Technical Note: Growth Extensions and Adjustments in Childrens Polypropylene Ankle-Foot Orthoses
Peter J. DiMeglio, C.P.O.
Mark Taylor, C.O.
Charles Thomas, assistant
Jim Merchand, assistant
For the past five to seven years the use of polypropylene in orthotics has grown enormously in our community. Parents, patients, and medical staffs have, in the main, accepted the change to plastics for their orthotic needs. Less weight and improved cosmesis have been the two most positive factors for acceptance.
The one negative factor with this newer type of orthosis has been lack of adjustability for growth. Many orthoses have been discarded prematurely because adjustments for growth are not possible while adequate, comfortable support is maintained.
We have dealt with this factor for quite some time, and have developed a few procedures that may help alleviate some of these problems.
The ability to continue use of the original orthosis necessarily depends on the growth rate of each patient, and even with the conventional orthosis, periodic evaluation is necessary to determine the advisability of a replacement.
Growth problems occur first at the anterior area of the sole. When the trimline is posterior to the metatarsal heads by a considerable amount, the orthosis tends to dig into the tissue during heel contact, causing an uncomfortable ridge to form behind the metatarsal area; later, the development of the calcaneal area prevents a proper fit because the patient's foot will not seat properly into the heel of the orthosis. When this situation occurs with an orthosis that has been designed to provide medial-lateral ankle stability, the forces become inadequate, and the patient complains of pressure posterior to the malleolus area; the proximal edge of the orthosis then drops below the fibular head and digs into the muscle belly of the gastrocnemius, causing a ridging and digging in the calf area.
To prevent or delay these problems we have altered our fabrication techniques. When fitting an ankle-foot orthosis on a small child where the probability is great that he or she will be a long term user the orthosis, it is lined throughout with Plastizote or a similar material which may be removed and replaced with a thinner liner as the patient grows, which, in turn, is eventually removed and the patient wears the orthosis with no liner.
This procedure allows for the growth and development of the foot without flaring the sides of the orthosis and sacrificing some stability of the ankle. The modifications need to be exact and buildups are kept to a minimum in order to reduce excessive bulkiness, especially for smaller children.
We have prevented the pressure behind the metatarsal heads by attaching a plastic extension that comes up under the metatarsal heads where normal trim lines would be. These extensions can be attached either in the forefoot area of the orthosis or may run the entire length of the orthosis sole, back to the heel.
To solve the linear growth problems, two designs have been used. Our aim is to keep the proximal area of the orthosis distal to the fibular head to provide comfortable and adequate support by applying extension bars to the lateral sides of the orthosis. Also a single posterior extension bar can be used for the same purpose (Fig. 1 and Fig. 2 ). Another design is used by overlapping the plastic in the calf area during fabrication allowing extension proximally in this area, according to patient growth.
This paper is designed only to familiarize the orthotist with some of our efforts to solve the complex growth problems presented to us by these young patients. We know that there are many ways to solve these problems and hope that fellow practitioners will share their experiences and ideas with those of us who are in the field of orthotics.