ISB Recommendation Research Articles

ISB recommendations on the definition, estimation, and reporting of joint kinematics in human motion analysis applications using wearable inertial measurement technology

There is widespread and growing use of inertial measurement technology for human motion analysis in biomechanics and clinical research. Due to advancements in sensor miniaturization, inertial measurement units can be used to obtain a description of human body and joint kinematics both inside and outside the laboratory. While algorithms for data processing continue to improve, a lack of standard reporting guidelines compromises the interpretation and reproducibility of results, which hinders advances in research and development of measurement and intervention tools. To address this need, the International Society of Biomechanics approved our proposal to develop recommendations on the use of inertial measurement units for joint kinematics analysis. A collaborative effort that incorporated feedback from the biomechanics community has produced recommendations in five categories: sensor characteristics and calibration, experimental protocol, definition of a kinematic model and subject-specific calibration, analysis of joint kinematics, and quality assessment. We have avoided an overly prescriptive set of recommendations for algorithms and protocols, and instead offer reporting guidelines to facilitate reproducibility and comparability across studies. In addition to a conceptual framework and reporting guidelines, we provide a checklist to guide the design and review of research using inertial measurement units for joint kinematics.

Rotation sequences for the calculation of shoulder kinematics of the volleyball attack

Calculating upper extremity kinematics during overhead movements presents with problems typically not seen for the lower extremity due to the large range of motion. Due to these unique issues, different rotation sequences have been suggested to circumvent challenges due to gimbal lock (GL) and angle coherence (AC). The purpose of this study is to determine the most appropriate rotation sequence for shoulder angle calculation during a volleyball attack. METHODS: 15 healthy experienced volleyball players (women = 8) performed 5 attacks off a stationary ball. A 12-camera 3D motion capture system was utilized to record trunk and arm kinematics to compare joint angles calculated using the YXY, ZXY, XZY, YXZ, ZYX, and XYZ rotation sequences. Instances of GL and AC inconsistences were marked for each trial. The last 3 trials were used for analysis. RESULTS: The YXY and XYZ sequences presented with the least total number of errors (12 and 5, respectively). 5 instances of GL were present in the XYZ sequence while none were recorded for the YXY sequence. All other sequences returned incoherent angles that greatly exceeded known ranges of motion. CONCLUSION: When performing kinematic analyses during a volleyball attack, researchers should adhere to ISB recommendations and employ the Eulerian YXY sequence for calculations. If greater anatomical understanding is desired, the XYZ sequence may be utilized for most subjects.

Complete 3D Kinematics Parameters of the Temporo-Mandibular Joints Using in Vivo Data Fusion

ObjectivesThe temporo-mandibular joint (TMJ) has implications in vital functions and its disorder prevalence is between 5% and 12%. The mandible motions rely on two joints where mandibular condyles are generally asymmetric and highly individual. They rotate during jaw opening and closing and translate vertically and anteroposteriorly. Quantitative motion analysis tools are of interest to better understand normal and abnormal TMJ behavior. Previous studies have reported the asymmetrical behavior of the mandible compared to the skull as well as the synchronism of rotation and translation during its motions. But none of them has developed an experimental protocol using in vivo motion data fused with a tridimensional (3D) model. Therefore, we aim to provide the detailed kinematic parameters of the mandible compared to the skull, of the 2 condyles compared to their sockets and the instantaneous helicoidal axis (IHA) calculation through a clearly described new technology: in vivo data motion fused with virtual palpation on 3D models. We also compare the accuracy and the consistency of our results with the existing literature. Material and methodsFive healthy subjects fitted with a tailor-made dental and head clusters performed mouth opening/closing, diduction and chewing motions. 15 anatomical landmarks (ALs) were palpated on their skull and their mandible. The trajectory of the markers and ALs was recorded by opto-electronic cameras. 3D models created from magnetic resonance imaging (MRI) from the 5 subjects were processed through a segmentation procedure and imported into a musculo-skeletal data processing software. Virtual palpation was used to locate specific ALs and to build coordinate systems following the ISB recommendations. The ALs coordinates, the motion files and the morphological model were fused. Motion cycles were normalized from 1 to 100% of rotations and translations duration in coordinate systems, instantaneous helical axis (IHA) parameters were computed for the 3 motions. ResultsMedian RMSE between manually and virtually palpated ALs was 8,0 mm.During opening motion, rotation around the Z-axis (median 24,9°), translations along the X-axis and the Y-axis (median 9,7 mm and 6,3 mm respectively) were happening all at once. The IHA was obliquely orientated.During diduction motion, rotations around the Y-axis and the X-axis (median 10,7° and 3.3° respectively), translation on the Z-axis is (median −9.4 mm) occurred simultaneously. The IHA orientation was oblique and changed accordingly to the diduction side.During chewing motion, median rotation around the Z-axis was −2.2° and median translation on the Y-axis −1.0 mm. The IHA pathway high asymmetry coincided with typical movements of working and balancing condyles. ConclusionComplete 3D kinematics parameters of the TMJs, corresponding to the ISB recommendations, have been extracted with our methodology. Our values matched previous studies if available and the palpation RMSE was within the bounds of precedent experimental protocol. It is therefore efficient to study in vivo motion.Motion data have been registered in an open access data repository, allowing other researchers to exploit them and develop their own TMJ model.

