- A linear soft tissue artefact model for human movement analysis A linear soft tissue artefact model for human movement analysis:
- Analysis of skeletal motion kinematics for a knee movement cycle "This study estimated the skeletal motion for a knee motion cycle. The surface markers on the thigh and the shank showed the computed displacement during in vivo motion analysis. This error was minimized using optimization procedure. The displacement was generally greater on the thigh than the shank. The minimization of error produced by this procedure was more successful on the thigh than the shank. The purpose of his study was to require high value motion data. These results provide the basis to calculate the instantaneous knee axis of rotation in a follow up study."
- Bone orientation and position estimation errors using Cosserat point elements Bone orientation and position estimation errors using Cosserat point elements and least squares methods: Application to gait "The aim of this study was to analyze the accuracy of bone pose estimation based on sub-clusters of three skin-markers characterized by triangular Cosserat point elements (TCPEs) and to evaluate the capability of four instantaneous physical parameters, which can be measured non-invasively in vivo, to identify the most accurate TCPEs. Moreover, TCPE pose estimations were compared with the estimations of two least squares minimization methods applied to the cluster of all markers, using rigid body (RBLS) and homogeneous deformation (HDLS) assumptions. Analysis was performed on previously collected in vivo treadmill gait data composed of simultaneous measurements of the gold-standard bone pose by bi-plane fluoroscopy tracking the subjects’ knee prosthesis and a stereophotogrammetric system tracking skinmarkers affected by soft tissue artifact."
- Can hip and knee kinematics be improved by eliminating thigh markers? "This study presents a comparison of hip and knee kinematics as calculated by five concurrently worn tracking marker sets during eight different tasks. The first three marker sets were based on Helen Hayes but used (1) proximal thigh wands, (2) distal thigh wands, and (3) patellar markers instead of thigh wands. The remaining two marker sets used rigid clusters on the (4) thighs and shanks and (5) only shanks. Pelvis and foot segments were shared by all marker sets."
- Comparison of surface mounted markers Comparison of surface mounted markers and atachment methods in estimating tibial rotations during walking: an in vivo study
Proof of concept using in vivo data
"We investigated the accuracy of a linear soft tissue artefact (STA) model in human movement analysis. Simultaneously recorded bone-mounted pin and skin marker data for the thigh and shank during walking, cutting and hopping were used to measure and model the motion of the skin marker clusters within anatomical reference frames (ARFs)."
- In Vivo Knee Kinematics during Gait In Vivo Knee Kinematics during Gait Reveals New Rotation Profiles and Smaller Translations
- Inﬂuence of thigh cluster conﬁguration on the estimation of hip axial rotation "The non-invasive estimation of hip axial rotation is prone to error. Most of this is likely to originate from soft tissue artefact (STA) at the thigh. The purpose of this study was to evaluate the relative performance of four different thigh cluster conﬁgurations. Three were novel conﬁgurations whilst one represented the Helen Hayes convention."
- Knee moment profiles during walking Knee moment profiles during walking: errors due to soft tissue movement of the shank and the influence of the reference coordinate system
- Non-invasive assessment of soft-tissue artifact Non-invasive assessment of soft-tissue artifact and its effect on knee joint kinematics during functional activity
"In order to identify abnormal or pathological motions associated with clinically relevant questions such as injury mechanisms or factors leading to joint degeneration, it is essential to determine the range of normal tibiofemoral motion of the healthy knee. In this study we measured in vivo 3D tibiofemoral motion of the knee during gait and characterized the nonsagittal plane rotations and translations in a group of six healthy young adults."
"The soft-tissue interface between skin-mounted markers and the underlying bones poses a major limitation to accurate, non-invasive measurement of joint kinematics. The aim of this study was twofold: first, to quantify lower limb soft-tissue artifact in young healthy subjects during functional activity; and second, to determine the effect of soft-tissue artifact on the calculation of knee joint kinematics."
- On the influence of soft tissue coverage On the inﬂuence of soft tissue coverage in the determination of bone kinematics using skin markers
- Quantiﬁcation of soft tissue artifact in lower limb human motion analysis: A systematic review "This systematic review critically evaluates the quantiﬁcation of soft tissue artifact (STA) in lower limb human motion analysis. It has a speciﬁc focus on assessing the quality of previous studies and comparing quantitative results."
- Soft tissue artifact assessment and compensation Human movement analysis using stereophotogrammetry
- Strategy for minimising soft tissue artefact at the tibia "The aim of this study is to identify a subset of markers on the tibia showing the least amount of movement with respect to each other."
"Accurate measurement of underlying bone positions is important for the understanding of normal movement and function, as well as for addressing clinical musculoskeletal or post-injury problems. Non-invasive measurement techniques are limited by the analysis technique and movement of peripheral soft tissues that can introduce signiﬁcant measurement errors in reproducing the kinematics of the underlying bones when using external skin markers. Reﬂective markers, skeletally mounted to the right hind limb of three Merino-mix sheep were measured simultaneously with markers attached to the skin of each segment, during repetitions of gait trials. The movement of the skin markers relative to the underlying bone positions was then assessed using the Point Cluster Technique (PCT), raw averaging and the Optimal Common Shape Technique (OCST), a new approach presented in this manuscript."
Part 3. Soft tissue artifact assessment and compensation
- Tibiofemoral and tibiocalcaneal motion during walking Tibiofemoral and tibiocalcaneal motion during walking: external vs. skeletal markers
- Towards a marker-less human gait analysis system A non–invasive system is described which is capable of extracting and describing the three–dimensional nature of human gait thereby extending the use of gait as a biometric.
