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Actuators for Wheelchairs

Changing position for function, comfort and safety.

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Clients who use wheelchair seating systems are often unable to change their position at all. Most wheelchair seating systems are static. The consumer is supported in one position unless he or she moves out of alignment with the support surfaces. This can lead to discomfort, pressure sores and other complications.

Actuators provide a means to change position, either by changing the client's position in space or changing his body angles. For example, a tilt actuator changes the position of the person in space, while a recline actuator changes the seat-to-back angle. Other actuators include elevating legrests, seat elevators and standers.

Actuators can be manual or powered. Manual actuators usually require caregiver control. Power tilt is available on some manual wheelchairs to allow independent control of tilt, despite the lack of independent mobility. Newer power-wheelchair electronics can be programmed to activate a specific sequence of actuators with one command. For example, the chair can be programmed to recline back 45 degrees, tilt back 15 degrees and elevate the legrests 20 degrees. Some electronics also include a reminder for the client to perform these weight shifts according to a programmable schedule.

Actuators provide positional changes that can remediate posture, improve comfort and sitting tolerance, address medical issues, facilitate functional tasks and reduce pressure sore risk. A critical part of a seating and mobility evaluation is determining if actuators are indicated, and which one(s).

Tilt
Tilt systems, also called tilt-in-space, shift the entire seating system forward and back in space; the angles at the ankles, knees and hips remain unchanged. Tilting rearward shifts some of the weight off the buttocks and thighs and onto the back. Anterior tilt tips the client forward; this is used in certain positioning strategies and can be used to assist with transfers.

Tilt systems often tilt rearward about 55 degrees, as this amount has been shown to provide the most beneficial pressure relief. Many clients may not tolerate this position; however, more frequent, smaller-degree tilts can also be effective.

More recently, center-of-gravity tilts have come to market. These tilt systems are less tippy, have a smaller "footprint" and make it easier for caregivers to bring a heavier client to an upright position.

Pros:

  • Enables pressure redistribution
  • Enhances comfort, resulting in increased sitting tolerance
  • Provides a position of rest to address fatigue
  • Allows gravity to assist with trunk and head control
  • May provide an improved position for swallow, visual regard or functional tasks
  • Accommodates one-piece seating systems and does not create shear forces, as the seating angles do not change
  • Can be used following a seizure to manage posture and fatigue

Cons:

  • Must move away from table or desk before tilting
  • Items on a tray may slide toward user
  • Leg bags may leak during tilt

Recline
Recline systems increase the seat-to-back angle so that the trunk is leaning back. Reclines are often combined with other technologies, such as a low-shear back, tilt or elevating legrests.

One issue with reclines systems is shear. Think about the last time you went to the dentist. You sat in the chair with your head on that little pillow. Then the dentist leaned you back (recline) and your head fell off the pillow. You probably had to scoot up to get back in position. That is shear. Without a low-shear back, seating components that are aligned with the client in an upright position do not remain so after a recline. Shear also causes friction on the body and can contribute to pressure sores. Some recline systems claim to have "no shear," but all have at least a minimal amount.

As with tilt, recline offers pressure redistribution, additional comfort and a position of rest. A reclined position may work better for some clients for swallow, visual regard or functional tasks. Recline can also enhance postural and fatigue management post-seizure.

Additional pros include:

  • May ease tasks, such as catheterization, accessing a G-tube, diapering and changing clothes, due to the open seat-to-back angle
  • Provides passive range of motion at the hips
  • Can be used to address orthostatic hypotension and autonomic dysreflexia

Cons:

  • Shear
  • Cannot be used with one-piece seating systems, including many molded systems
  • Opening the seat-to-back angle may elicit extensor tone, particularly in the hips
  • Opening the seat-to-back angle may lead to a loss of seated position, making returning to upright more difficult

Combination Systems
Combination tilt/recline systems are typically used for several specific applications. First, combining a tilt and recline provides better pressure distribution and relief than use of either system alone. Another advantage of combining the systems is that the tilt portion can prevent the loss of position that tends to occur when using recline. After reclining back, the client then executes a partial tilt before reclining forward. This tends to keep the pelvis from sliding forward.

