bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of a bone's in vivo 24‐hour loading history for physical exercise compared with background loading
Authors: Koniecynski D. D. , Truty M. J. , Biewener A. A. 
Published: February 2005

AbstractThe present study sought to answer two research questions. First, how distinctive, as a potential osteogenic stimulus, are short‐duration bouts of treadmill exercise relative to sedentary background activity? Second, how well does daily effective strain stimulus relate the loading history for one such exercise program, in comparison with other experimental loading programs, to bone formation? In vivo cortical strains were measured in the tibiotarsus of White Leghorn chickens at a late stage of skeletal growth (14–34 weeks old) under the conditions of a previous investigation of bone formation in response to an exercise program (15 min/day, treadmill gait at 60% maximum speed while carrying 20% body mass) that included sedentary background activity. These strain data were compiled into 24‐hour loading histories of peak cyclic strain, demonstrating that strains were statistically different for exercise and background activities (p < 0.0001), with both the magnitude and number of cyclic strain events being greater during exercise (generally greater than 500 microstrain, 2,500 cycles/day) than during background activity (generally less than 500 microstrain, mean: 775 cycles/day). Strains during exercise accounted for more than 97% of the daily effective strain stimulus for bone adaptation, despite the fact that exercise comprised only 1% of the daily period (15 min/day). The levels of the daily effective strain stimulus were similar to those calculated for strains engendered by artificial loading of functionally isolated avian ulnae, which either maintained bone mass or resulted in a 15% increase of cortical cross‐sectional area in both sets of studies. These results indicate that short‐duration bouts of treadmill exercise and sedentary background activity can represent distinct osteogenic stimuli for adaptive bone modeling. They also provide experimental support for the use of a daily effective strain stimulus to quantify skeletal loading histories for differing programs of physical exercise, although the relative importance of other mechanical and nonmechanical factors requires further investigation.
Mechanical behavior of human morselized cancellous bone in triaxial compression testing
Authors: Brodt Michael D. , Swan Colby C. , Brown Thomas D. 
Published: February 2005

AbstractDespite its widespread use as graft material in orthopaedic surgical procedures, morselized cancellous bone has not yet been well characterized from the standpoint of its mechanical properties. To accommodate the noncohesive nature of this loose particulate form of bone, a triaxial compression test apparatus commonly used in engineering soil mechanics was adapted for the testing of fresh‐frozen human morselized cancellous bone specimens. Triaxial compression tests were run to 30% axial strain at five different levels of confining pressure ranging from 0.276 to 0.552 MPa. The measured axial stress versus axial strain behavior was bimodal, characterized initially by relatively stiff linear behavior, then by a rapid transition to a much more compliant (but, again, approximately linear) domain until test cessation. The apparent axial moduli of both response regions were found to be nearly linear functions of the transverse confining pressure. As typically prepared surgically, the distribution of particle size was found to have approximately 80% of the bone graft, by weight, encompassed in particles 0.42–3.2 mm in size. Triaxial tests of samples segregated by size showed that particle size had no appreciable effect on apparent material properties. The nominal Young's modulus and Poisson's ratio of morselized cancellous bone were 100 MPa and 0.2, respectively.
Biomechanical characterization of osseointegration: An experimental in vivo investigation in the beagle dog
Authors: Brånemark Rickard , Öhrnell Lars‐Olof , Skalak Richard , Carlsson Lars , Brånemark Per‐Ingvar 
Published: February 2005

