Expert Insights On Prescribing Pediatric Orthotics
A: If a metatarsus adductus is flexible and reducible, Dr. Volpe says one can treat this with an orthosis designed around a rectus positive model. If the adductus is reduced in the positive model, he recommends incorporating a shell with a high and long medial flange — extending at least to the first metatarsal head, sometimes further to the hallux — pressed to the positive model. He says this will produce a device that holds the foot out of adductus.
With these patients, Dr. Volpe says it is important to accommodate for a potentially prominent styloid process in the negative casting and shell design/accommodations for the orthoses.
Dr. Volpe says one may take this approach regardless of age as long as the deformity is flexible and the device can reduce the deformity. He adds that issues with prominence of the styloid and consequent irritation seem to be greater with increasing age.
Like Dr. Volpe, Dr. Valmassy would use a similar device for a child under 8 that he would employ for a teenager. Dr. Valmassy says he would fully address the abnormal foot mechanics and utilize a shoe that would accommodate the orthotic, possibly utilizing some in-shoe buttressing along the medial margin of the hallux to decrease some of the pull of the abductor hallucis brevis.
In a child under 8 who demonstrates a flexible metatarsus adductus foot type, Dr. Kashanian recommends using an aggressive device to prevent breakdown and collapse of the midtarsal joint, which would result in a skewed foot. As the child becomes more ambulatory and active, Dr. Kashanian says the midtarsal joint begins to break down, unlock and pronate as a compensatory mechanism. To prevent unlocking, she advises using a combination of a medial heel skive with an inversion cast technique. When casting such a patient, Dr. Kashanian has found that casting out as much of the soft tissue supinatus out at the first metatarsal base area is helpful along with the traditional technique of holding the subtalar joint in neutral and locking the midtarsal joint.
Dr. Kashanian prefers to prescribe a vacuum-formed polypropylene device with a deep heel cup and a high medial flange. Vacuum-formed polypropylene, unlike a milled CAD-CAM device, contours better to the C-shaped lateral curvature of the metatarsus adductus foot type, according to Dr. Kashanian. She recommends a minimum cast arch fill, a medial heel skive and inverting the cast, depending on the degree of metatarsus. Dr. Kashanian says one should prescribe the rearfoot post of the orthotic with no lateral bevel. She notes this foot type has excessive lateral column loading and the unbeveled rearfoot post will offload the lateral column while allowing the medial heel skive and inversion to help the midtarsal and subtalar joint.
For teenage patients, Dr. Kashanian recommends using a deep device with a wide width and a standard arch cast fill. She says all other items of the prescription would be identical to her treatment for a younger child.
For children under 8 or 9, Dr. Jay not only creates a cast in the neutral position but holds the foot in the corrected abducted position at the same time. As he explains, this stabilizes the calcaneus in its neutral 0-degree position and abducts the forefoot on the rearfoot, reducing the metatarsus adductus deformity. The result is a negative cast of the foot in a corrected abducted position. Dr. Jay subsequently sends this to the laboratory with instructions to create an orthotic with a deep medial and lateral phalange, and a deep seated heel in a 5-degree rearfoot post.
Since children older than 8 or 9 usually have a prominent fifth metatarsal base, Dr. Jay advises cutting out the first metatarsal base area of the phalange in order to prevent any irritation or abutment into the orthotic.
Editor’s Note: The second part of this column will appear in the April 2005 issue of Podiatry Today.