- Towards a no-thigh markers protocol of gait analysis "An attempt to reduce the need for markers on the thigh is being carried out by modelling the knee joint constraints. By using MRI and fluoroscopy, the relative movements of femur, tibia and patella were captured in vivo during knee flexion. The length and orientation of cruciate ligaments were identified all along the range of movement. This information was then used in a four-bar, variablelength linkage model of the tibio-femoral connection. By knowing the location of the hip joint centre (fixed within the pelvis) and the shank in space, the rotation of the thigh can be determined from geometrical relationships. Preliminary results show that knee joint kinematic estimation errors are less than those due to markers being affected by skin artefacts."
Skin Deformation Measurements:
- Capturing and Animating Skin Deformation in Human Motion "During dynamic activities, the surface of the human body moves in many subtle but visually significant ways: bending, bulging, jiggling, and stretching. We present a technique for capturing and animating those motions using a commercial motion capture system and approximately 350 markers."
- Continuous Capture of Skin Deformation "We describe a method for the acquisition of deformable human geometry from silhouettes. Our technique uses a commercial tracking system to determine the motion of the skeleton, then estimates geometry for each bone using constraints provided by the silhouettes from one or more cameras."
- Estimating joint kinematics from skin motion observation: modelling and validation "Modelling of soft tissue motion is required in many areas, such as computer animation, surgical simulation, 3D motion analysis and gait analysis. In this paper, we will focus on the use of modelling of skin deformation during 3D motion analysis."
- Influence of soft tissue artifacts "Influence of soft tissue artifacts on the calculated kinematics and kinetics of total knee replacements during sit-to-stand
- Quantification of soft tissue artefact in motion analysis Quantification of soft tissue artefact in motion analysis by combining 3D fluoroscopy and stereophotogrammetry: a study on two subjects
- Soft tissue motion measurement Soft tissue motion measurement on shank and thigh with MRI
- Visualization of Local Movements for optimal Marker Positioning "In this paper we exploit a local fitting tool to visualize the influence of skin deformation on marker movements. Such a knowledge can in turn improve the layout of optical markers. We illustrate our viewpoint on motions of the upper-torso."
The current study aimed to quantify the soft tissue artifacts of selected markers on the thigh and shank, and their effects on the calculated joint center translations, angles and moments of the knee during sitto-stand. Ten patients with total knee replacements rose from a chair under simultaneous surveillance of a motion capture system, a force-plate and a fluoroscopy system."
"Two subjects, treated by total knee replacement, underwent data acquisition simultaneously with fluoroscopy and stereophotogrammetry during stair climbing, step up/down, sit-to-stand/stand-to-sit, and extension against gravity. The reference 3D kinematics of the femur and tibia was reconstructed from fluoroscopy-based tracking of the relevant prosthesis components. Soft tissue artefact was quantified as the motion of a grid of retro-reflecting makers attached to the thigh and shank with respect to the underlying bones, tracked by optoelectronic stereophotogrammetry. The propagation of soft tissue artefact to knee rotations was also calculated."
- Improved tracking of hip rotation using a patella marker "A marker placed on the patella allows for more accurate measurement of hip rotations than traditional thigh wands. In controlled trials of isolated hip internal-external rotation, the patella marker detected 97% of the actual range of motion, compared with 59% for a distal thigh wand and 41% for a proximal thigh wand."
- Use of a patella marker to improve traking of dynamic hip rotation range of motion "This study investigated effectiveness of a patella marker in tracking hip rotation range of motion in comparison with traditional thigh wands. In controlled trials of isolated hip internal–external rotation, the patella marker detected 98 +/- 8% of the actual range of motion, compared with 53 +/- 10% for a distal thigh wand and 43 +/- 13% for a proximal thigh wand. The patella marker produced the smoothest hip rotation curves and the smallest hip rotation range in walking, and results from the patella marker did not depend on walking speed."
- Comparison of a thigh wand versus a patella marker The effect of static standing posture on dynamic walking kinematics: Comparison of a thigh wand versus a patella marker
Pelve - Pelvis:
- Alternative modelling procedures for pelvic marker occlusion during motion analysis "Motion analysis of participants with different body shapes under diverse conditions can be problematic when vitalmarkers are occluded. The markers located over the anterior superior iliac spines are commonly occluded in older patients and during analysis of activities with trunk and hip flexion which can prevent accurate calculation of lower limb joint kinematics. Options to modify standard body models exist but have not been described in detail, and the effects on the lower limb kinematics are not known."
- Evaluation of alternative technical markers for the pelvic coordinate system "In this study, we evaluated alternative technical markers for the motion analysis of the pelvic segment."
- Quantification of pelvic soft tissue artifact in multiple static positions "Soft tissue artifact (STA) has been identified as the most critical source of error in clinical gait analysis. Multiple calibration is a technique to reduce the impact of STA on kinematic data, which involves several static calibrations through the range of motion of the joint of interest. This study investigated how skin markers at the pelvis were displaced in relation to anatomical body landmarks in multiple static calibration positions."
- Soft tissue displacement over pelvic anatomical landmarks during 3-D hip movements "The position, in a pelvis-embedded anatomical coordinate system, of skin points located over the following anatomical landmarks (AL) was determined while the hip assumed different spatial postures: right and left anterior superior and posterior superior iliac spines, and the sacrum. Postures were selected as occurring during walking and during a flexion–extension and circumduction movement, as used to determine the hip joint centre position (star-arc movement). Five volunteers, characterised by a wide range of body mass indices (22–37), were investigated. Subject-specific MRI pelvis digital bone models were obtained. For each posture, the pose of the pelvis-embedded anatomical coordinate system was determined by registering this bone model with points digitised over bony prominences of the pelvis, using a wand carrying a marker-cluster and stereophotogrammetry."