Biomechanics and Gait Testing of ONYX Exoskeleton

Grants and Contracts Details


Statement of Work [SOW] HJF PI Name: Betty Crosby Site PI Collaborator’s Name: Dr. Junfei Tong Subaward Title: Dr. Brian Noehren at the University of Kentucky Stratification of Musculoskeletal Injury Risk from Prolonged Date/Revision # Use of Wearable Exoskeleton Suits May 24, 2021 I. INTRODUCTION/BACKGROUND: Dr. Junfei Tong, located at the Biotechnology High Performance Computing Software Applications Institute (BHSAI), conducts research in the field of musculoskeletal injuries, and is performing studies under prime award W81XWH-20-C-0031 to specifically study the impact of prolonged use of exoskeleton on the lower extremities and lower back. Dr. Junfei Tong will utilize the technical expertise of Dr. Brian Noehren and the University of Kentucky to meet the objectives identified in the above mentioned study. Specifically, Dr. Noehren will serve as the collaborator for this study and be responsible for ensuring recording and preparation of computed tomography (CT), motion-capture, electromyography (EMG), and metabolic cost data in males during walking with and without load carriage, with and without exoskeleton. BHSAI will utilize these experimental data as inputs for musculoskeletal finite element models to estimate tibia and lumbar spines strain metrics in males, as part of a larger effort to predict the stress-fracture risk at the tibia. Dr. Noehren is the director of the Human Performance and Biomotion Laboratories. Since starting at the University of Kentucky in 2009, he has worked closely with the Department of Orthopedic Surgery to develop a focused research program on lower extremity injuries. The Human Performance and Biomotion Laboratories embody translational science with investigators from the colleges of Health Sciences, Education, Medicine, and Engineering working side by side on projects ranging from mechanistic studies in biomechanics to cutting- edge physical therapy treatments. The laboratory occupies approximately 1,365 square feet on the first floor and contains space dedicated to evaluating biomechanics across activities ranging from basic tasks such as transitioning between sit-to-stand, to advanced tasks such as performing a running cut motion at full speed. Laboratory also has outstanding laboratory equipment to support diverse research activities, including 22 Raptor cameras, two 16-bit A-D boards, a Bertec split-belt instrumented treadmill with dual force plates, 16 channel Delsys EMG system (Boston, MA), and 2 Bertec force plates for overground data collections. The overall objective of this project is to quantify the impacts of prolonged use of exoskeleton on the biomechanics of the lower extremity and lower back. This knowledge will help inform the safe and effective use of wearable exoskeleton devices. Significance: The exoskeleton is a promising device that has the potential to enhance Soldier strength and endurance [1]. For example, lower-body exoskeleton suits allow Soldiers to carry a 200-lb load 1 while marching at a speed of 4 km/h for up to 20 km [1]. However, preliminary experimental studies on such suits suggest that the use of exoskeleton can drastically affect the walking-gait motion and body forces (i.e., kinematics and kinetics), even during short marching periods without additional load [2,3]. Importantly, such gait-related changes may lead to unintended musculoskeletal injuries, for example, in the lower extremities [4] or in the lower back [5]. Yet, to date, we do not know the impact of the prolonged use of exoskeleton suits. For example, it is unclear what part of the human body is most vulnerable to prolonged use of a lower-body exoskeleton. Further, it remains to be determined what impact load carriage and marching distance would have in exoskeleton-induced injuries. II. TECHNICAL REQUIREMENTS: The following tasks will be performed by Dr. Brian Noehren at the University of Kentucky to meet the objectives listed above. Study design: For this study we will recruit 5 males from the University of Kentucky. This project would require each individual to have four visits to the lab. To assure that the study participants are representative of Army recruits in Basic Combat Training, we will recruit participants whose ages range from 18 to 25 years [5]. The students in the Reserve Officer Training Corps (ROTC) program will be prioritized for this recruitment if possible. Inclusion criteria: o Males o Age 18-25 years o Body size fit with the exoskeleton device o Free from injuries that would have limited their ability to be physically active for 3 months prior to study participation o Experience with treadmill walking Major tasks that will occur during Phase 1 of the protocol: Phase 1 will use significant lab resources and time to plan, pilot test and execute the testing