Biology subjects

Crouch, D. L.

Publications and source records attributed to Crouch, D. L..

7 recordsLinked to original sources

bioRxiv2024

Identifying an optimal anti-gravity assistance level for select functional shoulder movements: A simulation study

The level of assistance torque is one key design parameter for passive shoulder exoskeletons. High assistance levels may perturb arm movements, while low assistance may not provide functional benefits. This study aimed to use computational tools to identify an optimal anti-gravity assistance level for passive shoulder exoskeletons. We used the task space framework to perform biomechanical simulations of arm movements in OpenSim (Stanford, CA, USA). The simulated movements included shoulder elevation and lowering movements in frontal and scapular planes, as well as forward and lateral reaching movements. These movements were simulated across a range of assistance torque levels from 0% (no-assistance) to 100% of the maximum shoulder gravity torque, in increments of 10%. The optimal assistance level was identified based on analysis of hand kinematics, muscular response efficiency, and glenohumeral joint stability. As the assistance level increased from 10% to 40%, the variability of hand movements nearly doubled, and this trend continued for higher assistance levels. The total muscle effort rate was minimized at an assistance level ranging from 20% to 30%. While the stability of the glenohumeral joint was mostly maintained across assistance levels, it decreased slightly at higher assistance levels. The results of this study indicated that, for the simulated movements, an optimal assistance level lies within the range of 20-30% of the maximum gravity torque at the shoulder joint. Assistance levels above 40% could cause undesired effects such as greater variability of end-limb kinematics, reduced muscular efficiency, and compromised glenohumeral joint stability.

bioengineering↗

bioRxiv2024

Attaching artificial Achilles and tibialis cranialis tendons to bone using suture anchors in a rabbit model: assessment of outcomes

ObjectiveThe purpose of this study was to investigate the factors associated with outcomes of attaching artificial tendons to bone using suture anchors for replacement of biological tendons in rabbits. Study DesignMetal suture anchors with braided composite sutures of varying sizes (USP #1, #2, or #5) were used to secure artificial tendons replacing both the Achilles and tibialis cranialis tendons in 12 New Zealand White rabbits. Artificial tendons were implanted either at the time of (immediate replacement, n=8), or four weeks after (delayed replacement, n=4) resection of the biological tendon. Hindlimb radiographs of the rabbits were obtained immediately after surgery and approximately every other week until the study endpoint (16 weeks post-surgery). ResultsAll suture anchors used for the tibialis cranialis artificial tendons remained secure and did not fail during the study. The suture linkage between the Achilles artificial tendon and anchor failed in 9 of 12 rabbits. In all cases, the mode of failure was suture breakage distant from the knot. Based on radiographic analysis, the mean estimated failure timepoint was 5.3{+/-}2.3 weeks post-surgery, with a range of 2-10 weeks. Analysis of variance (ANOVA) tests revealed no significant effect of tendon implantation timing or suture size on either the timing or frequency of suture anchor failure. ConclusionBased on the mode of failure, suture mechanical properties, and suture anchor design, we suspect that the cause of failure was wear of the suture against the edges of the eyelet in the suture anchor post, which reduced the suture strength below in vivo loads. Suture anchor designs differed for the tibialis cranialis and did not fail during the period of study. Future studies are needed to optimize suture anchor mechanical performance under different loading conditions and suture anchor design features.

bioengineering↗

bioRxiv2023

Replacement of tibialis cranialis tendon with polyester, silicone-coated artificial tendon preserves biomechanical function in rabbits

Artificial tendons may be an effective alternative to autologous and allogenic tendon grafts for repairing critically sized tendon defects. The goal of this study was to quantify the in vivo hindlimb biomechanics (ground contact pressure and sagittal-plane motion) during hopping gait of rabbits having a critically sized tendon defect of the tibialis cranialis and either with or without repair using an artificial tendon. In five rabbits, the tibialis cranialis tendon of the left hindlimb was surgically replaced with a polyester, silicone-coated artificial tendon (PET-SI); five operated control rabbits underwent complete surgical excision of the biological tibialis cranialis tendon in the left hindlimb with no replacement (TE). At 8 weeks post-surgery, peak vertical ground contact force in the left hindlimb was statistically significantly less compared to baseline for the TE group (p=0.0215). Statistical parametric mapping (SPM) analysis showed that, compared to baseline, the knee was significantly more extended during stance at 2 weeks post-surgery and during the swing phase of stride at 2 and 8 weeks post-surgery for the TE group (p<0.05). Also, the ankle was significantly more plantarflexed during swing at 2 and 8 weeks postoperative for the TE group (p<0.05). In contrast, there were no significant differences in the SPM analysis among timepoints in the PET-SI group for the knee or ankle. These findings suggest that the artificial tibialis cranialis tendon effectively replaced the biomechanical function of the native tendon.

bioengineering↗

bioRxiv2022

Rabbit hindlimb kinematics and ground contact pressure during the stance phase of hopping gait

