Commode Conundrum

Reprinted from PN/Paraplegia News September 2013

The study of transferring from a wheelchair to another surface.

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Transferring to places such as a bed or chair are an essential activity in daily living for wheelchair users. Those transfers are physically demanding, but trying to do a similar move in the bathroom when nature calls can be even tougher.

During transfers the combination of large shoulder angles with the vertical reaction forces used to support body weight results in a big strain on joints, tendons and ligaments. The stress load on each joint of the upper arms during transfers is larger than any other wheelchair-related weight-bearing activity.

The Right Approach

Commode transfers present a unique set of challenges for wheelchair users.

They often take place in small and constrained spaces. Little room is available to position the wheelchair for the transfer. Things don’t match up in there very well, either.

The height of the commode (17–19 inches) is lower than the average wheelchair plus cushion seat-to-floor height (22 inches) requiring a non-level height transfer for most people. Making things even tougher is that there might not even be a good spot to place the hands.

That’s why researchers at the University of Pittsburgh’s Human Engineering Research Laboratories (HERL) are investigating upper-limb and trunk movements when space limits how the wheelchair is positioned next to the commode.

The study was approved by the Department of Veterans Affairs Institutional Review Board. Six men with spinal-cord injury (ranging from T2 to L1) volunteered to participate in the study. They were all able to independently transfer themselves.

Based on the space available around the commode, two general approaches defined by the Americans with Disabilities Act (ADA) were possible: side or diagonal.

How Much Effort?

During the study, the transfer station was used to collect force data from plates and sensors.

Reflective markers were placed on anatomical landmarks of the participants’ trunk and upper extremities. A ten-camera three-dimensional motion capture system was used to collect the marker positions during transfers. That was used to calculate trunk, shoulder, elbow and wrist angles and ranges of motion.

Subjects were asked to perform the two commode transfers (side and diagonal) using their regular, everyday approaches. They were free to adjust their wheelchair orientation in each case with respect to the commode within the confines of the space available on the platform which matched the ADA recommendations.

Subjects’ peak joint angles and overall ranges of motion of the leading (e.g., hand moving to new surface) and trailing (e.g., hand left on the old surface) wrists, elbows, shoulders and trunk during transfers were analyzed.

When using the side approach, participants positioned their wheelchairs closer (an average of 3.33 inches) to the commode than the diagonal approach (an average of 7.40 inches). The angle between the wheelchair and commode was 30 degrees on average for the side approach and 108 degrees for the diagonal approach.

When performing the diagonal approach transfer, participants had larger trunk, shoulder and wrist movements and less elbow extension than the side-approach transfer.

Going Diagonal

Advantages and disadvantages were found to each approach. These were learned not only during this study but also from other studies that have investigated similar transfer techniques.

For example, the side approach requires smaller movements and less room, but means more vertical force on the shoulders, wrists, and elbows. This may increase the risk of shoulder impingement. The diagonal approach lets the larger muscle groups do most of the work but requires more room and increases the risk of falling.

All the participants in this study reported using the diagonal approach for commode transfers more often. It’s unclear exactly why they used this approach more.

It’s believed environmental factors such as (1) the amount of space available around their commodes at home, in their workplaces, etc., (2) their wheelchair type and design features and/or (3) their functional limitations and preferences all factor into the choice of approach.   

An ADA Remodel?

This study provides important information on transfer techniques and the biomechanics of transferring back and forth on a commode.

Modifying the clear space recommendations in the ADA so wheelchair users could select either approach given their level of function, preferences, and knowledge of the trade-offs for each type would better accommodate individuals who perform independent transfers.

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