seating system. If a client has a contoured seating system or components that are placed very specifically, these surfaces will move in relation to the client during recline (Buck, 2018). For example, the lateral chest pads will move up during recline and may end up in the client’s armpits, causing discomfort and pressure. Many clients need to have the pelvis repositioned after coming forward from a reclined position, as the pelvis may be pushed forward. Some power recline systems are designed to reduce shear forces, though some shear is always present. Knee angle The knee angle is the angle between the upper leg and lower leg. A typical seated position at a table in an office chair includes the trunk leaning forward, arms on the table, and knees bent with the feet tucked under or behind the knees. This increases stability and relieves the pull on the hamstrings. Sitting with extended knees increases the pull on the hamstrings, making it harder to flex the hips and extend the lower back, and reduces stability. The knee angle in a seating system is determined by three main criteria: footrest hangers, hamstring range of motion, and caster clearance. Most wheelchairs with swing-away leg rests offer at least three footrest hanger angles: 60°, 70°, and 90° (Figure 7). The knee angle can be further adjusted by changing where the foot is placed on the footplate. Figure 7: Footrest Hangers Note . From Sunrise Medical, n.d., retrieved from http://www. sunrisemedical.com. © Sunrise Medical (US) LLC. Reprinted with permission. This is a challenging area of positioning. Many clients have tight hamstrings. If a client has the range of motion to extend the knee past 90°, placing the knee at 90° all day will most likely lead to loss of hamstring range (Rosen, 2018). On the other hand, if the hamstring is tight, placing it near end range can elicit a stretch reflex, increasing hamstring tightness and discomfort. The client will most likely respond to this discomfort by pulling his or her feet back behind the footplates or sliding the pelvis forward into a posterior tilt, both of which relieve the pull on the hamstring. Placing the knees at 90° often leads to caster interference. The footplates frequently end up in the path of the casters, especially during turns. Some wheelchair frames are designed Position in Space Sitting for long periods of time can cause discomfort, as the tissues between the pelvis and seat have been compressed for a while and are not receiving as much blood flow. The body signals discomfort to urge the person to relieve this compression. Clients may not be able to shift their weight but do experience tissue compression that can lead to discomfort (in clients with sensation) and even pressure injuries (usually in clients without sensation). Tilt-in-space tilts the entire seating system and client forward and back in space yet does not change any of the other seated angles (seat-to- back, knee, and ankle; Figure 9). Tilt-in-space keeps the pelvis in the same position and decreases shear on the skin; repositioning is typically not needed, as in a reclining seat. Some versions even provide a slight anterior tilt, which can be useful in transfers and for some functional tasks. The client can be tilted to provide a position of rest; to manage posture (particularly trunk and head control); to facilitate feeding; and to manage comfort (Dicianno et al., 2015). This is a feature
to accommodate for this, usually by flaring the front end of the frame. Front- and midwheel-drive power wheelchairs can also accommodate a 90° knee position without caster interference. An advantage of a more closed knee angle is a smaller wheelchair footprint, improving maneuverability and accessibility (Rosen, 2018). Elevating and/or articulating leg rests allow the knee angle to be changed to accommodate different needs, including comfort. This feature is available on manual and power wheelchairs and in manual (dependent) and power (independent) versions. Elevating leg rests simply open the knee angle. Articulating leg rests open the knee angle and lengthen, so that the leg is not “pushed up” during elevation. Elevating leg rests will help circulation and edema only if the feet are raised above the level of the heart, requiring use with a full recline feature or tilt to address this goal (Jones, 2018). Make sure the client has adequate hamstring range to use elevating leg rests, especially when used without recline. Ankle angle The ankle angle is the angle between the lower leg and foot. The angle of the ankle is very interdependent with the angle of the lower leg, especially when weight-bearing, as the bottom of the foot often matches the angle of whatever it is resting against. Many clients with abnormal muscle tone or muscle weakness lose range of motion in the ankle, usually limiting dorsiflexion. Many clients with increased muscle tone demonstrate increased extension when the ankle assumes a plantar-flexed position. The angle of the ankle, if range of motion allows, can be changed by changing the angle of the footplate. Some wheelchairs offer angle- adjustable footplates. Most adjustable footplates allow the dorsi/plantar flexion angle to be changed (Figure 8). Some allow lateral (rotational) adjustment for inversion/eversion (pronation/supination) as well. If this feature is not available, wedges can be added to the footplates to achieve the desired angle. Sometimes the required angle is determined by fixed contractures or orthotics, such as ankle-foot orthoses. Figure 8: Angle-Adjustable Footplates
Note . From Sunrise Medical, n.d., retrieved from http://www. sunrisemedical.com. © Sunrise Medical (US) LLC. Reprinted with permission.
available on many manual and power wheelchairs and comes in manual (dependent) or power (independent) versions. Clients using a reclining back or tilt-in-space wheelchair require posterior head support during weight shifts to support the head against gravity. Figure 9: Tilt-in-Space Power Wheelchair
Note . From Pride Mobility Products Corp., n.d., retrieved from http://www.pridemobility.com. © Pride Mobility Products Corp. Reprinted with permission.
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Book Code: PTNC1023
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