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Lorne Beckman

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Papers by Lorne Beckman

Acute mechanical injury of the human intervertebral disc: link to degeneration and pain

Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contrib... more Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contribute to degeneration and pain. However, the exact mechanisms by which mechanical injury initiates and promotes degeneration remain unclear. This study investigates biochemical changes and extracellular matrix disruption in whole-organ human IVD cultures following acute mechanical injury. Isolated healthy human IVDs were rapidly compressed by 5 % (non-injured) or 30 % (injured) of disc height. 30 % strain consistently cracked cartilage endplates, confirming disc trauma. Three days post-loading, conditioned media were assessed for proteoglycan content and released cytokines. Tissue extracts were assessed for proteoglycan content and for aggrecan integrity. Conditioned media were applied to PC12 cells to evaluate if factors inducing neurite growth were released. Compared to controls, IVD injury caused significant cell death. Injury also caused significantly reduced tissue proteoglycan content with a reciprocal increase of proteoglycan content in culture media. Increased aggrecan fragmentation was observed in injured tissue due to increased matrix metalloproteinase and aggrecanase activity. Injured-IVD conditioned media contained significantly elevated interleukin (IL)-5, IL-6, IL-7, IL-8, MCP-2, GROα, and MIG, and ELISA analysis showed significantly increased nerve growth factor levels compared to non-injured media. Injured-disc media caused significant neurite sprouting in PC12 cells compared to non-injured media. Acute mechanical injury of human IVDs ex vivo initiates release of factors and enzyme activity associated with degeneration and back pain. This work provides direct evidence linking acute trauma, inflammatory factors, neo-innervation and potential degeneration and discogenic pain in vivo.

Square-lashing technique in segmental spinal instrumentation: a biomechanical study

European Spine Journal, Feb 10, 2006

Evaluation of quantitative magnetic resonance imaging, biochemical and mechanical properties of trypsin-treated intervertebral discs under physiological compression loading

Journal of Magnetic Resonance Imaging, 2008

Purpose-To investigate the influence of targeted trypsin digestion and 16 hours compression loadi... more Purpose-To investigate the influence of targeted trypsin digestion and 16 hours compression loading on MR parameters and the mechanical and biochemical properties of bovine disc segments. Materials and Methods-Twenty-two 3-disc bovine coccygeal segments underwent compression loading for 16 hours after the nucleus pulposus (NP) of each disc was injected with a solution of trypsin or buffer. The properties of the NP and annulus fibrosus (AF) tissues of each disc were analyzed by quantitative MRI, biochemical tests, and confined compression tests. Results-Loading had a significant effect on the MR properties (T 1 , T 2 , T 1ρ , MTR, ADC) of both the NP and AF tissues. Loading had a greater effect on the MR parameters and biochemical composition of the NP than trypsin. In contrast, trypsin had a larger effect on the mechanical properties. Our data also indicated that localized trypsin injection predominantly affected the NP. T 1ρ was sensitive to loading and correlated with the water content of the NP and AF but not with their proteoglycan content. Conclusion-Our studies indicate that physiological loading is an important parameter to consider and that T 1ρ contributes new information in efforts to develop quantitative MRI as a noninvasive diagnostic tool to detect changes in early disc degeneration. Keywords quantitative MRI; intervertebral disc; T 1ρ ; biomechanics; loading Despite a relentless search for adequate and effective treatment, low back pain is one of the most prevalent (affecting up to 70% of people once during their lifetime) (1) and costly

Biomechanical Comparison of a Unique Plate Versus a Standard Plate for Internal Fixation of Proximal Humerus Fractures in a Cadaveric Model

Orthopaedic Proceedings, Mar 1, 2008

Influence of oscillatory mixing on the injectability of three acrylic and two calcium-phosphate bone cements for vertebroplasty

Journal of Biomedical Materials Research, 2003

Injecting acrylic and, increasingly, calcium‐phosphate cements into the porous bone structure is ... more Injecting acrylic and, increasingly, calcium‐phosphate cements into the porous bone structure is an emerging procedure, referred to as vertebroplasty, for the augmentation of osteoporotic vertebrae. Despite the benefits of vertebroplasty, it has limitations. The limitations of interest in this study are the injectability of bone cements and their mixing variability (i.e., low reproducibility of resulting viscosity). The objective of this study is to investigate the effect of oscillatory versus manual mixing on cement viscosity and mixing variability. Five cements are tested: (a) Vertebroplastic™, (b) DP‐Pour™, (c) Antibiotic Simplex®, (d) chronOS Inject™, and (e) Biopex™. Compared to manual mixing, oscillatory mixing significantly decreased the mean viscosity and the mixing variability, which was inferred from the coefficient of variation. For example, under oscillatory mixing, the viscosity and the variability for Vertebroplastic decreased to one‐third of the corresponding values for manual mixing. Similar results were obtained for the other cements. The decrease in viscosity is attributed to the pseudo‐plastic behavior of bone cements. The decrease in the variability of cement viscosity was attributed to greater dispersive mixing of the cement components under oscillatory mixing. The decrease in viscosity eases the injection by reducing the pressure required. The decrease in the variability of cement viscosity increases reproducibility of the cement injection. Oscillatory mixing appears to have the potential to contribute to improving vertebroplasty. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 105–111, 2004

Rapid Intraoperative Zygoma Fracture Imaging

Plastic and Reconstructive Surgery, Sep 1, 2009

Background: A fractured zygoma frequently results in an aesthetically displeasing facial asymmetr... more Background: A fractured zygoma frequently results in an aesthetically displeasing facial asymmetry. Open reduction and internal fixation may accurately realign the facial skeleton but often with undesirable sequelae. The authors' objective was to develop a precise technique of intraoperative zygoma fracture imaging using a C-arm to permit anatomical fracture realignment while reducing the extent of skeletal exposure required. The simplicity and accessibility of this method should allow its widespread clinical application. Methods: First, using a model skull, the relative positions of the C-arm required to adequately depict zygoma projection, width, arch contour, and zygoma rotation were defined. Second, diverse zygoma fracture types were created in six cadaver heads with a Mini Bionix machine and were repaired using C-arm guidance; accuracy was confirmed with postoperative computed tomography. Third, after defining optimal operating room setup, the accuracy in a clinical case was assessed. Results: Two C-arm views were defined. The zygoma projection view (C-arm at 70 to 90 degrees to the skull's coronal plane) allows visualization of projection, width, and contour. The rotation view (C-arm at 70 to 90 degrees to the skull's sagittal plane) allows visualization of zygoma rotation. Postoperative computed tomographic imaging confirmed anatomical repair in all cases. Average operating room duration was less than 30 minutes, with operating room times decreasing progressively. Conclusions: The authors have developed an accurate technique of intraoperative zygoma fracture imaging and reduction guidance. This technique may decrease the risks of open access by potentially limiting direct skeletal exposure to buttresses where skeletal stabilization is required. In addition, this method is simple, can be learned and used rapidly, and is readily accessible. (Plast.

