Intervertebral Disc Height Loss and Restoration: Outcomes and Implications

This thesis is unified around the theme of disc height loss. Current knowledge in the area of spine research identifies mechanical overload as the culprit for the initiation of injury to the spine. While genetic predispositions may play a factor in the severity of spine degeneration or in the resiliency to applied load, ultimately, injury occurs when a load exceeds a tissue’s tolerance. Disc height loss has the potential to be a primary factor in the progression of spinal degeneration. For example, disc height has been touted as a major component for the initiation of pathological and degenerative changes to the spine. Pathologic, non-recoverable disc height loss can occur through herniation or endplate fracture and could result in a degenerative cascade of injury that eventually involves the facet joints, narrows nerve root space, and increases stress at adjacent segments. What is not known is the degree to which disc height affects the degenerative cascade; that is, there is no quantitative data outlining the progression of mechanical consequences at adjacent segments or at the injured segment itself during disc height loss. Further, the degree to which restoring disc height, if even possible, will reverse the process of degeneration is not entirely clear. There is data which suggests that nucleus replacement can restore stress distributions within an injured disc, but the extent of repair material survivability is unknown. Finally, clinical categories of measuring spinal degeneration are based on visual cues and features from medical imaging. Understanding the links between joint visual cues and aberrant movement may help to guide clinical practice; researchers will gain greater insight into the mechanical consequences of anatomical features associated with degeneration. This thesis was comprised of three studies. Study 1 examined the effect of disc height loss and subsequent restoration using an injectable hydrogel on the relative kinematics of a segment with height loss and an adjacent segment. It was found that disc height loss produced an immediate effect, where relative angular displacement was reduced in the segment with height loss and increased in the adjacent segment. Restoring disc height with an injectable hydrogel brought the relative angular displacement of both segments back to their initial values. This study is the first of its kind to examine the immediate effects of disc height loss via loss of nucleus pulposus and restoration. Whether these effects are as clear in-vivo remains to be seen. Study 2 evaluated the efficacy of a novel repair strategy to restore the mechanical profile of a spine segment with disc height loss initiated via compressive fracture. The strategy employed the use of PMMA injected into the vertebral body to attempt to seal a fracture from above the disc, and an injectable hydrogel to restore disc height. The use of PMMA was found to restore the compressive stiffness of the injured segment to within approximately 20% of its initial value, while the use of the injectable hydrogel restored the sagittal plane rotational stiffness to within approximately 50-80% of its initial value. After further repetitive compression had been applied to the spine segment however, the restorative influence of both interventions was lost in terms of rotational and compressive stiffness. It was found that large cracks in the endplate prevented the hydrogel from being contained and quickly returned the segment back to its injured profile. Future efforts at restoring the disc while maintaining its anatomical structures need better methods of creating a sufficient seal inside the disc to allow it to re-pressurize and sustain the stresses encountered on a daily basis. Study 3 employed the use of a novel spine tracking algorithm developed as part of this thesis to evaluate sagittal plane cervical spine motion of a series of patient image sequences who had experienced trauma and had a chief complaint related to their neck, head, or shoulders. Some patients had evidence of disc height loss while others did not. Clinical subgroups were created that classified disc height loss as either moderate/severe (3 cases), mild (8 cases), or non-existent (9 cases). When normalized angular displacement of the C5/C6 segment in a group with moderate to severe height loss was compared to the same level in a group with no height loss, there was a statistically significant difference in angular displacement between the two groups (p = 0.004). Angular displacement at C5/C6 was 20.2% ± 2.3% of total measured neck angular displacement in the moderate/severe height loss group compared to 30.6% ± 4.0% of total measured neck angular displacement in the group without height loss. Based on the limited sample size of this study it would appear that disc height loss creates a loss in range of motion. This work has further revealed the heterogeneous nature of individual segmental movement patterns. However, in the group without height loss, there was a systematic trend seen of an increasing angular displacement with descending segmental level. This was not observed in those with moderate to severe disc height loss. The broad implications of this work are that disc height loss influences spine kinematics, which has implications with respect to further injury propagation through the spinal linkage. Angular displacement of a spine segment appears to be governed by its local stiffness. Restoration of disc height under real injury scenarios is a difficult proposition and any attempts at repair need to sufficiently seal the disc space and prevent extrusion of nucleus pulposus or hydrogel-based implants. We now appreciate the difficulty in this objective. Further, repeating the mechanism of injury will reduce the mechanical effects of the restorative intervention, preventing this is highly important

