Practice Essentials
Pes cavus is a descriptive term for a foot morphology characterized by high arch of the foot that does not flatten with weightbearing. [1] No specific radiographic definition of pes cavus exists. [2] The deformity can be located in the forefoot, the midfoot, the hindfoot, or a combination of these sites. [3] Whereas pes cavus is a common finding, occurring in approximately 10% of the general population, [4] it can also be a sign of an underlying neurologic disorder. [5]
The spectrum of associated deformities observed with pes cavus includes clawing of the toes, posterior hindfoot deformity (described as an increased calcaneal angle), contracture of the plantar fascia, and cockup deformity of the great toe. This can cause increased weightbearing for the metatarsal heads and associated metatarsalgia and calluses.
The goal of treatment is to produce a plantigrade foot that allows even distribution of weight. Failure to maintain an asymptomatic plantigrade foot is an indication for surgery. Nonoperative treatment (eg, physical therapy, orthotics, or bracing) may provide significant relief. Surgical decision-making requires a careful and complete examination of the foot and ankle, especially for rigidity, strength, and deformities. Surgical procedures can be broadly categorized into soft-tissue and bony procedures. No single procedure is appropriate for all patients; frequently, multiple individual procedures must be performed.
Pathophysiology
Multiple theories have been proposed for the pathogenesis of pes cavus. Duchenne described intrinsic muscle imbalances causing an elevated arch. Other theories include the extrinsic muscle and a combination of the intrinsic and extrinsic muscles being causes of the imbalance.
Mann described the pathogenesis of pes cavus in patients with Charcot-Marie-Tooth (CMT) disease. [6] An understanding of the muscles involved and the sequence of the involvement helps in understanding the deformity. An agonist-antagonist model for the muscles determines the deformity. In CMT disease, the anterior tibialis and the peroneus brevis develop weaknesses. Antagonist muscles, the posterior tibialis and the peroneus longus, pull harder than the other muscles, causing deformity.
Specifically, the peroneus longus pulls harder than the weak anterior tibialis, causing plantarflexion of the first ray and forefoot valgus. [7, 8] The posterior tibialis pulls harder than the weak peroneus brevis, causing forefoot adduction. Intrinsic muscle develops contractures while the long extensor to the toes, recruited to assist in ankle dorsiflexion, causes cockup or claw toe deformity. With the forefoot valgus and the hindfoot varus, increased stress is placed on the lateral ankle ligaments and instability can occur.
In patients with polio, the deformity is in the hindfoot and is caused by weakness of the gastrocnemius-soleus complex. This leads to a marked increase in the calcaneal pitch angle with normal forefoot alignment.
Etiology
Possible causes of pes cavus include the following:
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Malunion of calcaneal or talar fractures
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Burns
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Sequelae resulting from compartment syndrome
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Residual clubfoot
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Neuromuscular disease
The remaining 20% of cases are idiopathic and nonprogressive. Identifying the etiology is essential to determine if the deformity is progressive, which assists in operative planning.
Neuromuscular diseases, such as muscular dystrophy, CMT disease, [9, 10, 11, 12, 13, 14] spinal dysraphism, polyneuritis, intraspinal tumors, poliomyelitis, syringomyelia, Friedreich ataxia, cerebral palsy, and spinal cord tumors, can cause muscle imbalances that lead to elevated arches. [15] A patient with a new-onset unilateral deformity but without a history of trauma must be evaluated for spinal tumors.
Pes cavus may occur as part of the CAPOS (Cerebellar ataxia, Areflexia, Pes cavus, Optic atrophy, Sensorineural hearing loss) syndrome, caused by a mutation in ATP1A3. [16]
Prognosis
The results of surgical intervention are difficult to compare because of the multiple possible combinations of procedures necessary for successful treatment. Moreover, patients have varying degrees of deformity, disease progression, and underlying etiology, making comparison virtually impossible.
Nevertheless, some positive findings have been reported, such as Wetmore and Drennan's report that 24% of patients with CMT disease who underwent a triple arthrodesis had satisfactory results at an average of 21 years of follow-up. [17] They recommended the triple arthrodesis as a salvage procedure.
Mann and Hsu reported on 12 feet in patients with CMT disease that underwent triple arthrodesis, with a follow-up that averaged 7.5 years. [6] Five feet were plantigrade, asymptomatic, and united; three feet were plantigrade and asymptomatic but had nonunions; and four feet were nonplantigrade and symptomatic. The authors stated that positioning is the key to satisfactory results.
Roper and Tibrewal reported the results of soft-tissue procedures combined with osteotomies. [18] Ten cases of CMT disease were reviewed 14 years after surgery. Two patients required repeat surgery secondary to recurrent deformity. At last follow-up, all patients had plantigrade feet, without requiring a triple arthrodesis.
Gould discussed 18 feet in 10 patients with a 3- to 6-year follow-up. [19] All had satisfactory results with soft-tissue procedures combined with osteotomies, and all patients had plantigrade feet at last follow-up.
Sugathan et al treated lesser-toe clawing in 11 feet (N = 8) with flexible pes cavus using a modified Jones procedure. [20] At final clinical review, all 11 feet were improved, with minor complications in six. The mean Bristol Foot Score was 27, and the mean modified American Orthopaedic Foot and Ankle Society (AOFAS) Midfoot Score was 76, which indicated excellent results. Half of the patients had mild persistent foot pain, but all were satisfied with the outcome.
Naudi et al reported radiologic and clinical results with anterior tarsectomy in 39 cases of pes cavus (N = 33). [21] Pain decreased considerably in 75% of cases, and 68% of patients recovered normal activity. The foot was aligned correctly in 67% of cases, but at last follow-up, pes cavus remained undercorrected in 80%. In 74% of feet, adjacent joints showed progressive osteoarthritic degeneration. Subjectively, 70% of patients were very satisfied or satisfied with minor reservations, and objective outcome was excellent or good in 66% of feet.
According to Naudi et al, the overall results of this study showed that outcome in terms of function, motion, complications and satisfaction was good, but pain relief results were poor. [21] They added that anterior tarsectomy is able to correct initial pes cavus deformity and compensate anomalies of the hindfoot, but its correction capacity is limited, and its efficacy in case of clawfoot is poor.
Limitations to the literature exist. Most of the reported results include reviews of adolescents rather than adults. Multiple variables are included with a small population of patients. Current trends, however, are toward soft-tissue procedures combined with osteotomies, with arthrodesis reserved for salvage procedures.
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Pes cavus with severe hindfoot involvement.
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Pes cavus with plantarflexion of first ray.
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Patient with cavovarus deformity in both feet. Heel varus can be appreciated as it can be viewed from front, making "peek-a-boo sign" positive.
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Same patient viewed from back, showing varus deformity of heels, which is worse on right side.
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Same patient with Coleman block test showing correction of heel varus to neutral on left side but not on right side.
