bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cortical bone perfusion in plated fracutured sheep tibiae
Authors: Kregor Philip J. , Senft David , Parvin Dara , Campbell Colleen , Toomey Sean , Parker Colleen , Gillespy Thurman , Swiontkowski Marc F. 
Published: February 2005

AbstractThe limited contact dynamic compression plate and partial contact plate were designed to decrease contact with cortical bone in an attempt to decrease cortical ischemia, remodeling, and eventual porosis under the plate after use of standard dynamic compression plates. This study quantified cortical bone blood flow beneath the plate with these three different designs in a sheep tibia fracture model. In 18 skeletally immature sheep, the right tibia was fractured and then was internally fixed with an interfragmentary screw and a dynamic compression plate, limited contact dynamic compression plate, or partial contact plate. At 12 weeks, cortical bone perfusion was assessed with laser Doppler flowmetry in nine areas beneath the plate. The baseline (before fracture) cortical bone cell flux averaged 100 ± 60 mV. After fracture, this decreased to 60 ± 48 mV (p < 0.0003); immediately after plating, the perfusion averaged 29 ± 25 mV (p < 0.01). Cortical bone perfusion then increased to 106 ± 52, 165 ± 71, and 163 ± 71 mV at 2, 6, and 12 weeks after fracture (p < 0.001 for all when compared with values after plating). No significant differences in cortical perfusion were seen between the types of plate. Cortical porosity under the plate was assessed with digital density analysis of microradiographs of this region. No significant difference was seen between the types of plate in this analysis or in biomechanical and disulphine blue perfusion analysis. Thus, no significant advantage was seen for the new plate designs used in this model. This lack of advantage may be a result of the immature animals used in the study, the protocol for blood flow measurement, the invasive periosteal stripping employed to create the fracture, or all three. However, as advantages with the new plate designs have been seen in other studies, this area warrants further investigation.
Laxity characteristics of normal and pathological murine knee joints in vitro
Authors: van Osch Gerjo J. V. M. , Blankevoort Leendert , van der Kraan Peter M. , Janssen Bernard , Hekman Edsko , Huiskes Rik , van den Berg Wim B. 
Published: February 2005

AbstractThe aim of this study was to validate a device developed previously to measure laxity of murine knee joints and to investigate whether experimentally induced pathological conditions result in measurable laxity. The laxity characteristics of normal murine knee joints were derived from measurements of 25 left knees of normal mice. Reporducible, nonlinear s‐shaped load‐displacement curves were determined, and parameters of anterior‐posterior translation, varus‐valgus rotation, and compliance were calculated from the curves. No differences were found between the left and right knee joints of eight mice. The average displacement between 0.8 N of anterior force and 0.8 N of posterior force was 0.47 ± 0.10 mm. The endpoint compliances for anterior and posterior displacements were 0.16 ± 0.03 and 0.16 ± 0.04 mm/N, respectively. The average rotation between a 4 Nmm valgus moment and a 4 Nmm varus moment was 17.4 ± 3.3°. The endpoint compliances for varsus and valgus rotations were 1.1 ± 0.7 and 1.0 ± 0.3°/Nmm, respectively. Storage of the joints at −70°C had no effect on laxity. We also studied the parameters of laxity after pathology of the knee joint was induced. Zymosan‐induced or antigen‐induced arthritis did not increase laxity of the joint. In an osteoarthritis model induced by injection of collagenase, laxity was markedly increased. In conclusion, laxity in the knees of mice can be measured reproducibly, and changes in the characteristics of laxity due to pathological conditions can be quantified.
Role of muscles in lumbar spine stability in maximum extension efforts
Authors: Gardner‐Morse Mack , Stokes Ian A. F. , Laible Jeffrey P. 
Published: February 2005

