Cavovarus Foot Deformity

Cavovarus foot is a complex three-dimensional deformity: a high medial longitudinal arch (cavus), hindfoot varus and forefoot adduction. It is progressive, and early recognition and staging prevent the severe fixed deformity that requires triple arthrodesis.

Causes. In adults the commonest cause is Charcot-Marie-Tooth disease (CMT), a hereditary motor and sensory neuropathy that accounts for 66% of adult cavovarus. Across all causes:

• Neurological, 75%: CMT, spinal dysraphism, residual polio, cerebral palsy
• Idiopathic, 20%: no underlying cause identified
• Traumatic, 5%: compartment syndrome, malunion, neuroma

CMT type 1A is the most common subtype. It is autosomal dominant, results from duplication of the PMP22 gene, and makes up 70% of CMT cases.

Natural history. The deformity worsens over years as the muscle imbalance continues. It leads to lateral ankle instability, with recurrent sprains from varus heel strike, and to peroneal tendinopathy and stress fractures.

Pressure and wear. The plantar-flexed first ray and claw toes concentrate pressure and cause metatarsalgia, and the midfoot and ankle degenerate, with arthritis by the fifth to sixth decade.

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The muscle imbalance in CMT. Peroneal nerve dysfunction selectively weakens peroneus brevis (eversion) and tibialis anterior (dorsiflexion), and with them the long toe extensors, EHL and EDL. Posterior tibialis, supplied by the tibial nerve, stays strong and overpowers the weak peroneals, pulling the hindfoot into varus. The process is dynamic and progressive.

The intrinsics and the toes. Weak intrinsic foot muscles lead to claw toes and an elevated arch. The clawing is flexor overpull against intrinsic weakness, and plantar fascia release helps it. The high arch comes from first-ray plantar flexion and intrinsic imbalance, and a tight Achilles from posterior muscle overactivity adds an equinus component that may need lengthening.

The tripod. The standing foot rests on three points: the first metatarsal head, the fifth metatarsal head and the heel. The weak peroneals cannot resist the pull of peroneus longus, so the first metatarsal plantar-flexes and, when the patient stands, its head is too low. The forefoot pronates to bring it to the ground, and that forefoot pronation forces the hindfoot into functional varus.

Primary and secondary deformity. In most cases the plantar-flexed first ray is the primary driver and the hindfoot varus is secondary to it. If the hindfoot is flexible on the Coleman block, correcting the first ray often corrects the hindfoot without a calcaneal osteotomy; only fixed hindfoot varus needs one. Dynamic gait data have since questioned how universal this model is (see Controversies).

The deformity is classified by its components, by its cause and by its severity.

History. CMT is autosomal dominant, so ask whether parents or siblings are affected, and whether the foot has been this shape since childhood or has changed recently and is getting worse.

The complaint. Recurrent lateral ankle sprains are very common. Ask where it hurts: the lateral foot (peroneal tendinopathy), the plantar forefoot (metatarsalgia) or the ankle (arthritis). Ask about difficulty on uneven ground, running or balancing, and about footwear: can they fit standard shoes with the high arch?

Neurological symptoms. Ask about stocking-glove numbness from the sensory neuropathy, and about anterior compartment weakness with foot drop or a steppage gait. CMT also affects the hands, so ask about fine motor difficulty. Loss of proprioception increases the risk of falls.

Standing. From behind, look at hindfoot varus, medial arch height and forefoot adduction. From the front, with the feet pointing straight ahead, a visible medial heel pad is the peek-a-boo heel sign of hindfoot varus. Watch the gait for lateral foot strike, ankle instability and a steppage gait if tibialis anterior is weak.

The Coleman block test. This is the single most important clinical examination in the cavovarus foot and the gold standard for assessing flexibility. The patient stands with the lateral foot, the fourth and fifth metatarsals, on a 1-inch block, so that the first and second rays hang free off its edge, and the examiner watches the calcaneus from behind. With the plantar-flexed rays off the block, the test shows whether the hindfoot varus is driven by the forefoot or fixed.

