Biomechanical Testing (biomechanical + testing)

Distribution by Scientific Domains


Selected Abstracts


Enhancing the mechanical integrity of the implant,bone interface with BoneWelding® technology: Determination of quasi-static interfacial strength and fatigue resistance

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006
Stephen J. Ferguson
Abstract The BoneWelding® technology is an innovative bonding method, which offers new alternatives in the treatment of fractures and other degenerative disorders of the musculoskeletal system. The BoneWelding process employs ultrasonic energy to liquefy a polymeric interface between orthopaedic implants and the host bone. Polymer penetrates the pores of the surrounding bone and, following a rapid solidification, forms a strong and uniform bond between implant and bone. Biomechanical testing was performed to determine the quasi-static push-out strength and fatigue performance of 3.5-mm-diameter polymeric dowels bonded to a bone surrogate material (Sawbones solid and cellular polyurethane foam) using the BoneWelding process. Fatigue tests were conducted over 100,000 cycles of 20,100 N loading. Mechanical test results were compared with those obtained with a comparably-sized, commercial metallic fracture fixation screw. Tests in surrogate bone material of varying density demonstrated significantly superior mechanical performance of the bonded dowels in comparison to conventional bone screws (p < 0.01), with holding strengths approaching 700 N. Even in extremely porous host material, the performance of the bonded dowels was equivalent to that of the bone screws. For both cellular and solid bone analog materials, failure always occurred within the bone analog material surrounding and distant to the implant; the infiltrated interface was stronger than the surrounding bone analog material. No significant decrease in interfacial strength was observed following conditioning in a physiological saline solution for a period of 1 month prior to testing. Ultrasonically inserted implants migrated, on average, less than 20 ,m over, and interfacial stiffness remained constant the full duration of fatigue testing. With further refinement, the BoneWelding technology may offer a quicker, simpler, and more effective method for achieving strong fixation and primary stability for fracture fixation or other orthopaedic and dental implant applications. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source]


RANKL Inhibition with Osteoprotegerin Increases Bone Strength by Improving Cortical and Trabecular bone Architecture in Ovariectomized Rats,,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2008
Michael S Ominsky
Abstract Introduction: Ovariectomy (OVX) results in bone loss caused by increased bone resorption. RANKL is an essential mediator of bone resorption. We examined whether the RANKL inhibitor osteoprotegerin (OPG) would preserve bone volume, density, and strength in OVX rats. Materials and Methods: Rats were OVX or sham-operated at 3 mo of age. Sham controls were treated for 6 wk with vehicle (Veh, PBS). OVX rats were treated with Veh or human OPG-Fc (10 mg/kg, 2/wk). Serum RANKL and TRACP5b was measured by ELISA. BMD of lumbar vertebrae (L1,L5) and distal femur was measured by DXA. Right distal femurs were processed for bone histomorphometry. Left femurs and the fifth lumbar vertebra (L5) were analyzed by ,CT and biomechanical testing, and L6 was analyzed for ash weight. Results: OVX was associated with significantly greater serum RANKL and osteoclast surface and with reduced areal and volumetric BMD. OPG markedly reduced osteoclast surface and serum TRACP5b while completely preventing OVX-associated bone loss in the lumbar vertebrae, distal femur, and femur neck. Vertebrae from OPG-treated rats had increased dry and ash weight, with no significant differences in tissue mineralization versus OVX controls. ,CT showed that trabecular compartments in OVX-OPG rats had significantly greater bone volume fraction, vBMD, bone area, trabecular thickness, and number, whereas their cortical compartments had significantly greater bone area (p < 0.05 versus OVX-Veh). OPG improved cortical area in L5 and the femur neck to levels that were significantly greater than OVX or sham controls (p < 0.05). Biomechanical testing of L5 and femur necks showed significantly greater maximum load values in the OVX-OPG group (p < 0.05 versus OVX-Veh). Bone strength at both sites was linearly correlated with total bone area (r2 = 0.54,0.74, p < 0.0001), which was also significantly increased by OPG (p < 0.05 versus OVX). Conclusions: OPG treatment prevented bone loss, preserved trabecular architecture, and increased cortical area and bone strength in OVX rats. [source]


