bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue behavior of the equine third metacarpus: Mechanical property analysis
Authors: Gibson V. A. , Stover S. M. , Martin R. B. , Gibeling J. C. , Willits N. H. , Gustafson M. B. , Griffin L. V. 
Published: February 2005

AbstractThis is the first in a series of experiments to study the fatigue properties of equine cannon (third metacarpal) bone specimens from Throughbred racehorses. Monotonic and fatigue tests to failure were performed in four‐point bending on diaphyseal specimens in a 37°C saline bath to answer three initial questions. (a) Will a linear variable differential transducer yield the same elastic modulus as strain gauges? (b) Will fatigue results depend on whether the periosteal or endosteal side of the beam is in tension? (c) Are there regional variations in the monotonic and fatigue properties of the cannon bone midshaft? Eighteen left‐right pairs of specimens from six horses were used. One beam of each pair was fitted with strain gauges. Fatigue tests were conducted on 24 specimens under load control at 2 Hz; an initial range of 0‐10,000 microstrain was used so as to produce failure in a reasonable period of time. There were no left‐right differences in the fatigue or monotonic properties, and the presence of a gauge had no effect on modulus measured by a linear variable differential transducer. However, gauge‐measured moduli were about 1 GPa less than transducer‐measured values. Fatigue life was independent of which side of the beam was in tension, and there were significant variations in mechanical properties around the cortex. The lateral region was stiffer than the dorsal region but the latter had a longer fatigue life. The fixed cylindrical supports used in this experimental eventually produced slight wear grooves, causing artifactual stiffening at the end of the load cycle in some specimens. A second experiment using roller supports confirmed the reason for this stiffening. It also showed that fatigue life was shorter when roller supports were used but regional differences were similar.
Atrophic nonunion can be predicted with dual energy x‐ray absorptiometry in a canine ostectomy model
Authors: Markel Mark D. , Bogdanske John J. , Xiang Zhuzai , Klohnen Andreas 
Published: February 2005

AbstractThis study demonstrated that dual energy x‐ray absorptiometry can be used to distinguish between normal union and atrophic nonunion, with high sensitivity and high negative predictive value, by 8 weeks after surgery in a canine model. Eighteen adult mixed‐breed dogs were divided into two equal groups: normal union and atrophic nonunion. In the normal union group, a 5 mm mid‐diaphyseal transverse ostectomy was performed in the right tibia, and the bone was stabilized with a unilateral external fixator. In the atrophic nonunion group, a 5 mm mid‐diaphyseal ostectomy was performed; the distal 1.5 cm of the bone ends, including the periosteum, were frozen twice to −20°C using liquid nitrogen and thawed slowly twice; and the bone was stabilized with a unilateral external fixator. The members of the research team were blinded to the group assignments until after all dogs were killed and all data were acquired. Radiography and dual energy x‐ray absorptiometry of both tibiae were performed at week 1, 2, 3, 4, 6, 8, 10, 12, 14, and 16 after surgery. All dogs were killed at 16 weeks, and the torsional stiffness and maximum torque of both tibiae of five dogs in each group were determined. Mechanically, the tibiae in the normal union group had significantly higher maximum torque (43‐fold higher) and torsional stiffness (86‐fold higher) than the tibiae in the atrophic nonunion group. The sensitivity and negative predictive value of dual energy x‐ray absorptiometry for predicting nonunion were 100% by 8 weeks after surgery. The specificity and positive predictive value reached 78 and 82%, respectively, by 16 weeks. Radiographic scores were significantly higher for the union group than for the nonunion group beginning at 2 weeks after surgery. The earliest time after surgery that radiography classified an ostectomy as a nonunion was significantly later (4.6 ± 1.2 weeks) than for dual energy x‐ray absorptiometry (2.6 ± 1.4 weeks). Before these results can be extrapolated to human applications, further animal studies must be performed to evaluate clinically or experimentally induced fractures, or both, rather than the well defined ostectomies that were performed in this study.
Effect of stress deprivation and cyclic tensile loading on the material and morphologic properties of canine flexor digitorum profundus tendon: An in vitro study
Authors: Hannafin Jo A. , Arnoczky Steven P. , Hoonjan Amardeep , Torzilli Peter A. 
Published: February 2005