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Seated. With the foot unloaded, test flexibility and power:

• Passively correct the hindfoot varus: does it reach neutral, or go beyond?
• Can the first metatarsal be dorsiflexed to neutral?
• Ankle dorsiflexion with the knee extended and then flexed, the Silverskiöld test, separates isolated gastrocnemius tightness from combined gastrocnemius-soleus tightness
• Grade power 0-5: in CMT peroneus brevis is weak, tibialis anterior is weak with a possible drop foot, posterior tibialis is overactive and gastrocnemius is usually normal

Neurological examination. Anterior and lateral compartment weakness follows the peroneal nerve distribution, sensory loss is in a stocking-glove pattern, and the Achilles and patellar reflexes are often absent in CMT. Wasting of the anterior and lateral leg gives the stork leg, or inverted champagne bottle, a diagnostic sign. Look too for claw toes and, in the hand, intrinsic wasting (ape hand deformity).

Ankle stability. Chronic lateral instability is common, so perform the anterior drawer and talar tilt tests.

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Weight-bearing radiographs come first, and each view answers its own question:

• AP foot: forefoot adduction, the metatarsal break pattern and degenerative change
• Lateral foot: calcaneal pitch, the Meary and Hibbs angles, and first metatarsal plantar flexion
• AP ankle: ankle arthritis, and talar tilt from chronic instability
• Hindfoot alignment (Saltzman) view: a weight-bearing coronal view that quantifies the varus or valgus position of the calcaneus under the tibia, a plumb line falling medial to the heel indicating varus. It is essential for planning and for confirming neutral alignment intraoperatively after a calcaneal osteotomy.

The lateral angles. Three are measured on the weight-bearing lateral:

• Calcaneal pitch (calcaneal inclination angle), between the plantar surface of the calcaneus and the floor. Normal is about 20 degrees (roughly 20-30); a pitch over about 30 degrees indicates a calcaneocavus (hindfoot-driven) high arch.
• Meary's angle (talo-first metatarsal angle), between the long axes of the talus and the first metatarsal. Normally these are colinear, about 0 degrees. In cavus the line breaks with its apex pointing dorsally, and the level of that apex (forefoot, midfoot or a smooth curve) localises the deformity.
• Hibbs angle (calcaneal-first metatarsal angle), between the long axes of the calcaneus and the first metatarsal. Normal is roughly 150-175 degrees; under about 150 degrees reflects an elevated arch, and the more acute the angle, the higher the arch.

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MRI of the foot and ankle is for surgical planning. It shows the peroneal tendons, where split tears and subluxation are common with a varus hindfoot; the lateral ligament complex, with chronic ATFL and CFL injury from recurrent sprains; the ankle articular cartilage; and the quality of the plantar fascia and posterior tibial tendon.

Neurological work-up, when CMT is suspected:

• Nerve conduction studies: reduced motor and sensory conduction velocities in CMT type 1, the demyelinating form
• Electromyography: a denervation pattern in the affected muscles
• Genetic testing: PMP22 duplication for CMT1A
• MRI of the spine: if there is any suspicion of spinal dysraphism or a tethered cord

Dynamic assessment is optional. Pedobarography on a pressure mat demonstrates lateral column overload and forefoot pressure concentrated under the first metatarsal, and gait analysis quantifies ankle instability, varus thrust and the lateral foot contact pattern.

The first fork is neurological or not. A bilateral, symmetric, progressive cavovarus with a family history is CMT until proven otherwise. A unilateral or rapidly progressive cavovarus mandates spinal imaging to exclude a tethered cord or intraspinal lesion before any foot surgery; missing this leads to relentless recurrence.

Who. Non-operative treatment is indicated for:

• Mild deformity with minimal symptoms
• A patient unfit for surgery because of medical comorbidities
• A stable, non-progressive neurological condition
• A patient who refuses surgery or wants to delay it
• Elderly, low-demand patients with acceptable function

Orthoses and footwear. The mainstay is a custom foot orthosis with a lateral heel wedge, which shifts weight medially and unloads the lateral column. High-backed shoes or ankle braces help lateral ankle instability, accommodative padding (plantar metatarsal pads) eases metatarsalgia, rocker-bottom soles reduce forefoot pressure, and an ankle-foot orthosis (AFO) supports severe drop foot in CMT.

