The purpose of this study is to create an accurate experimental database for the passive (in vitro)freedom-of-motion characteristics of the human knee joint on a subject to subject basis, suitable for the verification and enhancement of mathematical knee-joint models. Knee-joint specimens in a six degree-of-freedom motion rig are moved through flexion under several combinations of external loads, including tibial torques, axial forces and AP-forces. Euler rotation angles and translation vectors, describing the relative, spatial motions of the joint are measured using an accurate Roentgen Stereo Photogrammetric system. Conceptually the joint is considered as a two degrees-of-freedom of motion mechanism (flexion-tibial rotation), whereby the limits of internal and external tibial rotation are defined at torques of ± 3 Nm. The motion pathways along these limits are denned as the envelopes of passive knee joint motion. It is found that these envelope pathways are consistent and hardly influenced by additional axial forces up to 300 N and AP-forces of 30 N. Within the envelope of motion, however, the motion patterns are highly susceptible to small changes in the external load configuration. It is shown that the external tibial rotation during extension ('screw-home mechanism') is not an obligatory effect of the passive joint characteristics, but a direct result of the external loads. Anatomical differences notwithstanding, the inter-individual discrepancies in the motion patterns of the four specimens tested, showed to be relatively small in a qualitative sense. Quantitative differences can be explained by small differences in the alignment of the coordinate systems relative to the joint anatomy and by differences in rotatory laxity.
DOCUMENT
AbstractIn many biomechanical motion studies, kinematic parameters are estimated from position measurements on a number of landmarks. In the present investigation, dummy motion experiments are performed in order to study the error dependence of kinematic parameters on geometric factors (number of markers, isotropic vs anisotropic landmark distributions, landmark distribution size), on kinematic factors (rotation step magnitude, the presence of translational displacements, the distance of the landmarks' mean position to the rotation axis), and on anisotropically distributed measurement errors. The experimental results are compared with theoretical predictions of a previous error analysis assuming isotropic conditions for the measurement errors and for the spatial landmark distribution. In general, the experimental findings agree with the predictions of the error model. The kinematic parameters such as translations and rotations are well-determined by the model. In the helical motion description, the same applies for the finite rotation angle about and the finite shift along the helical axis. However, the direction and position of the helical axis are ill-determined. An anisotropic landmark distribution with relatively few markers located in the direction of the rotation axis will even aggravate the ill-posed nature of the finite helical axis estimation.
DOCUMENT
BackgroundIdiopathic Toe Walking (ITW) is present in children older than 3 years of age still walking on their toes without signs of neurological, orthopaedic or psychiatric diseases. ITW has been estimated to occur in 7% to 24% of the childhood population. To study associations between Idiopathic Toe Walking (ITW) and decrease in range of joint motion of the ankle joint. To study associations between ITW (with stiff ankles) and stiffness in other joints, muscle strength and bone density.MethodsIn a cross-sectional study, 362 healthy children, adolescents and young adults (mean age (sd): 14.2 (3.9) years) participated. Range of joint motion (ROM), muscle strength, anthropometrics sport activities and bone density were measured.ResultsA prevalence of 12% of ITW was found. Nine percent had ITW and severely restricted ROM of the ankle joint. Children with ITW had three times higher chance of severe ROM restriction of the ankle joint. Participants with ITW and stiff ankle joints had a decreased ROM in other joints, whereas bone density and muscle strength were comparable.ConclusionITW and a decrease in ankle joint ROM might be due to local stiffness. Differential etiological diagnosis should be considered.
MULTIFILE
INTRODUCTION: The aim of this study was to determine the degree of ROM limitations of extremities, joints and planes of motion after burns and its prevalence over time.METHOD: The database of a longitudinal multicenter cohort study in the Netherlands (2011-2012) was used. From patients with acute burns involving the neck, shoulder, elbow, wrist, hip, knee and ankle joints that had surgery, ROM of 17 planes of motion was assessed by goniometry at 3, 6 weeks, 3-6-9 and 12 months after burns and at discharge.RESULTS: At 12 months after injury, 12 out of 17 planes of motion demonstrated persistent joint limitations. The five unlimited planes of motion were all of the lower extremity. The most severely limited joints at 12 months were the neck, ankle, wrist and shoulder. The lower extremity was more severely limited in the early phase of recovery whereas at 12 months the upper extremity was more severely limited.CONCLUSION: The degree of ROM limitations and prevalence varied over time between extremities, joints and planes of motion. This study showed which joints and planes of motion should be watched specifically concerning the development of scar contracture.
DOCUMENT
The wrist allows the hand to combine dorsopalmar flexion and radioulnar deviation, a unique combination of functions that is made possible by a highly complex system of joints. The morphologic features of the carpal bones and of the radiocarpal and intercarpal contacts can be functionally interpreted by the mechanism that underlies the movements of the hand to the forearm. Displacements of the carpals take place in longitudinal articulation chains, with the proximal carpals having the position of an intercalated bone. The three articulation chains, radial, central, and ulnar, have interdependent movements at the radiocarpal and midcarpal levels. The linkage of movements in the longitudinal direction is associated to a transverse linkage by mutual joint contacts and by specific ligamentous interconnections. Kinematic analyses of the carpal joint motions have provided convincing evidence that each motion of the hand to the forearm demonstrates a specific motion pattern of the carpal bones. The stability of the carpus essentially depends on the integrity of the ligamentous system which consists of interwoven fiber bundles that differ in length, direction, and mechanical properties. Distinct separations into morphologic entities are difficult to make. From a functional point of view, the ligamentous interconnections can be regarded as a system that passively restricts movements of the carpals on one another and on the radius, but in a very differentiated way. The ligamentous system controls the linkage of the movements of the carpals, with the geometries of the bones and of the joint surfaces being, first of all, responsible for the kinematic behavior of the carpal joint.