AbstractMany problems of the lumbar spine that cause pain are attributed to instability. The ligamentous spine (without muscles) is unstable at very low compressive loads. This study examined the hypothesis that instability of the lumbar spine is prevented under normal circumstances by the stiffness of spinal musculature, without active responses from the neuromuscular control system. The effect of muscle activity (force and stiffness) on the stability of the lumbar spine was analyzed for maximum voluntary extension efforts with different spinal postures in the sagittal plane. The analysis included realistic three‐dimensional representation of the muscular anatomy with muscles crossing several motion segments. The stiffness of motion segments was represented using in vitro measured properties. Under a range of conditions with maximum extension effort, active muscle stiffness was required to prevent the lumbar spine from buckling. The dimensionless value of the muscle stiffness parameter q as a function of activation and length had to be greater than a critical value in the range of 3.7–4.7 in order to stabilize the spine. Experimentally determined values of q ranged from 0.5 to 42. These analyses demonstrate how changes in motion segment stiffness, muscle activation strategy, or muscle stiffness (due to degenerative changes, injuries, fatigue, and so on) might lead to spinal instability and “self‐injury”.
Effects of fluid‐induced shear on articular chondrocyte morphology and metabolism in vitro
Authors: Smith R. Lane , Donlon B. S. , Gupta M. K. , Mohtai M. , Das P. , Carter D. R. , Cooke J. , Gibbons G. , Hutchinson N. , Schurman D. J. 
Published: February 2005

AbstractThis study tested the effects of fluid‐induced shear on high density monolayer cultures of adult articular chondrocytes. Fluid‐induced shear (1.6 Pa) was applied by cone viscometer to normal human and bovine articular chondrocytes for periods of 24, 48, and 72 hours. At 48 and 72 hours, fluid‐induced shear caused individual chondrocytes to elongate and align tangential to the direction of cone rotation. Fluid‐induced shear stimulated glycosaminoglycan synthesis by 2‐fold (p < 0.05) and increased the length of newly synthesized chains in human and bovine chondrocytes. In human chondrocytes, the hydrodynamic size of newly synthesized proteoglycans also was increased. After 48 hours of fluid‐induced shear, the release of prostaglandin E2 from the chondrocytes was increased 10 to 20‐fold. In human chondrocytes, mRNA signal levels for tissue inhibitor of metalloproteinase increased 9‐fold in response to shear compared with the controls. In contrast, mRNA signal levels for the neutral metalloproteinases, collagenase, stromelysin, and 72 kD gelatinase, did not show such major changes. This study demonstrated that articular chondrocyte metabolism responds directly to physical stimulation in vitro and suggests that mechanical loading may directly influence cartilage homeostasis in vivo.
Biomechanical properties of third carpal articular cartilage in exercised and nonexercised horses
Authors: Palmer J. L. , Bertone A. L. , Mansour J. , Carter B. G. , Malemud C. J. 
Published: February 2005

AbstractThe relevance of site and exercise on the biomechanical properties of the articular cartilage from the equine third carpal bone were assessed by creep indentation testing. Six horses were exercised for 30 minutes three times weekly. Another six horses were housed in box stalls and were not exercised. At the conclusion of the study, one third carpal bone from each horse was harvested and the KLM biphasic material properties of cartilage were determined at 12 sites. There was a significant (p < 0.01) effect of site but not exercise on the cartilage aggregate modulus, which was significantly lower for sites on the dorsal aspect of the radial facet and for all sites on the intermediate facet as compared with sites on the palmar aspect of the radial facet of the third carpal bone. Exercise significantly increased the permeability constant at all sites when compared with the nonexercised group, but there was no difference between sites within groups. Exercise also significantly increased Poisson's ratio, but only at sites located on the palmar aspect of the radial facet. In general, both site and exercise influence the biomechanical behavior of third carpal articular cartilage. Inherent differences in cartilage biomechanical properties within a joint correlate with the location specificity of cartilaginous lesions in the equine midcarpal joint.
Force attenuation in trochanteric soft tissues during impact from a fall
Authors: Robinovitch Stephen N. , McMahon Thomas A. , Hayes Wilson C. 
Published: February 2005

