The purpose of this study was to evaluate the use of compressible soft robotic sensors (C-SRS) in determining plantar pressure to infer vertical and shear forces in wearable technology: A ground reaction pressure sock (GRPS). To assess pressure relationships between C-SRS, pressure cells on a BodiTrakTM Vector Plate, and KistlerTM Force Plates, thirteen volunteers performed three repetitions of three different movements: squats, shifting center-of-pressure right to left foot, and shifting toes to heels with C-SRS in both anterior–posterior (A/P) and medial–lateral (M/L) sensor orientations. Pearson correlation coefficient of C-SRS to BodiTrakTM Vector Plate resulted in an average R-value greater than 0.70 in 618/780 (79%) of sensor to cell comparisons. An average R-value greater than 0.90 was seen in C-SRS comparison to KistlerTM Force Plates during shifting right to left. An autoregressive integrated moving average (ARIMA) was conducted to identify and estimate future C-SRS data. No significant differences were seen in sensor orientation. Sensors in the A/P orientation reported a mean R2 value of 0.952 and 0.945 in the M/L sensor orientation, reducing the effectiveness to infer shear forces. Given the high R values, the use of C-SRSs to infer normal pressures appears to make the development of the GRPS feasible.
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A novel implantable mechanism-based tendon transfer surgery for adult acquired flatfoot deformity: Evaluating feasibility in biomechanical simulation
Adult acquired flatfoot deformity becomes permanent with stage III posterior tibialis tendon dysfunction and results in foot pain and difficulty walking and balancing. To prevent progression to stage III posterior tibialis tendon dysfunction when conservative treatment fails, a flexor digitorum longus to posterior tibialis tendon transfer is often conducted. However, since the flexor digitorum longus only has one-third the force-capability of the posterior tibialis, an osteotomy is typically also required. We propose the use of a novel implantable mechanism to replace the direct attachment of the tendon transfer with a sliding pulley to amplify the force transferred from the donor flexor digitorum longus to the foot arch. In this work, we created four OpenSim models of an arched foot, a flatfoot, a flatfoot with traditional tendon transfer, and a flatfoot with implant-modified tendon transfer. Paired with these models, we developed a forward dynamic simulation of the stance phase of gait that reproduces the medial/lateral distribution of vertical ground reaction forces. The simulation couples the use of a fixed tibia, moving ground plane methodology with simultaneous activation of nine extrinsic lower limb muscles. The arched foot and flatfoot models produced vertical ground reaction forces with the characteristic double-peak profile of gait, and the medial/lateral distribution of these forces compared well with the literature. The flatfoot model with implant-modified tendon transfer produced a 94.2% restoration of the medial/lateral distribution of vertical ground reaction forces generated by our arched foot model, which also represents a 2.1X improvement upon our tendon transfer model. This result demonstrates the feasibility of a pulley-like implant to improve functional outcomes for surgical treatment of adult acquired flatfoot deformity with ideal biomechanics in simulation. The real-world efficacy and feasibility of such a device will require further exploration of factors such as surgical variability, soft tissue interactions and healing response.
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- NSF-PAR ID:
- 10358279
- Editor(s):
- Virdi, Amarjit Singh
- Date Published:
- Journal Name:
- PLOS ONE
- Volume:
- 17
- Issue:
- 9
- ISSN:
- 1932-6203
- Page Range / eLocation ID:
- e0270638
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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ABSTRACT In tendon, type‐I collagen assembles together into fibrils, fibers, and fascicles that exhibit a wavy or crimped pattern that uncrimps with applied tensile loading. This structural property has been observed across multiple tendons throughout aging and may play an important role in tendon viscoelasticity, response to fatigue loading, healing, and development. Previous work has shown that crimp is permanently altered with the application of fatigue loading. This opens the possibility of evaluating tendon crimp as a clinical surrogate of tissue damage. The purpose of this study was to determine how fatigue loading in tendon affects crimp and mechanical properties throughout aging and between tendon types. Mouse patellar tendons (PT) and flexor digitorum longus (FDL) tendons were fatigue loaded while an integrated plane polariscope simultaneously assessed crimp properties at P150 and P570 days of age to model mature and aged tendon phenotypes (
N = 10–11/group). Tendon type, fatigue loading, and aging were found to differentially affect tendon mechanical and crimp properties. FDL tendons had higher modulus and hysteresis, whereas the PT showed more laxity and toe region strain throughout aging. Crimp frequency was consistently higher in FDL compared with PT throughout fatigue loading, whereas the crimp amplitude was cycle dependent. This differential response based on tendon type and age further suggests that the FDL and the PT respond differently to fatigue loading and that this response is age‐dependent. Together, our findings suggest that the mechanical and structural effects of fatigue loading are specific to tendon type and age in mice. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:36–42, 2020 -