Prediction of shoulder load from wearable sensors for wheelchair related activities: A machine learning approach.

Introduction
 Shoulder problems like pain or pathology are highly prevalent in manual wheelchair users (MWU) with spinal cord injury, lead to limitations in participation, a reduced quality of life and are often associated with “shoulder overload” (Mercer et al., 2006). Laboratory based experiments have examined shoulder load for a variety of wheelchair related activities (WRA; van Drongelen et al., 2005), but no research has been conducted that investigates the actual shoulder load profile of MWU’s in daily conditions. Such a profile would help in understanding the relation of shoulder overload and shoulder problems and could thereby support clinical decision making in the prevention of shoulder problems. Inspired by recent work on machine learning (ML) prediction of joint load from wearable sensors, the current project's ultimate aim is to develop a generalizable ML algorithm that can predict shoulder load for a variety of WRA.
 Methods
 10 able bodied participants were trained before the actual measurement of the WRA of interest: wheelchair propulsion (WCP) at 0.56 and 1.1 m/s at 0%, 0.56 m/s at 6%, WCP in restricted space, short ramp 12% up and down, weight relieve lift, manual material handling with 2 kg and desk work. Participants were equipped with five Shimmer3 sensors on wheelchair, wheel, thorax, upper arm and forearm; EMG was collected from the biceps and medial deltoid muscles. An 8 camera Qualisys system was used to obtain kinematics conform ISB recommendations (Wu et al., 2005). A SmartWheel (Out-Front) for collecting propulsion kinetics replaced the original wheel of a standard Kuschal wheelchair. From laboratory kinematics and kinetics 3D shoulder joint reaction forces (JRF) were estimated with an OpenSim based musculoskeletal model (Wu et al., 2016) (MSM), which consequently served as target for the training of a variety of ML algorithms, using sensor data (acceleration, angular velocity, EMG) as input.
 Results & Discussion
 Starting with simple input (upper arm sensors only) and a linear neural network (NN, one input, one hidden, one output layer for total JRF; iteratively trained following a Leave One Subject Out approach, a R2 of around 60% was obtained between predicted JRF (NN) and target (MSM output), but results varied considerably over participants. In a next phase the complexity of the ML models was increased to deep learning models (recurrent NN) and more signals (e.g. forearm and thorax sensors) were added to the input, which, however, did not improve the overall performance considerably. Currently, it is explored whether using training the algorithms on individual datasets, for single tasks, can improve the performance. The explorative process will be presented and discussed in the light of the relevant results.
 References
 Mercer, J. L., Boninger, M., Koontz, A., Ren, D., Dyson-Hudson, T., & Cooper, R. (2006). Shoulder joint kinetics and pathology in manual wheelchair users. Clincal Biomechanics, 21(8), 781-789. https://doi.org/10.1016/j.clinbiomech.2006.04.010
 van Drongelen, S., van der Woude, L. H., Janssen, T. W., Angenot, E. L., Chadwick, E. K., & Veeger, D. H. (2005). Glenohumeral contact forces and muscle forces evaluated in wheelchair-related activities of daily living in able-bodied subjects versus subjects with paraplegia and tetraplegia. Archives of Physical Medicine and Rehabilitation, 86(7), 1434-1440. https://doi.org/10.1016/j.apmr.2005.03.014
 Wu, W., Lee, P. V. S., Bryant, A. L., Galea, M., & Ackland, D. C. (2016). Subject-specific musculoskeletal modeling in the evaluation of shoulder muscle and joint function. Journal of Biomechanics, 49(15), 3626-3634. https://doi.org/10.1016/j.jbiomech.2016.09.025
 Wu, G., van der Helm, F. C., Veeger, H. E., Makhsous, M., Van Roy, P., Anglin, C., Nagels, J., Karduna, A. R., McQuade, K., Wang, X., Werner, F. W., Buchholz, B., & International Society of, B. (2005). ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion-Part II: Shoulder, elbow, wrist and hand. Journal of Biomechanics, 38(5), 981-992. https://doi.org/10.1016/j.jbiomech.2004.05.042

