DME

To pommel or not to pommel, a look at adduction points of control

To pommel or not to pommel, a look at adduction points of control

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Historically known as a Pommel or an Abductor, the new ISO terminology to describe this product parameter is a medial thigh support. This support can be independent of the seating (attached to the seat pan of the mobility base) or built into the cushion through the contours of the cushion itself.

Abduction and adduction of the hip joint are a continuum; neutral positioning is when the knee joint and hip bones are in line and symmetrical. If the knee is medial (Knees together touching) the hip joint is adducted. If the knee joint is lateral to the hip joint (Knees apart), the hip is abducted.

 

 

We frequently refer to the sitting position being as neutral as possible and we know if the wheelchair is too wide this has a negative impact on the shoulder joint for self-propulsion. So why do we use medial thigh supports in seating? When do we consider its use? What are the disadvantages of this type of support? We also know that the larger the base of support the more stability gained, abduction increases our seated base of support thus can be a preferred position. Body dimensions may also require a more abducted seated position, so why not sit everyone abducted?

In addition to forcing self-propulsion from a vulnerable position (in shoulder abduction), the increase in the width of the seating may also decrease accessibility in some environments. The clinical reasoning process needs to consider the hip ranges of motion established in a MAT assessment, tone patterns, proximal stability of the pelvis, and users’ functional goals to determine the seating parameters. What kind of supports are required based on the capacity of someone to gain functional support and stability?

 

                                  Abduction                                                             Adduction

                                                                                     

  

 

 

 

 

 

 

 

 

 

 

 

 

If a femur is positioned in more abduction than there is passive range, the impact on the pelvis will be seen with the pelvis rotating in the same direction to enable the femoral position.  This is commonly seen when a non-reducible wind sweeping position is not accommodated. Wind sweeping is the tendency for both limbs to sweep to one side – one hip will be abducted and the other adducted.

Longitudinal hip surveillance studies have provided us invaluable information on hip migration, causations, high risk group identification and resulted in guidelines such as https://www.ausacpdm.org.au/wp-content/uploads/2017/05/2014-Aus-Hip-Surv-Guidelines_booklet_WEB.pdf - which is an excellent resource.

 

 

 

The resource explains “Progressive displacement can result in asymmetric pressure that may deform the femoral head and or acetabulum (also termed acetabular dysplasia). Hip dysplasia may lead to degeneration of articular cartilage and pain25. Problems with limited range of movement and pain can interfere with function, ability to be positioned, hygiene and personal care. In a large subset of children the progressive displacement can develop into dislocation of one or both hips (Cooke et al, 1989).”

For anyone working or caring for young children with Cerebral Palsy and mobility impairment, potential risk groups have been identified and are encouraged to be referred to a hip surveillance program. Seating positioning recommendations for these children is likely to include some abduction for either chair or bed positioning.

One thing a pommel is not is a load bearing surface or a safety stop! When someone does not have the hip flexion ranges to sit with the hips bent at 90 degrees they are likely to “slide” out of the seating as they try to open their hip angle to meet the seat-to-back angle of the seating. I have been involved in cases like this where the support people then ask us to make the seat more ramped – based on the anti-thrust seat concept they may have had as a child or seen others utilising. If they do not have the range to sit in a 90 degree seat-to-back angle, raising the front of the cushion will only make it more difficult to maintain a flexed hip. They will continue to attempt to open this angle by sliding into posterior pelvic tilt (PPT) – see my previous blog for more on that.

If there is a pommel fitted this is often all that is holding the individual in the seating if they don’t have the capacity to bend their hips enough. When doing custom seating I would often have support workers or carers asking for this pommel to be larger as it stopped the user from sliding out. If we are prescribing AT, It is part of our job as a therapist to be able to articulate and educate what the points of control are and how they can benefit someone’s positioning and ultimately their function.

 

             A Dreamline Swing-Down Abductor Pommel

So, what is a pommel? What point of control is it addressing? The purpose of a pommel or leg troughs in a cushion are solely intended to reduce the level of adduction. The ongoing implication for adduction includes instability, increased difficulties with personal care and hygiene tasks, increased pressure risk at the knees and of significant concern, increased risk of posterior hip dislocation especially for those individuals who have never had opportunity of the hip fossa fully developing through walking and weight bearing.

When considering a pommel or a support to decrease adduction, there are several factors to consider. Should it be integrated into the cushion? This is likely to be determined by factors such as transfer style. Should it be removable? What environments is the user in requiring support? Can the support workers easily fit and remove it as required? How high is it? Generally, it does not need to protrude above the user’s thighs. What angulation can be achieved? Can it be adjusted for ongoing needs?

Do you want to know more about product parameters, MAT or functional seated positioning? Permobil offer a range of workshops including practical hands-on learning opportunities, blogs, workshops and webinars. Don’t hesitate to reach out to us for further information! Follow our blog to be the first to find out more details on our 2020 training opportunities which will be released very shortly!

 

Tracee-lee Maginnity

 

 

 

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