bluuebunny/crossref_metadata_2025_split huggingface dataset:
S‐100 protein immunostaining identifies cells expressing a chondrocytic phenotype during articular cartilage repair
Authors: Wolff D. A. , Stevenson S. , Goldberg V. M. 
Published: February 2005

AbstractThe healing of articular surface defects has been studied with conventional histology, which relies on the staining of the extracellular matrix to identify the phenotype of the cells present. A chondrospecific cellular marker would be useful. S‐100 protein has been found in all chondroid tissues studied, and we evaluated its usefulness in the study of articular cartilage repair. Fullthickness rabbit femoral condylar defects were made, and the specimens were studied at serial time intervals. S‐100 protein staining positively showed chondroid cells in the 7‐ and 14‐day specimens, which were not identifiable by conventional techniques. At 30 and 60 days, an S‐100 positive band of cells separated a deep safranin‐O positive hypertrophic layer from a fibrocellular surface layer. At 120 days, the presence of S‐100 protein identified cells with chondrogenic potential, and the lack of S‐100 protein in other cells embedded in conventionally stained matrix suggested that these cells were no longer of a chondroid phenotype. The presence of S‐100 protein‐identified chondroid cells early in the repair process when the cells had not begun to synthesize conventionally stainable matrix and the lack of S‐100 protein in cells late in the repair positively identified a phenotypic change earlier than conventional histology.
Structural consequences of subchondral bone involvement in segmental osteonecrosis of the femoral head
Authors: Brown Thomas D. , Baker Kelly J. , Brand Richard A. 
Published: February 2005

AbstractAppearance of a crescent sign usually marks the onset of necrotic femoral head collapse, but very little is known about which local factors contribute most critically to avoiding or postponing fracture of at‐risk juxtaarticular cancellous bone. A three‐dimensional finite element model was used to test the hypothesis that an initially mechanically uncompromised subchondral plate could provide a substantial degree of stress protection to a weakened underlying segmental infarction. The computational simulation of osteonecrosis showed that the principal stress distribution for an assumption of subchondral plate weakening (given also an underlying, comparably weakened segmental infarction) differed inappreciably from that of a normal femoral head. However, the tendency for local structural failure, as reflected in the ratio of stress to strength, was substantially higher in the former instance. If, instead, the mechanical integrity of the subchondral plate overlying the weakened segmental infarction was assumed to be preserved, computed stress levels in the at‐risk subjacent necrotic cancellous bone were still over 70% as high as for the weakened‐plate case. The data thus indicate that even a fully normal subchondral plate can provide only modest stress protection of a weakened underlying segmental infarction, whereas weakening of the necrotic cancellous bone throughout the infarction induces marked stress increase in the overlying subchondral plate. These findings suggest that the onset of collapse is probably dominated much more strongly by the degree of structural degradation of the cancellous bone within the main infarct body, than by the degree of structural degradation within the subchondral plate.
Effect of tension and placement of a prosthetic anterior cruciate ligament on the anteroposterior laxity of the knee
Authors: Fleming B. , Beynnon B. , Howe J. , McLeod W. , Pope M. 
Published: February 2005

AbstractWe wished to determine the optimal tensions required to restore normal joint laxity to anterior cruciate ligament (ACL)‐deficient knees using a braided polyethylene ACL prosthesis (PACL). In 10 cadaveric specimens, we measured the anteroposterior (AP) laxity of the intact knee at 10°, 30°, 60°, and 90° of flexion. The ACL was then removed and replaced with the PACL using tunnel‐tunnel (T‐T) and “over‐the‐top” (OTT) placement techniques. In both positions, the PACL was initially tensioned to 0, 9, 18, and 27 N with the knee flexed to 30°. AP joint laxity was then measured at each flexion angle. With an increase in initial tension, there was a corresponding decrease in AP laxity. At 30° and 90° of flexion, AP laxity was not significantly different from normal using T‐T placement and an initial tension of 0 N. At 90° of flexion, AP laxity was not signifincantly different from normal using OTT placement at 0 or 9 N of initial tension. For both positions, all other tension levels and flexion angles constrained AP laxity. No laxity differences were detected between the OTT and T‐T positions at any flexion angle. The variability in AP laxity of the T‐T position was significantly greater than OTT. With a 150‐N anterior shear force applied to the proximal tibia, the maximum tensions developed in the PACL were not significantly different between the two positions except at 90°. The results suggest that implantation of the PACL is best performed using OTT positioning with an initial tension of 0 N applied at 30° of knee flexion.
Trunk positioning accuracy in children 7‐18 years old
Authors: Ashton‐Miller James A. , McGlashen Kelly M. , Schultz Albert B. 
Published: February 2005

