High Yield Overview
Congenital Vertical Talus
Rocker Bottom Foot | Irreducible Dorsal Dislocation
RigidDeformity Type
50%Syndromic
ReversePonseti Technique
TalusVertical Position
Classification
Idiopathic
PatternIsolated deformity. Less common (50%).
TreatmentReverse Ponseti + Surgery
Teratologic (Syndromic)
PatternAssociated with Arthrogryposis, Spina Bifida, Neuro conditions. More resistant.
TreatmentReverse Ponseti + Surgery
Critical Must-Knows
- Definition: Irreducible DORSAL dislocation of the navicular on the talus. The talus is 'vertical'.
- Deformity: Rigid Rocker Bottom Foot (Convex plantar surface). Heel in valgus and equinus.
- Key Differentiation: Differentiate from Oblique Talus (flexible) and Calcaneovalgus (flexible). CVT is RIGID.
- Diagnosis: Forces Plantarflexion Lateral X-ray. The talonavicular joint does NOT reduce (navicular stays dorsal to talus).
- Management: 'Reverse Ponseti' casting followed by minimal surgery (TN pin + Achilles tenotomy) is the new gold standard.
Examiner's Pearls
- "CVT is a DISLOCATION of the Talonavicular joint.
- "50% of cases are associated with syndromes (Arthrogryposis, Neural Tube Defects) - Check the spine!
- "On forced plantarflexion view, the axis of the talus passes BELOW the first metatarsal (does not align).
- "Traditional treatment was extensive release (PMR). Modern treatment is Dobbs method (Reverse Ponseti).
Clinical Imaging
Imaging Gallery
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Clinical Imaging
Imaging Gallery
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CVT Pitfalls
Missed Syndrome
Check the Baby. 50% are syndromic. Exam for arthrogryposis, sacral dimple (spina bifida), and dysmorphism.
Oblique Talus
The Mimic. Oblique talus looks similar but REDUCES on plantarflexion X-ray. CVT does not reduce.
Calcaneovalgus
Flexible vs Rigid. Calcaneovalgus foot is flexible (dorsiflexes easily, usually packaging defect). CVT is rigid.
Recurrence
High Risk. Especially in teratologic cases. Maintenance bracing is crucial.
At a Glance: CVT vs Oblique Talus vs Calcaneovalgus
| Feature | Congenital Vertical Talus | Oblique Talus | Calcaneovalgus |
|---|---|---|---|
| Rigidity | RIGID | FLEXIBLE | FLEXIBLE |
| TN Reduction | Irreducible | Reducible | Reducible |
| X-ray (Forced PF) | Talus axis below 1st MT | Talus aligns with 1st MT | Normal alignment |
| Heel Position | Equinus + Valgus | Valgus | Calcaneus (Dorsiflexed) + Valgus |
| Treatment | Surgery (Dobbs) | Orthotics/Obs | Stretching/Obs |
Mnemonic
ROCKERCVT Features
R
Rigid
Stiff deformity (unlike calcaneovalgus)
O
Obvious Convexity
Rocker bottom sole
C
Check Spine
Associated with neural tube defects
K
Key X-ray
Forced Plantarflexion View
E
Equinus
Heel is in equinus (hidden by rocker bottom)
R
Reverse Ponseti
Dobbs method treatment
Memory Hook:Rocker bottom foot features.
Mnemonic
TAMBARadiographic Sign
T
Talus
Talus Axis
A
And
+
M
Metatarsal
1st Metatarsal Axis
B
Bisect
Should bisect (align)
A
Away
In CVT, Talus points AWAY (below) 1st MT
Memory Hook:TAMBA angle (though usually just 'Meary's').
Mnemonic
COPDifferential
C
Calcaneovalgus
Flexible, Heel down
O
Oblique Talus
Flexible, Reducible
P
Posteromedial Bow
Tibial bowing
Memory Hook:COP the differential.
Overview and Epidemiology
Definition: Congenital Vertical Talus (CVT) is a rare foot deformity characterized by a rigid dorsal dislocation of the navicular on the talus. The talus is fixed in a vertical plantarflexed position.
Epidemiology:
- Incidence: Rare (1 in 10,000).
- Associations: ~50% have associated neuromuscular or genetic disorders (Arthrogryposis, Spina Bifida, Trilstonmy 18, Neurofibromatosis).
Pathophysiology:
- Hindfoot: Fixed Equinus (Calcaneus is plantarflexed).
- Midfoot: Dorsally dislocated (Navicular on Talus).
- Result: The midfoot dorsiflexion masks the hindfoot equinus, creating the "Rocker Bottom" appearance (convex plantar surface).
Pathophysiology and Mechanisms
Key Anatomy: Understanding the relevant anatomy is crucial for diagnosis and management. The structures involved include the osseous architecture and surrounding soft tissues.
