Pes cavus is commonly characterized by its elevated longitudinal medial plantar arch of the foot and is also known as “claw foot, hollow foot, or cavovarus foot” [1,5]. Variations of pes cavus deformities exist and may be associated with acquired, hereditary, and congenital neurological or musculoskeletal conditions. Pes cavus may have concomitant hindfoot varus, equinus, forefoot adduction, forefoot valgus, and claw toe [deformities] . Patients often present with painful conditions which result from pes cavus (e.g. peroneal tendinitis) rather than deformity itself. The presentations may merely be a result of abnormal biomechanics associated with cavus feet and identification and management of cavus feet is essential for successful treatment and avoidance of recurrence of symptoms.
Pes cavus cases can resultfrom hereditary or acquired peripheral neuropathies. Regardless of the etiology of the neuropathy, intrinsic muscle atrophy and imbalance among different muscles group of the leg leads to features of pes cavus including high arch, clawing of the toes, and equinus deformity.
Common causes of pes cavus [1,3,6]:
- Hereditary neuropathy [e.g. Hereditary sensory motor neuropathy (Charcot Marie Tooth disease)
- Spinal cord defects (e.g. congenital, traumatic)
- Acquired neuropathy (e.g. diabetic peripheral neuropathy)
- Posterior compartment syndrome of the leg
- Malunion of calcaneal or subtalar fracture
- Idiopathic subtle cavus feet without neurological disorders
- Lisfranc fractures
Epidemiology and Risk factors for Prevention
Pes cavus occurs in about 8-15% of the general population [9,10,12]. Severe pes cavus is 30% idiopathic in nature with 70% likely secondary to neurological causes, with most having origins with Charcot Marie Tooth disease (hereditary sensory motor neuropathy) [1,11].
Patho-anatomy and Physiology
Cavus deformity of Charcot Marie Tooth disease is hypothesized to stem from asymmetric foot weakness anterior-laterally due to selective denervation of the tibialis anterior and peroneus brevis muscles of the legs . The relatively weak tibialis anterior is overpowered by the strong peroneus longus muscle which plantarflexes the first 1st ray and pronates the forefoot (making forefoot valgus). This forefoot valgus position further drives the hindfoot into inversion. The extensor hallucis muscle which dorsiflexes the toe would then be unable to balance the combined plantarflexing forces of peroneus longus, posterior tibialis, and triceps surae muscles. Imbalance between relatively weak peroneus brevis and preserved posterior tibialis muscle leads to inversion of calcaneus and adduction of foot. Clawing of foot occurs as result of interphalangeal joints flexed by the flexor digitorum longus while the metatarsal phalangeal joints are extended by the extensor digitorum longus . A high foot arch then forms as the peripheral nerves are denervated more proximally in the foot causing fibrotic muscles to retract. In the early stages, the foot is flexible, but becomes more contracted as the disease progresses due to chronic muscular imbalances. In cavus foot associated with neuropathy, the heavy callus and the plantar ulceration are common on the 1st and 5th metatarsal heads due to high plantar pressure and reduced sensation in these areas. This can lead to infection and sometimes amputation [1,8,11,15].
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
Subtle cavus feet can be noted in normal individuals without neurological disorders. They may develop pain associated with various musculoskeletal conditions on the lateral foot (e.g. peroneal tendinitis, lateral ankle sprain). These individuals do not have neurological disorders with normal neurological examination (Figure 1a & 1b).
Figure 1a, 1b, and 1c.
Subtle cavus feet showing high arch, “peek a boo heel sign” when observed from the front (medial heel is shown bilaterally, 1b). Forefoot valgus with 1st ray lower than the rest of the forefoot (1c)
Pes cavus varies a great deal in severity of deformity, pain, and other musculoskeletal symptoms. Subtle cavus feet in otherwise normal individuals may not trigger pain or functional impairment other than excessive wear of the footwear laterally or callus formation on the lateral foot (5th metatarsal heads and base, lateral heel). As they engage in physical activities or sports, these individuals may become symptomatic.
Specific secondary or associated conditions and complications
The following are the common conditions associated with pes cavus [1,2].
- Pain and calluses on the lateral foot (5th metatarsal head and base, lateral heel)
- Stress fractures on 5th metatarsal, medial malleolus
- Stress fracture of sesamoid under the 1st metatarsal head
- Midfoot arthritis and associated anterior tarsal tunnel syndrome (deep peroneal nerve irritation)
- Peroneal tendinitis/tendinosis
- Heel pain including plantar fasciitis (hypothesized to be from poor shock absorption)
- Lateral ankle sprain
- Achilles tendinosis/Insertional Achilles tendinitis/adventitious bursitis
- Lateral and anterior knee pain (hypothesized to be from knee hyperextension, varus of the knee from supinated foot) from iliotibial band syndrome.