AbstractTrunk proprioception was measured in 253 healthy children 7‐18 years of age using infrared markers placed on the back of the head and on the skin over the T1, T8, and S1 spinous processes. The children were tested for their accuracy in sensing return of the head and trunk to a centered, neutral position in the frontal plane. Whole‐body sway was also quantified during 10 s of relaxed standing by measuring mean amplitudes of trunk marker and foot center of pressure (CP) movements. The results show that trunk positioning accuracy improved significantly with age (p = 0.000). Subjects could position their trunk in the frontal plane to within a mean (±SD) of 2.5 (±1.1) and 0.9 (±0.6)± of the neutral position at ages 7 and 18 years, respectively. No statistically significant gender differences were found. At every age trunk positioning accuracy was diminished in the presence of a continuous external trunk moment (equivalent to 0.01 × body weight × height), although not significantly so. Neither mean trunk sway nor CP amplitudes were significantly correlated with age or sex. The overall results suggest that spine decompensation is only abnormal when it exceeds 20 mm in healthy children and adolescents.
Mechanical properties of microcallus in human cancellous bone
Authors: Blackburn Joanne , Hodgskinson Richard , Currey John D. , Mason Jennifer E. 
Published: February 2005

AbstractUntil now, the mechanical properties of the microcalluses that form in human cancellous bone have been unexplained. We measured the micro‐hardnesses of microcalluses in cancellous bone, of the trabeculae within the microcalluses, of the trabeculae adjacent to microcalluses, and of trabeculae lacking microcalluses in a human tibia and femur. We observed no important differences between materials at the four different sites. Because the microhardness of bone is very closely related to its stiffness, this finding indicates that microcalluses are likely to stiffen the trabeculae in which they are formed, even though they may surround unhealed fractures of the cancellous trabeculae.
Comparison of asymmetrical and symmetrical pulse waveforms in electromagnetic stimulation
Authors: Pienkowski D. , Pollack S. R. , Brighton C. T. , Griffith N. J. 
Published: February 2005

AbstractPulsing electromagnetic field (PEMF) stimulation is a noninvasive therapeutic modality that has been successfully used to stimulate healing of surgically resistant human bone fracture nonunions. Asymmetry of the stimulaus pulse waveform was thought to be necessary for therapeutic effectiveness, but asymmetrical pulses require significant electrical energy that constrains clinical delivery systems to suboptimal designs. Development of low‐energy consuming stimuli will enable clinical device improvements and may provide additional information about the interaction of electromagnetic fields with tissues. The objectives of this study were (a) to determine if asymmetry of the stimulus pulse waveform is needed for efficacy and (b) to determine if symmetrical pulse waveform stimuli also can produce a beneficial therapeutic response. The rabbit fibular osteotomy model was used to answer these questions and to identify which components of the clinically used asymmetrical PEMF produce the therapeutic response. The results suggest that assymmetry is not necessary and that a narrow pulse width, symmetrical square wave signal can also stimulate stiffness increases in this model. The data also suggest that the high‐amplitude, narrow‐pulse portion of the asymmetrical PEMF is the principal component of the signal pulse that is responsible for the clinical therapeutic effect.
The microstructural tensile properties and biochemical composition of the bovine distal femoral growth plate
Authors: Cohen B. , Chorney G. S. , Phillips D. P. , Dick H. M. , Buckwalter J. A. , Ratcliffe A. , Mow V. C. 
Published: February 2005