Rotation sequence and marker tracking method affects the humerothoracic kinematics of manual wheelchair propulsion

The literature on shoulder (humerothoracic) kinematics in manual wheelchair propulsion is growing. Inconsistencies in the reporting of which rotation sequence is used to compute three-dimensional (3D) angles complicates the interpretation and comparison between studies. The purpose of this study was to compare the effects of three often used and recommended rotation sequences (ZXY, XZY, and YXY) and two tracking methods (anatomical and cluster only) on the humerothoracic kinematics of manual wheelchair propulsion. Fourteen able-bodied participants performed manual wheelchair propulsion on a treadmill, while a motion capture system recorded the movements at 120 Hz. Humeral and thoracic segment coordinate systems were constructed according to ISB recommendations. Humerothoracic angles were calculated using each of the three rotation sequences. The ZXY and XZY sequences yielded similar angles in terms of both shape and amplitude, but, perhaps unsurprisingly, these differed substantially from the YXY sequence. Anatomical tracking showed neither gimbal locks nor phase angle discontinuities for any rotation sequence, while cluster tracking yielded phase angle discontinuities for the ZXY and YXY rotation sequences. The two tracking methods yielded similar joint angles for all sequences except for internal/external rotation, and the cluster-only method had larger variability than the anatomical method. These results highlight the importance of reporting which rotation sequence and tracking method are used when calculating humerothoracic angles in order to allow for straightforward interpretation of results and comparison across studies.

Biomechanical analysis of the subscapularis, infraspinatus and teres minor length and moment arm after reverse shoulder arthroplasty: a cadaveric study

BackgroundReverse shoulder arthroplasty (RSA) affects the length and moment arm of the deltoid and rotator cuff. Currently, RSA is commonly considered for cuff-intact conditions, such as primary glenohumeral osteoarthritis. As such, understanding the effect of contemporary lateralized designs on the rotator cuff is paramount. The purpose of this study was to determine changes in length and moment arm of the subscapularis, infraspinatus and teres minor with implantation of one of 3 RSA designs. MethodsA previously validated model was used in 6 hemi-toraces with the shoulder attached. Suture lines were run through pneumatic cylinders from the insertion to the origin of 10 muscles to apply a constant, stabilizing load. Electromagnetic tracking sensors were fixed to the thorax, scapula, and humerus to record 3-dimensional kinematics. Coordinate systems were established according to ISB recommendations. The origin and insertion of the subscapularis, infraspinatus and teres minor were digitized and tracked. Testing consisted of manually rotating the humerus through 5 cycles of its internal-external rotation arc. Kinematic data was collected at 120 Hz. Testing was performed in 3 positions of abduction: 0°, 30°, and 60°. After testing the intact shoulder, RSA was performed using 3 different configurations: an onlay 135-degree humeral component matched with a 2-mm lateralized glenosphere, the same humeral component with a 6-mm lateralized glenosphere, and an inlay 135-degree humeral component matched with a 10 mm lateralized glenosphere. Minimal muscle operative lengths, maximal muscle operative lengths, and muscle moment arms were computed. ResultsWhen compared with the native shoulder, all 3 configurations of RSA resulted in statistically significant increases in both the minimal and maximal operative lengths of the subscapularis in all abduction positions. The teres minor only showed a statistically significant increase in minimal and maximal length at 60° of abduction. The infraspinatus showed a statistically significant increase in tendon excursion at 0° and 30° of abduction. In 40° of abduction and 40° of internal rotation, all RSA configurations translated in a decreased subscapularis internal rotation moment arm. On the contrary, RSA increased the external rotation moment arm of the infraspinatus in neutral rotation and 0° of abduction. ConclusionImplantation of contemporary lateralized RSA implants led to increased length of the subscapularis to a greater extent than the increased length experienced by the infraspinatus and teres minor. The moment arm of the subscapularis decreased, whereas the moment arm of the teres minor in neutral rotation with the arm in abduction increased. Level of EvidenceLevel III; Basic Science, Biomechanics Study

