Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (22)
- Beitrag zu einem Tagungsband (15)
- Beitrag zu einem Sammelband (11)
- Vortrag (8)
- Posterpräsentation (7)
- Sonstiges (1)
- Forschungsbericht (1)
Schlagworte
- Computed tomography (12)
- Computertomographie (6)
- Computer Tomographie (3)
- Fire resistance (3)
- Intumescence (3)
- Osteoporotic vertebral fracture (3)
- Simulation (3)
- X-ray refraction (3)
- Aerospace (2)
- Bone regeneration (2)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (8)
Performance of calcium phosphate cements in the augmentation of sheep vertebrae - An ex vivo study
(2021)
Oil-based calcium phosphate cement (Paste-CPC) shows not only prolonged shelf life and injection times, but also improved cohesion and reproducibility during application, while retaining the advantages of fast setting, mechanical strength, and biocompatibility. In addition, poly(L-lactideco-glycolide) (PLGA) fiber reinforcement may decrease the risk for local extrusion. Bone defects (diameter 5 mm; depth 15 mm) generated ex vivo in lumbar (L) spines of female Merino sheep (2–4 years) were augmented using: (i) water-based CPC with 10% PLGA fiber reinforcement (L3); (ii) Paste-CPC (L4); or (iii) clinically established polymethylmethacrylate (PMMA) bone cement (L5). Untouched (L1) and empty vertebrae (L2) served as controls. Cement performance was analyzed using micro-computed tomography, histology, and biomechanical testing. Extrusion was comparable for Paste-CPC(-PLGA) and PMMA, but significantly lower for CPC + PLGA. Compressive strength and Young’s modulus were similar for Paste-CPC and PMMA, but significantly higher compared to those for empty defects and/or CPC + PLGA. Expectedly, all experimental groups showed significantly or numerically lower compressive strength and Young’s modulus than those of untouched controls. Ready-to-use Paste-CPC demonstrates a performance similar to that of PMMA, but improved biomechanics compared to those of water-based CPC + PLGA, expanding the therapeutic arsenal for bone defects. O, significantly lower extrusion of CPC + PLGA fibers into adjacent lumbar spongiosa may help to reduce the risk of local extrusion in spinal surgery.
To assess the clinical course of a sheep stifle joint model for osteochondral (OC) defects, medial femoral condyles (MFC) were exposed without patella luxation using medial parapatellar skin (3–4 cm) and deep incisions (2–3 cm). Two defects (7 mm diameter; 10 mm depth; OC punch) were left empty or refilled with osteochondral autologous transplantation cylinders (OATS) and explanted after six weeks. Incision-to-suture time, anesthesia time, and postoperative wound or impairment scores were compared to those in sham-operated animals. Implant performance was assessed by X-ray, micro-computed tomography, histology, and immunohistology (collagens 1, 2; aggrecan). There were no surgery-related infections or patellar luxations. Operation, anesthesia, and time to complete stand were short (0.5, 1.4, and 1.5 h, respectively). The wound trauma score was low (0.4 of maximally 4; day 7). Empty-defect and OATS animals reached an impairment score of 0 significantly later than sham animals (7.4 and 4.0 days, respectively, versus 1.5 days). Empty defects showed incomplete healing and dedifferentiation/heterotopic differentiation; OATS-filled defects displayed advanced bone healing with remaining cartilage gaps and orthotopic expression of bone and cartilage markers. Minimally-invasive, medial parapatellar surgery of OC defects on the sheep MFC allows rapid and low-trauma recovery and appears well-suited for implant testing.
Subject of this investigation is the in-situ evolution of pore volume and pore size distribution in Ytong (a porous concrete material) under increasing pressure with two different non-destructive analytical methods: Nuclear Magnetic Resonance (NMR) and X-ray Computed Tomography (CT). For both methods special strain devices to apply external pressure were constructed. The results from the two techniques yield complementary information on the pore size distribution and allows covering different pore size regions.
