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Aldemar Andres Hegewald - One of the best experts on this subject based on the ideXlab platform.
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enhancing tissue repair in annulus fibrosus defects of the intervertebral disc analysis of a bio integrative annulus implant in an in vivo Ovine Model
2015Co-Authors: Aldemar Andres Hegewald, Fabian Medved, Daxiong Feng, Charalambos Tsagogiorgas, Genevieve Schindler, Marcus J. Trunk, Christian Kaps, Anja Beierfus, Demissew Shenegelegn MernAbstract:Annulus fibrosus repair techniques for the intervertebral disc (IVD) address the unsolved problem of reherniation after IVD herniation and might facilitate the development of nucleus pulposus replacement techniques for IVD diseases. This study investigates the suitability of a bio-integrative annulus implant.Standardized box defects were applied to the annulus L3/4 and L4/5 of 16 sheep, followed by randomized insertion of the textile polyglycolic acid/polyvinylidene fluoride annulus implant in one of the defects. Explantation was conducted after 2, 6 and 12 weeks, followed by provocative pressure testing and histological analysis. At 2 weeks' follow-up, all specimens of the control defect group demonstrated uncontained herniated nucleus pulposus tissue in the annulus defects. For the treated specimens, the annulus implant consistently provided an effective barrier for herniating nucleus pulposus tissue, with no implant dislocation at all time-points. After 2 weeks, a homogeneous cell infiltration of the annulus implant was observed, leading to a progressive directional matrix build-up. Repair tissue thickness was significantly stronger with the annulus implant at all follow-ups (p < 0.01). No pronounced foreign body reaction and no difference in the amount of supra-annular scar tissue over the defect sites were observed. The implantation procedure inflicted annulus damage adjacent to the defect. At later time-points, however, no difference in comparison with the control defect group was evident. The investigated biointegrative annulus implant showed promising results with regard to biointegration, enhancement of repair tissue and function as a mechanical barrier in an Ovine Model.
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Enhancing tissue repair in annulus fibrosus defects of the intervertebral disc: analysis of a bio-integrative annulus implant in an in-vivo Ovine Model.
2013Co-Authors: Aldemar Andres Hegewald, Fabian Medved, Daxiong Feng, Charalambos Tsagogiorgas, Anja Beierfuß, Genevieve Schindler, Marcus J. Trunk, Christian Kaps, Demissew Shenegelegn Mern, Claudius ThoméAbstract:Annulus fibrosus repair techniques for the intervertebral disc (IVD) address the unsolved problem of reherniation after IVD herniation and might facilitate the development of nucleus pulposus replacement techniques for IVD diseases. This study investigates the suitability of a bio-integrative annulus implant.Standardized box defects were applied to the annulus L3/4 and L4/5 of 16 sheep, followed by randomized insertion of the textile polyglycolic acid/polyvinylidene fluoride annulus implant in one of the defects. Explantation was conducted after 2, 6 and 12 weeks, followed by provocative pressure testing and histological analysis. At 2 weeks’ follow-up, all specimens of the control defect group demonstrated uncontained herniated nucleus pulposus tissue in the annulus defects. For the treated specimens, the annulus implant consistently provided an effective barrier for herniating nucleus pulposus tissue, with no implant dislocation at all time-points. After 2 weeks, a homogeneous cell infiltration of the annulus implant was observed, leading to a progressive directional matrix build-up. Repair tissue thickness was significantly stronger with the annulus implant at all follow-ups (p < 0.01). No pronounced foreign body reaction and no difference in the amount of supra-annular scar tissue over the defect sites were observed. The implantation procedure inflicted annulus damage adjacent to the defect. At later time-points, however, no difference in comparison with the control defect group was evident. The investigated biointegrative annulus implant showed promising results with regard to biointegration, enhancement of repair tissue and function as a mechanical barrier in an Ovine Model. © 2013 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd.
William R Walsh - One of the best experts on this subject based on the ideXlab platform.