AbstractThis study reports the results of torsion tests, pull‐out tests, and lateral Ioading tests on osseointegrated commercially pure titanium fixtures. The tests were performed in vivo on six beagie dogs. Three fixtures, each with a diameter of 3.7mm, were installed bilaterally in the tibia of each animal. The mean maximal pull‐out load was 1.55 kN (n = 4) the mean maximal lateral transverse load was 0.21 kN (n = 2), the mean maximal lateral axial load was (0.18 kN (n = 2)) the mean breakpoint torque was 0.31 Nm (n = 3), and the mean maximal torque was 0.43 Nm (n = 3). The torsion test revealed an almost immediate plastic deformation of the interface between the implant and bone: this indicates that although the contact between the bone and the implant is close, there is no strong bond, at least not in shear. The major transfer of load from the implant to the surrounding bone tissue must therefore depend on the design of the implant. A histological evaluation with measurements of the amount of bone in contact with the fixtures was performed. By the use of the histological and mechanical data, it is possible to estimate shear stresses in bone tissue (pull‐out test) and in the interface (torque test), The mean maximal shear stress in bone tissue in the pull‐out tests was 100 MPa (n = 4); the mean shear stress in the interface was 4.3 MPa (n = 3) in the torsion tests at the breakpoint torque and was 6.0 MPa (n = 3) at the maximal torque. It was also possible to estimate the shear modulus of elasticity in the pull‐out and torque tests. The mean shear modulus in pull‐out was 119 MPa (n = 4), and the mean apparent shear modulus in torsion was 9 kPa (n = 3) for an assumed interface thickness of 100 nm and was 86 kPa (n = 3) for an assumed interface thickness of 1.000 nm.
Dye incorporation to enhance the laser ablation of standard and reduced‐modulus bone cements
Authors: Lee Chi L. , Litsky Alan S. , Roberts Cynthia J. 
Published: February 2005

AbstractLaser ablation of acrylic bone cement is an alternative method of cement removal that can be used during revision arthroplasty of cemented implants. This study investigated the feasibility of using a continuous‐wave Argon ion laser (wavelength = 514 nm) with the addition of methylene blue or red dye no. 13 to enhance the ablation of two types of bone cements: polymethylmethacrylate and polybutylmethylmethacrylate. Six cement/dye combinations were studied while power (0.5, 0.75, and 1.0 W) and exposure times (30, 45, 60, and 90 seconds) were varied. The Argon laser was unable to ablafre undyed polymethylmethacrylate or polybutylmethylmethacrylate. However, ablation was shown for both cements with either dye. The red dye had a stronger absorption peak at 514 nm than did the blue dye. Statistically larger ablation areas were seen for red polymethylmethacrylate than for blue polymethylmethacrylate (p < 0.013) at all levels tested. Ablation areas were larger in red than in blue polybutylmethylmethacrylate cement. Blue polybutylmethylmethacrylate cement produced larger ablation areas than did blue polymethylmethacrylate cements at all energy levels tested, with smaller surrounding damage areas. Red polybutylmethylmethacrylate cement also produced larger ablation areas than did red polymethylmethacrylate cement (at 0.75 and 1.0 W), again with smaller damage areas. Damage zones were smallest in red polybutylmethylmethacrylate cements at all test levels. These results suggest that, by using dyes to selectively alter the absorption characteristics of bone cement, laser ablation can be an effective method for cement removal. Changes in the chemical structure of the cement can also influence the response to laser treatment. Furthermore, the absorption spectra of the bone cement can be altered to maximize energy absorption at a wavelength that is not absorbed by bone tissue; this potentially minimizes damage to bone during revision surgery.
Quantitative study of the quadriceps muscles and trochlear groove geometry related to instability of the patellofemoral joint
Authors: Farahmand Farzam , Sejiavongse Wongwit , Amis Andrew A. 
Published: February 2005

AbstractThis was a quantitative study of the major anatomical structures associated with instability of the patellofemoral joint: the quadriceps muscles and the femoral trochlear groove. The attachments of the muscles to the patella, their lines of action, and their relative sizes (physiological cross‐sectional areas) were found. On the basis of the physiological cross‐sectional areas, it was estimated that the central muscles—the rectus femoris and vastus intermedius—contributed 35% of the quadriceps strength, with 40% from the vastus lateralis and 25% from the vastus medialis. The vastus lateralis had the most variable results, with the ratio of the lateralis to the medialis ranging from 0.90 to 2.18; this may be associated with patellar instability. Both the long and oblique parts of the vastus medialis were more oblique than the corresponding parts of the vastus lateralis. Photographic “skyline” views of the trochlear groove produced data on the sulcus angle and ratio of depth to width. The data showed that the trochlear groove did not deepen in the area contacted by the patella with progressive knee flexion (p > 0.53). contrary to popular belief. These data are useful for objective analysis of patellofemoral stability and related surgical interventions.
Fatigue of bone and bones: An analysis based on stressed volume
Authors: Taylor David 
Published: February 2005

