Off-the-shelf seating works well for the majority of people who use wheelchairs; however, there are some people who require either customization of off-the-shelf seating or, for those who have more complex needs, custom seating systems. This month, I will discuss some of the modifications that are available in off-the-shelf seating that address skin protection, positioning needs, or personal choice. Some modifications can be done by a therapist in the field. For example, closed cell foam can be carved using an electric carving knife. If done at the factory, many of the customizations involve no additional charge, but to be sure, check the order form. If the customization is not listed on the order form, it does not necessarily mean it is not possible – it may simply mean it is not a frequently requested modification. Checking with the customization department of the manufacturer will give you all the information you need about possibilities and prices.
Fluid is a material known for its skin protection qualities in wheelchair cushions. Fluid is held within a segmented container, or a pack, within a contoured foam cushion base. The fluid allows for immersion of the pelvis into the pressure relieving material, while the cushion design allows for redistributing load to the femurs and possibly the trochanters. (Click for more information on cushion design and on cushion materials, respectively.)
A modification to the fluid level may be requested. This will affect the position of the pelvis within the well and the relative load distribution through the femurs. For example, a person with muscle atrophy at the buttocks may benefit from an “overfill” of the fluid volume to prevent “bottoming out”. In this case, the additional fluid volume represents a replacement for the tissue the person may be lacking. The additional fluid volume prevents “bottoming out” (providing adequate maintenance is completed with the fluid pack) and helps to ensure that the load is distributed evenly through the length of the femurs along the foam base.
On the opposite end of the spectrum, a person with a lot of excess adipose tissue at the buttocks may benefit from an “underfill” of fluid volume if the femurs are not fully supported on the foam base. Without an underfill in this example, the person with excess tissue may be perched “on top” of the well with loading through the distal aspect of the femurs. An underfill for a person with excess adipose tissue at the buttocks may facilitate optimal pelvic immersion into the well of the cushion and optimal pressure distribution through the length of the femurs.
Another modification to a fluid pack to affect skin protection is to request a heat seal to prevent fluid migration between segments. Fluid packs are segmented to reduce surface tension and enable optimal immersion into the fluid; however, migration of fluid between segments can occur. To control fluid migration, a heat seal can be made on the area at risk for skin breakdown, such as the sacral area.
Backrests, or back supports, also can be modified to address skin protection needs. A spinal fluid pack can be inserted into a foam back support, over the spinal area, to reduce pressure along the bony prominences of the spine. Another modification that can be done to a back support is to add a layer of Visco-elastic foam to the supportive foam. Visco-elastic foam not only adds comfort to a back support, but also facilitates envelopment of the bony prominences to create greater surface contact area, which helps to decrease pressure.
In addition, modifications can be made to fluid volume to affect positioning in a fluid/foam combination cushion. A pelvic obliquity can be addressed by requesting either an overfill or an underfill on either the right or left side of the fluid pack. For example, if a person has a flexible, right-sided pelvic obliquity (i.e., right ischial tuberosity is lower than left ischial tuberosity) and the person can tolerate correction, either an overfill on the right side of the fluid pad or an underfill on the left side of the fluid pad can be requested to bring the pelvis to a neutral position.
Numerous modifications can be made to foam cushions or bases to facilitate positioning for an individual. Foam can either be removed from, or added to, the cushion or base. For example, a leg length cut can be made to either the right or left side of the cushion to accommodate a leg length discrepancy. This can be done either in the field or in the factory. A foam base that has a pre-contoured medial thigh support can have the medial support removed to accommodate a person that presents with a fixed windswept posture. The lateral edges of a cushion can be notched on the undersurface of the cushion for seat rails to position the cushion lower to the floor between the seat rails to achieve a lower seat-to-floor height. For many cushions, a drop base can be added to the cushion, again, to achieve a lower seat-to-floor height, which may be required for transfers or foot propulsion.
A cushion can be modified to have anterior slope either by requesting an angle cut on the foam base or by requesting the addition of a foam wedge to the cushion. The same is true for the addition of a posterior slope on a cushion. An anterior slope opens the seat-to-back angle, which may benefit a person who has limited hip flexion. A posterior slope closes the seat-to-back angle, which can help with positioning for some people. Closing the seat to back angle can make it more difficult to transfer from the wheelchair and can increase the pressure through the ischial tuberosities so clinical consideration must be used when making this choice.
Positioning pieces also can be added to a closed-cell foam base. Positioning pieces include medial thigh support (i.e., “adductor”), lateral thigh support (i.e., abductor) and lateral pelvic support (i.e., “hip guide”), which come in a variety of heights to meet positioning needs.
Back supports come in a variety of contours and heights to meet positioning needs. If greater lateral support is required than is provided through the design of the shell, fixed or swing-away lateral supports can be added to the backrest. Like with the positioning pieces described for cushions, lateral supports come in a variety of sizes to meet the unique needs of individuals.
Modifications to Covers
Covers can be modified to meet a number of different needs. Covers can be customized to match positioning needs if the cushion modification was done at the factory. For example, if a cushion has a cut out for a leg length discrepancy, the cover can be sewn to match so that there is no excess material causing pressure. Cover material can be chosen to address skin protection needs. For example, a stretch cover can be chosen to allow for optimal immersion into a cushion well or a micro-climatic cover can be chosen if heat and moisture dissipation are required to facilitate skin protection. In addition, the newer style of inner incontinent cover (four-way stretch fabric with anti-wicking thread and inverse coil zipper) can be customized to many models of cushions and back supports, not only for those for which it was originally designed.
Covers, whether for cushions or for back supports, can be modified to reflect personal choice. Colour selection of the sideband of the cover is available on some cushions. This is popular with children! The shell of some back supports can be painted at the factory to provide a custom look to the seating. In addition, another back support offers some choice in the material that covers the posterior aspect of the backrest.
This month, I have mentioned only some of the common customizations in cushions and back supports. When looking at customization, the limit is only your imagination... and engineering possibilities!