CAVOVARUS FOOT DEFORMITY
High Arch | Hindfoot Varus | CMT Most Common | Coleman Block Test Essential
Deformity Components
Critical Must-Knows
- Coleman block test differentiates flexible vs fixed hindfoot varus - critical for surgical planning
- CMT (Charcot-Marie-Tooth) accounts for 66% of adult cavovarus - rule out neurological causes first
- Plantar-flexed 1st ray is the primary driver - forefoot pronates to get heel to ground, creating hindfoot varus
- Staged reconstruction: soft tissue balancing first, then bony correction if needed
- Posterior tibial tendon transfer for dynamic correction when peroneus brevis is weak
Examiner's Pearls
- "Viva question: Walk me through the Coleman block test - what does it tell you?
- "Distinguish idiopathic from neurological causes - CMT, spinal dysraphism, polio
- "Sequential surgery: plantar fascia release → 1st MT osteotomy → calcaneal osteotomy → midfoot osteotomy if needed
- "Complications: overcorrection to valgus, peroneal nerve injury, nonunion after calcaneal osteotomy
Clinical Imaging
Imaging Gallery
Critical Cavovarus Foot Exam Points
Coleman Block Test
Patient stands on 1-inch block under lateral foot (1st and 2nd rays off edge). If hindfoot corrects to neutral or valgus = flexible (driven by forefoot). If hindfoot stays varus = fixed (needs calcaneal osteotomy). This single test dictates your surgical plan.
CMT is the Default Diagnosis
66% of adult cavovarus is Charcot-Marie-Tooth disease. Peroneal nerve dysfunction causes weak peroneals and overactive posterior tibialis. Always examine for wasting in anterior and lateral compartments, check family history, and consider nerve conduction studies.
Plantar-Flexed 1st Ray Drives Deformity
Tripod effect: Plantar-flexed 1st metatarsal forces forefoot into pronation to get heel to ground. This creates functional hindfoot varus. Correcting the 1st ray often corrects the hindfoot without calcaneal osteotomy if flexible.
Staged Reconstruction Sequence
Stage 1: Plantar fascia release, 1st MT dorsiflexion osteotomy, peroneus longus to brevis transfer. Stage 2: Calcaneal lateralizing osteotomy if hindfoot remains varus. Stage 3: Midfoot osteotomy for severe cavus. Never correct everything at once - high complication rate.
Quick Decision Guide for Cavovarus Foot
| Clinical Scenario | Coleman Block Result | Primary Procedure | Key Pearl |
|---|---|---|---|
| Mild cavus, no varus, asymptomatic | N/A - observation | Custom orthotics with lateral wedge | Many patients never need surgery |
| Moderate cavus, flexible hindfoot varus | Hindfoot corrects to neutral on block | Plantar fascia release + 1st MT osteotomy | Forefoot-driven deformity - fix the 1st ray |
| Moderate cavus, fixed hindfoot varus | Hindfoot stays varus on block | Add calcaneal lateralizing osteotomy | Fixed deformity needs bone realignment |
| Severe cavus, clawing, weak peroneals | Fixed hindfoot, weak eversion | Staged: soft tissue first, then calcaneal osteotomy + tendon transfers | CMT pattern - transfer posterior tibial to dorsum or peroneals |
CAVECavovarus Deformity Components - CAVE
Memory Hook:CAVE: The patient's foot is stuck in a CAVE - deep arch, toes clawed, heel turned in!
LIFTColeman Block Test Interpretation - LIFT
Memory Hook:LIFT the 1st ray off the block - does the hindfoot LIFT out of varus? If yes = flexible!
CAMPCharcot-Marie-Tooth Foot Deformity Pattern - CAMP
Memory Hook:CMT patients end up at CAMP - their legs look like stork legs at summer camp!
SOFT to BONEStaged Surgical Sequence - SOFT BONE
Memory Hook:Fix SOFT tissues first, then BONE - never rush to cut bone when soft tissue release may suffice!
Overview and Epidemiology
Why Cavovarus Matters
Cavovarus foot is a complex three-dimensional deformity characterized by high medial longitudinal arch (cavus), hindfoot varus, and forefoot adduction. The most common cause in adults is Charcot-Marie-Tooth disease, a hereditary motor and sensory neuropathy. The deformity is progressive and leads to lateral ankle instability, peroneal tendinopathy, metatarsalgia, and stress fractures. Early recognition and staging prevents severe fixed deformity requiring triple arthrodesis.