The protocol runs in three phases:

• Weeks 1-6, symptom control: NSAIDs, activity modification and ice for acute exacerbations; orthotic fitting; footwear with extra depth, a wide toe box and a rigid shank.
• Weeks 6-12, strengthening: resistance-band eversion exercises for the peroneals, which will not reverse CMT but maintain function; towel curls and marble pick-up for the intrinsics, to slow claw toe progression; single-leg balance and wobble-board work for ankle proprioception.
• Ongoing, monitoring: annual reassessment, with radiographs to monitor progression and examination for worsening varus, and orthoses replaced or modified as the deformity progresses.

When it fails. Non-operative management is temporising, not curative. Offer surgery if the deformity worsens, pain increases or function declines significantly, and in particular for:

• Progressive deformity despite orthoses
• Recurrent ankle sprains, more than two a year
• Severe metatarsalgia affecting walking
• Lateral foot pain from peroneal overload
• Developing ankle arthritis
• Inability to fit into shoes

The Coleman block result sets the plan. A flexible hindfoot is corrected through the forefoot, a fixed hindfoot also needs the calcaneus realigned, and a rigid, arthritic foot is a salvage problem. Severe deformity is never corrected all at once: single-stage correction carries a high complication rate, and staging allows assessment after each stage to avoid overcorrection.

Flexible Hindfoot (Coleman Negative)Fixed Hindfoot (Coleman Positive)Severe/End-Stage Deformity

The goal is to correct the plantar-flexed first ray. That removes the forefoot pronation and with it the functional hindfoot varus, so the hindfoot corrects to neutral without a calcaneal osteotomy, as the preoperative Coleman block predicted. For a flexible deformity, soft-tissue procedures and the first metatarsal osteotomy are sufficient.

1. Plantar fascia release from the calcaneus, with release of the intrinsic origin. It drops the arch and reduces the plantar force on the first metatarsal. Do not over-release: that can create a flatfoot.
2. First metatarsal dorsiflexion osteotomy, a dorsal closing wedge at the base (preferred) or a Cotton opening wedge of the medial cuneiform, fixed with a plate and screws or staples. The aim is to bring the first metatarsal to neutral and eliminate the tripod effect.
3. Peroneus longus to brevis transfer. Peroneus longus plantar-flexes the first metatarsal; dividing it removes that deforming force, and weaving it into the weak brevis (the CMT pattern) improves eversion strength.
4. Claw toe correction, if needed. A Girdlestone-Taylor flexor-to-extensor transfer moves FDL or FHL to the dorsal hood to extend the toes; severe fixed clawing needs fusion of the PIP or DIP joints. The clawed hallux is corrected by the Jones procedure.
5. Gastrocnemius recession, if needed. A positive Silverskiöld test, ankle dorsiflexion of less than 5 degrees with the knee extended that improves with the knee flexed, indicates isolated gastrocnemius tightness, treated by a Strayer recession at the musculotendinous junction.

The goal is to correct the forefoot and the fixed hindfoot with staged bone and soft-tissue procedures. Fixed hindfoot varus requires bone realignment, and soft-tissue procedures alone will fail.

1. Stage 1, forefoot correction, as for the flexible foot: plantar fascia release, first metatarsal dorsiflexion osteotomy, peroneus longus to brevis transfer and claw toe correction. Reassess at 3-6 months, and if hindfoot varus persists, proceed to stage 2.
2. Stage 2, calcaneal lateralising osteotomy, a second operation when needed: a Dwyer lateral closing wedge, which removes a wedge from the lateral wall, or a lateralising slide, which translates the posterior calcaneus laterally. Shifting the calcaneal axis lateral to the tibial axis converts the varus moment arm to neutral or slight valgus. Fixation is with 1-2 screws.
3. Stage 3, midfoot osteotomy, a rare third operation. The Cole osteotomy, a dorsal closing wedge through the midfoot (cuneiforms and cuboid), reduces arch height when severe cavus persists after forefoot and hindfoot correction. It carries a high nonunion rate and a risk of stiffness.

Tendon transfers for dynamic balance are added during stage 1 or 2. A very weak peroneus brevis calls for a split posterior tibial transfer (see Surgical Technique); if tibialis anterior is weak, consider transferring tibialis posterior to the dorsum (the Bridle procedure).

The biggest pitfall of the calcaneal osteotomy is overcorrection into valgus (see Complications), so hindfoot alignment is checked on intraoperative fluoroscopy, with a Saltzman view, before final fixation.