AbstractThe effect of stress deprivation and cyclic tensile loading on the mechanical and histologic properties of the canine flexor digitorum profundus tendon was examined using an in vitro system. Stress deprivation resulted in a progressive and statistically significant decrease in the tensile modulus over an 8‐week period. Histologically, stress‐deprived tendons demonstrated quantitative changes in the morphology and number of cells and in the alignment of collagen. The change in tensile properties was not associated with an alteration in the water content of the tissue, but the change appeared to be dependent on the presence of a viable cell population. Dead (acellular) tendons did not undergo any alteration in tensile modulus in this in vitro system. In vitro cyclic tensile loading of tendons over a 4‐week time period resulted in a significant increase in the tensile modulus (93% of the control) compared with that of the stress‐deprived tendons (68% of the control). This loading regimen also maintained the normal histologic pattern of the tendons. The results of this study are similar to those previously reported for in vivo studies and suggest that this in vitro model may represent a valid system with which to test the effects of various stress conditions on the tensile properties of tissues.
Combined knee loading states that generate high anterior cruciate ligament forces
Authors: Markolf Keith L. , Burchfield Daniel M. , Shapiro Matthew M. , Shepard Michael F. , Finerman Gerald A. M. , Slauterbeck James L. 
Published: February 2005

AbstractInjuries to the anterior cruciate ligament frequently occur under combined mechanisms of loading. This in vitro study was designed to measure levels of ligament force under dual combinations of individual loading states and to determine which combinations generated high force. Resultant force was recorded as the knee was extended passively from 90° of flexion to 5° of hyperextension under constant tibial loadings. The individual loading states were 100 N of anterior tibial force, 10 Nm of varus and valgus moment, and 10 Nm of internal and external tibial torque. Straight anterior tibial force was the most direct loading, mechanism; the mean ligament force was approximately equal to applied anterior tibial force near 30° of flexion and to 150% of applied tibial force at full extension. The addition of internal tibial torque to a knee loaded by anterior tibial force produced dramatic increases of force at full extension and hyperextension. This loading combination produced the highest ligament forces recorded in the study and is the most dangerous in terms of potential injury to the ligament. In direct contrast, the addition of external tibial torque to a knee loaded by anterior tibial force decreased the force dramatically for flexed positions of the knee; at close to 90° of flexion, the anterior cruciate ligament became completely unloaded. The addition of varus moment to a knee loaded by anterior tibial force increased the force in extension and hyperextension, whereas the addition of valgus moment increased the force at flexed positions. These states of combined loading also could present an increased risk for injury. Internal tibial torque is an important loading mechanism of the anterior cruciate ligament for an extended knee. The overall risk of injury to the ligament from varus or valgus moment applied in combination with internal tibial torque is similar to the risk from internal tibial torque alone. External tibial torque was a relatively unimportant mechanism for generating anterior cruciate ligament force.
Formation of osteoclast‐like cells is suppressed by low frequency, low intensity electric fields
Authors: Rubin Janet , McLeod Kenneth J. , Titus Louisa , Nanes Mark S. , Catherwood Bayard D. , Rubin Clinton T. 
Published: February 2005