Double Pedicle Screw Instrumentation in the Osteoporotic Spine

Journal of Spinal Disorders & Techniques, Aug 1, 2007

A biomechanical feasibility test. To assess the overall feasibility, safety, and mechanical effec... more A biomechanical feasibility test. To assess the overall feasibility, safety, and mechanical effectiveness of an intrapedicular double-screw construct in the thoracolumbar spine. The bony purchase of the pedicle screw fixation is often not strong enough in elderly patients with osteoporosis. Our hypothesis was that the elliptical cross-section of the pedicle would allow the insertion of 2 smaller diameter pedicle screws resulting in a bony purchase superior to the standard single-screw technique. Thirty-six double-screw constructs (5mm diameter AOUSS and 5 mm Schanz screw) and 36 standard single pedicle screws (6mm diameter AOUSS screw) were placed. Screw pullout, multiaxial flexibility, and axial failure load testing was performed. Visual inspection, palpation, and radiograph confirmed that there were no pedicle breaches. In the double-screw group, all but 2 constructs had ideal direction. Pullout strength of the double-screw construct was no different than that of the single-screw construct. However, stiffness increased considerably in all testing modes. Axial load to failure, adjusted for bone mineral density, and dimensional variation, also increased. All differences were statistically significant except for axial rotation that was only marginally significant. The double-screw construct appears feasible and safe in the thoracolumbar spine. In this study, the new technique demonstrates a mechanical advantage over the standard single-screw technique. Further in vitro cadaveric safety studies with better adapted instrumentation are needed before the technique can be widely recommended.

Cadaveric device-injected very high-viscosity cement during vertebroplasty

Journal of Craniovertebral Junction and Spine, 2018

Introduction: Cement extravasation during vertebroplasty (VP) is the most commonly reported compl... more Introduction: Cement extravasation during vertebroplasty (VP) is the most commonly reported complication. Cement viscosity is considered the single most important predictor of the risk of extravasation. Certainly, injecting high-viscosity cement (HVC) is difficult to utilize in real practice. We invented a new device capable of injecting high-viscosity with ease and at a distance to avoid radiation. The aim of this study is to confirm the efficacy and safety of the new device on cadaveric vertebrae. Methodology: A 126 osteoporotic vertebral bodies were harvested from cadavers. Eighty vertebrae were included in the study. Computer-randomization software was used to allocate specimens over two main groups, Conventional VP and New Device. Both groups were further subdivided into two subgroups; high-viscosity and low-viscosity. A custom device was used on each vertebra to induce a compression fracture. Results: Injecting HVC was associated with a lower leakage volume compared with low-viscosity cement. HVC was associated with no leakage into the spinal canal. It was also associated with a low incidence of vascular extravasation (P < 0.001). The mean volume of cement leakage in the low-viscosity group was 0.23 and 0.15 cc, for the Conventional VP and New Device, respectively. In both groups, the most common site for leakage was the vertebral end plate, which was exhibited more in the low-viscosity group (71.5%) compared with the high-viscosity group (42.5%). The preset target amount of cement to be injected was reached in 99% of the time when injecting HVC with the New Device, compared with 62% using the Conventional VP. In both groups, there was no correlation between the amount of cement injected and the amount of leakage. Conclusion: The new device is capable of injecting HVC easily, with a lower incidence of cement leakage. It also minimized the risk of radiation exposure to the surgeon.

$Research paper thumbnail of Proximal tibial fracture following anterior cruciate ligament reconstruction surgery: a biomechanical analysis of the tibial tunnel as a stress riser$

Proximal tibial fracture following anterior cruciate ligament reconstruction surgery: a biomechanical analysis of the tibial tunnel as a stress riser

Knee Surgery, Sports Traumatology, Arthroscopy, Oct 14, 2015

This is the first biomechanical study to examine the potential stress riser effect of the tibial ... more This is the first biomechanical study to examine the potential stress riser effect of the tibial tunnel or tunnels after ACL reconstruction surgery. In keeping with literature, the primary hypothesis tested in this study was that the tibial tunnel acts as a stress riser for fracture propagation. Secondary hypotheses were that the stress riser effect increases with the size of the tunnel (8 vs. 10 mm), the orientation of the tunnel [standard (STT) vs. modified transtibial (MTT)], and with the number of tunnels (1 vs. 2). Tibial tunnels simulating both single bundle hamstring graft (8 mm) and bone-patellar tendon-bone graft (10 mm) either STT or MTT position, as well as tunnels simulating double bundle (DB) ACL reconstruction (7, 6 mm), were drilled in fourth-generation saw bones. These five experimental groups and a control group consisting of native saw bones without tunnels were loaded to failure on a Materials Testing System to simulate tibial plateau fracture. There were no statistically significant differences in peak load to failure between any of the groups, including the control group. The fracture occurred through the tibial tunnel in 100 % of the MTT tunnels (8 and 10 mm) and 80 % of the DB tunnels specimens; however, the fractures never (0 %) occurred through the tibial tunnel of the standard tunnels (8 or 10 mm) (P = 0.032). In the biomechanical model, the tibial tunnel does not appear to be a stress riser for fracture propagation, despite suggestions to the contrary in the literature. Use of a standard, more vertical tunnel decreases the risk of ACL graft compromise in the event of a fracture. This may help to inform surgical decision making on ACL reconstruction technique.