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Salvage procedures are reserved for end-stage deformity or failed reconstruction. They sacrifice motion for alignment and pain relief.

Triple arthrodesis

Indications

Fixed cavovarus with subtalar/midfoot arthritis, failed reconstruction

Key Technical Points

Fuse subtalar, talonavicular, calcaneocuboid in corrected position. Preserve ankle joint.

Outcomes

Reliably corrects deformity, sacrifices hindfoot motion, ankle arthritis risk

Supramalleolar osteotomy

Indications

Varus ankle arthritis, tibial plafond varus tilt from chronic deformity

Key Technical Points

Closing wedge medial tibial osteotomy to realign ankle joint. Can combine with triple.

Outcomes

Offloads lateral ankle, may delay need for ankle fusion

Ankle arthrodesis

Indications

End-stage ankle arthritis from chronic instability, post-traumatic

Key Technical Points

Fuse ankle in neutral dorsiflexion, neutral hindfoot alignment. Correct varus tilt.

Outcomes

Eliminates pain, sacrifices motion, increases midfoot stress

Procedure	Indications	Key Technical Points	Outcomes
Triple arthrodesis	Fixed cavovarus with subtalar/midfoot arthritis, failed reconstruction	Fuse subtalar, talonavicular, calcaneocuboid in corrected position. Preserve ankle joint.	Reliably corrects deformity, sacrifices hindfoot motion, ankle arthritis risk
Supramalleolar osteotomy	Varus ankle arthritis, tibial plafond varus tilt from chronic deformity	Closing wedge medial tibial osteotomy to realign ankle joint. Can combine with triple.	Offloads lateral ankle, may delay need for ankle fusion
Ankle arthrodesis	End-stage ankle arthritis from chronic instability, post-traumatic	Fuse ankle in neutral dorsiflexion, neutral hindfoot alignment. Correct varus tilt.	Eliminates pain, sacrifices motion, increases midfoot stress

When to abandon reconstruction. The indications for salvage arthrodesis over joint-sparing reconstruction are:

• Fixed, rigid deformity that cannot be passively corrected
• Severe subtalar or ankle arthritis (Kellgren-Lawrence grade 3-4)
• Age over 60 with low demand
• Multiple failed previous operations
• A patient willing to trade motion for stability and pain relief

Consent. Discuss each of these before any reconstruction:

• Infection: 2-3% superficial, 1% deep
• Nerve injury: the sural nerve with the lateral approach, the medial plantar nerve with plantar fascia release
• Nonunion of a calcaneal or midfoot osteotomy
• Overcorrection to valgus, which is difficult to salvage and may need revision
• Recurrence, if the underlying cause (CMT) is progressive
• The need for staged procedures: severe deformity may require 2-3 operations

Equipment. An oscillating saw and osteotomes; small-fragment plates and screws for the first metatarsal and cannulated screws for the calcaneus; a tendon passer and whipstitch sutures (FiberWire) for the transfers; K-wires for temporary fixation during correction; and a C-arm, which is essential for the bone cuts.

Plantar Fascia Release1st MT OsteotomyCalcaneal OsteotomyTendon Transfers

Plantar fascia release is the cornerstone of soft-tissue correction: it drops the arch and reduces tension on the plantar structures. The approach is plantar medial (Steindler stripping) or plantar lateral (endoscopic). For the plantar medial approach:

1. Position and incision. Supine with a bump under the ipsilateral hip and the foot externally rotated. Make a 3-4 cm longitudinal incision over the plantar medial foot, centred on the medial calcaneal tuberosity; palpate the tuberosity and stay medial to avoid the lateral plantar nerve.
2. Release. Identify the plantar fascia, a thick white band, and the origins of abductor hallucis and flexor digitorum brevis. Release the fascia sharply from its calcaneal origin, then strip the intrinsic origins (Steindler stripping) to drop the arch maximally, staying on bone.
3. Closure. Irrigate, close the deep fascia with absorbable suture and the skin with nylon, and apply a compression dressing to prevent haematoma.

Medial Plantar Nerve Danger

The medial plantar nerve runs deep to abductor hallucis and is at risk in the plantar medial approach; staying on bone during the release avoids it. Injury causes permanent plantar numbness and a painful neuroma. Test sensation before discharge.