AbstractThe measured fatigue strength of a material can be affected by specimen size: tests using a large stressed volume may show a low fatigue strength due to the increased probability of finding weak regions. A Weibull analysis revealed an important size effect in bone and predicted this effect with an accuracy of 12%. This approach also explained apparent inconsistencies in the published data and made it possible to separate and quantify the effects of frequency, loading mode, and material source. The effect of frequency is the same for human and bovine bone, and the differences between different types of loading (tension, compression, and bending) are small (maximum: 12%). By extrapolating to the volume of whole bones, it is concluded that large bones will have a fatigue strength much lower, by a factor of 2–3, than that measured by conventional tests. Failure within 105 cycles is expected to occur at cyclic stresses of 23–30 MPa in human long bones and of 32–43 MPa in bovine bones. Repair is therefore needed to prevent failure at physiological stress levels.
Effect of cooling on cutaneous microvascular adrenoceptors in vivo in the rabbit ear
Authors: Li Zhongyu , Koman L. Andrew , Rosencrance Eileen , Pollock David C. , Smith Beth P. , Strandhoy Jack W. , Smith Thomas L. 
Published: February 2005

AbstractPrevious studies have suggested that moderate cooling increases the responsiveness of vascular α2‐adrenoceptors. However, limited information is available documenting the influence of temperature changes on adrenoceptor responses in the microvasculature of thermoregulatory organs (e.g., the human digit and the rabbit ear) subjected to a wide range of temperatures. In the present study, the effect of local cooling (24°C) on cutaneous microvascular adrenoceptors in the ear was observed in vivo in male New Zealand White rabbits (total: 66 ears). The rabbit ear was studied in a temperature‐controlled tissue bath; the ear preparation was pretreated with terazosin (an α1‐adrenoceptor antagonist) (10−5 M) or a combination of terazosin (10−5 M) and propranolol (a β‐adrenoceptor antagonist) (10−6 M). The microvascular diameter responses of the ear to norepinephrine (10−l1‐10−4M) then were determined at 24 or 34°C, respectively, to determine the influences of low temperature on adrenoceptor responses to norepinephrine stimulation. The results demonstrated that low concentrations of norepinephrine induced vasodilation in arterioles and arteriovenous anastomoses. This vasodilation was followed by vasoconstriction with an increased concentration of norepinephrine in animals with α1‐adrenergic blockade at 34°C. Moderate tissue cooling increased the microvascular maximal response of the rabbit ear to norepinephrine and abolished the vasodilatation induced by a low concentration of norepinephrine. There was no significant difference in the microvascular response to norepinephrine between the two temperature conditions after simultaneous blockade of α1‐adrenoceptors and β‐adrenoceptors. Data from the present study indicate that moderate cooling does not enhance the responsiveness of α2‐adrenoceptors to norepinephrine. In contrast, cooling reduced the β‐adrenergic activity of arterioles and arteriovenous anastomoses after norepinephrine stimulation.
In vitro and In vivo study on the effect of autogenous cancellous bone and intramedullary polymethylmethacrylate on allograft construct strength
Authors: Hanson Peter D. , Warner Chad , Frassica Frank J. , Vanderby Ray , Markel Mark D. 
Published: February 2005

