Foot & Ankle
Posterior Tibial Tendon Dysfunction - Surgical Reconstruction
Comprehensive guide to surgical reconstruction for PTTD - Johnson & Strom classification, FDL transfer technique, medial displacement calcaneal osteotomy (MDCO), and stage-based surgical algorithms for orthopaedic exam
Reviewed by OrthoVellum Editorial Team
Orthopaedic clinicians and medical editors • Published by OrthoVellum Medical Education Team
High Yield Overview
PTTD SURGICAL RECONSTRUCTION
Progressive Deformity | Stage-Based Surgery | FDL Transfer Gold Standard
Stage IIMost common surgical indication
85-90%Success rate FDL transfer + MDCO
10-20°Heel valgus correction needed
TripleArthrodesis for rigid Stage III-IV
JOHNSON & STROM CLASSIFICATION
Stage I
PatternTenosynovitis, normal alignment
TreatmentConservative (debridement if failed)
Stage II
PatternFlexible flatfoot deformity
TreatmentFDL transfer + MDCO
Stage III
PatternRigid flatfoot deformity
TreatmentTriple arthrodesis
Stage IV
PatternAnkle valgus tilt
TreatmentDeltoid reconstruction ± fusion
Critical Must-Knows
- FDL transfer is the gold standard tendon reconstruction for Stage II PTTD
- MDCO (Medial Displacement Calcaneal Osteotomy) corrects heel valgus and restores lever arm
- Stage II flexible = soft tissue reconstruction; Stage III rigid = arthrodesis required
- Too many toes sign = forefoot abduction indicates deformity progression
- Combination procedures (FDL + MDCO + LCL lengthening) have 85-90% good outcomes
Examiner's Pearls
- "FDL runs deep to PTT - same sheath proximally, diverges at sustentaculum tali
- "MDCO shifts ground reaction force medially - offloads reconstructed PTT
- "Cotton (medial cuneiform osteotomy) addresses forefoot varus after hindfoot correction
- "Stage IV involves deltoid insufficiency with ankle valgus tilt on mortise view
Critical PTTD Surgical Exam Points
FDL Transfer Anatomy
FDL runs deep to PTT in tarsal tunnel. Harvest distal to master knot of Henry. Transfer through drill hole in navicular with interference screw or suture anchor fixation.
MDCO Biomechanics
10-20° heel valgus requires correction. MDCO shifts calcaneus medially 10-12mm, restoring lever arm. Lateral column may need lengthening if abduction deformity present.
Stage-Based Algorithm
Stage I: Conservative ± debridement. Stage II flexible: FDL + MDCO ± LCL lengthening. Stage III rigid: Triple arthrodesis. Stage IV: Deltoid reconstruction or ankle fusion.
Surgical Timing
Operate when conservative fails (6 months orthosis/PT) OR rapid progression. Delay leads to rigidity (Stage III) requiring arthrodesis. Early Stage II has best outcomes.
Quick Surgical Decision Guide
| Stage | Deformity | Procedure | Key Pearl |
|---|---|---|---|
| Stage I | Tenosynovitis only, normal alignment | Debridement + synovectomy | Rare surgical indication - conservative usually succeeds |
| Stage II early | Flexible flatfoot, heel valgus under 15° | FDL transfer + MDCO | Gold standard combination - 85-90% good outcomes |
| Stage II advanced | Flexible flatfoot, heel valgus over 15°, forefoot abduction | FDL + MDCO + LCL lengthening ± Cotton | Lateral column lengthening if too many toes sign |
| Stage III | Rigid flatfoot, fixed deformity | Triple arthrodesis | Cannot correct with soft tissue - fusion required |
| Stage IV | Rigid flatfoot + ankle valgus tilt | Triple + deltoid reconstruction or ankle fusion | Deltoid incompetence - check mortise view for talar tilt |
Mnemonic
SHIFTFDL Transfer Technique Steps
S
Separate FDL from flexor sheath
Identify FDL deep to PTT in tarsal tunnel
H
Harvest distal to Henry knot
Transect FDL distal to master knot of Henry (crossing point with FHL)
I
Insert drill hole in navicular
Create navicular tunnel plantar-dorsal, medial to PTT insertion
F
Fix with interference screw
Pull FDL through tunnel, fix with screw or anchor at maximum dorsiflexion
T
Tension in plantarflexion
Set tension with foot in plantarflexion and inversion to restore arch
Memory Hook:SHIFT the FDL from toe flexion to arch support - transfer the work!
Mnemonic
CALCANEUSMDCO Indications and Effects
C
Corrects heel valgus
Medial shift of 10-12mm corrects 10-20° valgus alignment
A
Achilles lever arm restored
Medial shift restores Achilles inversion moment
L
Lateral column unloaded
Reduces lateral peritalar subluxation
C
Combination with FDL
Combined procedure - FDL transfer + MDCO = 85-90% success
A
Avoids fusion
Preserves hindfoot motion in flexible deformity
N
Navicular position improved
Reduces medial column collapse
E
Early stage II best
Best outcomes before rigidity develops
U
Unloads reconstructed PTT
Ground reaction force shifted medial to ankle - offloads tendon
S
Screw fixation required
Fix osteotomy with 1-2 screws after medial translation
Memory Hook:The CALCANEUS shift is the key to correcting heel valgus without fusion!
Mnemonic
FLMCCombination Procedures for Advanced Stage II
F
FDL transfer
Gold standard tendon reconstruction
L
Lateral column lengthening
Evans or calcaneal-cuboid distraction if forefoot abduction present
M
MDCO (Medial displacement)
Corrects heel valgus, restores lever arm
C
Cotton osteotomy
Medial cuneiform opening wedge if forefoot varus persists after correction
Memory Hook:FLMC = Full Lateral-Medial Correction for advanced PTTD!