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biphasic calcium phosphate with submicron surface topography in an Ovine Model of instrumented posterolateral spinal fusion
2018Co-Authors: Lukas A Van Dijk, Rongquan Duan, Xiaoman Luo, Davide Barbieri, Matthew H Pelletier, Chris Christou, Antoine J W P Rosenberg, Huipin Yuan, Florence Barrerrede Groot, William R WalshAbstract:As spinal fusions require large volumes of bone graft, different bone graft substitutes are being investigated as alternatives. A subclass of calcium phosphate materials with submicron surface topography has been shown to be a highly effective bone graft substitute. In this work, a commercially available biphasic calcium phosphate (BCP) with submicron surface topography (MagnetOs; Kuros Biosciences BV) was evaluated in an Ovine Model of instrumented posterolateral fusion. The material was implanted stand-alone, either as granules (BCPgranules) or as granules embedded within a fast-resorbing polymeric carrier (BCPputty) and compared to autograft bone (AG). Twenty-five adult, female Merino sheep underwent posterolateral fusion at L2-3 and L4-5 levels with instrumentation. After 6, 12, and 26 weeks, outcomes were evaluated by manual palpation, range of motion (ROM) testing, micro-computed tomography, histology and histomorphometry. Fusion assessment by manual palpation 12 weeks after implantation revealed 100% fusion rates in all treatment groups. The three treatment groups showed a significant decrease in lateral bending at the fusion levels at 12 weeks (P < 0.05) and 26 weeks (P < 0.001) compared to the 6 week time-point. Flexion-extension and axial rotation were also reduced over time, but statistical significance was only reached in flexion-extension for AG and BCPputty between the 6 and 26 week time-points (P < 0.05). No significant differences in ROM were observed between the treatment groups at any of the time-points investigated. Histological assessment at 12 weeks showed fusion rates of 75%, 92%, and 83% for AG, BCPgranules and BCPputty, respectively. The fusion rates were further increased 26 weeks postimplantation. Similar trends of bone growth were observed by histomorphometry. The fusion mass consisted of at least 55% bone for all treatment groups 26 weeks after implantation. These results suggest that this BCP with submicron surface topography, in granules or putty form, is a promising alternative to autograft for spinal fusion.
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in vivo implant fixation of carbon fiber reinforced peek hip prostheses in an Ovine Model
2013Co-Authors: Ichiro Nakahara, Nicky Bertollo, William R Walsh, Masaki Takao, Shunichi Bandoh, Nobuhiko SuganoAbstract:Carbon fiber-reinforced polyetheretherketone (CFR/PEEK) is theoretically suitable as a material for use in hip prostheses, offering excellent biocompatibility, mechanical properties, and the absence of metal ions. To evaluate in vivo fixation methods of CFR/PEEK hip prostheses in bone, we examined radiographic and histological results for cementless or cemented CFR/PEEK hip prostheses in an Ovine Model with implantation up to 52 weeks. CFR/PEEK cups and stems with rough-textured surfaces plus hydroxyapatite (HA) coatings for cementless fixation and CFR/PEEK cups and stems without HA coating for cement fixation were manufactured based on Ovine computed tomography (CT) data. Unilateral total hip arthroplasty was performed using cementless or cemented CFR/PEEK hip prostheses. Five cementless cups and stems and six cemented cups and stems were evaluated. On the femoral side, all cementless stems demonstrated bony ongrowth fixation and all cemented stems demonstrated stable fixation without any gaps at both the bone-cement and cement-stem interfaces. All cementless cases and four of the six cemented cases showed minimal stress shielding. On the acetabular side, two of the five cementless cups demonstrated bony ongrowth fixation. Our results suggest that both cementless and cemented CFR/PEEK stems work well for fixation. Cup fixation may be difficult for both cementless and cemented types in this Ovine Model, but bone ongrowth fixation on the cup was first seen in two cementless cases. Cementless fixation can be achieved using HA-coated CFR/PEEK implants, even under load-bearing conditions. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 485–492, 2013
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a comparison of the thermal properties of 2 and 3 fluted drills and the effects on bone cell viability and screw pull out strength in an Ovine Model
2010Co-Authors: Nicky Bertollo, Hadley R M Milne, Liam P Ellis, Paul Stephens, R M Gillies, William R WalshAbstract:Abstract Background Drilling of bone is associated with an increase in temperature of the surrounding bone which may result in osteonecrosis. Methods In this study, cutting efficiency and thermal properties of one 2-fluted drill and two 3-fluted drills were determined in vitro using a porcine Model. Drills were then used to create pilot holes in an in vivo Ovine Model to facilitate implantation of pedicle screws. The effect of the characteristic thermal profiles of each drill on cortical bone cell viability and screw pull-out strength was then assessed. Findings Cutting efficiencies of both 3-fluted designs were found to be greater than that of the 2-fluted drill, but this did not translate into a decrease in the maximum temperatures during drilling for both drills. Histologically, no empty osteocyte lacunae were seen at 2 or 4 weeks, suggesting that temperatures were not sufficiently high enough to induce thermonecrosis in the Ovine tibia. No differences were found in the pull-out strength of the screws. Interpretation Both 2- and 3-fluted drills are currently in clinical use. Despite the theoretical advantage that 3-fluted drills possess over their 2-fluted counterparts, there is a lack of evidence in the literature in support of their use. In this study the observed increases in cutting efficiency of the 3-fluted drills tested did not translate into a reduction in heat generation or improvement in bone healing or screw fixation.
