Wednesday, June 16, 2021
To change or not to change. When MWD (mid-wheel drive) chairs prove challenging
A frequent conversation I’ve had in recent weeks has been around drive wheel configuration and working out what drive wheel configuration may best meet a person’s needs.
For children and people of short stature, it may not be possible to position them over the drive wheel as their thigh length is too short, meaning they sit towards the front of the chair. For this group of people, a MWD chair may feel more like a RWD chair to drive, as the drive wheel is positioned behind them, or it may be that the chair struggles to get traction on softer surfaces such as grass or gravel as the person’s bodyweight is towards the front of the chair, not down through the drive wheel. Changing to a front wheel drive can help overcome these issues and can also result in a base that has a shorter footprint which can be more in keeping with the person’s size.
For adults, their bodyweight may be focused towards the front of the chair for a couple of different reasons. If a person has shortened hamstrings, they may be positioned towards the front of the seat pan to keep their feet away from the power wheelchair base itself, meaning their pelvis is sitting in front of the drive wheel. Or it may be that the person has significant lower limb oedema and carrying extra fluid in their legs, or has extra body weight that is carried in front of them, so while their pelvis may be in line with the drive wheel, their body weight is distributed towards the front of base. In these situations, having extra bodyweight towards the front of the chair can mean the suspension on the front castors is already loaded by the person’s bodyweight, hence when the chair is used outdoors, the castors have a limited ability to move and hence road crossings can become more challenging. For some chairs they may also be more sluggish to turn on carpet, as more force is required to turn the castors which are carrying more load than intended. Changing to a FWD chair typically overcomes these issues, as the drive wheel is now positioned where the castors previously were, with the drive wheel being more suited to carry this load. As a side note, positioning a person towards the front of the seat pan can also influence how the power tilt actuator functions on some chair models, with the actuator prone to early failure if the setup is not ideal.
Not sure if one of these situations is relevant to a person you are prescribing a chair for?
Reach out to your local technician/dealer/supplier and seek a second opinion, with a front and side on photo of the person in the chair to share if possible. Getting the drive wheel configuration right for a person can make a big difference in how well a power wheelchair functions for a person, maximising their mobility and what they are able to achieve.
Clinical Education Specialist