However, no evidence currently supports this speculation. Anecdotally, one popular assumption holds that pes cavus deformity begins as a flexible entity and will become rigid if it is not treated. These two variations of functioning cavus feet, though similar in appearance, act very differently. 10 Although this type of pes cavus classification is often the least emphasized, function may prove to be the most important consideration relative to orthotic therapy. The short and long plantar ligaments may also develop contractures due to decreasing motion across their respective joints, maintaining a more rigid cavus foot. 9 This effect tends to maintain greater rigidity in some individuals and less in others, depending on the flexibility of the patient’s midtarsal joint. The myofascial band of the plantar aponeurosis maintains the deformity with the windlass effect. With regard to function, the pes cavus foot has also been classified as either flexible or rigid. The global type, sometimes referred to as combined cavus, is a combination of both deformities. The posterior type has a high calcaneal inclination angle but no forefoot equinus. 3 The anterior cavus is either total (indicating plantar flexion of the entire forefoot) or local (plantar flexion of the first ray only). The structure of pes cavus falls into anterior, posterior, and global categories. A normal foot has a score between 0 and +5. This statistically validated and consistent tool defines the cavus foot as any foot that has an FPI score between -5 and -12 on a scale from -12 to +12. 2,6-8 The FPI is the most comprehensive of these methods because it distinguishes all foot types, not just the cavus foot, using point-based criteria. The high-arched foot has also been classified according to footprint morphology, radiography, visual inspection, and, most recently, the Foot Posture Index (FPI). 4 Despite this discrepancy between the two studies, each study found that a significant portion of the pes cavus patients had no known etiologic source of deformity. 5 Another study reviewed 77 patients in a pes cavus clinic and found that 33.8% of cases were idiopathic and 66.2% were neuromuscular. 4 A large retrospective survey reviewed 465 patients with pes cavus and found that 81% were classified as having idiopathic pes cavus and 19% had neuromuscular pes cavus. Researchers often differentiate idiopathic from congenital pes cavus. The most common classification system categorizes pes cavus as neuromuscular, congenital, or traumatic. However, many of these overlap, which can lead to confusion. Pes cavus has a variety of classifications. 3 By combining what is known with what we can hypothesize, perhaps we can establish a new and more successful approach to pes cavus. Traditionally, we have considered pes cavus a neuromuscular problem with a surgical answer. 2Īlthough medical knowledge regarding pes cavus exists, the research and treatment options, as well as any theories or hypotheses as to why humans develop this deformity, are quite limited. 1 Sixty percent of individuals with cavus feet develop foot pain. Pes cavus foot occurs in about 8% to 15% of the population, but it does not get nearly as much attention in the medical literature as does its counterpart, pes planus. This author proposes a theory of pes cavus etiology based on muscle imbalances and reactions, which may support the concept of early orthotic intervention. Published studies on pes cavus are in short supply, making evidence-based orthotic management a challenge.
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