Recipe for a Wheelchair Prescription:

Spina Bifida in the new Millennia

Gloria Leibel B.Sc. PT, Linda J. Patrick B.Sc. PT

Bloorview MacMillan Children’s Centre

Introduction

Clinicians involved in the prescription of seating and mobility equipment need to be aware of their client’s current and future needs. In this presentation we have attempted to use the concept of evidence-based practice in order to develop clinical guidelines when prescribing equipment for clients with a diagnosis of spina bifida. We have included medical information about spina bifida and a review of current literature illustrating the effects of propulsion using a manual w/c. An overview of current w/c frames and features will be discussed in order to help the prescriber find the optimum fit for these very unique clients.

Spina bifida (SB) is defined as the incomplete formation of the spine and spinal cord. This occurs before birth and results in paralysis, loss of sensation of the legs and affects the functioning of the bowel and bladder. Approximately 85-90 percent of these clients also have hydrocephalus (an increased collection of cerebrospinal fluid in the brain due to blockage) Hydrocephalus can affect visual, hearing and learning abilities and may need surgical intervention. An average of one in 750 children in Canada are born with spina bifida. (1998)1

Types of presentation you may see:

1) Myelomeningocele (severe form): bones fail to close around the spinal cord at the site of the lesion and the meninges and the spinal cord protrudes to form a sac; results in failure of development of the cord and spinal nerves are damaged. This sac contains cerebral spinal fluid (CSF) and can be transparent with no skin coverage.

2) Meningocele (less severe): bones do not close around the spinal cord at the site of the lesion, this results in meninges pushed through the opening to form a sac. Sac is often covered with skin.

3) Lipomyelomeningocele: protrusion of abnormal fatty tissue through a defect in the vertebrae; results in damage to the nerves as a result of compression by the mass or due to abnormal formation of the spinal cord.

4) Occulta (mild): a small hole in the lower segment of the spine; there is no sac at the site of the bony deformity; the area may be marked by a dimple or tuft of hair.

Other neurological conditions that can be associated with SB

1) Chiari II Malformation: brain stem is lower than usual and compresses the upper part of the spinal cord in the neck (nearly all with myelomeningocele have this, about 15% of children with Chiari II malformation develop severe symptoms such as aspiration, apnea, feeding problems, tightness or weakness of arms). This may need surgical intervention.

2) Tethered Cord: spinal cord gets stuck at the site of the lesion and cannot slide therefore it gets stretched as the child grows. It can result in symptoms such as bladder or bowel changes, back pain, increase spasticity, scoliosis. This may need surgical intervention.

3) Syringomyelia: abnormal pocket of CSF forms inside the spinal cord. This results in increased scoliosis, upper extremity weakness, spasticity, and changes in sensation of the hands. This may need surgical intervention.

Orthopaedic considerations

1) Spinal curvatures: any muscle imbalance around the spine affects the position of the vertebrae and can result in a spinal curve (lordosis, kyphosis, or scoliosis). In reviewing papers concerned with spinal surgeries, 50% had increased flexion contractures of the hips at follow-up and a decrease in motoric skills and ambulation capacity.2

2) Spinal dysraphism: no spinal processes and/or enclosed vertebral bodies. This may result in the improper attachment of spinal muscles in the right position to create spinal extension.

3) Foot deformities: club feet, equinus, calcaneus, varus, valgus.

4) Dislocated hips: occurs with an imbalance of muscle pull due to spasticity or poor bony formation of the acetabulum as a result of non -weight bearing. A review of papers reveals that between 30-50% of children with SB have dislocated hips but it is rarely painful. The aim of management for bilateral hip dislocation has changed in the last 3 decades. The potential for walking is determined by the severity of motor and sensory deficits rather than whether the hips are dislocated.3 Children with quadriceps power of grade 4 or 5 may continue to walk in adult life, whereas those children with high-level lesions may walk during childhood but usually use w/cs for mobility in adult life. Patients who are ambulatory had a significantly higher energy cost than those using w/cs. Lack of functional improvement following surgery for dislocated hips was explained by a significant number of surgical failures. There was no difference in function between the operated and conservative group.4

Bowel and bladder concerns

The amount of bowel and bladder muscle control and sensation will vary depending on the level of the lesion as well as the amount of damage to the nerves. If the muscles of the bowel are weak, constipation can be a problem. If the anal sphincter muscles are weak this can result in fecal incontinence (accidents). Bowel and bladder routines will vary; scheduling is an important feature along with ease of transfers. These routines have a major impact and should be considered when prescribing a w/c in terms of continence and assessing transfers.

