Congenital Vertical Talus — Surgical Correction

What Is Congenital Vertical Talus?

Congenital vertical talus (CVT), historically called convex pes valgus, is a rigid foot deformity present at birth. It is defined by three fixed elements:

• A vertically orientated talus — its long axis lies almost parallel to the tibial axis, so the talar head projects downward and medially into the plantar arch.
• An irreducible dorsal dislocation of the navicular onto the talar neck — the navicular is locked dorsolaterally and cannot be reduced onto the talar head by manipulation.
• A fixed equinus of the hindfoot — the calcaneus is locked in equinus and will not dorsiflex.

The combination produces the characteristic rigid rocker-bottom flatfoot with a convex plantar surface, a prominent talar head felt in the medial sole, an abducted and dorsiflexed forefoot, and tight dorsolateral structures (the long toe extensors, the peronei, and the talonavicular capsule). It is rare, with an incidence commonly cited at roughly 1 in 10,000 live births, bilateral in about half of cases, and roughly equally distributed between the sexes.

Indications for the Reverse-Ponseti (Dobbs) Pathway

Absolute Indications

• Confirmed true CVT — rigid, with a persistent talonavicular dislocation on a forced plantar flexion lateral radiograph (idiopathic or syndromic)
• Failure of the deformity to correct after an initial trial of manipulation and casting
• An older infant or toddler presenting late, where the deformity is established

Relative Indications

• Mild or partially reducible deformity — a short course of casting may fully correct the talonavicular joint, and only a percutaneous tenotomy and pinning are needed
• Syndromic or neuromuscular CVT — the same pathway applies, but with a lower threshold for limited open reduction and with explicit counselling on a higher recurrence rate

Contraindications

Absolute:

• A flexible oblique talus — this reduces on forced plantar flexion and is NOT a CVT; it is managed non-operatively (observation, stretching, occasional casting)
• A structural positional deformity that is fully correctable (e.g. a severe positional calcaneovalgus foot) — observation and stretching only
• An untreatable life-limiting underlying condition where foot surgery would not be in the child's interest (a rare, multidisciplinary decision)

Relative:

• Severe skin compromise over the dorsum of the foot (defer casting until skin recovers)
• A medically unstable neonate (delay until the child is fit for sedation or anaesthesia)

Differentiating CVT from the Flexible Look-Alikes

This is the single most important decision and the most commonly examined point. The forced plantar flexion lateral radiograph resolves it.

Evidence for the Reverse-Ponseti Method

Why the Shift Away from Extensive Release

Historically, CVT was treated by an extensive single-stage open soft-tissue release — lengthening of the long toe extensors and peronei, release of the talonavicular and calcaneocuboid capsules, a posterior release for equinus, and reduction held with multiple K-wires. While it could correct alignment, it carried real risks: talar avascular necrosis from extensive peritalar dissection, marked stiffness, wound problems over tight dorsal skin, and a not-trivial recurrence rate. The minimally invasive Dobbs method was developed specifically to obtain comparable correction with far less dissection.

The Reverse-Ponseti (Dobbs) Method

Building on Ponseti principles but applied in the opposite direction, serial weekly casting stretches the dorsolateral structures and seats the navicular onto the talar head. Once the talonavicular joint is reduced, a percutaneous tendo-Achilles tenotomy corrects the residual equinus and a percutaneous K-wire is passed across the talonavicular joint to hold the reduction while the stretched capsule heals. The reported correction rates are high, the soft-tissue dissection is minimal, and the talar AVN and stiffness burden is lower than with extensive releases.

Important Caveats in the Evidence

• The best-reported results are in idiopathic CVT. Outcomes in syndromic and neuromuscular feet are less consistent, with higher recurrence and residual deformity.
• Recurrence is closely tied to orthosis compliance — families who do not maintain full-time then night-time bracing recur more often.
• Long-term follow-up studies are still maturing; mid-term correction is excellent, but lifelong surveillance for recurrence, AVN, and stiffness is appropriate.

