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INTERNATIONAL FORUM--Providing Orthoses forSpina-Bifida Patients

Klaus Dittmer

ABSTRACT

The key to success in providing orthoses for spina-bifida patients is understanding the disability's complexities. Different levels of lesions which accompany a lack of sensation require very specific treatments. This article discusses various treatment options.

Introduction

The application of biomechanics to orthopedic technologies requires an approach that considers problems that result from combining external technical structures with the human body. In the past, spina-bifida patients were treated with the same orthotic methods as polio or paraplegia patients. However, symptoms of spina-bifida paralysis are very specific as should be its treatment.

X-rays of the disorder, which consists of malformations of the trunk, skeleton and spinal nervous system, only show the extent of the defect. The level of the lesion and the treatment plan can be determined only after detailed investigations.

Once the level of the lesion is known, and an orthosis has been chosen, the medical requirements must be complied with mechanically. The following questions should be addressed:

• Is the condition in line with the patient's age?
• What muscular incapacity is observed?
• Which faulty positions can be corrected?
• Which joints have to be included?
• What purpose is served by the orthosis or any additional aid?
• How long will the orthosis be used?
• What reactions will be produced?
• What are the disorder-specific warning signals?

With spina bifida, the patient's age is very important. Selecting and working with lightweight, skin-compatible materials is essential since walking will be the most important form of locomotion.

Thus, orthotic treatment should correct deformities, prevent contractures and promote development of the child's mobility. Mental control of the device should be addressed only after these goals are achieved.

Positioning aids may be fitted on children as young as six months. Physiotherapeutic mobilization and stretch exercises are very important in preventing coxal paralytic luxation, hip flexion contracture, talipes equinus, clubfoot, talipes calcaneus and knee stiffness. These conditions are counteracted by positioning aids, which must be constructed and fitted carefully. It is rarely possible to overcome an existing contracture by positioning aids, however.

Provisions vary greatly depending on the materials, the patient's age and the level of the lesion. Following are just a few examples.

Lesions at the sacral segment S3 level result in functional disturbances of the foot muscles. Thus, inlays and corrective shoes will have to compensate for active formation of the foot arch.

For lesions at the sacral segment S2 level, the thigh and lower leg muscles will be so affected that lower leg orthoses will be necessary. Faulty axial positions may be corrected with spiral orthoses or knee condyle beds. Lesions at the sacral segment S1 level may require thigh positioning to prevent secondary damage such as external tibia rotation and a valgus position in the knee. Lesions at the lumbar segment L5 level require knee-ankle-foot orthoses. A pelvis bracket with elastic bands counteracts the inner rotation that is often present since there are no antagonists for the adductors.

Lesions at the lumbar segment L4 level often require hip-ankle-foot orthoses (HKAFOs), provided with hip abduction joints to absorb pronounced internal rotation forces.

For lesions at the lumbar segment L3 level, the pelvis must be encased. A hip rotation joint with an arresting effect will exert a stabilizing effect since the hip extensors are no longer active. Limited rotation permits walking to a certain degree.

Lesions at the lumbar segment L2 level require an adjustable hip rotation joint and an orthosis to encase the pelvis and thorax. Since the musculus quadratus lumborum is still active, walking can be achieved to a certain degree. For lesions at the lumbar segment L1 level, the musculus quadratus lumborum is inactive. A reciprocal hip joint system of the LSU type produced by Fillauer should be employed. If an upright gait is required, this hip joint is the only means of treating damage to the thorax region. Other alternatives include corsets or wheelchairs.

Compared with these traditional examples, what constitutes an innovative approach?

• Helping the child assume an upright position at an early age. The child's general mental and motor development must always be considered to ensure the child is not stressed excessively or subjected to disappointment.
• Attention to the gravity line of the orthosis to release the movement angle in the ankle and hip joints in a suitable dosaged way.
• Bearing in mind the necessary corrections, unaccompanied locomotion should always be the goal.
• Corrections without a gain in possible locomotion are not desired.

