The potential of an automated system to identify the upper limb component of a controlled sitting posture

Publication date: October 2017
Source:Gait & Posture, Volume 58
Author(s): María B. Sánchez, Ian Loram, John Darby, Paul Holmes, Penelope B. Butler
Full trunk control in sitting is demonstrated only when the head-trunk are aligned and upper limbs remain free of contact from mechanical support. These components represent a Controlled Kinetic Chain and can be evaluated in people with neuromotor disability using the Segmental Assessment of Trunk Control (SATCo) when a therapist provides manual trunk support at different segmental levels. However, the SATCo, as with other clinical assessments of control, is subjective. The SATCo was translated to objective rules relating the position of the hands and elbows to the head-trunk and then tested to determine the extent to which this automated objective method replicated the clinical judgement.Clinical evaluation used video to determine whether the upper limb was free of mechanical support while the objective evaluation used 3D motion capture of the trunk and upper limbs with a classification rule. The agreement between clinical and objective classification was calculated for three conditions of a distance-from-support-surface threshold parameter in five healthy adults and five children with cerebral palsy.The unfitted (zero-threshold values) method replicated the clinical judgement in part (68.26%±15.7, adults, 48.3%±33.9 children). The fitted (level-of-support determined) agreement showed that the process could be refined using trial specific parameters (88.32%±5.3 adults, 89.84%±10.2 children). The fixed-values agreement showed high values when using general group parameters (80.80%±3.1 adults, 74.31%±21.5 children).This objective classification of the upper limb component of trunk control largely captures the clinical evaluation. It provides the first stages in development of a clinically-friendly fully automated method.



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Predictive simulation of diabetic gait: Individual contribution of ankle stiffness and muscle weakening

Publication date: October 2017
Source:Gait & Posture, Volume 58
Author(s): Gilmar F. Santos, Aline A. Gomes, Isabel C.N. Sacco, Marko Ackermann
Diabetic neuropathic individuals present massive muscle strength reduction at the ankle plantar- and dorsiflexors and increased joint stiffness. Our aim is to investigate the adaptation strategies to these musculoskeletal alterations during walking by means of predictive simulations. We used a seven segment planar musculoskeletal model actuated by eight Hill-type muscles in each leg. The effect of all passive tissue in muscles and other joint structures was modeled by net passive joint moment curves. The predictive simulations were generated by solving an optimal control problem that minimized a cost function, including effort and tracking terms, using direct collocation and a commercial optimal control package. We simulate four conditions to represent the weakening of the distal muscles triceps sural (TS) and tibialis anterior (TA), and five conditions to represent the effect of increasing nonlinear ankle stiffness in flexion. The weakening of the distal muscles leads to a delayed action of the TS and a progressive decrease of the gastrocnemius peak force in the push-off phase. This distal deficit is compensated by a larger hip flexion moment resulting from an increase in the iliopsoas muscle force in this phase, known as the hip strategy. The adaptation mechanisms observed in response to an increase in ankle stiffness include the hip strategy and the exploitation of the passive joint structures as springs, which store energy during midstance and release it during push-off, reducing TS force and power in this phase and leading to a consistent decrease in the overall muscle force levels.



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In vivo kinematics of early-stage osteoarthritic knees during pivot and squat activities