Elevating Legrests
Opening the seat-to-back angle without increasing knee extension may be uncomfortable, so elevating legrests (ELRs) are typically ordered with a recline system. Articulating legrests increase knee extension and also lengthen so the leg isn't "jammed" during knee extension. ELRs may be mounted at midline (typically allowing the knees to start at 90 degrees flexion, often seen on power chairs with front- or mid-wheel drive) or in a more typical footrest hanger style.

Elevating legrests are most commonly recommended to reduce edema in the lower extremities; however, they are ineffective for this use. Unless the feet are raised above the heart, elevating the legs will have little effect. Tilting back fully can impact edema, as can a full recline with full knee extension, providing the client has adequate range of motion.

Elevated legrests provide passive stretch to the hamstrings, which can be beneficial or detrimental. Many clients simply do not have the range of motion in the hamstrings for this degree of knee extension. Extending the knee pulls on the hamstring and, if there is insufficient range of motion, the pelvis is pulled forward into a posterior pelvic tilt.

Seat Elevators
Seat elevators do exactly that: elevate the seating system. The seated angles do not change, but the entire system elevates up to 10 inches or more. This can have numerous advantages, including extending functional reach, changing seat height to accommodate various work surfaces and assisting with transfers.

Elevators can be beneficial for social interaction and to see over obstacles, but these justifications are not seen as a medical need. Seat elevators are very difficult to fund. Some power wheelchairs include seat elevators so separate funding is not required. RESNA's position paper on seat elevators can be very helpful in justifying funding (available at www.resna.org).

Standing
Some manual and power wheelchairs include a stander as a part of the frame. Standing in the wheelchair extends functional reach and enables the client to interact with others at eye level and see over obstacles. Clients who have standers as a part of their wheelchairs are more likely to stand on a regular basis than clients who rely on a stationary stander.

The main clinical drawbacks for standers are that some clients do not have adequate range of motion to stand or are not medically cleared for standing, indicating that the client may be at risk for a fracture or autonomic issues.

Other Actuators
Manufacturers have developed numerous other specialty actuators.

Lateral tilt is one that has some interesting applications. Occasionally, I run into a client who needs the ability to shift his weight to prevent pressure-sore development, but cannot tolerate leaning back (often due to reflex activity). However, this same client may be able to tolerate side-to-side weight shifts, which lateral tilt can provide.

Another type of specialty actuator lowers a platform to the ground in the same location as the footrests. The client can scoot onto this platform and then raise the platform to the level of the seat, allowing him to scoot into the seat itself. This actuator allows independent transfers from the floor for some clients.

Funding for Actuators
Funding is always a challenge in the seating and mobility world, and it seemingly gets tougher every day. When recommending actuators, I often refer to RESNA's position papers or even include relevant copies of them with my evaluation report. They are available online for free at www.resna.org. Each position paper includes a summary of clinical indicators for each technology and a very comprehensive listing of current research supporting that clinical information.

Funding sources may view actuators as "luxuries," but when an actuator is the best option for a client's needs, I encourage you to fight for funding. If enough clinicians keep pursuing funding for a specific technology, funding will eventually improve.

Michelle L. Lange, OTR, ABDA, ATP, is owner of Access to Independence in Arvada, CO. She has 20 years' experience working with assistive technology. A past secretary of RESNA, she can be reached at MichelleLange@msn.com or visit her Web site at www.atilange.com.

Related Content
To learn more about treating individuals with disabilities, visit our Disabilities & Conditions Specialty Spotlight.


 

I am a c5 quadriplegic I use a front wheel drive chair and the tilt actuator has went out on it and will not allow me to tilt backward to do my weight shifts.


Jake June 18, 2014
Alton, IL



I am very impressed the content. I believe you really have a hold on these actuators.

Joe September 10, 2010




     

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