bluuebunny/crossref_metadata_2025_split huggingface dataset:
Achilles tendon healing: A correlation between functional and mechanical performance in the rat
Authors: Best Thomas M. , Collins Alison , Lilly Edward G. , Seaber Anthony V. , Goldner Richard , Murrell George A. C. 
Published: February 2005

AbstractThe pathogenesis and treatment of rupture of the Achilles tendon remain a source of controversy. This study presents the results of a biomechanical, functional, and morphological evaluation of a group of rats that had division and repair of the Achilles tendon. A total of 46 rats were used: 18 for biomechanical testing, 18 for functional evaluation, and 10 for histology. Morphological examination revealed an early inflammatory response with loose connective tissue formation that was replaced gradually by fibroblasts and a collagenous matrix. The functional evaluation (Achilles functional index [AFI]) was made from measurements of the hind pawprints of walking rats. Division and repair of the Achilles tendon produced a significant functional impairment (mean [±SEM] AFI = −87 ± 8; p < 0.001), which gradually improved with healing time. The load to failure for the repaired tendons consistently improved with healing time, in a manner similar to the functional recovery. The average deformation (repair/control) varied considerably and was not related to healing time. The stiffness of the repaired tendons increased with healing time and was 60% of the corresponding control side by day 15. The major finding of this study was a strong correlation between the AFI and the failure load of the healing tendon‐bone constructs (250–300 g group, r = 0.97, p < 0.001; 325–375 g group, r = 0.96, p < 0.001).
Cyclic stretching of human osteoblasts affects proliferation and metabolism: A new experimental method and its application
Authors: Neidlinger‐Wilke Cornelia , Wilke Hans‐Joachim , Claes Lutz 
Published: February 2005

AbstractWe developed an experimental system to stimulate cell cultures by uniform and cyclic biaxial strain of the cell culture surface. The studies reported here were designed to determine the uniformity of the strain distribution, the suitability of the surface for the growth of human osteoblasts, and the effects of strain magnitude on cell proliferation and alkaline phosphatase (AP) activity. Subconfluent cell cultures were grown in rectangular silicone dishes that were stretched cyclically (1 Hz) in the long axis by an electromechanical apparatus that controlled peak stretch and cycle frequency. We applied cyclic strains (1.0, 2.4, 5.3, and 8.8% surface strains) for 15 minutes per day on 3 consecutive days. Phase contrast microscopy confirmed the transfer of dish surface strain to the cells. Stretching of the dish resulted in a homogeneous strain distribution that deviated approximately 0.05% from the applied strain. In comparison with plastic dishes, there was a 20% reduction of cell proliferation on the silicone substrate whereas morphology, AP activity, and total protein content of the cells were similar. The proliferation of human osteoblasts was increased significantly (16.4–100%) by 1% strains, although higher strain magnitudes had lesser (nonsignificant) effects or decreased the mitotic activity of the cells. AP and lactate dehydrogenase activities were not influenced significantly by cyclic strains. This study demonstrates that the cell stretching system is suitable for the investigation of the effects of well defined cyclic strains.
Aging, vertebral density, and disc degeneration alter the tensile stress‐strain characteristics of the human anterior longitudinal ligament
Authors: Neumann P. , Ekström L. A. , Keller T. S. , Perry L. , Hansson T. H. 
Published: February 2005