Pathomechanics: The injury mechanism often involves specific loading patterns that disrupt the structural integrity.
Classification Systems
- Idiopathic: Isolated deformity. Less common (50%).
- Teratologic (Syndromic): Associated with Arthrogryposis, Spina Bifida, Neuro conditions. More resistant.
This classification guides prognosis.
Clinical Assessment
Physical Examination:
- Look:
- "Rocker Bottom" foot: Convex sole.
- Hindfoot Valgus and Equinus (Heel is up).
- Forefoot Abducted and Dorsiflexed.
- Deep creases on dorsolateral aspect.
- Feel:
- Head of Talus: Palpable in the medial sole (prominent because it points down).
- Rigid: The deformity is stiff. You cannot plantarflex the forefoot or dorsiflex the heel.
- Systemic: Check spine (spina bifida), hips (DDH), and general tone (Arthrogryposis).
Differential Diagnosis:
- Calcaneovalgus Foot: Very common. Flexible. Heel is calcaneus (down), not equinus. Resolves with stretching.
- Oblique Talus: Less severe. Navicular reduces on talus with plantarflexion.
- Posteromedial Bowing: Apex is tibial shaft.
Investigations
X-rays (Simulated Weight Bearing / Forced Views):
- Lateral Forced Plantarflexion (KEY VIEW):
- Normal: Axis of talus lines up with 1st metatarsal.
- CVT: Axis of talus passes BELOW the 1st metatarsal. The navicular (and forefoot) remains dorsally dislocated and cannot be reduced onto the talar head.
- Lateral Forced Dorsiflexion:
- Shows fixed equinus of the calcaneus (calcaneus does not dorsiflex).
- AP View:
- Increased Talo-Calcaneal angle (Kite's angle) - indicating valgus.
Note: The navicular is not ossified until age 3, so you infer its position by the 1st metatarsal.
Management Algorithm
Dobbs Method (Reverse Ponseti)
Gold Standard (Minimally Invasive).
- Serial Casting:
- Opposite to Ponseti clubfoot.
- Foot is Plantarflexed and Inverted (to reduce the navicular onto the talus).
- NOT dorsiflexed (this worsens the deformity by "breaking" the midfoot).
- Weekly casts (usually 5-8).
- Percutaneous Pinning:
- Once navicular reduced (confirmed on X-ray), a K-wire is passed through Talo-Navicular joint.
- Often done percutaneously or mini-open.
- Achilles Tenotomy:
- To correct the fixed equinus (which remains after casting).
- Post-op: Cast for 6-8 weeks. Pin removed.
- Bracing: Shoes/AFO long term.
Surgical Technique
Dobbs Technique Step-by-Step
Phase 1: Casting
- Counter-pressure on medial talar head (pushing it up).
- Hand creates 'mold' to plantarflex and invert forefoot.
- Goal: Stretch the tight dorsal structures (EHL, EDL, TC ligament) and reduce navicular.
Phase 2: Surgery
- Mini-Open: Small incision over TN joint.
- Pinning: Visualize reduction of navicular on talus. Drive 1.6mm K-wire from dorsal Navicular into Talus.
- Percutaneous Achilles Tenotomy: Corrects the heel equinus.
- Cast: Long leg cast in neutral.
Complications
Complications
| Complication | Risk Factor | Management |
|---|---|---|
| Recurrence | Neuromuscular cause, Poor bracing | Repeat casting / Open surgery |
| AVN of Talus | Extensive open release | Fusion (salvage) |
| Stiffness | Open surgery | Observation |
| Under-correction | Insufficient casting | Revision |
| Navicular Subluxation | Pin migration/removal | Revision |
Postoperative Care
Protocol:
- Immobilization: Initial splinting/casting to protect the repair/fracture.
- Rehabilitation: Gradual Range of Motion (ROM) and strengthening as healing progresses.
- Weight Bearing: Progression depends on stability of fixation and healing.
Outcomes
- Dobbs Method: High success rate (greater than 90% initial correction). Reduced stiffness compared to open surgery.
- Untreated: Severe disability, painful calluses on sole (talar head), difficulty wearing shoes.
Evidence Base
Dobbs Method
Key Findings:
- Described the 'Reverse Ponseti' technique.
- Serial casting followed by limited surgery.
- Excellent outcomes compared to historic extensive releases.
Clinical Implication: Consider Dobbs method as first line.
Limitation: Case series
Etiology of CVT
Key Findings:
- Strong association with neuromuscular disorders (50%).
- Genetic factors involved (Hox transcription factors).
Clinical Implication: Always work up the patient for syndromes.
Limitation: Review
Forced Plantarflexion View
Key Findings:
- Described the radiographic criteria.
- Irreducibility of TN joint on forced plantarflexion is diagnostic.
Clinical Implication: Essential for diagnosis.