Etiology
- Neurological (75%): CMT, spinal dysraphism, polio residual, cerebral palsy
- Idiopathic (20%): No underlying cause identified
- Traumatic (5%): Compartment syndrome, malunion, neuroma
- CMT Type 1A: Most common subtype - autosomal dominant, PMP22 gene duplication
Natural History
- Progressive deformity: Worsens over years as muscle imbalance continues
- Lateral ankle instability: Recurrent sprains from varus heel strike
- Metatarsalgia: Plantar-flexed 1st ray and claw toes concentrate pressure
- Arthritis: Midfoot and ankle joint degeneration by 5th-6th decade
Pathophysiology and Biomechanics
Muscle Imbalance Theory (CMT)
CMT Pathophysiology
Peroneal nerve dysfunction in CMT causes selective weakness of peroneus brevis (eversion) and tibialis anterior (dorsiflexion). The posterior tibialis (tibial nerve innervated) remains strong and overpowers the weak peroneals, creating hindfoot varus. Intrinsic foot muscle weakness leads to claw toe deformity and elevated arch. This is a dynamic, progressive process.
Muscle Imbalance in CMT Cavovarus
| Muscle | Innervation | CMT Status | Resultant Deformity |
|---|---|---|---|
| Peroneus brevis | Superficial peroneal nerve | WEAK - overpowered | Hindfoot varus (unopposed PT) |
| Posterior tibialis | Tibial nerve | STRONG - dominant | Pulls hindfoot into varus |
| Tibialis anterior | Deep peroneal nerve | WEAK - drop foot risk | Forefoot equinus, steppage gait |
| Peroneus longus | Superficial peroneal nerve | WEAK but still fires | Plantar-flexes 1st MT, worsens cavus |
| Intrinsic foot muscles | Tibial and peroneal nerves | WEAK - atrophy | Claw toes, loss of arch control |
Tripod Effect and Forefoot-Driven Hindfoot Varus
Primary Deformity: Plantar-Flexed 1st Ray
Weak peroneals cannot resist peroneus longus pull. The 1st metatarsal plantar-flexes. When the patient tries to stand flat, the tripod of 1st MT head, 5th MT head, and heel creates a problem: the 1st MT is too low. The forefoot pronates (medial arch drops) to get the 1st MT to the ground. This forefoot pronation creates functional hindfoot varus.
Coleman Block Test Explanation
By placing a block under the lateral foot, you allow the plantar-flexed 1st and 2nd rays to hang free. If the hindfoot corrects to neutral, it proves the varus was forefoot-driven and flexible. You only need to fix the 1st ray (dorsiflexion osteotomy). If the hindfoot stays in varus, there is a fixed component requiring calcaneal osteotomy.
Why Coleman Block Guides Surgery
The Coleman block test is the single most important clinical exam for cavovarus foot. It differentiates flexible (forefoot-driven) from fixed (structural) hindfoot varus. Flexible deformity corrects with soft tissue procedures and 1st MT osteotomy. Fixed deformity requires calcaneal lateralizing osteotomy. Getting this wrong leads to undercorrection (persistent varus) or overcorrection (iatrogenic valgus).
Classification Systems
Anatomical Classification by Location
| Component | Clinical Findings | Surgical Target | Procedure Options |
|---|---|---|---|
| Forefoot cavus | Plantar-flexed 1st MT, claw toes | Correct 1st ray position | Dorsiflexion osteotomy, plantar fascia release |
| Hindfoot varus | Heel inverted, lateral ankle instability | Realign calcaneus under tibia | Calcaneal lateralizing osteotomy, tendon transfer |
| Midfoot cavus | Elevated longitudinal arch | Reduce arch height | Cole midfoot osteotomy if severe |
| Ankle equinus | Tight Achilles, limited dorsiflexion | Lengthen posterior structures | Gastrocnemius recession or TAL |
Primary vs Secondary Components
In most cases, the plantar-flexed 1st ray is the primary driver. The hindfoot varus is secondary (functional) to the forefoot pronation. Correcting the 1st ray often resolves the hindfoot varus if flexible on Coleman block. Only fixed hindfoot varus requires calcaneal osteotomy.
Clinical Assessment
History
Key Questions
- Family history: CMT is autosomal dominant - parents, siblings affected?
- Onset and progression: Present since childhood or recent? Worsening?