Minimally invasive injection of calcium phosphate cement into bone defects in aged sheep vertebrae has been used as a model for the treatment of osteoporotic vertebral fractures. One of the therapeutic criteria is a compression test of non-treated or treated vertebral bodies. In the present study, an in situ compression test with a stepwise load increase was performed with small spongiosa cylinders from the vertebrae under continuous monitoring by μCT. This allows localization of bone cracks and the visualization of correct placement and form of the bone cylinder. In addition, the effects of an uneven load distribution on the sample due to an irregular shape and a subsequent underperformance of the test sample can be excluded by controlling its shape under increasing load. There was a good agreement between the measured data and those obtained by simulated load-dependent transformation on the basis of a digital volume correlation between consecutive compression tests on the bone surface under the assumption of homogeneous bone material. Mechanic simulation was executed by directly using structural voxel data, resulting in maps of Von Mise stresses and predicted displacements.
Mit Hilfe der Computertomographie können zerstörungsfrei Bilder des Bodengefüges gewonnen werden. Sowohl die verschiedene Dichte des Bodens als auch Hohlräume und Poren sowie Wurzeln und anderes organisches Material können dargestellt werden. Die Wurzeln werden dabei lagerichtig wiedergegeben. Begrenzt wird dieses durch die Ortsauflösung des jeweiligen Tomogramms.
Ist die Methode für eine Fragestellung aus der landwirtschaftlichen Praxis – Einfluss der Bodenbearbeitung auf das Wurzelbild von Raps – geeignet?
Untersuchungen haben gezeigt, dass sich ältere Schafe gut als Modell für die mi-nimalinvasive Behandlung von Osteoporose eignen [1]. Um einen Behandlungs-effekt nachzuweisen, wird dabei unter anderem die Belastungsfähigkeit des Kno-chens durch Druckversuche an kleinen Zylindern aus den behandelten und unbe-handelten Knochen bestimmt. Diese hatten hier einen Durchmesser von 10 mm und eine Höhe von 13 mm. Für den in-situ Druckversuch wurde eine Deben CT5000 verwendet. In einer Serie von Druckerhöhungen wurden die Proben je-weils tomographiert. Dabei ergab sich zunächst, dass mit der µCT innerhalb der Knochen im oberen und unteren Bereich schon Brüche nachgewiesen werden können, obwohl die gemessene Kraftaufnahmekurve keine Unstetigkeit zeigt. Deswegen wurden die starren Probenaufnehmer der Deben Anordnung durch bewegliche Aufnehmer ergänzt, die eine leichte Verkippung der belasteten Ober-flächen ausgleichen können. Ein Vergleich der gemessenen und der aus den µCT-Daten berechneten Verschiebungsfelder ergab trotz der komplexen Struktur der Knochen gute Übereinstimmungen. Diese Verschiebungen wurden dann mit den aus den µCT Daten simulierten mechanischen Druckversuchen, Von-Mise-Spannungen und daraus berechneten Verschiebungen verglichen. (VGStudioMax Simulation).
Untersuchungen haben gezeigt, dass sich ältere Schafe gut als Modell für die mi-nimalinvasive Behandlung von Osteoporose eignen [1]. Um einen Behandlungs-effekt nachzuweisen, wird dabei unter anderem die Belastungsfähigkeit des Kno-chens durch Druckversuche an kleinen Zylindern aus den behandelten und unbe-handelten Knochen bestimmt. Diese hatten hier einen Durchmesser von 10 mm und eine Höhe von 13 mm. Für den in-situ Druckversuch wurde eine Deben CT5000 verwendet. In einer Serie von Druckerhöhungen wurden die Proben je-weils tomographiert. Dabei ergab sich zunächst, dass mit der µCT innerhalb der Knochen im oberen und unteren Bereich schon Brüche nachgewiesen werden können, obwohl die gemessene Kraftaufnahmekurve keine Unstetigkeit zeigt. Deswegen wurden die starren Probenaufnehmer der Deben Anordnung durch bewegliche Aufnehmer ergänzt, die eine leichte Verkippung der belasteten Ober-flächen ausgleichen können. Ein Vergleich der gemessenen und der aus den µCT-Daten berechneten Verschiebungsfelder ergab trotz der komplexen Struktur der Knochen gute Übereinstimmungen. Diese Verschiebungen wurden dann mit den aus den µCT Daten simulierten mechanischen Druckversuchen, Von-Mise-Spannungen und daraus berechneten Verschiebungen verglichen. (VGStudioMax Simulation).