Robert C Gorman - One of the best experts on this subject based on the ideXlab platform.
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in vitro mitral valve simulator mimics systolic valvular function of chronic ischemic mitral regurgitation Ovine Model
2013Co-Authors: Andrew W Siefert, Jeremy R. Mcgarvey, Joseph H Gorman, Robert C Gorman, Jeanpierre Rabbah, Kevin J Koomalsingh, Steven A Touchton, Neelakantan Saikrishnan, Ajit P YoganathanAbstract:Background This study was undertaken to evaluate an in vitro mitral valve (MV) simulator's ability to mimic the systolic leaflet coaptation, regurgitation, and leaflet mechanics of a healthy Ovine Model and an Ovine Model with chronic ischemic mitral regurgitation (IMR). Methods Mitral valve size and geometry of both healthy Ovine animals and those with chronic IMR were used to recreate systolic MV function in vitro. A2-P2 coaptation length, coaptation depth, tenting area, anterior leaflet strain, and MR were compared between the animal groups and valves simulated in the bench-top Model. Results For the control conditions, no differences were observed between the healthy animals and simulator in coaptation length (p = 0.681), coaptation depth (p = 0.559), tenting area (p = 0.199), and anterior leaflet strain in the radial (p = 0.230) and circumferential (p = 0.364) directions. For the chronic IMR conditions, no differences were observed between the Models in coaptation length (p = 0.596), coaptation depth (p = 0.621), tenting area (p = 0.879), and anterior leaflet strain in the radial (p = 0.151) and circumferential (p = 0.586) directions. MR was similar between IMR Models, with an asymmetrical jet originating from the tethered A3-P3 leaflets. Conclusions This study is the first to demonstrate the effectiveness of an in vitro simulator to emulate the systolic valvular function and mechanics of a healthy Ovine Model and one with chronic IMR. The in vitro IMR Model provides the capability to recreate intermediary and exacerbated levels of annular and subvalvular distortion for which IMR repairs can be simulated. This system provides a realistic and controllable test platform for the development and evaluation of current and future IMR repairs.
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an Ovine Model of pulmonary insufficiency and right ventricular outflow tract dilatation
2012Co-Authors: J D Robb, Matthew A. Harris, Yoav Dori, Robert C Gorman, Kevin J Koomalsingh, Masahito Minakawa, E Rodriguez, Takashi Shuto, Matthew J GillespieAbstract:The treatment of patients with pulmonary insufficiency (PI) following reconstructive surgery of the right ventricular outflow tract (RVOT) for congenital heart disease remains an important clinical challenge. Longstanding PI typically leads to right ventricular (RV) dilatation, exercise intolerance, ventricular arrhythmias, and heart failure. This adverse reModeling of the right ventricle is a common indication for late reintervention following surgical repair of the tetralogy of Fallot (ToF) (1-10). A homograft conduit or bioprosthetic valve replacement are commonly used for the surgical treatment of RVOT dysfunction (11) although, due to their tendency to degenerate and calcify, these prostheses often fail very quickly. Such concern over prosthesis longevity frequently delays the decision to refer patients for surgery, thereby subjecting them to ongoing PI and the risk of irreversible RV damage. This clinical dilemma has led to the development of minimally invasive approaches to PI following RVOT reconstruction for congenital heart disease. The first implantation of a transcatheter pulmonary valve in animals, and subsequently in humans, was made in 2000 (12,13). Yet, increasing experience with transcatheter pulmonary valve placement has demonstrated the