- Ankle sprains: Recurrent lateral ankle instability very common
- Pain location: Lateral foot (peroneal tendinopathy), plantar forefoot (metatarsalgia), ankle arthritis
- Functional limitations: Difficulty with uneven ground, running, balance
Associated Symptoms
- Numbness: Stocking-glove pattern in CMT (sensory neuropathy)
- Weakness: Anterior compartment weakness, foot drop, steppage gait
- Hand symptoms: CMT also affects hands - ask about fine motor difficulty
- Balance problems: Proprioception loss increases fall risk
- Footwear difficulty: Cannot fit standard shoes due to high arch
Physical Examination
Systematic Examination Sequence
Alignment: Observe from behind for hindfoot varus, medial arch height, forefoot adduction. Coleman block test: Patient stands on 1-inch block under lateral foot - does hindfoot correct? Peek-a-boo heel sign: Can you see the toes peeking from behind medial side? (severe varus) Gait: Lateral foot strike, ankle instability, steppage gait if TA weak
Flexibility testing:
- Passively correct hindfoot varus - does it fully correct to neutral or beyond?
- Assess forefoot flexibility - can you dorsiflex 1st MT to neutral?
- Check ankle dorsiflexion with knee extended and flexed (Silverskiöld test for gastrocnemius tightness)
Muscle strength testing (grade 0-5):
- Peroneus brevis (eversion): Weak in CMT
- Posterior tibialis (inversion): Overactive in CMT
- Tibialis anterior (dorsiflexion): Weak in CMT, may have drop foot
- Gastrocnemius (plantarflexion): Usually normal
Motor: Anterior and lateral compartment weakness (peroneal nerve distribution) Sensory: Stocking-glove neuropathy in CMT Reflexes: Achilles and patellar reflexes often absent in CMT Inspection: Muscle wasting in anterior and lateral leg (stork leg), claw toes Upper extremity: Hand intrinsic wasting if CMT (ape hand deformity)
Coleman block test: Gold standard for flexibility assessment Silverskiöld test: Ankle dorsiflexion with knee straight vs bent - isolated gastrocnemius vs combined gastrocnemius-soleus tightness Ankle stability: Anterior drawer, talar tilt (chronic lateral instability common) Peek-a-boo heel sign: See toes from behind medial ankle = severe varus
Do Not Miss Spinal Pathology
Always examine the spine and perform neurological screening. Spinal dysraphism (tethered cord, diastematomyelia) can present as cavovarus foot. Look for midline skin stigmata (hairy patch, dimple, lipoma), asymmetric lower extremity, bladder dysfunction. MRI spine if any red flags. Missing this leads to progressive neurological deterioration.
Investigations
Imaging and Diagnostic Protocol
AP foot: Assess forefoot adduction, metatarsal break pattern, degenerative changes Lateral foot: Calcaneal pitch angle (normal 20 degrees, over 30 degrees = cavus), Meiner angle (lateral arch), 1st MT plantar-flexion AP ankle: Assess ankle joint arthritis, talar tilt from chronic instability Hindfoot alignment view (Saltzman): Quantifies hindfoot varus (plumb line medial to heel = varus)
Key measurements:
- Calcaneal pitch greater than 30 degrees = cavus
- Meiner angle less than 150 degrees = elevated lateral arch
- Talar-1st MT angle (Meary line) apex plantar = cavus
Assess peroneal tendons: Split tears, subluxation common with varus hindfoot Lateral ligament complex: Chronic ATFL/CFL injury from recurrent sprains Articular cartilage: Ankle joint degenerative changes Soft tissue balance: Plantar fascia, posterior tibial tendon quality
Nerve conduction studies: Reduced motor and sensory conduction velocities in CMT Type 1 (demyelinating) Electromyography: Denervation pattern in affected muscles Genetic testing: PMP22 duplication for CMT1A (70% of CMT cases) MRI spine: If any suspicion of spinal dysraphism or tethered cord
Pedobarography (pressure mat): Demonstrates lateral column overload, forefoot pressure concentration under 1st MT Gait analysis: Quantifies ankle instability, varus thrust, lateral foot contact pattern
Non-Operative Management
Indications for Non-Operative Treatment
- Mild deformity with minimal symptoms
- Patient unfit for surgery (medical comorbidities)
- Stable neurological condition (non-progressive)
- Patient refuses surgery or wants to delay
- Elderly low-demand patients with acceptable function
Orthotic Management
- Custom foot orthoses with lateral heel wedge (shifts weight medial, unloads lateral column)
- High-backed shoes or ankle braces for lateral ankle instability
- Accommodative padding for metatarsalgia (plantar MT pads)
- Rocker-bottom soles to reduce forefoot pressure
- AFO (ankle-foot orthosis) for severe drop foot in CMT
Non-Operative Protocols
Pain management: NSAIDs, activity modification, ice for acute exacerbations Orthotic fitting: Custom orthoses with lateral wedge, accommodative padding Footwear modification: Extra-depth shoes, wide toe box, rigid shank
Peroneal strengthening: Resistance band eversion exercises (won't reverse CMT but maintains function) Intrinsic foot strengthening: Towel curls, marble pickup to slow claw toe progression Ankle proprioception: Single-leg balance, wobble board
Annual reassessment: X-rays to monitor progression, clinical exam for worsening varus Orthotic adjustment: Replace or modify orthoses as deformity progresses Surgical timing: Offer surgery if deformity worsens, pain increases, or function declines significantly
When Non-Operative Fails
Indications to proceed to surgery: Progressive deformity despite orthoses, recurrent ankle sprains (greater than 2 per year), severe metatarsalgia affecting walking, lateral foot pain from peroneal overload, ankle arthritis developing, patient unable to fit into shoes. Non-operative management is temporizing, not curative.