AbstractThe risk for hip fracture from a fall is known to decrease with increased body mass index (weight/height2), a relative measure of obesity. To explore whether this reduced risk is due to the protective effect of increased soft‐tissue cushioning in obese individuals, we used an impact pendulum and surrogate human pelvis to conduct simulated fall impact experiments on trochanteric soft tissues harvested from the cadavers of nine elderly individuals. For each impact, the total applied energy was 140 J. Peak forces ranged from 4,050 to 6,420 N, and tissue energy absorption ranged from 8.4 to 81.6 J. Increased tissue thickness correlated strongly with both decreased peak force (r2 = 0.91) and increased tissue energy absorption (r2 = 0.76). However, peak forces in all cases were within 1 SD of previously reported average fracture forces forces elderly cadaveric femora. This suggests that force attenuation in trochanteric soft tissues alone is insufficient to prevent hip fracture in falls in which an elderly person lands directly on the hip. In such falls, additional energy‐absorbing mechanisms, such as breaking the fall with an outstretched hand and eccentric contraction of the quadriceps during descent, are likely to be involved if fracture does not occur.
Imaging of immature articular cartilage using ultrasound backscatter microscopy at 50 MHz
Authors: Kim H. K. W. , Babyn Paul S. , Harasiewicz K. A. , Gahunia H. K. , Pritzker K. P. H. , Foster F. S. 
Published: February 2005

AbstractA high frequency sonographic technique–ultrasound backscatter microscopy–was used to visualize the subsurface structure of immature porcine articular cartilage from the knee joint. In 20‐week‐old pigs, all parts that were scanned, except the weight‐bearing regions of the femoral condyles, demonstrated heterogeneous ultrasound backscatter characteristics within the articular cartilage. A trilaminar pattern consisting of hypoechoic, hyperechoic, and anechoic layers ranging from superficial to deep generally was observed, except in the weight‐bearing regions of the femoral condyles, where a homogeneous anechoic pattern was seen. In the younger pigs (6 and 10 weeks old), the trilaminar backscatter pattern was not observed. Small, highly echogenic structures that correlated with vascular channels in histologic assessment were observed frequently in the cartilage of younger pigs, but they were seldom present in the cartilage of 20‐week‐old pigs. Structural details, such as disruption of the subchondral bone and presence of a thickened fibrous layer on the articular surface at the chondrosynovial junction, also were detected with the ultrasound backscatter microscope. We concluded that high frequency ultrasound can be used to visualize the subsurface structure of immature articular cartilage and some of its developmental changes. Further research is required to explain the mechanism underlying the observed backscatter characteristics of immature articular cartilage and to study its potential for the imaging of pathologic changes.
Late changes in bone mineral density of the proximal tibia following total or partial medial meniscectomy: A randomized study
Authors: Petersen Michael Mørk , Olsen Claus , Lauritzen Jes Bruun , Lund Bjarne , Hede Adam 
Published: February 2005

AbstractThe adaptive bone remodeling in the proximal tibia following medial meniscectomy was measured quantitatively by dual photon absorptiometry. Thirty‐three patients who had undergone a meniscectomy (randomized to either total [n = 19] or partial [n = 14] meniscectomy) performed by open joint surgery approximately 12 years earlier were included in the study. Bone mineral density was measured in the previously injured legs and in the healthy contralateral legs in areas located medially and laterally in the cortical bone of the subchondral plates and below in the trabecular bone of the medial and lateral tibial condyles. The distribution of bone mineral within the proximal tibia showed a characteristic and significant pattern. In the trabecular bone of the healthy contralateral knees, bone mineral density was 15% higher in the medial tibial condyles compared with the values laterally: a total or partial meniscectomy increased this difference to 25%. With regard to the cortical bone of the subchondral plates, the bone mineral density in the healthy knees was 24.8–29.4% higher medially than laterally, whereas after total and partial meniscectomy the differences were, respectively, 37.7 and 41.4%. No significant differences in the distribution of bone mineral density, at either cortical or trabecular measuring sites, were found between totally and partially meniscectomized knees.
In vitro stimulation of articular chondrocyte mRNA and extracellular matrix synthesis by hydrostatic pressure
Authors: Smith R. Lane , Rusk S. F. , Ellison B. E. , Wessells P. , Tsuchiya K. , Carter D. R. , Caler W. E. , Sandell L. J. , Schurman D. J. 
Published: February 2005