Hip Fractures and the Contribution of Cortical Versus Trabecular Bone to Femoral Neck Strength,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2009
Gerold Holzer
Abstract Osteoporotic fractures are caused by both cortical thinning and trabecular bone loss. Both are seen to be important for bone fragility. The relative contributions of cortical versus trabecular bone have not been established. The aim of this study was to test the contribution of cortical versus trabecular bone to femoral neck stability in bone strength. In one femur from each pair of 18 human cadaver femurs (5 female; 4 male), trabecular bone was completely removed from the femoral neck, providing one bone with intact and the other without any trabecular structure in the femoral neck. Geometrical, X-ray, and DXA measurements were carried out before biomechanical testing (forces to fracture). Femoral necks were osteotomized, slices were analyzed for cross-sectional area (CSA) and cross-sectional moment of inertia (CSMI), and results were compared with biomechanical testing data. Differences between forces needed to fracture excavated and intact femurs (,F/F mean) was 7.0% on the average (range, 4.6,17.3%). CSA of removed spongiosa did not correlate with difference of fracture load (,F/F mean), nor did BMD. The relative contribution of trabecular versus cortical bone in respect to bone strength in the femoral neck seems to be marginal and seems to explain the subordinate role of trabecular bone and its changes in fracture risk and the effects of treatment options in preventing fractures. [source]


RANKL Inhibition with Osteoprotegerin Increases Bone Strength by Improving Cortical and Trabecular bone Architecture in Ovariectomized Rats,,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2008
Michael S Ominsky
Abstract Introduction: Ovariectomy (OVX) results in bone loss caused by increased bone resorption. RANKL is an essential mediator of bone resorption. We examined whether the RANKL inhibitor osteoprotegerin (OPG) would preserve bone volume, density, and strength in OVX rats. Materials and Methods: Rats were OVX or sham-operated at 3 mo of age. Sham controls were treated for 6 wk with vehicle (Veh, PBS). OVX rats were treated with Veh or human OPG-Fc (10 mg/kg, 2/wk). Serum RANKL and TRACP5b was measured by ELISA. BMD of lumbar vertebrae (L1,L5) and distal femur was measured by DXA. Right distal femurs were processed for bone histomorphometry. Left femurs and the fifth lumbar vertebra (L5) were analyzed by ,CT and biomechanical testing, and L6 was analyzed for ash weight. Results: OVX was associated with significantly greater serum RANKL and osteoclast surface and with reduced areal and volumetric BMD. OPG markedly reduced osteoclast surface and serum TRACP5b while completely preventing OVX-associated bone loss in the lumbar vertebrae, distal femur, and femur neck. Vertebrae from OPG-treated rats had increased dry and ash weight, with no significant differences in tissue mineralization versus OVX controls. ,CT showed that trabecular compartments in OVX-OPG rats had significantly greater bone volume fraction, vBMD, bone area, trabecular thickness, and number, whereas their cortical compartments had significantly greater bone area (p < 0.05 versus OVX-Veh). OPG improved cortical area in L5 and the femur neck to levels that were significantly greater than OVX or sham controls (p < 0.05). Biomechanical testing of L5 and femur necks showed significantly greater maximum load values in the OVX-OPG group (p < 0.05 versus OVX-Veh). Bone strength at both sites was linearly correlated with total bone area (r2 = 0.54,0.74, p < 0.0001), which was also significantly increased by OPG (p < 0.05 versus OVX). Conclusions: OPG treatment prevented bone loss, preserved trabecular architecture, and increased cortical area and bone strength in OVX rats. [source]