Key Evidence

The Deformity in Three Dimensions

Understanding the pathoanatomy is what makes the reduction make sense. The deformity is a fixed dorsal and lateral dislocation of the navicular on the talus, with the talus itself tipped into vertical alignment and the hindfoot locked in equinus.

The Talus

• The long axis of the talus is nearly vertical, lying close to the long axis of the tibia rather than running forward to the toes.
• The talar head and neck point plantarward and medially, projecting into the plantar arch — this is what you feel as the firm medial prominence in the sole and what produces the rocker-bottom.
• The talus has a tenuous, largely end-arterial blood supply through the neck and the tarsal sinus. Extensive peritalar dissection — the historical open release — endangers this supply and is the mechanism of talar avascular necrosis.

The Talonavicular Joint

• The navicular is dislocated dorsally and laterally onto the talar neck, not sitting in front of the talar head where it belongs.
• The talonavicular capsule is tight and contracted dorsolaterally; the plantar capsule is attenuated.
• Reduction requires the navicular to be brought down and around onto the talar head, which is exactly what the reverse-Ponseti casting achieves by stretching the dorsolateral structures.

The Hindfoot

• The calcaneus is fixed in equinus — the heel cord (the tendo-Achilles and the posterior ankle capsule) is tight and will not allow the heel down into a corrected position.
• This equinus is corrected LAST, after the talonavicular joint is reduced and pinned, by a percutaneous tendo-Achilles tenotomy.

The Forefoot

• The forefoot is abducted and dorsiflexed relative to the hindfoot, held there by the tight long toe extensors (extensor hallucis longus, extensor digitorum longus) and the peronei.
• These dorsolateral structures are the target of the serial casting, which plantarflexes and adducts the forefoot around the talar head.

Why It Is "Reverse" Ponseti

In a clubfoot, the deformity points inward and downward, and Ponseti casting abducts and supinates the forefoot around the talar head. In CVT, the deformity points the opposite way — the forefoot is dorsiflexed and abducted and the talonavicular joint is dislocated dorsally. The correction is therefore in the OPPOSITE direction: you plantarflex and adduct the forefoot to bring the navicular dorsally-to-plantarly around and onto the talar head. The principle of serial gentle stretching and casting, and of correcting the hindfoot equinus last with a percutaneous tenotomy, is borrowed directly from Ponseti — only the direction of correction is reversed.

The Vascular Hazard — the Talus

The talus is the structure most at risk in any CVT surgery. Its blood supply is largely through vessels entering the neck and the tarsal sinus, with limited collateral flow to the body. The historical extensive release stripped and incised widely around the talar head and neck; the consequence was a recognisable rate of avascular necrosis of the talar body. The entire rationale for moving to the minimally invasive Dobbs method was to obtain reduction while leaving the peritalar soft tissues and the talar blood supply as undisturbed as possible.

Positioning and Preparation

Patient position: Supine on a flat surface for the casting phase; for the theatre procedure, supine with the leg free. Casting is performed with the child settled (often after a feed) and can be done in an outpatient setting.

Anaesthesia / sedation: The serial casting is performed without anaesthesia. The tendo-Achilles tenotomy and talonavicular pinning are performed under sedation or a light general anaesthetic, with full sterile precautions.

Imaging: Mini C-arm fluoroscopy is used to confirm reduction of the talonavicular joint and correct K-wire placement across the joint.

Consent: Counsel specifically on the need for multiple weekly casts, the percutaneous tenotomy and pinning under sedation, the six-to-eight-week cast, the subsequent bracing commitment, and the risks of recurrence, residual deformity, talar avascular necrosis, stiffness, wound problems and pin-tract infection.

Phase 1 — Serial Casting (Reverse-Ponseti)

Aim

Stretch the tight dorsolateral structures and bring the navicular down and around onto the talar head, so that the talonavicular joint is (or nearly is) reduced before any surgery.

