Congenital Vertical Talus

Definition: Congenital vertical talus (CVT), or "congenital convex pes valgus", is a rigid, irreducible dorsal dislocation of the navicular on the head of the talus. The talus is locked in a near-vertical, plantarflexed position, producing the characteristic rocker-bottom foot.

Epidemiology:

• Incidence: Rare, approximately 1 in 10,000 live births. No strong sex predilection.
• Laterality: Bilateral in roughly half of cases.
• Associations: Around 50% are non-idiopathic (teratologic), occurring with neuromuscular or genetic disorders — arthrogryposis, myelomeningocele/spina bifida, trisomy 13/18, and chromosomal/single-gene syndromes. An autosomal-dominant familial form linked to a HOXD10 mutation has been described.

The four key deformities:

• Hindfoot equinus: The calcaneus is fixed in plantarflexion, tethered by a contracted tendo-Achilles and posterior capsule.
• Hindfoot valgus: Increased talocalcaneal divergence.
• Midfoot dorsiflexion / dorsal dislocation: The navicular sits dorsal to the talar neck, held by contracted dorsal structures (tibialis anterior, extensor digitorum longus, extensor hallucis longus, peroneus tertius, and the dorsal talonavicular capsule). The peroneals and tibialis anterior become displaced and act as deforming dorsiflexors.
• Forefoot abduction and dorsiflexion.

The hindfoot equinus is masked by the dorsiflexed midfoot — the sole becomes convex (rocker-bottom), with the prominent talar head palpable medially in the sole. The deformity is rigid and irreducible, which is the cardinal feature separating CVT from its flexible mimics.

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:

1. Calcaneovalgus Foot: Very common. Flexible. Heel is calcaneus (down), not equinus. Resolves with stretching.
2. Oblique Talus: Less severe. Navicular reduces on talus with plantarflexion.
3. Posteromedial Bowing: Apex is tibial shaft.

X-rays (Simulated Weight Bearing / Forced Views):

1. 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.
2. Lateral Forced Dorsiflexion:
   • Shows fixed equinus of the calcaneus (calcaneus does not dorsiflex).
3. 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.

Protocol (Dobbs method):

• Immobilization: Long-leg cast in the corrected position for ~6-8 weeks. The talonavicular K-wire is typically removed at ~5-6 weeks.
• Bracing: After cast removal, an ankle-foot orthosis (AFO) or solid-ankle shoe is used to maintain correction. Many surgeons use a foot-abduction-style brace/AFO part-time for 1-2 years, mirroring the maintenance phase of Ponseti clubfoot care.
• Weight bearing: Permitted once the cast is removed and the foot is plantigrade; mobilisation is encouraged.
• Surveillance: Recurrence (especially in teratologic feet) is the dominant late problem, so children are followed until skeletal maturity. Early recurrence is managed with repeat casting; established relapse may need revision surgery.

• 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.

Global epidemiology:

• Rare congenital deformity, ~1 in 10,000 live births; bilateral in roughly half.
• Around 50% are teratologic, associated with arthrogryposis, myelomeningocele, trisomies (13/18) and other syndromes — proportions vary with referral pattern and access to prenatal screening.

Practice consensus (no single national guideline governs CVT):

High- vs limited-resource variation:

• Where neonatal screening and paediatric orthopaedic services exist, most feet present and are cast in infancy with minimally invasive surgery.
• In limited-resource or remote settings, late/neglected presentation is more common, shifting the balance toward salvage procedures (naviculectomy, talectomy, later triple arthrodesis). Reverse-Ponseti casting is attractive globally because it is low-cost and avoids major open surgery.
• No dedicated implant registry exists for CVT (unlike arthroplasty); evidence rests on single-centre series, so practice is guided by consensus rather than registry data.