Effects of osteogenic protein-1 on distraction osteogenesis in rabbits

Bone, Aug 1, 2003

In this study we tested the effect of locally applied osteogenic protein 1 (OP-1) on distraction ... more In this study we tested the effect of locally applied osteogenic protein 1 (OP-1) on distraction osteogenesis in rabbits. Seven days after tibial osteotomy, distraction was started at a rate of 0.25 mm per 12 h for 3 weeks. At the end of the distraction period, OP-1 was injected at the site of osteotomy. Four different dosages were tested (0, 80, 800, or 2000 g; eight rabbits per dose group). Rabbits were sacrificed 3 weeks later, and histologic, densitometric, and biomechanical parameters were assessed. No significant differences were found between groups for any parameter. To explain why this approach was only modestly successful, the expression of BMP receptor protein in the newly formed tissue was analyzed by immunohistochemistry. Strong expression of BMP receptor IA, IB, and II was found during the early distraction phase, but not during later stages of the process. Thus, it appears that the lack of receptor protein in the target tissue impairs the effect of OP-1 given at the end of the distraction period. Possibly, OP-1 could be more useful when applied early in the distraction phase.

Investigating Commercial Filaments for 3D Printing of Stiff and Elastic Constructs with Ligament-Like Mechanics

Micromachines, Sep 11, 2020

The current gold standard technique for treatment of anterior cruciate ligament (ACL) injury is r... more The current gold standard technique for treatment of anterior cruciate ligament (ACL) injury is reconstruction with autograft. These treatments have a relatively high failure and re-tear rate. To overcome this, tissue engineering and additive manufacturing are being used to explore the potential of 3D scaffolds as autograft substitutes. However, mechanically optimal polymers for this have yet to be identified. Here, we use 3D printing technology and various materials with the aim of fabricating constructs better matching the mechanical properties of the native ACL. A fused deposition modeling (FDM) 3D printer was used to microfabricate dog bone-shaped specimens from six different polymers-PLA, PETG, Lay FOMM 60, NinjaFlex, NinjaFlex-SemiFlex, and FlexiFil-at three different raster angles. The tensile mechanical properties of these polymers were determined from stress-strain curves. Our results indicate that no single material came close enough to successfully match reported mechanical properties of the native ACL. However, PLA and PETG had similar ultimate tensile strengths. Lay FOMM 60 displayed a percentage strain at failure similar to reported values for native ACL. Furthermore, raster angle had a significant impact on some mechanical properties for all of the materials except for FlexiFil. We therefore conclude that while none of these materials alone is optimal for mimicking ACL mechanical properties, there may be potential for creating a 3D-printed composite constructs to match ACL mechanical properties. Further investigations involving co-printing of stiff and elastomeric materials must be explored.

Assessment of Trypsin-Digested and Dynamically Loaded Intervertebral Discs Using Quantitative Mri

Orthopaedic Proceedings, Mar 1, 2008

Purpose: Quantitative MRI is currently being tested as an early and non-invasive diagnostic tool ... more Purpose: Quantitative MRI is currently being tested as an early and non-invasive diagnostic tool of disc problems prior to the appearance of symptoms. The aim of the present study was to determine the effects of cyclic loading and enzymatic digestion on quantitative MRI, biochemical composition, and mechanical properties of intervertebral disc tissue. Methods: Bovine tail segments consisting of three discs were subjected to 16h of cyclic compression loading (50N–300N–50N at 1Hz) or left unloaded for 16h while in saline solution at 37°C. Prior to loading, the nucleus pulposus were injected with either a trypsin or buffer solution. MR examinations were carried out in a 1.5T Siemens` Avanto system to measure T1 and T2 relaxation times, magnetization transfer ratio (MTR), and trace of the apparent diffusion coefficient (TrD). The nucleus pulposus and annulus fibrosus were dissected and analyzed for contents of water, glycosaminoglycan, total collagen, and denatured collagen. Cylindrical nucleus pulposus and annulus fibrosus tissue plugs were harvested, prepared, and tested under confined compression to measure compressive modulus (HA) and hydraulic permeability (k). ANOVA and linear regression analyses were performed (p Results: Loading decreased the T1, T2, and TrD of NP while it increased MTR. Only water content in the nucleus pulposus was significantly influenced by loading. T1, water content, and k of the annulus fibrosus tissue were significantly reduced with loading.|Enzymatic treatment of the nucleus pulposus had no effect on its MR properties, but increased the percent of denatured collagen and thus decreased HA. None of the biochemical, mechanical, and MR parameters of the annulus fibrosus changed with trypsin treatment. Conclusions: Dynamic loading of the disc segments for 16h decreased the permeability of both disc tissues. This was consistent with the measured drop in tissue hydration and was observed as a decrease in T1. Targeted trypsin digestion of the nucleus pulposus was confirmed with no detectable changes in the biochemical, biomechanical, or MR properties of the annulus fibrosus. Future studies will address additional quantitative MR parameters such as T1-rho, a higher strength magnet, and different enzymatic treatments. Funding : Other Education Grant Funding Parties : Canadian Institutes of Health Research, McGill William Dawson Scholar Award, and Whitaker Foundation

The Influence of Harvesting Methods For The Development Of An In-vitro Intervertebral Disc Model

INTRODUCTION: There have been a large variety of animal models used to study the intervertebral d... more INTRODUCTION: There have been a large variety of animal models used to study the intervertebral disc. However, there has yet to be a live ex-vivo model that provides of a platform for long-term, dynamic loading, disc tissue studying and culturing. In this study the impact of harvesting method on the mechanical properties and nutrition diffusion of bovine coccygeal intervertebral discs

Novel Reconstructive Procedure for Unstable Radial-Sided TFCC Avulsions (SS-85)

Arthroscopy: The Journal of Arthroscopic & Related Surgery, 2005

Fatigue Testing of a Titanium Tapered Rod versus Two Rods Connected by a Parallel Connector across the Cervicothoracic Junction: A Biomechanical Study

