Customized from the Ground Up
Building mobility solutions from the ground up with appropriate seating and accessories promotes improved function and overall quality of life.
by Erin Michael, PT, DPT, ATP/SMS, and Elizabeth Farrell, PT, DPT, ATP
Following a spinal cord injury or acquired neurological insult, individuals may experience a change in functional status that results in decreased ability to ambulate. Many people with neurological impairments rely on a manual or power wheelchair as their primary or only means of mobility. It is estimated that as many as 1.6 million Americans are wheelchair users.1 When an individual uses a wheelchair as the primary means of mobility, access to that person’s environment may be limited. The ability to perform mobility-related activities of daily living may be limited, and the individual’s overall independence may be limited.
The way in which a wheelchair is configured for the individual can significantly impact the person’s functional abilities. Likewise, a wheelchair that is not optimally designed for the user may result in devastating physical and medical consequences, such as the development of a wound, postural abnormalities, or progression of orthopedic deformities. During a seating clinic evaluation, a wheelchair is customized for the patient based on the individual’s positioning and functional needs. The chair is designed for each individual with the same end goal in mind: improve function for the patient to allow for increased independence. From frame selection to cushions and backs, each item on the manual wheelchair is chosen to serve a specific purpose. Options are not only discussed with the patient, but trialed in seating clinic. It is not enough to ensure that the patient looks good and feels comfortable in the chair. Patients must be able to brush their teeth, pick up items from the floor, and get around their homes using the wheelchair independently. The patient needs to have the means to complete instrumental activities of daily living as independently and effectively as possible.
Forging the Foundation for a Frame
A custom manual wheelchair is essentially built from the bottom up for the user, beginning with frame style. There are two basic frame styles for the independent manual wheelchair user: rigid and folding. Rigid frames are typically lighter weight and more durable due to the design. This type of frame is welded together versus a folding frame, which is characterized by an “x”-shaped cross brace and multiple points of physical connection joined with hardware. The rigid style chair folds for storage or transport, as the back folds down and the wheels pop off. The folding style collapses sideways. Rigid frame chairs also tend to have a smaller footprint and tighter turning radius because the front end of the chair can be brought in up to 90 degrees. The decision for frame type is dependent upon many factors including home setup, vehicle type for transport, and user preference.
Next, the team must decide on cushion type. Like the foot of a standing individual, the pelvis is the primary building block for posture and proper positioning in the sitting individual. Additionally, the cushion serves as a pressure-relieving protective surface, reducing the risk of skin breakdown. The materials utilized must be carefully considered.
Cushions: Benefits and Considerations
The primary materials utilized to fabricate cushions are variable types and densities of foam, air, fluid, or a honeycomb flexible matrix. Foam is lightweight and inexpensive, but it is known to trap heat near the body and can lose its resilience quickly over time. Viscoelastic foams accommodate slowly to the user’s weight and have memory, which delays its return to its original shape. This type of foam also has good thermal properties versus standard foam.
Air cushions can provide significant pressure relief by enveloping the user’s body and they have good resiliency; however, their effectiveness depends on the user. These cushions are high maintenance and require training in proper use and inflation levels. Additionally, air decreases the stability of the user’s pelvis and reduces the ability of the user to push off for transfers.
Fluid-filled gel cushions vary in their viscosity and subsequently vary in the degree of movement of the fluid or envelopment of the user’s body. This type of material attempts to maximize the pressure distribution, like air, but provides a more stable base. However, gel tends to be heavier than other materials. Gel is also affected by temperature and can harden in cold temperatures or soften in warmer climates. Additionally, gel may spread out under the user and reduce effectiveness of pressure distribution over time.
Honeycomb cushions are flexible enough to conform to the user’s shape, but have good ability to return to their original shape once the user transfers out of the wheelchair. Additionally, air can flow through the cushion, keeping the cushion cooler and dryer and allowing the user’s skin to breathe.
Hybrid-style cushions, which utilize multiple materials, have become popular in recent years, as they combine the pros and cons of each material, improving the overall function of the cushion. For example, a cushion combining air in the seat area, with a foam base under the legs, maximizes pressure-relieving properties over the area of the ischium for someone at increased risk of developing pressure ulcers at these boney prominences, while maintaining a stable base for the pelvis and legs, and giving the user a solid surface to push off for transfers. Cushion trials, user feedback, skin assessments, and pressure mapping systems are all valuable tools in working to make the final decision for cushion type.