AbstractWith use of a solenoid to generate uniform time‐varying electric fields, the effect of extremely low frequency electric fields on osteoclast‐like cell formation stimulated by 1,25(OH)2D3 was studied in primary murine marrow culture. Recruitment of osteoclast‐like cells was assessed by counting multinuclear, tartrateresistant acid phosphatase positive cells on day 8 of culture. A solenoid was used to impose uniform time‐varying electric fields on cells: sham exposures were performed with an identical solenoid with a null net electric field. During the experiments, both solenoids heated interiorly to approximately 1.5°C above ambient incubator temperature. As a result of the heating, cultures in the sham solenoid formed more osteoclast‐like cells than those on the incubator shelf (132 ± 12%). For this reason, cells exposed to the sham solenoid were used for comparison with cultures exposed to the active coil. Marrow cells were plated at 1.4 × 106/cm2 in square chamber dishes and exposed to 60 Hz electric fields at 9.6 μV/cm from days 1 to 8. Field exposure inhibited osteoclast‐like cell recruitment by 17 ± 3% as compared with sham exposure (p < 0.0001). Several variables, including initial cell plating density, addition of prostaglandin E2 to enhance osteoclast‐like cell recruitment, and field parameters, were also assessed. In this secondary series, extremely low frequency fields inhibited osteoclast‐like cell formation by 24 ± 4% (p < 0.0001), with their inhibitory effect consistent throughout all variations in protocol. These experiments demonstrate that extremely low intensity, low frequency sinusoidal electric fields suppress the formation of osteoclast‐like cells in marrow culture. The in vitro results support in vivo findings that demonstrate that electric fields inhibit the onset of osteopenia and the progression of osteonecrosis: this suggests that extremely low frequency fields may inhibit osteoclast recruitment in vivo.
Determinants of femoral geometry and structure during adolescent growth
Authors: van der Meulen Marjolein C. H. , Ashford Marvin W. , Kiratli B. Jenny , Bachrach Laura K. , Carter Dennis R. 
Published: February 2005

AbstractOur goal was to understand developmental determinants of femoral structure during growth and sexual maturation by relating femoral measurements to gender and developmental factors (age, pubertal stage, height, and body mass). The bone mineral content of the femur was measured by dual energy x‐ray absorptiometry in 101 healthy Caucasian adolescents and young adults, 9–26 years of age. After some simplifying assumptions had been made, cross‐sectional geometric properties of the femoral midshaft were estimated. Two geometry‐based structural indicators, the section modulus and whole bone strength index, were calculated to assess the structural characteristics of the femur. Femoral strength, as described by these structural indicators, increased dramatically from childhood through young adulthood. Regressions were performed between these femoral measurements and the developmental factors. Our data show that of age, pubertal stage, body mass, and height, body mass is the strongest predictor of femoral cross‐sectional properties, and the correlation of body mass with femoral cross‐sectional structure is independent of gender. A model including all four developmental factors and gender did not substantially increase the accuracy of predictions compared with the model with body mass alone. In light of previous research, we hypothesize that body mass is an indicator of in vivo loading and that this in vivo loading influences the cross‐sectional growth of the long bones.
Friction and stem stiffness affect dynamic interface motion in total hip replacement
Authors: Kuiper Jan Herman , Huiskes Rik 
Published: February 2005

AbstractLarge cyclic movements between the femoral stem and bone during the first weeks after total hip arthroplasty may hamper bone ingrowth and adversely affect the eventual success of the arthroplasty. Little is known, however, about the magnitude of the motions and its relationship to design and surgical factors. A two‐dimensional finite element model of a cementless prosthesis inserted into the proximal femur was constructed to study the effects of two mechanical variables—the stiffness of the implant and the coefficient of friction between bone and implant—on the magnitude of the motions. We investigated the influences of these variables on the subsidence of the prosthesis, the magnitudes of the cyclic motions, and the level of the interface stresses. The presence of friction reduced cyclic motions by about 85% compared with a frictionless interface. Once friction was assumed, varying the coefficient of friction had little effect. The effect of friction on the interface stress state and gross subsidence of the prosthesis was not as great as on cyclic motion. Implant stiffness also affected the magnitudes and distributions of the cyclic motions along the interface. A flexible stem generated motions about three to four times larger proximally than those of a stiff stem, which generated larger motions distally. The influence of stem stiffness on interface stresses and prosthetic subsidence was less than on cyclic motion. The location of the peak shear stresses at the interface around a bonded prosthesis corresponded to the location where cyclic interface motion was maximal for an unbonded prosthesis. However, no direct relationship was found between the magnitudes of peak stresses and the amplitudes of cyclic motions.
Differential effects of serum, insulin‐like growth factor‐I, and fibroblast growth factor‐2 on the maintenance of cartilage physical properties during long‐term culture
Authors: Sah Robert L. , Trippel Stephen B. , Grodzinsky Alan J. 
Published: February 2005