AbstractThis study tested the effects of hydrostatic pressure (10 MPa) on adult articular chondrocyte mRNA and extracellular matrix synthesis in vitro. High density primary cultures of bovine chondrocytes were exposed to hydrostatic pressure applied intermittently at 1 Hz or constantly for 4 hours in serum‐free medium or in medium containing 1% fetal bovine serum, mRNAs for aggrecan, types I and II collagen, and β‐actin were analyzed by Northern blots and quantified by slot blots. Proteoglycan synthesis was quantified by 35SO4 uptake into cetylpyridinium chloride‐precipitable glycosaminoglycans, and cell‐associated aggrecan and type‐II collagen were detected by immunohistochemical techniques. In serum‐free medium, intermittent pressure increased aggrecan mRNA signal by 14% and constant pressure decreased type‐II collagen mRNA signal by 16% (p < 0.05). In the presence of 1% fetal bovine serum, intermittent pressure increased aggrecan and type‐II collagen mRNA signals by 31% (p < 0.01) and 36% (p < 0.001), respectively, whereas constant pressure had no effect on either mRNA. Intermittent and constant pressure stimulated glycosaminoglycan synthesis 65% (p < 0.001) and 32% (p < 0.05), respectively. Immunohistochemical detection of cell‐associated aggrecan and type‐II collagen was increased in response to both intermittent and constant pressure. These data support the hypothesis that physiologic hydrostatic pressure directly influences the extracellular matrix metabolism of articular chondrocytes.
Enhanced denaturation of the α1(II) chains of type‐II collagen in normal adult human intervertebral discs compared with femoral articular cartilage
Authors: Hollander Anthony P. , Heathfield Terrence F. , Liu Jane J. , Pidoux Isabelle , Roughley Peter J. , Mort John S. , Poole A. Robin 
Published: February 2005

AbstractThe mechanical strength of connective tissues is dependent on the integrity of their fibrillar collagen frameworks. The objective of the present study was to assess type‐II collagen damage (denaturation) in the adult human intervertebral disc compared with articular cartilage, in order to determine whether damage to this molecule may vary in different anatomical sites in the same person. A new immunochemical assay was used to measure the amounts of denatured and total type‐II collagen in the annulus fibrosus and nucleus pulposus of the L5‐S1 disc and in cartilage from the femoral condyles of the same individuals (n = 7). Denaturation of type‐II collagen was significantly higher in both the annulus fibrosus and the nucleus pulposus than in articular cartilage. Such increased damage to type‐II collagen in the adult disc may have relevance to the more pronounced degenerative changes observed in this tissue compared with articular cartilage.
Effect of alendronate on fracture healing and bone remodeling in dogs
Authors: Peter C. P. , Cook William O. , Nunamaker David M. , Provost Michael T. , Seedor J. Gregory , Rodan Gideon A. 
Published: February 2005

AbstractTo examine the effect of alendronate (4‐amino‐1‐hydroxybutylidene bisphosphonate) on fracture repair, the drug was given to mature beagle dogs orogastrically at 2 mg/kg/day for 9 weeks preceding fracture, 16 weeks after fracture, or both before and after fracture (25 weeks). A transverse mid‐diaphyseal fracture of the right radius was surgically induced and was stabilized by external coaptation splinting. Fracture healing and bone remodeling were evaluated by radiography, gross and histological examination, and bone histomorphometry. The mechanical properties of the fracture callus were determined by a four‐point bending test. Radiographs and gross and microscopic examination demonstrated normal bone healing at the fracture site in all dogs. In dogs that received alendronate during the fracture healing period, at 16 weeks the calluses were approximately 2–3 times larger than those in dogs that received a placebo during the healing period. This is consistent with slower callus bone remodeling, an expected pharmacological effect of the compound. Bone histomorphometry demonstrated that treatment with alendronate did not inhibit bone formation or mineralization. Mechanical testing showed that the ultimate load at failure and the flexural rigidity of both the fractured and contralateral intact bone were unaffected by treatment with alendronate. Therefore, in this study, treatment with alendronate before or during fracture healing, or both, resulted in no adverse effects on the union, strength, or mineralization of bone in mature beagle dogs.
Qualitative and quantitative analysis of orthotopic bone regeneration by marrow
Authors: Werntz Joanne R. , Lane Joseph M. , Burstein Albert H. , Justin Robert , Klein Robert , Tomin Emre 
Published: February 2005