Journal of King Abdulaziz University-medical Sciences, Jun 30, 2020

This study compares the fatigue failure of a tapered titanium-rod construct against two connected... more This study compares the fatigue failure of a tapered titanium-rod construct against two connected titanium rods (domino construct) across the cervicothoracic junction. All testing was carried out in a simulated flexion-extension plane. The 3.5-mm/6.0-mm tapered titanium rod and the 3.5-mm titanium rod, connected to a 6.0-mm titanium rod with a connector, were compared for their fatigue failures. Six specimens of each construct were tested in a cantilever displacement control method using 6 different amplitudes. Each specimen was cycled to failure or to 2.5 million cycles (run out) at 10 Hz. Failure was defined as rod fracture. The domino construct reached the test limit of 2.5 million cycles at± 0.45 mm (72 N) but failed in all the other tested amplitudes. The tapered rod construct reached the test run out limit of 2.5 million cycles at higher amplitudes than the domino construct at ± 0.9 mm and failed in all the other tested amplitudes. The study showed that the tapered-rod construct across the cervicothoracic junction is more fatigue resistant than the domino construct.

Dynamic loading, matrix maintenance and cell injection therapy of human intervertebral discs cultured in a bioreactor

European Cells and Materials, 2016

Low back pain originating from intervertebral disc (IVD) degeneration affects the quality of life... more Low back pain originating from intervertebral disc (IVD) degeneration affects the quality of life for millions of people, and it is a major contributor to global healthcare costs. Long-term culture of intact IVDs is necessary to develop ex vivo models of human IVD degeneration and repair, where the relationship between mechanobiology, disc matrix composition and metabolism can be better understood. A bioreactor was developed that facilitates culture of intact human IVDs in a controlled, dynamically loaded environment. Tissue integrity and cell viability was evaluated under 3 different loading conditions: low 0.1-0.3, medium 0.1-0.6 and high 0.1-1.2 MPa. Cell viability was maintained > 80 % throughout the disc at low and medium loads, whereas it dropped to approximately 70 % (NP) and 50 % (AF) under high loads. Although cell viability was affected at high loads, there was no evidence of sGAG loss, changes in newly synthesised collagen type II or chondroadherin fragmentation. Sulphated GAG content remained at a stable level of approximately 50 µg sGAG/ mg tissue in all loading protocols. To evaluate the feasibility of tissue repair strategies with cell supplementation, human NP cells were transplanted into discs within a thermoreversible hyaluronan hydrogel. The discs were loaded under medium loads, and the injected cells remained largely localised to the NP region. This study demonstrates the feasibility of culturing human IVDs for 14 days under cyclic dynamic loading conditions. The system allows the determination a safe range-of-loading and presents a platform to evaluate cell therapies and help to elucidate the effect of load following cell-based therapies.

Acute mechanical injury of the human intervertebral disc: link to degeneration and pain

European Cells and Materials, 2014

Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contrib... more Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contribute to degeneration and pain. However, the exact mechanisms by which mechanical injury initiates and promotes degeneration remain unclear. This study investigates biochemical changes and extracellular matrix disruption in whole-organ human IVD cultures following acute mechanical injury. Isolated healthy human IVDs were rapidly compressed by 5 % (non-injured) or 30 % (injured) of disc height. 30 % strain consistently cracked cartilage endplates, confirming disc trauma. Three days post-loading, conditioned media were assessed for proteoglycan content and released cytokines. Tissue extracts were assessed for proteoglycan content and for aggrecan integrity. Conditioned media were applied to PC12 cells to evaluate if factors inducing neurite growth were released. Compared to controls, IVD injury caused significant cell death. Injury also caused significantly reduced tissue proteoglycan content with a reciprocal increase of proteoglycan content in culture media. Increased aggrecan fragmentation was observed in injured tissue due to increased matrix metalloproteinase and aggrecanase activity. Injured-IVD conditioned media contained significantly elevated interleukin (IL)-5, IL-6, IL-7, IL-8, MCP-2, GROα, and MIG, and ELISA analysis showed significantly increased nerve growth factor levels compared to non-injured media. Injured-disc media caused significant neurite sprouting in PC12 cells compared to non-injured media. Acute mechanical injury of human IVDs ex vivo initiates release of factors and enzyme activity associated with degeneration and back pain. This work provides direct evidence linking acute trauma, inflammatory factors, neo-innervation and potential degeneration and discogenic pain in vivo.

Bone Cement Injection Device

$Research paper thumbnail of Biomechanical comparison of a unique locking plate versus a standard plate for internal fixation of proximal humerus fractures in a cadaveric model$

Biomechanical comparison of a unique locking plate versus a standard plate for internal fixation of proximal humerus fractures in a cadaveric model

Clinical Biomechanics, 2006

Newer internal fixation devices with a locking mechanism between the plate and the screw have rec... more Newer internal fixation devices with a locking mechanism between the plate and the screw have recently been released. The efficacy of these plates in the proximal humerus has yet to be fully described. There is a need to compare the biomechanical properties of efficacy of plate fixation with or without locking screws for surgery of two-part proximal humerus fractures. Multiple-plane locking plate and cloverleaf plate designs were tested to determine their ability to maintain fixation on the humeral head. Eight matched pairs of cadaveric shoulders with 7-millimeter osteotomy defects at the surgical neck simulating two-part fractures of the proximal humerus were loaded to failure in thirty degrees of glenohumeral abduction. One side was repaired with a proximal humerus locking plate and the other with a cloverleaf plate. The rotator cuff musculature was then loaded via a servo-hydraulic testing machine under displacement control to simulate the deforming forces present in vivo. The average maximum load to failure was greater in proximal humerus locking plates than in cloverleaf plates (876 versus 712; P=0.04). In the cadaveric, two-part proximal humerus fracture model that was created, the locking plate displayed significantly greater holding power of the humeral head. Clinical relevance is unproven but may be manifested in vivo as improved early range of motion exercises and functional outcome.