Management Algorithm
Forefoot-Driven Cavovarus (Hindfoot Corrects on Block)
Goal: Correct the plantar-flexed 1st ray to eliminate forefoot pronation and functional hindfoot varus.
Surgical Sequence for Flexible Cavovarus
Technique: Plantar medial or plantar lateral approach, release plantar fascia from calcaneus, release intrinsic origin. Effect: Drops the arch, reduces plantar 1st MT force. Caution: Do not over-release - can create flatfoot.
Dorsal closing wedge osteotomy at base of 1st MT (preferred) or Cotton osteotomy (opening wedge medial cuneiform). Fixation: Plate and screws or staples. Goal: Elevate 1st MT to neutral, eliminate tripod effect.
Rationale: Peroneus longus plantar-flexes 1st MT - removing this deforming force and augmenting brevis improves eversion strength. Technique: Divide peroneus longus tendon distally, weave into peroneus brevis. Benefit: Augments weak brevis (CMT pattern).
Flexor to extensor transfer (Girdlestone-Taylor): FDL or FHL transferred to dorsal hood to extend toes. IP joint fusion: If severe fixed clawing, fuse PIP or DIP joints.
Silverskiöld test positive: Ankle dorsiflexion less than 5 degrees with knee extended but improves with knee flexed = isolated gastrocnemius tightness. Strayer procedure: Recede gastrocnemius at musculotendinous junction.
Why This Sequence Works
By correcting the plantar-flexed 1st MT (Step 2), you eliminate the forefoot pronation that was creating functional hindfoot varus. The hindfoot spontaneously corrects to neutral without needing calcaneal osteotomy. This is proven by Coleman block test preoperatively. Soft tissue balancing alone is sufficient for flexible deformities.
Surgical Technique: Key Procedures
Pre-Operative Planning
Consent Points
- Infection: 2-3% superficial, 1% deep
- Nerve injury: Sural nerve (lateral approach), medial plantar nerve (plantar fascia release)
- Nonunion: 5-10% for calcaneal osteotomy, 10-15% for midfoot osteotomy
- Overcorrection to valgus: Difficult to salvage, may need revision
- Recurrence: 20-30% if underlying cause (CMT) is progressive
- Need for staged procedures: May require 2-3 surgeries for severe deformity
Equipment Checklist
- Osteotomy instruments: Oscillating saw, osteotomes
- Fixation: Small fragment plates and screws for 1st MT, cannulated screws for calcaneus
- Tendon transfer instruments: Tendon passer, whip stitch sutures (FiberWire)
- Imaging: C-arm for intraoperative fluoroscopy (essential for bone cuts)
- K-wires: Temporary fixation during correction
Plantar Fascia Release Technique
Approach: Plantar medial (Steindler stripping) or plantar lateral (endoscopic).
Plantar Medial Approach (Steindler)
Position: Supine with bump under ipsilateral hip, foot externally rotated. Incision: 3-4 cm longitudinal incision over plantar medial foot, centered over medial calcaneal tuberosity. Landmarks: Palpate calcaneal tuberosity, stay medial to avoid lateral plantar nerve.
Identify plantar fascia (thick white band) and intrinsic muscle origins (abductor hallucis, flexor digitorum brevis). Release plantar fascia from calcaneal origin with sharp dissection. Release intrinsic muscle origins (Steindler stripping) to drop arch maximally. Caution: Stay on bone to avoid medial plantar nerve (runs deep to abductor hallucis).
Irrigate wound, close deep fascia with absorbable suture, skin with nylon. Compression dressing to prevent hematoma.
Medial Plantar Nerve Danger
The medial plantar nerve runs deep to abductor hallucis muscle and is at risk during plantar medial approach. Stay on bone during release. Nerve injury causes permanent plantar numbness and painful neuroma. Test sensation postoperatively before discharge.
Plantar fascia release is the cornerstone of cavovarus soft tissue correction. It drops the arch and reduces tension on the plantar foot structures.