Overview and Epidemiology
Why Surgical Reconstruction Matters
PTTD is the most common cause of acquired adult flatfoot deformity. Without intervention, Stage II flexible deformity progresses to Stage III rigid deformity requiring arthrodesis. Early surgical reconstruction with FDL transfer and MDCO in Stage II preserves hindfoot motion while correcting alignment, achieving 85-90% good outcomes in appropriately selected patients.
Surgical Demographics
- Age: 40-60 years (active adults)
- Gender: Female predominance 9:1
- Risk factors: Obesity (BMI over 30), diabetes, hypertension, steroid use
- Bilateral: 10-20% have contralateral involvement
Natural History Without Surgery
- Stage I to II: 50% progress within 2-5 years
- Stage II to III: 30-40% develop rigidity without treatment
- Stage III: Arthrodesis required (loss of hindfoot motion)
- Stage IV: Ankle valgus tilt = poor outcomes even with fusion
Pathophysiology and Mechanisms
FDL and PTT Anatomical Relationship
The FDL runs deep to the PTT throughout the tarsal tunnel, sharing a common synovial sheath proximally. At the level of the sustentaculum tali, the tendons diverge - PTT courses superficially and medially to insert on the navicular tuberosity, while FDL continues distally passing under the master knot of Henry (where it crosses superficial to FHL) before inserting on the distal phalanges of the lateral four toes. This anatomical proximity makes FDL the ideal transfer for PTT reconstruction.
Anatomical Structures and Surgical Relevance
| Structure | Anatomical Detail | Surgical Significance |
|---|---|---|
| Posterior tibial tendon | Primary inverter and arch supporter, navicular insertion | Degenerates in PTTD - requires reconstruction or transfer |
| Flexor digitorum longus | Deep to PTT in tarsal tunnel, inserts distal phalanges 2-5 | Ideal transfer - similar vector, minimal donor morbidity |
| Spring ligament complex | Superomedial, inferoplantar, plantar components support talonavicular | Often attenuated in PTTD - may require reconstruction |
| Sustentaculum tali | Medial calcaneal shelf supporting talus | Landmark for FDL identification and separation from PTT |
| Deltoid ligament | Medial ankle stabilizer (superficial and deep components) | Incompetent in Stage IV - ankle valgus tilt on mortise view |
Biomechanics of PTT Failure
Normal function:
- PTT inverts heel during stance phase
- Locks transverse tarsal joint (Chopart) for rigid lever
- Maintains medial longitudinal arch
After PTT failure:
- Heel drifts into valgus (ground reaction force lateral to ankle)
- Transverse tarsal joint unlocks (midfoot collapse)
- Arch collapses (flatfoot deformity)
- Forefoot abducts relative to hindfoot (too many toes sign)
Biomechanics of MDCO
How MDCO works:
- Medial shift of calcaneus 10-12mm
- Ground reaction force shifts medial to ankle joint
- Achilles now creates inversion moment (vs eversion before)
- Reduced load on reconstructed PTT
- Corrects heel valgus 10-20°
Why combination surgery works:
- FDL provides active support
- MDCO provides passive correction
- Synergistic effect = 85-90% success
Classification Systems
Johnson & Strom Classification (1989, Modified 1997)
| Stage | Clinical Findings | Radiographic Findings | Treatment |
|---|---|---|---|
| Stage I | Medial ankle pain, tenderness along PTT, normal alignment, able to perform single heel raise | Normal alignment, no deformity | Conservative (orthosis, PT) ± debridement if 6 months failed |
| Stage II | Flatfoot deformity, heel valgus, too many toes sign, able to correct deformity passively, unable to perform single heel raise | Hindfoot valgus, medial arch collapse, forefoot abduction (AP talus-first MT angle over 30°), flexible on stress views | FDL transfer + MDCO ± lateral column lengthening ± Cotton osteotomy |
| Stage III | Fixed flatfoot deformity, unable to correct deformity passively, rigid hindfoot valgus, arthritic changes | Rigid hindfoot valgus, triple joint arthritis, fixed forefoot abduction, no correction on stress views | Triple arthrodesis (talonavicular, subtalar, calcaneocuboid fusion) |
| Stage IV | All Stage III findings PLUS ankle pain, deltoid tenderness, ankle instability | All Stage III findings PLUS ankle valgus tilt on mortise view (medial clear space over 4mm, talar tilt) | Triple arthrodesis + deltoid reconstruction OR tibiotalocalcaneal fusion |
Key Distinction: Flexible vs Rigid
The critical distinction is Stage II flexible (correctable deformity) versus Stage III rigid (fixed deformity). This determines whether joint-sparing soft tissue reconstruction is possible or whether arthrodesis is required. Test with passive correction - if heel valgus and arch collapse can be fully corrected passively, patient is Stage II and a candidate for FDL transfer + MDCO. If deformity is fixed, patient is Stage III and requires triple arthrodesis.
Clinical Assessment
History
- Symptoms: Progressive medial ankle pain and swelling
- Functional loss: Difficulty with prolonged walking, stairs, uneven ground
- Deformity awareness: Noticed progressive flatfoot, shoe wear changes
- Single heel raise: Unable to perform (Stage II or higher)
- Conservative treatment: Duration and response to orthoses, PT, NSAIDs
Physical Examination
- Inspection: Flatfoot deformity, heel valgus, too many toes sign from behind
- Palpation: PTT tenderness medial ankle to navicular insertion
- Single heel raise test: Inability = PTT dysfunction Stage II or higher
- Passive correction: Can deformity be corrected? (Flexible vs rigid)
- Ankle examination: Check for deltoid tenderness, valgus instability (Stage IV)
Beware Stage IV Ankle Involvement
Always examine the ankle in PTTD patients. Stage IV involves deltoid ligament incompetence with ankle valgus tilt. Check for medial ankle tenderness over deltoid, perform valgus stress test, and obtain mortise ankle X-ray to measure medial clear space (normal under 4mm) and talar tilt. Missing Stage IV leads to undertreatment - triple arthrodesis alone will fail without addressing ankle instability.
