The most previous post on this forum discussed orthotic control of the over-pronated forefoot, now, we are attacking the opposite condition, the over-supinated forefoot, generally seen in cavus foot types. Orthotic control of this forefoot aims to correct abnormal biomechanics, redistribute pressure off plantar prominences, and improve stability. Over-supination leads to poor shock absorption, discrete callus and blister formation, lateral foot loading, and increased risk of ankle sprains, stress fractures, and lateral (soft tissue) and medial (joint compression) knee pain.
We typically focus our attention when treating the cavus foot mechanically on the rearfoot and midfoot. An inverted heel position leads to lateral instability at heel contact, poor shock absorption and inadequate adaptability to uneven surfaces. In the midfoot we see pain in the 5th metatarsal styloid area and Peroneal Tendon pathology. Most lateral ankle sprains involving the Anterior Talo-Fibular and Calcaneo-Fibular Ligaments occur not only when the foot is inverted but also plantarflexed at the ankle. For those occasions when sudden traumatic inversion of the foot occurs with the ankle joint at neutral 90 degrees or dorsiflexed, 5th metatarsal fractures result. The goals of orthotic control of the supinated forefoot should improve alignment and stability, redistribute plantar pressure, promote shock absorption and enhance gait efficiency.
Key orthotic features for over-supinated forefoot include lateral forefoot posting (e.g., valgus wedge) which helps to evert the forefoot and encourage better ground contact.
Intrinsic valgus posting of the forefoot is built into the frame of the orthotic device, and tends to heighten the lateral arch of the orthotic device, so use caution when a patient has a prominent 5th metatarsal base or tight calves. Extrinsic valgus posting of the forefoot (valgus extrinsic bar) tends to cause a thickening of the lateral aspect of the distal edge of the orthotic frame so may cause some irritation proximal to the 5th metatarsal head. It is also a good idea to keep this correction minimal in a flexible or semi flexible device.
A handy option when correcting the supinated forefoot is the use of the Valgus Onlay Pad.
Generally made from Korex, or rubberized cork, it differs from the valgus post in so much as it is applied to the dorsal surface of the orthotic frame, as opposed to the plantar surface. It will thicken the device and elevate the 5th metatarsal, and can be useful when addressing a prominent 5th metatarsal or a tailor bunion deformity.
A Metatarsal Pad 2-4 may also be quite useful in the cavus forefoot to “balance” the metatarsal heads by filling in under the middle three metatarsals in the case of an elevated transverse metatarsal arch.
Continuing distally onto the extension of the orthotic device, several more options are available to enhance correction of the supinated forefoot. A reverse metatarsal wedge (valgus) may be added which is thicker laterally on the extension and matched to a similar degree valgus extrinsic bar.
A dancer’s pad may be added to offload a plantarflexed 1st metatarsal.
A reverse Morton’s extension will perform a similar function
A met balance pad may be added to offload prominent metatarsal heads.
A general rule of thumb to keep in mind is to use a more flexible device in a more rigid foot type, accommodating the rigid nature of the supinated foot without overcorrecting. Many of these feet also exhibit digital contractures and hammertoes thus resulting in plantar prominent metatarsals, callousing and blistering. Well cushioned top covers, thicker extensions are often called for. In the presence of non reducible hammer digits a sulcus length extension which tapers distally will allow more toe room within the shoe.
Clinical considerations should include the fact that supinated feet are often less adaptable, so orthotics should correct gently to avoid discomfort. Evaluate for associated issues like peroneal tendon stress, plantar fasciitis, or lateral ankle instability. Be mindful of potentially progressive cavus deformities resulting from neurological conditions such as Charcot-Marie-Tooth Disease and Post-Polio syndrome. Footwear should be neutral or cushioned (not motion-control) to complement the orthotic support. As always, please feel free to contact us with any questions or concerns in these challenging cases.