Paricalcitol [19-Nor-1,25-(OH)2D2] in the Treatment of Experimental Renal Bone Disease,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2006
Jarkko Jokihaara
Abstract Paricalcitol is a less hypercalcemic vitamin D analog that has been shown to suppress secondary hyperparathyroidism and to prevent the associated histomorphometric changes in bone. In this study, we show that paricalcitol also ameliorates the renal insufficiency-induced loss of bone mineral and the mechanical competence of bone. Introduction: Renal bone disease is a common consequence of chronic renal insufficiency and the associated secondary hyperparathyroidism (SH). Paricalcitol [19-nor-1,25(OH)2D2] has been shown to ameliorate SH and prevent renal failure,induced histomorphometric changes in bone with minimal calcemic and phosphatemic activity. However, information about its efficacy on restoration of bone structural strength is lacking. In this study, we explored the effects of paricalcitol treatment on bone structure and strength in a model of advanced renal disease. Materials and Methods: Forty-five 8-week-old rats were randomly assigned to either surgical 5/6 nephrectomy (NTX) or Sham-operation. After a 15-week postoperative disease progression period, the NTX rats were further allocated to uremic control (NTX) and treatment (NTX + paricalcitol) groups, the latter of which received paricalcitol for the subsequent 12 weeks. After 27 weeks, the animals were killed, plasma samples were collected, and both femora were excised for comprehensive analysis of the femoral neck and midshaft (pQCT and biomechanical testing). Results: High mortality that exceeded 30% was observed in both NTX groups. NTX induced over a 13-fold increase in plasma PTH, whereas this increase was only 5-fold after paricalcitol treatment. At the femoral neck, NTX was associated with an 8.1% decrease (p < 0.05) in vBMD and a 16% decrease in breaking load (p < 0.05) compared with the Sham group, whereas paricalcitol treatment completely prevented these changes. At the femoral midshaft, the NTX resulted in a 6.6% decrease in cortical BMD (p < 0.01 versus Sham), and this change was also prevented by paricalcitol. Conclusions: Paricalcitol administration prevented renal insufficiency-associated decreases in BMD in the femoral neck and the femoral midshaft and restored bone strength in the femoral neck. Therefore, paricalcitol can efficiently ameliorate renal insufficiency-induced loss of bone mineral and mechanical competence of bone. [source]


BMP-7,induced ectopic bone formation and fracture healing is impaired by systemic NSAID application in C57BL/6-mice,

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2010
Alexander S. Spiro
Abstract Nonsteroidal antiinflammatory drugs (NSAIDs) are known to potentially impair the fracture healing process. The aim of the present study was to determine if the impairment of bone healing by systemic NSAID application is, at least in part, due to an interaction of NSAIDs with the bone anabolic BMP-7 pathway. Therefore, we first analyzed fracture healing in control and diclofenac-treated mice, where we not only found a significant impairment of fracture healing due to diclofenac treatment as assessed by biomechanical testing and µCT imaging, but also found high coexpression of bone morphogenetic protein-7 (BMP-7) and cyclooxygenase-2 (COX-2) within the fracture callus of both groups. To experimentally address the possible interaction between BMP-7 and COX-2, we then induced ectopic bone formation in control (n,=,10) and diclofenac-treated mice (n,=,10) by application of BMP-7 (recombinant human OP-1, rhOP-1) into the hamstring muscles. After 20 days of treatment, each ectopic bone nodule was analyzed by contact-radiography, µCT, histology, and histomorphometry. Diclofenac application decreased the trabecular number and bone mass in the ectopic bone nodules significantly due to reduced osteoblast number and activity. These data demonstrate that the bone anabolic effect of BMP-7 and fracture healing is impaired by diclofenac application, and suggest that the potential negative impact of NSAIDs on fracture healing is, at least in part, due to interference with BMP-7 signaling. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:785,791, 2010 [source]


Novel Polysaccharide-derived hydrogel prevents perineural adhesions in a rat model of sciatic nerve adhesion

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2010
Michiro Yamamoto
Abstract We investigated the effects of a novel carboxymethylcellulose (CMC)-derived hydrogel, in which phosphatidylethanolamine (PE) was introduced into the carboxyl groups of CMC, for preventing perineural adhesion after extensive internal neurolysis of rat sciatic nerve. Sciatic nerves were randomly assigned to one of the following groups: the Control group, operated but no treatment; the HA group, operated and treated with 1% hyaluronan; the CMC,PE(L) group, operated and treated with low-viscosity CMC,PE hydrogel; and the CMC,PE(H) group, operated and treated with high-viscosity CMC,PE hydrogel. Perineural adhesions were evaluated at 6 weeks. Nerves were also subjected to biomechanical testing to assess ultimate breaking strength. Electrophysiological and wet muscle weight measurements were performed. Breaking strengths were significantly lower for the CMC,PE(L) group than for the Control and HA groups. Latency was significantly longer for the Control group than for the CMC,PE(L) group at 20 days. The mean percentage of wet muscle weight to body weight was significantly lower for the Control group than for the CMC,PE(L) group at 6 weeks. Low-viscosity CMC,PE hydrogel appears to prevent perineural adhesions and allow early restoration of nerve function. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:284,288, 2010 [source]


Enhancement of posterolateral lumbar spine fusion using low-dose rhBMP-2 and cultured marrow stromal cells