AbstractThe tensile properties of distal femoral growth plates from 12‐month‐old cows were determined on uniformily prepared straight bone‐growth plate‐bone specimens (7 × 7 mm2 in cross‐section) from predetermined anatomical sites on the physis. Each specimen was distracted to failure using a computer‐controlled servo‐hydraulic testing machine at a strain rate of 0.004 s−1. It was found that the exponential constitutive law, using finite deformation formulation for strain, provides an excellent description of the stress‐strain behavior of all the specimens up to the point of failure. The ultimate stress and both tangent moduli (i.e., the toe region tangent modulus and the tangent modulus calculated at 75% of ultimate strain) varied with anatomical site. The anterior region was the strongest, followed by the posterior/lateral. The anterior and posterior/lateral regions were also the stiffest, whereas the posterior/medial and center regions were the weakest and most compliant. The bone‐growth plate‐bone specimen exhibited a low ultimate strain (13.8% ± 6%) that did not vary significantly throughout the growth plate. This result suggests that disruption of the physis may occur in vivo even at the lower distractions currently recommended for the clinical chondrodiatasis procedure for leg lengthening. The biochemical composition of the growth plate in the anatomical regions correlated well with the tensile properties. There was a greater collagen content in the regions that were the stiffest and strongest. The gross morphology of the growth plate of the bovine distal femur is also described in this study. There is a regular pattern to the undulations of the physis at several dimensional levels. Histologic findings showed that orientation of the hypertrophic cell columns and transphyseal septa are aligned nearly parallel to the longitudinal axis of the diaphyseal shaft. This column orientation is not affected by the undulation of the primary contour of the physis, which at certain locations may be inclined as much as 60° relative to the diaphyseal axis. The orientation of the hypertrophic cell columns appears to be one of the dominant microstructural features influencing the tensile behavior of the bone‐growth plate‐bone specimens.
Treatment of proteoglycan aggregates with physeal enzymes reduces their ability to inhibit hydroxyapatite proliferation in a gelatin gel
Authors: Boskey A. L. , Maresca M. , Armstrong A. L. , Ehrlich M. G. 
Published: February 2005

AbstractIn vitro, cartilage proteoglycans (PGs) are effective inhibitors of hydroxyapatite formation and growth. Their inhibitory ability decreases with decreasing PG size and charge density. It has been suggested that the enzyme‐mediated alteration in the size and conformation of PGs in the growth plate may similarly facilitate the calcification process. In this study, a gelatin gel system was used to monitor hydroxyapatite formation and growth in the presence of proteoglycan aggregates, before and after enzyme treatment. To reproduce the physeal degradation cascade, an enzyme preparation was used that contained all of the growth plate enzymes. At a concentration of 500 μg/ml, the untreated proteoglycan aggregates reduced the amount of mineral formed by 30%. When the aggregates were treated with the heat‐inactivated enzyme, the same extent of inhibition was found. In contrast, treating the aggregates with the crude growth plate enzyme preparation removed all the inhibitory ability, such that 500 μg/ml of proteoglycan preparation yielded 10% more mineral than the controls. Treatment of the aggregates with chondroitinase ABC and trypsin, similarly removed all the inhibitory ability. These data, suggest that enzymatic degradation of proteoglycans may contribute to the regulation of growth plate calcification.
Increased release of matrix components from articular cartilage in experimental canine osteoarthritis
Authors: Ratcliffe Anthony , Billingham Michael E. J. , Saed‐Nejad Fatemeh , Muir Helen , Hardingham Timothy E. 
Published: February 2005

AbstractThe release rates of specific components of the proteoglycan aggregates (G1 domain, the chondroitin sulfate and keratan sulfate containing portion of the protein core, and link protein) of the articular cartilage of mature beagles were studied at early stages of canine experimental osteoarthritis (OA), generated by transection of the anterior cruciate ligament. Analysis of cartilage explants and synovial fluids indicates that at early stages of experimental OA, there is increased release of the proteoglycan aggregates of the articular cartilage. This involves a release from the tissue of the components of the proteoglycan that are specifically involved with aggregation together with the glycosaminoglycans of the proteoglycan. These components were detected at elevated levels in the media of explants of cartilage from the operated joint, and in the synovial fluids of the operated joints.
Effects of β‐adrenergic blockade in an osteoblast‐like cell line
Authors: Majeska R. J. , Minkowitz B. , Bastian W. , Einhorn T. A. 
Published: February 2005

