A Case for Supra-malleolar AFOs in Persons with Cerebral Palsy

Nancy Hylton

Typical foot/ankle bracing for individuals with cerebral palsy often includes a fixed 90 degree PF stop combined with either a solid custom molded or hinged AFO when the person has significant PF hypertonus and/or spasticity even though recent biomechanical, soft tissue and movement science supports a more dynamic approach. During a course in Seattle on " Evaluation and Intervention for Musculoskeletal Injuries: Biomechanical Approach ", instructor Michael Gross, PhD, PT, Program in Human Movement Sciences, Div. PT, U of N.C. at Chapel Hill was asked the question "If you had 2 choices of bracing, one that blocked movement even in one direction and one that acted like a guiding exoskeleton, assisting physiologic movement control in all directions which one you would chose?" His answer to me was, " Research in biomechanics clearly points to the 2nd option. Immobilization, no matter how well intended, makes the musculo-skeletal system weak. " I took this comment as a scientific validation of our clinic bracing experience over the past 25 years. This is the period of time that we have be using nearly exclusively ultra-flexible supra-malleolar style Dynamic AFOs at CTC of Kent in Washington State.

Our journey with this style of bracing began much earlier in the early 1970's, as an adjunct to NDT based therapy, with shoe modifications, short leg casting and ultimately ankle height casting to reduce disruptive hypertonus at the ankle and throughout the body. We were focusing treatment on young children with cerebral palsy to begin with. There were many surprises along the way. In many children with moderate to severe spasticity, reducing plantarflexion spasticity caused global changes including uncovering underlying instability, hypotonia and muscle weakness. Some had no idea how to move when their motor strategies were dramatically altered by the new environment. But we also often saw the ability to move more easily and in more adaptive ways when we changed their base of support (BOS) in this way.

BOS science tells us that our balance is typically organized from our base of support and muscles activate in a distal to proximal wave beginning at the base of support. Most of us use a combination of ankle, hip and trunk strategies to smoothly manage our posture, balance and movement control. In person's who have CP or other neuromotor impairments, balance is one of the sensory-motor mechanisms that is disturbed. Research by Marjorie Woolcott and others in Portland, Oregon has shown that even very active and able children with CP are all weaker and have immature balance responses as compared with their typical peers. Instead of the distal to proximal wave of activation, their balance strategies tend to initiate more proximally, ie., at the knees or hips, and create a mass activation response throughout the body. Leading edge research has been published by physical therapists, such as, Ann Schumway-Cook and Marjorie Wolcott in the Pacific NW, helping us to understand how our balance system works.

Our consistent use of custom contoured footboards to achieve precise support of the active dynamic arching structures of the foot during cast molding, permits a much more exact mold which makes mold rectification Soft tissue science, primarily funded by sports medicine concerns, has looked closely over the past 20 + years at the nature and impact of different environmental elements on the health and strength of soft tissue structures, such as, muscles, tendons and ligaments. The negative impact of immobilization on these tissues has totally changed the sports medicine approach to healing of soft tissue injuries during this time. When immobilization is contrasted with guided physiologic triplanar movement, immobilization produces a 50% decrease in the strength of soft tissue structures within 2 weeks, muscle atrophy, deactivation of biomechanical chain movement interactions, and decreases in proprioception and other somato-sensory input needed for movement control and balance. By contrast, triplanar physiologic movement maintains soft tissue strength, increases muscle strength and endurance, supports biomechanical chain micro-interactions for balance and movement control, and supports proprioception and other somatio-sensory input necessary for movement control, active stabilization and balance.

Research over the past 20-30 years has also shown that biomechanical alignment and stabilization is a "dynamic process" organized around dynamic spiral linkages and microchanges of motion. The biomechanical system interacts intimately with our neuro-postural control mechanisms and relies heavily on body awareness provided by somato-sensory receptors. These are basically mechano-receptors and rely on small and controlled increments in positional change to function. Even important hard-wired neurologic structures, such as the central pattern generator (CPG) which supports typical walking and makes it efficient and easy, are dependent on typical biomechanical and sensori-neural function to operate.

Research in neuro-physiology indicates that our sensory-motor system is very plastic and adaptive, via reinforcement and changes in synaptic connections in our CNS. Neurotrophic chemicals that are produced with every movement, feed the growth and development of synaptic connections whether movement is driven by stereotypic spastic movement strategies or typical more adaptive balance and movement strategies. Research shows that forcing the use of an affected limb, after CNS injury, will cause nearby undamaged areas of the brain to take over motor control function. Whether atypical or typical movement control is practiced, the practiced movement, including those based on spasticity, will get stronger.