benefits and limitations of this therapy (1,14-21). It has been shown that the percutaneous implantation of valved stents in failed right ventricle to pulmonary artery (PA) conduits represents an effective means of rehabilitating a surgically placed homograft. The patients benefit in both the short and medium terms, with improvements in symptoms, aerobic and anaerobic exercise capacity, RV volumes and systolic and diastolic function, without incurring the risk of open-heart surgery (18,22-24). Percutaneous pulmonary valve replacement does, however, have certain limitations, with the use of this technique generally having been limited to ‘conduit rehabilitation’. Currently available devices - namely, the Melody® valve (Medtronic, Minneapolis, MN, USA) and the SAPIEN® valve (Edwards Lifesciences, Irvine, CA, USA) - have maximum functional diameters of 22 mm and 26 mm, respectively, and are therefore not suitable for dilated RVOTs (21). Unfortunately, massively dilated RVOTs are commonly encountered in clinical practice, particularly in patients who have undergone transannular patch repair of ToF. Although attempts have been made to downsize the large outflow tracts - either surgically, or with a filler device to facilitate valved-stent deployment (16,25) - these procedures have met with only limited success. In addition, the RVOT is often not only dilated but also highly asymmetrical and distorted, which makes the placement of any device difficult. Thus, a dilated and distorted RVOT remains a considerable clinical challenge, and provides a fertile area for study. In order to permit laboratory investigations of this important clinical problem, an Ovine Model of pulmonary valve insufficiency with a dilated RVOT has been developed that closely replicates the common late clinical presentation for ToF patients who previously would have been treated with a transannular patch.
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elimination of ischemic mitral regurgitation does not alter long term left ventricular reModeling in the Ovine Model
2010Co-Authors: Kanji Matsuzaki, Joseph H Gorman, Masato Morita, Hirotsugu Hamamoto, Mio Noma, Daniel J Robb, Matthew J Gillespie, Robert C GormanAbstract:Background The efficacy of annuloplasty for ischemic mitral regurgitation (IMR) has been difficult to establish. Using an established Ovine Model of IMR, we tested the ability of ring annuloplasty to durably relieve IMR and reverse or limit progression of left ventricular (LV) reModeling during a clinically relevant follow-up period. Methods A posterolateral infarction known to result in chronic IMR was initiated in 33 sheep. Echocardiography was used to assess LV end diastolic and systolic volumes and IMR (0 to 4 scale) before and 8 weeks after infarction. Eight weeks after infarction, 20 surviving animals with ≥2+ IMR were randomized (1:1) to no treatment or undersized, semi-rigid, complete ring annuloplasty placement. LV reModeling and IMR were assessed at 4 and 6 months after infarction. Results All animals had similarly sized LV volumes at baseline (end systolic, 27.8 ± 4.6 mL; end diastolic, 53.5 ± 6.4 mL). The 20 randomized animals survived to complete the study. The degree of IMR before randomization was similar in treatment (2.6 ± 0.4) and control (2.8 ± 0.3) groups. At the 6-month follow-up, the degree of IMR was significantly less in the annuloplasty group (0.3 ± 0.1 vs 3.4 ± 0.6); however, LV volumes in the treatment group were not significantly different from the control group (end systolic, 82.1 ± 15.6 vs 81.1 ± 8.6 mL; end diastolic, 110.4 ± 22.1 vs 111.1 ± 16.5 mL). Conclusions In a clinically relevant Ovine Model of IMR, annuloplasty provides durable relief from IMR during an extended follow-up period but does not significantly influence LV reModeling.