AbstractThe β‐adrenergic blocking agent propranolol was shown in previous studies to increase orthotopic bone formation in rats. To understand the cellular mechanisms underlying this observation, propranolol was tested for its effects on osteoblastic cells, which posses adenylate cyclase‐coupled β‐adrenergic receptors. The ability of propranolol to modulate parathyroid hormone (PTH) and isoproterenol effects on adenylate cyclase activity and on alkaline phosphatase expression was studied in the osteoblast‐like rat osteosarcoma cell line ROS 17/2.8. At concentrations between 0.1 and 10 μM, DL‐propranolol specifically inhibited adenylate cyclase stimulation by the β‐adrenergic agonist isoproterenol, but did not alter either basal or PTH‐stimulated activity. At these concentrations, propranolol also blunted the inhibition of alkaline phosphatase activity by isoproterenol but not PTH. Propranolol alone had minimal effects on ROS alkaline phosphatase activity at low concentrations (0.1–1 μM), but became inhibitory at high concentrations (10–100 μM). Thus, the direct effects of physiologically relevant propranolol concentrations on osteoblastic cells can be attributed principally to β‐adrenergic blockade. These findings further suggest that propranolol may enhance bone formation by preserving osteoblastic activity in the face of inhibition by β‐adrenergic agonists.
Role of loads and prosthesis material properties on the mechanics of the proximal femur after total hip arthroplasty
Authors: Cheal Edward J. , Spector Myron , Hayes Wilson C. 
Published: February 2005

AbstractThe objective of this study was to establish the role of loads and prosthesis material properties on the mechanics of the proximal femur after total hip arthroplasty. We developed a three‐dimensional finite element model of an intact human femur and the same femur with a conventional collared straight‐stem femoral component. Using published data, we defined two sets of loading conditions: one that represented three phases of gait, and one that represented four different extreme loads. The four extreme loads were based on the peak joint contact forces that occur during stair ascent and isometric contraction of various muscle groups. The model was analyzed with three different material properties for the prosthesis, including cobalt‐chromium alloy, titanium alloy, and a carbon fiber‐reinforced polymer (CFRP) laminate. We assumed that the implant was stable, with rigid bonding, collar contact, and no cement. To address femoral component loosening, we examined the shear stresses at the implant‐bone interface; to address adaptive bone remodeling, we examined the principal stresses in the supporting cortical bone relative to those in the intact femur. Our analyses of the various loading conditions demonstrated large out‐of‐plane bending moments and torsional moments, especially for the load representing stair ascent. Based on stepwise multiple regressions, the maximum shear stresses at the implant‐bone interface in the distal region were dependent on the total applied axial force and torsion; the maximum shear stresses in the proximal region were dependent on the axial component of the joint contact force alone. Reduction in the prosthesis stiffness, by substitution of the CFRP material properties, resulted in lower interface shear stresses at the distal end of the stem and higher interface shear stresses at the more proximal sections, consistent with the findings of others. We fit equations, based on composite beam theory, to the maximum implant‐bone interface shear stresses and the cortical bone principal stresses as a function of the axial modulus of the prosthesis. These equations can be used to estimate the maximum stresses at the interface and in the cortical bone that would be predicted by similar models, for the same prosthesis constructed of alternative materials, relative to the stresses in the intact femur. The nonlinear nature of these relationships was such that the cortical bone stresses changed more rapidly, as a function of the prosthesis modulus, for lower values of elastic modulus, especially in the more proximal sections.
The axes of rotation of the thumb carpometacarpal joint
Authors: Hollister Anne , Buford William L. , Myers Loyd M. , Giurintano David J. , Novick Andrew 
Published: February 2005

