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New Orthotic Applications for Neuromuscular Disease
by Gene Bernardoni, CO President, Ballert Orthopedic

Introduction

Orthotists work in a field with few dramatic breakthroughs. The standard orthotic appliances have been with us for quite some time. Nevertheless, innovations sometimes arise from the desire to increase patient compliance or capitalize on patient strengths while addressing their specific weaknesses. Over the past several years, I have been privileged to collaborate with Dr. Irwin Siegel, Professor of Neurological Sciences at Rush-Presbyterian-St. Luke’s Medical Center in Chicago. In this paper, I describe several ways in which Dr. Siegel and I have adapted orthotics to the needs of patients with neuromuscular disease. Because some readers may wish to emulate our work, I discuss several fabrication techniques I’ve found to be helpful.

GENE BERNARDONI, RPh, CO, is president and owner of Ballert Orthopedic, and Chief Orthotist, Cook County Hospital, in Chicago.

The Kinesceptic Ankle-Foot Orthosis

My first example is what we call a Kinesceptic Ankle-Foot Orthosis. It is designed for patients with Myotonic Dystrophy or Charcot-Marie-Tooth Syndrome. These patients typically experience impaired proprioception: that is, their ability to achieve spatial positioning through sensory feedback is compromised. The typical AFO further impairs proprioception by introducing a layer of plastic between the patient’s foot and the sole of the shoe.

With the Kinesceptic AFO, we rectify this problem by cutting out holes in the plastic so that the metatarsal heads and the calcaneus can sense the surface and contours of the sole of the shoe. These two openings allow the tripod of the foot to come through, thereby restoring a degree of sensory feedback to the patient. The Kinesceptic AFO is made from 3.2 mm or thinner polypropylene, depending on the size and weight of the patient.

Kinesceptic AFO

The position of the first opening is immediately beneath the calcaneus. This is an anterior-posterior oval the center of which is the insertion of the plantarfascia tendon. The cutout for the metatarsal heads follows the apices of those heads, with the largest diameter under the first head decreasing to the fifth.

Tone-Balancing Orthosis

We devised a similar modification for patients early in the treatment of Duchenne Muscular Dystrophy when the weakness is mild. Our idea, which we refer to as a tone-balancing orthosis, or TBO, is an adaptation of the tone-reducing orthosis, which grew out of the pioneering work of the physical therapist Nancy Hylton.

Hylton’s contribution was to map the pressure points of the foot.  Based on this work, a supramalleolar orthosis, or SMO, was developed for the treatment of patients with spasticity-producing diseases such as Cerebral Palsy.

This SMO is designed to reduce tone by supporting specific parts of the ankle and foot. We decided to try to use areas of reflex stimulation on the sole of the foot to encourage dorsiflexion while dampening plantarflexion.

	By opening the heel of an SMO we attempt to stimulate the dorsiflexion at the ankle. Adding an elevated sulcus platform distal to the metatarsal heads in a full foot plate tone-balancing orthosis creates a metatarsal well that helps to inhibit plantarflexion. Similarly, by applying pressure lateral to the Achilles tendon we inhibit plantarflexion.
SMO with Heel Opening

The pressure is created in the cast modification process by excavating plaster from each side of the Achilles tendon so that the finished SMO will apply pressure to those areas.

Because the tone-balancing orthosis is dynamic, it is important to use very thin plastic throughout, with the thinnest plastic stretching over the dorsum of the foot. The overall plastic thickness in children weighing less than 30 kg is 2.4 mm and this is stretched to about 1.6 mm over the entire orthosis and to 0.8 mm over the dorsum of the foot.

Duchenne KAFO

In later stages of Duchenne Muscular Dystrophy, tendon releases must be performed to alleviate contractures of the knees and ankles, which are threatening upright posture and ambulation. Following this surgery, we like to use a KAFO modified to accommodate the selective muscle weakness which is common to these patients. This KAFO consists of a tubular thigh section and an anterior shell AFO section similar to a floor reaction AFO.These tubular sections use the thin-walled cylinder principle for strength, thereby permitting the use of thinner plastic and reduced weight.

