Wednesday, November 13, 2019
Seating and Positioning – Achieving the right posture
This week’s blog comes to you from the sky as we head to Melbourne, for Australia’s first ever Oceania Seating Symposium! We are excited to have this conference here in Australia. If you’re attending, please stop by and say hello. Rachel has two clinical presentations and we are both also presenting on the product stage. I will share a few conference highlights next week but for this week’s discussion we will continue with a seating theme.
Posterior Pelvic Tilt (PPT) and associated kyphosis are one of the most common and avoidable seating positions. When we talk about the pelvis being the foundation in sitting, we are referring to supporting the pelvis in a neutral position, but is this all about the cushion? … yes and no! The cushion can assist in maintaining a neutral position but if there is a tendency for a reducible PPT the primary point of control is the posterior aspect of the pelvis, so essentially comes from the backrest. Before we delve deeper into this point of control lets look at some common causations of PPT based on the equipment provided and how a cushion can assist or work against the goal.
Identifying some common causations of PPT
The most common causation in an equipment induced PPT is when the seat depth is too long. This is a crucial measurement. If it is longer than the femoral length (Popliteal to behind Glutes with neutral as possible pelvis) the user has no choice but to roll back into PPT to gain back support. Think about your big deep comfy couch. This is often designed with a long seat depth. Think about the functional activities we do on couch…its more about relaxation. When we sit on this deep seat length and we can’t sit back any further whilst still having our knees in a flexed position, our pelvis must roll back into a PPT for us to have contact on the backrest. The same happens in a wheelchair seat.
The other time we frequently see PPT is when we have not accommodated shortened hamstrings or reduced hip flexion. In these instances the seat to back angle and/or the hanger angle of the leg rests need to meet the users needs and postural requirements, if these do not meet the range of motion (ROM) identified within the MAT assessment of the user there is often a constant postural battle with PPT as the consequence.
As discussed earlier the seat depth is crucial and as such the cushion is also important. We need to ensure that the cushion depth and placement match the user’s measurements. When considering the product parameters of the cushion we need to pay attention to the Ischial well and ledge. In some modular cushions there are some IT adjustment options (where the ledge is located and how deep the well is) ideally you want the ledge to be just in front of the ITs to assist in reducing them from rolling back towards PPT. The depth of the well and the materials in the well also need to be considered in relation to the positioning and support requirements. Placement of a pelvic belt will also assist in supporting the pelvis and are part of the point of control solution.
So, what happens when you have an end user who has an appropriate seat depth, a reducible PPT and you have determined the ROM is appropriate. Where is the point of control to correct this positioning and support a neutral pelvis?
Just as our back is not flat, the contours of the backrest should be such that they support the end users shape and postural tendencies. In paediatric seating we may be further trying to assist in the development of the natural curves within the spine.
If the wheelchair is for occasional use, an upholstery backrest may meet the goals and needs of the user, however if the wheelchair is used for all mobility or functional tasks it is essential to consider alternatives. For some users this may mean a tension adjustable upholstery backrest which can be adjusted to provide support as required however for many a rigid backrest will be needed to provide the best support. Assessors and prescribers need to be aware of how to appropriately provide support with a rigid backrest to assist in the clinical reasoning process. For some backrests we can adjust the angle of support within the mounting bracketry and if the user has trunk innovation this may be enough. For some users, a pelvic block cut from a firm foam and placed under the backrest padding can make a significant difference. Other options have bespoke adjustments such as the Boa system within the Acta backrest, which uses a reel and cable system to provide supportive contours. If more contouring is required consideration of a customisable backrest where you can build a pelvic block into the backrest such as using the BAC system with the Dreamline backs may provide the contouring and positioning chosen. Essentially it is dependant on the degree of impairment and overall presentation on how aggressive and what type of supports are required. In all instances however we are trying to provide a rear low force that assists in pushing the pelvis from PPT towards neutral as the primary point of control and then provide opposite and equal forces to maintain using the cushion and pelvic belt.
If you want more info on seating and positioning, please contact us. We have a range of workshops to assist you in your learning goals.