2. ESSENTIALS OF ASSESSMENT
Clues in History for Pes Cavus:
Patients often present with painful conditions mentioned above rather than the deformity itself. Any patient with metatarsalgia, frequent lateral ankle sprain, midfoot pain, stress fractures of 5th metatarsal, Achilles area pain, or heel pain should be examined for possible pes cavus. Patient’s report of excessive wearing of footwear on the lateral side also warrant thorough examination for pes cavus. The presentation of these conditions may merely be a result of abnormal biomechanics associated with cavus foot and identification and management is essential for successful treatment and avoid recurrence.
- Elevated medial arch
- Hindfoot varus (inverted calcaneus)
- Reduced passive range of motion of ankle dorsiflexion [Shortened gastrocnemius and Achilles tendon (may not be observed in calcaeocavus, e.g. pes cavus due to weakness of gastrocnemius in polio patients)]
- Reduced subtalar pronation (relatively more range of motion of supination)
- Peek-a-boo heel sign in standing (medial heels are seen from the front (Figure 1b))
- Foot calluses usually under 1st and 5th metatarsals with/without tenderness
- Forefoot valgus (1st ray lower than the rest of the forefoot) which drives hindfoot into varus
- Muscle hypotrophy of Peroneus Brevis and Tibialis Anterior
- Coleman Block Test: evaluation for examining the flexibility (reducibility) of hindfoot varus. Place a block under the lateral side of the forefoot and examine whether hindfoot returns to neutral position from varus. If hindfoot remains to be in varus position, the hindfoot deformity is likely rigid and not correctable with orthosis.
- Full neurological examination: If neurological impairment is noted in clinical examination, further work-up including electrodiagnostic study is warranted [1,3,13,14].
Clinical functional assessment: mobility, self care cognition/behavior/affective state
- Gait evaluation is essential especially in cavus feet of neurological etiology. Clinicians look for
- Steppage gait or foot drop (weak dorsiflexor tibialis anterior)
- Toe hyperextension (compensate with extensors for weak dorsiflexor tibialis anterior) in swing phase
- Footwear evaluation
- lateral wear of outsole
- deformation of upper lateral aspect of shoe
- excessive wear and pressure points on 1st and 5th metatarsal heads
If hereditary neuropathy is suspected, electrodiagnostic study, nerve biopsy, and genetic testing is recommended.
Radiographs of foot (at least 3 views) are obtained for evaluation of pes cavus deformities including lateral ankle/foot, frontal view of hindfoot (Meary or Salzman), dorsoplantar of forefoot . All imaging of foot is taken in weight bearing position.
- Forefoot Cavus – Hibb’s Angle also known as Calcaneum to First Metatarsal angle >45 degrees
- Meary’s Angle – Talus to Frist Metatarsal angle >5 degrees
- Hindfoot Cavus – Calcaneus to ground angle > 30 degrees
- Tibio-talar angle > 105 degrees
CT and MRI scans are not used often as they are more useful for peroneal tendinopathy for future reconstruction of ligament, weakness in amyotrophic lower extremities from Charcot Marie Tooth disease, spinal cord involvement, and painful arthritis of the foot [3,7,11].
Supplemental assessment tools
Electrodiagnostic Study (Edx):
Edx may reveal peripheral neuropathy or nerve root lesions. Other work ups include genetic testing and imaging of spine depending on the clinical and Edx findings.
Early predictions of outcomes
Neurogenic cavus feet are often more severe and progressive.
Increased activities and laterally worn out shoes results in secondary conditions.
A hard floor surface and rigid footwear exacerbate symptoms.
Soft flexible footwear accommodates the rigidity of cavus feet.
Elevated heel design is also recommended for accommodation of shortening of gastrocnemius.
Social role and social support system
Neurogenic cavus feet often have genetic predisposition and screening of family members may be needed. Understanding the progressive nature of neurogenic cavus feet and potential disability will help to plan for the future.
Neurogenic cavus feet also often accompanies foot drop. Fall prevention and intervention education is important.
3. REHABILITATION MANAGEMENT AND TREATMENTS
Available or current treatment guidelines
Currently no specific published guideline is available for pes cavus.
At different disease stages
Treatment differs depending on the etiologies and severity of pes cavus.
Treat for the associated conditions with NSAIDs, tape, and bandages.
Identify the biomechanical deficit and address them with orthosis.
Stretching of gastrocnemius and subtalar range of motion to increase pronation range of subtalar and ankle dorsiflexion range.
Check the status of orthosis and revise it as needed. Inspect footwear for lateral wear.
Accommodative footwear and operative interventions for recalcitrant lateral ankle instability and plantar ulceration under metatarsal heads.