Duchenne KAFO

The thigh component allows the Duchenne patient with very weak hip extensors to sit on the ischial/gluteal thigh section and ambulate the typical waddling gait. Since the patient now has a locked knee, the AFO section is cast in neutral to 5° of dorsiflexion to allow the patient to maintain the weight line in front of the knees and behind the hips. The entire KAFO is strapless. Additionally, the bars are pulled inside of the plastic, where channels in the material’s thermoformed plastic support them, so that thinner and lighter bar stock, such as 3.2 mm x 12.7 mm aluminum, can be used.

The trim lines of the Duchenne KAFO are unique in two respects: First, the KAFO extends very low laterally from the thigh section almost to the actual knee joint. In this way it provides the channel of support for the bar stock. The AFO anterior shell contains the patellar tendon.

Second, to allow donning and doffing, the thigh section is cut high and the AFO section is cut low posteriorly. The patient dons the KAFO by turning it upside down, inserting his foot into the thigh section, and then turning the KAFO right side up when his foot comes to the knee joint.

We recommend that the Duchenne KAFO be applied in either of two scenarios: After surgery, Dr. Siegel puts the patient in a long-leg cast, and the patient is encouraged to stand and ambulate the same day.

One week after that, we bi-valve this cast and take an impression for the KAFO. We then replace the original cast and send the patient home to await delivery of the finished KAFO. However, if contractures are less than 20° we sometimes cast the patient prior to surgery and correct the ankle to neutral to 5° of dorsiflexion. In this case, the KAFO would be applied by Dr. Siegel immediately after surgery.

With regard to fabrication, the following considerations should be kept in mind:  In children weighing less than 30 kg we use 2.4 mm copolymer plastic and 3.2 mm x 12.7 mm aluminum barstock, while in children weighing more than 30 kg we use 4 mm copolymer plastic and 4.8 mm x 12.7 mm aluminum barstock.

After the plastic is pulled over the bars and cast and allowed to cool, the open areas are cut away from the cast. The plaster cast is then broken away from the inside of the plastic AFO section using an air hammer, much the same as is done for a prosthetic socket. The knee joint is disassembled and the thigh cuff is pushed down and removed.

Floor Reaction Ankle Foot Orthosis

Although it is not an invention of ours, I’d like to briefly describe the Floor Reaction Ankle Foot Orthosis because of its relevance to the treatment of Duchenne Muscular Dystrophy.

Between the ages of two and six years old, the child with Duchenne Muscular Dystrophy develops weakness in the hip extensors (that is, the gluteus maximus muscles). To compensate for this weakness, the child begins to walk with posterior placement of the head and shoulders in order to keep his weight line posterior to the hip joint. As the disease progresses, the knee extensors (that is, quadriceps muscles) also begin to weaken. The child adopts an increasingly lordotic posture to keep his weight line posterior to the hips and anterior to the knees.

As quadricep strength becomes weaker, the child begins to go up on his toes, widen his base of support and keep his knees locked during gait.

By walking on his toes, the child locks his knees at initial contact and continues a knee extension moment during the stance phase of his gait. Since the patient is now ambulating with both knees in extension, initial contact is fore foot contact. By doing this there is a decrease of the flexion moment at the knee that would have been caused by sharp heel strike. In essence, the child has developed his own floor reaction to initiate and/or maintain knee extension.

We may be able to help the patient at this point by fitting him with a Floor Reaction Ankle Foot Orthosis, or FRAFO as it is commonly called.

This FRAFO helps the child to lock his knee by causing posterior movement of the tibia to lock the knee during stance phase of gait.

The FRAFO is fabricated by taking an impression in the same way as for a normal thermoplastic AFO, except that the impression is taken with the patient’s foot in 5 to 10 degrees of plantarflexion.

Much of the time the patient already has a plantarflexion contracture at the ankle and will be in neutral or 5 - 10 degrees of plantarflexion already.