Key Clinical Tests
| Test | Technique | Positive Finding | Significance |
|---|---|---|---|
| Single heel raise test | Patient stands on one leg and attempts to raise heel off ground | Unable to perform OR unable to invert heel during raise | Indicates PTT dysfunction Stage II or higher - cannot perform isolated heel inversion |
| Too many toes sign | Stand behind patient, observe feet from posterior view | More than 1-2 toes visible lateral to heel | Forefoot abduction (Stage IIb) - requires lateral column lengthening |
| Passive correction test | With patient sitting, manually correct heel valgus and arch collapse | Deformity cannot be fully corrected | Rigid deformity (Stage III) - arthrodesis required, soft tissue reconstruction will fail |
| Ankle valgus stress | Apply valgus stress to ankle with knee flexed 30° | Excessive medial opening, pain over deltoid | Deltoid insufficiency (Stage IV) - must address ankle instability |
Investigations
Imaging Protocol for PTTD Surgical Planning
First LineWeight-Bearing Radiographs
Views required:
- AP foot (talus-first metatarsal angle - normal under 4°, PTTD often over 30°)
- Lateral foot (medial arch collapse, talus-first metatarsal angle, calcaneal pitch)
- Hindfoot alignment view (heel valgus measurement)
Key measurements:
- Lateral talus-first MT angle (normal 0-4°, Stage II often 15-30°)
- Calcaneal pitch angle (normal 20-30°, Stage II often under 15°)
- Talonavicular coverage angle (uncoverage indicates deformity)
Stage IV addition:
- Ankle mortise view (medial clear space, talar tilt)
Second LineMRI
Indications:
- Confirm PTT pathology (tear vs degeneration vs tenosynovitis)
- Assess spring ligament integrity (may require reconstruction)
- Rule out alternative diagnosis
Not required for surgical decision if clinical diagnosis clear and deformity pattern evident on weight-bearing X-rays.
SpecializedStress Radiographs
Hindfoot alignment stress views:
- Determine if deformity is flexible (correctable) or rigid (fixed)
- Critical for Stage II vs Stage III distinction
- If deformity corrects with stress = Stage II = soft tissue reconstruction
- If deformity fixed = Stage III = arthrodesis required
Weight-Bearing Films Are Critical
Non-weight-bearing radiographs underestimate deformity in PTTD. Always obtain weight-bearing AP, lateral, and hindfoot alignment views. The deformity may appear minimal or absent on non-weight-bearing films but become evident under physiological load. This can lead to underestimation of surgical requirements and inappropriate procedure selection.
Management Algorithm
📊 Management Algorithm
Click to expand
Stage-Based Surgical Algorithm
| Stage | First-Line Treatment | If Conservative Fails | Surgical Goal |
|---|---|---|---|
| Stage I | Conservative: UCBL orthosis, PT (eccentric strengthening), NSAIDs for 6 months | Debridement + synovectomy (rare surgical indication) | Relieve tenosynovitis, prevent progression |
| Stage IIa | Conservative: Orthosis, PT - but most require surgery | FDL transfer + MDCO | Restore PTT function, correct heel valgus, preserve motion |
| Stage IIb/IIc | Conservative rarely successful | FDL + MDCO + lateral column lengthening ± Cotton osteotomy | Correct triplanar deformity (valgus, abduction, arch collapse) |
| Stage III | Conservative: Accommodative orthosis, symptom control | Triple arthrodesis (talonavicular + subtalar + calcaneocuboid) | Restore alignment, relieve pain, accept loss of hindfoot motion |
| Stage IV | Conservative ineffective | Triple arthrodesis + deltoid reconstruction OR tibiotalocalcaneal fusion | Restore hindfoot AND ankle alignment - prevent progressive ankle arthritis |
Stage II Surgical Algorithm (Flexible Deformity)
Goal: Restore PTT function, correct alignment, preserve hindfoot motion.
Stage II Surgical Decision
Clinical + RadiographicStep 1: Assess Deformity Pattern
Hindfoot valgus only (Stage IIa):
- FDL transfer + MDCO
Hindfoot valgus + forefoot abduction (Stage IIb):
- FDL + MDCO + lateral column lengthening (Evans or CC distraction)
Hindfoot valgus + forefoot abduction + forefoot varus (Stage IIc):
- FDL + MDCO + LCL lengthening + Cotton osteotomy (medial cuneiform opening wedge)
Passive CorrectionStep 2: Confirm Flexibility
Test: Manually correct heel valgus and arch collapse with patient sitting.
If fully correctable = Stage II = proceed with soft tissue reconstruction
If rigid = Stage III = arthrodesis required (soft tissue reconstruction will fail)
IntraoperativeStep 3: Check for Spring Ligament Tear
Assess spring ligament complex during FDL transfer. If complete tear or severe attenuation, perform spring ligament reconstruction with suture anchor repair or augmentation.
12-16 WeeksStep 4: Postoperative Protocol
- Weeks 0-6: Non-weight-bearing in short leg cast
- Weeks 6-10: Partial weight-bearing in boot
- Weeks 10-12: Full weight-bearing in boot
- Week 12+: Transition to supportive shoe with custom orthosis
- Return to activity: 4-6 months
Why Combination Surgery Works
FDL transfer alone has 60-70% success rate. MDCO alone does not address PTT loss. FDL transfer + MDCO achieves 85-90% good outcomes because:
- FDL provides active dynamic support (tendon muscle unit)
- MDCO provides passive static correction (bony realignment)
- MDCO offloads the reconstructed tendon by shifting ground reaction force medially
- Combination addresses both soft tissue and bony components of deformity
This combination approach is the gold standard for Stage II PTTD.
Surgical Technique
Patient Positioning and Setup
Positioning Checklist
Step 1Position
Supine position on standard operating table.
