Operative Management of Midfoot Cavus: The Japas V-Osteotomy and Tarsal Reconstructions

Introduction to Midfoot Cavus Deformity

Cavus foot deformities present a complex, multiplanar reconstructive challenge for the orthopedic surgeon. Characterized by an abnormally high longitudinal arch, the deformity can originate in the forefoot, midfoot, or hindfoot. Midfoot cavus specifically localizes the apex of the deformity to the midtarsal joints (talonavicular and calcaneocuboid articulations) or the naviculocuneiform joints. While the midtarsal joint is the most common site of apex angulation, the rigidity of the deformity dictates the surgical algorithm.

Historically, the management of fixed midfoot cavus relied heavily on anterior tarsal wedge osteotomies (such as the Cole osteotomy). However, these traditional techniques possess a significant biomechanical and cosmetic disadvantage: the deformity is corrected by resecting a dorsal wedge, which shortens the convex dorsal surface of the foot rather than lengthening the concave plantar surface. Consequently, the resulting foot is often shortened, widened, and thickened—a cosmetically unappealing and biomechanically altered outcome.

To circumvent these limitations, advanced osteotomy techniques, such as the Japas V-osteotomy and specific tarsometatarsal resections, have been developed. This masterclass details the indications, biomechanical principles, surgical techniques, and postoperative protocols for midfoot osteotomies, providing a comprehensive framework for the practicing orthopedic surgeon.

Pathoanatomy and Biomechanics of Midfoot Cavus

Understanding the pathoanatomy of the cavus foot is paramount to selecting the appropriate osteotomy. The deformity is typically driven by a combination of muscle imbalances, often secondary to underlying neurological conditions (e.g., Charcot-Marie-Tooth disease, spinal dysraphism, or poliomyelitis), though idiopathic cases exist.

In midfoot cavus, the primary deforming force is often a rigid, plantarflexed first ray, driven by an overactive peroneus longus overpowering a weak tibialis anterior. This plantarflexed medial column acts as a kickstand, driving the hindfoot into a secondary, flexible varus deformity during weight-bearing—a phenomenon classically evaluated using the Coleman block test.

Over time, the plantar fascia and intrinsic foot musculature contract, converting a flexible deformity into a rigid, fixed structural abnormality. Once the midtarsal or naviculocuneiform joints become rigidly deformed, soft tissue releases alone (such as a Steindler stripping) are insufficient, necessitating osseous correction via tarsal osteotomy.

Clinical Pearl: Always perform a Coleman block test during the preoperative evaluation of a cavus foot. If the hindfoot varus corrects when the first ray is allowed to drop off the block, the hindfoot deformity is flexible and driven by the forefoot/midfoot. In such cases, correcting the midfoot cavus will spontaneously correct the hindfoot varus, negating the need for a primary hindfoot osteotomy.

Preoperative Evaluation

Clinical Assessment

A meticulous clinical examination must assess the flexibility of the deformity, the presence of callosities (typically under the first and fifth metatarsal heads), and a comprehensive neurological evaluation. The Silfverskiöld test should be performed to assess for concomitant gastrocnemius equinus, which may require a concurrent lengthening procedure.

Radiographic Evaluation

Weight-bearing anteroposterior (AP) and lateral radiographs of the foot and ankle are mandatory. Key radiographic parameters include:
* Meary’s Angle (Talus-First Metatarsal Angle): Normally 0 degrees. In midfoot cavus, the angle intersects at the midtarsal or naviculocuneiform joint, with the first metatarsal plantarflexed relative to the talus.
* Hibbs Angle (Calcaneus-First Metatarsal Angle): Normally approaches 150 degrees. In a cavus foot, this angle approaches 90 degrees.
* Calcaneal Pitch: Often increased (>30 degrees) in true calcaneocavus deformities.

The Japas V-Osteotomy of the Tarsus

To address the cosmetic and functional shortcomings of the anterior tarsal wedge osteotomy, Japas described a revolutionary V-osteotomy technique. This procedure is designed to produce a more normal-appearing, functional foot by lengthening the plantar surface rather than shortening the dorsal surface.

Biomechanical Rationale

The Japas technique is a zero-resection osteotomy. No bone is excised. Instead, a V-shaped cut is made through the tarsus. The proximal border of the distal fragment is then depressed plantarward, while the metatarsal heads are elevated. This maneuver effectively flattens the longitudinal arch, correcting the cavus deformity while simultaneously lengthening the plantar surface of the foot.