Anthropometrics

In preparation for this presentation a series of measurements were collected at clinics to support the clinicians’ anecdotal information re the distinct body shape of children with spina bifida and how this may impact on the prescription of a wheelchair. The clients tend to be short in stature with short trunks and if non-weight bearing, short lower extremities. An example of this body shape was a five-year-old boy, his w/c measurements 20x14: at one point in order to improve the stability of the w/c it was suggested that an outrigger be used instead of anti-tippers.

Technology of wheelchairs: what is available ?

Features to consider: squeeze, height adjustable back canes, detachable push handles, multiple wheel options, multiple casters and forks, axle plate options, front rigging configurations including swing away, 60,70, 90 degree and tapered hangers with angle adjustable foot plates, one piece angle adjustable foot plate, detachable height adjustable armrests, camber, weight.

Rigid frames:

1. designed for active users, sports enthusiasts: characterized by rigid tapered front end, adjustable camber (2 types-axle plates adjusted with washers, or one piece camber bar with machined axle sleeves), adjustable centre of gravity (rear wheel position and caster position, seat angle) lightweight traditional rigid non-growing frame. They are specifically designed for strength and performance (mobility issues). Range in size from 14-20 inches.

2. growing rigid frame aimed at the paediatric population: although they are growable, they do not have cross-braces but instead have horizontal tubes which can be replaced for growth. Typically they have swing away front ends and depth adjustable back posts. They are designed to deal with seating and growth issues. Size range 10-18.

Folding frames:

Standard cross-brace configuration available with rigid or swingaway front end, growable, folds sideways to transport, accommodates more complex seating, allows for greater than 1 inch suspended seat base. These are designed for stability and tend to be a heavier frame.

Best Practice Prescriptions

The following points for discussion were found in various articles pertaining to the issues surrounding propulsion. There were very few articles that were specific to the Spina Bifida population and even fewer directly looking at paediatrics. The information is based mainly on studies of adult manual w/c users (mostly people with spinal cord injuries), on biomechanics of the shoulder and elbow joint, and the configurations of the wheelchairs. One study did find little difference in the manner in which paediatric w/c users propel their w/cs when compared with a neurologically matched adult population.5 This is a cautionary tale for clinicians doing manual wheelchair prescriptions for paediatric clients.

Maneuverability versus stability

Children with SB rarely experience the sensation of falling or speed. They may be fearful and tend not to explore their environment. Cautious parents may inadvertently limit a child’s development of independence. The clinician needs to work with the family/client to set realistic goals for the prescription of this equipment, e.g. mobility versus stability.

From the literature reviewed the following biomechanical principals are supported. When the axle position is moved forward, the rolling resistance is decreased and propulsion efficiency is increased.6 The effect of seat height was found to have significant effects on gross mechanical efficiency, oxygen cost, pushrange, duration and motion. Rolling resistance is decreased and more of the pushrim is accessible to the manual wheelchair user with the axle placed forward and higher relative to the shoulder. Therefore w/c users with a forward-high axle have a decreased frequency of propulsion, spend more time on the pushrim, and have lower pushrim forces. If more weight is distributed over the larger rear wheels, the rolling resistance decreases. Increased push angle equals more force and a decrease in frequency of propulsion.7 A more forward axle places weight over the back wheels decreasing turning radius, decreasing flutter in the front casters and allowing for curb hopping and wheelies; however, it is easier to tip backwards.

Some clients choose stability over maneuverability. In one study reviewed, individuals with Spinal Cord Injury had their w/cs set up with the axles more posterior relative to the shoulder. In some cases older clients had become accustomed to the rearward position of the axle. It was hypothesized that clinicians are recently doing a better job of fitting w/c to client and paying more attention to biomechanics. However, individuals may not like this set up, start to feel less stable and adjust their axles back to increase stability of their w/c. 7

Pain and Discomfort

Wheelchair propulsion is a repetitive, cyclical movement. It is the product of a user-machine interface. For children disabled in their lower extremities this is a life long experience. The shoulder joint is the most freely moving joint in the body and it is also one of the most unstable. People with lower extremity dysfunction must rely extensively on their shoulders while performing many activities e.g. propulsion, transfers, and lifts.8

The upper extremity is not designed for repetitive loading. Manual w/c users are prone to shoulder injuries. In survey studies, 31%-73% of manual w/c users reported shoulder pain. Bayley et al found rotator cuff tears in 65% of individuals with paraplegia and shoulder pain.9 In all the studies reviewed, the authors felt that pain and abnormalities seen were at least in part related to overuse of the arm during wheelchair propulsion.10

Median nerve dysfunction is directly correlated to propulsion frequency and total pushrim force. There is a correlation between median nerve injuries (a marker for carpal tunnel syndrome) and axle position relative to the shoulder. It has been hypothesized that decreasing the frequency of propulsion may help prevent median nerve injury. Providing wheelchair users with adjustable axle position and then fitting the user to the wheelchair can improve propulsion biomechanics and likely reduce the risk of injury.7

In discussion with children and families at the Combined SB Clinic at Bloorview Macmillan, when the clients were asked specifically about shoulder pain and discomfort, almost all of the children reported some discomfort. Clients stated that no one ever asked about this before. Parents were surprised. Parents felt that their child was not propelling efficiently.

