bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vascular and structural changes in rat femora following nailing and intramedullary occlusion
Authors: Grundnes Oliver , Gjerdet Nils R. , Utvåg Stein Erik , Reikerås Olav 
Published: February 2005

AbstractThe purpose of this study was to evaluate biomechanical, structural, and blood flow changes of the femoral canal in rats 12 weeks after intramedullary reaming, nailing, or occlusion. In one group, reaming alone was performed. In a second group, reaming was followed by use of a tight‐fit steel nail. In a third group, reaming was followed by use of inert silicone that totally plugged the medullary cavity. A fourth group served as the control. The acute mechanical and vascular effects caused by reaming and nailing were determined in a separate group. Reaming and nail insertion reduced blood flow in femoral bone to about one‐third. Reaming reduced bending moment by approximately 40%, whereas bending rigidity was unchanged. After 12 weeks, the cortical bone blood flow was significantly increased in both the nailed and the silicone‐plugged bones compared with the reamed and control groups. The bending moment and energy absorption in the silicone group were inferior to those of the other groups. There were no differences in either the external or internal diameter or the medullary and net bone areas. In the silicone group, both the number and the area of large pores (larger than 10 μm) significantly increased in comparison with the other groups; hence, bone porosity was increased. This increment was confined to large pores. It is concluded that medullary occlusion contributes to structural and blood flow changes in bone.
Regional gene therapy with a BMP‐2‐producing murine stromal cell line induces heterotopic and orthotopic bone formation in rodents
Authors: Lieberman Jay R. , Le Lu Q. , Wu Lilly , Finerman Gerald A. M. , Berk Arnie , Witte Owen N. , Stevenson Sharon 
Published: February 2005

AbstractThe ability to continuously deliver osteoinductive proteins to a specific anatomic site would facilitate the treatment of fracture nonunions and other clinical problems associated with bone loss. We have developed a murine model of regional gene therapy. A bone‐marrow stromal cell line infected with an adenovirus expressing recombinant bone morphogenetic protein‐2 cDNA secreted biologically active bone morphogenetic protein‐2. These bone morphogenetic protein‐2‐producing cells were able to induce abundant heterotopic bone formation when implanted into the quadriceps muscle of severe combined immune deficient mice and also successfully healed large segmental femoral defects in nude rats. These studies demonstrate that regional gene therapy with continuous delivery of osteoinductive factors to a specific anatomic site can enhance the formation and repair of bone.
Pre‐yield and post‐yield shear behavior of the cement‐bone interface
Authors: Mann Kenneth A. , Allen Matthew J. , Ayers David C. 
Published: February 2005

AbstractAseptic loosening of cemented total hip replacements is thought to involve mechanical failure of the cement‐bone interface. However, the mechanical response of the interface, particularly the post‐yield, behavior, is not well understood. The purpose of this study was to determine the constitutive behavior of the cement‐bone interface for loading in shear using a combination of experimental and finite element methods. A total of 55 cement‐bone specimens (5 × 10 × 15‐20 mm) from the proximal femur of human cadavers were loaded to failure under displacement control with use of a custom shear test jig. Finite element models of the test specimens were made and included provision for a two‐parameter nonlinear interface model at the cement‐bone interface. The experimental tests revealed a complicated load versus displacement response with an initial linear region and a reduction in slope until the ultimate strength (2.25 ± 1.49 MPa) was reached, followed by an exponential decrease in load with increasing displacement until the entire interface debonded. Failure most often occurred at the cement‐bone interface, where the cement penetraed into the bone with bone remaining in the cement in 30 specimens and with bone remaining in the cement and cement spicules remaining in the bone in 22 specimens. The adjacent bulk bone and cement did not appear, to permanently deformed. Finite element models of the test specimens revealed that failure initiated at the base of the test specimen before the peak load had been reached. The two interface parameters, interface strength (2.71 ± 1.90 MPa) and interface‐softening exponent (4.96 ± 3.47 1/mm), could be determined directly from the experimental data and provided a good fit with the experimental structural response for a wide range of interface strengths. These results show that the cement‐bone interface does not fail abruptly when the shean strength is reached but absorbs a substantial amount of energy with post‐yield strain‐softening behavior.
Effect of static compression on proteoglycan biosynthesis by chondrocytes transplanted to articular cartilage in vitro
Authors: Chen Albert C. , Sah Robert L. 
Published: February 2005

