Biology subjects

Peloquin, J. M.

Publications and source records attributed to Peloquin, J. M..

4 recordsLinked to original sources

bioRxiv2023

Volume loss and recovery in bovine knee meniscus loaded in circumferential tension

Load-induced volume change is an important aspect of knee meniscus function because volume loss creates fluid pressure, which minimizes friction and helps support compressive loads. The knee meniscus is unusual amongst cartilaginous tissues in that it is loaded not only in axial compression, but also in circumferential tension between its tibial attachments. Despite the physiologic importance of the knee meniscus tensile properties, its volumetric strain in tension has never been directly measured, and predictions of volume strain in the scientific literature are inconsistent. In this study, we apply uniaxial tension to bovine knee meniscus and use biplanar imaging to directly observe the resulting 3D volume change and unloaded recovery, revealing that tension causes volumetric contraction. Compression is already known to also cause contraction; therefore, all major physiologic loads compress and pressurize the meniscus, inducing fluid outflow. Although passive unloaded recovery is often described as slow relative to loaded loss, here we show that at physiologic strains the volume recovery rate in the meniscus upon unloading is faster than the rate of volume loss. These measurements of volumetric strain are an important step towards a complete theory of knee meniscus fluid flow and load support.

bioengineering↗

bioRxiv2023

Acute repair of meniscus root tear partially restores joint displacements as measured with MRI and loading in a porcine knee

The meniscus serves important load-bearing functions and protects the underlying articular cartilage. Unfortunately, meniscus tears are common and impair the ability of the meniscus to distribute loads, greatly increasing the risk for developing osteoarthritis. Therefore, surgical repair of the meniscus is a frequently performed procedure; however, this repair does not always prevent osteoarthritis. This is hypothesized to be due to altered joint loading post injury and repair, where the functional deficit of the meniscus prevents it from performing its role of distributing forces. However, many studies of meniscus function required opening the joint, which alters kinematics. The objective of this study was to use novel MRI methods to image the intact joint under axial load and measure the acute meniscus and femur displacements in an intact joint, after a meniscus root tear, and after suture repair in the porcine knee, a frequently used in vivo model. We found that anterior root tear led to large meniscus and femur displacements under physiological axial loading, and that suture anchor repair reduced these displacements, but did not fully restore intact joint kinematics. After tear and repair, the anterior region of the meniscus moved posteriorly and medially as it was forced out of the joint space under loading, while the posterior region had small displacements as the posterior attachment acted as a hinge about which the meniscus rotated in the axial plane. This technique can be applied to evaluate the effect of knee injuries and to develop improved repair strategies to restore joint kinematics.

bioengineering↗

bioRxiv2019

3D Microstructure of Tendon Collagen Fibrils using Serial Block-Face SEM and a Mechanical Model for Load Transfer

Tendons hierarchical structure allows for load transfer between its fibrillar elements at multiple length scales. Tendon microstructure is particularly important, because it includes the cells and their surrounding collagen fibrils, where mechanical interactions can have potentially important physiological and pathological contributions. However, the three-dimensional microstructure and the mechanisms of load transfer in that length scale are not known. It has been postulated that interfibrillar matrix shear or direct load transfer via the fusion/branching of small fibrils are responsible for load transfer, but the significance of these mechanisms is still unclear. Alternatively, the helical fibrils that occur at the microstructural scale in tendon may also mediate load transfer, however, these structures are not well studied due to the lack of a three-dimensional visualization of tendon microstructure. In this study, we used serial block-face scanning electron microscopy (SBF-SEM) to investigate the threedimensional microstructure of fibrils in rat tail tendon. We found that tendon fibrils have a complex architecture with many helically wrapped fibrils. We studied the mechanical implications of these helical structures using finite element modeling and found that frictional contact between helical fibrils can induce load transfer even in the absence of matrix bonding or fibril fusion/branching. This study is significant in that it provides a three-dimensional view of the tendon microstructure and suggests friction between helically wrapped fibrils as a mechanism for load transfer, which is an important aspect of tendon biomechanics.

bioengineering↗

bioRxiv2018

Short cracks in knee meniscus tissue cause strain concentrations, but not weakness, in single-cycle uniaxial tension

Tears are central to knee meniscus pathology and, from a mechanical perspective, are crack-like defects (cracks). In many materials, cracks create stress concentrations that cause progressive local rupture and reduce effective strength. It is currently un-known if cracks in meniscus have these consequences; if they do, this would have repercussions for management of meniscus pathology. The objective of this study was to determine if a short crack in meniscus tissue, which mimics a preclinical meniscus tear, (a) causes crack growth and reduces effective strength, (b) creates a near-tip strain concentration, and (c) creates unloaded regions on either side of the crack. Specimens with and without cracks were tested in uniaxial tension and compared in terms of macroscopic stress-strain curves and digital image correlation strain fields. The strain fields were used as an indicator of stress concentrations and unloaded regions. Effective strength was found to be insensitive to the presence of a crack (potential effect < 0.86 s.d.; {beta} = 0.2), but significant strain concentrations, which have the potential to lead to long-term accumulation of tissue or cell damage, were observed near the crack tip.

bioengineering↗