ISB recommendations for skin-marker-based multi-segment foot kinematics

The foot is anatomically and functionally complex, and thus an accurate description of intrinsic kinematics for clinical or sports applications requires multiple segments. This has led to the development of many multi-segment foot models for both kinematic and kinetic analyses. These models differ in the number of segments analyzed, bony landmarks identified, required marker set, defined anatomical axes and frames, the convention used to calculate joint rotations and the determination of neutral positions or other offsets from neutral. Many of these models lack validation. The terminology used is inconsistent and frequently confusing. Biomechanical and clinical studies using these models should use established references and describe how results are obtained and reported.The International Society of Biomechanics has previously published proposals for standards regarding kinematic and kinetic measurements in biomechanical research, and in this paper also addresses multi-segment foot kinematics modeling. The scope of this work is not to prescribe a particular set of standard definitions to be used in all applications, but rather to recommend a set of standards for collecting, calculating and reporting relevant data.The present paper includes recommendations for the overall modeling and grouping of the foot bones, for defining landmarks and other anatomical references, for addressing the many experimental issues in motion data collection, for analysing and reporting relevant results and finally for designing clinical and biomechanical studies in large populations by selecting the most suitable protocol for the specific application.These recommendations should also be applied when writing manuscripts and abstracts.

Coordinate system requirements to determine motions of the tibiofemoral joint free from kinematic crosstalk errors

The relative rigid body motions between the femur and the tibia (termed tibiofemoral kinematics) during flexion activities can provide an objective measure of knee function. Clinically meaningful tibiofemoral kinematics are defined as the six relative rigid body motions expressed in a joint coordinate system where the motions about and along the axes conform to clinical definitions and are free from kinematic crosstalk errors. To obtain clinically meaningful tibiofemoral kinematics, coordinate systems must meet certain requirements which neither have been explicitly stated nor in fact satisfied in any previous publication known to the author. Starting with the joint coordinate system of Grood and Suntay (1983) where motions conform to clinical definitions, the body-fixed axes must correspond to the functional (i.e. actual) axes in flexion-extension and internal-external axial rotation to avoid kinematic crosstalk errors in rotations and both functional axes must be body-fixed throughout knee flexion. To avoid kinematic crosstalk errors in translations, the origins of the femoral and tibial Cartesian coordinate systems, which serve as stepping stones for computing translations, must lie on the functional body-fixed axes. Neither the paper by Grood and Suntay nor the ISB recommendation (Wu et al., 2002) which adopted the joint coordinate system of Grood and Suntay explains these requirements. Indeed meeting these requirements conflicts with the ISB recommendation thus indicating the need for revision to this recommendation. Future studies where clinically meaningful tibiofemoral kinematics are of interest should be guided by the requirements described herein.

