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Biomechanical Strength (biomechanical + strength)
Selected AbstractsBiomechanical Strength of Human Nasal Septal Lining: Comparison of the Constituent LayersTHE LARYNGOSCOPE, Issue 8 2005David W. Kim MD Abstract Objective/Hypothesis: Nasal septal perforation is a common complication following surgery involving the nasal septum. Septoplasty, septorhinoplasty, and submucosal resection may result in the inadvertent resection of perichondrium, which may predispose the patient to septal perforations. Study Design: Controlled human cadaver study testing the biomechanical strength of the constituent layers of nasal septal lining. Methods: Uniform samples of nasal septal mucosa, perichondrium, and a composite of both layers were obtained from five fresh human cadavers. The mechanical tensile strength of these layers was evaluated and compared with the Instron 4301 Mechanical Testing System (Canton, MA). Results: Mixed-effects regression analysis demonstrated a significant difference in the tensile strength of the three groups (mean values ± SD: mucosa, 662 ± 308 g; perichondrium, 1370 ± 798 g; composite, 2340 ± 1252 g). All three pairwise comparisons among the three groups showed a significant difference in tensile strength. Conclusion: The perichondrial layer imparts the majority of the biomechanical strength to septal lining. Lining flaps containing both perichondrium and mucosa are stronger than flaps with either perichondrium or mucosa alone. Dissection in the subperichondrial plane during septal surgery provides a stronger septal flap and may prevent the development of nasal septal perforation during nasal surgery. [source] Healing process induced by three composite prostheses in the repair of abdominal wall defectsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2002Juan M. Bellón Abstract The present study compared the performance of three composite prostheses used to repair abdominal wall defects in rabbits. Two of them [Parietex Composite® (PC) and Composix® (CS)] are commonly used in clinical practice and one was designed by the present team (PL-PU99). At 14 and 90 days postimplant, specimens were obtained for morphological, macrophage response (RAM-11) and morphometric and biomechanical analysis. The prosthetic area covered by adhesions was significantly greater (p < 0.05) in the CS group (6.83 ± 2.31 cm2) than in PC (0.11 ± 0.02 cm2) or PL-PU99 (0.10 ± 0.07 cm2). At 14 days, it was observed a homogeneous, organized, well-vascularized neoperitoneum that was significantly thicker (p < 0.05) in PL-PU99. Except in the CS implants, this layer was covered by a continuous mesothelium. All three composites achieved good recipient tissue integration. Highest macrophage levels were recorded at 14 days with significantly higher values in the PL-PU99 prosthesis. Biomechanical strength was significantly greater (p < 0.05) in CS at two weeks postimplant, but it was similar at 90 days. These findings suggest that the three composites show ideal integration with host tissue, along with similar biomechanical strength at 90 days, and significantly higher adhesion formation is induced by the CS prosthesis, possibly due to incomplete mesothelialization of the lower prosthetic surface. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 182,190, 2002; DOI 10.002/jbm.10123 [source] Long-Term Protective Effects of Zoledronic Acid on Cancellous and Cortical Bone in the Ovariectomized Rat,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2008Jürg A Gasser PhD Abstract Current bisphosphonate therapies effectively prevent bone loss in postmenopausal women. We studied the effect of a single intravenous dose of ZOL in ovariectomized rats. Protection from bone loss was dose dependent, lasting for up to 32 weeks, supporting the rationale for an annual intravenous dosing regimen of ZOL for treatment of postmenopausal osteoporosis. Introduction: Once-yearly dosing with zoledronic acid (ZOL) 5 mg can increase BMD and reduce fracture rate in postmenopausal women with low BMD. The primary objective of this study was to determine the duration of bone protective effects of a single dose of ZOL in ovariectomized rats, an animal model of postmenopausal osteopenia. Secondary objectives were to determine the effects on bone turnover and mechanical properties. Materials and Methods: Female Wistar rats (10 per group) received single intravenous doses of ZOL 0.8, 4, 20, 100, or 500 ,g/kg, alendronate 200 ,g/kg, or isotonic saline 4 days before bilateral ovariectomy. Sham-operated controls were pretreated with saline. Mass and density of cancellous and cortical bone (pQCT) were measured at 4-wk intervals for 32 wk. Bone architecture (,CT), bone formation dynamics (fluorochrome label-based histomorphometry), and biomechanical strength in compression testing were also assessed at 32 wk. Results: Ovariectomy-associated BMD loss was significantly attenuated for 32 wk by ZOL ,4 ,g/kg for total BMD, ZOL ,20 ,g/kg for cortical BMD, and ZOL ,4 ,g/kg for cancellous BMD (p < 0.01 versus ovariectomized controls). Alendronate 200 ,g/kg was of equivalent potency to ZOL 20 ,g/kg. Ovariectomy-associated decreases in trabecular architectural parameters were dose-dependently attenuated by ZOL. Alendronate 200 ,g/kg was equivalent to ZOL 20 ,g/kg. The bone resorption marker TRACP5b indicated