Therapeutic Corrective Shoes

In the case of sacral segment 83 lesions, foot muscles are severely damaged. The great toe flexor (musculus flexor halluxis longus) is inactive, and patients cannot stand on their toes. Thus, active consolidation of the foot arch is not possible. With pes valgus, the calcaneus tends to tip over, leading to a shortening of the Achilles tendon. The disorder can be treated with comprehensive inlays or stiff, ankle-high corrective shoes.

The therapeutic corrective shoe was developed specifically for patients with inadequate foot arch and ankle joint stability (see Figure 1 ). The shaft of the shoe extends approximately 5 cm above the ankle joint and has reinforcement that extends medially to the metatarsophalangeal joint and laterally to the middle of the foot.

In addition to the stable footbed, a medial wing-type heel prevents the shoe from deforming with normal use. Individual changes can be made easily to the foot bed and ankle region.

The shoe has a boxcalf leather upper and insole. The internal leather lining is continuous, and additional cushioning is provided in the ankle area. A steel spring in the sole provides stability.

Specially developed, small series shoes are available for patients who previously received only comprehensive inlays or "individually made-to-measure shoes." Patients welcomed the shoes' economical price and immediate availability as major improvements.

Cast Resin Devices with Soft Footbeds

New production methods have been introduced for orthoses made of cast resin and thermoplastic materials that integrate articulated connections. These devices embed the entire foot and stretch from the toes to well above the ankle joint. A removable soft lining enhances correction.

The calf and foot parts of the orthosis overlap at the height of the ankle joint. This articulation is limited in the plantar and dorsal directions by the angular position of the foot part. The rigid foot part also encloses the toes to achieve an upright, stabilized lower-leg position-the pre condition for any higher orthosis.

The plaster cast of the leg is taken with the leg in the best possible corrected position. The foot area is modeled on the positive of the plaster cast so the model stands smoothly on its base with optimum correction and minimum heel height. A slight forward dorsal tilt of 5 to 8 degrees shifts the gravity line of the body to the middle of the foot (see Figure 2 and Figure 3 ).

Producing a separate foot part requires a separate plaster model that is recast from the original plaster model.

A soft footbed then is shaped from low-temperature Polyform¹ and smoothed down for the final fit (see Figure 4 ). The soft footbed extends 4 to 8 cm above the ankle joint, embedding the foot at its most sensitive places. The hard foot shell bearing the weight of the body is then cast with carbon laminate above the soft interior (see Figure 5 ). The curing temperature and the under pressure that occur during the casting process ensure extensive contact between the soft footbed and the foot part after the plaster structure is removed. The shaped foot part with the soft cushion footbed is applied to the original plaster leg model, and the thermoplastic calf part is pressed over the calf and foot part.

The ankle joint is marked in parallel on the orthoses then drilled and secured with screws. Joint mobility and the degree of plantar and dorsal movement are controlled by the dorsal shaping and foot embedding of the calf sleeve.

When the device is first fitted, mobility is kept to a minimum. Later modifications provide 8 to 10 degrees with a dorsal forward tilt of about 8 degrees. The soft footbed encases the endangered part of the foot. Small cushioned parts overcome pressure points and absorb additional correction forces.

Results

The soft footbed cushions the limb and prevents pressure points (without affecting the fit under long-term stress). Difficult foot conditions, including those with open pressure sores, have been treated with positive results. The greater amount of work involved with this type of orthotic device is not only justified but necessary, particularly for patients who suffer from lack of sensation.

Shoes for Orthoses

The success of orthoses improves considerably with well fitted shoes. The shoe typically used with orthoses was created for the first spina-bifida patient who was fitted with an orthosis with a soft footbed. Only much larger ready-to wear shoes would accommodate this orthosis. Normal commercial shoes would require flatter heels and an area above the instep and the heel or toe-cap large enough to accept the toe embedding drawn up around the sides of the orthosis. The orthotic shoe was developed in 1987 (see Figure 6 ).

A Hip Joint for Orthotic Aids

The mechanics of natural hip joints can be compared to those of ball joints. The planes of movement are always at a 90-degree angle to the axes. Since movement exists in three planes, there are six main directions of movement: flexion/extension, adduction/ abduction and endorotation/ exorotation.

