INTRODUCTION
Definition
A defomity with an elevated longitudinal arch with calcaneus or varus hindfoot due to fixed plantar flexion of the forefoot, or, less frequently, as a result of excessive calcaneal dorsiflexion (calcaneus hindfoot).Epidemiology
- Two-thirds of the patients with pes cavus have an underlying neurologic disorder, most commonly
- Charcot-Marie-Tooth disease (CMT).
- The condition is seen in both pediatric and adult populations.
- Bilateral cases are often due hereditary or congenital causes.
Etiology
Overview: The exact etiology is unknown.Neurologic conditions: Up to 67% of cases due to neurologic disorder. Conditions which present with cavovarus foot include:
- Charcot-Marie-Tooth disease (most commonly). Due to a defect in the gene responsible for peripheral myelin protein 22 (PMP22).
- Cerebral palsy.
- Polio.
- Freidreich’s ataxia.
- Myelomeningocele.
- Spinal cord lesions (injury, tumor, or abnormality).
Traumatic condition:
- Talus fracture malunion.
- Compartment syndrome.
- Crush injury.
Patoanatomy
The primary structural problem is forefoot plantar flexion.- Muscle imbalance generate deformity:
- Strong peroneus longus and posterior tibialis overpower tibialis anterior and peroneus brevis, resulting in plantarflexion of the first ray and forefoot pronation with compensatory hindfoot varus and a depressed first metatarsal head. First ray plantar flexion is more commonly caused by intrinsic weakness and contracture.
- Tthe medial forefoot strikes the ground first with the first metatarsal plantarflexed and forefoot pronated.
- For the lateral half of the foot to be in contact with the ground, the subtalar joint supinates to bring the lateral forefoot to the ground and maintain three-point contact, resulting in hindfoot varus.
- Hindfoot varus can become rigid with time, while initially flexible, as the plantar fascia contracts.
- Extensor hallucis longus activation will lead to dorsiflexion of the foot over time causing shortening of plantar fascia and resultant cavus.
- Strong peroneus longus and posterior tibialis overpower tibialis anterior and peroneus brevis, resulting in plantarflexion of the first ray and forefoot pronation with compensatory hindfoot varus and a depressed first metatarsal head. First ray plantar flexion is more commonly caused by intrinsic weakness and contracture.
CLINICAL FEATURES
Symptoms
- Patients may complain about ankle instability (ankle sprains).
- Due to peroneal tendon pathology.
- Lateral foot pain: Caused by excessive weight bearing by the lateral foot due to deformity. May result in 5th metatarsal stress fracture.
- Painful plantar callus: Seen under first metatarsal head and 5th metatarsal head or base.
- Plantar fasciitis: Caused by contracture of the plantar fascia due to elevated medial arch, forefoot pronation and tight gastronemius.
Signs
General examination:- Neurologic examination and a family history are essential. Consider genetics/neurology referral (DNA testing for CMT).
- Unilateral involvement: Suggests a focal diagnosis (e.g. spinal cord anomaly, spinal cord tumor tethered spinal cord, or nerve injury).
- Bilateral involvement: Common with Charcot-Marie-Tooth disease. Though, asymmetry may be seen in Charcot-Marie-Tooth disease.
- Spine exam: Scoliosis is suggestive of CMT.
- Gait: The patient will have an altered gait with unstable base of support and increased double limb stance and decreased single limb stance.
- Cavusvarus deformity is characterized by:
- Cavus (elevated longitudinal arch).
- Plantarflexion of the 1st ray and forefoot pronation.
- Hindfoot varus.
- Forefoot adduction.
- Prominent first metatarsal fat pads.
- Wasting of first dorsal interosseous muscle of the hand is suggestive of CMT.
- Silfverskiöld test: Check the dorsiflexion with both knee flexion and knee extension.
- If there is tightness only with knee extension, then gastrocnemius is tight.
- Gastronemius tightness often present with cavovarus foot.
- If there is also tightness with knee flexion, then soleus is also tight.
- If there is tightness only with knee extension, then gastrocnemius is tight.
- Coleman block test (lateral block test): Used to assess hindfoot flexibility of the cavovarus foot. Hindfoot flexibility is assessed by placing a 1-inch block under the lateral border of the foot. A flexible hindfoot corrects to neutral with a lift placed under the lateral aspect of the foot.
DIAGNOSIS
Conventional Radiography
Projections (views): Weight-bearing views are required.- Standing AP and lateral radiographs of the ankle.
