Upper Extremity Biomechanics During Manual Wheelchair Propulsion: A Systematic Review and Analysis of Push Rim Positioning and Training Effects

Abstract

Background: Manual wheelchair use is associated with upper extremity pain and impairment, which are linked to decreased mobility and quality of life. There are a variety of methods in wheelchair fit, wheelchair design, and propulsion techniques that have the potential to help decrease the risk of injury and subsequent pain and decreased function. Existing research and new simulation studies suggest that a more anterior push rim position can help prevent shoulder injury. Based on this idea, a novel ergonomic manual wheelchair was designed and fabricated to allow for modifiable push rim positioning in an idealized position that was previously unattainable due to concerns about rearward tipping of the wheelchair. Additional strategies to protect the shoulder include using a semicircular recovery pattern during propulsion. Objectives: The objective of these studies was to determine if the anterior push rim position improves upper extremity joint biomechanics compared to the “standard” and “stable” push rim positions. Additionally, the anterior position was then combined with training in a semicircular recovery pattern to determine if the effects of the two strategies together offered additional benefit. Finally, a systematic review was conducted to determine how ergonomic assessment tools have been used in wheelchair research to this point. Methods: The design of the study was a within-subjects repeated measures design, where each subject served as their own control. The outcome measures were the joint kinematics of the shoulder, elbow, and wrist and the contact, release, and push angle on the push rim. The outcome measures were repeated across the three different push rim positions - a theorized ideal position where the push rim is anterior to the shoulder, a standard position with the push rim directly below the shoulder and a “stable” position where the push rim is behind the user’s shoulder. The data was collected using an 8-camera optical motion capture system and a stationary wheelchair simulator designed to mimic the positioning capabilities of the newly designed wheelchair. The order of the push rim positions was randomized and after two trials of 10 pushes in each of the positions were completed, the subjects were provided with visual feedback of their recovery pattern and trained to use a semicircular recovery pattern. Results: Only one of the 13 kinematic outcomes, glenohumeral internal/external rotation (p=0.001), showed evidence of an influence of push rim position by point in the propulsion cycle. In the main effects model (with no interaction term), six of the 13 kinematic outcomes were significantly different for push rim position, all of which occurred in the shoulder. The contact and release angle were significantly different between the three positions, but the push angle was not. The anterior push rim position had a higher contact angle, meaning that the participant grasped the push rim further back. However, the release angle was also higher, meaning that the push rim was released sooner. This resulted in a total push angle that did not differ significantly between the push rim positions. None of the other kinematic joint angle outcome variables were different between the two recovery patterns in either the interaction or main effects models. There were also no differences in push rim variables, so the contact, release, and push angle were all functionally the same between the two recovery patterns. Finally, the systematic review found that there was no substantive use of standardized ergonomic risk assessment tools in the manual wheelchair literature. Conclusions: The two joint angles that were statistically significantly different in the anterior position, scapulothoracic anterior tilt and glenohumeral external rotation, could be protective of the shoulder joint. The clinical practice guidelines and existing evidence suggest that the primary benefit of increasing the push angle is that it can result in decreased repetitive movements. Since that was not different between the three push rim positions nor with the addition of the semicircular recovery pattern, despite differences in the contact and release angles, the anterior push rim position and semicircular recovery pattern do not demonstrate a clear benefit over the other positions based on this metric. Despite the existence of established ergonomic principles and associated risk assessments that are relevant to repetitive tasks such as manual wheelchair propulsion, they are not being used in manual wheelchair design, set up, modification, clinical intervention, and research.