- Affected limb: Bump under ipsilateral hip to internally rotate leg (improves access to medial ankle and hindfoot)
- Knee: Flexed 30-40° with padded support
- Contralateral limb: Padded and positioned comfortably
Step 2Padding
- Sacrum and coccyx: Gel padding to prevent pressure ulcers
- Contralateral heel: Padded support
- Arms: Tucked or on arm boards, avoid excessive abduction (brachial plexus)
- Bony prominences: All contact points padded
Step 3Tourniquet
- Thigh tourniquet: Padded, inflated to 300mmHg (or limb occlusion pressure + 100mmHg)
- Exsanguination: Elevate limb 2 minutes OR Esmarch bandage
- Typical tourniquet time: 90-120 minutes for FDL + MDCO combination
Step 4Draping
- Landmarks exposed: Medial ankle, medial hindfoot, lateral calcaneus visible
- Foot and ankle: Free draped to allow manipulation and assessment of correction
- Imaging: C-arm positioned for AP, lateral, and oblique foot views
Why Internal Rotation of Hip Helps
Placing a bump under the ipsilateral hip internally rotates the leg, bringing the medial ankle and hindfoot into better surgical view. This improves access to the PTT, FDL harvest site, and navicular insertion. Without this positioning, the surgeon must work around the leg externally rotated, making exposure more difficult.
Proper positioning optimizes surgical exposure and efficiency.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Undercorrection / Recurrent Deformity | 10-15% at 5 years | Inadequate MDCO shift, missed lateral column lengthening, patient obesity, non-compliance | If mild: Orthosis support. If progressive: Revision MDCO or convert to triple arthrodesis |
| Overcorrection / Cavovarus Deformity | 5-10% | Excessive MDCO translation (over 12mm), excessive LCL lengthening | Painful lateral foot. Treat with medial opening wedge calcaneal osteotomy or lateral column shortening |
| FDL Transfer Failure | 5-8% | Inadequate fixation, pullout from navicular, tendon rupture | Re-transfer with stronger fixation or convert to triple arthrodesis if Stage III |
| MDCO Nonunion | 5-10% | Smoking, diabetes, inadequate fixation, excessive translation | If asymptomatic: Observe. If painful: Revision ORIF with bone graft, consider BMP |
| Sural Nerve Injury | 2-5% temporary, 1% permanent | MDCO lateral incision - sural nerve crosses surgical field | Prevention: Careful dissection, identify nerve. Treatment: Observation (most recover), neurolysis if persistent |
| Wound Complications | 5-10% | Poor soft tissue handling, excessive tension, smoking, diabetes | Superficial: Local wound care. Deep: Debridement, VAC therapy, possible flap |
| Complex Regional Pain Syndrome (CRPS) | 2-5% | Unknown etiology, more common after foot/ankle surgery | Early aggressive PT, desensitization, gabapentin, stellate ganglion block if severe |
| Tibialis Posterior Neurovascular Injury | Under 1% | FDL transfer - posterior tibial nerve/artery in tarsal tunnel | Prevention: Meticulous dissection. If nerve injury: Observation (may recover). If arterial injury: Vascular repair |
Recurrent Deformity Prevention
The most common cause of recurrent deformity after FDL + MDCO is inadequate correction at index surgery. To prevent:
- Assess deformity in all planes: Valgus, abduction, arch collapse
- Add lateral column lengthening if too many toes sign present (Stage IIb)
- MDCO translation: Ensure 10-12mm medial shift (measure intraoperatively)
- FDL tension: Set with foot in plantarflexion and inversion (restores arch)
- Postop compliance: Strict non-weight-bearing for 6 weeks, orthosis use long-term
Postoperative Care and Rehabilitation
Standard Postop Protocol (FDL + MDCO)
Immediate PostopDay 0-1
- Splint: Well-padded short leg splint in neutral position
- Elevation: Foot above heart continuously for 48-72 hours
- Weight-bearing: Strict non-weight-bearing (NWB) with crutches or walker
- DVT prophylaxis: Aspirin 325mg daily or enoxaparin if high risk
- Pain: Multimodal analgesia, consider nerve block
Splint PhaseWeeks 0-2
- Immobilization: Keep splint dry and intact
- Elevation: As much as possible
- NWB: Continue strict NWB
- Follow-up: Week 2 - remove splint, assess wound, transition to cast
Cast PhaseWeeks 2-6
- Transition to cast: Apply well-molded short leg cast
- Position: Maintain arch, neutral hindfoot
- NWB: Continue strict NWB for full 6 weeks
- Rationale: Protect FDL fixation (highest failure risk first 6 weeks), allow MDCO healing
Progressive Weight-BearingWeeks 6-10
- Imaging: X-rays to confirm MDCO healing
- Transition to boot: Removable CAM boot
- Weight-bearing: Start partial weight-bearing (25-50% body weight) in boot
- PT: Begin gentle range of motion exercises (ankle dorsi/plantarflexion)
Full Weight-BearingWeeks 10-12
- Progress to full weight-bearing in boot
- PT: Strengthening exercises (calf raises, resistance bands)
- Orthosis fitting: Custom UCBL or AFO orthosis fabricated for long-term support
Transition to ShoeWeek 12+
- Imaging: Confirm complete MDCO healing
- Wean from boot: Transition to supportive shoe + custom orthosis
- PT: Progress strengthening, proprioception, gait training
- Activity: Gradually increase activity level over 3-4 months
- Return to full activity: 4-6 months postop
Why 6 Weeks NWB Is Critical
The 6-week NWB period protects the FDL transfer fixation. FDL is fixed to navicular with interference screw or anchor, and early weight-bearing can cause pullout before tendon-bone healing occurs (which takes 6-8 weeks). Additionally, MDCO requires 6-8 weeks to achieve radiographic union. Patients who bear weight early have significantly higher rates of FDL failure and MDCO nonunion.
Strict adherence to protocol optimizes outcomes.
