with aggressive retraction)

Surgical Pearl: The interval between tibialis anterior (dorsal) and posterior (plantar) provides safe access to the TN joint capsule.

Q5: Why does the talonavicular joint have a high non-union rate, and how do you optimize fusion?

A: The TN joint has a 10-15% non-union rate (highest among hindfoot joints) due to:

Biomechanical Factors:

• Small contact surface area (~2-3 cm²)
• High shear forces during gait
• Multiplanar motion demands high stability

Biological Factors:

• Frequently poor bone quality (osteopenia in RA, cysts, subchondral sclerosis)
• Tenuous blood supply to navicular (watershed zone)

Optimization Strategies: [11,12]

1. Thorough Joint Preparation: Remove ALL cartilage and sclerotic bone down to bleeding cancellous bone; fish-scale or drill perforations in subchondral bone
2. Bone Grafting: Autologous iliac crest or calcaneal cancellous graft to fill defects and enhance biology
3. Rigid Fixation: Compression screws + dorsal neutralization plate (biomechanically superior to screws alone)
4. Patient Optimization: Smoking cessation (most critical—reduces union by 3.5×), glycemic control, vitamin D repletion
5. Consider Double Arthrodesis: Adding subtalar fusion creates larger surface area and more stable construct (non-union rate less than 5%)

Q6: Explain Chopart's joint locking mechanism and its clinical relevance.

A: Chopart's joint (talonavicular + calcaneocuboid) functions as an adaptive coupling between the hindfoot and midfoot, described by Elftman and Manter: [2]

Heel Inversion (Supination):

• TN and CC joint axes diverge (non-parallel)
• Midfoot becomes rigid and locked
• Creates stable lever arm for push-off during terminal stance

Heel Eversion (Pronation):

• TN and CC joint axes become parallel
• Midfoot becomes flexible and unlocked
• Allows accommodation to ground irregularities during initial contact and loading

Clinical Relevance:

• Explains why TN fusion eliminates subtalar motion (axes locked)
• Rationale for double arthrodesis (fusing both TN and ST creates rigid hindfoot block)
• Loss of this locking mechanism post-fusion explains difficulty on uneven terrain

Q7: What are the radiographic goals for talonavicular fusion alignment?

A:

Coronal Plane (AP view):

• Heel Alignment: Neutral to 5° valgus (NEVER varus—causes lateral overload)
• Talar Head Coverage: > 70% of talar head covered by navicular (reduce subluxation)
• Forefoot Abduction: Restore normal talus–first metatarsal alignment (AP angle 0-10°)

Sagittal Plane (Lateral view):

• Meary's Angle: 0-5° (restore collinearity of talus and first metatarsal)
• Calcaneal Pitch: 20-25° (restore arch height)
• Talar Declination: 20-25° (avoid excessive plantarflexion)

Key Principle: "Better slight valgus than any varus." Varus malunion causes lateral column overload, peroneal tendinitis, 5th metatarsal stress fractures, and painful gait.

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19. Summary and Key Takeaways

Core Concepts

1. Anatomy: The talonavicular joint is the "hip of the foot" (acetabulum pedis), responsible for 80-90% of hindfoot motion.

2. Pathophysiology: Arthritis develops via inflammatory (RA), post-traumatic, or biomechanical (PTTD Stage IV) pathways; all converge on spring ligament failure and medial column collapse.

3. Clinical Presentation: Deep medial midfoot pain worse on uneven ground; planovalgus deformity; "too many toes" sign.

4. Diagnosis: Weight-bearing radiographs mandatory; CT scan for surgical planning to assess adjacent joints and bone quality.

5. Conservative Management: Arizona brace + rocker-bottom shoe; effective in 30-50% but not curative.

6. Surgical Management: Arthrodesis is definitive treatment; double arthrodesis (TN + subtalar) is modern gold standard due to superior deformity control, higher union rates, and CC joint preservation compared to isolated TN or triple fusion.

7. Outcomes: 85-92% satisfaction; significant pain relief and functional improvement; long-term risk of adjacent joint arthritis.

8. Complications: Non-union (5-15% isolated TN, less than 5% double), malposition (avoid varus!), adjacent segment disease.

Exam Pearls

• Motion: TN fusion → 90% loss of ST motion; ST fusion → 25% loss of TN motion
• Fixation: Plate + screw > screws alone for TN fusion
• Double > Triple: Unless CC joint arthritic
• Bone Graft: Mandatory for high-quality fusion
• Alignment: Slight valgus > neutral > varus (never varus!)
• Recovery: 6 weeks NWB, 12 weeks to union, 6 months to full activity

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20. References

1. Astion DJ, Deland JT, Otis JC, Kenneally S. Motion of the hindfoot after simulated arthrodesis. J Bone Joint Surg Am. 1997;79(2):241-246. doi:10.2106/00004623-199702000-00010

2. Elftman H, Manter J. The evolution of the human foot, with especial reference to the joints. J Anat. 1935;70(Pt 1):56-67.

3. Toullec E. Adult flatfoot. Orthop Traumatol Surg Res. 2015;101(1 Suppl):S11-S17. doi:10.1016/j.otsr.2014.07.030

4. Maceira E, Rochera R. Müller-Weiss disease: clinical and biomechanical features. Foot Ankle Clin. 2004;9(1):105-125. doi:10.1016/S1083-7515(03)00153-7

5. Sammarco VJ, Magur EG, Sammarco GJ, Bagwe MR. Arthrodesis of the subtalar and talonavicular joints for correction of symptomatic hindfoot malalignment. Foot Ankle Int. 2006;27(9):661-666. doi:10.1177/107110070602700901

6. Knupp M, Zwicky L, Bolliger L, et al. Double versus triple arthrodesis for adult-acquired flatfoot deformity due to stage III posterior tibial tendon insufficiency: a prospective comparative study of two cohorts. Int Orthop. 2021;45(9):2219-2229. doi:10.1007/s00264-021-05041-1

7. Gazdag AR, Cracchiolo A. Rupture of the posterior tibial tendon. Evaluation of injury of the spring ligament and clinical assessment of tendon transfer and ligament repair. J Bone Joint Surg Am. 1997;79(5):675-681.

8. Suckel A, Muller O, Langenstein P, et al. Talonavicular arthrodesis or triple arthrodesis: peak pressure in the adjacent joints measured in 8 cadaver specimens. Acta Orthop. 2007;78(5):592-597. doi:10.1080/17453670710014248

9. Ljung P, Kaij J, Knutson K, Pettersson H, Rydholm U. Talonavicular arthrodesis in the rheumatoid foot. Foot Ankle. 1992;13(6):313-316. doi:10.1177/107110079201300603

10. Jeng CL, Campbell JT, Tang EY, Cerrato RA, Myerson MS. Tibiotalocalcaneal arthrodesis with bulk femoral head allograft for salvage of large defects in the ankle. Foot Ankle Int. 2013;34(9):1256-1266. doi:10.1177/1071100713488764

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21. Revision History

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