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2009
Tsai-Sheng Fu
Abstract We tested the hypothesis that the dose of recombinant human bone morphogenetic protein-2 (rhBMP-2) required to induce spine fusion can be reduced by combination with mesenchymal stem cells (MSCs). Twenty-four adult rabbits underwent posterolateral intertransverse fusion at the L4,L5 level. The animals were divided into four groups based on the implant material: autologous iliac graft, Alginate-MSCs composite, Alginate-BMP-2-MSCs composite, and Alginate-BMP-2 composite. After 16 weeks, the rabbits were euthanized for radiographic examination, manual palpation, biomechanical testing, and histology. Radiographic union of 12 intertransverse fusion areas for the autogenous iliac graft, Alginate-MSCs, Alginate-BMP-2-MSCs, and Alginate-BMP-2 groups was 11, 8, 11, and 0, respectively. Moreover, manual palpation of six fusion segments in each subgroup found solid union to be 6, 1, 5, and 0, respectively. The average torques at failure of the first three groups were 2278,±,135, 1943,±,140, and 2334,±,187 N-mm, respectively. The failure torque did not differ significantly between the autograft and Alginate-BMP-2-MSCs groups; both groups were significantly higher than the Alginate-MSCs group. The results indicate that MSCs delivered with in vitro cellular doses of rhBMP-2 are more osteoinductive than MSCs without rhBMP-2. In combination with MSCs, a low dose (2.5 µg) of rh-BMP-2 could enhance bone formation and posterolateral spine fusion success in the rabbit model. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:380,384, 2009 [source]


Reduced cortical bone mass in mice with inactivation of interleukin-4 and interleukin-13

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2007
Carl-Johan Silfverswärd
Abstract The aim of the present study was to study the in vivo role of IL-4 and IL-13 on bone metabolism. The skeletal phenotypes of male and female IL-13,/, (n,=,7+7), IL-4,/,IL-13,/, (n,=,7+7), and WT (n,=,7+7) mice were compared. Analysis was made at 6 weeks of age (juvenile) by pQCT, and at 20 weeks of age (adult) by pQCT, biomechanical testing, and by S-IGF-1 and S-Osteocalcin measurements. The skeletal phenotype was affected only in adult male IL-4,/,IL-13,/, mice. These animals displayed a reduction in cortical bone mineral content (BMC) of both the tibia and the femur, as measured by mid-diaphyseal pQCT scans, compared with WT mice (tibia ,8.2%; femur ,8.5%; p,<,0.01). This reduction in cortical BMC was due to a decreased cross-sectional area as a result of a reduced cortical thickness. The mechanical strength of the cortical bone, tested by three-point-bending at the mid-diaphyseal region of the femurs, demonstrated a significant reduction of displacement at failure (,11.4%), maximal load at failure (,10.6%), and total energy until failure (,29.4%). S-IGF-1 and S-Osteocalcin levels as well as trabecular bone mineral density (tvBMD) were unaffected in adult male IL-4,/,IL-13,/, mice. IL-4,/,IL-13,/, male mice show adult onset reduction of cortical bone mass and strength, indicating that the two anti-inflammatory Th2 cytokines IL-4 and IL-13 are involved in the regulation of bone remodeling. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25: 725,731, 2007 [source]


Use of a collagen-platelet rich plasma scaffold to stimulate healing of a central defect in the canine ACL

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2006
Martha M. Murray
Abstract The anterior cruciate ligament (ACL) of the knee fails to heal after primary repair. Here we hypothesize that a beneficial biologic repair response can be induced by placing a collagen-platelet rich plasma (collagen-PRP) material into a central ACL defect. A collagen-PRP scaffold was used to treat a central ACL defect in vivo. In the first experiment, the histologic response in treated and untreated defects was evaluated at 3 (n,=,5) and 6 weeks (n,=,5). In the second experiment, biomechanical testing of the treated ligaments (n,=,8) was performed at 6 weeks and compared with the results of biomechanical testing of untreated defects at the same time-point (n,=,6). The percentage filling of the defects in the treated ACLs was significantly higher at both the 3- and 6-week time-points when compared with the untreated contralateral control defects (50,±,21% vs. 2,±,2% at 3 weeks, and 43,±,11% vs. 23,±,11 at 6 weeks; all values mean,±,SEM. Biomechanically, the treated ACL defects had a 40% increase in strength at 6 weeks, which was significantly higher than the 14% increase in strength previously reported for untreated defects (p,<,0.02). Placement of a collagen-PRP bridging scaffold in a central ACL defect can stimulate healing of the ACL histologically and biomechanically. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:820,830, 2006 [source]