Aligned for Success
Once a proper seating surface is chosen, appropriate back support is identified. There are many options for backrest types: solid, sling, or fabric. Solid backs may be planar, contoured, or custom molded. Within the sling category, there are standard fabric backs or tension-adjustable backs. Solid backs provide increased postural support, as fabric can stretch out over time, which promotes a more rounded, kyphotic position. Tension-adjustable strapping was developed to counteract this phenomenon. However, these straps are also made of fabric and can stretch out over time. Additionally, they cannot provide the same level of counter-pressure as an aluminum or plastic base. A solid back can promote improved spinal alignment, and the back angle can be reclined as needed to reduce the effects of gravity on the user with less trunk control. A planar back is flat, whereas the human body is not. A contour-style back may provide the most natural and well-distributed support.
Back height is also an important consideration for the manual wheelchair user. The back should be tall enough to allow the user to feel stable and comfortable, but, ideally, it should also leave the scapulae free for full range of motion for each propulsion stroke. Poor trunk stability or limited shoulder range of motion can lead to compensations in push mechanics and, over time, upper extremity injury. The decision about back height and material will result from many factors, including sitting balance and level of trunk control, positioning needs, and user preference.
Factors in Propulsion
Rear wheel selection is another important consideration. This is the main driving force of the chair, the chief interface between the user and the device. Wheel type dramatically impacts the user’s ability to push the chair. There are many factors to consider: type of tread, pneumatic versus solid, standard versus foldable, and hand rim style. Tread may be categorized as low tread, high tread or knobby, and no tread. Higher treads improve ability to propel over variable terrain, but also increase rolling resistance and, therefore, propulsion demand. The level of tread should be influenced by the primary environments encountered. It is possible for the user to have more than one set of wheels with different tread types to utilize in different environments.
Pneumatic tires require a comparatively high level of maintenance and can be punctured, but they provide an extremely smooth ride, absorbing some of the impact from the environment. They are lighter weight and have reduced rolling resistance than solids or tires with airless inserts, but require that the user manage a flat tire independently. New to the market are foldable wheels: these wheels can be easier to transport because they fit in smaller spaces, such as trunks or overhead bins, but they are much heavier than a standard wheel. A foldable wheel can weigh 7 to 8 pounds, which is an extra 15 pounds to be pushed around with the user. Hand rims come in both standard and ergonomic designs. Ergonomic designs should be considered to preserve hand and wrist function and can reduce the risk of overuse injury. They also can dramatically impact pain levels in a user with tendonitis or protect the fingers of someone who commonly gets fingers caught between the rim and the wheel. A plastic coating may be added to increase friction between the user and the rim.
Once the wheelchair frame, back, and cushion are selected, positioning components may be added to the wheelchair to optimize the user’s positioning in the chair. Headrests can provide support on multiple levels on the head to control lateral flexion and rotation. Lateral supports may be added to a solid back for individuals with decreased trunk control. Lumbar support may be added to a solid back to facilitate a more upright posture. Wedges or pelvic obliquity pads may be added to the cushion in order to neutralize pelvic positioning. Hip, thigh, and foot supports also may keep the user’s legs in neutral alignment.
Although individuals who require a manual wheelchair have different diagnoses, physical abilities, and seating needs, the goal is the same. The goal is to provide the individual with the best seating system to facilitate improved function, reduce medical complications that could be addressed through seating and positioning, and improve overall quality of life. RM
Erin Michael, PT, DPT, ATP/SMS, is a physical therapist and a seating and mobility specialist at the Kennedy Krieger Institute’s International Center for Spinal Cord Injury in Baltimore. She received her Doctor of Physical Therapy Degree from Ithaca College in 2006. She specializes in treating paralyzing neurological conditions, including multiple sclerosis, transverse myelitis, cerebral palsy, and traumatic brain and spinal cord injury.
Elizabeth Farrell, PT, DPT, ATP, is a senior physical therapist at the International Center for Spinal Cord Injury at Kennedy Krieger Institute. She received her Doctor of Physical Therapy degree from the University of Maryland, Baltimore, in 2007 and has a graduate certificate in the Business of Health from the Johns Hopkins University Carey Business School. Her primary interests are in seating and positioning, and pediatric applications of ABRT. For more information, contact RehabEditor@nullallied360.com.
1. Kaye HS, Kang T, LaPlante MP. University of California, San Francisco. UCSF Disability Statistic Center. Wheelchair Use in the United States. May 23, 2002. Available at: http://dsc.ucsf.edu/publication.php, Accessed January 3, 2014.
2. Cook AM, Polgar JM, Hussey SM. Cook and Hussey’s Assistive Technologies: Principles and Practice. St Louis: Mosby Elsevier; 2008.