Biomechanical modeling and analysis of manual wheelchair propulsion

Users of manual wheelchairs depend on wheelchairs for most of their daily activities. Manual Wheelchair Propulsion (MWP) is an inefficient and physically straining process, which in the long term can cause injury. However, wheelchair users do benefit greatly from cardiovascular exercise with the use of manual wheelchairs. The first step in improving the low efficiency and/or preventing injuries during MWP is to be able to measure these factors. To do this, we have proposed an Equivalent Biomedical Index (EBI) and two Wheelchair Users' Joint Injury Indices (WUJII and WUJII') for gross mechanical efficiency and injury assessments. We have fabricated and validated an instrumented wheel to measure the user's applied loads on the handrim during MWP as part of the data required for calculating the proposed indices. The wheel system has been verified by using general uncertainty analysis, and its specifications have been determined using both static and dynamic experiments. The results have ensured the reliability of the system. Also, a procedure has been developed to determine the angular position of the contact point between the hand and the handrim by using the applied loads and without the use of cameras. This study also focuses on proposing a novel method to determine the optimum seat position of the wheelchair to minimize the values of the injury indices and/or maximize the value of EBI for each user. Eight male wheelchair user subjects were recruited for the experiments. Statistical analysis showed that horizontal seat position was significantly related to all three indices (p <0.05). The response surfaces of the indices for two users were determined by using the proposed method and a Bivariate Quadratic Function. We developed and elaborated "Method I" for analysis of the dynamics of user joints and to calculate the joint loads as part of the factors required to define the optimum seat position. A 3D rigid-body inverse dynamic method was used to calculate the joint loads. "Method II" for analysis of the kinetics of the upper limbs was developed and validated to simplify the experimental procedure and decrease the required post-processing. Method II showed to be reliable for measuring the joint forces.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat

Design and Fabrication of an Instrumented Handrim to Measure the Kinetic and Kinematic Information by the Hand of User for 3D Analysis of Manual Wheelchair Propulsion Dynamics

The repetitious nature of propelling a wheelchair has been associated with the high incidence of injury among manual wheelchair users (MWUs), mainly in the shoulder, elbow and wrist. Recent literature has found a link between handrim biomechanics and risk of injury to the upper extremity. The valid measurement of three-dimensional net joint forces and torques, however, can lead to a better understanding of the mechanisms of injury, the development of prevention techniques, and the reduction of serious injuries to the joints. In this project, an instrumented wheel system was developed to measure the applied loads dynamically by the hand of the user and the angular position of the wheelchair user′s hand on the handrim during the propulsion phase. The system is composed of an experimental six-axis load cell, and a wireless eight channel data logger mounted on a wheel hub. The angular position of the wheel is measured by an absolute magnetic encoder. The angular position of the wheelchair user′s hand on the handrim during the propulsion phase (ɸ) or point of force application (PFA) is calculated by means of a new-experimental method using 36 pairs of infrared emitter/receiver diodes mounted around the handrim. In this regard, the observed data extracted from an inexperienced able-bodied subject pushed a wheelchair with the instrumented handrim are presented to show the output behavior of the instrumented handrim. The recorded forces and torques were in agreement with previously reported magnitudes. However, this paper can provide readers with some technical insights into possible solutions for measuring the manual wheelchair propulsion biomechanical data

Knee Kinematic Improvement After Total Knee Replacement Using a Simplified Quantitative Gait Analysis Method

Objectives: The aim of this study was to extract suitable spatiotemporal and kinematic parameters to determine how Total Knee Replacement (TKR) alters patients&rsquo; knee kinematics during gait, using a rapid and simplified quantitative two-dimensional gait analysis procedure. Methods: Two-dimensional kinematic gait pattern of 10 participants were collected before and after the TKR surgery, using a 60 Hz camcorder in sagittal plane. Then, the kinematic parameters were extracted using the gait data. A student t-test was used to compare the group-average of spatiotemporal and peak kinematic characteristics in the sagittal plane. The knee condition was also evaluated using the Oxford Knee Score (OKS) Questionnaire to ensure thateach subject was placed in the right group. Results: The results showed a significant improvement in knee flexion during stance and swing phases after TKR surgery. The walking speed was increased as a result of stride length and cadence improvement, but this increment was not statistically significant. Both post-TKR and control groups showed an increment in spatiotemporal and peak kinematic characteristics between comfortable and fast walking speeds. Discussion: The objective kinematic parameters extracted from 2D gait data were able to show significant improvements of the knee joint after TKR surgery. The patients with TKR surgery were also able to improve their knee kinematics during fast walking speed equal to the control group. These results provide a good insight into the capabilities of the presented method to evaluate knee functionality before and after TKR surgery and to define a more effective rehabilitation program

Biomechanical Analysis of Tapered Integrated Screw and Sensitivity Analysis on Abutment Loosening in Dental Implants

Background and Aims: Different mechanisms have been developed for connecting abutment to implant. One of the most popular mechanisms is Tapered Integrated Screw (TIS), which is a Tapered Interference Fit (TIF) with a screw integrated at the bottom of that. The aim of this study was to investigate the mechanism of TIS and effective factors in employing TIS during design and implementation processes using an analytic method.Materials and Methods: Relevant equations were developed to predict tightening and loosening torques, contactpressure and preloads with and without bone tissue in this analysis. The efficiency is defined as the ratio of the loosening torque to the tightening torque. The effects of the change in elastic modulus and thickness of the bone on operation of this mechanism were investigated.Results: In this study, 14 independent parameters such as taper angle, friction coefficient, abutment and implantgeometry that are effective on performance of TIS mechanism were presented. The role of some factors was shown in the performance of ITI implant using sensitivity analysis.Conclusion: It was shown that friction coefficient, contact length, and implant radius play major roles on tightening and loosening torques and efficiency of the mechanism. Furthermore, the results revealed that the change in the elastic modulus and thickness of the bone influenced the efficiency of the mechanism less than 15%