WITHDRAWN:Coordinate system requirements to obtain physiologic motions of the tibiofemoral joint

Abstract The relative rigid body motions between the femur and the tibia (termed tibiofemoral kinematics) during flexion activities provide an objective measure of knee function. However, to obtain physiologic tibiofemoral kinematics, coordinate systems must meet certain requirements which neither have been explicitly stated nor in fact satisfied in any previous publication known to the author. Thus the primary purpose of this paper was to explain these requirements. The only valid method for obtaining physiologic tibiofemoral kinematics is to insure that coordinate systems meet four necessary requirements which are 1) the joint coordinate system must follow the convention of Grood and Suntay ( Grood and Suntay, 1983 ), 2) the body-fixed axes must correspond to the functional FE axis of the femur and the functional IE axis of the tibia, 3) the origins of the Cartesian coordinate systems, which serve as a stepping stone for computing translations, must lie on the functional body-fixed axes, and 4) the reference position between the tibia and femur must correspond to neutral with the knee in extension and the change in the components of the vector locating the origins of the Cartesian coordinate systems from the neutral position must be used to determine translations by projecting changes in vector components along the joint coordinate system axes. Neither the paper by Grood and Suntay nor the ISB recommendation ( Wu et al., 2002 ) which adopted the joint coordinate system of Grood and Suntay explains these requirements. Indeed meeting these requirements may not be possible following the ISB recommendation thus indicating the need for revision to this recommendation.

Kinematic Analysis of a Six-Degrees-of-Freedom Model Based on ISB Recommendation: A Repeatability Analysis and Comparison with Conventional Gait Model.

Objective. The purpose of the present work was to assess the validity of a six-degrees-of-freedom gait analysis model based on the ISB recommendation on definitions of joint coordinate systems (ISB 6DOF) through a quantitative comparison with the Helen Hays model (HH) and repeatability assessment. Methods. Four healthy subjects were analysed with both marker sets: an HH marker set and four marker clusters in ISB 6DOF. A navigated pointer was used to indicate the anatomical landmark position in the cluster reference system according to the ISB recommendation. Three gait cycles were selected from the data collected simultaneously for the two marker sets. Results. Two protocols showed good intertrial repeatability, which apart from pelvic rotation did not exceed 2°. The greatest differences between protocols were observed in the transverse plane as well as for knee angles. Knee internal/external rotation revealed the lowest subject-to-subject and interprotocol repeatability and inconsistent patterns for both protocols. Knee range of movement in transverse plane was overestimated for the HH set (the mean is 34°), which could indicate the cross-talk effect. Conclusions. The ISB 6DOF anatomically based protocol enabled full 3D kinematic description of joints according to the current standard with clinically acceptable intertrial repeatability and minimal equipment requirements.

FRI0581-HPR The effect of muscular strength on scapular kinematics in asymptomatic shoulders with or without scapular dyskinesis

BackgroundScapular dyskinesis is alternations in scapular position and motion, has been associated with various shoulder pathologies [1]. An appropriate scapular upward rotation is considered to be essential for normal shoulder...

Influence of kinematic analysis methods on detecting ankle and subtalar joint instability

Patients with subtalar joint instability may be misdiagnosed with ankle instability, which may lead to chronic instability at the subtalar joint. Therefore, it is important to understand the difference in kinematics after ligament sectioning and differentiate the changes in kinematics between ankle and subtalar instability. Three methods may be used to determine the joint kinematics; the Euler angles, the Joint Coordinate System (JCS) and the helical axis (HA). The purpose of this study was to investigate the influence of using either method to detect subtalar and ankle joints instability. 3D kinematics at the ankle and subtalar joint were analyzed on 8 cadaveric specimens while the foot was intact and after sequentially sectioning the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), the cervical ligament and the interosseous talocalcaneal ligament (ITCL). Comparison in kinematics calculated from sensor and anatomical landmarks was conducted as well as the influence of Euler angles and JCS rotation sequence (between ISB recommendation and previous research) on the subtalar joint. All data showed a significant increase in inversion when the ITCL was sectioned. There were differences in the data calculated using sensors coordinate systems vs. anatomic coordinate systems. Anatomic coordinate systems were recommended for these calculations. The Euler angle and JCS gave similar results. Differences in Euler angles and JCS sequence lead to the same conclusion in detecting instability at the ankle and subtalar joint. As expected, the HA detected instability in plantarflexion at the ankle joint and in inversion at the subtalar joint.

Relation Between Kinematic Analysis of Wheelchair Propulsion and Wheelchair Functional Basketball Classification

The objective was to conduct a methodological pilot study to analyze wheelchair propulsion upper limb kinematics in standard competitive play considering the functional classification of each athlete. Ten basketball players with a functional classification ranging from 1 to 4 were included in the study. Four camcorders (Kinescan-IBV) and a treadmill for wheelchairs were used. Temporal parameters were analyzed and the upper limb kinematics was obtained using ISB recommendations. The value of the temporal parameters such as push phase duration, the ratio of push phase/recovery phase, contact, and propulsion angle seems to reduce as the functional classification increases. A methodological protocol has been developed that allows the analysis of kinematic characteristics of wheelchair propulsion in basketball players taking into account their functional classification.

A method for estimating three-dimensional human arm movement with two electromagnetic sensors

Measurement of upper-limb movements is important in various domains. In this article, an upper-limb three-dimensional movement recording technique is proposed based on only two electromagnetic sensors. Two joints are considered with a total of seven degrees of freedom (DoF; three translations and four rotations). The chosen sequence of joint rotations is compliant with ISB recommendations: the shoulder is modelled with a ball and socket joint with three DoF and the elbow with a one DoF revolute joint. This article is focused on the procedure used to calibrate and sense the upper-limb movements from the raw data coming from the flock of birds sensors. The principle of the method is to define the centre of the wrist, elbow and shoulder joints in the frame of the adequate sensor. This operation is done by performing calibration gestures. Results are proposed and commented.

Kinematic analysis and dexterity evaluation of upper extremity in activities of daily living

The redundant kinematic structure of upper extremity (UE) provides it with increased dexterity in activities of daily living (ADL). Most functional tasks during ADL can be implemented in various positions; however, only some routine trajectories are employed in healthy humans. Exploring motion ability and analyzing dexterity are clinically helpful in understanding the motion principles of the UE during ADL. The aim of this work was to develop a qualitative and quantitative evaluation method for unconstrained movement analysis of the UE. Ten healthy male volunteers with no UE pathology were tested based on a kinematic model proposed in this paper which follows the ISB recommendations. The dexterity measure (DM) and manipulability ellipsoid (ME) were used to evaluate the dexterity distribution and motion ability in space. Representative dexterity trajectories and corresponding ellipsoids were determined for the ADL tasks. The results of the study showed that there was a most dexterous posture for each functional task. The UE movement followed an approximately optimal kinematic performance trajectory when the hand moved in front of the thorax during ADL.

Rotation sequence is an important factor in shoulder kinematics. Application to the elite players’ flat serves

The aim of this study was to test three different rotation sequences (YXY, ZXY, and XZY) on the shoulder kinematics (rotations of the humerus relative to the thorax) during an original movement such as the tennis flat serve (FS). Nine elite male and female players performed a minimum of five flat serves. An optoelectronic motion analysis system was used to record the movements. Segment kinematics during each FS was reconstructed from the spatial trajectories of the markers according to ISB recommendations. For each rotation sequence, three angles were reported for the shoulder joint, each corresponding to a rotation component around a defined axis. The occurrence of gimbal lock (GL) and angle amplitude coherences were examined. From these three rotation sequences tested, it appears that the XZY sequence was the only decomposition not to suffer from GL. Moreover, the rotation sequence XZY was found to be coherent for all rotation components. Thus, these results show that the best rotation sequence, from both GL and amplitude coherence points of view, is XZY to describe the shoulder kinematics during the tennis serve.