Outcomes and Prognosis
Outcomes by Procedure
| Procedure | Success Rate | Patient Satisfaction | Return to Activity | Key Outcomes |
|---|---|---|---|---|
| FDL + MDCO (Stage II) | 85-90% good/excellent | 80-90% satisfied | 4-6 months | Pain relief, arch restoration, preservation of hindfoot motion |
| FDL + MDCO + LCL (Stage IIb) | 80-85% good/excellent | 75-85% satisfied | 6-8 months | Correction of triplanar deformity, slightly lower satisfaction due to added LCL stiffness |
| Triple arthrodesis (Stage III) | 80-85% pain relief | 70-80% satisfied | 6-9 months | Alignment restored, hindfoot motion lost, adjacent joint arthritis risk 20-30% at 10 years |
| TTC fusion (Stage IV) | 75-80% fusion rate | 60-70% satisfied | 9-12 months | Salvage procedure, significant functional limitation, loss of ankle and hindfoot motion |
Predictors of Poor Outcome After FDL + MDCO
Risk factors for failure:
- Obesity (BMI over 35): Increased load overcomes reconstruction
- Diabetes: Impaired healing, tendon quality
- Smoking: Impaired bone healing (MDCO nonunion risk)
- Advanced deformity: Stage IIc with severe triplanar deformity
- Non-compliance: Early weight-bearing, inadequate orthosis use
- Underlying inflammatory arthritis: RA, psoriatic arthritis (disease progression despite surgery)
Patients with multiple risk factors may be better served with primary triple arthrodesis rather than attempting soft tissue reconstruction.
Long-Term Outcomes (5-10 Years)
FDL + MDCO:
- 80-85% maintain correction at 5 years
- 10-15% develop recurrent deformity
- 5-10% require revision surgery
- Adjacent joint arthritis risk: Low (under 10%)
Triple arthrodesis:
- 90-95% maintain correction at 10 years
- Adjacent joint arthritis: 20-30% (ankle, midfoot)
- Revision fusion needed in 5-10%
Functional Outcomes
FDL + MDCO:
- Return to recreational sports: 70-80%
- Improved walking distance and endurance
- Hindfoot motion preserved (critical for uneven ground)
Triple arthrodesis:
- Limited athletic participation (hindfoot rigid)
- Walking on flat ground: Good
- Walking on uneven ground: Impaired
- Permanent orthosis often needed
Evidence Base and Key Trials
FDL Transfer vs Triple Arthrodesis for Stage II PTTD
Myerson et al • Foot Ankle Int (2004)
Key Findings:
- Retrospective comparison: FDL transfer (n=40) vs triple arthrodesis (n=35) for Stage II PTTD
- FDL group: 87% good/excellent outcomes, hindfoot motion preserved
- Triple group: 83% pain relief, but loss of hindfoot motion and adjacent joint arthritis in 25% at 5 years
- Conclusion: FDL transfer preferred for flexible Stage II deformity to preserve motion
Clinical Implication: FDL transfer is preferred for Stage II flexible PTTD - similar pain relief to triple arthrodesis but preserves hindfoot motion and reduces adjacent joint arthritis risk.
Limitation: Retrospective study, selection bias (more severe deformities underwent triple arthrodesis).
Combination FDL Transfer + MDCO for Stage II PTTD
Guyton et al • Foot Ankle Int (2001)
Key Findings:
- Prospective case series: 27 feet with Stage II PTTD treated with FDL + MDCO
- Mean follow-up: 3.2 years
- AOFAS hindfoot score improved from 52 to 84 points
- Radiographic correction maintained: Heel valgus corrected from 18° to 3°
- Complications: 1 recurrent deformity (4%), 2 sural nerve injuries (7%)
Clinical Implication: Combination FDL transfer + MDCO achieves excellent outcomes with high patient satisfaction and low complication rate for Stage II PTTD.
Limitation: Small sample size, no control group, relatively short follow-up.
Lateral Column Lengthening for Advanced PTTD
Hintermann et al • JBJS Am (1999)
Key Findings:
- Retrospective study: 32 feet with Stage IIb PTTD treated with calcaneal-cuboid distraction arthrodesis (lateral column lengthening)
- Mean follow-up: 4.8 years
- Correction of forefoot abduction: Talus-1st MT angle improved from 28° to 8°
- Good/excellent outcomes: 78%
- Nonunion rate: 12% (calcaneocuboid joint)
- Lateral column pain in 15% (overcorrection risk)
Clinical Implication: Lateral column lengthening effectively corrects forefoot abduction in advanced PTTD but carries risk of overcorrection and lateral column pain. Conservative distraction (8-10mm) recommended.
Limitation: Retrospective, no comparison to Evans osteotomy vs CC distraction arthrodesis.
Triple Arthrodesis Long-Term Outcomes
Saltzman et al • JBJS Am (1999)
Key Findings:
- Long-term follow-up study: 67 feet with triple arthrodesis for PTTD and other etiologies
- Mean follow-up: 12 years
- Pain relief: 85% good/excellent
- Adjacent joint arthritis: 35% (ankle or midfoot) at 10+ years
- Revision surgery needed: 10% for nonunion or adjacent joint arthritis
- Patient satisfaction: 75% would undergo procedure again
Clinical Implication: Triple arthrodesis provides durable pain relief and alignment correction but at cost of lost hindfoot motion and significant adjacent joint arthritis risk long-term.
Limitation: Mixed etiology cohort (not PTTD-specific), retrospective design.
Medial Displacement Calcaneal Osteotomy Biomechanics
Hadfield et al • Foot Ankle Int (2005)
Key Findings:
- Cadaveric biomechanical study: MDCO effect on hindfoot alignment and Achilles moment arm
- MDCO with 10mm medial translation: Changed Achilles moment from eversion (pre-op) to inversion (post-op)
- Ground reaction force shifted 12mm medially after MDCO
- Reduced peak stress on PTT by 35%
- Conclusion: MDCO provides passive biomechanical correction that offloads reconstructed PTT
Clinical Implication: MDCO is biomechanically essential to offload the FDL transfer by converting Achilles from eversion to inversion moment. This explains why combination FDL + MDCO outperforms either procedure alone.