The FRAFO has a solid ankle and an anterior shell, but no straps. At fore foot contact during gait the anterior shell pushes the tibia posteriorly to facilitate knee extension. This allows the child to maintain his knee in a locked position while also helping to maintain medio-lateral support and balance.

Toronto Boot AFO

As ambulation becomes more difficult with progressive muscle weakness, the Duchenne Muscular Dystrophy patient begins to spend more time in the wheelchair. Contractures of the hips, knees and ankles become more problematic. Standing is good for the patient for both psychological and physiological reasons, so the child is encouraged to spend time during the day standing in his KAFO’s even if he no longer ambulates with them.

If knee contractures are less than 15 degrees, I use a “Dial Lock” or “Step-Lock” knee joint at the knee to try to prevent progression or decrease the contractures.

Even though a child may be wheelchair-bound at this point in the progress of this disease, maintaining a plantigrade foot is extremely important for two reasons.

First, it allows the patient to continue standing for as long as possible. And, second, even in the wheelchair it allows proper alignment of the foot in the foot rest, while permitting the patient to wear normal shoes. For psychological reasons it is good for the child to wear the shoes endorsed by a popular sports figure just as other children are doing.

To achieve this goal we use AFO Night Splints called Toronto Boot AFOs.

Toronto Boots are thermoplastic AFOs lined with leather posterior to the heel about 96 mm superior and inferior to the calcaneus. The boot includes a wide leather closure anterior to the dorsal aspect of the foot to hold the splint on at night. The leather lining behind the heel serves to make the AFO more comfortable for nighttime use and to prevent skin breakdown at the calcaneus and medial and lateral malleoli. The wide tongue and strap are also more comfortable than narrow straps in holding the heel down in the AFO.

Spoon-style AFO

I’d like to describe next a modification I designed to overcome aversion to bracing in patients in the early stages of Charcot-Marie-Tooth Syndrome, or CMT. Typically CMT patients are just beginning to experience weakness and imbalance; they may have stumbled or tripped, yet may be resistant to the idea of wearing a brace. We have found that a simple modification of the standard AFO succeeds in raising patient compliance.

Spoon-Syle AFO

The AFO is trimmed to medium-calf height and the leather strap eliminated, producing what we call a “spoon-style” AFO.

The “spoon-style” AFO can be made from beige-colored copolymer or polypropylene. If made thin enough it can be worn under beige hose. Because the appliance is so abbreviated, it can be worn with a skirt. The patient must wear a lace-up shoe to hold the orthosis on the foot. The trim line should be flexible to provide a posterior leaf spring or dorsiflexion assist orthosis.

Remember that CMT produces a very characteristic, extremely cavus foot.

Consequently, it is very important that the AFO be in total contact with and support the longitudinal arch. If there is toe-clawing in such a patient, a sulcus roll made out of nickelplast (or a firm durometer foam) material may be glued onto the AFO.

Foot Orthotic

Another orthosis that I use in the treatment of patients with Charcot-Marie-Tooth Syndrome, or CMT, is really not a new orthosis but special modifications of a standard orthosis to better accommodate the patient with CMT. It is the Foot Orthotic, or FO, and it is the device that most lay people think of when someone talks about orthotics.

The symptoms of CMT include weakness and atrophy of the muscles innervated by the peroneal nerves -- the evertors of the foot; weakness of the anterior tibialis -- the dorsiflexors of the foot; and the atrophy of the intrinsic muscles of the foot.

These atrophies affect the patient in two ways. The weakness of the anterior tibialis and evertors causes the patient to develop weakness of dorsiflexion and eversion resulting in tripping and inversion injuries (that is, sprained ankles) later in the course of the disease.

This is a result of the inversion of the foot during swing phase of gait and weakness of dorsiflexion resulting in “drop foot.”

The dorsiflexion weakness coupled with the atrophy of the intrinsic muscles causes foot pain with thick callous formation under the metatarsal heads and calcaneus. The pain is caused by the foot slapping, which in turn is due to the lack of normal dampening action of the pretibial muscles at heel strike in conjunction with the lack of normal padding around and under the metatarsal heads due to the intrinsic atrophy. This combination of atrophies and weaknesses causes the patient to develop a rigid, equinocavovarus foot.

