bluuebunny/crossref_metadata_2025_split huggingface dataset:
Histological and biochemical analysis of the fibrous tissue induced by implantation of synthetic ligament (Dacron): An experimental study in a rat model
Authors: Irie Kazunori , Kurosawa Hisashi , Oda Hiromi 
Published: February 2005

AbstractWe conducted a comparative study to evaluate the quality and true nature of the fibrous tissue formed around synthetic grafts when used in ligament replacement. In one group of Lewis rats, a patellar ligament was replaced with a Dacron prosthesis; the comparison group received a tail tendon isograft. Two‐, 4‐, 8‐, 12‐, and 24‐week comparisons showed histological and biochemical changes in the Dacron group alone that were consistent with foreign‐body reaction. Specifically, the Dacron group showed infiltration by large numbers of macrophages and foreign‐body, multinucleated giant cells. In addition, the capsule of fibrous tissue that developed around the Dacron ligaments was characterized by lower collagen solubility, a higher content of noncollagenous protein, and a higher proportion of type III collagen than that comprising the isografted tendons. The results of this study call into question the suitability of synthetics for ligament replacement.
Ultrastructural changes of articular cartilage chondrocytes associated with freeze‐thawing
Authors: Tavakol K. , Miller R. G. , Bazett‐Jones D. P. , Hwang W. S. , McGann L. E. , Schachar N. S. 
Published: February 2005

AbstractIn an attempt to justify the use of cryopreserved versus fresh articular cartilage (AC) allografts, we used transmission electron microscopy (TEM) to study the ultrastructure of fresh versus frozen‐thawed AC with or without a dimethyl sulfoxide (DMSO) treatment. AC explants were cut aseptically from the femoral condyles of healthy, mature rabbits when they were killed. Half of all explants were incubated in Ham's F‐12 medium, supplemented with antibiotics and with or without 7.5% DMSO, frozen to −80°C, stored for 24 h, and thawed rapidly. These, and the control explants, were fixed with glutaraldehyde, paraformaldehyde, and acrolein in cacodylate buffer. Sections were stained for acid phosphatase (APase), postfixed with osmium, embedded, and examined under TEM. The typical organization of the matrix and the cells was noted in control sections. The chondrocytes contained intact nuclei, organelles, and discrete plasma membrane. Although some endoplasmic reticula and nuclear membrane appeared intact, distinct ultrastructural changes were observed in frozen‐thawed samples treated with DMSO. These changes included condensation of chromatin, large lipid droplets, partly disrupted plasma membrane, and pericellular precipitation of APase‐positive crystalites. In sections not treated with DMSO, the cytoplasm was extensively vacuolated and no distinct organelies could be detected in the chondrocytes. Little difference was noted between the matrix organization of fresh or frozen‐thawed samples. Our results suggest that distinct ultrastructural changes occur in the chondrocytes following freeze‐thawing of intact AC and that DMSO pretreatment may contribute to improvement in the cryopreservation of AC.
Physeal replacement with cultured chondrocytes of varying developmental time: Failure to reconstruct a functional or structural physis
Authors: Barr Stephen J. , Zaleske David J. , Mankin Henry J. 
Published: February 2005

AbstractReconstruction of physeal regions excised from the distal femoral chondroepiphysis was attempted in a murine model. Cultured chondrocytes of varying developmental time from the same inbred strain of mice were used for replacement. Vascularity, matrix formation, and cell division, as well as growth, were assessed. The cultured chondrocytes did not produce growth. Consistent with this, cell division, as assessed with incorporation of tritiated thymidine, was not normal. However, the cultured chondrocytes did receive a nutritional supply from the host and did continue matrix formation after transplantation.
Maintenance of set force in anterior cruciate ligament grafts
Authors: Stewart Nathaniel J. , Engebretsen Lars , Lewis Jack L. , Lindquist Conrad , Lew William D. 
Published: February 2005