Though the rabbit is a common animal model in musculoskeletal research, there is very limited data reported on healthy rabbit biomechanics. Our objective was to quantify the normative hindlimb biomechanics of six New Zealand White rabbits (3 male, 3 female) during the stance phase of hopping gait. We measured biomechanics by synchronously recording sagittal plane motion and ground contact pressure using a video camera and pressure mat, respectively. Both foot angle (i.e., angle between foot and ground) and ankle angle curves were unimodal. The peak ankle dorsiflexion angle was 65.9{degrees}{+/-}12.7{degrees} and occurred at 39% stance, while the peak ankle plantarflexion angle was 136.9{degrees}{+/-}7.8{degrees} at toe-off. Minimum and maximum foot angles were 16.6{degrees}{+/-}6.4{degrees} at 12% stance and 125.4{degrees}{+/-}4.0{degrees} at toe-off, respectively. During stance, the knee joint center gradually progressed 4.7 cm downward and 18.1 cm forward, on average. The maximum vertical ground reaction force and contact area, both averaged across rabbits, were 42.5 {+/-} 11.4 %BW and 7.5 {+/-} 1.8 cm2, respectively. Our study confirmed that rabbits exhibit a plantigrade gait pattern, similar to humans. Future studies can reference our data to quantify the extent to which orthopedic interventions affect rabbit biomechanics.

systems biology↗

bioRxiv2022

GAIT BIOMECHANICS OF RABBITS WITH EITHER ACHILLES OR TIBIALIS CRANIALIS ARTIFICIAL TENDONS

Artificial tendons have been developed as a replacement for biological tendons with irreparable pathologies and defects. Previous studies reported the mechanical strength and tissue integration of a polyester suture-based artificial tendon, but not its effect on locomotor function. The objective of this study was to quantify the hindlimb biomechanics during hopping gait of New Zealand White rabbits with surgical replacement of either the Achilles (n=2) or tibialis cranialis (TC, n=2) biological tendons with artificial tendons. Once pre-surgery and for five consecutive weeks post-surgery (starting at about two weeks post-surgery), we measured hindlimb kinematics and ground contact pressures with a video camera and pressure mat, respectively. Promisingly, post-surgical locomotor function was either consistent or improved over time in both tendon replacement groups. However, Achilles rabbits exhibited greater immediate post-surgery functional decline and less post-surgical functional recovery than TC rabbits. Compared to healthy rabbits, at the study endpoint, (1) TC rabbits had a 17.3-degree higher (i.e., more plantarflexed) ankle angle at foot strike; and (2) Achilles rabbits had a 39.2-degree lower (i.e., more dorsiflexed) ankle angle at toe off. These functional deficits suggest that the muscles attached to the artificial tendons had lower force-generating capacity. Future studies of artificial tendons are needed to quantify long-term function, determine the effectiveness of structured rehabilitation exercises, and refine surgical implementation.

bioengineering↗

bioRxiv2020

Design and Performance Evaluation of a Wearable Passive Cable-driven Shoulder Exoskeleton

The mechanical assistance provided by exoskeletons could potentially replace, assist, or rehabilitate upper extremity function in patients with mild to moderate shoulder disability to perform activities of daily living. While many exoskeletons are "active" (e.g. motorized), mechanically passive exoskeletons may be a more practical and affordable solution to meet a growing clinical need for continuous, home-based movement assistance. In the current study, we designed, fabricated, and evaluated the performance of a wearable, passive, cable-driven shoulder exoskeleton (WPCSE) prototype. An innovative feature of the WPCSE is a modular spring-cam-wheel system that can be custom designed to compensate for any proportion of the shoulder elevation moment due to gravity over a large range of shoulder motion. The force produced by the spring-cam-wheel system is transmitted over the superior aspect of the shoulder to an arm cuff through a Bowden cable. The results from mechanical evaluation revealed that the modular spring-cam-wheel system could successfully produce an assistive positive shoulder elevation moment that matched the desired, theoretical moment. However, when measured from the physical WPCSE prototype, the moment was lower (up to 30%) during positive shoulder elevation and higher (up to 120%) during negative shoulder elevation due primarily to friction. Even so, our biomechanical evaluation showed that the WPCSE prototype reduced the root mean square (up to 35%) and peak (up to 33%) muscular activity, as measured by electromyography, of several muscles crossing the shoulder during shoulder elevation and horizontal adduction/abduction movements. These preliminary results suggest that our WPCSE may be suitable for providing movement assistance to people with shoulder disability.

bioengineering↗

bioRxiv2020

Characterizing Trabecular Bone Properties near the Glenohumeral Joint Following Brachial Plexus Birth Injury

Brachial plexus birth injury (BPBI) causes functional arm impairment in 30-40% of those affected due to altered loading on the glenohumeral joint. While gross morphological osseous deformities have been seen in the humerus and scapula, alterations in the underlying trabecular bone microstructure and mineralization are not clear. Using a murine model of BPBI, trabecular bone alterations were explored in the proximal humerus and distal scapula, which surround the articulating surface of the joint. Samples were scanned using micro-CT, reoriented, and analyzed for standard trabecular metrics. The regions of interest closest to the articulating surface showed the greatest detriments. In the scapula, the scapular neck region showed less robust trabecular bone in the neurectomy group with decreased BV/TV (p=0.001), BMD (p=0.001), Conn.D (p=0.006), Tb.N (p<0.0001), and DA (p=0.033), and increased Tb.Sp (p<0.0001) compared to sham. In the humerus, the epiphysis showed less robust trabecular bone in neurectomy group, but to a much lesser extent than the scapular neck. The neurectomy group showed reduced BMD (p=0.007) and Tb.N (p=0.029) compared to sham. Data suggest deformities are worse near the articulating surface, likely due to the greater amount of mechanical loading. The reduction in trabecular microstructure and mineralization may compromise bone strength of the affected limb following BPBI. Further investigation of the underlying trabecular bone deformities following injury are necessary to eventually inform better treatments to limit the development of deformities.

bioengineering↗