For individuals with idiopathic subtle cavus feet without neurological conditions, addressing the presenting symptoms and conditions is the first step of treatment. These individuals may have lateral ankle sprain, peroneal tendinitis, and other disorders mentioned above which may be triggered or exacerbated by pes cavus deformity. Choosing proper footwear especially athletic footwear (sneakers) during sports activities is essential. Clinicians should examine their foot wear for work and leisure activities to ensure that their feet are properly supported. They should avoid sneakers with anti-pronation design (reinforced medial midsole, counter) which is popular and commonly used among runners. This type of sneaker is designed for individuals with pes planus and potentially drives the foot into further supination putting further stress on the lateral structures of the feet. Foot orthoses should be designed to address all components of the deformities (hindfoot varus, ankle or forefoot equinus, forefoot valgus) taking into account the flexibility of the deformities. If hindfoot varus is flexible, a lateral wedge combined with a heel lift is incorporated in the orthotic prescription. Forefoot valgus is an often ignored component of pes cavus. A small lateral forefoot wedge or depression on the insole at the location corresponding to the 1st metatarsal head can accommodate forefoot valgus. This design reduces the need for the hindfoot turning to varus. Individuals with severe deformities of idiopathic pes cavus with lateral ankle/foot instability with recurrent ankle sprain should be referred for possible operative intervention. Physical therapy focuses on stretching of gastrocnemius and restoring subtalar eversion.
Pes cavus from neurological disorders is often worsened as the primary disorder progresses. Patients with Charcot Marie Tooth disease presents with foot drop, heavy callus formation on the 1st and 5th metatarsal heads, and clawing of the toes. These individuals often require AFO (typically posterior leaf spring orthosis) unilaterally or bilaterally. Foot orthoses can be placed inside an AFO with the design mentioned above to address forefoot valgus and reduce pressure on the 1st metatarsal head. As the disease progresses, patients may have further weakness in ankle plantarflexion and knee extension, a semisolid or solid AFO may be needed. Solid AFOs for both lower limbs are rarely recommended because they do not allow any motion of the ankle, subtalar, and midtarsal joints.
Physical therapy emphasizes prevention of contractures (i.e, gastrocnemius), range of motion exercises, and gait training with AFO [1,3,8,12,16]. Custom made orthotics reduce about 75% of the pain and redistributes pressure points around the foot . Operative intervention should be entertained in patients with recurrent plantar ulceration, lateral ankle and foot instability which affects mobility and quality of life.
These may involve plantar fasciotomies, Achilles tendon lengthening, tendon repairs, soft tissue releases, and osteotomies [1,3]. Patient may still need to wear AFO after the operation.
Coordination of care
Parallel practice: Patients may be rehabilitating but still working or competing.
Coordinated: Employers, coaches, and family may need to be involved to promote a successful outcome.
Multidisciplinary: Athletic trainers, physical therapists, and orthotists may be involved.
Interdisciplinary: Foot-ankle trained orthopedic surgeons or podiatrists can be consulted in refractory cases.
Patient & family education
Educate on the importance of foot and ankle stretching, appropriate training volume and intensity, appropriate shoe (and orthotic) wear. Different athletic shoes should be worn every 6 months and can be rotated for longer wear.
Measurement of Treatment Outcomes including those that are impairment-based, activity participation-based and environmentally-based
The Foot Function Index (FFI) is a 0-10 scale of pain and foot function over time in standing, walking, etc. The Foot Health Status Questionnaire (FHSQ) is a 42-item questionnaire assessing quality of foot health. The Foot and Ankle Ability Measure (FAAM) is an activities-of-daily-living scale of foot health. These measures can be used to assess pain severity and to monitor response to treatment.
Translation into Practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
Neurogenic cavus feet may progressively worsen with new weakness in ankle dorsiflexors or quadriceps. Thorough manual muscle testing at each visit should be performed including proximal muscles. A systematic approach should be used.
4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
Key point in orthoses
New treatment techniques include extracorporeal shockwave therapy (ESWT), ultrasound guided corticosteroid injection, percutaneous needle tenotomy, platelet rich plasma (PRP), prolotherapy, and potentially in the future, stem cell therapies to promote healing.
Newer materials for orthotics and knowledge of different shoes for different activities are important. Minimally invasive surgical techniques are emerging.
5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE
Controversies and gaps in the evidence-based knowledge
New techniques of pain management include different types of foot orthotics and ankle bracing. The role of PRP, prolotherapy, botulinum toxin, percutaneous needle tenotomy, stem cells needs to be evaluated. Comparison-outcome trials are needed to provide better data to evaluatetreatment options. The current controversy in the reconstruction of these deformities is whether to proceed with osteotomies and tendon transfers or arthrodesis.
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Original Version of the Topic
David Berbrayer, MD. Pes Planus/Cavus. 09/15/2015.
Mooyeon Oh-Park, MD
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Yusik Cho, MD
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Lawrence Chang, DO, MPH
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