AbstractTransplantation of chondrocytes by injection or within carrier matrices has shown promise for augmenting the repair of articular cartilage defects. In vivo, transplanted chondrocytes are exposed to mechanical forces. This in vitro study examined the effect of a step application of compressive load to chondrocytes after the cells had been seeded onto a cartilage surface. Bovine chondrocytes were transplanted onto bovine cartilage disks, allowed to attach for 1 hour or 4 days, and subjected to compression through overlying cartilage disks in a confined compression configuration. Before use, the disks were lyophilized to lyse the endogenous chondrocytes and thereby allow assessment of the metabolic activity of the transplanted cells. During a 16‐hour application of compressive stress of 0‐24‐0.72 MPa, proteoglycan synthesis, assessed as [35S]sulfate incorporation into macromolecules. was inhibited by approximately 68% after the 1‐hour attachment and by approximately 45% after the 4‐day attachment. Cell retention after the application of load was assessed by use of [3H]thymidine‐tagged chondrocytes and quantitation of the displacement of radioactivity. After the 1‐hour seeding period, loading induced a dose‐dependent dislodgment of [3H]radioactivity (as much as 35%) from the tissue bilayer. In contrast, after the 4‐day seeding period, there was no detectable effect of loading on chondrocyte dislodgment with an 8–12% release of radioactivity. The inhibitory effect of a 16‐hour compression of 0.48 MPa applied after the 4‐day seeding period was studied further. This protocol did not appear to have an irreversible effect on chondrocyte metabolism; at 2 days after the release of load, proteoglycan synthesis by the loaded cells was stimulated by 41% compared with transplanted cells that were not subjected to loading. These results suggest that the application of static compressive stress to chondrocytes at a cartilage surface may affect biosynthesis by these cells and thus subsequent integrative cartilage repair. Such an effect may have implications for optimization of the tightness of the press fit of a cell‐laden cartilaginous construct into an articular defect.
Prediction of long‐term polyethylene wear in total hip arthroplasty, based on early wear measurements made using digital image analysis
Authors: Pedersen Douglas R. , Brown Thomas D. , Hillis Stephen L. , Callaghan John J 
Published: February 2005

AbstractThe capability to reliably predict long‐term in vivo wear of polyethylene would be of great value for the early identification of problematic total hip designs. Formal quantitative estimates of long‐term polyethylene wear were made from a series of 197 patients who had a total hip arthroplasty and who were followed for a minimum of 10 years; the estimates were based on the wear that was apparent radiographically at nominally 2 years after the operation. A newly developed digital image‐analysis edge‐detection procedure was applied to 1,237 archived follow‐up radiographs. The edge‐detection measurements were analyzed with a robust regression random‐coefficients statistical formulation developed especially to address the distributions of wear rate observed across this population over time. Formal regression equations were reported, which can be used to estimate late‐wear depth for a patient radiographed at a 2‐year follow‐up visit. Series wide, the correlation between predicted and observed wear depths was 0.73 at 4 years, with a correlation decline of approximately 0.03 per additional year.
Bone ingrowth to implant surfaces in an inflammatory arthritis model
Authors: An Yuehuei H. , Friedman Richard J. , Jiang Ming , LaBreck Jacqueline C. , Draughn Robert A. , Butehorn Henry F. , Bauer Thomas W. 
Published: February 2005

AbstractMany studies have shown enhanced bone apposition to implants coated with hydroxyapatite, but the optimum implant texture, especially in abnormal trabecular bone, is unclean The purpose of this project was to evaluate the histological and mechanical properties of cylindrical implants with three different surface textures that were placed in the cancellous bone of the distal femur of the rabbit after the production of an inflammatory knee arthritis. The three implant surfaces included a beaded surface (Group A), a beaded surface coated with hydroxyapatite (Group B), and a smooth surface coated with hydroxyapatite (Group C). The right knees of 36 rabbits were injected with carrageenan twice a week for 2 weeks. Then bilateral implantations were performed, with 12 rabbits in each group receiving identical implants in the right and left knees. The rabbits were killed 6 weeks after surgery. Mechanical (push‐out test) and histomorphometric analyses were performed to determine the quality and quantity of bone ingrowth. In Group A, there was virtually no direct contact (a 20–60‐μm clearance) between the bone and the beaded surfaces. Direct contact between the bone and the implant surfaces was seen in Groups B and C. The thickness and number of trabeculae were smaller on the arthritic side than on the control side for all groups but were not different between groups for either the control or the arthritic side. Mechanical testing showed that the shear strength of the interface was weaker on the arthritic side in all groups. The results suggest that inflammatory arthritis induced by carrageenan may influence the quality of local bone (osteopenic changes) and hence compromise the bone apposition and mechanical stability of the interface between the implant and bone.
Identification of sex hormone receptors in human and rabbit ligaments of the knee by reverse transcription‐polymerase chain reaction: Evidence that receptors are present in tissue from both male and female subjects
Authors: Sciore Paul , Frank Cyril B. , Hart David A. 
Published: February 2005