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annuloplasty ring selection for chronic ischemic mitral regurgitation lessons from the Ovine Model
2003Co-Authors: Joseph H Gorman, Robert C Gorman, Benjamin M. Jackson, Martin G St Johnsutton, Yoshiharu Enomoto, Henry L EdmundsAbstract:Abstract Background Chronic ischemic mitral regurgitation (CIMR) is poorly understood and repair operations are often unsatisfactory. This study elucidates the mechanism of CIMR in an Ovine Model. Methods Sonomicrometry array localization measured the three-dimensional geometry of the mitral annulus and subvalvular apparatus in five sheep before and 8 weeks after a posterior infarction of the left ventricle that produced progressive severe CIMR. Results End systolic annular area increased from 647 ± 44 mm 2 to 1,094 ± 173 mm 2 ( p = 0.01). Annular dilatation occurred equally along the anterior (47.0 ± 5.6 mm to 60.2 ± 4.9 mm, p = 0.001) and posterior (53.8 ± 3.1 mm to 68.5 ± 8.4 mm, p = 0.005) portions of the annulus. The tip of the anterior papillary muscle moved away from both the anterior and posterior commissures by 5.2 ± 3.2 mm ( p = 0.021) and 7.3 ± 2.2 mm ( p = 0.002), respectively. The distance from the tip of the posterior papillary muscle to the anterior commissure increased by 11.0 ± 5.7 mm ( p = 0.032) while the distance from the tip of the posterior papillary muscle to the posterior commissure remained constant. Conclusions Progressive dilatation of both the anterior and posterior mitral annuli, increased annular area, and asymmetric ventricular dilatation combine to cause CIMR by distortion of mitral valve geometry and tethering of leaflet coaptation. Therefore complete ring annuloplasty may be superior to partial annuloplasty in the treatment of CIMR.
Joseph H Gorman - One of the best experts on this subject based on the ideXlab platform.
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in vitro mitral valve simulator mimics systolic valvular function of chronic ischemic mitral regurgitation Ovine Model
2013Co-Authors: Andrew W Siefert, Jeremy R. Mcgarvey, Joseph H Gorman, Robert C Gorman, Jeanpierre Rabbah, Kevin J Koomalsingh, Steven A Touchton, Neelakantan Saikrishnan, Ajit P YoganathanAbstract:Background This study was undertaken to evaluate an in vitro mitral valve (MV) simulator's ability to mimic the systolic leaflet coaptation, regurgitation, and leaflet mechanics of a healthy Ovine Model and an Ovine Model with chronic ischemic mitral regurgitation (IMR). Methods Mitral valve size and geometry of both healthy Ovine animals and those with chronic IMR were used to recreate systolic MV function in vitro. A2-P2 coaptation length, coaptation depth, tenting area, anterior leaflet strain, and MR were compared between the animal groups and valves simulated in the bench-top Model. Results For the control conditions, no differences were observed between the healthy animals and simulator in coaptation length (p = 0.681), coaptation depth (p = 0.559), tenting area (p = 0.199), and anterior leaflet strain in the radial (p = 0.230) and circumferential (p = 0.364) directions. For the chronic IMR conditions, no differences were observed between the Models in coaptation length (p = 0.596), coaptation depth (p = 0.621), tenting area (p = 0.879), and anterior leaflet strain in the radial (p = 0.151) and circumferential (p = 0.586) directions. MR was similar between IMR Models, with an asymmetrical jet originating from the tethered A3-P3 leaflets. Conclusions This study is the first to demonstrate the effectiveness of an in vitro simulator to emulate the systolic valvular function and mechanics of a healthy Ovine Model and one with chronic IMR. The in vitro IMR Model provides the capability to recreate intermediary and exacerbated levels of annular and subvalvular distortion for which IMR repairs can be simulated. This system provides a realistic and controllable test platform for the development and evaluation of current and future IMR repairs.
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elimination of ischemic mitral regurgitation does not alter long term left ventricular reModeling in the Ovine Model
2010Co-Authors: Kanji Matsuzaki, Joseph H Gorman, Masato Morita, Hirotsugu Hamamoto, Mio Noma, Daniel J Robb, Matthew J Gillespie, Robert C GormanAbstract:Background The efficacy of annuloplasty for ischemic mitral regurgitation (IMR) has been difficult to establish. Using an established Ovine Model of IMR, we tested the ability of ring annuloplasty to durably relieve IMR and reverse or limit progression of left ventricular (LV) reModeling during a clinically relevant follow-up period. Methods A posterolateral infarction known to result in chronic IMR was initiated in 33 sheep. Echocardiography was used to assess LV end diastolic and systolic volumes and IMR (0 to 4 scale) before and 8 weeks after infarction. Eight weeks after infarction, 20 surviving animals with ≥2+ IMR were randomized (1:1) to no treatment or undersized, semi-rigid, complete ring annuloplasty placement. LV reModeling and IMR were assessed at 4 and 6 months after infarction. Results All animals had similarly sized LV volumes at baseline (end systolic, 27.8 ± 4.6 mL; end diastolic, 53.5 ± 6.4 mL). The 20 randomized animals survived to complete the study. The degree of IMR before randomization was similar in treatment (2.6 ± 0.4) and control (2.8 ± 0.3) groups. At the 6-month follow-up, the degree of IMR was significantly less in the annuloplasty group (0.3 ± 0.1 vs 3.4 ± 0.6); however, LV volumes in the treatment group were not significantly different from the control group (end systolic, 82.1 ± 15.6 vs 81.1 ± 8.6 mL; end diastolic, 110.4 ± 22.1 vs 111.1 ± 16.5 mL). Conclusions In a clinically relevant Ovine Model of IMR, annuloplasty provides durable relief from IMR during an extended follow-up period but does not significantly influence LV reModeling.