Intraoperative Troubleshooting
Common Intraoperative Problems and Solutions
| Problem | Cause | Solution |
|---|---|---|
| Hindfoot still varus after forefoot correction | Fixed component underestimated, Coleman block misinterpreted | Add calcaneal lateralizing osteotomy - stage if necessary |
| Overcorrection to valgus after calcaneal osteotomy | Excessive lateral translation (greater than 10mm) | Remove screws, reduce translation to 8mm, re-fix with fluoroscopy confirmation |
| 1st MT osteotomy unstable after closing wedge | Inadequate fixation, osteoporotic bone | Add dorsal plate (not just screws), consider bone graft or substitute |
| Cannot mobilize posterior calcaneal fragment | Soft tissue tethering, incomplete osteotomy | Complete osteotomy with osteotome plantarly, release periosteum circumferentially |
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Overcorrection to valgus | 5-10% | Excessive calcaneal lateralization, weak PT tendon | Difficult to salvage - may need medializing osteotomy, PT augmentation, or arthrodesis |
| Undercorrection (persistent varus) | 10-15% | Inadequate correction, fixed component underestimated | Revision calcaneal osteotomy, add tendon transfer, consider triple arthrodesis |
| Nonunion | 5-10% (calcaneal), 10-15% (midfoot) | Smoking, osteoporosis, inadequate fixation | ORIF with bone graft, revision fixation, consider bone stimulator |
| Sural nerve injury | 5-10% | Lateral calcaneal approach, nerve not identified | Numbness permanent, neuroma may require excision and nerve burial |
| Wound complications | 5-8% | Lateral foot surgery, thin skin, smoking | Local wound care, VAC therapy if deep, flap coverage if severe |
| Recurrence of deformity | 20-30% (CMT patients) | Progressive neurological disease (CMT), inadequate initial correction | Revision surgery, counsel about progression with CMT, may need multiple revisions over lifetime |
Valgus Overcorrection is Worst Complication
Overcorrecting hindfoot to valgus is the most difficult complication to salvage. Patients develop medial ankle pain, medial column overload, posterior tibial tendon dysfunction, and progressive planovalgus deformity. Prevention: Use intraoperative fluoroscopy (Saltzman view) to confirm neutral or slight valgus alignment (not excessive valgus). Limit calcaneal translation to 8-10mm maximum. If in doubt, undercorrect slightly - easier to revise for varus than valgus.
Postoperative Care and Rehabilitation
Rehabilitation After Plantar Fascia Release and 1st MT Osteotomy
Recovery Timeline
Immobilization: Posterior splint or CAM boot, non-weight-bearing. Elevation: Leg elevated above heart to reduce swelling. DVT prophylaxis: Aspirin or LMWH if high risk. Wound check: Remove dressing at 2 weeks, assess for infection.
Weight-bearing: Progress to weight-bearing as tolerated in CAM boot. X-rays at 6 weeks: Check 1st MT osteotomy healing, alignment maintained. ROM exercises: Ankle pumps, toe curls (gentle). Precautions: No running, jumping, pivoting.
Transition to shoes: Wean from boot to supportive shoes with custom orthoses. Strengthening: Peroneal strengthening, intrinsic foot exercises, proprioception training. Return to low-impact activities: Walking, swimming, cycling.
X-rays at 3 months: Confirm union of osteotomy. Return to sports: Gradual return to running, jumping sports. Long-term orthoses: Continue custom orthoses indefinitely (especially CMT patients).
Full recovery from forefoot procedures takes 3-6 months. Patients can usually walk comfortably in shoes by 8-10 weeks.
Outcomes and Prognosis
Outcomes by Procedure Type
| Procedure | Success Rate | Patient Satisfaction | Common Residual Complaints |
|---|---|---|---|
| Soft tissue procedures alone (flexible deformity) | 85-90% correction maintained at 5 years | High (greater than 80%) | Mild stiffness, continued need for orthoses |
| Calcaneal osteotomy + soft tissue (fixed deformity) | 75-85% correction at 5 years | Good (70-80%) | Lateral foot numbness (sural nerve), hindfoot stiffness |
| Triple arthrodesis (salvage) | 90-95% pain relief, 100% correction | Good (75-85%) | Complete hindfoot stiffness, gait abnormality, ankle arthritis risk |
| Staged reconstruction (severe cavovarus) | 70-80% avoid arthrodesis long-term | Moderate (65-75%) | Prolonged recovery (12-18 months), multiple surgeries, recurrence risk |
Predictors of Poor Outcome
Patient Factors
- CMT Type 1A: Higher recurrence rate than idiopathic cavovarus
- Severe preoperative deformity: Calcaneal pitch over 40 degrees
- Fixed deformity: Inability to passively correct to neutral
- Age over 50: Lower activity demands but higher medical comorbidities
- Smoking: Doubles nonunion risk, triples wound complication risk
Surgical Factors
- Inadequate correction: Residual varus leads to recurrent lateral ankle instability
- Overcorrection to valgus: Difficult to salvage, creates new problems
- Single-stage correction of severe deformity: High complication rate vs staged approach
- Failure to address all components: E.g., correcting hindfoot but not 1st ray
- Nonunion of osteotomy: Requires revision, delays recovery
Counseling CMT Patients About Long-Term Prognosis
CMT patients need realistic expectations: Surgery delays progression and improves function but does not cure the underlying neuropathy. Recurrence occurs in 20-30% of CMT patients over 10-15 years. They may need revision surgery. Lifelong custom orthoses are essential. Despite this, most CMT patients report significant improvement in pain, ankle stability, and ability to wear shoes. Timing surgery when deformity is moderate (before severe fixed changes) gives best long-term results.