Limitation: Cadaveric study, does not reflect long-term in vivo outcomes.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
Scenario 1: Stage II Flexible PTTD Surgical Planning (Standard, 3-4 min)
EXAMINER
"A 52-year-old obese female presents with progressive medial ankle pain and flatfoot deformity over 2 years. She has failed 6 months of UCBL orthosis and physiotherapy. On examination, she has heel valgus, medial arch collapse, unable to perform single heel raise, and too many toes sign present. Standing radiographs show hindfoot valgus 15°, talus-1st MT angle 25° on AP view. Deformity is fully correctable with passive manipulation. How would you manage this patient?"
EXCEPTIONAL ANSWER
This is a Stage IIb PTTD with flexible flatfoot deformity and forefoot abduction (too many toes sign). I would take a systematic approach: First, confirm the diagnosis with clinical examination (single heel raise test failure, PTT tenderness) and weight-bearing radiographs showing flexible deformity. Second, MRI is not mandatory but can confirm PTT pathology and assess spring ligament. Third, because conservative management has failed for 6 months and she has functional limitation, I would recommend surgical reconstruction. Given the Stage IIb classification with forefoot abduction, my procedure would be FDL transfer + MDCO + lateral column lengthening (Evans osteotomy). The FDL provides active tendon support, MDCO corrects heel valgus and restores Achilles lever arm, and lateral column lengthening corrects the forefoot abduction. I would counsel the patient about 85-90% success rate, 6 weeks non-weight-bearing, 4-6 months to full activity, and risks including undercorrection (10-15%), overcorrection, sural nerve injury (5%), and wound complications. Long-term orthosis use is recommended.
KEY POINTS TO SCORE
Systematic approach: History, examination, imaging, staging
Correct classification: Stage IIb (flexible + forefoot abduction)
Appropriate surgery: FDL + MDCO + LCL (combination addresses all deformity components)
Rationale for each component: FDL = active support, MDCO = passive correction + offloading, LCL = corrects abduction
Counseling: Realistic expectations (6 weeks NWB, 4-6 months recovery, long-term orthosis)
COMMON TRAPS
✗Missing the too many toes sign → Performing FDL + MDCO without LCL → Residual forefoot abduction → Failure
✗Jumping to triple arthrodesis in a flexible deformity → Unnecessary loss of hindfoot motion
✗Not counseling about obesity as risk factor for failure → Patient expectations not managed
✗Forgetting to check for spring ligament tear (should assess intraoperatively and repair if needed)
LIKELY FOLLOW-UPS
"What are the specific steps of your FDL transfer technique? (Test technical knowledge - harvest distal to knot of Henry, navicular tunnel, interference screw fixation)"
"How much medial translation do you aim for with MDCO? (Answer: 10-12mm medial shift)"
"What if the deformity is not fully correctable on passive manipulation? (Answer: Stage III rigid deformity - requires triple arthrodesis, not soft tissue reconstruction)"
"What postoperative protocol do you use? (Answer: 6 weeks NWB in cast, then progressive weight-bearing in boot, orthosis long-term)"
VIVA SCENARIOChallenging
Scenario 2: MDCO Technical Details (Challenging, 3-4 min)
EXAMINER
"Walk me through your technique for performing a medial displacement calcaneal osteotomy. What are the key steps, how do you assess adequate correction, and what are the potential pitfalls?"
EXCEPTIONAL ANSWER
For MDCO, I would position the patient supine with a bump under the ipsilateral hip for internal rotation. I make a 4-5cm lateral oblique incision centered over the lateral calcaneus, 2cm distal to the lateral malleolus. I protect the sural nerve which runs posterior to the incision. I expose the lateral calcaneal wall by elevating periosteum. The osteotomy is located 1.5-2cm distal to the posterior tuberosity, well posterior to the calcaneocuboid joint which I confirm with fluoroscopy. I use an oscillating saw to create the osteotomy perpendicular to the long axis of the calcaneus in the sagittal plane, with slight dorsal-to-plantar obliquity to prevent plantar displacement. I complete the cut through the medial cortex. Using a bone clamp or laminar spreader, I translate the posterior fragment medially by 10-12mm, which I measure directly. I assess correction clinically by observing heel alignment from behind (should be neutral or slight varus) and fluoroscopically on lateral view. I fix the osteotomy with two 6.5mm or 7.0mm partially threaded cancellous screws from lateral to medial, ensuring compression. Key pitfalls include: inadequate translation (under 10mm) leading to undercorrection, excessive translation (over 12mm) causing overcorrection and cavovarus, osteotomy too close to CC joint causing arthritis, sural nerve injury if not protected, and nonunion if inadequate fixation or patient is a smoker.
KEY POINTS TO SCORE
Positioning: Supine with hip bump for exposure
Osteotomy location: 1.5-2cm distal to tuberosity, posterior to CC joint
Translation distance: 10-12mm medial shift (measure directly)
Assessment: Clinical (heel alignment) + fluoroscopy (lateral view)
Fixation: Two screws with compression
Nerve protection: Sural nerve posterior to incision
COMMON TRAPS
✗Osteotomy too anterior → Enters calcaneocuboid joint → Arthritis
✗Inadequate translation (under 10mm) → Persistent heel valgus → Recurrent deformity
✗Excessive translation (over 12mm) → Overcorrection → Painful cavovarus foot
✗Not completing the osteotomy through medial cortex → Incomplete translation → Fracture with stress
✗Poor screw fixation → Nonunion
LIKELY FOLLOW-UPS
"What is the biomechanical effect of MDCO? (Answer: Shifts ground reaction force medially, changes Achilles from eversion to inversion moment, offloads reconstructed PTT)"
"How do you manage MDCO nonunion? (Answer: If asymptomatic observe; if painful revise with bone graft and rigid fixation, consider BMP)"
"What if the patient develops cavovarus overcorrection? (Answer: Symptomatic treatment with orthosis, or revision with medial opening wedge calcaneal osteotomy or lateral column shortening)"
VIVA SCENARIOCritical
Scenario 3: Stage III vs Stage II Distinction (Critical, 2-3 min)
EXAMINER
"A 58-year-old patient presents with longstanding flatfoot deformity and medial ankle pain. On examination, the heel is in valgus and the arch is collapsed. When you attempt to passively correct the deformity, you find the heel valgus only partially corrects. How does this finding influence your surgical management, and what procedure would you recommend?"