Digital tracking algorithm reveals the influence of structural irregularities on joint movements in the human cervical spine

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.clinbiomech.2018.04.015 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Background Disc height loss and osteophytes change the local mechanical environment in the spine; while previous research has examined kinematic dysfunction under degenerative change, none has looked at the influence of disc height loss and osteophytes throughout movement. Methods Twenty patients with pain related to the head, neck or shoulders were imaged via videofluoroscopy as they underwent sagittal-plane flexion and extension. A clinician graded disc height loss and osteophytes as “severe/moderate”, “mild”, or “none”. A novel tracking algorithm quantified motions of each vertebra. This information was used to calculate intervertebral angular and shear displacements. The digital algorithm made it practical to track individual vertebrae in multiple patients through hundreds of images without bias. Findings Cases without height loss/osteophytes had a consistent increase in intervertebral angular displacement from C2/C3 to C5/C6, like that of healthy individuals, and mild height losses did not produce aberrations that were systematic or necessarily discernable. However, joints with moderate to severe disc height loss and osteophytes exhibited reduced range of motion compared to adjacent unaffected joints in that patient and corresponding joints in patients without structural irregularities. Interpretation Digitally-obtained motion histories of individual joints allowed anatomical joint changes to be linked with changes in joint movement patterns. Specifically, disc height loss and osteophytes were found to influence cervical spine movement in the sagittal plane, reducing angular motions at affected joints by approximately 10% between those with and without height loss and osteophytes. Further, these joint changes were associated with perturbed intervertebral angular and shear movements.Natural Sciences and Engineering Research Council (NSERC) Discovery Grant

The Tito-Stalin Split 70 Years After

The goal of the Zagreb conference “The Tito-Stalin Split: 70 Years Later”, Zagreb-Goli Otok, 28-30 June 2018, as well as of the papers presented, was to show not only the new interpretations and takes on the subject, but to present the Yugoslav 1948 as a global event, one that touched lives of so many people around the world. It had a very significant impact not only on politics, international relations, prisoners, army cooperation and army relations, ideology, but also cultural life and production, especially in Yugoslavia and the Soviet Union. Most of the papers presented at the Faculty of Humanities and Social Sciences, University of Zagreb, which co-organized the whole event with colleagues from the University of Ljubljana, Slovenia, are published in this volume. A few papers were presented but the authors did not contribute the text (those were: Mark Kramer, Peter Ruggenthaler, Ondřej Vojtěchovský, Klaus Buchenau, Andreii Edemskii, Boris Stamenić, and Marie-Janine Calic). Also, one paper on China was not presented, but the text is here. We hope this volume will be an important contribution to the continuous dialogue that should be not only regional, but global. It should also be ongoing, since there is hardly an event in the history of the Cold War whose consequences were as important and as global as this one’s. (from the Preface)The book is co-published by the University of Zagreb, Faculty of Humanities and Social Sciences – Department of History (Postgraduate Doctoral Studies “Modern and Contemporary Croatian History In European and World Context”) & the University of Ljubljana Faculty of Arts – Department of History, as a volume 31 in the Historia series. The goal of the Zagreb conference “The Tito-Stalin Split: 70 Years Later”, Zagreb-Goli Otok, 28-30 June 2018, as well as of the papers presented, was to show not only the new interpretations and takes on the subject, but to present the Yugoslav 1948 as a global event, one that touched lives of so many people around the world. It had a very significant impact not only on politics, international relations, prisoners, army cooperation and army relations, ideology, but also cultural life and production, especially in Yugoslavia and the Soviet Union.Most of the papers presented at the Faculty of Humanities and Social Sciences, University of Zagreb, which co-organized the whole event with colleagues from the University of Ljubljana, Slovenia, are published in this volume. A few papers were presented but the authors did not contribute the text (those were: Mark Kramer, Peter Ruggenthaler, Ondřej Vojtěchovský, Klaus Buchenau, Andreii Edemskii, Boris Stamenić, and Marie-Janine Calic). Also, one paper on China was not presented, but the text is here. We hope this volume will be an important contribution to the continuous dialogue that should be not only regional, but global. It should also be ongoing, since there is hardly an event in the history of the Cold War whose consequences were as important and as global as this one’s. (from the Preface)The book is co-published by the University of Zagreb, Faculty of Humanities and Social Sciences – Department of History (Postgraduate Doctoral Studies “Modern and Contemporary Croatian History In European and World Context”) & the University of Ljubljana Faculty of Arts – Department of History, as a volume 31 in the Historia series.&nbsp