AbstractThis study was undertaken to determine how accurately total graft force and load‐sharing between graft segments could be set and maintained during augmented anterior cruciate ligament (ACL) reconstruction in the goat knee. Special procedures were developed to reduce the effect of tissue creep and to overcome difficulties in the setting of graft force. Five knees from goat cadavers were reconstructed using a bone‐tendon‐bone graft (PT) and a synthetic augmentation device (LAD). Prescribed levels of total graft force and load‐sharing between the autograft and LAD were set under a standardized external joint load. Immediately after fixation, the set force declined an average of 9 and 3% in the LAD and PT, respectively. After three subsequent exercise sequences, the set forces fell from their initial level by an average of 25% for the LAD and 28% for the PT. An analysis of variance did not show the loss of force with exercise to be statistically significant. We conclude from this in vitro study that our method can be used to set forces in an ACL reconstruction with reasonable maintenance of load‐sharing but that losses of approximately 30% of total graft force after exercise of the reconstructed joint are to be expected.
Load transfer with the austin moore cementless hip prosthesis
Authors: Keaveny Tony M. , Bartel Donald L. 
Published: February 2005

AbstractMore than 1,300 Austin Moore hemiarthroplasties have been reviewed in the literature, with no reports of fracture of the stem. Many patients with these hip implants had good function. The lack of stem fractures in patients with good function has not been explained and contrasts with stem fractures that have occurred in patients with cemented prostheses of other designs during the same time. We used three‐dimensional finite‐element analysis and free‐body diagrams to explain the lack of fractures for this device by a description of the probable load‐transfer mechanisms between the prosthesis and the bone. Results from our finite‐element analysis indicate that, with good calcar‐collar support, the stresses in the stem are small because the stem portion of the prosthesis and the bone are uncoupled and, consequently, do not share the resultant bending moment of the head and abductor forces. If the stem is coupled to the bone so that the resultant bending moment is shared, high stresses in the stem are predicted; such stresses are inconsistent with the complete absence of fractures of these prostheses. The results of the finite‐element analysis further showed that loss of calcar‐collar support with proximal fixation through the fenestrations resulted in high stresses in the stem and stress shielding of the proximal medial cortex. The uncoupled prosthesis also may be modeled with a free‐body diagram as a three‐force member loaded at the head, stem tip, and in the proximal region. With this model, it can be shown that the reaction force of the stem tip, and thus the peak bending stress in the stem, increases as calcar‐collar support is decreased. If there is no calcar‐collar support, proximal support must be provided by some combination of integration of bone in the fenestrations and wedging due to the lateral‐medial taper of the device. Stresses in the stem are largest when there is no wedging, but high stresses develop in the cancellous bone in the fenestrations. When there is wedging, stresses in the stem can be low, but stresses in the supporting cancellous bone can be high; additional proximal support through the fenestrations substantially reduces these bone stresses. If reduced stresses in the cancellous bone are indicative of a stable device, these mechanisms indicate that fractures of the Austin Moore prosthesis have not occurred in normally loaded hips because load was transferred primarily either through the collar or by wedging, with additional support at the fenestrations.
Healing of cancellous bone osteotomy in rabbits—Part I: Regulation of bone volume and the regional acceleratory phenomenon in normal bone
Authors: Bogoch E. , Gschwend N. , Rahn B. , Moran E. , Perren S. 
Published: February 2005

AbstractWe performed a simple, undisplaced, incomplete osteotomy of the distal medial condyle of mature New Zealand White rabbits and permitted healing without fixation for 4 weeks. During the recovery period, the rabbits received the bone label calcein in their drinking water. From ground stained and unstained sections, we determined histomorphometric parameters in five zones: osteotomy gap, juxtaosteotomy, lateral condyle, metaphysis, and diaphysis. At 4 weeks, newly formed cancellous bone had obliterated the osteotomy gap. Osteotomy also stimulated new bone formation in cancellous bone of the medial condyle around the osteotomy. At that site, we found a fivefold increase in new bone without a change in bone volume (BV). Stimulation of bone formation was not observed in cancellous bone of the lateral concyle that had not been operated on or in cortical bone of the metaphysis or diaphysis. The maintenance of BV, despite increased new bone formation in the osteotomized medial femoral condyle, was probably due to a local acceleration of bone remodeling.
Muscle contraction increases the structural capacity of the lower leg: An in vivo study in the rat
Authors: Nordsletten Lars , Ekeland Arne 
Published: February 2005