AbstractA rat model of a femoral segmental defect was used to specifically test the hypothesis that autogenous marrow has the osteogenic capability to heal a bone defect. The variables analyzed included the ratio of the marrow volume to the defect, implantation of live or dead marrow, and remodeling of established nonunions by implantation of live marrow. The uniqueness of this model allows biomechanical evaluation of the new bone formed by the implant. When live marrow was implanted, woven bone formed at 3 weeks, progressing to early lamellar bone at 6 weeks, with subsequent remodeling for as long as 12 weeks in a volumetric fashion (p < 0.05). Bone marrow, when placed in a fresh femoral defect and given in sufficient amounts, produced a rate of union comparable with that of autologous bone grafts. Mature lamellar bone formed by marrow was evaluated biomechanically: the results were statistically comparable with those of cancellous bone grafts at 12 weeks. Significant bone formation occurred when marrow was percutaneously injected in femoral nonunions, although union and remodeling did not take place in this rat model. Implantation of dead marrow resulted in rare cellular infiltration and minimal bone formation in a manner comparable with that of autogenous cancellous bone grafts. These results indicate that bone marrow can lead to structurally functional bone regeneration in an orthotopic location.
Uniaxial tension inhibits tendon collagen degradation by collagenase in vitro
Authors: Nabeshima Y. , Grood E. S. , Sakurai A. , Herman J. H. 
Published: February 2005

AbstractTendon structure is governed largely by factors regulating the anabolic and catabolic phases of tenocyte metabolism. Little is known about the mechanisms that regulate the synthesis, activation, and action of metalloproteinases, which are key enzymes in a multifactorial cascade controlling homeostasis of the extracellular matrix. In the present study, we investigated the effect of tension on collagenase‐induced degradation of the tendon in vitro by assessing changes in structural and material properties measured during tensile failure tests. Devitalized right‐left pairs of rabbit patella‐patellar tendon‐tibia units were maintained under culture conditions in the presence of 60 U/ml highly purified collagenase for 20 hours. One randomly selected unit from each animal was subjected to a tension that produced a constant 4% elongation or strain (n = 10); the contralateral unit served as a slack comparison (n = 10). In one series of experiments (immediate, n = 5), the tension was applied immediately prior to collagenase exposure. In a second series (delayed, n = 5), it was delayed for 4 hours to allow time for the collagenase to diffuse into the tendon. Additional devitalized and nonincubated units (n = 6) were used as normal controls. Collagenase exposure caused large decreases in stiffness and elongation to failure in slack units. This resulted in greater than 80% reductions in both maximum failure force and energy to failure. In contrast, the loaded unit in both experimental protocols had significantly greater stiffness than control units. In both the immediate and the delayed protocols, the loaded tendons had significantly higher stiffness and failed at significantly higher elongations and maximum forces than the slack tendons. Diffusion studies with and without tension showed the tension did not inhibit diffusion of collagenase into the tendon but did significantly decrease the water content from 64.6 to 57.8%. The data suggest that stresses and strains of the extracellular matrix may modify the kinetics of the bacterial collagenase‐collagen interaction. Matrix stress and strain may be an important and overlooked factor that modulates the susceptibility of collagen to proteolytic degradation.
Reproducibility of isometric trunk extension torque, trunk extensor endurance, and related electromyographic parameters in the context of their clinical applicability
Authors: van Dieën Jaap H. , Heijblom P. 
Published: February 2005

AbstractTesting the capacity of the trunk extensor muscles may be useful in the diagnosis of low back pain. In the present study, the reproducibility of measurements of maximum trunk extension force, trunk extension endurance, and related electromyographic parameters was investigated. Intraclass correlations indicated that the reproducibility of maximum force and endurance time was satisfactory. Nevertheless, the smallest difference in these parameters that could be attributed, with 95% confidence, to a change in the condition of a patient was, in general, more than 20%. On the electromyograms, the slopes of amplitude and frequency content appeared to be related to endurance time. The reproducibility of these parameters in terms of the intraclass correlation was again satisfactory; however, the smallest detectable difference generally exceeded 50%. The clinical applicability of the parameters studied is severely limited by a lack of reproducibility.