Browsing by Author "Swamy, Ganesh"

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    Do Mechanical and Structural Characteristics of Degenerated Intervertebral Discs Contribute to Development of Degenerative Scoliosis and Spondylolisthesis?
    (2023-08-28) Bader, Taylor J.; Swamy, Ganesh; Hart, David A.; Duncan, Neil; Salo, Paul
    Intervertebral disc (IVD) degeneration is the age-related breakdown of the cushioned discs that serve as the principal connection between the vertebral bodies. Although affecting 80% of individuals over the age of 50, the causes of the highly varied severity of this disease are not well understood. Additionally, in some cases, primarily in women, the degeneration of the IVD leads to spinal deformities. Degenerative scoliosis (dScoli), the lateral translation and rotation of the vertebrae, and degenerative spondylolisthesis (dSpondy), the forward slippage of the vertebrae with respect to its caudal neighbour, both potentially lead to immobility and pain. These conditions involve increased instability of motion segments of the spine, cascading into further degeneration. The aim of this study was to compare the shear mechanical behaviour of the annulus fibrosus (AF), the outer portion of the IVD, in normal, non-deformity degenerated (degen), dScoli, and dSpondy patients. Small sections of the AF were collected from healthy donors and surgical patients and sheared, mimicking the translation seen in spinal deformity. These same AF sections were scored for degeneration through histology and their lamellar structure was measured with optical coherence tomography (OCT). From these tests, the structure-function relationship of degenerated AF was analyzed to explore degenerative changes. A reduced shear stiffness in degen samples (radial 27 ± 24 kPa, circumferential 57 ± 43 kPa) when compared to normal tissue (radial 80 ± 38 kPa, circumferential 231 ± 73 kPa) was found (p < 0.05). dScoli tissue were further reduced in shear stiffness (radial 12 ± 6 kPa, circumferential 33 ± 21 kPa), although not significantly. There were significant trends linking an increase in structure degeneration, by histology (rS = -0.58, p < 0.01) and OCT (rS = -0.70, p < 0.01), to decreased circumferential shear modulus. Differences in structure and shear stiffness will serve as the backbone for further research into surgical tissue to better understand the progression of IVD degeneration and spinal deformities. Through understanding of the structure-function relationship of the AF, predictors of outcomes and potential treatments could help patients better manage these painful conditions.
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    In vivo kinematic outcomes of cervical total disc arthroplasty using dual fluoroscopy: A longitudinal collective case study
    (2024-12-19) Bangsboll, Emily Merle; Ronsky, Janet Lenore; Swamy, Ganesh; Roach, Koren Elaine; Duncan, Neil Alexander
    Intervertebral disc degeneration of the cervical spine is prevalent in aging adults with symptomatic cases often requiring surgical intervention. Cervical total disc arthroplasty (cTDA) is a surgical treatment for disc degeneration that aims to preserve natural motion of the spine and avoid adjacent segment degeneration. Despite low re-operation rates associated with cTDA, patient outcomes vary, and kinematic effects remain poorly understood. Understanding these effects via in vivo characterization could help address complications of cTDA and improve patient outcomes. This study implemented dual fluoroscopy to evaluate pre- and post-cTDA intervertebral rotations, translations, and endplate proximities to assess the impact of cTDA on in vivo cervical spine kinematics. Five asymptomatic control participants and two surgical participants undergoing cTDA were recruited. Participants underwent computed tomography and dual fluoroscopy imaging during dynamic movements. Model-based tracking matched subject-specific vertebral bone models to each dual fluoroscopy sequence with high accuracy (0.97 mm and 1.4°) and intervertebral rotations, translations, and bone-to-bone proximities were computed. The control pilot study verified the data collection and processing protocols yielded baseline data consistent with literature, although there was notable variability for some trials. Post-cTDA rotation patterns were similar to those of the controls, suggesting increased mobility at both treated and adjacent motion segments. Translations also increased post-cTDA, with some magnitudes exceeding one standard deviation above the control means, potentially indicating instability. Proximity measures indirectly described local disc height and illustrated the coupled motion patterns throughout movement, further emphasizing the value of three-dimensional in vivo kinematic approaches for studying the cervical spine. These kinematic measures have the potential to elucidate the complex coupled motion of the cervical spine post-cTDA and will be valuable for informing future artificial disc designs.