The leg can be moved around three main axes in relation to the pelvis. The normal position is the standing position relative to the pelvis. From this position the leg can be raised 90 degrees with the knee straight-i.e., it can be moved to the anteversion or anteflexion position. The leg can move backward from the normal position only 15 to 20 degrees. In the upright standing position, abduction of 50 percent is possible (40 to 50 degrees with the hip and the knee both bent at right angles). With the hip straight, endorotation amounts to 20 to 30 degrees (30 to 40 degrees with the hip and knee bent).

These ranges need not be duplicated exactly in an orthotic hip joint. However, the joint should allow endorotation and exorotation with a stable connection between the orthotic leg component and the orthotic pelvis or trunk component. An angular deflection of 20 degrees should be permissible with the joint locked. In spite of orthotic hip joint blockage, a stride length very close to normal locomotion can be achieved.

Previously, only hip joints with one axis of mobility or hip abduction joints with two axes of movement were available for pelvis-high orthoses.

Some rotary movement was made possible by the material of the pelvis embedding. Otherwise, the rotary forces resulted in such high material stress that splint fracture was a risk. The "rocking gait," made possible by a hip joint where both sides were locked, or a hip abduction joint locked on one side while the opposing side was released were the two variants of pelvis-high orthoses with (lumbar level) paralysis. Thus, it was necessary to devote more attention to the rotary movements when using doublesided pelvis-high orthotic aids.

Starting in 1983, attempts were made in Italy to provide rotary movement in an orthotic hip joint. Dr. Ferrari of the University of Parma and S. Ciarolo and B. Bassi of the Centro Orthopedico Emiliano designed and produced a hip joint that permitted rotary movement and an adjustable stride length with a locked orthotic hip joint. Many spina-bifida patients and patients with atrophied spinal muscles have been fitted with this type of hip joint.

Since 1988, another hip joint variant has been used successfully with HKAFOs (see Figure 7 ). It can be used only when there is an active musculus quadratus lumborum and no marked malposition with endo- or exorotation. Correction of severe malpositions is not possible with the rotary hip joint. However, slight directional deviations can be influenced by elastic bands attached to the pelvis.

The hip area has a fixed center of rotation through which the axes for flexion/extension pass, as well as abduction/ adduction and endorotation/exorotation-all the axes important to orthosis design.

The axis for flexion and extension movements coincides with the transverse anatomic hip joint axis, i.e., the axis passing through the center of rotation of both hip joints. Therefore, the height of the mechanical hip joint must be arranged above the level of the greater trochanter. The uppermost palpable part of the trochanter serves as a measurement reference point.

Design of the Rotary Hip Joint

After determining the construction height, the orthotic joint is combined so that the bending axis coincides with the horizontal axis of the hip joint. The upper part of the joint should be oriented toward the pelvis so that it abuts against the box guide during active extension of the hip. The falling latch should lock the joint.

On the bending side, the upper joint component in the standing position should not abut against the front box edge of the lower joint part. The upper part of the joint must have free-swinging play to enable a stride length. A light elastic rubber band for the gluteus helps straighten the hip so the stride length release of the hip joint can be used to adjust the stride length (see Figure 8 )

In the fabrication of HKAFOs, the function of the quadratus lumborum should serve as an important criterion for the choice of the orthotic hip joint design. When combined with a rotary hip joint and falling latch, it permits the leg to be raised from the ground, allowing a certain stride length. The walking performance of patients and overall physical development improved.

The rotary joint is manufactured from highly alloyed stainless steel and is available in three sizes (see Figure 9 ). This orthosis uses a fixed cast-resin foot part and hip joint arrestment. The fixed foot part extending over the length of the foot stabilizes the knee, eliminating a knee arrestment system even though no quadriceps muscle exists.

In view of the child's fast growth in relation to the stabilizing foot length, this variant cannot be adapted.

KLAUS DITTMER is an orthotist/prosthetist in Berlin, Germany, where he operates his own company, Ortho-Ped Dittmer, Blissestr. 13/15, D-10713 Berlin, and specializes in O&P services.

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