The selection of an appropriate and/or standardized method for representing 3-D joint attitude and motion is a topic of popular debate in the field of biomechanics. The joint coordinate system (JCS) is one method that has seen considerable use in the literature. The JCS consists of an axis fixed in the proximal segment, an axis fixed in the distal segment, and a "floating" axis. There has not been general agreement in the literature on how to select the body fixed axes of the JCS. The purpose of this paper is to propose a single definition of the body fixed axes of the JCS. The two most commonly used sets of body fixed axes are compared and the differences between them quantified. These differences are shown to be relevant in terms of practical applications of the JCS. Argumentation is provided to support a proposal for a standardized selection of body fixed axes of the JCS consisting of the axis ê1 embedded in the proximal segment and chosen to represent flexion-extension, the "floating" axis ê2 chosen to represent ad-abduction, and the axis ê3 embedded in the distal segment and chosen to represent axial rotation of that segment. The algorithms for the JCS are then documented using generalized terminology.
Changes in KJL during the menstrual cycle do change knee joint loading during movements. Clinical Relevance Our findings will be beneficial for researchers in the development of more effective ACL injury prevention programs.
Female hormone levels are related to increased knee joint laxity and decreased stiffness at ovulation. To understand subject variations in knee joint laxity during the menstrual cycle in female athletes, further investigation is warranted.
ABSTRACT:The ovine stifle joint is a promising model for the investigation of joint mechanobiology in both normal and pathological states. The objectives of this study were to characterize threedimensional (3D) joint motion in the intact ovine stifle joint during walking, incline walking, and trotting; to determine the range of variability in normal joint motion (intrasubject and intersubject); and to characterize the 3D ground reaction forces in the ovine hind limb during walking. 3D in vivo kinematics were measured in the right hind limb of eight sheep during walking, incline walking, and trotting on a treadmill (accuracy: 0.4 AE 0.4 mm, 0.4 AE 0.48). 3D ground reaction forces were measured in the hind limbs of the same subjects during walking. Joint flexion ranged from 43.1 to 77.08, and was coupled with abduction (0.0-4.18), internal rotation (5.9-17.68), and translations in the medial (5.1-7.3 mm), anterior (21.9-23.8 mm), and superior (6.0-11.4 mm) directions. Kinematics were similar during walking, incline walking, and trotting. Intrasubject variability was small, ranging from 0.4-2.08 for rotations, and 0.4-0.5 mm for translations. The active range of joint motion was offset between subjects leading to intersubject variability of 4.1-7.48 for rotations and 2.5-4.2 mm for translations. Peak vertical ground reaction forces in the hind limbs ranged from 34.5(AE1.6) to 50.0(AE5.6)% body weight. This study establishes the bounds of normal motion in the intact ovine stifle joint and provides baseline data for further studies of joint mechanobiology in this model.
The classification and monitoring of individuals with early OA is an important strategy for the design and evaluation of therapeutic interventions. Such an approach requires the identification of appropriate outcomes measures. Potential outcome measures for early OA include patient-reported outcomes (such
This study aimed to estimate the reliability of 3-D trunk surface measurements for the characterization of external asymmetry associated with scoliosis. Repeated trunk surface acquisitions using the Inspeck system (Inspeck Inc., Montreal, Canada), with two different postures A (anatomical position) and B (''clavicle'' position), were obtained from patients attending a scoliosis clinic. For each acquisition, a 3-D model of the patient's trunk was built and a series of measurements was computed. For each measure and posture, intraclass correlation coefficients (ICC) were obtained using a bivariate analysis of variance, and the smallest detectable difference was calculated. For posture A, reliability was fair to excellent with ICC from 0.91 to 0.99 (0.85 to 0.99 for the lower bound of the 95% confidence interval). For posture B, the ICC was 0.85 to 0.98 (0.74 to 0.99 for the lower bound of the 95% confidence interval). The smallest statistically significant differences for the maximal back surface rotation was 2.5 and 1.5°for the maximal trunk rotation. Apparent global asymmetry and axial trunk rotation indices were relatively robust to changes in arm posture, both in terms of mean values and withinsubject variations, and also showed a good reliability. Computing measurements from cross-sectional analysis enabled a reduction in errors compared to the measurements based on markers' position.Although not yet sensitive enough to detect small changes for monitoring of curve natural progression, trunk surface analysis can help to document the external asymmetry associated with different types of spinal curves as well as the cosmetic improvement obtained after surgical interventions. The anatomical posture is slightly more reliable as it allows a better coverage of the trunk surface by the digitizing system.
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