A videofluoroscopy-based tracking algorithm for quantifying the time course of human intervertebral displacements

<p>The motions of individual intervertebral joints can affect spine motion, injury risk, deterioration, pain, treatment strategies, and clinical outcomes. Since standard kinematic methods do not provide precise time-course details about individual vertebrae and intervertebral motions, information that could be useful for scientific advancement and clinical assessment, we developed an iterative template matching algorithm to obtain this data from videofluoroscopy images. To assess the bias of our approach, vertebrae in an intact porcine spine were tracked and compared to the motions of high-contrast markers. To estimate precision under clinical conditions, motions of three human cervical spines were tracked independently ten times and vertebral and intervertebral motions associated with individual trials were compared to corresponding averages. Both tests produced errors in intervertebral angular and shear displacements no greater than 0.4° and 0.055 mm, respectively. When applied to two patient cases, aberrant intervertebral motions in the cervical spine were typically found to correlate with patient-specific anatomical features such as disc height loss and osteophytes. The case studies suggest that intervertebral kinematic time-course data could have value in clinical assessments, lead to broader understanding of how specific anatomical features influence joint motions, and in due course inform clinical treatments.</p

The Tito-Stalin Split 70 Years After

The goal of the Zagreb conference “The Tito-Stalin Split: 70 Years Later”, Zagreb-Goli Otok, 28-30 June 2018, as well as of the papers presented, was to show not only&nbsp;the new interpretations and takes on the subject, but to present the Yugoslav 1948 as a&nbsp;global event, one that touched lives of so many people around the world. It had a very&nbsp;significant impact not only on politics, international relations, prisoners, army cooperation and army relations, ideology, but also cultural life and production, especially&nbsp;in Yugoslavia and the Soviet Union.&nbsp;Most of the papers presented at the Faculty of Humanities and Social Sciences,&nbsp;University of Zagreb, which co-organized the whole event with colleagues from the&nbsp;University of Ljubljana, Slovenia, are published in this volume. A few papers were presented but the authors did not contribute the text (those were: Mark Kramer, Peter Ruggenthaler, Ondřej Vojtěchovský, Klaus Buchenau, Andreii Edemskii, Boris Stamenić,&nbsp;and Marie-Janine Calic). Also, one paper on China was not presented, but the text is&nbsp;here. We hope this volume will be an important contribution to the continuous dialogue&nbsp;that should be not only regional, but global. It should also be ongoing, since there is&nbsp;hardly an event in the history of the Cold War whose consequences were as important&nbsp;and as global as this one’s. (from the Preface)The book is co-published by the University of Zagreb, Faculty of Humanities and Social Sciences – Department of History (Postgraduate Doctoral Studies “Modern and Contemporary Croatian History In European and World Context”)&nbsp;&amp; the&nbsp;University of Ljubljana Faculty of Arts – Department of History, as a volume 31 in the Historia series.&nbsp;The goal of the Zagreb conference “The Tito-Stalin Split: 70 Years Later”, Zagreb-Goli Otok, 28-30 June 2018, as well as of the papers presented, was to show not only&nbsp;the new interpretations and takes on the subject, but to present the Yugoslav 1948 as a&nbsp;global event, one that touched lives of so many people around the world. It had a very&nbsp;significant impact not only on politics, international relations, prisoners, army cooperation and army relations, ideology, but also cultural life and production, especially&nbsp;in Yugoslavia and the Soviet Union.Most of the papers presented at the Faculty of Humanities and Social Sciences,&nbsp;University of Zagreb, which co-organized the whole event with colleagues from the&nbsp;University of Ljubljana, Slovenia, are published in this volume. A few papers were presented but the authors did not contribute the text (those were: Mark Kramer, Peter Ruggenthaler, Ondřej Vojtěchovský, Klaus Buchenau, Andreii Edemskii, Boris Stamenić,&nbsp;and Marie-Janine Calic). Also, one paper on China was not presented, but the text is&nbsp;here. We hope this volume will be an important contribution to the continuous dialogue&nbsp;that should be not only regional, but global. It should also be ongoing, since there is&nbsp;hardly an event in the history of the Cold War whose consequences were as important&nbsp;and as global as this one’s. (from the Preface)The book is co-published by the University of Zagreb, Faculty of Humanities and Social Sciences – Department of History (Postgraduate Doctoral Studies “Modern and Contemporary Croatian History In European and World Context”)&nbsp;&amp; the&nbsp;University of Ljubljana Faculty of Arts – Department of History, as a volume 31 in the Historia series.&nbsp