Melatonin effect on bone metabolism in rats treated with methylprednisolone

JOURNAL OF PINEAL RESEARCH, Issue 4 2006
Marta G. Ladizesky
Abstract:, The present study was undertaken to examine the effect of melatonin (25 ,g/mL of drinking water, about 500 ,g/day) on a 10-wk long treatment of male rats with methylprednisolone (5 mg/kg s.c., 5 days/wk). Bone densitometry and mechanical properties, calcemia, phosphatemia and serum bone alkaline phosphatase activity and C-telopeptide fragments of collagen type I (CTX) were measured. Both melatonin and methylprednisolone decreased significantly body weight (BW) and the combination of both treatments resulted in the lowest BW values found. Consequently, all results were analyzed with BW as a covariate. Densitometrically, methylprednisolone augmented bone mineral content (BMC), bone area (BA) and bone mineral density (BMD) in the entire skeleton, BMC in cortical bone, and BMC and BMD in trabecular bone. Melatonin increased BMC and BA in whole skeleton and BMC and BMD in trabecular bone. For BMC and BA of whole skeleton, BMC of cortical bone, and BMC and BMD of trabecular bone, the combination of glucocorticoids and melatonin resulted in the highest values observed. Femoral weight of rats receiving methylprednisolone or melatonin increased significantly and both treatments summated to achieve the greatest effect. In femoral biomechanical testing, methylprednisolone augmented ultimate load and work to failure significantly. Rats receiving the combined treatment of methylprednisolone and melatonin showed the highest values of work to failure. The circulating levels of CTX, an index of bone resorption, decreased after methylprednisolone or melatonin, both treatments summating to achieve the lowest CTX values found. Serum calcium increased after methylprednisolone and serum phosphorus decreased after treatment with methylprednisolone or melatonin while serum bone alkaline phosphatase levels remained unchanged. The results are compatible with the view that low doses of methylprednisolone or melatonin decrease bone resorption and have a bone-protecting effect. [source]


Methodology for biomechanical testing of fresh anterior wall vaginal samples from postmenopausal women undergoing cystocele repair,

NEUROUROLOGY AND URODYNAMICS, Issue 4 2009
Philippe E. Zimmern
Abstract Goal To explore the methodological challenges of biomechanical testing of freshly harvested human anterior vaginal wall (HAVW) samples. Method Longitudinal full-thickness samples of HAVW were excised during cystocele repair in postmenopausal women and age-matched controls. Two methods of tissue storage during transport were compared. All samples were prepared for uniaxial testing within 2 hr of harvest and loaded at a rate of 0.5 mm/sec, until irreversible deformation was observed. Young's modulus and other parameters were extracted from the tensile stress,strain curves. Results Samples were obtained over 2 years from 42 patients. Significant differences in biomechanical parameters were noted based on the degree of hydration of the tissue, suggesting that the wetter samples were mechanically weaker. Conclusions This study reports on a new method for testing the biomechanical properties of freshly harvested HAVW tissues and the impact of tissue hydration during transport between the operating room and the testing lab. Neurourol. Urodynam. 28:325,329, 2009. © 2009 Wiley-Liss, Inc. [source]


Validity and clinical significance of biomechanical testing of implant/bone interface

CLINICAL ORAL IMPLANTS RESEARCH, Issue S2 2006
Carlos Aparicio
Abstract Purpose: The aim of this paper was to review the clinical literature on the Resonance frequency analysis (RFA) and Periotest techniques in order to assess the validity and prognostic value of each technique to detect implants at risk for failure. Material and methods: A search was made using the PubMed database to find clinical studies using the RFA and/or Periotest techniques. Results: A limited number of clinical reports were found. No randomized-controlled clinical trials or prospective cohort studies could be found for validity testing of the techniques. Consequently, only a narrative review was prepared to cover general aspects of the techniques, factors influencing measurements and the clinical relevance of the techniques. Conclusions: Factors such as bone density, upper or lower jaw, abutment length and supracrestal implant length seem to influence both RFA and Periotest measurements. Data suggest that high RFA and low Periotest values indicate successfully integrated implants and that low/decreasing RFA and high/increasing Periotest values may be signs of ongoing disintegration and/or marginal bone loss. However, single readings using any of the techniques are of limited clinical value. The prognostic value of the RFA and Periotest techniques in predicting loss of implant stability has yet to be established in prospective clinical studies. [source]