Paper 108: Evaluation of Quantitative Magnetic Resonance Imaging, Biochemical and Mechanical Properties of Trypsin Treated …

Journal of Bone & Joint …, 2010

Purpose: Since the human intervertebral disc (IVD) is loaded in compression for approximately 16h... more

Acute mechanical injury of the human intervertebral disc: link to degeneration and pain

Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contrib... more Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contribute to degeneration and pain. However, the exact mechanisms by which mechanical injury initiates and promotes degeneration remain unclear. This study investigates biochemical changes and extracellular matrix disruption in whole-organ human IVD cultures following acute mechanical injury. Isolated healthy human IVDs were rapidly compressed by 5 % (non-injured) or 30 % (injured) of disc height. 30 % strain consistently cracked cartilage endplates, confirming disc trauma. Three days post-loading, conditioned media were assessed for proteoglycan content and released cytokines. Tissue extracts were assessed for proteoglycan content and for aggrecan integrity. Conditioned media were applied to PC12 cells to evaluate if factors inducing neurite growth were released. Compared to controls, IVD injury caused significant cell death. Injury also caused significantly reduced tissue proteoglycan content with a reciprocal increase of proteoglycan content in culture media. Increased aggrecan fragmentation was observed in injured tissue due to increased matrix metalloproteinase and aggrecanase activity. Injured-IVD conditioned media contained significantly elevated interleukin (IL)-5, IL-6, IL-7, IL-8, MCP-2, GROα, and MIG, and ELISA analysis showed significantly increased nerve growth factor levels compared to non-injured media. Injured-disc media caused significant neurite sprouting in PC12 cells compared to non-injured media. Acute mechanical injury of human IVDs ex vivo initiates release of factors and enzyme activity associated with degeneration and back pain. This work provides direct evidence linking acute trauma, inflammatory factors, neo-innervation and potential degeneration and discogenic pain in vivo.

Square-lashing technique in segmental spinal instrumentation: a biomechanical study

European Spine Journal, Feb 10, 2006

Evaluation of quantitative magnetic resonance imaging, biochemical and mechanical properties of trypsin-treated intervertebral discs under physiological compression loading

Journal of Magnetic Resonance Imaging, 2008

Purpose-To investigate the influence of targeted trypsin digestion and 16 hours compression loadi... more Purpose-To investigate the influence of targeted trypsin digestion and 16 hours compression loading on MR parameters and the mechanical and biochemical properties of bovine disc segments. Materials and Methods-Twenty-two 3-disc bovine coccygeal segments underwent compression loading for 16 hours after the nucleus pulposus (NP) of each disc was injected with a solution of trypsin or buffer. The properties of the NP and annulus fibrosus (AF) tissues of each disc were analyzed by quantitative MRI, biochemical tests, and confined compression tests. Results-Loading had a significant effect on the MR properties (T 1 , T 2 , T 1ρ , MTR, ADC) of both the NP and AF tissues. Loading had a greater effect on the MR parameters and biochemical composition of the NP than trypsin. In contrast, trypsin had a larger effect on the mechanical properties. Our data also indicated that localized trypsin injection predominantly affected the NP. T 1ρ was sensitive to loading and correlated with the water content of the NP and AF but not with their proteoglycan content. Conclusion-Our studies indicate that physiological loading is an important parameter to consider and that T 1ρ contributes new information in efforts to develop quantitative MRI as a noninvasive diagnostic tool to detect changes in early disc degeneration. Keywords quantitative MRI; intervertebral disc; T 1ρ ; biomechanics; loading Despite a relentless search for adequate and effective treatment, low back pain is one of the most prevalent (affecting up to 70% of people once during their lifetime) (1) and costly

Biomechanical Comparison of a Unique Plate Versus a Standard Plate for Internal Fixation of Proximal Humerus Fractures in a Cadaveric Model

Orthopaedic Proceedings, Mar 1, 2008

Influence of oscillatory mixing on the injectability of three acrylic and two calcium-phosphate bone cements for vertebroplasty

Journal of Biomedical Materials Research, 2003

Injecting acrylic and, increasingly, calcium‐phosphate cements into the porous bone structure is ... more Injecting acrylic and, increasingly, calcium‐phosphate cements into the porous bone structure is an emerging procedure, referred to as vertebroplasty, for the augmentation of osteoporotic vertebrae. Despite the benefits of vertebroplasty, it has limitations. The limitations of interest in this study are the injectability of bone cements and their mixing variability (i.e., low reproducibility of resulting viscosity). The objective of this study is to investigate the effect of oscillatory versus manual mixing on cement viscosity and mixing variability. Five cements are tested: (a) Vertebroplastic™, (b) DP‐Pour™, (c) Antibiotic Simplex®, (d) chronOS Inject™, and (e) Biopex™. Compared to manual mixing, oscillatory mixing significantly decreased the mean viscosity and the mixing variability, which was inferred from the coefficient of variation. For example, under oscillatory mixing, the viscosity and the variability for Vertebroplastic decreased to one‐third of the corresponding values for manual mixing. Similar results were obtained for the other cements. The decrease in viscosity is attributed to the pseudo‐plastic behavior of bone cements. The decrease in the variability of cement viscosity was attributed to greater dispersive mixing of the cement components under oscillatory mixing. The decrease in viscosity eases the injection by reducing the pressure required. The decrease in the variability of cement viscosity increases reproducibility of the cement injection. Oscillatory mixing appears to have the potential to contribute to improving vertebroplasty. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 105–111, 2004

Rapid Intraoperative Zygoma Fracture Imaging

Plastic and Reconstructive Surgery, Sep 1, 2009

Background: A fractured zygoma frequently results in an aesthetically displeasing facial asymmetr... more Background: A fractured zygoma frequently results in an aesthetically displeasing facial asymmetry. Open reduction and internal fixation may accurately realign the facial skeleton but often with undesirable sequelae. The authors' objective was to develop a precise technique of intraoperative zygoma fracture imaging using a C-arm to permit anatomical fracture realignment while reducing the extent of skeletal exposure required. The simplicity and accessibility of this method should allow its widespread clinical application. Methods: First, using a model skull, the relative positions of the C-arm required to adequately depict zygoma projection, width, arch contour, and zygoma rotation were defined. Second, diverse zygoma fracture types were created in six cadaver heads with a Mini Bionix machine and were repaired using C-arm guidance; accuracy was confirmed with postoperative computed tomography. Third, after defining optimal operating room setup, the accuracy in a clinical case was assessed. Results: Two C-arm views were defined. The zygoma projection view (C-arm at 70 to 90 degrees to the skull's coronal plane) allows visualization of projection, width, and contour. The rotation view (C-arm at 70 to 90 degrees to the skull's sagittal plane) allows visualization of zygoma rotation. Postoperative computed tomographic imaging confirmed anatomical repair in all cases. Average operating room duration was less than 30 minutes, with operating room times decreasing progressively. Conclusions: The authors have developed an accurate technique of intraoperative zygoma fracture imaging and reduction guidance. This technique may decrease the risks of open access by potentially limiting direct skeletal exposure to buttresses where skeletal stabilization is required. In addition, this method is simple, can be learned and used rapidly, and is readily accessible. (Plast.

