Evaluation of alternative technical markers for the pelvic coordinate system

Adaptation of balancing behaviour during continuous perturbations of stance. Supra-postural visual tasks and platform translation frequency modulate adaptation rate

When humans are administered continuous and predictable perturbations of stance, an adaptation period precedes the steady state of balancing behaviour. Little information is available on the modulation of adaptation by vision and perturbation frequency. Moreover, performance of supra-postural tasks may modulate adaptation in as yet unidentified ways. Our purpose was to identify differences in adaptation associated to distinct visual tasks and perturbation frequencies. Twenty non-disabled adult volunteers stood on a platform translating 10 cm in antero-posterior (AP) direction at low (LF, 0.18 Hz) and high frequency (HF, 0.56 Hz) with eyes open (EO) and closed (EC). Additional conditions were reading a text fixed to platform (EO-TP) and reading a text stationary on ground (EO-TG). Peak-to-peak (PP) displacement amplitude and AP position of head and pelvis markers were computed for each of 27 continuous perturbation cycles. The time constant and extent of head and pelvis adaptation and the cross-correlation coefficients between head and pelvis were compared across visual conditions and frequencies. Head and pelvis mean positions in space varied little across conditions and perturbation cycles but the mean head PP displacements changed over time. On average, at LF, the PP displacement of the head and pelvis increased progressively. Adaptation was rapid or ineffective with EO, but slower with EO-TG, EO-TP, EC. At HF, the head PP displacement amplitude decreased progressively with fast adaptation rates, while the pelvis adaptation was not apparent. The results show that visual tasks can modulate the adaptation rate, highlight the effect of the perturbation frequency on adaptation and provide evidence of priority assigned to pelvis stabilization over visual tasks at HF. The effects of perturbation frequency and optic flow and their interaction with other sensory inputs and cognitive tasks on the adaptation strategies should be investigated in impaired individuals and considered in the design of rehabilitation protocols.

Assessment of Pelvic-Lumbar-Thigh Biomechanics to Optimize The Childbirth Position: An "In Vivo" Innovative Biomechanical Study

The study aimed to assess the associations between the pelvis orientation, lumbar curve and thigh postures throughout pregnancy in a population of healthy women. Additionally, optimal mechanical birth conditions in terms of the pelvic inlet and lumbar curve were researched. The individuals' posture was assessed with three-dimensional motion analysis and the lumbar curve with the Epionics SPINE system. The association between the hip joint angles (flexion and abduction), the pelvis external conjugate, and lumbar curve position was assessed with a generalized linear mixed model (GLMM) adjusted to individuals' characteristics. Joint laxity was assessed with a modified Jobbin's extensometer. For all of the subjects, hip flexion and hip abduction were significantly associated with the angle between the external conjugate and spine, with higher correlation in the multivariate regression model. The association between hip flexion and the lumbar curve was less significant in multivariate than univariate regression analysis. Optimal birth conditions were never reached. The findings contribute to the understanding of the association between the hip position (flexion and abduction), pelvic orientation, and lumbar curve adjusted for joint laxity in healthy pregnant women. They lay the groundwork for future research in the field of obstetrical biomechanics.

Walking breaks can reduce prolonged standing induced low back pain

Standing is commonly recommended to reduce sedentary behavior in the workplace; however, constrained prolonged standing has also been linked to musculoskeletal symptoms, such as low back pain (LBP). Light physical activity breaks, such as walking, may change lumbar spine posture enough to reduce LBP during standing. This study assessed the effectiveness of inserting 5-minute walking breaks every 25 min for reducing prolonged standing-induced LBP development. Nineteen participants completed two bouts of standing lasting 2 h - one with a 5-minute walking break every 25 min and one with no breaks. Pain measures were completed throughout the trial to categorize participants as pain developers (PDs) or non-pain developers (non-PDs). Lumbar region kinematics angle and range of motion were measured continuously. In standing, 58% (11/19) of participants were PDs, compared to just 26% when walking breaks were inserted. Seventy-three percent (8/11) were categorized as non-PDs with walking breaks. Median lumbar flexion increased during walking compared to standing. Lumbar region range of motion in the coronal and transverse planes also increased during walking. The intermittent lumbar flexion may help decrease LBP during prolonged standing. These results demonstrate that walking breaks may help promote lumbar movement and reduce prolonged standing-induced LBP.

