Abstract: Motion analysis allows for the collection and quantification of movement, and has long been used for the assessment of gait. In more recent years, models have been developed to accurately track the kinematics of the upper extremity, however, current methods are limited due to the small number of validated kinematic models. Over time, multiple models have developed for shoulder joint center (SJC) calculation, however, few are validated, with most difficult to implement. Currently, approximately 3.7 million wheelchair users reside in the USA. The repetitive cyclic propulsion pattern required for wheelchair mobility places high loads on the wrist, elbow, and shoulder and often results in overuse injuries with an estimated 30% to 69% prevalence. Quantification of the shoulder complex using 3D kinematics allows for the assessment of ranges of motion, forces, and moments which may allow for better prescription and training, and propulsion biomechanics in wheelchair users. Schnorenberg et al. developed and validated a wheelchair model whereby the SJC was calculated using multiple linear regression of the positions of the scapula, clavicle, and humerus. While this model more accurately tracks the glenohumeral joint center as compared to previous models, it requires advanced training and custom Matlab code which limit application for adoption by low resourced clinics and facilities. A simplified model using Visual 3D was developed to allow for local and international clinical and research applications in conjunction with a previously develop low-cost motion tracking system. Motion data during the wheelchair stroke cycle, was obtained using 12 Vicon cameras and Vicon Nexus software. The 3D motion files were processed using both models. The wrist joint center and glenohumeral joint center yielded sub 2 mm mean error. While the wrist, elbow, and glenohumeral joints had an average error of less than 10° during the grasp and vertical events. Through the development and validation of a simplified model utilizing Visual3D, upper extremity motion analysis may be easily applied in international and outreach clinics. This work presents new methodology to augment current paradigms for evaluation of wheelchair biomechanics.
Keywords: Manual wheelchair users,Motion analysis,Scapular modeling,Upper extremity, Visual 3D