Limitation: Diagnostic
Minimally Invasive
Key Findings:
- Compared extensive release vs limited release (Dobbs).
- Limited release had better range of motion and functional scores.
- Less AVN risk.
Clinical Implication: Less is more.
Limitation: Comparitive
Genetics of CVT
Key Findings:
- HOXD10 mutation identified in familial CVT.
- Suggests a genetic basis for failure of foot segmentation/development.
Clinical Implication: Genetic counselling relevant.
Limitation: Basic Science
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
The Rocker Bottom Foot
EXAMINER
"What is your diagnosis and differential?"
EXCEPTIONAL ANSWER
**Congenital Vertical Talus (CVT).**
1. **Exam Findings**: 'Rocker Bottom' foot. Irreducible deformity. Talar head palpable in sole.
2. **Differential**:
- *Calcaneovalgus*: Flexible. Heel is down (calcaneus).
- *Oblique Talus*: Reducible.
- *Posteromedial Bowing*: Tibial bow.
3. **Key Step**: Check the spine/neurology! (50% associated with Arthrogryposis, Spina Bifida).
4. **Confirm**: Forced Plantarflexion Lateral X-ray.
- CVT: Talar axis stays vertical, does not align with 1st MT.
KEY POINTS TO SCORE
Rocker Bottom
Rigid
Check Spine
Forced PF X-ray
COMMON TRAPS
✗Calling it Calcaneovalgus (which is flexible)
✗Missing a neural tube defect
LIKELY FOLLOW-UPS
"What is the Dobbs method?"
"How does Calcaneovalgus differ?"
VIVA SCENARIOStandard
Dobbs Technique
EXAMINER
"Explain the casting and surgery."
EXCEPTIONAL ANSWER
**Dobbs Method (Reverse Ponseti).**
1. **Casting Phase**:
- We will apply weekly casts.
- We push the foot DOWN and IN (Plantarflexion and Inversion). **This is key** - unlike clubfoot.
- This stretches the top of the foot to put the navicular back on the talus.
2. **Surgical Phase**:
- After ~6 casts, we do a small surgery.
- *Tenotomy*: Cut the tight Achilles tendon (heel cord).
- *Pinning*: Put a wire through the joint to hold it in place.
3. **Recovery**:
- Cast for 2 months.
- Bracing/Shoes afterwards.
4. **Why?**: Better flexibility and movement than efficient open surgery.
KEY POINTS TO SCORE
Plantarflex and Invert
Reverse Ponseti
Percutaneous Pin + Tenotomy
Better than open release
COMMON TRAPS
✗Describing Ponseti (Dorsiflex/Evert) - Wrong!
✗Forgetting the tenotomy
LIKELY FOLLOW-UPS
"Why do you tenotomize the Achilles?"
"What is the recurrence rate?"
MCQ Practice Points
Diagnosis
Q: What represents the radiographic hallmark of CVT? A: Irreducible dorsal dislocation of the navicular on the talus, demonstrated on a forced plantarflexion lateral X-ray (talar axis passes below 1st metatarsal).
Association
Q: What percentage of CVT cases are associated with other anomalies? A: Approximately 50% (Neural tube defects, Arthrogryposis, Genetic syndromes).
Differentiation
Q: How do you clinically differentiate CVT from Calcaneovalgus foot? A: CVT is RIGID and the heel is in equinus. Calcaneovalgus is FLEXIBLE and the heel is in calcaneus (dorsiflexed).
Dobbs Casting
Q: In the Dobbs method for CVT, how is the foot manipulated? A: Plantarflexion and Inversion (to reduce the navicular). Dorsiflexion is AVOIDED as it causes a midfoot break.
Key Angle
Q: What happens to Kite's Angle (Talocalcaneal Angle) in CVT? A: It is increased (greater than 35-40 degrees), indicating severe hindfoot valgus.
Australian Context
- Centres: Complex foot deformities usually managed at tertiary pediatric centres (RCH, SCHN).
- Dobbs: Widely adopted as standard of care in Australia over extensive release.
High-Yield Exam Summary
Key Features
- •Rocker Bottom Foot
- •Rigid Deformity
- •Talar Head in Sole
- •50% Syndromic
X-ray Sign
- •Forced Plantarflexion View
- •Irreducible TN joint
- •Talus axis below 1st MT
- •Kite's Angle greater than 40 (Valgus)
- •Fixed Equinus on DF View
Management
- •Dobbs Method (Gold Std)
- •Cast: PF + Inversion
- •Sx: Pin + Tenotomy
- •Open Release (Historic)
Differential
- •Calcaneovalgus (Flexible)
- •Oblique Talus (Reducible)
- •Clubfoot (Wait.. opposite)
- •Review Spine/Hips
Complications
- •Recurrence (Common)
- •AVN (Open Surgery)
- •Stiff Foot
- •Navicular Subluxation