A Primer on Motion Capture with Deep Learning: Principles, Pitfalls, and Perspectives

A comprehensive assessment of the musculoskeletal system: The CAMS-Knee data set.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jor.24416

Kinematic Evaluation of the GMK Sphere Implant During Gait Activities: A Dynamic Videofluoroscopy Study

https://minerva-access.unimelb.edu.au/bitstream/handle/11343/275338/10.1002 jor.24613.pdf

Comparison of posterior‐stabilized, cruciate‐retaining, and medial‐stabilized knee implant motion during gait

Background: Walking patterns can provide important indications of a person’s health status and be beneficial in the early diagnosis of individuals with a potential walking disorder. For appropriate gait analysis, it is critical that natural functional walking characteristics are captured, rather than those experienced in artificial or observed settings. To better understand the extent to which setting influences gait patterns, and particularly whether observation plays a varying role on subjects of different ages, the current study investigates to what extent people walk differently in lab versus real-world environments and whether age dependencies exist. Methods: The walking patterns of 20 young and 20 elderly healthy subjects were recorded with five wearable inertial measurement units (ZurichMOVE sensors) attached to both ankles, both wrists and the chest. An automated detection process based on dynamic time warping was developed to efficiently identify the relevant sequences. From the ZurichMOVE recordings, 15 spatio-temporal gait parameters were extracted, analyzed and compared between motion patterns captured in a controlled lab environment (10m walking test) and the non-controlled ecologically-valid real-world environment (72 hours recording) in both groups. Results: Several parameters (Cluster A) showed significant differences between the two environments for both groups, including an increased outward foot rotation, step width, number of steps per 180° turn, stance to swing ratio, and cycle time deviation in the real-world. A number of parameters (Cluster B) showed only significant differences between the two environments for elderly subjects, including a decreased gait velocity (p=0.0072), decreased cadence (p=0.0051) and increased cycle time (p=0.0051) in real-world settings. Importantly, the real-world environment increased the differences in several parameters between the young and elderly groups. Conclusions: Elderly test subjects walked differently in controlled lab settings compared to their real-world environments, which indicates the need to better understand natural walking patterns under ecologically valid conditions before clinically relevant conclusions can be drawn on a subject’s functional status. Moreover, the greater inter-group differences in real-world environments seem promising regarding the sensitive identification of subjects with indications of a walking disorder.

/pdf/wearable-inertial-measurement-units-for-assessing-gait-in-4un544q4uq.pdf

Wearable Inertial Measurement Units for Assessing Gait in Real-World Environments.

Videofluoroscopy has been shown to provide essential information in the evaluation of the functionality of total knee arthroplasties. However, due to the limitation in the field of view, most systems can only assess knee kinematics during highly restricted movements. To avoid the limitations of a static image intensifier, a moving fluoroscope has been presented as a standalone system that allows tracking of the knee during multiple complete cycles of level- and downhill-walking, as well as stair descent, in combination with the synchronous assessment of ground reaction forces and whole body skin marker measurements. Here, we assess the ability of the system to keep the knee in the field of view of the image intensifier. By measuring ten total knee arthroplasty subjects, we demonstrate that it is possible to maintain the knee to within 1.8 ± 1.4 cm vertically and 4.0 ± 2.6 cm horizontally of the centre of the intensifier throughout full cycles of activities of daily living. Since control of the system is based on real-time feedback of a wire sensor, the system is not dependent on repeatable gait patterns, but is rather able to capture pathological motion patterns with low inter-trial repeatability.

/pdf/a-moving-fluoroscope-to-capture-tibiofemoral-kinematics-29tq1cy46j.pdf

A moving fluoroscope to capture tibiofemoral kinematics during complete cycles of free level and downhill walking as well as stair descent

Stability boots can protect the ankle ligaments from overloading after serious injury and facilitate protected movement in order to aid healing of the surrounding soft tissue structures. For comparing different stability shoe designs and prototypes, a reliable and fast testing method (FTM) is required. The aim of this study was to assess the reliability of a novel custom-built device. Six different stability boots were tested in a novel device that allowed body weight to be taken into account using a pneumatic actuator. The fixation of the boots was controlled using two air pad pressure sensors. The range of motion (RoM) was then assessed during 5 trials at physiological ankle joint torques during flexion/extension and inversion/eversion. Furthermore the intraclass correlation coefficient ICC was determined to assess the repetitive reliability of the testing approach. The measured ankle angles ranged from 3.4° to 25° and proved to be highly reliable (ICC = 0.99), with standard deviations <9.8%. Comparing single trials to one another resulted in a change of 0.01° joint angle, with a mean error of 0.02°. The FTM demonstrates that it is possible to reliably measure the ankle joint RoM in both the sagittal and frontal planes at controlled torque levels, together with the application of body weight force.

/pdf/a-fast-testing-method-to-objectively-quantify-the-stiffness-2wksykksfi.pdf

A Fast Testing Method to Objectively Quantify the Stiffness of Stability Boots

Linear actuators are a key element of automatized industrial systems, as linear motion is present in most manipulation tasks. For actuators performing x-z movements, actuator windings are placed on the moving part and these must be supplied. However, in high-purity environments such as in the food processing or pharmaceutical industries, actuators should be fully enclosed in stainless steel (SS) to facilitate thorough cleaning, and cables are undesirable. This paper therefore proposes high-efficiency (97% at 100W) wireless power transfer (WPT) through two 0.5mm thick SS enclosures, which facilitates the deployment of linear actuators in high-purity environments. The proposed coaxial transformer arrangement with the magnetic core mounted on the moving part results in a magnetic field that is in parallel to the SS enclosures, which minimizes eddy-current losses. We discuss the detailed modeling and optimization of the system, and finally present an industrial two-axis actuator prototype that fully confirms the theoretical analysis.

Wireless Power Supply of Moving Linear Actuator Enclosed in Stainless-Steel

The aim of the study was to validate indigenously designed novel state-of-the-art wearable sensor technology (WST), the JUMP modules, against a more conventional optical motion tracking system. 16 healthy young participants were requested to walk at three different walking speeds (slow, normal and fast). Bland-Altman analysis revealed high — excellent levels of agreement for all the parameters, with stride time as well as stride time variability showing the highest levels of agreement as well as precision. The results indicate that the novel WST system is a valid tool for monitoring both summary gait as well as gait variability parameters, and therefore has the potential to accurately monitor motor-related deficits in patients as well as elderly adults in clinical settings.

Marco Hitz

Papers

A comprehensive assessment of the musculoskeletal system: The CAMS-Knee data set.

A moving fluoroscope to capture tibiofemoral kinematics during complete cycles of free level and downhill walking as well as stair descent

A Fast Testing Method to Objectively Quantify the Stiffness of Stability Boots

Wireless Power Supply of Moving Linear Actuator Enclosed in Stainless-Steel

Achieving ecological validity in mobility assessment: Validating a wearable sensor technology for comprehensive gait assessment