BACKGROUND CONTEXT: Targeted delivery of osteoinductive bone morphogenetic Proteins (eg, GDF5) in bioresorbable calcium phosphate cement (CPC), potentially suitable for vertebroplasty and kyphoplasty of osteoporotic vertebral fractures, may be required to counteract augmented local bone catabolism and to support complete bone regeneration. The biologically optimized GDF5 Mutant BB-1 may represent an attractive drug candidate for this purpose.
PURPOSE: The aim of the current study was to test an injectable, poly (l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming CPC containing low-dose BB-1 in a sheep lumbar osteopenia model.
STUDY DESIGN/ SETTING: This is a prospective experimental animal study.
METHODS: Bone defects (diameter 5 mm) were generated in aged, osteopenic female sheep and were filled with fiber-reinforced CPC alone (L4; CPC+fibers) or with CPC containing different dosages.
BACKGROUND CONTEXT:
Biodegradable calcium phosphate cement (CPC) represents a promising option for the surgical treatment of osteoporotic vertebral fractures. Because of augmented local bone catabolism, however, additional targeted delivery of bone morphogenetic proteins with the CPC may be needed to promote rapid and complete bone regeneration.
PURPOSE:
In the present study, an injectable, poly(l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming cement (CPC) containing the bone morphogenetic Protein GDF5 was tested in a sheep lumbar osteopenia model.
STUDY DESIGN/SETTING:
This is a prospective experimental animal study
METHODS:
Defined bone defects (diameter 5 mm) were placed in aged, osteopenic female sheep.
Defects were treated with fiber-reinforced CPC alone (L4; CPC+ fibers) or with CPC containing different dosages of GDF5 (L5; CPC+ fibers + GDF5; 1, 5, 100, and 500g GDF5; n =
5 or 6 each).
The results were compared with those of untouched controls (L1). Three and 9 months postoperation, structural and functional effects of the CPC (±GDF5) were assessed ex vivo by measuring
(1) bone mineral density (BMD);
(2) bone structure, that is, bone volume/total volume (assessed by micro-computed tomography and histomorphometry), trabecular thickness, and trabecular number;
(3) bone formation, that is, osteoid volume/bone volume, osteoid surface/bone surface, osteoid thickness, mineralized surface/bone surface, mineral apposition rate, and bone formation rate/bone surface;
(4) bone resorption, that is, eroded surface/bone surface; and
(5) compressive strength.
RESULTS:
Compared with untouched controls (L1), both CPC+ fibers (L4) and CPC+ fibers + GDF5 (L5) numerically or significantly improved all parameters of bone formation, bone resorption, and bone structure. These significant effects were observed both at 3 and 9 months, but for some parameters they were less pronounced at 9 months. Compared with CPC without GDF5, additional significant effects of CPC with GDF5 were demonstrated for BMD and parameters of bone formation and structure (bone volume/total volume, trabecular thickness, and trabecular number, as well as mineralized surface/bone surface). The GDF5 effects were dose-dependent (predominantly in the 5–100g range) at 3 and 9 months.
CONCLUSIONS:
GDF5 significantly enhanced the bone formation induced by a PLGA fiber-reinforced CPC in sheep lumbar osteopenia. The results indicated that a local dose as low as ≤100g
GDF5 may be sufficient to augment middle to long-term bone formation. The novel CPC+ GDF5 combination may thus qualify as an alternative to the bioinert, supraphysiologically stiff poly-(methyl methacrylate) cement currently applied for vertebroplasty/kyphoplasty of osteoporotic vertebral fractures.