AbstractThe effects of fetal bovine serum, insulin‐like growth factor‐I, and fibnoblast growth factor‐2 on the regulation of the functional physical properties of adult bovine cartilage explants during an incubation period of 18–20 days was determined, and the relationship between the measured functional properties of the cartilage and the tissue composition was assessed. Cartilage disks were tested in the uniaxial radially confined configuration by the application of low amplitude oscillatory displacement and measurement of the resultant load and streaming potential. For the control cartilage terminated just after explant, the modulus was 0.39 ± 0.28 MPa, the open circuit hydraulic permeability was 2.0 ± 1.0 × 10−15 m2/(Pa•c), and the electrokinetic (streaming potential) coefficient was −2.3 ± 0.6 mV/MPa. Incubation of cartilage in medium supplemented with serum or insulin‐like growth factor‐I resulted in maintenance of the modulus and electrokinetic coefficient, whereas incubation in basal medium or medium supplemented with fibroblast growth factor‐2 led to a marked decrease from control values in the modulus and the amplitude of the electrokinetic coefficient. All of the culture conditions examined resulted in an increase in permeability that was not statistically significant. The variation in the electromechanical properties of all the cartilage samples tested was related to the density of tissue proteoglycan and collagen (hydroxyproline). The modulus was correlated with both the density of tissue proteoglycan (+0.014 MPa/[mg/ml]) and the density of tissue hydroxyproline (+0.008 MPa/[mg/ml]). The electrokinetic coefficient was also correlated with the density of proteoglycan (−0.080 [mV/MPa]/[mg/ml]) and the density of hydroxyproline (+0.064 [mV/MPa]/[mg/ml]). These data indicate that the regulation of chondrocyte matrix metabolism by growth factors can significantly affect the physical properties and function of cartilage.
Effect of loading and fracture motions on diaphyseal tibial fractures
Authors: Sarmiento Augusto , McKellop Harry A. , Llinas Adolfo , Park Sang‐Hyun , Lu Bin , Stetson William , Rao Raj 
Published: February 2005

AbstractA computerized motion sensor was used to record the three‐dimensional components of interfragmentary motion during healing in three patients with closed, low‐energy fractures of the tibial diaphysis treated with functional braces. At the first measurement session, 2 weeks after fracture, the patients applied approximately 15 kg to the injured limb. Although this produced 1–4 mm of translation of the fragments, this was recovered when the load was removed. The maximum rotational and angulatory displacements often occurred as the patients rose from the chair with no weight applied to the limb and frequently were reduced as the 15 kg of load was applied. Under load, the maximum axial rotation was 3° and the maximum angular displacement was 1°. As with the translations, the initial rotational and angulatory positions of the fragments were recovered when the load was removed and the patient returned to the seated position. At 8 weeks, the patient applied full body weight, producing a maximum interfragmentary translation of 0.5 mm and maximum axial rotation or angulation of 0.5°. Abundant peripheral callus formed in all three fractures, and they healed by 15 weeks through typical gradual consolidation and mineralization of the callus, accompanied by a corresponding reduction in interfragmentary motions.
Recorticalization after bifocal internal bone transport in the double‐plated sheep femur
Authors: Windhager R. , Großschmidt K. , Tsuboyama T. , Siegl H. , Heinzl H. , Seidl G. , Plenk H. 
Published: February 2005

AbstractDistraction osteogenesis and bone remodelling after the end of bone transport were investigated in one femur each of six adult male sheep. A newly designed internal distraction device was used. A custommade osteosynthesis plate was fixed on the lateral side of the femur, and two transporting plates driven by a transcutaneously inserted screwdriver moved two bone cylinders simultaneously over a 40 mm defect. An additional plate was applied ventrally to stabilize the device. Bone transport was begun 2 weeks postoperatively at 1 mm/day at each transporting plate until they came into contact. New bone formation within the distraction gaps was evaluated by computed tomography scans and was quantified at 4 and 6 months by dual energy x‐ray absorptiometry as well as histomorphometry on polyfluorochrome‐labelled undecalcified ground sections and microradiographs. At 4 months, all distraction gaps were bridged by abundant newly formed bone trabeculae, which were reduced and condensed to cortex‐like layers of new bone at 6 months. Less new bone was always found under the lateral device than in the unplated medial and dorsal segments, but the amount of new bone under the ventral plate was comparable with that in the unplated regions. The results of this pilot study show that distraction osteogenesis can be achieved with an internal device such as this one and that recorticalization and restoration of a medullary canal occur despite the relatively rigid internal stabilization by the plates.
Effect of Er: YAG laser holes on osteoinduction in demineralized rat calvarial allografts
Authors: O'Donnell Richard J. , Deutsch Thomas F. , Flotte Thomas J. , Lorente Carol A. , Tomford William W. , Mankin Henry J. , Schomacker Kevin T. 
Published: February 2005