AbstractTwo axes of rotation of the carpometacarpal (CMC) joint of seven cadaver thumbs were located using an axis finder. The flexion‐extension axis is located in the trapezium and the abduction‐adduction axis is in the first metacarpal. These axes are fixed, are not perpendicular to each other or to the bones, and do not intersect. Motion of the first metacarpal on the trapezium can be defined by these two axes. Understanding of the movements of the basal joint of the thumb is essential to the study of its function and reconstruction.
Development of vascularization in the chondroepiphysis of the rabbit
Authors: Ganey Timothy M. , Love Sheila M. , Ogden John A. 
Published: February 2005

AbstractAlthough numerous studies have addressed the presence of cartilage canals within developing epiphyses, the chronology of their appearance and their vascular contribution to the developing chondroepiphysis remain to be studied. We have selected a model, similar to the developing human skeletal system, in which extensive cartilage canal development precedes the subsequent secondary ossification process. In the rabbit proximal tibia, both chondroepiphyseal and vascular (cartilage canals) development were quantified from the first evidence of vessels until the formation of the secondary center of ossification. The volume of hyaline cartilage increased 25 times after intraepiphyseal vessels were initially observed. The blood supply, measured in cartilage canal volume, increased 400‐fold over the same period. Three distinct cartilage canal morphologies were identifiable before the formation of the secondary center of ossification: (a) an early phase, in which the canals appeared as infoldings derived from the perichondrium; (b) a reactive phase, occurring simultaneously with chondrocyte hypertrophy and characterized by a very large increase in mesenchymal cells within the cartilage canal; and (c) a vascular phase, coincident with mineralization of the matrix, in which the familiar, unitary canal morphology was replaced by that of a vascular plexus. While matrix mineralization and the formation of bone seem dependent on critical cellular events, notably chondrocyte hypertrophy, the role that the vascular supply plays in developing sufficient biological inertia for the ossifying transition must not be underestimated.
Contact characteristics of the subtalar joint: The effect of talar neck misalignment
Authors: Sangeorzan Bruce J. , Wagner Ulrich A. , Harrington Richard M. , Tencer Allan F. 
Published: February 2005

AbstractIn this study we determined the effects of misalignment of the talar neck on the contact characteristics of the subtalar joint. Each of seven fresh cadaver lower extremities was mounted in a loading jig and a vertical load was applied, 90% of which was directed through the tibia and 10% through the fibula. The foot was allowed to displace freely in the horizontal plane so that relative rotations, known to occur in the subtalar joint, would not be prevented. Pressure‐sensitive film, inserted into the posterior and anterior/middle articulations, was used to quantify changes in contact characteristics. After testing in the normal condition, the talar neck was osteotomized and stabilized with internal and external skeletal fixation. Contact characteristics were then determined in each of the following stages: anatomic realignment, or with 2‐mm displacement of the talar neck either dorsally, medially, laterally, or complex (dorsal and varus) with respect to the body of the talus. Measurements showed no significant changes in overall contact area or high pressure area in the posterior facet, although four of the seven specimens demonstrated increased localization of the contact area into two discrete regions. The combined anterior/middle facet, on the other hand, was significantly unloaded by all but medial displacement of the talar neck. An extraarticular load path and/or increased loading directly on the talonavicular joint was presumed to account for the loss of load transfer in the talocalcaneal joint.
The effects of fluoridated water on bone strength
Authors: Turner Charles H. , Akhter M. P. , Heaney Robert P. 
Published: February 2005

AbstractFluoride from fluoridated water accumulates not only in the enamel of teeth but also in the skeleton. The effects of fluoridated water on the skeleton are not well understood, yet there is some evidence that fluoridated water consumption increases the incidence of fractures. In the present study, femoral bending strength was measured in rats on fluoride intakes that ranged from low levels to levels well above natural high fluoride drinking water. Bone strength followed a biphasic relationship with bone fluoride content. Fluoride had a positive effect on bone strength for lower fluoride intakes and a negative influence on bone strength for higher fluoride intakes. The vertebral fluoride content at which femoral strength was maximum was between 1,100 and 1,500 ppm. The increase in femoral strength at this fluoride level was not accompanied by an increase in femoral bone density. The optimal fluoride content is within the range of bone fluoride contents found in persons living in regions with fluoridated water (1 ppm) for > 10 years.