AbstractThe mechanical properties of the human lumbar anterior longitudinal ligament were investigated, and the influence of aging, disc degeneration, and vertebral bone density on these properties was determined. Tensile mechanical properties of the vertebra‐anterior longitudinal ligament‐vertebra complex were determined for 16 segments from cadavera of individuals who had been 21–79 years old (mean, 52.1 years) at the time of death. Regional strain patterns associated with three sites across the width and three sites along the length of the anterior longitudinal ligament were measured with use of a video‐based motion analysis system. In the young, normal anterior longitudinal ligament, the elastic moduli of the insertion and substance regions of the ligament were similar (approximately 500 MPa). During aging (21–79 years), the elastic modulus of the substance region increased 2‐fold, whereas the elastic modulus of the insertion decreased 3‐fold; this resulted in an approximately 5‐fold difference in elastic modulus between these regions in the older spine. The strength of the bone‐ligament complex decreased approximately 2‐fold (from 29 to 13 MPa) over this same age range. The outer portion of the anterior longitudinal ligament consistently had the highest peak tensile strains (11.8 ± 2.7%) in all of the specimens examined. Preparations with nondegenerated discs and high bone density were significantly stronger (66%) and failed in the ligament substance; in contrast, segments from older individuals with degenerated discs and lower bone density failed in the ligament insertion regions.
Electric field stimulation can increase protein synthesis in articular cartilage explants
Authors: Macginitie L. A. , Gluzband Y. A. , Grodzinsky A. J. 
Published: February 2005

AbstractIt has been hypothesized that the electric fields associated with the dynamic loading of cartilage may affect its growth, remodeling, and biosynthesis. While the application of exogenous fields has been shown to modulate cartilage biosynthesis, it is not known what range of field magnitudes and frequencies can alter biosynthesis and how they relate to the magnitudes and frequencies of endogenous fields. Such information is necessary to understand and identify mechanisms by which fields may act on cartilage metabolism. In this study, incorporation of 35S‐methionine was used as a marker for electric field‐induced changes in chondrocyte protein synthesis in disks of cartilage from the femoropatellar groove of 1 to 2‐week‐old calves. The cartilage was stimulated sinusoidally at 1, 10, 100, 103 Hz with current densities of 10–30 mA/cm2. Incorporation was assessed in control disks maintained in the absence of applied current at 37, 41, and 43°C. The possibility that applied currents would induce synthesis of the same stress proteins that are caused by heating or other mechanisms was assessed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and examination of gel fluorographs. Total radiolabel incorporation in cartilage that had been stimulated relative to incorporation in the controls increased with current density magnitudes greater than 10 mA/cm2. The increase was greatest at 100 Hz and 1 kHz, and it depended on the position on the joint surface from which the cartilage samples were taken. Together, these results suggest that endogenous electric fields could affect cartilage biosynthesis. Stress proteins were not induced at any current density when the electrodes were electrically connected but chemically isolated from the media by agarose bridges. Stress proteins were observed for disks incubated at temperatures greater than 39°C (no field) and when the stimulating platinum electrodes were in direct contact with the media bathing the cartilage disks. Therefore, the increase in incorporation of 35S‐methionine due to applied fields with the use of chemically isolated electrodes did not appear to be associated with stress response.
Kinematics of the trapeziometacarpal joint after sectioning of ligaments
Authors: Imaeda Toshihiko , Niebur Glen , An Kai‐Nan , Cooney William P. 
Published: February 2005

AbstractThis study was designed to examine the roles of ligaments in the maintenance of the articular kinematics of the trapeziometacarpal joint. Circumduction of the trapeziometacarpal joint was studied in 12 hands from fresh human cadavera. With use of a magnetic tracking system, changes in the motion of the base of the first metacarpal after ligament sectioning were analyzed and compared with those of the normal joint. Two sets of ligaments were sectioned: (a) the anterior oblique and ulnar collateral ligaments and (b) the first intermetacarpal ligament and the ulnar joint capsule. Sectioning of the anterior oblique and ulnar collateral ligaments resulted in a significant dorsal‐ulnar shift in the path of the base of the first metacarpal. However, sectioning of the first intermetacarpal ligament did not affect the movement pattern of the center of the base. The anterior oblique and ulnar collateral ligaments provided constraint of the trapeziometacarpal joint during circumduction of the thumb.
Cortical and trabecular bone contribute strength to the osteopenic distal radius
Authors: Spadaro J. A. , Werner F. W. , Brenner R. A. , Fortino M. D. , Fay L. A. , Edwards W. T. 
Published: February 2005

