A few posts ago I discussed (really just reviewed) the Inverted Forefoot Deformities, and today I will do the same with Everted Forefoot Deformities. Typically seen with the patient in a prone position, or captured in your cast or image. I like to lay the patient on their stomachs, get the posterior surface of the heel parallel with my eyes, and hold the subtalar joint neutral at the fifth metatarsal base. Then I have an easy observation of the position of the metatarsal heads to that heel bisection line. Are they inverted, perpendicular, or everted to the heel bisection or the plantar surface of the heel? Are you going to say this patient has an inverted deformity or an everted deformity?
For our discussion, let us say you observed and/or measured, an everted forefoot deformity. Here the first metatarsal head is lower than the 5th metatarsal head. Its compensation at forefoot loading is to invert the heel to rest the whole forefoot on the ground. This of course is opposite of what a forefoot varus needs to do to bring the entire foot to the ground which would be heel eversion. Forefoot varus/supinatus is an easy compensation working with gravity. Forefoot valgus/pronatus compensation of heel inversion does happen but with less frequency. Since the foot has already begun to pronate at heel contact, reversing course into inversion or a supination course is tissue demanding. I estimate a pes cavus with plantar flexed first ray (everted forefoot deformity) inverts 1/3 of the time, stays rigid with a vertical heel 1/3 of the time, and actually everts the heel 1/3 of the time. Only the heel inversion would be considered compensation of this everted forefoot deformity. Since we know that these everted forefoot deformities do function with all the metatarsal heads on the ground, the forefoot must accomplish this with other mechanisms than heel inversion. An easy example is a weak posterior tibial tendon which allow the medial column to dorsiflex leveling the met heads, or a tibial varum that pronates the subtalar joint for its own compensation, and allows medial column dorsiflexion to the ground.
Are these the ramblings of a madman? Possibly, I just want you to think about these deformities more (when they have become somewhat boring at times). I want to breathe some life into them. So, what are the 3 most common everted forefoot deformities seen? Plantarflexed first ray, often called a rigid deformity, since it can demand heel inversion and subsequent foot rigidity. Forefoot valgus is a fairly even everted forefoot deformity from the first to the fifth metatarsal heads. Forefoot pronatus is the functional everted forefoot deformity which can reduce with custom orthotic devices. Forefoot pronatus can develop with any overload of the lateral column which may twist the joints and soft tissue into more forefoot eversion on the rearfoot. Common examples are forefoot pronatus secondary to genu varum and its overload of the foot's lateral column, or forefoot pronatus secondary to plantar flexed first ray and its heel inversion which overloads the lateral column. In this case, you may measure 8, 9, 10 degrees of an everted forefoot deformity this year, only to see your next cast or image at 5 or 6 degrees (with complete reduction of the pronatus deformity).
While I have had fun with this, and perhaps too much, what is the take home? Get good at measuring the forefoot to rearfoot relationship when making orthotic devices. If you correct the heel's eversion or inversion, within a year you may see a reduction of some of that inverted or everted angle due to the the reduction in soft tissue contractures holding that deformity.