Publication date: October 2017
Source:Gait & Posture, Volume 58
Author(s): Keisuke Matsuki, Kei O. Matsuki, Tomonori Kenmoku, Satoshi Yamaguchi, Takahisa Sasho, Scott A. Banks
Kinematic changes have been shown to accompany severe knee osteoarthritis, but no studies have analyzed early-stage osteoarthritic knee kinematics in the transverse plane during functional activities. The purpose of this study was to analyze kinematics of early-stage osteoarthritic knees using model registration techniques. Fifteen early-stage osteoarthritic knees from eight females with a mean age of 52 years old (range, 43–57years old) were involved in this study. A radiologist confirmed with plain radiographs that knees had Kellgren-Lawrence grade-1 or −2 arthritic changes. Fluoroscopic images of squat and pivot activities were recorded for each subject. Three-dimensional surface models of the distal femur and proximal tibia were created from CT images, and anatomic coordinate systems were embedded in each model. The three-dimensional position and orientation of the femur and the tibia were determined using model-image registration techniques, and tibial anteroposterior translation and internal/external rotation relative to the femur were calculated. The contact points of the medial and lateral femoral condyle were also computed. Compared to healthy knees, osteoarthritic knees showed lateral contact points that were significantly shifted anteriorly in both pivot (P<0.001) and squat (P=0.001) activities and greater tibial external rotation in pivot activity (P=0.007). The medial contact point location was similar to healthy knees, but the amount of anteroposterior translation was smaller (P<0.001). These kinematic changes might change stress distributions in the medial compartment during weight-bearing activities. The changes in kinematics possibly have some influence on initiation or progression of knee osteoarthritis.



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Foot strike pattern in children during shod-unshod running

Publication date: October 2017
Source:Gait & Posture, Volume 58
Author(s): Pedro Ángel Latorre Román, Fernando Redondo Balboa, Felipe García Pinillos
The purpose of this study was to determine the foot strike patterns (FSPs) and neutral support (no INV/EVE and no foot rotation) in children, as well as to determine the influence of shod/unshod conditions and sex. A total of 713 children, aged 6 to 16 years, participated in this study (Age=10.28±2.71years, body mass index [BMI]=19.70±3.91kg/m², 302 girls and 411 boys). A sagittal and frontal-plane video (240Hz) was recorded using a high-speed camcorder, to record the following variables: rearfoot strike (RFS), midfoot strike (MFS), forefoot strike (FFS), inversion/eversion (INV/EVE) and foot rotation on initial contact. RFS prevalence was similar between boys and girls in both shod and unshod conditions. In the unshod condition there was a significant reduction (p<0.001) of RFS prevalence both in boys (shod condition=83.95% vs. 62.65% unshod condition) and in girls (shod condition=87.85% vs. 62.70% unshod condition). No significant differences were found in INV/EVE and foot rotation between sex groups. In the unshod condition there was a significant increase (p<0.001) of neutral support (no INV/EVE) both in boys (shod condition=12.55% vs. 22.22% unshod condition) and in girls (shod condition=17.9% vs. 28.15% unshod condition). In addition, in the unshod condition there is a significant reduction (p<0.001) of neutral support (no foot rotation) both in boys (shod condition=21.55% vs. 11.10% unshod condition) and in girls (shod condition=21.05% vs. 11.95% unshod condition). In children, RFS prevalence is lower than adult’s population. Additionally, barefoot running reduced the prevalence of RFS and INV/EVE, however increased foot rotation.



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The potential of an automated system to identify the upper limb component of a controlled sitting posture

Publication date: October 2017
Source:Gait & Posture, Volume 58
Author(s): María B. Sánchez, Ian Loram, John Darby, Paul Holmes, Penelope B. Butler
Full trunk control in sitting is demonstrated only when the head-trunk are aligned and upper limbs remain free of contact from mechanical support. These components represent a Controlled Kinetic Chain and can be evaluated in people with neuromotor disability using the Segmental Assessment of Trunk Control (SATCo) when a therapist provides manual trunk support at different segmental levels. However, the SATCo, as with other clinical assessments of control, is subjective. The SATCo was translated to objective rules relating the position of the hands and elbows to the head-trunk and then tested to determine the extent to which this automated objective method replicated the clinical judgement.Clinical evaluation used video to determine whether the upper limb was free of mechanical support while the objective evaluation used 3D motion capture of the trunk and upper limbs with a classification rule. The agreement between clinical and objective classification was calculated for three conditions of a distance-from-support-surface threshold parameter in five healthy adults and five children with cerebral palsy.The unfitted (zero-threshold values) method replicated the clinical judgement in part (68.26%±15.7, adults, 48.3%±33.9 children). The fitted (level-of-support determined) agreement showed that the process could be refined using trial specific parameters (88.32%±5.3 adults, 89.84%±10.2 children). The fixed-values agreement showed high values when using general group parameters (80.80%±3.1 adults, 74.31%±21.5 children).This objective classification of the upper limb component of trunk control largely captures the clinical evaluation. It provides the first stages in development of a clinically-friendly fully automated method.