AbstractFractures of the distal radius are common, especially in postmenopausal women, and their prevalence increases with age. Knowledge of the factors that increase the risk of fracture in this metaphyseal region would have predictive and therapeutic implications. Of particular interest in this study were (a) the relative contributions of cortical and trabecular bone to the strength of the distal radius and (b) the best radiographic features to use as strength indicators. In 21 forearms from fresh cadavera (median age at the time of death, 75 years), single photon absorptiometry and quantitative computed tomography were used to determine bone mineral content (BMC), density (BMC/W), and cross‐sectional properties of the radius at distal and midshaft sites. Mechanical testing of the forearms then was used to determine the ultimate force and energy to cause the type of fracture that might be caused by a fall on the outstretched hand. Twelve of the 17 tested specimens sustained a fracture of the distal radius, and five sustained a fracture of the scaphoid. In the group of fractures of the distal radius, we found the cross‐sectional area and moment of inertia of the cortical shell at the metaphyseal site to be better correlates of strength than the trabecular area and trabecular moment. In contrast, strength correlated much better with trabecular density than with cortical density. Overall, the best correlates of strength were the BMC and BMC/W at either the distal or proximal site. On balance, these results suggest that the thin cortical shell contributes substantially more to the mechanical strength of the distal radius than has been commonly appreciated.
Nonuniform distribution of collagen density in human knee ligaments
Authors: Mommersteeg T. J. A. , Blankevoort L. , Kooloos R. J. G. M. , Hendriks J. C. M. , Kauer J. M. G. , Huiskes R. 
Published: February 2005

AbstractIt is generally recognized that the mechanical properties of soft connective tissues are affected by their structural components. We documented collagen density distributions in human knee ligaments to quantify differences in density within and between these ligaments. In order to explain the variations in mechanical properties within and between different knee ligaments as described in the literature, the distributions of collagen density were correlated with these biomechanical findings. Human knee ligaments were shown to be nonhomogeneous structures with regard to collagen density. The anterior bundles of all ligaments contained significantly more collagen mass per unit of volume than the posterior bundles did. The percentage differences between the anterior and posterior bundles, in relation to the posterior bundles, were about 25% for the anterior cruciate ligament (ACL) and the collateral ligaments and about 10% for the posterior cruciate ligament (PCL). Along the cruciate ligaments, the central segments had higher collagen densities than did segments adjacent to the ligament insertions (ACL 9%, PCL 24%). The collagen density in the ACL was significantly lower than that in the other ligaments. These variations within and between the ligaments correlate well with the variations in mechanical properties described in the literature; however, other structural differences have to be taken into account to fully explain the variations in mechanical properties from the structural components.
Blood flow in the human achilles tendon assessed by laser doppler flowmetry
Authors: Åstroöm Mats , Westlin Nils 
Published: February 2005

AbstractThis study evaluated microvascular perfusion in the human Achilles tendon by laser Doppler flowmetry (LDF) at rest, during vascular occlusion, and during passive stretch and isometric contraction of the triceps surae. In 40 healthy volunteers, an intratendinous needle probe was introduced 5 mm above the distal insertion, at the midportion, and at the musculotendinous junction of both legs. Values were obtained at rest and during temporary vascular occlusion. Twenty‐eight of the subjects also were assessed during physical provocation by passive stretch and isometric contraction of the triceps surae. Blood flow was significantly lower near the calcaneal insertion but otherwise was distributed evenly in the tendon. The output signal showed a pulsatile variation synchronous with heart activity, and temporary vascular occlusion always caused a pronounced reduction in LDF values. Passive stretch and isometric contraction induced a progressive decline in LDF values as tension increased. Hyperemia often appeared after contraction. Tendon blood flow was higher in women and decreased with increasing age.
Chondrocyte cells respond mechanically to compressive loads
Authors: Freeman P. M. , Natarajan R. N. , Kimura J. H. , Andriacchi T. P. 
Published: February 2005