EXCEPTIONAL ANSWER
This is a critical examination finding. The inability to fully correct the heel valgus passively indicates a **rigid deformity**, which classifies this as **Stage III PTTD**. This is in contrast to Stage II where the deformity is flexible and fully correctable. The distinction is crucial because it determines surgical management: Stage II flexible deformity can be treated with **soft tissue reconstruction** (FDL transfer + MDCO) which preserves hindfoot motion, whereas Stage III rigid deformity requires **triple arthrodesis** to correct the fixed bony malalignment. If I attempted FDL + MDCO in this rigid Stage III deformity, the surgery would fail because the soft tissue reconstruction cannot overcome fixed bony deformity - the heel valgus and arch collapse would recur. Therefore, my recommendation for this patient is **triple arthrodesis** (fusion of talonavicular, subtalar, and calcaneocuboid joints) to restore alignment. I would counsel about loss of hindfoot motion, 6-8 weeks non-weight-bearing, longer recovery than Stage II surgery (6-9 months), nonunion risk 10-15%, and adjacent joint arthritis risk 20-30% at 10 years. The key message is that the **passive correction test** is the single most important examination finding to distinguish Stage II from Stage III and guide surgical decision-making.
KEY POINTS TO SCORE
Recognition of rigidity: Partially correctable = rigid deformity = Stage III
Critical distinction: Flexible (Stage II) vs rigid (Stage III) determines surgery type
Stage III requires arthrodesis: Triple fusion to correct fixed bony deformity
FDL + MDCO will fail in Stage III: Soft tissue cannot overcome rigid bony deformity
Passive correction test is key: Single most important examination to guide surgery
COMMON TRAPS
✗Performing FDL + MDCO in a rigid deformity → Certain failure → Patient worse off (had surgery with no benefit, now needs revision triple arthrodesis)
✗Not performing passive correction test → Misclassifying Stage III as Stage II → Wrong surgery
✗Assuming all PTTD patients are surgical candidates for soft tissue reconstruction → Some need fusion
✗Not counseling about loss of hindfoot motion with triple arthrodesis → Patient expectations not managed
LIKELY FOLLOW-UPS
"What if the patient also has ankle valgus tilt on mortise view? (Answer: Stage IV - requires triple arthrodesis + deltoid reconstruction OR tibiotalocalcaneal fusion)"
"What is the fusion rate for triple arthrodesis? (Answer: 80-90%, nonunion most common at talonavicular joint)"
"How would you manage persistent pain after triple arthrodesis with solid fusion? (Answer: Assess for adjacent joint arthritis (ankle, midfoot), consider fusion extension or shoe modifications/orthosis)"
MCQ Practice Points
FDL Anatomy Question
Q: The flexor digitorum longus tendon is harvested for posterior tibial tendon reconstruction. At what anatomical landmark should the FDL be transected to maximize harvest length while minimizing donor morbidity? A: Distal to the master knot of Henry. The master knot of Henry is the crossing point where FDL passes superficial to FHL in the midfoot. Transecting FDL distal to this point allows the tendon to be pulled proximally, stripping it from its insertions on the lateral four toes with minimal donor morbidity (toe flexion loss is not functionally significant). Transecting proximal to the knot risks losing harvest length and disrupting FHL.
Johnson and Strom Classification Question
Q: A patient with PTTD has medial arch collapse and heel valgus that can be fully corrected with passive manipulation. What Johnson & Strom stage is this, and what is the surgical treatment? A: Stage II - Flexible flatfoot deformity. The key feature is passive correctability - the deformity can be fully corrected when manipulated, indicating the joints are not arthritic or fixed. Treatment is FDL transfer + MDCO (± lateral column lengthening if forefoot abduction present). If the deformity were rigid (not correctable), it would be Stage III requiring triple arthrodesis.
MDCO Biomechanics Question
Q: What is the biomechanical effect of medial displacement calcaneal osteotomy in PTTD reconstruction? A: MDCO shifts the ground reaction force medial to the ankle joint axis, changing the Achilles tendon moment arm from an eversion moment (contributing to heel valgus) to an inversion moment (correcting heel valgus). This passive correction offloads the reconstructed FDL by reducing the load on the tendon. Without MDCO, FDL transfer alone has only 60-70% success because the biomechanics remain unfavorable. Combination FDL + MDCO achieves 85-90% success.
Too Many Toes Sign Question
Q: The too many toes sign in PTTD indicates what deformity component, and how does it affect surgical planning? A: The too many toes sign (viewing more than 1-2 toes from behind when standing behind the patient) indicates forefoot abduction, which is a transverse plane deformity. This classifies the patient as Stage IIb (if flexible). Surgical planning must include lateral column lengthening (Evans osteotomy or calcaneocuboid distraction arthrodesis) in addition to standard FDL transfer + MDCO. Without addressing the forefoot abduction, the deformity will recur.
Stage IV Definition Question
Q: What distinguishes Stage IV PTTD from Stage III, and how does this change surgical management? A: Stage IV involves deltoid ligament insufficiency with ankle valgus tilt, in addition to the rigid flatfoot deformity of Stage III. On mortise ankle view, the medial clear space is over 4mm (normal under 4mm) and there is talar tilt. Surgical management requires addressing both hindfoot and ankle - triple arthrodesis alone will fail. Options are triple + deltoid reconstruction (if no ankle arthritis) or tibiotalocalcaneal fusion (if ankle arthritis present). Stage IV has the worst prognosis of all PTTD stages.
