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What is Pes Cavovarus?

pes cavovarus arched foot charcot marie tooth

Pes Cavovarus (or an overarched foot) is a condition that can be thought of as the opposite of flatfoot, where the arch of the foot is dramatically high, and the foot is tilted inward (supinated).  

This foot deformity can cause problems with coordination, walking, and pain, however, the reason doctors are most concerned about the condition when it comes into the office is the high association with neurologic conditions that involve the whole body.  An abnormal nerve causes the muscles to act abnormally, and this leads an abnormal foot alignment.

The large arch deformity is caused by the first toe (great toe) being flex-downward (planterflex) because of a muscle imbalance (usually abnormal nerve activity causes abnormal muscle tension).  When you think about the motion in all of your joints, they are able bend and straighten by the balance of opposing muscles.  But what if some of the muscles are very strong and the other is weak... then the joint would stay bent in one position (its like a game of tug-o-war).  That is essentially what happens with this deformity, where the Peroneus Longus and Tibialis Posterior muscles are too strong for the opposing muscles, the Tibalis Anterior muscle and the Peroneus Brevis muscle, so it deforms the foot over time by pulling the foot into a big arch.  

what is a high arch foot in a child too big of an arch suggest cavus foot
cavovarus foot is caused by the overpull of the tibialis posterior and the peroneus longus

How is Pes Cavovarus diagnosed?

Like flatfoot, some people just have high arches (the upper limit of whats considered normal), while others have truly abnormal high arches, which get this fancy name “Pes cavovarus”.  

Separating a normal from abnormal high arch is a major challenge of diagnosis, and ultimately theres no perfect test, and it’s the years of experience doctors have that allow them to really tell the difference between the two. 

About 2/3 of kids that have true cavovarus have an underlying neurologic cause such as a spinal cord anomalies, or the condition called Charot Marie Tooth.  Therefore, when someone is diagnosed with this condition, doctors must back up, take their mind off the foot, and look at whole child.  They need to work with a neurologist and geneticist to evaluate other abnormalities in the body before sitting down to talk about the foot.  

Only after doctors have looked at the whole body, can they then focus in on the Cavovarus foot.  

There are stages of progressive foot deformity, and by looking at the foot, a doctor can determine how far along in the course a patient is.  

The first change is the large arch and over time the toes try to compensate for the downward slope of the forefoot (the arch causes the toes to be pointed downward) so the toe extensor muscles pull upward and create “claw toes” which places a lot of pressure on the front of the feet causing calluses to form under the base of the toes.  Additionally the muscle imbalance also not only forms the large arch, but pulls the foot to start facing inward (supinate), thus increasing pressure over the outside (lateral) part of the foot (causing a thick callus to form), and over time this internal rotation becomes rigid and non-flexable.  All the changes create this “tripod” effect on the foot, where all the weight gets placed over the 1st and 5th Metatarsal head (front of the foot) and the lateral part of the back foot (secondary to varus).  Doctors get x-rays and see this angle and relationship between the foot bones.  This will guide treatment

pes cavus pes cavovarus pressure callus formation first and fifth metatarsal heads and lateral foot

Doctors also perform the "Coleman Block Test" which helps determine the severity of the Cavo Varus.  While the abnormal balance of muscles technically occurs in the front of the foot creating the High Arch...over time the back of the foot (aka the heel bone) is pulled into Varus.  The Coleman Block test puts a bump under the front of the foot to correct the high arch (cavus), and then looks at the back of the foot to see if the "varus" component gets better.  This test is evaluating the flexability of the hindfoot, which is important if surgery is required (see below).  

what is the coleman block test

How do you treat Pes Cavovarus:

surgical treatment for pes cavovarus tibialis posterior transfer first metatarsal osteotomy calcaneus valgus ostoetomy

Mild cases can benefit from custom insoles (orthotics) to go into sneakers and take pressure off the outside of the foot and prevent callus formation.  

More severe causes require surgery to correct the High arch (aka Cavus) and possibly correct the Varus too (this depends on the flexability of the hindfoot...which is determined by the Coleman block test).  Surgery involves switching around the teams.  The Tibialis Posterior (which was too strong before) is now pulling the other direction.  The tight Plantar fascia and Achilles Tendon are also loosened.  Sometimes the foot bone for the big toe is also straightened out.  

If the Varus is not flexible, the correcting the front of the foot will not allow the hindfoot to similarly correct.  Instead the heel bone is straightened out with surgery.