AbstractMany studies have illustrated the effect of mechanical loading on articular cartilage and the corresponding changes in chondrocyte metabolism, yet the mechanism through which the cells respond to loading still is unclear. The purpose of this study was to evaluate the change in shape of chondrocytes under a statically applied uniaxial compressive load. Isolated chondrocytes from rat chondrosarcoma were embedded in 2% agarose gel. Strains of 5, 10, and 15% were applied, and images of the cell were recorded from initial loading to equilibrium (15 minutes). A finite‐element model was used to model the experimental setup and to estimate the mechanical properties of the chondrocyte at equilibrium. The transient behavior of the composite in the experiment was analyzed with use of a standard linear viscoelastic model. We found that all cells decreased in cross‐sectional area under each of the applied compressive strains. In the finite‐element model, the elasticity of the chondrocyte was similar to that of the surrounding agarose gel (4.0 kPa) and had a Poisson's ratio of 0.4. Viscoelastic analysis showed that the chondrocytes contributed a significant viscoelastic component to the behavior of the composite in comparison with the agarose gel alone. If a decrease in cell volume proportional to the decrease in cross‐sectional area is assumed, the decrease observed was greater than would be predicted by a passive cellular response due to an equivalent osmotic pressure. This indicates that the chondrocyte may be altering its intracellular composition by cellular processes in response to mechanical loading.
Effects of lathyritic drugs and lathyritic demineralized bone matrix on induced and sustained osteogenesis
Authors: Di Cesare Paul E. , Nimni Marcel E. , Yazdi Mohamadreza , Cheung David T. 
Published: February 2005

AbstractDemineralized bone matrix was implanted in normal and lathyritic rats. At 2 weeks, the bone that formed in the lathyritic animals had an elevated alkaline phosphatase activity and a reduced calcium content compared with the controls. Four weeks after implantation, these biochemical parameters were reversed, with a decrease in alkaline phosphatase activity and an increase in calcium content to control levels. the histology of the recovered implants revealed new bone formation. Lathyritic demineralized bone matrix was prepared from bones of rats fed β‐aminopropionitrile for 2 weeks (2‐week BAPN‐DBM) or 4 weeks (4‐week BAPN‐DBN), and was implanted in normal rats. Two weeks after implantation, both preparations of lathyritic demineralized bone matrix demonstrated early bone formation, although alkaline phosphatase activity and calcium content were reduced. By 4 weeks after implantation, no biochemical or histological evidence of bone formation remained at the site of the 4‐week BAPN‐DBM implants; continued but reduced bone formation was observed at the site of the 2‐week BAPN‐DBM implants. Reconstitution of inactivated normal demineralized bone matrix with the guanidine‐soluble extracts restored the osteoinductive capacity. However, reconsistution of inactivated lathyritic demineralized bone matrix (4‐week BAPN‐DBM) failed to restore the osteoinductive capacity. These results indicate that the degree of crosslinking of the collagen matrix that acts as a carrier for osteoinductive proteins plays a key role in inducing and sustaining osteogenesis.
Mechanical and biochemical changes in the superficial zone of articular cartilage in canine experimental osteoarthritis
Authors: Guilak Farshid , Ratcliffe Anthony , Lane Nancy , Rosenwasser Melvin P. , Mow Van C. 
Published: February 2005