transient suppression of elevated osteoclast activity by ZOL relative to OVX-rats even at the lowest dose of 0.8 ,g/kg, whereas at 100,500 ,g/kg, the effect was significant relative to the OVX control for the entire duration of the study of 32 wk. Bone formation parameters were not significantly affected by ZOL 20 ,g/kg but were significantly reduced by ZOL 100,500 ,g/kg. Alendronate 200 ,g/kg was equivalent to ZOL 100 ,g/kg. ZOL produced dose-related improvements in bone strength parameters after ovariectomy. Alendronate 200 ,g/kg was of similar potency to ZOL 20 ,g/kg. Conclusions: The duration and magnitude of the bone-protecting effect of a single intravenous dose of ZOL in ovariectomized rats is dose dependent and lasts for up to 32 wk. Compared with alendronate, ZOL shows 10-fold higher potency in preventing bone loss. These data support the use of an annual intravenous ZOL dosing regimen for the treatment of osteoporosis. [source] Whole-Genome Scan for Linkage to Bone Strength and Structure in Inbred Fischer 344 and Lewis Rats,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2005Imranul Alam Abstract A genome-wide genetic linkage analysis identified several chromosomal regions influencing bone strength and structure in F2 progeny of Fischer 344 x Lewis inbred rats. Introduction: Inbred Fischer 344 (F344) and Lewis (LEW) rats are similar in body size, but the F344 rats have significantly lower BMD and biomechanical strength of the femur and spine compared with LEW rats. The goal of this study was to identify quantitative trait loci (QTL) linked to bone strength and structure in adult female F2 rats from F344 and LEW progenitors. Materials and Methods: The 595 F2 progeny from F344 x LEW rats were phenotyped for measures of bone strength (ultimate force {Fu}; energy to break {U}; stiffness {S}) of the femur and lumbar vertebra and structure (femur midshaft polar moment of inertia {Ip}; femur midshaft cortical area; vertebral area). A genome-wide scan was completed in the F2 rats using 118 microsatellite markers at an average interval of 20 cM. Multipoint quantitative linkage analysis was performed to identify chromosomal regions that harbor QTL for bone strength and structure phenotypes. Results: Evidence of linkage for femur and lumbar strength was observed on chromosomes (Chrs) 1, 2, 5, 10, and 19. Significant linkage for femoral structure was detected on Chrs 2, 4, 5, 7, and 15. QTLs affecting femoral strength on Chrs 2 and 5 were also found to influence femur structure. Unique QTLs on Chrs 1, 10, and 19 were found that contributed to variability in bone strength but had no significant effect on structure. Also, unique QTLs were observed on Chrs 4, 7, and 15 that affected only bone structure without any effect on biomechanics. Conclusion: We showed multiple genetic loci influencing bone strength and structure in F344 x LEW F2 rats. Some of these loci are homologous to mouse and human chromosomes previously linked to related bone phenotypes. [source] Biomechanical Strength of Human Nasal Septal Lining: Comparison of the Constituent LayersTHE LARYNGOSCOPE, Issue 8 2005David W. Kim MD Abstract Objective/Hypothesis: Nasal septal perforation is a common complication following surgery involving the nasal septum. Septoplasty, septorhinoplasty, and submucosal resection may result in the inadvertent resection of perichondrium, which may predispose the patient to septal perforations. Study Design: Controlled human cadaver study testing the biomechanical strength of the constituent layers of nasal septal lining. Methods: Uniform samples of nasal septal mucosa, perichondrium, and a composite of both layers were obtained from five fresh human cadavers. The mechanical tensile strength of these layers was evaluated and compared with the Instron 4301 Mechanical Testing System (Canton, MA). Results: Mixed-effects regression analysis demonstrated a significant difference in the tensile strength of the three groups (mean values ± SD: mucosa, 662 ± 308 g; perichondrium, 1370 ± 798 g; composite, 2340 ± 1252 g). All three pairwise comparisons among the three groups showed a significant difference in tensile strength. Conclusion: The perichondrial layer imparts the majority of the biomechanical strength to septal lining. Lining flaps containing both perichondrium and mucosa are stronger than flaps with either perichondrium or mucosa alone. Dissection in the subperichondrial plane during septal surgery provides a stronger septal flap and may prevent the development of nasal septal perforation during nasal surgery. [source] A role for ,/, T cells in a mouse model of fracture healingARTHRITIS & RHEUMATISM, Issue 6 2009Nona T. Colburn Objective Fractures can initiate an immune response that disturbs osteoblastic and osteoclastic cellular homeostasis through cytokine production and release. The aim of our study was to investigate ,/, T cells, innate lymphocytes known to be involved in tissue repair, as potential cellular components of the osteoimmune system's response to an in vivo model of bone injury. The absence of such cells or their effector cytokines influences the fate of other responder cells in proliferation, differentiation, matrix production, and ultimate callus formation. Methods Tibia fractures were created in 60 ,/, T cell,deficient mice (also called , T cell receptor [TCR],knockout mice) and 