AbstractAn in vitro study was performed to compare the effects of augmenting interlocking nails of one of two diameter (5 or 6 mm) with intramedullary polymethylmethacrylate. Subsequently, an in vivo study was performed to compare the effects of augmenting the interlocking nail with five combinations of intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface or within the medullary canal. Dogs were killed 6 months after the procedure for biomechanical evaluation of the femora in axial compression, mediolateral and craniocaudal bending, and torsion. Results from the in vitrostudy at the proximal osteotomy indicated the 6‐mm inteilocking nail with intramedullary polymethylmethacrylate had greater stiffness than the 5‐mm interlocking nail without it (p < 0.05). At the distal osteotomy, regardless of the diameter of the interlocking nail, the addition of intramedullary polymethylmethacrylate increased stiffness (p < 0.05). Results from the in vivo study indicated greater global construct stiffness with an interlocking nail alone, an interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface, and an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface (p < 0.05). At the osteotomy level, the interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface had greater stiffness than did an interlocking nail alone or an interlocking nail augmented with either intramedullary polymethylmethacrylate. cancellous bone within the medullary canal, or cancellous bone at the periosteal surface (p < 0.05) but produced the same results as an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface. The results suggest that augmenting interlocking nail fixation with intramedullary polymethylmethacrylate by itself offers no advantage but that acombination of intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface improves structural properties at 6 months.
Actions of endothelin‐1,2, and 3 in the microvasculature of bone
Authors: Briggs Peter J. , Moran Christopher G. , Wood Michael B. 
Published: February 2005

AbstractEndothelins have recently been associated with hypoxia‐related vascular smooth‐muscle constriction and with the so‐called no‐reflow phenomenon following reperfusion. Their action is tissue dependent. The role of endothelins on vascular smooth muscle in bone is unknown. An ex vivo perfusion model was used to investigate the effects of the three different endothelins on the vascular resistance in the canine tibia. Endothelin‐1 and endothelin‐2 had molar potencies similar to that of norepinephrine, whereas endothelin‐3 was less potent. Tachyphylaxis to the same dose of endothelin‐1 did not occur. The calcium channel blocker, diltiazem, attenuated (45% reduction) the vasoconstrictor responses to norepinephrine (p < 0.005) but had a smaller effect (24% reduction) on the responses to endothelin (p < 0.025). Vascular smooth muscle in bone appears to have endothelin receptors that are similar to those in other organs.
Semiquantitative reverse transcription‐polymerase chain reaction analysis of mRNA for growth factors and growth factor receptors from normal and healing rabbit medial collateral ligament tissue
Authors: Sciore Paul , Boykiw Raymond , Hart David A. 
Published: February 2005

AbstractGrowth factors and their receptors play an essential role in the development, maturation, and response to injury of all tissues. A number of studies have explored the possibility of improving ligament healing with exogenous growth factors. However, limited data is available regarding the endogenous growth factor network in ligaments on which any exogenous growth factors must impact. The purpose of this study was to assess the endogenous growth factor network with molecular techniques. By the sensitive reverse transcription‐polymerase chain reaction technique, transcripts for a number of growth factors and receptors were detected with RNA isolated from normal and healing rabbit medial collateral ligament tissues. These include transforming growth factor‐β1, insulin‐like growth factors I and II, basic fibroblast growth factor, endothelin‐1, and the receptors for insulin and insulin‐like growth factor II. Semiquantitative reverse transcription‐polymerase chain reaction analysis of RNA from normal and scar tissues from the medial collateral ligament revealed that the levels of several transcripts were elevated in the scar tissue. It was not possible to confirm biological activity because of the hypocellularity of the tissues; however, the results, obtained indicate that the reverse transcription‐polymerase chain reaction approach to defining the endogenous growth factor‐receptor phenotype is feasible, and further definition should contribute to the development of rational approaches to exogenous therapy to improve healing.
In situ calibration of miniature sensors implanted into the anterior cruciate ligament. Part I: Strain measurements
Authors: Markolf Keith L. , Willems Matthew J. , Jackson Steven R. , Finerman Gerald A. M. 
Published: February 2005