AbstractThe changes in the tensile mechanical properties and biochemical composition of the superficial zone of articular cartilage were examined in a canine model of early osteoarthritis generated by transection of the anterior cruciate ligament. Sixteen weeks following ligament transection, the tensile stiffness of the articular cartilage was decreased by 44% and the ion‐induced stress relaxation of the tissue was increased by 57% compared with the contralateral control. Biochemical analyses indicated that the water content of the experimental tissue was increased by 13%, which was reflected as an apparent 37% decrease in the proteoglycan content and a 36% decrease in the collagen content (expressed per wet weight). The hydroxypyridinium crosslink density was decreased in the experimental tissue by 11%. A significant negative correlation was found between the ion‐induced stress relaxation and the hydroxypyridinium crosslink density in both control tissue (R = −0.56) and experimental tissue (R = −0.70). No correlation was noted between the tensile stiffness and the biochemical composition of the tissue. These results suggest that, in the superficial zone of articular cartilage, the structure of the tissue may play a more important role than the composition in the determination of its mechanical properties. A major event observed in the model of early osteoarthritis appears to be the disruption and remodeling of the collagen network in the superficial zone of the articular cartilage.
Chondrocyte‐fibrin matrix transplants for resurfacing extensive articular cartilage defects
Authors: Hendrickson Dean A. , Nixon Alan J. , Grande Daniel A. , Todhunter Rory J. , Minor Ronald M. , Erb Hollis , Lust George 
Published: February 2005

AbstractCartilage resurfacing by chondrocyte implantation, with fibrin used as a vehicle, was examined in large (12 mm) full‐thickness articular cartilage defects in horses. Articular chondrocytes, isolated from a 9‐day‐old foal, were mixed with fibrinogen and injected with thrombin, in a 1:1 mixture, into 12 mm circular defects on the lateral trochlea of the distal femur of eight normal horses. The contralateral femoropatellar (knee) joint served as a control in which the defect was left empty. Synovial fluid from the femoropatellar joints was sampled on days 0, 4, 7, 30, 120, and 240 postoperatively. Groups of four horses were killed at 4 or 8 months postoperatively, and the repair tissue was evaluated by gross and histologic examination with use of hematoxylin and eosin and safranin O staining and by autoradiography. Biochemical analyses included quantitation of proteoglycan, total collagen, and type‐II collagen in the repair tissue. Grossly, grafted defects had improved filling of the cartilage lesions: histologically, these areas consisted of differentiated chondrocytes in the deep and middle zones. The cellular arrangement in these zones resembled that of hyaline cartilage. The control defects contained poorly attached fibrous tissue throughout. Grafted tissue at 8 months had increased proteoglycan synthesis evident by both safranin O staining and autoradiography. Glycosaminoglycan quantitation by dye‐binding assay confirmed a significantly elevated glycosaminoglycan content in grafted defects (58.8 μg/mg of dry weight) compared with control defects (27.4 μg/mg; p < 0.05). Similarly, the levels of chondroitin sulfate/dermatan sulfate was significantly elevated in the grafted defects, and this was the predominant glycosaminoglycan epitope present. There was a statistically significant (p < 0.05) increase in type‐II collagen in the grafted tissue at 8 months (61.2% grafted; 25.1% control). This resurfacing attempt with use of allograft chondrocytes, secured in large full‐thickness articular defects with polymerized fibrin, resulted in an improved cartilage surface in comparison with the control defects, a significantly greater aggrecan level, and a significantly higher proportion of type‐II collagen.
Infection at the site of implanted materials with and without preadhered bacteria
Authors: Chang C. C. , Merritt K. 
Published: February 2005

AbstractA study was undertaken to examine the role of bacterial adherence in the development of infection at the site of an implant. The amount of in vitro adherence of Staphylococcus epidermidis was greatest for stainless steel, followed by polymethylmethacrylate and commercially pure titanium, and was least for polymethylmethacrylate with gentamicin. These materials then were preincubated with S. epidermidis and implanted. The number of organisms that were isolated and the rate of infection followed the same pattern as that in the in vitro studies. Materials that were not preincubated with bacteria also were implanted and bacteria were injected into the site. The number of organisms isolated from the site and the rate of infection were lower than those for the preincubated materials, but the trend was the same as in both the in vitro and the in vivo studies. The rates of infection and colonization correlated with the propensity for the organisms to adhere to a given material. Materials colonized with S. epidermidis at the time of implantation caused a high rate of infection. The ability of organisms to adhere to a material in vitro is correlated with their propensity to cause biomaterial‐based infection.