Obtaining patient-specific point model of the human ilium bone in the case of incomplete volumetric data using the method of parametric regions

In this paper, we present the methodology for determining the point model of the ilium bone in cases when volumetric data of the whole bone are not available. An extreme traumatic bone damage, osteoporosis, destruction of bone tissue by malignant bone tumors or the existence of only 2D medical image (X-ray) can be the reason for the lack of complete volumetric data. Points on the bone surface were defined at the curves that run through 26 previously defined parameters, at the edges of anteroposterior (A-P) and lateral projections and at the parts of the surface between some parameters. Those parts of the surface, enclosed by parameters, represent ten parametric regions. The values of coordinates, which represent the input data in the statistical program, were measured in a uniquely defined coordinate system. After establishing the correlations between the values of coordinates, 8869 different linear and nonlinear regression models were obtained. The prediction values for point coordinates were calculated and exported to a CAD program. Results obtained were tested on a randomly chosen male right ilium bone, applying the methodology for creating the prediction model using the method of parametric regions, which allows creating a complete polygonal model, for each region separately or just for some parts of the region. Results obtained in the form of regression equations for the right ilium bone can be applied to the left ilium bone. The results of the research were verified using a comparative deviation and distance analysis between the initial and obtained polygonal models.

A public dataset of overground and treadmill walking kinematics and kinetics in healthy individuals

In a typical clinical gait analysis, the gait patterns of pathological individuals are commonly compared with the typically faster, comfortable pace of healthy subjects. However, due to potential bias related to gait speed, this comparison may not be valid. Publicly available gait datasets have failed to address this issue. Therefore, the goal of this study was to present a publicly available dataset of 42 healthy volunteers (24 young adults and 18 older adults) who walked both overground and on a treadmill at a range of gait speeds. Their lower-extremity and pelvis kinematics were measured using a three-dimensional (3D) motion-capture system. The external forces during both overground and treadmill walking were collected using force plates and an instrumented treadmill, respectively. The results include both raw and processed kinematic and kinetic data in different file formats: c3d and ASCII files. In addition, a metadata file is provided that contain demographic and anthropometric data and data related to each file in the dataset. All data are available at Figshare (DOI: 10.6084/m9.figshare.5722711). We foresee several applications of this public dataset, including to examine the influences of speed, age, and environment (overground vs. treadmill) on gait biomechanics, to meet educational needs, and, with the inclusion of additional participants, to use as a normative dataset.

New approaches for assessing childbirth positions

BACKGROUND

An overview of labor based only on epidemiological data cannot identify or explain the mechanisms involved in childbirth. Data about the position that women should take in giving birth are discordant. None of the studies of birth positions adequately define or describe them or their biomechanical impact (pelvic orientation, position of the back). The measurement of the effect of one position relative to that of another requires precise definitions of each position and of their maternal biomechanical consequences, as well as safe measurement methods.

METHODOLOGY

We have developed a system to analyze the position of labor by quantifying the posture of the woman's body parts (including thighs, trunk, and pelvis), using an optoelectronic motion capture device (Vicon™, Oxford Metrics) widely used in human movement analysis and a system for measuring the lumbar curve (Epionics spine system). A specific body model has also been created to conduct this biomechanical analysis, which is based on external markers. With this methodology and model, it should be possible to define: (1) the hip joint angles (flexion/extension, abduction/adduction, internal/external rotation); (2) the ante/retroversion of the pelvis; (3) the lumbar curve.