Double Pedicle Screw Instrumentation in the Osteoporotic Spine

Journal of Spinal Disorders & Techniques, Aug 1, 2007

A biomechanical feasibility test. To assess the overall feasibility, safety, and mechanical effec... more A biomechanical feasibility test. To assess the overall feasibility, safety, and mechanical effectiveness of an intrapedicular double-screw construct in the thoracolumbar spine. The bony purchase of the pedicle screw fixation is often not strong enough in elderly patients with osteoporosis. Our hypothesis was that the elliptical cross-section of the pedicle would allow the insertion of 2 smaller diameter pedicle screws resulting in a bony purchase superior to the standard single-screw technique. Thirty-six double-screw constructs (5mm diameter AOUSS and 5 mm Schanz screw) and 36 standard single pedicle screws (6mm diameter AOUSS screw) were placed. Screw pullout, multiaxial flexibility, and axial failure load testing was performed. Visual inspection, palpation, and radiograph confirmed that there were no pedicle breaches. In the double-screw group, all but 2 constructs had ideal direction. Pullout strength of the double-screw construct was no different than that of the single-screw construct. However, stiffness increased considerably in all testing modes. Axial load to failure, adjusted for bone mineral density, and dimensional variation, also increased. All differences were statistically significant except for axial rotation that was only marginally significant. The double-screw construct appears feasible and safe in the thoracolumbar spine. In this study, the new technique demonstrates a mechanical advantage over the standard single-screw technique. Further in vitro cadaveric safety studies with better adapted instrumentation are needed before the technique can be widely recommended.

Cadaveric device-injected very high-viscosity cement during vertebroplasty

Journal of Craniovertebral Junction and Spine, 2018

Introduction: Cement extravasation during vertebroplasty (VP) is the most commonly reported compl... more Introduction: Cement extravasation during vertebroplasty (VP) is the most commonly reported complication. Cement viscosity is considered the single most important predictor of the risk of extravasation. Certainly, injecting high-viscosity cement (HVC) is difficult to utilize in real practice. We invented a new device capable of injecting high-viscosity with ease and at a distance to avoid radiation. The aim of this study is to confirm the efficacy and safety of the new device on cadaveric vertebrae. Methodology: A 126 osteoporotic vertebral bodies were harvested from cadavers. Eighty vertebrae were included in the study. Computer-randomization software was used to allocate specimens over two main groups, Conventional VP and New Device. Both groups were further subdivided into two subgroups; high-viscosity and low-viscosity. A custom device was used on each vertebra to induce a compression fracture. Results: Injecting HVC was associated with a lower leakage volume compared with low-viscosity cement. HVC was associated with no leakage into the spinal canal. It was also associated with a low incidence of vascular extravasation (P < 0.001). The mean volume of cement leakage in the low-viscosity group was 0.23 and 0.15 cc, for the Conventional VP and New Device, respectively. In both groups, the most common site for leakage was the vertebral end plate, which was exhibited more in the low-viscosity group (71.5%) compared with the high-viscosity group (42.5%). The preset target amount of cement to be injected was reached in 99% of the time when injecting HVC with the New Device, compared with 62% using the Conventional VP. In both groups, there was no correlation between the amount of cement injected and the amount of leakage. Conclusion: The new device is capable of injecting HVC easily, with a lower incidence of cement leakage. It also minimized the risk of radiation exposure to the surgeon.

$Research paper thumbnail of Proximal tibial fracture following anterior cruciate ligament reconstruction surgery: a biomechanical analysis of the tibial tunnel as a stress riser$

Proximal tibial fracture following anterior cruciate ligament reconstruction surgery: a biomechanical analysis of the tibial tunnel as a stress riser

Knee Surgery, Sports Traumatology, Arthroscopy, Oct 14, 2015

This is the first biomechanical study to examine the potential stress riser effect of the tibial ... more This is the first biomechanical study to examine the potential stress riser effect of the tibial tunnel or tunnels after ACL reconstruction surgery. In keeping with literature, the primary hypothesis tested in this study was that the tibial tunnel acts as a stress riser for fracture propagation. Secondary hypotheses were that the stress riser effect increases with the size of the tunnel (8 vs. 10 mm), the orientation of the tunnel [standard (STT) vs. modified transtibial (MTT)], and with the number of tunnels (1 vs. 2). Tibial tunnels simulating both single bundle hamstring graft (8 mm) and bone-patellar tendon-bone graft (10 mm) either STT or MTT position, as well as tunnels simulating double bundle (DB) ACL reconstruction (7, 6 mm), were drilled in fourth-generation saw bones. These five experimental groups and a control group consisting of native saw bones without tunnels were loaded to failure on a Materials Testing System to simulate tibial plateau fracture. There were no statistically significant differences in peak load to failure between any of the groups, including the control group. The fracture occurred through the tibial tunnel in 100 % of the MTT tunnels (8 and 10 mm) and 80 % of the DB tunnels specimens; however, the fractures never (0 %) occurred through the tibial tunnel of the standard tunnels (8 or 10 mm) (P = 0.032). In the biomechanical model, the tibial tunnel does not appear to be a stress riser for fracture propagation, despite suggestions to the contrary in the literature. Use of a standard, more vertical tunnel decreases the risk of ACL graft compromise in the event of a fracture. This may help to inform surgical decision making on ACL reconstruction technique.