protocol to be used. To ensure the highest quality data, we will extensively pilot test the proposed experimental procedures, develop detailed standard operating procedures, and complete the required regulatory paperwork for the Institutional Review Board (IRB) and Human Research Protection Office (HRPO). We have outlined major steps below: Human subjects protections: 1) Complete informed consent document and have the protocol reviewed through a full board review at the University of Kentucky. Make any requested changes and have full board approval 2) Submit protocol to HRPO and complete all regulatory paperwork for approval Pilot testing: 1) The data collections will result in occlusion of many markers and we will do extensive pilot testing of multiple solutions to able to track the trunk and tibia which 2 we suspect will be occluded. This will include testing different backpack designs, marker placement, developing new marker attachment points on the backpack and exoskeleton. 2) The data collections will require carrying a heavy load for an extended period of time. It is unknown how well the backpacks will endure for such a period of time and if they will be tolerable on the research subjects. We will test several designs selecting the one that fits the best on subjects to help ensure adherence and completion of the testing protocol. 3) The data collections will result in prolonged tracking of EMG and markers. We will test EMG placement and the ability of the EMG to record during high exertion and sweaty conditions. 4) We will also test and evaluate the data export, formatting and signal quality both internally and through collaboration with Dr. Tong at BHSAI through sharing of early data. Data to be checked include marker trajectories, EMG signal, force data, anthropometric data. 5) We will need to test systems to ensure subject engagement during the prolonged walk to facilitate completing the task. To do this we plan to offer the subjects both music and videos that they can watch while performing the task to help them stay motivated to finish. The optimal place to put such feedback in the lab environment, how to set it up, volume, and ensuring that it does not occlude markers from the cameras needs to be determined. 6) The exoskeleton will need to be extensively tested. The mode of operation, fit, recharging, are all unknown and would need to be investigated prior to use on subjects. 7) We will need to develop detailed checklists of standard operating procedures and data collection forms to be used. 8) New computational models within the data collection computer to collect new models will need to be developed. We will test optimal fit to track markers to minimize any gaps. 9) We will need to conduct run through’ s with both the pack and the exoskeleton to check how the participant responds to the intervention through monitoring with a heart rate monitor and taking ratings of perceived exertion during the testing. 10) We will start to establish relationships within the community and campus to get the word out about the study and identify where and what groups to recruit from once we are approved to start recruitment. 11) The metabolic testing will need to be pilot tested within the lab to ensure that it does not block other equipment and is tolerable for the subject with everything else attached to them. 12) Proper prep and post collection disinfecting and cleaning of exoskeletons, backpacks and other equipment used for this experiment will need to be established. 13) We will conduct a mock run through of the CT scan with the radiology to ensure they have everything they need to perform the tests once the subjects start being recruited. 14) We will identify the optimal minimum time between collections that subjects are no longer sore for follow up collections for the actual trial. 15) We will evaluate the learning effect of use of the exoskeleton and repeated wearing of the backpack. 3 Protocol – RQ1: 1. Visit 1: For each participant, we will acquire anthropometric measurements including fat percent, height, weight, tibial length, and Q-angle. Participants will walk at their preferred speed for a 5-km distance without an exoskeleton carrying no load. Motion- capture data, electromyography (EMG) data, and ground reaction force will be collected for 20 seconds at baseline and at each 1-km mark. Metabolic cost data will be collected throughout the whole walking process. 2. Visit 2: This visit will be used to acclimate the participant to the use of the exoskeleton and fit him to the backpack. Subjects will be fitted with the exoskeleton and undergo a standardized period of instruction followed by use of the exoskeleton while walking on the treadmill. Subjects may practice walking for up to 30 minutes. In addition, during this visit, the subject will also be fitted for the backpack they will use during testing. Adjustments in the overall fit of the backpack will be made to help ensure subject comfort to improve compliance with completing the testing. 