The equinocavovarus foot is characterized by a high arch and toes flexed at the interphalangeal joints, and the metatarsophalangeal joints are dorsiflexed with the toes drawn back to the dorsum of the foot. The first time a patient presents to the orthotist for orthotic intervention, he may not be aware of his disease. The foot pain and callous formation may prompt his doctor to prescribe foot orthotics. Examination of the patient’s foot will usually reveal the muscle weaknesses, atrophy and equinocavovarus foot.

We take a plaster impression of the patient’s feet in as close to a neutral position as possible. We then make a positive impression in the usual way with a plaster slurry. An impression of the full plantar surface of the foot must be made since the Foot Orthotic will be a full length foot plate. In the modification process, care must be taken to create a metatarsal pad proximal to the metatarsal heads.

Distal to the metatarsal heads we create a “sulcus” pad or toe crest.  This combination causes the formation of a metatarsal “well.”

The longitudinal arch should not be modified out. Modification is very important because it provides two mechanical methods to relieve metatarsal pain. The combination of the high longitudinal arch with metatarsal pad proximal to the metatarsal heads and the sulcus role distal to them creates a “well” or trough to relieve the metatarsal heads.

We usually make the foot orthotics out of a firm durometer foam or cork rather than a plastic FO with a leather liner. However, any thermoplastic AFO should also have this custom foot plate. The “sulcus” pad of firm durometer foam may be glued into the AFO after thermoforming and trimming.

In making a FO we may relieve the calcaneus by either creating a well under the insertion of the plantarfascia tendon or using a softer durometer foam in the heel of the FO.

When making this relief in a thermoplastic AFO, it is necessary to excavate plaster from the cast both medial and lateral to the heel to force the fat pad of the heel under the calcaneus or to glue a soft durometer foam “donut” shaped pad into the heel of the AFO.

Wire Frame Cervical Orthosis

The typical cervical orthosis is often used to immobilize the neck in order to prevent pain, allow healing after surgery or prevent further injury. However, for patients suffering from Myotonic Dystrophy or Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease), the goal may be to provide cervical support while allowing as much movement as possible.

Patients with Myotonic Dystrophy have difficulty relaxing the muscles after contraction. This “tone” may mask the underlying weakness and allow ambulation.

Ultimately, however, another effect of this disease is to cause severe weakness and wasting of the massiter, temporal and sternocleidomastoid muscles. The weakness can make it very difficult for these patients to hold their heads up.

Similarly, patients with Amyotrophic Lateral Sclerosis develop this same cervical weakness.

Our solution is a wire-frame collar with a spring-fed mandibular attachment that allows rotation of the head and mandibular movement while helping the patient to balance his head on his shoulders. The flat mandibular attachment allows side-to-side motion. The gauge of the wire is varied to counterbalance the weight of the head, while allowing mandibular movement. In addition to the mandibular piece, the collar consists of a simple occipital strap and a sternal extension.

Wire Frame Collar

Because it is made from foam and wire only, it is light-weight and allows for air circulation.

We use .102 decimal diameter gauge stainless steel piano wire for patients over 168 cm in height and .086 decimal diameter gauge in shorter patients. The mandibular piece is made in two lengths, 12 cm and 18 cm, measured from the center of the spring. For comfort, there is aliplast padding on the mandibular piece, between the lateral neck and the spring, and on the occipital strap. The angle of the mandibular piece may be changed by opening or closing the spring.

My final example illustrates the virtue of simplicity in treating some of the orthotic challenges posed by children with neuromuscular disease.

Parapodium Frame with Orlaw Walker Feet

Children suffering from Spinal Muscular Atrophy, or SMA Type 2, are encouraged for physiological and psychological reasons to stand and ambulate at the appropriate developmental age. Typical HKAFO’s or KAFO’s, however, require more truncal strength than all but the most exceptional of these children possess.

