What You Should Know About Wheelchair Elevating Leg-Rests

What You Should Know About Wheelchair Elevating Leg-Rests     

Most wheelchairs have a number of items that are adjustable and that can be aligned, as well, for comfort and convenience. These rests are used to elevate the legs placing them in extended, knee-straight positions with “calf-pads” that are either padded or covered with a hard, plastic material. Foot-plates and calf-pads can be adjusted for improved alignment and foot-placement, as well. Some of these devices have an articulating feature that allows them to be extended and become longer as the leg is elevated. Usually, they are ordered for the control of foot and/or leg edema (swelling).

PROS

·        The leg-rests keep the leg extended for those who have limited knee-flexion (knee fixed in a straight-position) or for those who require this position, that is, after an operation.

·        On a chair with a powered recline-system, powered these elevating rests are useful in help-ing a user into the supine-position (lying on one’s back) or into the reclining position.   

·        Sometimes, changing the leg-positions is helpful in resolving discomfort or pain in the lower extremities.

CONS

·        The leg-rests increase the weight of the wheelchair as well as increase the cost.

·        They have a number of moving parts that may “lock-up” or become difficult to manipu-late, but rarely.

·        A certain amount of co-ordination and strength is required to operate these leg-rests, without assistance. (At the same time, the user must bend over to one side, depress a lever and lift the leg.)  

·        The extent of edema-control (swelling) is questionably a benefit since the extremity is nowhere near the level of the user’s heart, even with the elevated height.  

·        Elevating the leg may result in a somewhat flexing-of-the-knee depending on the length of the user’s leg.

·        When the leg is elevated, it makes the chair longer resulting in the need for an increase in “turning-radius” and space and possibly, a re-positioning of the legs and hips.

·        The elevating rests, after a period of time, may become warped or worn from the weight of supporting the legs and may become “abducted” (away from each other) result-ing in poor positioning of the legs and hips.

• The leg-supporting pad, an integral part of the leg-rest, may push against the user's calf, pulling the user forward on the seat, resulting in a slouched position and/or result in some pain with the sciatic (tailbone) nerve.
• At the highest-point of the rest is a “joint” that has a tendency to rub on the outside of the user's leg.

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What You Should Know About Wheelchair Camber

What You Should Know About Wheelchair Camber              

Camber is the angle made by the wheels of the chair. It is the angle between the vertical axis of the rear-wheels and the vertical axis of the chair when viewed from the front or rear of the chair. It is used in the design of steering and suspension. If the bottom of the wheel is farther out than the top (away from the axle), it is called negative camber. Tilted-rear-wheels, a popular feature on racing wheelchairs is being seen more and more on wheelchairs that are used for activities of daily living. One of the advantages of camber is that it provides better lateral (sideways) static stability for the wheelchair as a result of the greater distance between the low, bottom-points of the two wheels. This is especially advantageous when frequent sideways movements are needed as in wheelchair basketball. It can be described as an angling that brings the top of the two, major drive- wheels closer to each other.

In a study conducted in Holland, eight non-impaired wheelchair users participated in an exercise (test) using a motor-driven treadmill in order to study the effects of rear-wheel camber on wheel-chair movement for six shoulder muscles which was the major part of the study. The test consisted of four runs with rear wheels at 0°, 3°, 6° and 9°-degrees camber and at speeds of 2, 3, 4 and 5 km/hr. There were no significant changes and/or results on oxygen-usage, heart-rate or mechanical efficiency.

Camber angle alters the handling qualities of the suspension design; negative camber improves the grip when cornering. This is because it places the tire at a more optimal angle to the road, transmitting the forces through the vertical plane of the tire, rather than through a force across it. Another reason for negative camber is that a tire tends to roll on itself while cornering. If the tire had zero camber, the inside edge of the contact point would begin to lift off the ground, thereby reducing the area of contact. By applying negative camber, this effect is reduced, maximizing the contact point. Note that this is only true for the outside tire during the turn; the inside tire would benefit most from positive camber.

On the other hand, for maximum straight-line acceleration, the greatest traction is attained when the camber angle is zero and the tread is flat on the road. Proper management of the camber angle is a major factor in suspension design and must incorporate not only geometric models but also, real-life behavior of components such as flexing, distortion, elasticity, etc. What was once an “art” in design is now become a more exact and scientific technique through the use of the computer. They can optimize ALL of the variables, mathematically, instead of relying on the experiences and intuitive estimations of engineers. As a result, the improved handling of wheelchairs has been dramatic in recent years.  

However, excessive camber angle can lead to increased tire wear and impaired handling. As camber is increased, the width of the wheelchair across the bottom increases. This adds lateral-stability to the system by increasing the wheelchair footprint. If too much camber is added, there may be a problem getting through doorways.  The amount of camber required for ordinary, daily use is not the same as that that is required for wheelchair sports. The amount of camber introduced is measured in degrees where the higher the number, the more camber or angling. Some more expensive models of wheelchairs have methods of adjusting the camber.

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Besides the greater stability of cambered wheelchairs, cambered rear-wheels provide an easier reach to the hand-rims and less hampered arm movements during push-and-recovery movement leading to a less strenuous propulsion technique. Thus, camber would be more efficient with less arm spreading and stabilization. A study on chair characteristics during the 1980 Paralympics showed a trend of increased success of the athlete with increasing camber. The most successful athletes had wheelchairs with a camber.