3. Visit 3: Participants will receive CT scans of the tibia and lumbar vertebrae L4 and L5. Similar to Visit 1, participants will walk at their preferred speed for a 5-km distance without an exoskeleton carrying a 70-lb load. Motion-capture data, EMG data, and ground reaction force will be collected for 20 seconds at baseline and at each 1-km mark. Metabolic cost data will be collected throughout the whole walking process. 4. Visit 4: Participants will walk at their preferred speed for a 5-km distance with an exoskeleton carrying no load. Motion-capture data, EMG data, and ground reaction force will be collected for 20 seconds at baseline and at each 1-km mark. Metabolic cost data will be collected throughout the whole walking process. 5. Visit 5: Participants will walk at their preferred speed for a 5-km distance with an exoskeleton carrying a 70-lb load. Motion-capture data, EMG data, and ground reaction force will be collected for 20 seconds at baseline and at each 1-km mark. Metabolic cost data will be collected throughout the whole walking process. Global Methods Prolonged walking Before each experiment, we will conduct static trials to establish segmental coordinate systems. We will also do a rigorous force platform calibration. To collect motion-capture data, retroreflective markers will be placed on anatomical landmarks and segments of the participant’s whole-body. Markers will be tracked using a camera motion analysis system while participants walk on an instrumented treadmill. Motion-capture (Motion Analysis Corp, Santa Rosa, CA) and ground reaction forces from an instrumented treadmill (Bertec, Columbus, OH) data will be collected at sampling frequencies of 200 and 1200 Hz, respectively. If it is difficult to recruit participants to successfully complete the 5km walking with a 70-lb load in the pilot study, we will reduce the load carriage to 50 lb. A 52 reflective marker set will be fitted on each subject’s 4 lower extremity and trunk to track each Figure 1: Standardized marker set for initial segment during the walking task (Figure 1). calibration of anatomical markers. Note, Twenty-seven of the markers were placed on marker set may be modified during pilot anatomical landmarks including sternal testing to best optimize data collection with notch, spinous process of C7, bilateral exoskeleton and backpack on. superior acromion processes, bilateral superior iliac crests, posterior L5/S1 vertebral joint, bilateral greater trochanters, bilateral medial and lateral distal femurs, bilateral medial and lateral distal proximal tibias, bilateral medial and lateral malleoli, bilateral first and fifth metatarsal heads, and bilateral distal foot. Sixteen tracking markers were attached including four rigid plates secured to bilateral thigh and shank with four markers on each plate. Three tracking markers identifying proximal, distal, and lateral heels will be secured to the rear foot of each shoe. Additional tracking markers will be placed on the right anterior thigh and shank, and second metatarsal head for identification of right side vs left side. EMG data for major muscles of the lower- extremity will be collected at 1000 Hz. For each condition, biomechanical data will be collected for 20 seconds after subjects reach a natural steady state, which will ensure a minimum of 15 strides for analysis. CT data collection The CT scans will be acquired for each participant using a scan length that captures the entire tibia and lumbar vertebrae L4 and L5. The CT scans will be performed using a Siemens CT scanner. Images will be reconstructed with a slice thickness of 0.6~0.9 mm and an in-plane pixel resolution of 0.35~0.5 mm. All scans will include a phantom in the field of view with known calcium hydroxyapatite concentrations to convert CT Hounsfield units to bone apparent density. All work will be overseen by Dr. Noehren. Dr. Noehren will meet once every two weeks via teleconference and/or email correspondence with the site PI, Dr. Tong, to provide updates on progress and discuss any unanticipated limitations and potential solutions. In collaboration with Dr. Tong, benchmarks to measure collaborator progress will be established. Final data sets to be used for examining the effects of exoskeleton on the biomechanical responses of the tibia and lumbar spines during walking with a load carriage, will be delivered by Dr. Noehren electronically to Dr. Tong via secure ftp, encrypted physical files, or encrypted email files as appropriate. 5
Effective start/end date11/1/2111/15/22


  • Henry M Jackson Foundation for the Advancement of Military Medicine Incorporated: $183,717.00


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