Effects of osteogenic protein-1 on distraction osteogenesis in rabbits

Bone, Aug 1, 2003

In this study we tested the effect of locally applied osteogenic protein 1 (OP-1) on distraction ... more In this study we tested the effect of locally applied osteogenic protein 1 (OP-1) on distraction osteogenesis in rabbits. Seven days after tibial osteotomy, distraction was started at a rate of 0.25 mm per 12 h for 3 weeks. At the end of the distraction period, OP-1 was injected at the site of osteotomy. Four different dosages were tested (0, 80, 800, or 2000 g; eight rabbits per dose group). Rabbits were sacrificed 3 weeks later, and histologic, densitometric, and biomechanical parameters were assessed. No significant differences were found between groups for any parameter. To explain why this approach was only modestly successful, the expression of BMP receptor protein in the newly formed tissue was analyzed by immunohistochemistry. Strong expression of BMP receptor IA, IB, and II was found during the early distraction phase, but not during later stages of the process. Thus, it appears that the lack of receptor protein in the target tissue impairs the effect of OP-1 given at the end of the distraction period. Possibly, OP-1 could be more useful when applied early in the distraction phase.

Investigating Commercial Filaments for 3D Printing of Stiff and Elastic Constructs with Ligament-Like Mechanics

Micromachines, Sep 11, 2020

The current gold standard technique for treatment of anterior cruciate ligament (ACL) injury is r... more The current gold standard technique for treatment of anterior cruciate ligament (ACL) injury is reconstruction with autograft. These treatments have a relatively high failure and re-tear rate. To overcome this, tissue engineering and additive manufacturing are being used to explore the potential of 3D scaffolds as autograft substitutes. However, mechanically optimal polymers for this have yet to be identified. Here, we use 3D printing technology and various materials with the aim of fabricating constructs better matching the mechanical properties of the native ACL. A fused deposition modeling (FDM) 3D printer was used to microfabricate dog bone-shaped specimens from six different polymers-PLA, PETG, Lay FOMM 60, NinjaFlex, NinjaFlex-SemiFlex, and FlexiFil-at three different raster angles. The tensile mechanical properties of these polymers were determined from stress-strain curves. Our results indicate that no single material came close enough to successfully match reported mechanical properties of the native ACL. However, PLA and PETG had similar ultimate tensile strengths. Lay FOMM 60 displayed a percentage strain at failure similar to reported values for native ACL. Furthermore, raster angle had a significant impact on some mechanical properties for all of the materials except for FlexiFil. We therefore conclude that while none of these materials alone is optimal for mimicking ACL mechanical properties, there may be potential for creating a 3D-printed composite constructs to match ACL mechanical properties. Further investigations involving co-printing of stiff and elastomeric materials must be explored.

Assessment of Trypsin-Digested and Dynamically Loaded Intervertebral Discs Using Quantitative Mri

Orthopaedic Proceedings, Mar 1, 2008

Purpose: Quantitative MRI is currently being tested as an early and non-invasive diagnostic tool ... more Purpose: Quantitative MRI is currently being tested as an early and non-invasive diagnostic tool of disc problems prior to the appearance of symptoms. The aim of the present study was to determine the effects of cyclic loading and enzymatic digestion on quantitative MRI, biochemical composition, and mechanical properties of intervertebral disc tissue. Methods: Bovine tail segments consisting of three discs were subjected to 16h of cyclic compression loading (50N–300N–50N at 1Hz) or left unloaded for 16h while in saline solution at 37°C. Prior to loading, the nucleus pulposus were injected with either a trypsin or buffer solution. MR examinations were carried out in a 1.5T Siemens` Avanto system to measure T1 and T2 relaxation times, magnetization transfer ratio (MTR), and trace of the apparent diffusion coefficient (TrD). The nucleus pulposus and annulus fibrosus were dissected and analyzed for contents of water, glycosaminoglycan, total collagen, and denatured collagen. Cylindrical nucleus pulposus and annulus fibrosus tissue plugs were harvested, prepared, and tested under confined compression to measure compressive modulus (HA) and hydraulic permeability (k). ANOVA and linear regression analyses were performed (p Results: Loading decreased the T1, T2, and TrD of NP while it increased MTR. Only water content in the nucleus pulposus was significantly influenced by loading. T1, water content, and k of the annulus fibrosus tissue were significantly reduced with loading.|Enzymatic treatment of the nucleus pulposus had no effect on its MR properties, but increased the percent of denatured collagen and thus decreased HA. None of the biochemical, mechanical, and MR parameters of the annulus fibrosus changed with trypsin treatment. Conclusions: Dynamic loading of the disc segments for 16h decreased the permeability of both disc tissues. This was consistent with the measured drop in tissue hydration and was observed as a decrease in T1. Targeted trypsin digestion of the nucleus pulposus was confirmed with no detectable changes in the biochemical, biomechanical, or MR properties of the annulus fibrosus. Future studies will address additional quantitative MR parameters such as T1-rho, a higher strength magnet, and different enzymatic treatments. Funding : Other Education Grant Funding Parties : Canadian Institutes of Health Research, McGill William Dawson Scholar Award, and Whitaker Foundation

The Influence of Harvesting Methods For The Development Of An In-vitro Intervertebral Disc Model

INTRODUCTION: There have been a large variety of animal models used to study the intervertebral d... more INTRODUCTION: There have been a large variety of animal models used to study the intervertebral disc. However, there has yet to be a live ex-vivo model that provides of a platform for long-term, dynamic loading, disc tissue studying and culturing. In this study the impact of harvesting method on the mechanical properties and nutrition diffusion of bovine coccygeal intervertebral discs

Novel Reconstructive Procedure for Unstable Radial-Sided TFCC Avulsions (SS-85)

Arthroscopy: The Journal of Arthroscopic & Related Surgery, 2005

Fatigue Testing of a Titanium Tapered Rod versus Two Rods Connected by a Parallel Connector across the Cervicothoracic Junction: A Biomechanical Study