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    Intervertebral Disc Inflammation: The Effect Of Il-1ra Deficiency On Development, Aging And Injury Of The Murine Caudal Intervertebral Disc
    (2018-01) Swamy, Ganesh; Matyas, John; Salo, Paul; Jirik, Frank; Duncan, Neil
    Intervertebral disc inflammation: The effect of IL-1Ra deficiency on development, aging and injury of the murine caudal intervertebral disc Inflammation is a coordinated, balanced and redundant cellular response to threats to homeostasis, and leads to tissue repair and regeneration. In the musculoskeletal system, inflammation is central in such reparative processes as fracture healing and wound repair. Inflammation in the intervertebral disc has been broadly implicated in mainly catabolic or degenerative cellular and matrix processes, and cited as the driver of intervertebral disc (IVD) degeneration. We pursued the hypothesis that increased IL-1 activity accelerates the natural history of IVD degeneration. In this study, we assembled a multi-modal platform to evaluate murine caudal IVD structure (through structured histomorphometry and stereology) and function (through dynamic and elastic biomechanics). We also examined gene expression of whole murine IVD (through QPCR analysis) to evaluate IVD response patterns and localized inflammatory gene expression (through immunohistochemistry). Through detailed study of structure, function and molecular response in vivo, the role of inflammation was contrasted between natural aging in genetically normal mice, mice deficient in IL-1Ra, and in both genotypes in the well-characterized pinprick model. In the first set of investigations, we characterized normal aging of the C57BL/6J caudal IVD, from age 3 to 36 months. In the second set of investigations, we characterized the natural history of IVD changes in the IL-1Ra (-/-) mouse on a C57BL/6J background. In our last set of investigations, we examined the effect of injury via the caudal pinprick injury. When synthesized, there is a predictable structure and functional change in aging caudal IVDs, which is accelerated in IL-1Ra (-/-) mice. Inflammatory gene expression is co-regulated with antagonist genes in the IVD. Despite marked changes in gene expression profiles in injury, wild-type and IL-1Ra (-/-) mice demonstrate similar structural and functional changes. The studies described herein have served to increase the importance of IL-1 related inflammation as a driver of degenerative changes in the IVD, and set the stage for further mechanistic analyses.
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    Multiscale Mechanical Changes to the Collagenous Structure in the Annulus Fibrosus from Adult Degenerative Disc Disease and Adult Spine Deformity Surgical Patients
    (2023-06) Dhiman, Manmeet; Duncan, Neil; Swamy, Ganesh; Hart, David
    The annulus fibrosus in patients with degenerative disc disease (degen) and adult spinal deformities, including degenerative spondylolisthesis (dSpondy), isthmic spondylolisthesis (iSpondy), degenerative scoliosis (dScoli), and adolescent idiopathic scoliosis (AIS), often exhibit severely degenerated discs at the time of surgery. These conditions are accompanied by mechanical and structural changes in the annulus fibrosus, which can cause significant pain and affect mobility. In many cases, the patients require surgical intervention. The overarching hypothesis was that surgical patients have mechanical and structural integrity of the annulus fibrosus compared to normal patients. The objective of the study was to quantify the interlamellar mechanics, circumferential tensile mechanics, and collagen damage in samples from these patients. Interlamellar mechanical properties (Peel Stiffness, Peel Strength, and Peel Toughness) were decreased in the surgical patients compared to the normal patients suggesting a loss of integrity of the collagenous interlamellar matrix in surgical patients. Moderate to strong positive correlations between interlamellar properties and Pfirrmann Grade were observed. Circumferential tensile properties (Rate of Change of Tangential Modulus, Linear Elastic Modulus, Yield Stress, and Ultimate Tensile Stress) were decreased in the surgical patients compared to the normal patients suggesting a loss of collagen's mechanical integrity in the circumferential direction. The collagen hybridizing peptide indicated greater average mean fluorescence intensity and average percent positive ROI area in the surgical patients compared to the normal patients suggesting a loss of structural integrity of collagen. In conclusion, the present study demonstrated that compared to normal patients, surgical patients experienced a greater loss of collagen's structural and mechanical integrity in the annulus fibrosus at molecular and tissue scales.
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    Quantifying In Vivo Cervical Spine Kinematics: Validation of a Novel Data Collection and Processing Pipeline
    (2020-07-16) Figueroa, Luis Alonso; Ronsky, Janet L.; Swamy, Ganesh; Duncan, Neil A.
    Intervertebral disc (IVD) degeneration is a condition that affects a vast majority of the aging population. IVD is characterized by the decay of the joints between vertebrae and may result in pain and disability. Studying spinal kinematics has proven effective for evaluating the outcomes of surgical procedures aimed at mediating with the effects of IVD degeneration, such as cervical discectomy and fusion (ACDF) and cervical total disc arthroplasty (cTDA). However, quantifying and analyzing cervical IVD kinematics represents a challenging task when examining biomechanics of the neck. This study presents a novel data collection and processing pipeline aimed at quantifying in-vivo kinematics of the cervical spine with high-speed biplanar video-radiography (HSBV). A cadaveric pilot study was conducted to test the viability and accuracy of this methodology. Accuracy, defined as the error with respect to radiostereometric analysis (RSA) (the “gold standard”), was calculated as 1.39±0.58° in rotational error and 0.97±0.74 mm in translational error. A separate experiment was implemented to validate the RSA. It was determined that RSA techniques present accuracies of 0.09±0.01 mm and 0.35±0.05 deg/sec. The development of this valuable tool to analyze and measure the in vivo kinematics of the cervical spine will enable further understanding of cervical spine kinematics following cTDA and ACDF.