Likewise, the reciprocating gait orthosis, or RGO, is successful only for the strongest of these patients because of the strength and motor ability they require. The RGO was developed to treat patients with spina bifida. It requires upper arm strength to operate with either a walker or forearm crutches, and this is something that few SMA patients possess. On the contrary, the SMA Type 2 patient is characterized by degenerative weakness in the upper limbs and trunk areas.

For psychological reasons, then, it is important to fit the SMA Type 2 patient with an orthosis with which he can be successful. Faced with this need, we developed a protocol which combines the use of a parapodium frame with the duck feet of an Orlaw Walker.

At the first signs of the patient wanting to stand, or at a developmental age between 8 and 16 months when standing is appropriate, the parent begins placing the patient in the parapodium frame several times throughout the course of each day. Inside the frame, the child may play with his toys on an adjacent low table or chair.

When the child begins to rock the frame from side to side and show interest in mobility, we attach the duck feet from an Orlaw Walker, thereby providing the child the means to move himself around. The addition of the duck feet typically occurs between 16 and 24 months of age.

This hybrid orthosis has several significant advantages over other orthotic devices designed for mobility. First, it gives the child the means to move about with a minimum of side-to-side head motion. Second, no upper arm strength is needed for mobility. Third, because the hands are not required for mobility, they can be used to play. And finally, the achievability of the goal leads to a sense of success for the child.

Parapodium Walker

As previously noted, the management of the SMA Type 2 child centers around helping that child achieve developmental milestones. The next major area of orthotic intervention applies to truncal weakness. For a variety of reasons, the SMA Type 2 child has a high incidence of scoliosis. Truncal weakness and prolonged wheelchair sitting during maximum growth years combine to promote the progression of scoliosis. It is therefore important to initiate TLSO orthotic management early if there is to be any chance of success.

Delays in treatment can give rise to a number of problems, any one of which may be insurmountable. For example, if the curve is allowed to progress, the lateral pressure required to correct the curve will exceed capillary pressure and cause skin breakdown.

As with the Duchenne Muscular Dystrophy patient, prolonged wheelchair sitting and inacitivity promote obesity, which is always a problem in orthotic management of scoliosis. Wheelchair sitting also allows the development of contractures, which can affect the normal A-P curves of the spine and make it more difficult to brace for scoliosis. The flexion contractures of the knees due to tight hamstrings pull the pelvis into a posterior tilted position which, coupled with severe hypotonia, cause lumbar and thoracic kyphosis.

To further complicate matters, we are faced with the problem of respiratory compromise in these children, the same condition that makes spinal fusion an unacceptable treatment. Normal protocol for a child not afflicted with this disease would be to make a TLSO or custom seating to slow or prevent progression until the child reaches skeletal maturity, then perform a spinal fusion with instrumentation.

But such spinal fusions take between 6 and 12 hours under general anesthesia and the chances of an SMA Type 2 child surviving the surgery are slim. As one surgeon said to me, “Fixing this child’s back would be easy, it’s keeping him alive that would be hard.”

I have tried a number of cut-out and elastic panel designs in an attempt to prevent further compromise respiration in these patients. A few years back, a respiratory therapist and I did tests on two designs of TLSO’s with cut-outs. The breathing test showed the TLSO with a simple abdominal cut-out beneath the inferior costal margin was better tolerated by the patient.

If, as may happen in some children, their abdomen protrudes, I like to use a thin elastic binder under the TLSO. The TLSO is of the neuromuscular type. This means that instead of pads we excavate plaster in the position of the pad in the positive model and add plaster opposite to allow for trunk shift. The TLSO is high profile for seating balance. The anterior superior trimlines are 24 - 48 mm inferior to the sternal notch and 12 - 24 mm inferior to the clavical bilaterally and the inferior trimlines are the usual 24 mm superior to symphysis pubis. The top center of the abdominal cut-out is 24 mm inferior to the xyphoid.

TLSO with Abdominal Cutout

Conclusion
These are examples of how the thoughtful prescription and fabrication of orthoses can assist in the management of the patient with neuromuscular disease. There are no doubt other applications awaiting discovery by creative practitioners in the profession.

References

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