60 control C57BL/6 mice. Analysis included radiographs, basic histology, mechanical testing, flow cytometry, and immunohistochemical localization of ,/, TCR,positive subsets from control animals and of CD44 expression from both groups, as well as enzyme-linked immunosorbent assay for the effector cytokines interleukin-2 (IL-2), interferon-, (IFN,), and IL-6. Results Animals deficient in ,/, T cells demonstrated more mature histologic elements and quantitative increases in the expression of major bone (bone sialoprotein) and cartilage (type II collagen) matrix proteins and in the expression of bone morphogenetic protein 2 at a critical reparative phase. Moreover, only ,/, T cell,deficient animals had a decrease in the osteoprogenitor antiproliferative cytokines IL-6 and IFN, at the reparative phase. The result was improved stability at the repair site and an overall superior biomechanical strength in ,/, T cell,deficient mice compared with controls. Conclusion The evidence for a role of ,/, T cells in the context of skeletal injury demonstrates the importance of the immune system's effect on bone biology, which is relevant to the field of osteoimmunology, and offers a potential molecular platform from which to develop essential therapeutic strategies. [source] Long-term biomechanical properties of rabbit sclera after collagen crosslinking using riboflavin and ultraviolet A (UVA)ACTA OPHTHALMOLOGICA, Issue 2 2009Gregor Wollensak Abstract. Purpose:, Scleral crosslinking by the photosensitizer riboflavin and ultraviolet A (UVA) has been shown to increase significantly the scleral biomechanical rigidity and might therefore become a possible sclera-based treatment modality for progressive myopia. In the present study, the long-term effect of the new crosslinking method on biomechanical properties was investigated in the rabbit sclera. Methods:, A 10 × 10 mm sector of the equatorial sclera of nine Chinchilla rabbit eyes was treated in vivo using a UVA double diode of 370 nm with a surface irradiance of 3 mW/cm2 and application of 0.1% riboflavin-5-phosphate drops as photosensitizer for 30 min. Three days, 4 months and 8 months postoperatively, biomechanical stress,strain measurements of the treated scleral strips were performed and compared to contralateral control sclera using a microcomputer-controlled biomaterial tester. In addition, routine histological controls were performed. Results:, Following the crosslinking treatment, Young's modulus was increased by 320% after 3 days, 277% after 4 months and 502% after 8 months, and ultimate stress by 341% after 3 days, 131% after 4 months and 213.8% after 8 months versus the controls. The decrease in ultimate strain was between 24% and 44.8%. On histology, no tissue damage was detected. Conclusion:, Our new method of scleral collagen crosslinking proved very effective and constant over a time interval of up to 8 months in increasing the scleral biomechanical strength. Therefore, the new treatment might become an option for strengthening scleral tissue in progressive myopia and other conditions associated with weakened sclera. There were no side-effects on the retina or retinal pigment epithelium. The new crosslinking treatment could now be tested in a suitable myopia model (like the tree shrew) and finally in human eyes. [source] Long-term biomechanical properties after collagen crosslinking of sclera using glyceraldehydeACTA OPHTHALMOLOGICA, Issue 8 2008Gregor Wollensak Abstract. Purpose:, Chemical crosslinking by glyceraldehyde has been shown to increase significantly the biomechanical rigidity of sclera. It might therefore become an option for a sclera-based treatment of progressive myopia. The present pilot study was designed to test the long-term biomechanical efficiency of the new crosslinking method. Methods:, Six Chinchilla rabbits were treated with sequential sub-Tenon's injections of 0.15 ml 0.5 m glyceraldehyde, which were given in the supero-nasal quadrant of the right eye (OD) five times over 14 days. The rabbits were killed 4 months and 8 months after crosslinking treatment, respectively. Biomechanical stress,strain measurements of scleral strips from the treatment area were performed and compared to non-treated contralateral control sclera using a microcomputer-controlled biomaterial testing device. In addition, the eyes were examined histologically by light microscopy to evaluate possible side-effects. Results:, Following the crosslinking treatment, the ultimate stress was 10.2 ± 2.3 MPa after 4 months and 8.5 ± 2.2 MPa after 8 months versus 2.4 ± 0.3 MPa in the controls (increases of 325% and 254.17%, respectively); Young's modulus was 104.6 ± 13.7 MPa after 4 months and 53.2 ± 5.2 MPa after 8 months versus 9.6 ± 1.3 MPa in the controls (increases of 989.6% and 554.17%, respectively); and ultimate strain was 15.8 ± 1.5% after 4 months and 24.1 ± 0.7% after 8 months versus 38.4 ± 4.6% in the controls (decreases of 58.84% and 37.24%, respectively). Histologically, no side-effects were found. Conclusion:, Our new method of scleral collagen crosslinking proved very efficient in increasing scleral biomechanical strength over a period of up to 8 months. Glyceraldehyde can be applied easily by sequential parabulbar injections. Before clinical application in myopic patients, a study in an animal myopia model is recommended. [source] | ||||||||||