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annuloplasty ring selection for chronic ischemic mitral regurgitation lessons from the Ovine Model
2003Co-Authors: Joseph H Gorman, Robert C Gorman, Benjamin M. Jackson, Martin G St Johnsutton, Yoshiharu Enomoto, Henry L EdmundsAbstract:Abstract Background Chronic ischemic mitral regurgitation (CIMR) is poorly understood and repair operations are often unsatisfactory. This study elucidates the mechanism of CIMR in an Ovine Model. Methods Sonomicrometry array localization measured the three-dimensional geometry of the mitral annulus and subvalvular apparatus in five sheep before and 8 weeks after a posterior infarction of the left ventricle that produced progressive severe CIMR. Results End systolic annular area increased from 647 ± 44 mm 2 to 1,094 ± 173 mm 2 ( p = 0.01). Annular dilatation occurred equally along the anterior (47.0 ± 5.6 mm to 60.2 ± 4.9 mm, p = 0.001) and posterior (53.8 ± 3.1 mm to 68.5 ± 8.4 mm, p = 0.005) portions of the annulus. The tip of the anterior papillary muscle moved away from both the anterior and posterior commissures by 5.2 ± 3.2 mm ( p = 0.021) and 7.3 ± 2.2 mm ( p = 0.002), respectively. The distance from the tip of the posterior papillary muscle to the anterior commissure increased by 11.0 ± 5.7 mm ( p = 0.032) while the distance from the tip of the posterior papillary muscle to the posterior commissure remained constant. Conclusions Progressive dilatation of both the anterior and posterior mitral annuli, increased annular area, and asymmetric ventricular dilatation combine to cause CIMR by distortion of mitral valve geometry and tethering of leaflet coaptation. Therefore complete ring annuloplasty may be superior to partial annuloplasty in the treatment of CIMR.
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an Ovine Model of postinfarction dilated cardiomyopathy
2002Co-Authors: Sina L Moainie, Joseph H Gorman, Benjamin M. Jackson, Martin G St Johnsutton, Sloane T Guy, Frank W Bowen, Theodore Plappert, Navneet Narula, Jagat Narula, Henry L EdmundsAbstract:Abstract Background . Coronary arterial disease is the major cause of congestive heart failure, but suitable animal Models of postinfarction, dilated cardiomyopathy do not exist. This article describes an Ovine Model that develops after an anterobasal infarction. Methods . The distribution of Ovine myocardium supplied by the first two diagonal branches of the left homonymous artery were determined in 20 slaughterhouse hearts and eight live sheep using methylene blue and tetrazolium injections, respectively. Seven additional animals had the infarction and underwent serial hemodynamic, microsphere and echocardiographic studies more than 8 weeks and histologic studies at the eighth week. Infarcts represented 24.6% ± 4.7% and 23.9% ± 2.2% of the left ventricular mass in slaughterhouse and live hearts, respectively. Results . During reModeling, left ventricular end-systolic and end-diastolic volumes increased 115% and 73%, respectively, ejection fraction decreased from 41.2% ± 6.7% to 29.1% ± 5.7%, systolic wall thickening remote from the infarct decreased by 68%, sphericity index increased from 0.465 ± 0.088 to 0.524 ± 0.038, and left ventricular end-diastolic pressure increased from 1.7 ± 1.0 to 8.2 ± 3.5 mm Hg. Serial microsphere measurements documented normal blood flow (1.34 mL/g per minute) to all uninfarcted myocardium and 22% of normal to the infarct. Viable myocardium showed mild interstitial fibrosis. Conclusions . This Ovine Model meets all criteria for postinfarction, dilated cardiomyopathy and has the advantages of controlling for variations in coronary arterial anatomy, collateral vascularity, and differences in the numbers, location, and severity of atherosclerotic lesions that confound human studies of the pathogenesis of this disease. This simple Model contains only infarcted and fully perfused, hypocontractile myocardium produced by a moderate-sized, regional infarction.