Energy costs

It has been documented that fatigue is an issue both with the ambulators and w/c users. The clients who ambulate often begin to depend on w/c mobility as the demands in the environment increase, i.e. high school- carrying books and long distances between classes. Clients in the older age group reported that it had become increasingly more difficult to manage in their environment. For the T 12 or higher-level lesion this often means moving into more light weight rigid frames or in some cases power w/c’s.

Lifestyle and Independence

It is important for the clinician to work with the family/client to clarify where and how the w/c will be used. How will the w/c be transported –folded or in a van with a lift? Where will the client use the w/c – inside/outside, in the city/country? Is the client independent on uneven surfaces/ramps? How does the client transfer into and out of the w/c (toilet routine)?

The Recipe: Wheelchair Prescription for the child with Spina Bifida

Factors to consider:

1. age of child 5. type of seating required 9. growability

2. level of lesion 6. transfers 10. foldability/transportation

3. shape of child 7. environment 11. level of independence of client

4. level of cognition 8. weight/set up of the chair

Options which are presented at the first prescription may impact the client’s lifestyle in the future. Wheelchairs are often built generically. There is nothing generic about this population in terms of their function and body type, therefore careful consideration is required when choosing a specific wheelchair.

The therapist should consider the family/client needs in the areas of maneuverability versus stability, biomechanics of the shoulder and elbow joint, energy costs, lifestyle and independence. It may be necessary to trial different equipment to determine the best client/w/c fit. Set up of the w/c needs to be customized to the client. One of the issues that became apparent during this investigation was the impact of centre of gravity adjustment. Because these clients often have extreme orthopaedic deformities, the weight distribution of the client is unbalanced, making the set up of the wheelchair challenging. Sometimes it is necessary to order a wider w/c and recess the back between the canes to distribute the weight accordingly. In order to compensate, camber would be added for better wheel access and sideways stability. At times as prescribing therapists, we have erred by stressing growth and foldability of the w/c instead of the maneuverability and set up of the equipment. With the new technology now available one can prescribe a w/c, which is rigid but can be folded, lightweight but extremely strong and adjusted to the specifics of the client in question. As responsible prescribers we need to consider the orthopaedic risks of using a manual w/c for all activities. Weight and set up of the frame will make a difference in a client’s life.

Recently, a w/c skills camp was held at the Bloorview Macmillan Children’s Centre. It became obvious that the clients’ w/c’s were set up for stability not mobility. Many of the children participating in the camp were fearful when the w/c set up was changed to allow maximum maneuverability. Training was stressed by mentors and w/c athletes who reviewed such activities as falling out of the w/c, wheelies, ramps, curb jumping. Clients experienced greater maneuverability and with training enjoyed the increased freedom.

References

1 Spina Bifida Team of Bloorview Macmillan Centre.Understanding Spina Bifida.1-19.

2 E Berned Muller et al. Influence of surgical treatment of scoliosis in children with spina bifida on ambulation and motoric skills. ACTA PAEDIATR.1992: 81: 173-6

3 Minne Heeg et al. Bilateral dislocation of the hip in spina bifida: A long-term follow-up. Journal of Pediatric Orthopaedics. 1998: 18: 434-436.

4 B.Alman, M Bhandari, J.Wright. Function of dislocated hips in children with lower level spina bifida. Journal of Bone and Joint Surgery. 1996: 294-8.

5 J.H.Bednarczyk, D.J.Sanderson. Kinematics of wheelchair propulsion in adults and children with spinal cord injury. Arch Phys Med Rehab Dec 1994:75:1327-34.

6 Brubaker CE. Wheelchair prescription: an analysis of factors that affect mobility and performance. Journal of Rehabil Res Dev. 1986:23: 19-26

7 Michael L.Boninger, Mark Baldwin, Rory A. Cooper, Alice Koontz, Leighton Chan. Manual wheelchair pushrim biomechanics and axle position. Arch Phys Med Rehabil May 2000: 81: 608-13.

8 A.M.Kootz, R.A. Cooper,M.L. Boninger, B.T. Fay, M.A. Baldwin. Shoulder joint forces and moments during two speeds of wheelchair propulsion

Notes: