Patrick Salvia

Validity and reliability of the Kinect within functional assessment activities: comparison with standard stereophotogrammetry.

The recent availability of the Kinect™ sensor, a cost-effective markerless motion capture system (MLS), offers interesting possibilities in clinical functional analysis and rehabilitation. However, neither validity nor reproducibility of this device is known yet. These two parameters were evaluated in this study. Forty-eight volunteers performed shoulder abduction, elbow flexion, hip abduction and knee flexion motions; the same protocol was repeated one week later to evaluate reproducibility. Movements were simultaneously recorded by the Kinect (with Microsoft Kinect SDK v.1.5) MLS and a traditional marker-based stereophotogrammetry system (MBS). Considering the MBS as reference, discrepancies between MLS and MBS were evaluated by comparing the range of motion (ROM) between both systems. MLS reproducibility was found to be statistically similar to MBS results for the four exercises. Measured ROMs however were found different between the systems.

Registration of 6-DOFs electrogoniometry and CT medical imaging for 3D joint modeling

The paper describes a method in which two data-collecting systems, medical imaging and electrogoniometry, are combined to allow the accurate and simultaneous modeling of both the spatial kinematics and the morphological surface of a particular joint. The joint of interest (JOI) is attached to a Plexiglas jig that includes four metallic markers defining a local reference system (R(GONIO)) for the kinematics data. Volumetric data of the JOI and the R(GONIO) markers are collected from medical imaging. The spatial location and orientation of the markers in the global reference system (R(CT)) of the medical-imaging environment are obtained by applying object-recognition and classification methods on the image dataset. Segmentation and 3D isosurfacing of the JOI are performed to produce a 3D model including two anatomical objects-the proximal and distal JOI segments. After imaging, one end of a custom-made 3D electrogoniometer is attached to the distal segment of the JOI, and the other end is placed at the R(GONIO) origin; the JOI is displaced and the spatial kinematics data is recorded by the goniometer. After recording, data registration from R(GONIO) to R(CT) occurred prior to simulation. Data analysis was performed using both joint coordinate system (JCS) and instantaneous helical axis (IHA).Finally, the 3D joint model is simulated in real time using the experimental kinematics data. The system is integrated into a computer graphics interface, allowing free manipulation of the 3D scene. The overall accuracy of the method has been validated with two other kinematics data collection methods including a 3D digitizer and interpolation of the kinematics data from discrete positions obtained from medical imaging. Validation has been performed on both superior and inferior radio-ulna joints (i.e. prono-supination motion). Maximal RMS error was 1 degrees and 1.2mm on the helical axis rotation and translation, respectively. Prono-supination of the forearm showed a total rotation of 132 degrees for 0.8mm of translation. The method reproducibility using JCS parameters was in average 1 degrees (maximal deviation=2 degrees ) for rotation, and 1mm (maximal deviation=2mm) for translation. In vitro experiments have been performed on both knee joint and ankle joint. Averaged JCS parameters for the knee were 109 degrees, 17 degrees and 4 degrees for flexion, internal rotation and abduction, respectively. Averaged maximal translation values for the knee were 12, 3 and 4mm posteriorly, medially and proximally, respectively. Averaged JCS parameters for the ankle were 43 degrees, 9 degrees and 3 degrees for plantarflexion, adduction and internal rotation, respectively. Averaged maximal translation values for the ankle were 4, 2 and 1mm anteriorly, medially and proximally, respectively.

Functional and outcome evaluation of the hand and wrist

The first evaluation of the upper extremity and hand, performed by the surgeon at the outpatient clinic, is fundamental to understanding the patients problem, determining the best treatment options, and, in the case of a surgical indication, assessing the preoperative status. In addition to recording the patients symptoms and complaints, the surgeon evaluates anatomic integrity, stability, mobility, trophicity, strength, and sensibility. In many patients, especially patients with severe handicaps or those who anticipate long delays in rehabilitation, in litigation problems, or as part of prospective clinical research, this classic evaluation is not sufficient. The authors recommend that to accommodate these patients, a laboratory of functional evaluation of the hand should be established. The evaluation, performed by independent reviewers, ideally includes techniques allowing objective measurements of kinematics, strength, sensibility, and global hand function and dexterity. Pain assessment using the VAS is indispensable. The results may be presented as scores based on to the patients problem. The researchers should analyze precisely how the scores were constructed. Questionnaires are part of the evaluation armamentarium. As with other tools, questionnaires allow us to understand better what our patients experience. They do not replace physical examination. Questionnaires also could be used for routine screening in a general upper limb practice, even before the patient sees the hand surgeon. The choice of the questionnaire is important; the reviewer should make sure that the patient understands all questions, that the questions are not redundant, and that they do apply to the patient. Generic health status instruments such as the SF-36 allow comparison across a variety of health problems, including mental and physical conditions, but are not sensitive to upper extremity disability. The DASH questionnaire seems a better choice, allowing a standardized outcome evaluation. Dedicated questionnaires have been developed for specific conditions (eg, carpal tunnel syndrome). As discussed by Amadio, questionnaires are easier to perform than physical testing, can be self-administered, and require no special equipment, saving the cost of an examiner, avoiding the complexities of scheduling a follow-up examination, and eliminating the possibility of observer bias. The patient is less likely to offer polite but incorrect responses. Questionnaires are especially useful when patients perceptions are important to assess. Questionnaires also could be used in longitudinal studies to assess improvement or aggravation. The use of questionnaires is therefore especially indicated in studies involving a large number of patients, when observer bias and costs are concerns, and when the main outcome measurements are satisfaction, symptoms, or functional status. Amadio has pointed out that questionnaires are not the best tool to measure anatomic or physiologic impairments.

Head repositioning accuracy in patients with whiplash-associated disorders.

Study Design. Controlled study, measuring head repositioning error (HRE) using an electrogoniometric device. Objective. To compare HRE in neutral position, axial rotation and complex postures of patients with whiplash-associated disorders (WAD) to that of control subjects. Summary of Background Data. The presence of kinesthetic alterations in patients with WAD is controversial. Methods. In 26 control subjects and 29 patients with WAD (aged 22–74 years), head kinematics was sampled using a 3-dimensional electrogoniometer mounted using a harness and a helmet. All tasks were realized in seated position. The repositioning tasks included neutral repositioning after maximal flexion-extension, eyes open and blindfolded, repositioning at 50° of axial rotation, and repositioning at 50° of axial rotation combined to 20° of ipsilateral bending. The flexion-extension, ipsilateral bending, and axial rotation components of HRE were considered. A multiple-way repeated-measures analysis of variance was used to compare tasks and groups. Results. The WAD group displayed a reduced flexion-extension range (P = 1.9 × 10−4), and larger HRE during flexion-extension and repositioning tasks (P = 0.009) than controls. Neither group nor task affected maximal motion velocity. Neutral HRE of the flexion-extension component was larger in blindfolded condition (P = 0.03). Ipsilateral bending and axial rotation HRE components were smaller than the flexion-extension component (P = 7.1 × 10−23). For pure rotation repositioning, axial rotation HRE was significantly larger than flexion-extension and ipsilateral bending repositioning error (P = 3.0 × 10−23). Ipsilateral bending component of HRE was significantly larger combined tasks than for pure rotation tasks (P = 0.004). Conclusions. In patients with WAD, range of motion and head repositioning accuracy were reduced. However, the differences were small. Vision suppression and task type influenced HRE.

Determination of the precision and accuracy of morphological measurements using the Kinect™ sensor: comparison with standard stereophotogrammetry

The recent availability of the Kinect™ sensor, a low-cost Markerless Motion Capture (MMC) system, could give new and interesting insights into ergonomics (e.g. the creation of a morphological database). Extensive validation of this system is still missing. The aim of the study was to determine if the Kinect™ sensor can be used as an easy, cheap and fast tool to conduct morphology estimation. A total of 48 subjects were analysed using MMC. Results were compared with measurements obtained from a high-resolution stereophotogrammetric system, a marker-based system (MBS). Differences between MMC and MBS were found; however, these differences were systematically correlated and enabled regression equations to be obtained to correct MMC results. After correction, final results were in agreement with MBS data (p = 0.99). Results show that measurements were reproducible and precise after applying regression equations. Kinect™ sensors-based systems therefore seem to be suitable for use as fast and reliable tools to estimate morphology. Practitioner Summary: The Kinect™ sensor could eventually be used for fast morphology estimation as a body scanner. This paper presents an extensive validation of this device for anthropometric measurements in comparison to manual measurements and stereophotogrammetric devices. The accuracy is dependent on the segment studied but the reproducibility is excellent.

Precision of shoulder anatomical landmark calibration by two approaches: A CAST-like protocol and a new Anatomical Palpator method

The objective of the study was to compare the precision of shoulder anatomical landmark palpation using a CAST-like method and a newly developed anatomical palpator device (called A-Palp) using the forefinger pulp directly. The repeated-measures experimental design included four examiners that twice repeated measurements on eleven scapula and humerus anatomical landmarks during two sessions. Inter-session and inter-examiner precision was determined on volunteers. A-Palp accuracy was obtained from in vitro measurements and using virtual palpation on 3D bone models. Error propagation on the motion representation was also analyzed for a continuous motion of abduction movement performed in the shoulder joint. Palpation results showed that CAST and A-Palp methods lead to similar precision with the Maximal A-Palp calibration error being 1.5mm. In vivo precision of the CAST and A-Palp methods varied between 4mm (inter-session) and 8mm (inter-examiner). Mean propagation of the palpation error on the motion graph representation was 2 degrees and 5 degrees for scapula and humerus, respectively. A-Palp accuracy was 3.6 and 8.1mm for scapula and humerus, respectively. The A-Palp seems promising and could probably become an additional method next to todays marker-based motion analysis systems (i.e., Helen-Hayes configuration, CAST method).

Femur shape prediction by multiple regression based on quadric surface fitting

Quadric surface fitting of joint surface areas is often performed to allow further processing of joint component size, location and orientation (pose), or even to determine soft tissue wrapping by collision detection and muscle moment arm evaluation. This study aimed to determine, for the femoral bone, if the position of its morphological joint centers and the shape morphology could be approximated using regression methods with satisfactory accuracy from a limited amount of palpable anatomical landmarks found on the femoral bone surface. The main aim of this paper is the description of the pipeline allowing on one hand the data collection and database storage of femoral bone characteristics, and on the other hand the determination of regression relationships from the available database. The femoral bone components analyzed in this study included the diaphysis, all joint surfaces (shape, location and orientation of the head, condyles and femoro-patellar surface) and their respective spatial relationships (e.g., cervico-diaphyseal angle, cervico-bicondylar angle, intercondylar angle, etc.). A total of 36 morphological characteristics are presented and can be estimated by regression method in in-vivo applications from the spatial location of 3 anatomical landmarks (lateral epicondyle, medial epicondyle and greater trochanter) located on the individual under investigation. The method does not require any a-priori knowledge on the functional aspect of the joint. In-vivo and in-vitro validations have been performed using data collected from medical imaging by virtual palpation and data collected directly on a volunteer using manual palpation through soft tissue. The prediction accuracy for most of the 36 femoral characteristics determined from virtual palpation was satisfactory, mean (SD) distance and orientation errors were 2.7(2.5)mm and 6.8(2.7)°, respectively. Manual palpation data allowed good accuracy for most femoral features, mean (SD) distance and orientation errors were 4.5(5.2)mm and 7.5(5.3)°, respectively. Only the in-vivo location estimation of the femoral head was worse (position error=23.2mm). In conclusion, results seem to show that the method allows in-vivo femoral joint shape prediction and could be used for further development (e.g., surface collision, muscle wrapping, muscle moment arm estimation, joint surface dimensions, etc.) in gait analysis-related applications.

Model-based approach for human kinematics reconstruction from markerless and marker-based motion analysis systems

Modeling tools related to the musculoskeletal system have been previously developed. However, the integration of the real underlying functional joint behavior is lacking and therefore available kinematic models do not reasonably replicate individual human motion. In order to improve our understanding of the relationships between muscle behavior, i.e. excursion and motion data, modeling tools must guarantee that the model of joint kinematics is correctly validated to ensure meaningful muscle behavior interpretation. This paper presents a model-based method that allows fusing accurate joint kinematic information with motion analysis data collected using either marker-based stereophotogrammetry (MBS) (i.e. bone displacement collected from reflective markers fixed on the subjects skin) or markerless single-camera (MLS) hardware. This paper describes a model-based approach (MBA) for human motion data reconstruction by a scalable registration method for combining joint physiological kinematics with limb segment poses. The presented results and kinematics analysis show that model-based MBS and MLS methods lead to physiologically-acceptable human kinematics. The proposed method is therefore available for further exploitation of the underlying model that can then be used for further modeling, the quality of which will depend on the underlying kinematic model.

In vivo registration of both electrogoniometry and medical imaging: development and application on the ankle joint complex

An in vivo method for joint kinematics visualization and analysis is described. Low-dose computed tomography allowed three-dimensional joint modeling, and electrogoniometry collected joint kinematic data. Data registration occurred using palpated anatomical landmarks to obtain interactive computer joint simulation. The method was applied on one volunteers ankle, and reproducibility was tested (maximal discrepancy: 3.6 deg and 5.5 mm for rotation and translation respectively).

Development of kinematics tests for the evaluation of lumbar proprioception and equilibration

OBJECTIVE This study aimed at developing lumbar repositioning and seated equilibration tests. DESIGN 3D-electrogoniometric study of trunk repositioning and equilibration in seated position. BACKGROUND Postural equilibrium and lumbar proprioception alterations have been shown in patients with low-back pain. METHODS In 21 healthy volunteers, pure flexion and flexion+rotation repositioning error was measured using 3D-electrogoniometry. Lumbar kinematics was analysed (time and frequency domain) during antero-posterior and lateral equilibration tests in seated position. Reproducibility and stability of the protocol were evaluated. RESULTS Reproducibility and stability were good. Pure flexion repositioning error was similar to previous reports. For flexion+rotation tests, repositioning error was 3 degrees for flexion and 1 degrees for rotation. Amplitude, imbalance time and power spectrum were significantly larger in lateral than in antero-posterior equilibration tests. CONCLUSIONS The feasibility of kinematic analysis of lumbar repositioning and equilibration was shown. Repositioning error values were in agreement with previous studies. New tests and parameters were proposed. Lateral equilibration tests appeared more demanding than antero-posterior tests. RELEVANCE In patients with low-back pain, lumbar repositioning and equilibration tests may be of use to define rehabilitation strategies and to evaluate treatment outcome.