Demissew Shenegelegn Mern - One of the best experts on this subject based on the ideXlab platform.
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enhancing tissue repair in annulus fibrosus defects of the intervertebral disc analysis of a bio integrative annulus implant in an in vivo Ovine Model
2015Co-Authors: Aldemar Andres Hegewald, Fabian Medved, Daxiong Feng, Charalambos Tsagogiorgas, Genevieve Schindler, Marcus J. Trunk, Christian Kaps, Anja Beierfus, Demissew Shenegelegn MernAbstract:Annulus fibrosus repair techniques for the intervertebral disc (IVD) address the unsolved problem of reherniation after IVD herniation and might facilitate the development of nucleus pulposus replacement techniques for IVD diseases. This study investigates the suitability of a bio-integrative annulus implant.Standardized box defects were applied to the annulus L3/4 and L4/5 of 16 sheep, followed by randomized insertion of the textile polyglycolic acid/polyvinylidene fluoride annulus implant in one of the defects. Explantation was conducted after 2, 6 and 12 weeks, followed by provocative pressure testing and histological analysis. At 2 weeks' follow-up, all specimens of the control defect group demonstrated uncontained herniated nucleus pulposus tissue in the annulus defects. For the treated specimens, the annulus implant consistently provided an effective barrier for herniating nucleus pulposus tissue, with no implant dislocation at all time-points. After 2 weeks, a homogeneous cell infiltration of the annulus implant was observed, leading to a progressive directional matrix build-up. Repair tissue thickness was significantly stronger with the annulus implant at all follow-ups (p < 0.01). No pronounced foreign body reaction and no difference in the amount of supra-annular scar tissue over the defect sites were observed. The implantation procedure inflicted annulus damage adjacent to the defect. At later time-points, however, no difference in comparison with the control defect group was evident. The investigated biointegrative annulus implant showed promising results with regard to biointegration, enhancement of repair tissue and function as a mechanical barrier in an Ovine Model.
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Enhancing tissue repair in annulus fibrosus defects of the intervertebral disc: analysis of a bio-integrative annulus implant in an in-vivo Ovine Model.
2013Co-Authors: Aldemar Andres Hegewald, Fabian Medved, Daxiong Feng, Charalambos Tsagogiorgas, Anja Beierfuß, Genevieve Schindler, Marcus J. Trunk, Christian Kaps, Demissew Shenegelegn Mern, Claudius ThoméAbstract:Annulus fibrosus repair techniques for the intervertebral disc (IVD) address the unsolved problem of reherniation after IVD herniation and might facilitate the development of nucleus pulposus replacement techniques for IVD diseases. This study investigates the suitability of a bio-integrative annulus implant.Standardized box defects were applied to the annulus L3/4 and L4/5 of 16 sheep, followed by randomized insertion of the textile polyglycolic acid/polyvinylidene fluoride annulus implant in one of the defects. Explantation was conducted after 2, 6 and 12 weeks, followed by provocative pressure testing and histological analysis. At 2 weeks’ follow-up, all specimens of the control defect group demonstrated uncontained herniated nucleus pulposus tissue in the annulus defects. For the treated specimens, the annulus implant consistently provided an effective barrier for herniating nucleus pulposus tissue, with no implant dislocation at all time-points. After 2 weeks, a homogeneous cell infiltration of the annulus implant was observed, leading to a progressive directional matrix build-up. Repair tissue thickness was significantly stronger with the annulus implant at all follow-ups (p < 0.01). No pronounced foreign body reaction and no difference in the amount of supra-annular scar tissue over the defect sites were observed. The implantation procedure inflicted annulus damage adjacent to the defect. At later time-points, however, no difference in comparison with the control defect group was evident. The investigated biointegrative annulus implant showed promising results with regard to biointegration, enhancement of repair tissue and function as a mechanical barrier in an Ovine Model. © 2013 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd.