The dorsal closing wedge elevates the plantar-flexed first metatarsal, the primary deformity, to neutral.

1. Exposure. Supine, foot flat on the table. Make a 4-5 cm dorsal incision over the first metatarsal base, between EHL and EHB, and clear the periosteum dorsally, protecting EHL medially and the dorsalis pedis artery laterally.
2. Planning. The wedge is typically 5-8mm dorsally, measured on the preoperative lateral radiograph. It sits 1-1.5 cm distal to the first TMT joint to preserve that joint, apex plantar, leaving the plantar hinge intact for stability.
3. Cut and fixation. Make the proximal cut perpendicular to the shaft with an oscillating saw and angle the distal cut dorsally to create the wedge, full width at the dorsal cortex and 0mm at the plantar cortex. Remove the dorsal bone and compress to close the gap, then fix with a 3-4 hole dorsal plate or two 3.5mm cortical screws. On the lateral fluoroscopic view the first metatarsal should align with the lesser metatarsals, with no plantar flexion.
4. Closure. Irrigate, close in layers (periosteum, subcutaneous tissue, skin) and apply a compression dressing to reduce swelling.

The Cotton alternative. A plantar-based opening wedge in the medial cuneiform, through a dorsal approach, with bone graft and plate fixation. It avoids a first metatarsal osteotomy, but has a higher nonunion rate, the cuneiform being a small bone with a limited blood supply, and it elevates the entire medial column, which may be excessive.

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The calcaneal osteotomy is indicated for fixed hindfoot varus (Coleman positive) that persists despite forefoot correction. The lateralising slide:

1. Position and exposure. Lateral decubitus with the affected side up, or prone. Make a 6-8 cm oblique incision over the lateral calcaneus, centred 2 cm distal to the tip of the fibula. Identify and protect the peroneal tendons, incise the periosteum and expose the lateral calcaneal wall.
2. Osteotomy. Oblique, from posterosuperior to anteroinferior and parallel to the posterior facet, starting 1-1.5 cm distal to the posterior facet to stay posterior to the subtalar joint, and aimed toward the anterior process of the calcaneus to exit plantar-medially. Complete it with the oscillating saw; the plantar cortex may need an osteotome.
3. Translation. Translate the posterior fragment laterally 8-10mm, measured with a ruler or calibrated on the C-arm. The hindfoot should be neutral or in slight valgus on AP fluoroscopy (Saltzman view). Hold it with a temporary K-wire while drilling for the screws.
4. Fixation. Two 6.5mm or 7.0mm cannulated screws from the posterior tuberosity across the osteotomy into the anterior calcaneus, parallel to the plantar surface and aimed anterosuperiorly. Final fluoroscopy: an AP ankle (Saltzman) view to confirm a neutral hindfoot and a lateral foot view for screw position.
5. Closure. Irrigate, close the periosteum over bone, then the subcutaneous layer and skin, and apply a well-padded posterior splint in neutral hindfoot alignment.

Sural Nerve at Risk

The sural nerve runs along the lateral border of the Achilles tendon and courses inferiorly behind the lateral malleolus, where it is at high risk in the lateral calcaneal approach. Identify it early and retract it posteriorly. Injury causes permanent lateral foot numbness and a painful neuroma.

The minimally invasive alternative uses prone positioning and two convergent wires to bound the calcaneal wedge before burr resection, with fluoroscopy confirming the safe corridor and the correction.

The Dwyer alternative. A lateral-based wedge is removed from the calcaneus instead of translating it. It corrects the varus angulation directly, but shortens the calcaneus, alters the Achilles moment arm and has a higher nonunion rate than the slide, which is preferred in modern practice.

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The peroneus longus to brevis transfer removes a deforming force, since longus plantar-flexes the first metatarsal, and augments weak eversion through brevis.

1. Exposure. A 3-4 cm incision over the lateral foot at the level of the cuboid, distal to the tip of the fibula. Peroneus longus courses deep to peroneus brevis and then turns plantar under the cuboid; brevis inserts on the base of the fifth metatarsal.
2. Divide longus as far distally as possible, at the entrance to the cuboid tunnel. Deliver the proximal stump through the lateral incision and prepare its end with a whipstitch (FiberWire or Ethibond #2).
3. Weave it into brevis with a side-to-side Pulvertaft weave of 3 passes, tensioned with the foot held in neutral eversion and the knee flexed 90 degrees, and secure with multiple non-absorbable sutures.
4. Closure in layers, with a compression dressing.