- Standing AP, lateral and oblique radiographs of the foot.
- AP of the foot:
- Talocalcaneal angle: < 20° (normal is 20-45°) suggests hindfoot varus.
- Talonavicular overcoverage: The talonavicular angle > 7° indicates forefoot adduction.
- Metatarsal overlap: Indicates forefoot pronation.
- Lateral of the foot:
- Meary angle (lateral talo-first metatarsal angle): Increased, > 4° apex dorsal. The long axis of the talus will intersect the long axis of the first metatarsal dorsally on the lateral view of the foot. The normal value is 0° to 5°. The is a break in Meary line caused by plantarflexion of the first ray.
- Calcaneal pitch (calcaneal inclination angle): Increased, > 30°, indicates a calcaneocavus foot. Intersection of a line running along the undersurface of the calcaneus and the floor.
- Sinus tarsi see-through sign and double talar dome sign: Occurs due to external rotation of the ankle and hindfoot relative to the xray cassette, which is placed along the medial border of the adducted forefoot.
- Other signs:
- The cuboid is bell-shaped.
- There is an increased distance between base of 5th metatarsal and medial cuneiform.
- Oblique view of the foot:
- Metatarsal stress fractures.
- Calcaneonavicular coalitions.
Magnetic Resonance Imaging (MRI)
MRI of the spine (neuraxis) is indicated for unilateral cavus foot).TREATMENT
Overview
- Use joint-sparing procedures whenever possible.
- Make the hindfoot flexible.
Treatment of Pes Cavus | ||
---|---|---|
Severity of Deformity | Examination | Treatment |
Mild | Flexible, painless | Heel cord stretching, eversion/dorsiflexion strengthening program |
Mild | Progressive or symptomatic | Plantar release ± peroneus longus to brevis transfer |
Varus because of peroneal weakness | Add tibialis anterior and/or posterior tendon transfer to the peroneal muscles | |
Moderate | Rigid medial cavus | Dorsiflexion osteotomy of either first metatarsal or cuneiform |
Rigid medial and lateral cavus | Dorsiflexion osteotomies of the cuboid and cuneiforms | |
Rigid hindfoot varus | Closing/sliding calcaneal osteotomy | |
Clawing of hallux | Add EHL transfer to first metatarsal (Jones) | |
Severe | Not correctable to plantigrade with other procedures | Triple arthrodesis is rarely needed and should be avoided whenever possible. |
Nonoperative Treatment
Method:- Accomodative shoe wear is rarely sufficient except in mild deformity.
- Full-length semi-rigid insole orthotic with a depression for the first ray and a lateral wedge is indicated with mild cavus foot deformity in adult (not indicated in children).
- Supramalleolar orthosis (SMO) may be used in more severe cavovarus deformity recalcitrant to shoe wear accommodations.
- Ankle foot orthosis (AFO) may be needed if equinus also present, resulting in equinocavovarus foot deformity. It works best if equinus is a dynamic deformity (not rigid).
- Lace-up ankle brace and/or high-top shoe or boots may consider in moderate deformities when patient does not tolerate the more rigid bracing with an SMO or AFO.
Operative Treatment
Generally:- Soft tissue procedures: Indication with failure of nonoperative treatment. Includes plantar fascia release and tendon transfer.
- Percutaneous plantar fascia release is insufficient to correct a cavus foot. An open release and soft-tissue rebalancing are needed.
- Achilles tendon lengthening should not be performed concomitantly with plantar fasciotomy.
- An intact Achilles tendon provides the resistance necessary to stretch the contracted plantar tissues and correct the cavus deformity.
- Osteotomies: Calcaneal osteotomy can be used if the hindfoot is fixed in varus.
- Triple arthrodesis: Used for rigid deformity in skeletally mature patients.
Operation Methods
Soft tissue reconstruction:- Plantar release: Indicated with cavus deformity.
- Method: Plantar fascia release and Steindler stripping (release short flexors off the calcaneus).
COMPLICATIONS AND PROGNOSIS
Complications
Ankle instability: If untreated can lead to varus ankle arthritis.- Treat the cavovarus deformity concomitantly with the standard lateral ankle ligament reconstruction.
Hallux sesamoiditis: Due to overload from plantarflexed first metatarsal head.
Peroneal tendon pathology: Involves most often the peroneus brevis tendon. Includes tendonitis, tears, subluxation or dislocation.