DOCUMENT
The purpose of this study was to investigate the influence of body function, activities and pain on the level of activity in adults with Kashin Beck Disease (KBD). Seventy-five KBD patients with a mean age of 54.8 years (SD 11.3) participated. Anthropometrics, range of joint motion (ROM) and muscle strength were measured as well as the time-up-and-go test and functional tests for the lower and upper extremities. Activity was assessed with the participation scale and the WHO DAS II. In the shoulder, elbow, hip and knee joints, a severe decrease in ROM and bilateral pain was noted. A decrease in muscle strength was observed in almost all muscles. The timed-up-and-go test scores decreased. No or mild restriction in activity was found in 35%, and 33% experienced a moderate restriction whereas 32% had severe to extreme restriction. Activities in the lower extremities were mildly to moderately correlated to ROM and muscle strength, whereas in the upper extremities activities were correlated to range of joint motion. Activity was significantly associated with ROM after correction for muscle strength, gender and age. Participation was borderline significantly associated with ROM after correction for muscle strength, gender, age and the activity time-up-and-go. In KBD adults, a severe decrease in activity is primarily caused by decrease in ROM. These findings have strong influence on rehabilitation and surgical intervention.
DOCUMENT
In biomechanical joint-motion analyses, the continuous motion to be studied is often approximated by a sequence of finite displacements, and the Finite Helical Axis(FHA) or "screw axis" for each displacement is estimated from position measurements on a number of anatomical or artificial landmarks. When FHA parameters are directly determined from raw (noisy) displacement data, both the position and the direction of the FHA are ill-determined, in particular when the sequential displacement steps are small. This implies, that under certain conditions, the continuous pathways of joint motions cannot be adequately described. The purpose of the present experimental study is to investigate the applicability of smoothing (or filtering)techniques, in those cases where FHA parameters are ill-determined. Two different quintic-spline smoothing methods were used to analyze the motion data obtained with Roentgenstereophotogrammetry in two experiments. One concerning carpal motions in a wrist-joint specimen, and one relative to a kinematic laboratory model, in which the axis positions are a priori known. The smoothed and nonsmoothed FHA parameter errors were compared. The influences of the number of samples and the size of the sampling interval (displacement step) were investigated, as were the effects of equidistant and nonequidistant sampling conditions and noise invariance
DOCUMENT
This paper describes the work that is done by a group of I3 students at Philips CFT in Eindhoven, Netherlands. I3 is an initiative of Fontys University of Professional Education also located in Eindhoven. The work focuses on the use of computer vision in motion control. Experiments are done with several techniques for object recognition and tracking, and with the guidance of a robot movement by means of computer vision. These experiments involve detection of coloured objects, object detection based on specific features, template matching with automatically generated templates, and interaction of a robot with a physical object that is viewed by a camera mounted on the robot.
DOCUMENT
Knee joint instability is frequently reported by patients with knee osteoarthritis (KOA). Objective metrics to assess knee joint instability are lacking, making it difficult to target therapies aiming to improve stability. Therefore, the aim of this study was to compare responses in neuromechanics to perturbations during gait in patients with self-reported knee joint instability (KOA-I) versus patients reporting stable knees (KOA-S) and healthy control subjects.Forty patients (20 KOA-I and 20 KOA-S) and 20 healthy controls were measured during perturbed treadmill walking. Knee joint angles and muscle activation patterns were compared using statistical parametric mapping and discrete gait parameters. Furthermore, subgroups (moderate versus severe KOA) based on Kellgren and Lawrence classification were evaluated.Patients with KOA-I generally had greater knee flexion angles compared to controls during terminal stance and during swing of perturbed gait. In response to deceleration perturbations the patients with moderate KOA-I increased their knee flexion angles during terminal stance and pre-swing. Knee muscle activation patterns were overall similar between the groups. In response to sway medial perturbations the patients with severe KOA-I increased the co-contraction of the quadriceps versus hamstrings muscles during terminal stance.Patients with KOA-I respond to different gait perturbations by increasing knee flexion angles, co-contraction of muscles or both during terminal stance. These alterations in neuromechanics could assist in the assessment of knee joint instability in patients, to provide treatment options accordingly. Furthermore, longitudinal studies are needed to investigate the consequences of altered neuromechanics due to knee joint instability on the development of KOA.
DOCUMENT
Inertial measurement units (IMUs) allow for measurements of kinematic movements outside the laboratory, persevering the athlete-environment relationship. To use IMUs in a sport-specific setting, it is necessary to validate sport-specific movements. The aim of this study was to assess the concurrent validity of the Xsens IMU system by comparing it to the Vicon optoelectronic motion system for lower-limb joint angle measurements during jump-landing and change-of-direction tasks. Ten recreational athletes performed four tasks; single-leg hop and landing, running double-leg vertical jump landing, single-leg deceleration and push off, and sidestep cut, while kinematics were recorded by 17 IMUs (Xsens Technologies B.V.) and eight motion capture cameras (Vicon Motion Systems, Ltd). Validity of lower-body joint kinematics was assessed using measures of agreement (cross-correlation: XCORR) and error (root mean square deviation and amplitude difference). Excellent agreement was found in the sagittal plane for all joints and tasks (XCORR > 0.92). Highly variable agreement was found for knee and ankle in transverse and frontal plane. Relatively high error rates were found in all joints. In conclusion, this study shows that the Xsens IMU system provides highly comparable waveforms of sagittal lower-body joint kinematics in sport-specific movements. Caution is advised interpreting frontal and transverse plane kinematics as between-system agreement highly varied.
DOCUMENT
