A new method for unconstrained measurement of knee joint angle and timing in alpine skiing : Comparison of crossover and crossunder turns

Timing is an important part in the analysis of alpine skiing technique. Key events extracted from dynamics and kinematics of ski were previously proposed, but timing of body segments kinematics is also required to understand the biomechanics and to assess the performance. In this study, we proposed a new method based on inertial sensors to measure timing parameters based on body segments kinematics. To show the efficacy of the method, angle and timing of knee joints during crossover and crossunder techniques were compared. Significant differences were obtained for the timing, but not for the amplitude of the knee angles. The proposed system reported a good repeatability, did not encumber the athletes and allowed the measurement of body movement during the whole run. So it could easily be used to assess performance in training conditions.

Orientation of body segments in ski jumps using wearable sensors: Analysis of relevant parameters during stable flight phase

Kamiar Aminian, Julien Chardonnens, Julien Favre

3D kinematic and dynamic analysis is highly required in ski jumping. Current recording techniques (e.g. camera systems) suffered from limitations, such as volume capture or complexity of use and processing. This study proposed a new 3D approach based on inertial sensors to calculate automatically the whole body segments orientation of the entire jump during in-field measurements. Combination of accelerometers and gyroscopes allowed devising a functional calibration procedure adapted to ski jumping activity. Then, segments orientation was obtained based on strapdown integration of gyroscopes. Finally, accelerometers were used to define in-run initial orientations and to improve segments orientations during stable flight. In order to show the efficacy of the proposed system, relevant 3D parameters of stable flight phase (V-and attack ski angles, joint angles, drag and lift forces) were extracted from 86 jumps of 34 jumpers. Combination of these parameters expressed 55% of whole variance of distance score.

2010

Instrumented Knee Prosthesis for Force and Kinematics Measurements

Shafqat Ali, Kamiar Aminian, Arash Arami, Oguz Atasoy, Arnaud Bertsch, Catherine Dehollain, Pierre-André Farine, Willyan Hasenkamp Carreira, Brigitte Jolles-Haeberli, Eric Meurville, Philippe Renaud, Peter Ryser, Matteo Simoncini, Steve Tanner

In this work, we present the general concept of an instrumented smart knee prosthesis for in-vivo measurement of forces and kinematics. This system can be used for early monitoring of the patient after implantation and prevent possible damage to the prosthesis. The diagnosis of defects can be done by detecting the load imbalance or abnormal forces and kinematics of the prosthetic knee in function. This work is a step towards the fabrication of an instrumented system for monitoring the function of the knee in daily conditions. Studying the constraints of commercially available prostheses, we designed a minimal sensory system and required electronics to be placed in the polyethylene part of prostheses. Three magnetic sensors and a permanent magnet were chosen and configured to measure the prosthetic knee kinematics. Strain gauges were designed to measure the forces applied to the polyethylene insert. Kinematic and force measurements were validated on a mechanical knee simulator by comparing them to different reference systems. Embedded electronics, including the A/D converters and amplifier were designed to acquire and condition the measurements to wirelessly transmit them to an external unit. By considering the necessary power budget for all components, the optimum coil for remote powering was investigated. The necessary rectifier and voltage doubler for remote powering were also designed. This is the first system capable of internally measuring force and kinematics simultaneously. We propose to package the system in the polyethylene part, bringing versatility to the instrumented system developed, as the polyethylene part can be easily modified for different types of prostheses based on the same principle, without changing the prosthesis design.

Ieee-Inst Electrical Electronics Engineers Inc2013

Shoulder function and outcome evaluation after surgery using 3D inertial sensors

Brian Coley

The importance of outcome evaluation of a medical treatment in orthopedics is currently recognized. In shoulder disease, a large variety of evaluation tools is employed to assess the results of the surgery. However, even if the majority of these evaluations are largely widespread, none was accepted as a universal standard. Since 1990, few researchers have been evaluating the assumption that the movement analysis (with camera-based or electromagnetic systems) is likely to provide objective results. In clinical practice, these techniques are not always applicable for outcome evaluation of a treatment. The surgeons lack a convenient and simple method of evaluating in an objective way a patient's activity and quality of life after a surgery of the shoulder. This project provides a new tool for the objective functional evaluation of shoulder pathologies, a tool that can be easily used by a doctor at a hospital and by the patient at home. It allows the measurement of the biodynamic changes as well as 3D kinematics of the treated shoulder by noting the effects of these changes on clinical results and on the patient's daily activity. The project was split in four complementary studies. In the first study, a new ambulatory device allowing long-term monitoring of the shoulder movement using several inertial sensors (3D gyroscopes, 3D accelerometers) attached on the trunk, the humerus and the scapula's spine was designed. By combining acceleration and angular velocity features of the both humerus during 9 tests, three kinematic scores for the functional assessment of the shoulder were presented to evaluate the shoulder function in patient before and after surgery. The kinematic scores objectively showed the shoulder improvement after surgery. In the second study, a new method was proposed to detect and quantify the dominant upper-limb segment during daily activity. The method was tested on healthy subjects (N=31) and a patient group (N=10, at baseline, 3, 6 and 12 months after surgery) while carrying the system during 8 hours of their daily life. The results showed the dominance of the arm during standing, sitting and walking periods for healthy subjects and the quantification of the shoulder improvement after surgery, by taking into account the presence of the disease in the dominant or the non dominant arm. In the third study, 3D gyroscopes attached on the humerus were used to identify the movements of flexion-extension, abduction-adduction and internal/external rotation of the humerus and to identify the rates of adjunct (deliberate rotation) and conjunct rotations (inherent or automatic rotation) within each movement. The frequencies of each movement (number/hour) for the different ranges of the arm speed, as well as the rate of adjunct and conjunct rotations for each movement were estimated during daily activity in healthy and patient groups. The results provided the values of frequency of each movement and adjunct/conjunct rate based on the data obtained from the healthy group. In the pathological case, we found that the painful dominant shoulder of the patients lost its predominance in favor of the healthy shoulder, the non dominant shoulder. Patients had less pure internal/external rotations and performed less fast movements while after surgery these parameters presented no significant differences with the healthy group. In the fourth study, a new method of detecting the working level of the shoulder was presented. By measuring the arm elevation during motionless periods, we proposed a new score to evaluate the ability of working at a specific level for a definite duration. We showed that this score had an average of 100% (±31%) for healthy subjects while the working level of the painful shoulder was lower than the healthy shoulder and improved significantly after surgery (up to 87% at 6 months). This study provides preliminary evidence of the effectiveness of the proposed system in clinical practice and objectively assesses upper-limb activity during daily activity.

EPFL2007

Shoulder function and outcome evaluation after surgery using 3D inertial sensors

Brian Coley

EPFL2007

Instrumented Knee Prosthesis for Force and Kinematics Measurements

Ieee-Inst Electrical Electronics Engineers Inc2013