Comparison of three standard anatomical reference frames for the tibia–fibula complex

Definition of anatomical reference frames is necessary both for in vitro biomechanical testing, and for in vivo human movement analyses. Different reference frames have been proposed in the literature for the lower limb, and in particular for the tibia–fibula complex. The scope of this work was to compare the three most commonly referred proposals (proposed by [Ruff, C.B., Hayes, W.C., 1983. Cross-sectional geometry at Pecos Pueblo femora and tibiae —A biomechanical investigation: I. method and general patterns of variation. American Journal of Physical Anthropology 60, pp. 359–381.], by [Cappozzo, A., Catani, F., Della Croce, U., Leardini, A., 1995. Position and orientation in space of bones during movement: anatomical frame definition and determination. Clinical Biomechanics (Bristol, Avon) 10, pp. 171–178.], and by the Standardization and Terminology Committee of the International Society of Biomechanics, [Wu, G., Siegler, S., Allard, P., Kirtley, C., Leardini, A., Rosenbaum, D., Whittle, M., D'Lima, D.D., Cristofolini, L., Witte, H., Schmid, O., Stokes, I., 2002. ISB recommendation on definitions of joint coordinate system of various joints for reporting of human joint motion—part I: ankle, hip and spine. International Society of Biomechanics. Journal of Biomechanics 35, pp. 543–548.]). These three frames were identified on six cadaveric tibia–fibula specimens based on the relevant anatomical landmarks, using a high-precision digitizer. The intra-operator (ten repetitions) and inter-operator (three operators) repeatability were investigated in terms of reference frame orientation. The three frames had similar intra-operator repeatability. The reference frame proposed by Ruff et al. had a better inter-operator repeatability (this must be put in relation with the original context of interest, i.e. in vitro measurements on dissected bones). The reference frames proposed by Ruff et al. and by ISB had a similar alignment; the frame proposed by Cappozzo et al. was considerably externally rotated and flexed with respect to the other two. Thus, the reference frame proposed by Ruff et al. is preferable when the full bone surface is accessible (typically during in vitro tests). Conversely, no advantage in terms of repeatability seems to exist between the reference frames proposed by Cappozzo et al. and ISB.

Concurrent Free Paper Sessions 1

Concurrent Free Paper Sessions 1

COORDINATE SYSTEM VALIDATION FOR KINEMATICS ANALYSIS OF THE CARPAL BONES

INTRODUCTION Analysis of 3D-kinematics of the carpal bones faces several difficulties, due to their small size, complicated shape and uneasy access. Among the problems encountered, the definition of coordinate frames has to be valid and reliable. The ISB recommendations concerning the carpal joint coordinate systems have [1] recently been criticized [2]. In the past, several approaches have been proposed in studies using medical imaging to study carpal kinematics. These include the use of anatomical landmarks [3], inertial axes [2,4], or surface registration [5,6]. The aim of this study was to compare kinematics data obtained using anatomical landmarks and inertial axes and to validate them using implanted landmarks.

Shoulder movements during the initial phase of learning manual wheelchair propulsion in able-bodied subjects

The kinetics and kinematics of the glenohumeral joints, and shoulder muscles activities during the initial phase of learning wheelchair propulsion by individuals with paraplegia have been partially described. But no studies carry out the kinematics of the upper-limb during the learning of non-constrained open field locomotion with a wheelchair. Ten subjects with no manual wheelchair experience propelled themselves repetitively straight ahead along an 11m linear path. Upper-limb segment orientations were measured with an electromagnetic system. Angular displacements of joints were determined using a standardized protocol [Wu, G., Van der Helm, F.C.T., Veeger, H.E.J., Makhsous, M., Van Roy, P., Anglin, C., Nagels, J., Karduna, A.R., McQuade, K., Wang, X., Wernerl, F.W., Buchholzm, B., 2005. ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion--Part II: shoulder, elbow, wrist and hand. J. Biomech. 38(5), 981-992] and a modeling method [Biryukova, E.V., Roby-Brami, A., Frolov, A.A., Mokhtari, M., 2000. Kinematics of human arm reconstructed from spatial tracking system recordings. J. Biomech. 33, 985-995]. A full 3-D scapular motion description was obtained that allowed us to measure the mean amplitudes of rotation for the nine degrees of freedom of our model. The change in the propulsion pace and the repetition of trials induced a general increase of amplitudes of joint rotations that can explain the increase of velocity among trials. We did not observe a freezing of any DOF as predicted by Bernstein's theory of motor learning, but the increase in joint movement amplitudes could correspond to his "unfreezing of DOF" stage. This non-respect of Bernstein's theory could originate in the relative simplicity of the task.