Off-road vehicles such as agricultural tractors generally use positive camber. In such vehicles, the positive camber-angle helps to achieve a lower steering effort. Also, some single-engine aircraft that are primarily meant to operate from unimproved surfaces such as bush-planes and crop-dusters have their main wheels equipped with positive-cambered wheels to better handle the de-flection of the landing gear as the aircraft settles on rough, unpaved airstrips.

Caster is the tilting of the steering-axis either forward or backward when viewed from the side of the chair. A backward tilt is positive and a forward tilt is negative.  Caster influences directional control of the steering (in an automobile) but does not affect the tire- wear and is not adjustable. On an auto-mobile, caster is affected by the vehicle height. Overloading the vehicle or a weak or sagging rear spring will affect caster. Since we are talking about a wheelchair, caster does not come into play.

PROS

      

• Lateral stability is increased with a wider footprint by having a camber greater than zero.                
• The ride is softer with a camber greater than zero.
• The push-rims are placed in a more positive position for pushing with a camber angle greater than zero since it is more natural to push down and outward.
• The hands are more protected when pushing in tight areas since the bottom of the wheels will make contact first with walls and door-frames.
• The strain on the shoulders is diminished since the plane of the wheel is closer to that of the shoulder.
• Turns are made quicker.
• The wheelchair is given a sportier look.

CONS

• The wheelchair is made to be wider by angling the wheels at the bottom.
• The cost of the chair is increased.
• The wheels may rub against the armrest(s), against the side-panels or the user due to an excessive camber angle.      

• Traction may be diminished and wear on the tires, uneven, by comparison to a conventional tire.

NOTE: A conventional tire has treads placed in the center of the tire. Cambered tires ride on the inside edges of the tire. To compensate for cambering, some manufacturers make their tires with offset treads.

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What You Should Know About Wheelchair Lateral-Supports

What You Should Know About Wheelchair Lateral-Supports

Lateral trunk supports, are also known as laterals, lateral-supports, lateral-thoracic-supports, trunk-stabilizers or just plain wheelchair stabilizers. They are rectangular-shaped devices that mount to the back-posts of a wheelchair and rest against the user's trunk. Often, they are used in pairs, one on each side of the trunk. The main-purpose for them is to eliminate the “side-to-side” rocking of the chair and lateral leaning. They are part of the wheelchair positioning accessories that provide a comfortable, convenient armrest to facilitate arm-use and rehabilitation.

These supports come in a number of different sizes and padding densities. Size and shape will vary depending on the manufacturer and style. The most common styles are planar (flat) or contoured (shaped). The amount of “contouring” (shaping, fitting) may vary between styles and manufacturers. Many models can be ordered with hardware that allows these supports to “swing-away” from the user and out-of-the-way. This makes getting in-and-out of the chair much easier. They are available from the wheelchair manufacturer or can be purchased from a number of aftermarket sources.

These positioning accessories are most often used to increase the user's trunk-stability and balance. These supports are often used in an effort to control “spinal-scoliosis” ("S-shaped” curvature of the spine). This tactic may work in those cases were the scoliosis is flexible and can easily be reduced. In cases where the scoliosis is rigid, these supports may cause discomfort as well as some tissue damage (wounds). This is especially true if the support is placed on the apex (high-point) of the spinal curvature.

If the user’s trunk can be placed in an upright, neutral, sitting-position but the user cannot maintain this position, the supports can be placed opposite one another, on each side of the trunk. This technique adds the needed external support to hold the user in position. Many users and professionals think that these supports must be placed exactly opposite each other on the trunk. This is not true and, in certain cases, may result in poor performance results and extreme discomfort

to the user.

In those cases where spinal curvature is present, uneven or oblique placement of the supports must be considered. One lateral should be placed just under the apex of the spinal curve. The second lateral should be placed on the opposite side

of the trunk and above the opposing one. This initiates the proper dynamics for reducing the curve (if flexible) and gives

the proper support to the trunk.

In order to work well, these devices must be in contact with the user’s trunk. If they do not make contact, support is not possible. If they are too tight, the user may have a problem with breathing. If they are placed too low, the support is lost and the trunk may "lean" over the supports. If placed too high, they may impinge on the armpit and cause damage to the nerve fibers from the spine to the neck and arm, irritate the surrounding skin and restrict shoulder and arm movement.

             

              PROS

                                                                              

• Aids in trunk support and stability.                               

• Improves balance and posture.                                      

• Helps maintain the user in a functional position.           .

• Prevents further postural decay.                                    

• Diminishes the need for repetitive repositioning of the user during the day.                                               

• Improves appearance.                                                                                                                                  .

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                CONS

                                                                           

• If placed too low, they are ineffective.

• If placed too high, they may irritate the armpit, spinal nerves, surrounding tissue limiting shoulder and arm movement.

• May be difficult to mount to the “back-rest” in the proper location.

• When the pad is under pressure, the “swing-away” feature   may become difficult to operate.

• Contact of the entire pad against the body is difficult to position since there are no adjustments for angling the pad in or out.

• If the user changes position, the supports will now, most likely, not be aligned, correctly, any more. In addition, they add another layer of complexity to the entire chair.

   

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