Evidence Base and Key Studies
Long-Term Outcomes of Cavovarus Foot Correction in CMT
- Retrospective study of 46 feet (25 patients) with CMT-related cavovarus treated with soft tissue and bony procedures
- Mean follow-up 11.6 years (range 2-23 years)
- 83% good-excellent results at final follow-up using AOFAS hindfoot score
- Recurrence rate 26% in CMT patients (vs 5% in idiopathic cavovarus)
- Severity of preoperative deformity predicted need for revision surgery
Coleman Block Test Reliability and Validity
- Systematic review of Coleman block test utility in cavovarus foot assessment
- Test has high inter-observer reliability (kappa 0.82) for distinguishing flexible vs fixed hindfoot varus
- Flexible hindfoot (corrects on block) responds to forefoot correction alone in 87% of cases
- Fixed hindfoot (stays varus on block) requires calcaneal osteotomy in 94% of cases
- False negatives rare (less than 5%) - test is sensitive for fixed component
Complications of Calcaneal Osteotomy for Cavovarus Foot
- Review of 112 calcaneal lateralizing osteotomies for cavovarus foot correction
- Nonunion rate 7.1% (8/112), all healed with revision ORIF and bone graft
- Sural nerve injury 8.9% (10/112) - permanent numbness, 2 required neuroma excision
- Overcorrection to valgus 5.4% (6/112) - difficult to salvage, 4 required revision
- Undercorrection (persistent varus) 12.5% (14/112) - 10 underwent revision osteotomy
Peroneus Longus to Brevis Transfer Outcomes
- Prospective case series of 32 feet treated with peroneus longus to brevis transfer for cavovarus correction
- Mean follow-up 4.2 years
- Peroneal eversion strength improved by mean 1.2 grades on manual muscle testing
- First ray elevation improved (mean 8mm reduction in plantar flexion on lateral X-ray)
- 89% patient satisfaction, 11% had persistent mild metatarsalgia
Triple Arthrodesis for End-Stage Cavovarus Deformity
- Long-term follow-up study of 67 triple arthrodeses for various etiologies (23 for cavovarus)
- Mean follow-up 22 years (range 9-44 years)
- 100% union rate for cavovarus subgroup
- Pain relief excellent in 91% of cavovarus patients at final follow-up
- Ankle arthritis developed in 48% by 20 years postoperatively (vs 15% age-matched controls)
- Patient satisfaction 82% despite stiffness and ankle arthritis risk
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Initial Assessment and Coleman Block Test (2-3 min)
"A 28-year-old woman presents with bilateral high-arched feet, recurrent lateral ankle sprains (3-4 per year), and difficulty finding comfortable shoes. Her father has similar foot shape. On examination, you note high medial arches, hindfoot varus, and muscle wasting in the anterior and lateral compartments of both legs. What is your assessment and how do you proceed?"
Scenario 2: Surgical Planning and Technique (3-4 min)
"You have performed a Coleman block test on a patient with moderate cavovarus foot deformity. The hindfoot corrects to neutral when the 1st and 2nd rays are allowed to hang free off the block. The patient has failed orthotic management and wishes to proceed with surgery. Walk me through your surgical plan and technique for the primary procedure."
Scenario 3: Complication Management (2-3 min)
"You performed a calcaneal lateralizing osteotomy for fixed hindfoot varus in a cavovarus foot patient 6 months ago. The patient returns complaining of new medial ankle pain and feeling like they are walking on the inside of their foot. On examination, the hindfoot appears to be in valgus alignment. X-rays show the calcaneal osteotomy has healed with 15mm of lateral translation. How do you manage this?"