Considering this ever growing body of new information, what might be the advantages of precision fabricated very flexible 2 mm polypropylene supramalleolar AFOs in person's who have cerebral palsy and other neuro-motor conditions? l)They provide precise deep pressure, precise touch and proprioceptive information for a person to better control balance from their BOS. 2)They control and contain alignment and movement, but permit small increments of guided triplanar movement to occur, supporting more typical whole body movement control. 3)They support a predictable balance and motor response. 4)They can guide active awareness of midline orientation and motor learning by the rebound qualities of the ultra-thin fabrication materials. Though it is a very old plastic, polypropylene has exceptional rebound memory, which supports motor learning and somato-sensory awareness. 5)And finally, supra-malleolar DAFOs support soft tissue flexibility and muscle health and strength.

At CTC of Kent, we have more than 30 years of experience with the use of ultra-flexible supra-malleolar Dynamic AFOs in persons of all ages and severity of cerebral palsy and other neuro-motor and musculo-skeletal deficits. In general, we have had fewer typical muscle shortening problems, requiring orthopedic lengthening procedures than seen with other stiffer types of bracing. Compliance is generally good, partly because this style of brace is less cosmetically obtrusive and permits a greater variety of movement strategies. Very thin and intimate support appears to reduce problems with skin breakdown and increase comfort of wear, even in adults with very severe motor problems.

Our long-term experience with supramalleolar bracing has shifted and honed our direction in therapy intervention, as well. An emphasis on active shoulder-trunk-hip control, transitional balance control and active strengthening, in as physiologically typical functional situations as possible, frame our therapeutic approach for persons of all ages with CP.

We have had a very positive experience with other ultra-flexible support systems, such as, SPIO Compressing bracing, custom contoured foam seating inserts, and BENIK Neoprene KOs, EOs and WHFOs with and without custom moldable thermoplast. These are commonly used at CTC of Kent in conjunction with supra-malleolar Dynamic AFO. Upper and lower extremity serial casting has also proved to manage increasing deformities resulting from rapid growth and other factors, dramatically reducing the need for muscle lengthening surgeries in the moderate to severely involved persons who receive services at CTC of Kent, Tacoma and Burien.

Two different case examples should offer helpful specifics about the use of supra-malleolar ultra-flexible PP bracing. The first, Boy A, has a moderate to severe spastic diplegia with very strong dynamic hypertonus into adduction, internal rotation, semi-flexion knees and hips and PF at the ankles. He began NDT based therapy at 1 year of age, began wearing DAFOs at 1.5 years, began to stand and take independent free steps at 3.5 to 4 years. In addition to weekly PT, he wore sensory level electrostimulation to his gluteals and quadriceps muscles about 4 hours/day, 5 to 6 days/week during the first 2 years of walking. The e-stim significantly improved his gait quality by reducing adductor, hamstring and PF spasticity with improved hip, knee and trunk extension stability and balance as he stood and moved about during his school day. He had some difficulties maintaining his walking skills during early puberty and had to work very hard to manage an increasing crouch and knee pain with knee extension night splinting and some serial casting. We had suggested when he was quite young, that a sport type wheelchair would be helpful for long distances or when he became tired and his gait deteriorated, so as he started high school, he became quite active in wheelchair sports and ultimately earned a sports scholarship to university. He is now 25 years, continues to be a functional free ambulatory and use his wheelchair for long distances and sports.

Girl B is currently 13 years old and I has a severe dystonic quadriplegic cerebral palsy with marked axial hypotonia and strong fluctuations into extreme extensor hypertonus. She has worn supra-malleolar DAFOs for 2-3 years since moving to the Seattle area and presented in the Spring of 2012 with 40 degree knee flexion contractures making it impossible for her to wear her KO extension splints. She had lost her ability to bear weight and assist with transfers and was getting too big for her mother to pick up. She had gone through a very rapid growth in height over the previous year.

We offered Serial Cylinder Casting as a possible help and the family was happy to try and regain her previous supported standing skills. In conjunction with serial casting, our Center always makes a provision for a least weekly therapy with an active home exercise program to promote active weight bearing, trunk and hip control. The cylinder casts had anterior drop outs to permit addition motion into knee extension and were designed to permit wearing of her DAFOs. After 3 sets of casts, she was again able to wear her KO molded extension splints fulltime in place of j the casts to continue gain knee extension range and strength. Her father noted that with the knee casts, her right foot/ankle were becoming more supinated, making DAFO wear difficult. During the 3 rd knee casting, her foot and ankle were also casted on the right to improve this situation, with good results. She is now able to assist consistently with standing transfers and has just been fitted in a TAOS orthosis to improve strength and control in standing and exercise walking. She is highly motivated support her full weight and take steps in the TAOS, even though she needs a foam collar support to manage head control.