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Predictive simulation of diabetic gait: Individual contribution of ankle stiffness and muscle weakening

Publication date: October 2017
Source:Gait & Posture, Volume 58
Author(s): Gilmar F. Santos, Aline A. Gomes, Isabel C.N. Sacco, Marko Ackermann
Diabetic neuropathic individuals present massive muscle strength reduction at the ankle plantar- and dorsiflexors and increased joint stiffness. Our aim is to investigate the adaptation strategies to these musculoskeletal alterations during walking by means of predictive simulations. We used a seven segment planar musculoskeletal model actuated by eight Hill-type muscles in each leg. The effect of all passive tissue in muscles and other joint structures was modeled by net passive joint moment curves. The predictive simulations were generated by solving an optimal control problem that minimized a cost function, including effort and tracking terms, using direct collocation and a commercial optimal control package. We simulate four conditions to represent the weakening of the distal muscles triceps sural (TS) and tibialis anterior (TA), and five conditions to represent the effect of increasing nonlinear ankle stiffness in flexion. The weakening of the distal muscles leads to a delayed action of the TS and a progressive decrease of the gastrocnemius peak force in the push-off phase. This distal deficit is compensated by a larger hip flexion moment resulting from an increase in the iliopsoas muscle force in this phase, known as the hip strategy. The adaptation mechanisms observed in response to an increase in ankle stiffness include the hip strategy and the exploitation of the passive joint structures as springs, which store energy during midstance and release it during push-off, reducing TS force and power in this phase and leading to a consistent decrease in the overall muscle force levels.



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In vivo kinematics of early-stage osteoarthritic knees during pivot and squat activities

Publication date: October 2017
Source:Gait & Posture, Volume 58
Author(s): Keisuke Matsuki, Kei O. Matsuki, Tomonori Kenmoku, Satoshi Yamaguchi, Takahisa Sasho, Scott A. Banks
Kinematic changes have been shown to accompany severe knee osteoarthritis, but no studies have analyzed early-stage osteoarthritic knee kinematics in the transverse plane during functional activities. The purpose of this study was to analyze kinematics of early-stage osteoarthritic knees using model registration techniques. Fifteen early-stage osteoarthritic knees from eight females with a mean age of 52 years old (range, 43–57years old) were involved in this study. A radiologist confirmed with plain radiographs that knees had Kellgren-Lawrence grade-1 or −2 arthritic changes. Fluoroscopic images of squat and pivot activities were recorded for each subject. Three-dimensional surface models of the distal femur and proximal tibia were created from CT images, and anatomic coordinate systems were embedded in each model. The three-dimensional position and orientation of the femur and the tibia were determined using model-image registration techniques, and tibial anteroposterior translation and internal/external rotation relative to the femur were calculated. The contact points of the medial and lateral femoral condyle were also computed. Compared to healthy knees, osteoarthritic knees showed lateral contact points that were significantly shifted anteriorly in both pivot (P<0.001) and squat (P=0.001) activities and greater tibial external rotation in pivot activity (P=0.007). The medial contact point location was similar to healthy knees, but the amount of anteroposterior translation was smaller (P<0.001). These kinematic changes might change stress distributions in the medial compartment during weight-bearing activities. The changes in kinematics possibly have some influence on initiation or progression of knee osteoarthritis.



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