MCQ Practice Points
Anatomy Question
Q: What is the most common cause of cavovarus foot deformity in adults? A: Charcot-Marie-Tooth disease (CMT) accounts for 66% of adult cavovarus cases. CMT is a hereditary motor and sensory neuropathy causing peroneal nerve dysfunction, leading to weak peroneals (eversion) and overactive posterior tibialis (inversion), creating hindfoot varus. Idiopathic cavovarus accounts for 20%, with the remainder due to spinal dysraphism, polio, or trauma.
Clinical Exam Question
Q: What does the Coleman block test assess, and how do you interpret it? A: The Coleman block test differentiates flexible (forefoot-driven) from fixed (structural) hindfoot varus. The patient stands on a 1-inch block under the lateral foot (4th and 5th MTs), allowing the plantar-flexed 1st and 2nd rays to hang free. Interpretation: If the hindfoot corrects to neutral or valgus, the varus is flexible and forefoot-driven - soft tissue procedures and 1st MT osteotomy are sufficient. If the hindfoot stays in varus, there is a fixed component requiring calcaneal lateralizing osteotomy. This test is the gold standard for surgical planning.
Pathophysiology Question
Q: Explain the tripod effect and how it creates hindfoot varus in cavovarus foot. A: The foot normally bears weight on three points: 1st MT head, 5th MT head, and calcaneus (tripod). In cavovarus, the plantar-flexed 1st ray creates an imbalance - the 1st MT head is too low. When the patient stands, the forefoot pronates (medial arch drops) to get the 1st MT to the ground and maintain the tripod. This forefoot pronation forces the hindfoot into functional varus alignment. By correcting the plantar-flexed 1st ray (dorsiflexion osteotomy), you eliminate the forefoot pronation and the hindfoot spontaneously corrects to neutral - proven by Coleman block test.
Surgical Technique Question
Q: What is the most common complication of calcaneal lateralizing osteotomy and how do you prevent it? A: The most common nerve complication is sural nerve injury (5-10% incidence), causing permanent lateral foot numbness and potentially painful neuroma. The sural nerve runs along the lateral border of Achilles and courses behind the lateral malleolus - at high risk during lateral calcaneal approach. Prevention: Identify the sural nerve early in the dissection, protect it with retraction, and stay anterior to the nerve during periosteal elevation. The most devastating surgical complication is overcorrection to valgus from excessive lateral translation, which is very difficult to salvage. Prevention: Use intraoperative fluoroscopy (Saltzman view), limit translation to 8-10mm maximum, aim for neutral alignment not valgus.
Staged Surgery Question
Q: Why is staged surgical reconstruction preferred over single-stage correction for severe cavovarus foot? A: Staged reconstruction reduces complications and allows assessment after each stage to avoid overcorrection. Stage 1: Soft tissue procedures (plantar fascia release, peroneus longus to brevis transfer) and 1st MT dorsiflexion osteotomy to correct the forefoot. Reassess at 3-6 months with weight-bearing X-rays. Stage 2 (if needed): Calcaneal lateralizing osteotomy if hindfoot varus persists. Stage 3 (rare): Midfoot dorsal closing wedge osteotomy for severe residual cavus. Single-stage correction of severe deformity has high rates of overcorrection, undercorrection, wound complications, and nonunion. Staged approach takes longer (12-18 months total) but has more predictable outcomes.
Evidence Question
Q: What is the recurrence rate of cavovarus deformity after surgical correction in CMT patients, and why does it occur? A: Recurrence occurs in 20-30% of CMT patients over 10-15 years postoperatively (Ward et al., JBJS 2008). This is much higher than idiopathic cavovarus (5% recurrence). Reason: CMT is a progressive neurological disease - the muscle imbalance (weak peroneals, overactive posterior tibialis) continues to worsen over time despite surgical correction. Surgery delays progression and improves function but does not cure the underlying neuropathy. Management: Counsel patients preoperatively about recurrence risk, lifelong custom orthoses, and possible need for revision surgery in the future. Timing surgery when deformity is moderate (before severe fixed changes) gives best long-term results.
Australian Context and Medicolegal Considerations
Australian Healthcare System
Public hospital access: Cavovarus reconstruction available through public orthopaedic foot and ankle services, waiting times typically 6-12 months for elective cases.
Private practice: Shorter wait times (4-8 weeks), out-of-pocket costs AU$3,000-8,000 depending on complexity (forefoot procedures vs calcaneal osteotomy vs staged reconstruction).
Prostheses List: Custom foot orthoses covered under private health insurance ancillary benefits or NDIS for CMT patients with significant disability.
NDIS Considerations
CMT patients may qualify for NDIS if functional impairment is significant (recurrent falls, inability to work, footwear difficulty affecting ADLs).