Indications and Contraindications

• Indications: Recommended for moderate, fixed midfoot cavus deformities in children aged 6 years or older, adolescents, and young adults.
• Contraindications: Severe, rigid deformities with extensive degenerative joint disease; isolated hindfoot deformities; or isolated forefoot deformities.

Surgical Warning: The Japas osteotomy does not correct deformities of the hindfoot or the proximal midtarsal joint (talonavicular/calcaneocuboid). If a rigid hindfoot varus is present, it will require later or concurrent correction via a Dwyer calcaneal osteotomy or a triple arthrodesis.

Surgical Technique: Step-by-Step

1. Patient Positioning and Preparation

The patient is placed supine on the operating table with a bump under the ipsilateral hip to internally rotate the leg to a neutral position. A thigh tourniquet is applied. Prophylactic intravenous antibiotics are administered prior to inflation.

2. Soft Tissue Release

A preliminary plantar fascial release (Steindler stripping) is almost universally required to allow for the lengthening of the plantar surface. This is performed through a medial incision over the calcaneal tuberosity, releasing the plantar fascia and the origins of the short plantar muscles.

3. Surgical Approach

A dorsal longitudinal incision is made over the midfoot, centered over the apex of the cavus deformity (usually the navicular).
* Carefully dissect through the subcutaneous tissues, protecting the superficial peroneal nerve branches.
* Identify and retract the extensor hallucis longus (EHL) and extensor digitorum longus (EDL) tendons.
* Identify, mobilize, and protect the dorsalis pedis artery and the deep peroneal nerve. Retract them gently with a vessel loop.

4. The V-Osteotomy Cut

The apex of the "V" is positioned proximally, at the highest point of the cavus deformity—most commonly within the body of the navicular.
* Medial Limb: Extends from the apex in the navicular, distally and medially, passing through the medial (first) cuneiform to exit at the medial border of the foot.
* Lateral Limb: Extends from the apex, distally and laterally, passing through the lateral cuneiform and cuboid to exit at the lateral border of the foot.
* The cuts are made using an oscillating saw under continuous saline irrigation to prevent thermal necrosis. The cuts must be perpendicular to the plantar aspect of the foot to avoid inducing unintended varus or valgus malalignment.

5. Deformity Correction

Once the osteotomy is complete and the fragments are fully mobile:
* Apply dorsal pressure to the metatarsal heads to elevate the forefoot.
* Simultaneously, apply plantarward pressure to the proximal border of the distal osteotomy fragment.
* This maneuver depresses the apex of the deformity, flattens the arch, and lengthens the foot.

6. Fixation

Hold the corrected position and secure the osteotomy with internal fixation. Steinmann pins or heavy Kirschner wires (K-wires) are typically utilized.
* Drive the pins from the dorsal aspect of the midfoot, across the osteotomy site, and into the proximal tarsal bones (talus and calcaneus).
* Ensure rigid stability. Intraoperative fluoroscopy is mandatory to confirm the correction of Meary's angle and the appropriate placement of hardware.

Tarsometatarsal and Proximal Metatarsal Osteotomies

For deformities localized more distally at the tarsometatarsal (Lisfranc) joints, proximal metatarsal closing wedge osteotomies or resection-arthrodeses (as described by Jahss) may be indicated.

The Jahss Technique

Jahss described a truncated wedge resection across the tarsometatarsal joints to correct fixed forefoot equinus.

• Wedge Geometry: The base of the wedge is dorsal. Because the cavus deformity is typically driven by a severely plantarflexed first ray, the wedge of bone removed is largest at the first metatarsal-cuneiform joint. The size of the resected wedge becomes progressively smaller laterally, with minimal bone removed from the fourth and fifth tarsometatarsal joints.
• Fixation: Following the closure of the dorsal wedge, internal fixation is achieved using stout Steinmann pins driven longitudinally through the first and fifth rays, crossing the arthrodesis site into the midtarsus.

Pitfall: The Jahss procedure requires the removal of a substantial wedge of bone. Therefore, it should not be used for severe cavus deformities. Over-resection or failure to respect the complex multiplanar geometry of the midfoot can result in a devastating bayonet-shaped foot or an iatrogenic rocker-bottom deformity. Meticulous attention to detail and precise preoperative templating are absolute requirements.