Split posterior tibial transfer. If peroneus brevis is very weak (CMT grade 2 or less) and posterior tibialis is overpowering it into dynamic varus, consider splitting the posterior tibial tendon longitudinally and rerouting the lateral half through the interosseous membrane to peroneus brevis or the lateral cuneiform. This removes a varus deforming force and augments the weak eversion. Do not transfer the whole tendon: that leaves the medial arch unsupported.

The problem. In cavovarus, especially CMT, a weak tibialis anterior recruits extensor hallucis longus (EHL) to help dorsiflex the ankle. The over-recruited EHL cocks up the hallux into a clawed great toe, the MTP joint hyperextended and the IP joint flexed. Because its distal pull acts on the toe rather than the metatarsal, it also indirectly depresses (plantarflexes) the first metatarsal and worsens the cavus.

The operation (Robert Jones, 1916). The EHL is detached distally and transferred into the neck of the first metatarsal, and the hallux IP joint is fused (or tenodesed). This achieves three things at once:

• It removes the deforming plantarflexion force on the first ray
• It converts EHL into a first metatarsal dorsiflexor, augmenting correction of the plantarflexed first ray
• It straightens the clawed hallux, the IP fusion preventing recurrent clawing

Where it fits. It is a soft-tissue adjunct performed with the plantar fascia release and first metatarsal osteotomy during the forefoot-correction stage: the hallux equivalent of the Girdlestone-Taylor flexor-to-extensor transfer used for the clawed lesser toes.

Recurrence in CMT. The 20-30% recurrence of deformity in CMT patients is quoted over 10-15 years.

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Predictors of a poor outcome. In the patient, they are:

• CMT type 1A, which has a higher recurrence rate than idiopathic cavovarus
• Severe preoperative deformity, with a calcaneal pitch over 40 degrees
• Fixed deformity that cannot be passively corrected to neutral
• Age over 50: lower activity demands but more medical comorbidity
• Smoking, which doubles the nonunion risk and triples the wound complication risk

In the surgery. Inadequate correction leaves residual varus and recurrent lateral ankle instability, while overcorrection to valgus creates new problems. Single-stage correction of severe deformity has a high complication rate compared with a staged approach. Failing to address every component, such as correcting the hindfoot but not the first ray, predicts a poor result, as does nonunion of an osteotomy, which requires revision and delays recovery.

Counselling in CMT. Surgery delays progression and improves function, but it does not cure the underlying neuropathy, and revision surgery may be needed. Lifelong custom orthoses are essential. Even so, most CMT patients report significant improvement in pain, ankle stability and the ability to wear shoes, and operating while the deformity is moderate, before severe fixed changes, gives the best long-term results.

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Is the deformity truly forefoot-driven? The classic teaching, a plantarflexed first ray driving hindfoot varus through the tripod effect, underpins the Coleman block test. Dynamic pedobarography (Ferguson et al., 2024) found first-ray-first contact in only about 40% of varus CMT feet, suggesting that many feet are pre-positioned in varus by progressive muscle imbalance rather than purely forefoot-driven. The block test remains useful but may oversimplify a multifactorial deformity.

Which calcaneal osteotomy? No high-level trial defines the optimal hindfoot osteotomy. The lateral translation (slide) and the Z (Malerba) osteotomy are now generally preferred over the classic Dwyer lateral closing wedge because they correct alignment without shortening the calcaneus or altering the Achilles moment arm. Comparative outcome data remain limited and largely retrospective.

Joint-sparing reconstruction or triple arthrodesis? Long-term data favour joint-sparing surgery in flexible deformity, with lower arthritis and reoperation rates than historical fusion series. The threshold of rigidity and arthritis at which to abandon reconstruction for triple arthrodesis is not precisely defined, and remains a judgement call.

Timing and transfer selection. Whether to operate early in flexible CMT to delay fixed changes, and which tendon transfers best balance a progressive neuropathy, are debated. Because CMT continues to progress, no transfer fully prevents recurrence, and revision over a lifetime is common.