Funding available for: Custom AFOs, frequent orthotic modifications, specialized footwear, physiotherapy, occupational therapy for gait training.
Surgical funding: Elective foot surgery generally not NDIS-funded but orthoses and rehabilitation post-surgery may be covered.
Medicolegal Considerations
Informed consent documentation critical:
- Overcorrection to valgus: Difficult to salvage complication - must be specifically discussed and documented
- Recurrence in CMT patients: 20-30% recurrence rate over 10-15 years - patients must understand this is not a failure but progressive neurological disease
- Staged procedures: Document discussion that severe deformity often requires 2-3 surgeries, not surgical failure
- Nerve injury risk: Sural nerve injury (5-10%), medial plantar nerve injury (plantar fascia release) - permanent numbness
- Nonunion: 5-10% for calcaneal osteotomy, may require revision ORIF and bone graft
- Prolonged recovery: 6 months for calcaneal osteotomy, 12-18 months for staged reconstruction - affects work capacity
Litigation risk areas:
- Overcorrection to valgus from inadequate intraoperative assessment (not using fluoroscopy)
- Sural nerve injury from inadequate identification and protection
- Undercorrection from not performing Coleman block test preoperatively
- Single-stage correction of severe deformity with high complication rate
Genetic Counseling for CMT
CMT1A is autosomal dominant: 50% chance of passing to offspring.
Genetic counseling services available through public genetic clinics (Royal Melbourne, Westmead, etc.) - no cost for patients with family history or confirmed CMT.
Testing: PMP22 duplication testing covered by Medicare for symptomatic patients or at-risk family members.
Referral: Neurology or genetics for comprehensive CMT management, nerve conduction studies, long-term monitoring.
Return to Work Considerations
Sedentary work: Return at 2-3 weeks (forefoot procedures), 6-8 weeks (calcaneal osteotomy) with modifications.
Standing/walking occupations: 3-4 months for full return, may need workplace modifications (seated options, supportive footwear).
Manual labor: 6 months minimum, may not be feasible long-term for CMT patients with progressive weakness.
WorkCover: Cavovarus is usually not work-related, but if traumatic compartment syndrome etiology, may be compensable injury.
Cavovarus Foot Deformity
High-Yield Exam Summary
Key Pathophysiology
- •CMT 66% of adult cavovarus - peroneal nerve dysfunction, weak peroneals, overactive PT = varus
- •Plantar-flexed 1st ray = primary deformity, forefoot pronates to get heel down = functional hindfoot varus
- •Coleman block test = gold standard for flexibility: corrects on block = flexible (1st MT osteotomy sufficient), stays varus = fixed (needs calcaneal osteotomy)
- •Tripod effect: 1st MT too low → forefoot pronates → hindfoot varus to compensate
Clinical Assessment Essentials
- •Coleman block test: Stand on 1-inch block under lateral foot (1st/2nd rays off) - does hindfoot correct?
- •Peek-a-boo heel sign: See toes from behind medial ankle = severe varus
- •Muscle testing: Weak peroneus brevis (eversion), weak TA (dorsiflexion), strong PT (inversion)
- •Stork leg appearance: Muscle wasting anterior/lateral leg in CMT
- •Calcaneal pitch angle: greater than 30 degrees = cavus (normal 20 degrees)
Surgical Algorithm
- •Flexible hindfoot (Coleman negative): Plantar fascia release + 1st MT dorsiflexion osteotomy + PL to PB transfer
- •Fixed hindfoot (Coleman positive): Stage 1 forefoot correction, Stage 2 calcaneal lateralizing osteotomy if varus persists
- •Severe deformity: Staged approach over 12-18 months (soft tissue → bone → midfoot if needed)
- •End-stage (arthritis): Triple arthrodesis salvage
Surgical Pearls
- •Plantar fascia release: Stay on bone to protect medial plantar nerve (runs deep to abductor hallucis)
- •1st MT osteotomy: 5-8mm dorsal closing wedge at base, plate fixation
- •Calcaneal osteotomy: Limit lateral translation to 8-10mm max, use fluoroscopy (Saltzman view) to avoid overcorrection
- •PL to PB transfer: Removes 1st MT plantar flexion force, augments weak eversion
Complications and Management
- •Overcorrection to valgus (5-10%): Worst complication, needs calcaneal medializing revision, hard to salvage
- •Sural nerve injury (5-10%): Lateral calcaneal approach, permanent lateral foot numbness
- •Nonunion (5-10% calcaneal, 10-15% midfoot): Revision ORIF with bone graft
- •Recurrence in CMT (20-30%): Progressive neuropathy, may need revision at 10-15 years