DISCUSSION

This methodology could become a reference for assessing delivery postures, one that makes it possible to describe the relation between the postures used in the delivery room and their impact on the pelvis and the spine in an integrated and comprehensive model.

TRIAL REGISTRATION

No. Eudract 2013-A01203-42.

Performance of a lateral pelvic cluster technical system in evaluating running kinematics

Valid measurement of pelvic and hip angles during posterior load carriage gait task requires placement of pelvic markers which will not be occluded or physically displaced by the load. One solution is the use of pure lateral pelvic clusters to track the pelvis segment. However, the validity of this method has not been compared against pelvic marker systems recommended by the International Society of Biomechanics (ISB) during high impact tasks, such as running. The purpose of this study was to validate the lateral tracking pelvic clusters against the ISB pelvis during running. Six participants performed overground running at a self-selected running speed with shoes. Three dimensional motion capture and synchronised in-ground force plates were used to determine lower limb joint angles and gait events respectively. Two biomechanical models were used to derive pelvic segment and hip joint angles. The ISB pelvis used the anterior and posterior iliac spines as anatomical and tracking markers, whilst the other model used lateral pelvic clusters as tracking markers. The between participant averaged coefficient of multiple correlation suggested good to excellent agreement between the angle waveforms generated from the two marker protocols. In addition, both marker protocols had similar sensitivity in detecting three dimensional pelvic and hip joint angles during the stance phase. This study suggests that in the event posterior load carriage is involved in running gait, pelvic and hip kinematics can be measured by the use of lateral pelvic clusters.

Comparison of two alternative technical marker sets for measuring 3D pelvic motion during gait

When using motion capture to measure pelvic motion, situations in which the anterior superior iliac spines (ASISs) or posterior superior iliac spines (PSISs) are obscured from view require that an alternative technical marker set be used to track the pelvis. The current study evaluated the accuracy and temporal similarity (i.e., cross-correlation) of two alternative pelvic models compared to the standard pelvic model during gait. The first alternative model used markers placed on the ASISs and iliac crests (ASIS-IC), while the second alternative model used markers placed on the PSISs and iliac crests (PSIS-IC). Both alternative models demonstrated an acceptable degree of accuracy in the sagittal, frontal, and transverse planes (root-mean-square error <1.4° in all planes). The temporal similarity between both alternative models and the standard model was "very strong" in the frontal and transverse planes. In the sagittal plane, the temporal similarity was also "very strong" for the PSIS-IC model and "strong" for the ASIS-IC model. Although statistically significant differences were found between the two alternative models for some of the variables, the practical significance of these findings is generally questionable considering the magnitude of the differences. These results suggest that both alternative models are suitable alternatives to the standard pelvic model for tracking pelvic motion. However, consideration would need to be paid to the spatial resolution and temporal resolution requirements, as well as the specific plane(s) of movement that are deemed most important, for a particular investigation if one of these alternative models is to be used.

Effects of transporting an infant on the posture of women during walking and standing still

We investigated the effects on women of carrying an infant in front, focusing on the pelvic and spinal posture and the displacement of the body's center of gravity. For such, we compared mothers to non-mothers not carrying anything or carrying the same load (a doll) and the mothers carrying their infants. Twenty mothers and 44 women who did not have children were analyzed for their movement and posture during walking and standing still with a motion capture system. Walking while carrying a load was slower and with a shorter stride length than while not carrying a load. The mothers' group walked slower and with a shorter stride length than the non-mothers' group. During walking and standing still, the women decreased their angle of pelvic anteversion, increased lumbar lordosis, increased thoracic kyphosis, and increased trunk backward inclination while carrying a load in comparison with not carrying anything. In addition, we observed some small differences in the spinal angles of mothers when carrying their infants compared to when carrying a doll. When standing still, the women carrying a load displaced backwards their vertical projection of the center of gravity to exactly compensate the destabilizing load at the front that resulted in no net change of the body-plus-load center of gravity. In general, these changes are qualitatively similar to the ones observed during pregnancy.