Technique

1. The foot is manipulated into forefoot plantar flexion and adduction around the talar head, with counter-pressure on the lateral talar head — the opposite mechanics to a clubfoot cast.
2. A long-leg plaster cast is applied with the knee flexed, holding the foot in the maximally corrected position; the hindfoot equinus is NOT corrected yet.
3. The cast is changed weekly, each time advancing the correction.
4. Typically four to seven casts are required (an average of about five).

Phase 2 — Percutaneous Tenotomy and Talonavicular Pinning

Aim

Correct the residual hindfoot equinus and hold the reduced talonavicular joint while the stretched capsule heals.

Step 1: Confirm Reduction of the Talonavicular Joint

After the final cast, assess whether the navicular sits on the talar head. If closed reduction is incomplete, plan a limited open reduction through a small dorsolateral incision over the talonavicular joint to lever the navicular onto the talar head.

Step 2: Percutaneous Talonavicular Pinning

• Under fluoroscopy, pass a smooth K-wire across the talonavicular joint from the navicular into the talar head and neck, securing the reduced joint.
• Confirm the wire position and joint reduction on mini C-arm in two planes.

Step 3: Percutaneous Tendo-Achilles Tenotomy

• Perform a percutaneous tendo-Achilles tenotomy to correct the fixed hindfoot equinus, identical in principle to the Ponseti clubfoot tenotomy.
• The heel comes down into dorsiflexion once the cord is released.

Step 4: Final Cast

• Apply a long-leg cast with the knee flexed and the foot in the corrected position, the K-wire incorporated and bent at the skin.
• The cast and wire are retained for six to eight weeks.

Phase 3 — Wire Removal and Bracing

• At six to eight weeks, remove the K-wire (typically in clinic) and apply a final short period of casting if needed.
• Transition to a foot abduction orthosis (a reverse-last or moulded ankle-foot orthosis) to maintain the corrected position.
• Bracing is full-time initially, then night-time for years, mirroring the Ponseti bracing principle — this is the single most important factor in preventing recurrence.

Casting and Bracing Protocol

Immediate Phase (Theatre to Six-to-Eight Weeks)

• A long-leg cast with the knee flexed and the foot in the corrected position, the K-wire incorporated and bent at the skin.
• Parents are counselled on cast care, elevation, and red-flag signs (fever, foul smell, loosening of the cast, exposed wire).

Wire Removal Phase (Six to Eight Weeks)

• The K-wire is removed, typically in clinic.
• A short further period of casting may be applied if correction needs consolidation.

Bracing Phase (Months to Years)

• Transition to a foot abduction orthosis or a moulded ankle-foot orthosis to hold the corrected position.
• Worn full-time initially, then reduced to night-time for several years.
• Bracing compliance is the single most important modifiable factor in preventing recurrence — it must be emphasised at every visit.

Surveillance and Follow-Up

• Regular review through growth: assess for recurrence (return of forefoot abduction, rocker-bottom), equinus, and footwear fit.
• Radiographic surveillance when recurrence is suspected, again using the forced plantar flexion lateral view.
• Lifelong follow-up is appropriate, as recurrence, AVN and stiffness can declare themselves years later.

Special Case — Neuromuscular and Syndromic CVT

• The reverse-Ponseti pathway still applies, but the threshold for a limited open reduction is lower and the recurrence rate is higher.
• Treat the foot in the context of the whole child: seating and mobility goals, the natural history of the underlying condition (for example, muscle imbalance in cerebral palsy or arthrogryposis), and the likely need for later soft-tissue balancing or bony surgery.
• Counsel families honestly: the goal in a syndromic or neuromuscular foot is a plantigrade, braceable, painless foot, and a perfect radiographic reduction may not be achievable or necessary.

Special Case — Late Presentation

• A child presenting after walking age, or with a long-standing rigid deformity, may not fully correct with casting alone.
• These feet more often require an open reduction through a limited dorsolateral and medial approach, with soft-tissue balancing, and may need later bony correction.
• The principles are unchanged: reduce the talonavicular joint, correct the equinus, preserve the talar blood supply, and brace.