AbstractThe goals of this study were to (a) evaluate the differential variable reluctance transducer as an instrument for measuring tissue strain in the anteromedial band of the anterior crudciate ligament, (b) develop a series of calibration curves (for simple states of knee loading) from which resultant force in the ligament could be estimated from measured strain levels in the anteromedial band of the ligament, and (c) study the effects of knee flexion angle and mode of applied loading on ouput from the transducer. Thirteen fresh‐frozen cadaveric knee specimens underwent mechanical isolation of a bone cap containing the tibial insertion of the anterior cruciate ligament and attachment of a load cell to measure resultant force in the ligament. The transducer (with barbed prongs) was inserted into the anteromedial band of the anterior cruciate ligament to record local elongation of the instrumented fibers as resultant force was generated in the ligament. A series of calibration curves (anteromedial bundle strain versus resultant force in the anterior cruciate ligament) were determined at selected knee flexion angles as external loads were applied to the knee. During passive knee extension, strain readings did not always follow the pattern of resultant force in the ligament; erratic strain readings were often measured beyond 20° of flexion, where the anteromedial band was slack. For anterior tibial loading, the anteromedial band was a more active contributor to resultant ligament force beyond 45° of flexion and was less active near full extension; mean resultant forces in the range of 150–200 N produced strain levels on the order of 3–4%. The anteromedial band was also active during application of internal tibial torque; mean resultant forces on the order of 180–220 N produced strains on the order of 2%. Resultant forces generated by varus moment were relatively low, and the anteromedial band was not always strained. Mean coefficients of variation for resultant force in the ligament (five repeated measurements) ranged between 0.038 and 0.111. Mean coefficients of variation for five repeated placements of the strain transducer in the same site ranged from 0.209 to 0.342. Insertion and removal of this transducer at the anteromedial band produced observable damage to the ligament. In our study, repeatable measurements were possible only if both prongs of the transducer were sutured to the ligament fibers.
Mechanical properties of wrist extensor tendons are altered by the presence of rheumatoid arthritis
Authors: Breault‐Janicki Martine J. , Small Carolyn F. , Bryant J. Timothy , Dwosh Isaac L. , Lee J. Michael , Pichora David R. 
Published: February 2005

AbstractThe in vitro mechanical properties of 14 wrist extensor tendons salvaged at surgery from patients with inflammatory (rheumatoid) arthritis and noninflammatory arthrosis were measured in uniaxial tension and compared. The rheumatoid tendons had higher extensibility at low stresses, lower stiffness in the linear portion of the stress‐strain curve, greater rates of stress relaxation, and lower ultimate strengths than did the nonrheumatoid tendons. Differences in tangent modulus, stress remaining at 100 seconds, and ultimate tensile strength were significant at the 95% confidence level. In vivo, mechanically, impaired tendons may play an important role in destabilization of the wrist in patients with rheumatoid arthritis.
Local tissue properties in bone healing: Influence of size and stability of the osteotomy gap
Authors: Augat Peter , Margevicius Kristen , Simon Jörg , Wolf Steffen , Suger Gebhard , Claes Lutz 
Published: February 2005

AbstractTo characterize the site‐specific mechanical and histological properties in fracture repair and to relate these properties to the initial mechanical situation, an experimental fracture model was used in the metatarsus of 42 sheep. the mechanical situation of a transverse osteotomy was described by three gap sizes (1,2, or 6 mm) and two amounts of strain (7 or 31 %). An external fixator that allowed a defined axial movement provided control of these settings. Nine weeks following surgery, the healing area was dissected and tensile and compressive properties were measured in subregions of the fracture gap and the periosteal callus. The central, sagittal section was used for quantitative histology. We found the quality of the tissue along the osteotomy line to be most important for regaining mechanical stability. Increasing the size of osteotomy gaps resulted in poorer mechanical and histological qualities, and the repair process was less complete. Interfragmentary strain did not significantly influence the repair process. The smaller strain levels had already stimulated the secondary repair process, and this stimulatory effect could not be further enhanced by increasing the amount of strain. Our finding that large gaps between bone segments were not as well healed as were smaller gaps suggests that it is advantageous to avoid large gaps in fracture treatment.