Midtarsal and Naviculocuneiform Osteotomies

Cavus deformities can also occur directly at the midtarsal joints (talonavicular and calcaneocuboid) or the naviculocuneiform joints. The midtarsal joint is the most frequent site of apex angulation in the midfoot.

Management Algorithm

1. Flexible Deformity: If the midfoot deformity is flexible, a plantar fascial release combined with a calcaneal osteotomy (Dwyer) or a first metatarsal dorsiflexion osteotomy may sufficiently correct the deformity to achieve a stable, plantigrade foot.
2. Mild-to-Moderate Fixed Deformity: For fixed deformities, midfoot osteotomies (dorsal closing wedges through the midtarsal or naviculocuneiform joints) are required.

Cosmetic and Functional Considerations

Surgeons must be acutely aware of the inherent limitations of midfoot wedge resections. Any midfoot osteotomy that relies on the excision of a dorsal wedge will inevitably produce a shorter, wider, and often cosmetically unattractive foot. The severity of this shortening is directly proportional to the amount of bone removed. This underscores the superiority of the Japas V-osteotomy in appropriate candidates, as it avoids bone resection entirely.

Postoperative Protocol and Rehabilitation

The success of midfoot osteotomies relies heavily on strict adherence to postoperative immobilization and rehabilitation protocols.

• Phase 1: Immediate Postoperative (Weeks 0-6)
  • The foot is placed in a bulky Jones dressing and a well-padded short-leg cast in a neutral, plantigrade position.
  • The patient is strictly non-weight-bearing (NWB) on the operative extremity.
  • Elevation is critical to manage edema and prevent wound complications or compartment syndrome.
• Phase 2: Intermediate (Weeks 6-10)
  • At 6 weeks, radiographs are obtained to assess bone healing.
  • If Steinmann pins were left protruding through the skin, they are removed in the clinic.
  • The patient is transitioned to a short-leg walking cast or a rigid controlled ankle motion (CAM) boot.
  • Progressive weight-bearing is initiated based on radiographic evidence of consolidation.
• Phase 3: Rehabilitation (Weeks 10+)
  • Once clinical and radiographic union is achieved, the patient transitions to supportive footwear, often requiring custom orthotics to support the newly reconstructed arch.
  • Physical therapy focuses on restoring ankle and subtalar range of motion, strengthening the peroneals and tibialis anterior, and gait retraining.

Complications and Salvage Strategies

Despite meticulous surgical technique, complications can arise following midfoot osteotomies for cavus deformities.

• Undercorrection / Recurrence: The most common complication. Often results from inadequate soft tissue release (failure to perform a complete Steindler stripping) or failure to address a concomitant hindfoot deformity. Salvage may require a triple arthrodesis.
• Overcorrection (Rocker-Bottom Foot): Caused by excessive dorsal wedge resection or over-depression of the distal fragment in a Japas osteotomy. This is a severe complication that drastically alters foot biomechanics, often requiring complex revision arthrodesis.
• Nonunion / Delayed Union: The midfoot has a robust blood supply, but excessive periosteal stripping or thermal necrosis from the saw blade can lead to nonunion. Treatment involves revision with rigid internal fixation and autologous bone grafting.
• Neurovascular Injury: The deep peroneal nerve and dorsalis pedis artery are at high risk during dorsal approaches to the midfoot. Meticulous dissection and gentle retraction are mandatory.
• Cosmetic Dissatisfaction: Patients must be counseled preoperatively that dorsal wedge osteotomies will result in a shorter, wider foot. Managing patient expectations is as critical as the surgical execution itself.

Conclusion

The operative management of midfoot cavus demands a profound understanding of foot biomechanics and a tailored surgical approach. While traditional anterior wedge osteotomies remain in the surgical armamentarium, their tendency to shorten and widen the foot makes them less desirable for moderate deformities. The Japas V-osteotomy represents a biomechanically elegant solution, correcting the deformity by lengthening the plantar surface without sacrificing bone stock. When combined with appropriate soft tissue releases and precise internal fixation, tarsal osteotomies can reliably restore a stable, plantigrade, and functional foot for patients suffering from debilitating cavus deformities.