Complication Question
Q: What is the most common cause of recurrent deformity after FDL transfer + MDCO for Stage II PTTD? A: Inadequate correction at index surgery. Specifically: (1) Inadequate MDCO medial translation (under 10mm), (2) Missing lateral column lengthening in a patient with too many toes sign (Stage IIb), (3) Inadequate FDL tensioning. Other causes include patient non-compliance (early weight-bearing), obesity (excessive load on reconstruction), and progression of underlying disease. Prevention requires meticulous surgical technique with adequate correction in all three planes (valgus, abduction, arch collapse) and strict postoperative non-weight-bearing protocol.
Australian Context and Medicolegal Considerations
Australian Surgical Landscape
- Public hospital access: PTTD reconstruction typically performed in public system after conservative management failure
- Private practice: Increasing volume of FDL transfer + MDCO procedures
- Waiting times: 6-12 months in public system (allows adequate conservative trial)
- DVA patients: Common presentation in older veterans, comprehensive rehabilitation access
Australian Guidelines
- ACSQHC: VTE prophylaxis mandatory for major foot/ankle surgery (aspirin 325mg daily or LMWH)
- Perioperative antibiotic: Cephazolin 2g IV within 60 minutes of incision
- Diabetic patients: Multidisciplinary care with endocrinology, optimized HbA1c prior to elective surgery
- AOANJRR: No specific registry for PTTD reconstruction (arthroplasty registry only)
Medicolegal Considerations in PTTD Surgery
Key documentation requirements:
-
Conservative management failure: Document at least 6 months of conservative treatment (UCBL orthosis, physiotherapy, NSAIDs) before recommending surgery. Medicolegal risk if surgery performed without adequate conservative trial.
-
Staging and surgical planning: Document passive correction test result (flexible vs rigid), too many toes sign presence, and radiographic measurements (heel valgus, talus-1st MT angle). This justifies procedure selection (FDL + MDCO vs triple arthrodesis vs combination with LCL).
-
Informed consent: Must counsel about:
- Success rates (85-90% for FDL + MDCO, but lower if risk factors present)
- 6 weeks non-weight-bearing (patient must have support at home or arrange care)
- Recurrent deformity risk 10-15%
- Sural nerve injury risk (document nerve protection intraoperatively)
- Alternative treatments (triple arthrodesis, continued conservative management)
-
Risk factor counseling: Document discussion of obesity (BMI over 35), diabetes, smoking as risk factors for failure/complications. Consider deferring surgery until risk factors optimized (weight loss, smoking cessation).
-
Postoperative complications: Early recognition and documentation of compartment syndrome symptoms, wound complications, and CRPS. Delayed recognition of compartment syndrome is a significant medicolegal risk.
Common litigation issues in PTTD surgery:
- Sural nerve injury (most common nerve injured in MDCO)
- Recurrent deformity due to inadequate correction or wrong procedure selection (FDL + MDCO in Stage III rigid deformity)
- Compartment syndrome (rare but catastrophic if missed)
- Infection requiring hardware removal or amputation (diabetic patients at highest risk)
PTTD SURGICAL RECONSTRUCTION
High-Yield Exam Summary
Key Anatomy
- •FDL runs DEEP to PTT in tarsal tunnel - ideal transfer donor
- •Master knot of Henry = FDL crosses superficial to FHL - harvest FDL distal to this point
- •Sustentaculum tali = landmark where PTT and FDL diverge in tarsal tunnel
- •Spring ligament complex = supports talonavicular joint, often torn in PTTD
- •Sural nerve = crosses lateral calcaneus - at risk during MDCO
Classification - Johnson & Strom
- •Stage I = tenosynovitis, normal alignment = conservative ± debridement
- •Stage II = FLEXIBLE flatfoot deformity = FDL + MDCO ± LCL
- •Stage III = RIGID flatfoot deformity = triple arthrodesis
- •Stage IV = Stage III + ankle valgus tilt (deltoid insufficiency) = triple + deltoid reconstruction or TTC fusion
- •KEY TEST: Passive correction = flexible (Stage II) vs rigid (Stage III)
Surgical Algorithm
- •Stage IIa (valgus only): FDL transfer + MDCO
- •Stage IIb (valgus + abduction/too many toes): FDL + MDCO + LCL
- •Stage IIc (valgus + abduction + forefoot varus): FDL + MDCO + LCL + Cotton osteotomy
- •FDL harvest: Transect distal to knot of Henry, transfer to navicular via drill hole
- •MDCO: 10-12mm medial translation, 1.5-2cm distal to tuberosity, fix with 2 screws
Surgical Pearls
- •Combination FDL + MDCO = 85-90% success (FDL alone = 60-70%)
- •MDCO biomechanics: Shifts ground reaction force medially, changes Achilles from eversion to inversion moment
- •Protect sural nerve during MDCO (posterior to lateral incision)
- •Assess spring ligament intraoperatively - reconstruct if torn
- •Set FDL tension with foot in plantarflexion and inversion (restores arch)
Complications
- •Undercorrection/recurrent deformity: 10-15% - most common cause is inadequate MDCO translation or missing LCL in Stage IIb
- •Overcorrection/cavovarus: 5-10% - excessive MDCO (over 12mm) or LCL lengthening
- •MDCO nonunion: 5-10% - smoking, diabetes, inadequate fixation
- •Sural nerve injury: 2-5% temporary, 1% permanent - protect during MDCO
- •FDL transfer failure: 5-8% - pullout from navicular, inadequate fixation
Key Evidence
- •FDL + MDCO achieves 85-90% good outcomes vs 80-85% for triple arthrodesis (Myerson 2004)
- •MDCO biomechanics: Shifts ground reaction force 12mm medially, reduces PTT stress 35% (Hadfield 2005)
- •Triple arthrodesis: 35% adjacent joint arthritis at 10 years (Saltzman 1999)
- •Lateral column lengthening: Corrects forefoot abduction but 12% nonunion, 15% lateral column pain (Hintermann 1999)
- •Postop protocol: 6 weeks NWB critical to protect FDL fixation and allow MDCO healing