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Abstract The absence of preserved soft tissues in the fossil record is frequently a hindrance for palaeontologists wishing to investigate morphological shifts in key skeletal systems, such as the limbs. Understanding the soft tissue composition of modern species can aid in understanding changes in musculoskeletal features through evolution, including those pertaining to locomotion. Establishing anatomical differences in soft tissues utilising an extant phylogenetic bracket can, in turn, assist in interpreting morphological changes in hard tissues and modelling musculoskeletal movements during evolutionary transitions (e.g. digit reduction in perissodactyls). Perissodactyls (horses, rhinoceroses, tapirs and their relatives) are known to have originated with a four‐toed (tetradactyl) forelimb condition. Equids proceeded to reduce all but their central digit, resulting in monodactyly, whereas tapirs retained the ancestral tetradactyl state. The modern Malayan tapir (
Tapirus indicus ) has been shown to exhibit fully functional tetradactyly in its forelimb, more so than any other tapir, and represents an ideal case‐study for muscular arrangement and architectural comparison with the highly derived monodactylEquus . Here, we present the first quantification of muscular architecture of a tetradactyl perissodactyl (T. indicus ), and compare it to measurements from modern monodactyl caballine horse (Equus ferus caballus ). Each muscle of the tapir forelimb was dissected out from a cadaver and measured for architectural properties: muscle‐tendon unit (MTU) length, MTU mass, muscle mass, pennation angle, and resting fibre length. Comparative parameters [physiological cross‐sectional area (PCSA), muscle volume, and % muscle mass] were then calculated from the raw measurements. In the shoulder region, theinfraspinatus ofT. indicus exhibits dual origination sites on either side of the deflected scapular spine. Within ungulates, this condition has only been previously reported in suids. Differences in relative contribution to limb muscle mass betweenT. indicus andEquus highlight forelimb muscles that affect mobility in the lateral and medial digits (e.g.extensor digitorum lateralis ). These muscles were likely reduced in equids during their evolutionary transition from tetradactyl forest‐dwellers to monodactyl, open‐habitat specialists. Patterns of PCSA across the forelimb were similar betweenT. indicus andEquus , with the notable exceptions of thebiceps brachii andflexor carpi ulnaris , which were much larger inEquus . The differences observed in PCSA between the tapir and horse forelimb muscles highlight muscles that are essential for maintaining stability in the monodactyl limb while moving at high speeds. This quantitative dataset of muscle architecture in a functionally tetradactyl perissodactyl is a pivotal first step towards reconstructing the locomotor capabilities of extinct, four‐toed ancestors of modern perissodactyls, and providing further insights into the equid locomotor transition. -
null (Ed.)An active ankle-foot orthosis (AAFO) was developed with the intent of providing propulsive ground reaction force to individuals at risk of experiencing fall. The device makes use of one double-acting cylinder per leg, and a lever arm system to transfer propulsive force to the ground, and potentially assist in fall prevention and rehabilitation. Preliminary tests have been shown to improve ground reaction forces in walking. In this paper, the design and construction of the device is included as well as the control algorithm used and testing procedure. This research may be used to advance the field of gait assistance and fall prevention through use of active foot orthotics.more » « less
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Abstract No current clinical treatments provide an ideal long‐term solution for repair of long bone segment defects. Incomplete healing prevents patients from returning to preinjury activity and ultimately requires additional surgery to induce healing. Obtaining autologous graft material is costly, incurs morbidity, requires surgical time, and quality material is finite. In this pilot study, 3D printed biomimetic scaffolds were used to facilitate rapid bone bridging in critical sized defects in a sheep model. An inverse trabecular pattern based on micro‐CT scans of sheep trabecular bone was printed in polybutylene terephthalate. Scaffolds were coated with micron‐sized tricalcium phosphate particles to induce osteoconductivity. Mesenchymal stem cells (MSCs) were isolated from sheep inguinal and tail fat, in one group of sheep and scaffolds were infiltrated with MSCs in a bioreactor. Controls did not undergo surgery for cell extraction. Scaffolds were implanted into two experimental and two control adult sheep, and followed for either 3 or 6 months. Monthly radiographs and post explant micro‐CT scanning demonstrated bone formation on the lateral, anterior, medial, and posterior‐medial aspects along the entire length of the defect. Bone formation was absent on the posterior‐lateral aspect where a muscle is generally attached to the bone. The 3‐month time point showed 15.5% more cortical bone deposition around the scaffold circumference while the 6‐month time point showed 40.9% more bone deposition within scaffold pores. Control sheep failed to unite. Serum collagen type‐1C‐terminus telopeptides (CTX‐1) showed time‐dependent levels of bone resorption, and calcein labeling demonstrated an increase in bone formation rate in treated animals compared with controls. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 242–252, 2019.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1371/journal.pone.0270638