AbstractA model to study the contribution of muscle contraction to the structural capacity of the rat tibia was developed. The right lower leg was tested to failure in three‐point ventral bending during electrically stimulated muscle contraction. The left lower leg was tested without stimulation, as a control. The mean ultimate bending moment for the stimulated legs was 0.603 Nm, compared with 0.492 Nm for the unstimulated legs (p ≤ 0.001). The ultimate energy absorption was 0.313 and 0.188 J in the stimulated and unstimulated legs, respectively (p ≤ 0.01). Fracture strength has been studied nearly exclusively in dissected bone stripped of all soft tissues. The present investigation suggests that studies of dissected bone are incomplete compared with the in vivo situation, as contraction of the muscles substantially increased the fracture strength of the lower leg in rats.
An experimental canine model of osteonecrosis: Characterization of the repair process
Authors: Malizos Konstantinos N. , Quarles L. Darryl , Seaber Anthony V. , Rizk Wagdy S. , Urbaniak James R. 
Published: February 2005

AbstractOsteonecrosis of the femoral head was induced in dogs by a process of deep freezing, accompanied by stripping of the soft‐tissue attachments from the femoral neck and intertrochanteric area, in an effort to develop an experimental model to study treatment modalities for avascular necrosis of the hip. Immediate uniform necrosis was created in a defined area. Thereafter, spontaneous healing originated mainly from the adjacent viable bone by migration of undifferentiated mesenchymal tissue into the necrotic bone, genesis of fibrosis, and, finally, formation of new bone. Osteogenesis occurred primarily through intramembranous ossification without a preexisting template. Quantitative measurements showed a difference in the rates of ingrowth and revascularization of the necrotic area during the fibrotic and osteogenic phases of the healing. The de novo osteogenesis was slower than the migration of fibrosis. These findings indicate that, without osteotomy, we can reproducibly create necrosis of bone in a defined area of the proximal femur and induce a reparative process that incompletely heals the defect. Although it does not fully simulate the human disorder of osteonecrosis, our experimental surgical model provides a basis for further laboratory investigation into the management of avascular necrosis of the femoral head.
Sequential appearance of macromolecules in bone induction in the rat
Authors: Hulth Anders , Johnell Olov , Lindberg Lisbeth , Heinegård Dick 
Published: February 2005

AbstractThe appearance of noncollagenous proteins and proteoglycans during induction of cartilage and bone by implanted demineralized bone powder was studied by immunohistochemistry with polyclonal antibodies. Three bone proteins (osteopontin, sialoprotein, and a 62 kDa protein) were present in the bone powder grains before implantation. They appeared to be lost slowly from the granulation tissue but reappeared when bone formation started. The raw powder also contained a cartilage protein, biglycan (S1), chondrocalcin, cartilage oligomeric matrix protein, and the large proteoglycan aggrecan. The amounts of these molecules, however, increased significantly both within and outside the grains on cartilage formation. Cartilage matrix protein (148 kDa protein) appeared sparsely. The 58 kDa protein and fibromodulin (59 kDa protein), particularly the latter, were prevalent in fibrillar bundles. Antibodies against the laminin‐staining vessel basement membranes showed an abundant occurrence of capillaries within the matrix grains in the granulation tissue and in the precartilaginous tissue. Bone powder made noninductive by 4 M guanidine HCl did not induce cartilage and did not stain for antibodies against bone proteins or for molecules restricted to cartilage.
Evaluation of biodegradable cefazolin sodium microspheres for the prevention of infection in rabbits with experimental open tibial fractures stabilized with internal fixation
Authors: Jacob Elliot , Cierny George , Fallon Michael T. , McNeill James F. , Siderys George S. 
Published: February 2005