Journal of King Abdulaziz University-medical Sciences, Jun 30, 2020

This study compares the fatigue failure of a tapered titanium-rod construct against two connected... more This study compares the fatigue failure of a tapered titanium-rod construct against two connected titanium rods (domino construct) across the cervicothoracic junction. All testing was carried out in a simulated flexion-extension plane. The 3.5-mm/6.0-mm tapered titanium rod and the 3.5-mm titanium rod, connected to a 6.0-mm titanium rod with a connector, were compared for their fatigue failures. Six specimens of each construct were tested in a cantilever displacement control method using 6 different amplitudes. Each specimen was cycled to failure or to 2.5 million cycles (run out) at 10 Hz. Failure was defined as rod fracture. The domino construct reached the test limit of 2.5 million cycles at± 0.45 mm (72 N) but failed in all the other tested amplitudes. The tapered rod construct reached the test run out limit of 2.5 million cycles at higher amplitudes than the domino construct at ± 0.9 mm and failed in all the other tested amplitudes. The study showed that the tapered-rod construct across the cervicothoracic junction is more fatigue resistant than the domino construct.

Dynamic loading, matrix maintenance and cell injection therapy of human intervertebral discs cultured in a bioreactor

European Cells and Materials, 2016

Low back pain originating from intervertebral disc (IVD) degeneration affects the quality of life... more Low back pain originating from intervertebral disc (IVD) degeneration affects the quality of life for millions of people, and it is a major contributor to global healthcare costs. Long-term culture of intact IVDs is necessary to develop ex vivo models of human IVD degeneration and repair, where the relationship between mechanobiology, disc matrix composition and metabolism can be better understood. A bioreactor was developed that facilitates culture of intact human IVDs in a controlled, dynamically loaded environment. Tissue integrity and cell viability was evaluated under 3 different loading conditions: low 0.1-0.3, medium 0.1-0.6 and high 0.1-1.2 MPa. Cell viability was maintained > 80 % throughout the disc at low and medium loads, whereas it dropped to approximately 70 % (NP) and 50 % (AF) under high loads. Although cell viability was affected at high loads, there was no evidence of sGAG loss, changes in newly synthesised collagen type II or chondroadherin fragmentation. Sulphated GAG content remained at a stable level of approximately 50 µg sGAG/ mg tissue in all loading protocols. To evaluate the feasibility of tissue repair strategies with cell supplementation, human NP cells were transplanted into discs within a thermoreversible hyaluronan hydrogel. The discs were loaded under medium loads, and the injected cells remained largely localised to the NP region. This study demonstrates the feasibility of culturing human IVDs for 14 days under cyclic dynamic loading conditions. The system allows the determination a safe range-of-loading and presents a platform to evaluate cell therapies and help to elucidate the effect of load following cell-based therapies.

Acute mechanical injury of the human intervertebral disc: link to degeneration and pain

European Cells and Materials, 2014

Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contrib... more Excessive mechanical loading or acute trauma to intervertebral discs (IVDs) is thought to contribute to degeneration and pain. However, the exact mechanisms by which mechanical injury initiates and promotes degeneration remain unclear. This study investigates biochemical changes and extracellular matrix disruption in whole-organ human IVD cultures following acute mechanical injury. Isolated healthy human IVDs were rapidly compressed by 5 % (non-injured) or 30 % (injured) of disc height. 30 % strain consistently cracked cartilage endplates, confirming disc trauma. Three days post-loading, conditioned media were assessed for proteoglycan content and released cytokines. Tissue extracts were assessed for proteoglycan content and for aggrecan integrity. Conditioned media were applied to PC12 cells to evaluate if factors inducing neurite growth were released. Compared to controls, IVD injury caused significant cell death. Injury also caused significantly reduced tissue proteoglycan content with a reciprocal increase of proteoglycan content in culture media. Increased aggrecan fragmentation was observed in injured tissue due to increased matrix metalloproteinase and aggrecanase activity. Injured-IVD conditioned media contained significantly elevated interleukin (IL)-5, IL-6, IL-7, IL-8, MCP-2, GROα, and MIG, and ELISA analysis showed significantly increased nerve growth factor levels compared to non-injured media. Injured-disc media caused significant neurite sprouting in PC12 cells compared to non-injured media. Acute mechanical injury of human IVDs ex vivo initiates release of factors and enzyme activity associated with degeneration and back pain. This work provides direct evidence linking acute trauma, inflammatory factors, neo-innervation and potential degeneration and discogenic pain in vivo.

Bone Cement Injection Device

$Research paper thumbnail of Biomechanical comparison of a unique locking plate versus a standard plate for internal fixation of proximal humerus fractures in a cadaveric model$

Biomechanical comparison of a unique locking plate versus a standard plate for internal fixation of proximal humerus fractures in a cadaveric model

Clinical Biomechanics, 2006

Newer internal fixation devices with a locking mechanism between the plate and the screw have rec... more Newer internal fixation devices with a locking mechanism between the plate and the screw have recently been released. The efficacy of these plates in the proximal humerus has yet to be fully described. There is a need to compare the biomechanical properties of efficacy of plate fixation with or without locking screws for surgery of two-part proximal humerus fractures. Multiple-plane locking plate and cloverleaf plate designs were tested to determine their ability to maintain fixation on the humeral head. Eight matched pairs of cadaveric shoulders with 7-millimeter osteotomy defects at the surgical neck simulating two-part fractures of the proximal humerus were loaded to failure in thirty degrees of glenohumeral abduction. One side was repaired with a proximal humerus locking plate and the other with a cloverleaf plate. The rotator cuff musculature was then loaded via a servo-hydraulic testing machine under displacement control to simulate the deforming forces present in vivo. The average maximum load to failure was greater in proximal humerus locking plates than in cloverleaf plates (876 versus 712; P=0.04). In the cadaveric, two-part proximal humerus fracture model that was created, the locking plate displayed significantly greater holding power of the humeral head. Clinical relevance is unproven but may be manifested in vivo as improved early range of motion exercises and functional outcome.

Paper 108: Evaluation of Quantitative Magnetic Resonance Imaging, Biochemical and Mechanical Properties of Trypsin Treated …

Journal of Bone & Joint …, 2010

Purpose: Since the human intervertebral disc (IVD) is loaded in compression for approximately 16h... more