AbstractMassive cortical autografts and allografts have been found to incorporate into host bone very slowly and thus are subject to complications such as fatigue fracture and infection. In order to understand and improve the process of osteogenesis in these types of bone grafts, a new experimental model was developed using bone discs from rat calvaria prepared by demineralization and drilling of 0.5 mm diameter holes with a pulsed, 2.94 μm wavelength Erbium: Yttrium‐Aluminum‐Garnet laser. Four types of bone discs were analyzed: untreated (Type I), demineralized (Type II), laser‐ablated (Type III), and laser‐ablated then demineralized (Type IV). The discs were transplanted into a subcutaneous site in adult Sprague‐Dawley rats and followed for as long as 6 weeks. Histologic analysis of the discs at weekly intervals with use of hematoxylin and eosin staining confirmed the presence of new bone growth in Type‐II and Type‐IV discs. The amount of new bone growth in each disc was estimated by determining the mineral x‐ray attenuation coefficient, which is proportional to mineral density, from digitized radiographs of the discs. The results showed that the processes of demineralization (p < 0.001) and laser ablation with demineralization (p < 0.05) were both significant in enhancing new bone growth in this model. This study demonstrated that osteoinduction can be fostered in cortical bone through the processes of demineralization and laser ablation. To the extent that laser ablation may allow maintenance of structural integrity while altering the surface geometry in such a way as to promote ingrowth of new bone, this experimental model represents an advance in understanding how osteogenesis in cortical bone grafts might be improved.
Myofibroblasts in the healing lapine medial collateral ligament: Possible mechanisms of contraction
Authors: Faryniarz D. A. , Chaponnier C. , Gabbiani G. , Yannas I. V. , Spector M. 
Published: February 2005

AbstractThe specific objective of this study was to determine the chronology of the appearance of the myofibroblast in the healing ligament. The overall goal of our work is to elucidate the cellular mechanism of contraction in this tissue. The myofibroblast has been found to be responsible for wound contraction in many tissues and to be the cause of the contracture in several pathological conditions. This cell type contains the actin isoform previously thought to be unique to smooth muscle cells and displays certain characteristic features at the ultrastructural level. In 26 New Zealand White male rabbits, the right medial collateral ligament was transected, whereas the left medial collateral ligament received a sham operation. The central third of the ligament (ligament scar tissue) was evaluated at 2, 3, 6, 8, 10, and 12 weeks postoperatively by immunohistochemical techniques, transmission electron microscopy, and Western blot analyses. Three other rabbits served as anatomic controls. During the early reparative phase (2 and 3 weeks after transection), there was an increase in the number of cells containing α‐smooth muscle actin as well as augmentation of the α‐smooth muscle actin content within each cell—a finding attributed to smooth muscle cells and pericytes associated with neovascularity. No myofibroblasts were detected at this stage, immediately postoperatively, or in the sham‐operation controls. Ligaments in the remodeling phase of healing (6, 8, 10, and 12 weeks) exhibited α‐smooth muscle actin in fibroblasts (myofibroblasts) as well as in vascular pericytes and smooth muscle cells. During this stage of healing, transmission electron microscopy demonstrated an increase in the number of cells displaying myofibroblastic features. It was estimated that at 12 weeks of healing 10% of the cells at the site of injury were myofibroblasts. This is the first definitive finding of myofibroblasts in the injury site of the healing ligament, to our knowledge. The appearance of myofibroblasts in the 6–12 week healing period, the interval during which the ligament has been shown to contract in studies by other investigators, is a rationale for a hypothesis that a cellular contractile apparatus comprising α‐smooth muscle actin (i.e., the myofibroblast) may contribute to the recovery of original ligament length (and normal in situ strain).