AbstractImmediate internal fixation of severe open tibial fractures usually is contraindicated due to the high risk of infection. The objective of this study was to evaluate the efficacy of local antibiotic therapy with biodegradable poly‐(DL‐lactide‐co‐glycolide) cefazolin‐loaded microspheres for the prevention of infection in experimental open fractures stabilized with internal fixation. Rabbits with experimental tibial fractures that were contaminated with Staphylococcus aureus were treated with local application of cefazolin microspheres, an equivalent local dose of free Ancef powder, or systemic Ancef therapy. The bones then were fixed with a four‐hole plate, and the animals were observed for 8 weeks. Clinically, deep infection was present in 86% of control animals that received no antibiotics and in 60% of animals that received a 7 day course of systemic Ancef therapy. In contrast, no infections were noted among any of the surviving rabbits that received local therapy with either cefazolin microspheres or free Ancef powder. Significantly higher levels of serum cefazolin were measured at 1 h for animals treated with free Ancef powder (18.7 ± 6.1 μg/ml) than for those treated with cefazolin microspheres (0.57 ± 0.27 μg/ml). Follow‐up studies are in progress to evaluate further the potential clinical benefits of local antibiotic therapy for the management of contaminated open fractures in humans.
Dual energy x‐ray absorptiometry of implanted femora after cemented and press‐fit total hip arthroplasty in a canine model
Authors: Markel Mark D. , Gottsauner‐Wolf F. , Bogdanske John J. , Wahner Heinz W. , Chao Edmund Y. S. 
Published: February 2005

AbstractThe effect of a press‐fit and cemented titanium alloy endoprosthesis on the measurement of bone mineral density (BMD) of the proximal femur in a canine model with dual energy x‐ray absorptiometry (DXA) was determined. Seven regions of interest, corresponding to zones 1–7 according to Gruen et al., were measured. Eight unpaired femora were scanned with DXA before implantation (five separate scans per femur), after press‐fitting with a titanium alloy femoral component (five separate scans per femur); and after cementing with the same component (five separate scans per femur). When the titanium alloy endoprosthesis was press‐fit, the BMD of five of seven regions of the proximal femur increased significantly (range, 2.7–23.1%; mean, 11.2%), although the mean precision error of this measurement was not altered (before implantation, 1.1%; after press‐fit 1.8%). Cementing of the implant caused a variable effect on BMD, resulting in a decrease in distal regions where cortical bone was relatively thin compared with the cement mantle (regions 3, 4, and 5) and in an increase in the other regions. Cementing of the implant significantly increased the mean precision error of measurement to 7.2% (range, 1.1–12.6%).
Rib cage deformities in scoliosis: Spine morphology, rib cage stiffness, and tomography imaging
Authors: Closkey Robert F. , Schultz Albert B. 
Published: February 2005

AbstractA computer‐implemented biomechanical model of a thoracolumbar spine and deformable rib cage was used to investigate the influence of spine morphology and rib cage stiffness properties on the rib cage deformities that arise from scoliosis and to study the relationship of actual rib distortions with those seen on computed tomography (CT) scans. For the purposes of this study, it was assumed that rib cage deformities result from forces imposed on the ribs by the deforming spine. When a structurally normal rib cage was allowed to follow freely the imposition of scoliotic curves on the spine, different configurations of scoliosis led to substantial differences in the resulting rib cage deformities. Rib cage lateral offset correlated well with the Cobb angle of the scoliosis but not with the apical vertebral axial rotation, whereas rib cage axial rotation correlated well with apical vertebral axial rotation but not with the Cobb angle. These model‐obtained findings mirror clinical findings that correction of the Cobb angle leads to correction of the lateral offset of the rib cage but does not correlate well with correction of the rib cage axial rotation. The stiffnesses of the ligamentous tissue connecting the sternum to the pelvis, of the costovertebral joints, and of the ribs themselves also influenced the rib deformities substantially. The influence of the sternopelvic ligamentous ties has not been recognized previously. The total rib cage volume remained essentially constant regardless of the severity of the resulting deformity, but the distribution of this volume between convex and concave sides varied somewhat. Simulated CT scans of model rib cages suggested that distortions of individual ribs are substantially exaggerated in such images.
Viscoelastic shear properties of articular cartilage and the effects of glycosidase treatments
Authors: Zhu Wenbo , Mow Van C. , Koob Thomas J. , Eyre David R. 
Published: February 2005

AbstractThe objectives of this study were to determine the viscoelastic shear properties of articular cartilage and to investigate the effects of the alteration of proteoglycan structure on these shear properties. Glycosidase treatments (chondroitinase ABC and Streptomyces hyaluronidase) were used to alter the proteoglycan structure and content of the tissue. The dynamic viscoelastic shear properties of control and treated tissues were measured and statistically compared. Specifically, cylindrical bovine cartilage specimens were subjected to oscillatory shear deformation of small amplitude (γo = 0.001 radian) over a physiological range of frequencies (0.01–20 Hz) and at various compressive strains (5, 9, 12, and 16%). The dynamic complex shear modulus was calculated from the measurements. The experimental results show that the solid matrix of normal articular cartilage exhibits intrinsic viscoelastic properties in shear over the range of frequencies tested. These viscoelastic shear properties were found to be dependent on compressive strains. Our data also provide significant insights into the structure‐function relationships for articular cartilage. Significant correlations were found between the material properties (the magnitude of dynamic shear modulus, the phase shift angle, and the equilibrium compressive modulus), and the biochemical compositions of the cartilage (collagen, proteoglycan, and water contents). The shear modulus was greatly reduced when the proteoglycans were degraded by either chondroitinase ABC or Streptomyces hyaluronidase. The results suggest that the ability of collagen to resist tension elastically provides the stiffness of the cartilage matrix in shear and its elastic energy storage capability. Proteoglycans enmeshed in the collagen matrix inflate the collagen network and induce a tensile prestress in the collagen fibrils. This interaction of the collagen and proteoglycan within the cartilage matrix provides the complex mechanism that allows the tissue to resist shear deformation.
Response of peripheral nerve to cyclic compression in a laboratory rat model
Authors: Szabo R. M. , Sharkey N. A. 
Published: February 2005

AbstractRepetitive cyclic loading of a nerve has been proposed as a pathogenic factor in the development of occupational compression neuropathies. Little is known about the basic response of peripheral nerve to cyclic compression. We investigated the hypothesis that cyclic compression is more detrimental to nerve function than constant compression. We measured the amplitudes and velocities of distally evoked action potentials in the presence of constant or cyclic compression of the tibial nerve in rats. Seven groups were subjected to constant or cyclic compression for 6 h by a computer controlled, hydraulically activated compression chamber. Nerves were compressed with 0 (control group), 30, 60, or 90 mm Hg of constant pressure or 0–30, 20–50, or 30–60 mm Hg of cyclic compression for ∼20,000 compression cycles. Action potentials were recorded every 15 min. The effects of cyclic compression on nerve conduction were equivalent to the effects of constant compression at the average applied pressure. Cyclic loading itself does not appear to be an important pathogenic factor in the development of nerve conduction block.
Reduction of fretting corrosion of Ti‐6Al‐4V by various surface treatments
Authors: Maurer Anne M. , Brown Stanley A. , Payer Joe H. , Merritt Katharine , Kawalec Jill S. 
Published: February 2005

AbstractTitanium and titanium‐6% aluminum‐4% vanadium (Ti‐6Al‐4V) are known to be biocompatible and corrosion resistant. However, there have been numerous reports of elevated tissue levels of titanium due to passive dissolution, wear, or fretting corrosion of implants. Studies were undertaken to determine whether the fretting corrosion of Ti‐6Al‐4V could be reduced by surface treatment of one or both surfaces in a fretting situation. Three different surface treatments were studied: ion implantation, physical vapor deposition nitriding, and plasma ion nitriding. The specimens used were screws fretting against the countersinks of a two‐hole plate. Fretting corrosion was assessed by weight loss, by chemical analysis of test solutions, and by scanning electron microscopy. Surface treatment of one component, the screws, resulted in reduction in the release of titanium to only 18–32% of that seen with the untreated controls. Weight loss of the untreated plates fretted against physical vapor deposition nitrided screws and plasma ion nitrided screws was reduced to 31 and 38% of the control, respectively. The weight loss of plasma nitrided screws was only 30% that of the control. Nitriding of both plates and screws resulted in a further decrease in plate weight loss and metal release. Plasma ion nitriding of both components had the most significant effect, with the weight loss and titanium release being only 11 and 2% of the control values, respectively.