AbstractGender‐related factors have been attributed to observed differences in the rate of injury to ligaments (e.g., anterior cruciate ligament) between male and female subjects. These differences may be a result of unique regulatory mechanisms within the tissue in response to the sex hormones estrogen and progesterone. These hormones, when bound to specific intracellular receptors (estrogen receptor and progesterone receptor, respectively), modulate gene expression within hormone‐responsive tissue. The purpose of this study was to evaluate the expression of the estrogen and progesterone receptors in ligament tissue from male and female rabbits and humans by the sensitive molecular technique of reverse transcription‐polymerase chain reaction. Total RNA was extracted from human anterior cruciate ligament tissue and from medial cruciate ligament, anterior cruciate ligament, patellar tendon, and synovium tissue of the New Zealand White rabbit by the newly developed TRIspin method. The total RNA was reverse transcribed and analyzed by polymerase chain reaction to assess the expression of estrogen and progesterone receptors. Our results demonstrate that estrogen and progesterone receptor transcripts are expressed in ligament tissue of male and female rabbits and humans and that alterations in receptor expression occur in ligaments during pregnancy. In the human samples, only a small percentage of the estrogen receptor appeared to be a nonfunctional mRNA splice variant, and the predominant form contained the estrogen‐binding domain.
Effect of 25‐OH‐vitamin D on fracture healing in elderly rats
Authors: Delgado‐Martínez A. D. , Martínez M. E. , Carrascal M. T. , Rodríguez‐Avial M. , Munuera L. 
Published: February 2005

AbstractTo investigate the effect of 25‐OH‐vitamin D supplements (calcidiol) on fracture healing in the elderly, an experimental model with 15 18‐month‐old female Wistar rats was designed. An experimental fracture in the middle third of both femora of each rat was made. Then the rats were randomly assigned to two groups: one group was subcutaneously treated with 25‐OH‐vitamin D during all healing processes, and the other group (the control group) was not. After 5 weeks of healing, the animals were killed and both femora were extracted. Blood samples were collected before fracture and at death to determine the levels of 25‐OH‐vitamin D. All bones that were extracted were subjected to a torsion test to assess healing; a significantly greater maximum shear force before failure was supported in the treated group (p < 0.01). Moreover, a positive correlation (p < 0.01; r = 0.55) was found between blood levels of 25‐OH‐vitamin D at death and the mechanical strength of the callus. Thus, the administration of 25‐OH‐vitamin D after the experimental fracture significantly improved the mechanical strength of the fractured bone. If similar results are found in the human, then treatment with 25‐OH‐vitamin D after the occurrence of a fracture would be a good way to improve fracture healing in the elderly.
Single local injection of recombinant fibroblast growth factor‐2 stimulates healing of segmental bone defects in rabbits
Authors: Kato Takashi , Kawaguchi Hiroshi , Hanada Keigo , Aoyama Ikuo , Hiyama Yoshiyuki , Nakamura Toshiyuki , Kuzutani Kazuya , Tamura Makoto , Kurokawa Takahide , Nakamura Kozo 
Published: February 2005

AbstractThe effects of a single local injection of recombinant human fibroblast growth factor‐2 on the healing of segmental bone defects were evaluated in rabbits. One month after the external fixator originally designed for this experiment was installed in the tibia of the rabbit, a 3‐mm bone defect was created by an osteotomy in the middle of the tibia and 0, 50, 100, 200, or 400 μg of fibroblast growth factor‐2 in 100 μg of saline solution was injected into the defect. Injection of the growth factor increased the volume and mineral content of newly made bone at the defect in a dose‐dependent manner with significant effects at Concentrations of 100 μg or greater. These significant effects were observed at 5 weeks and later. One hundred micro‐grams of the growth factor increased the volume and mineral content of newly made bone by 95 and 36%, respectively, at 5 weeks. These results indicate that a single local injection of fibroblast growth factor‐2 stimulates the healing of segmental defects. We speculate that such an injection could be clinically useful for the healing of fractures even when the fracture gap is rather large.
Adhesion and reliability of interfaces in cemented total joint arthroplasties
Authors: Ohashi K. L. , Romero A. C. , McGowan P. D. , Maloney W. J. , Dauskardt R. H. 
Published: February 2005

AbstractDebonding of the prosihctielpolymelhylmcthacrylate interface has been implicated in the initial failure process of cemented total hip arthroplasties. However, little quantitative understanding of the debonding process, as well as of the optimum interface morphology for enhanced resistance to debonding, exists. Accordingly, a fracture‐mechanics approach has been used in which adhesion at the interface is characterized in terms of the interface fracture energy. G (J/m2), and shown to be a strong function of the morphology, debonding length, and loading mode of the interface. Double‐cantilever‐beam and four‐point‐flexure fracture‐mechanics samples containing four clinically relevant prosthetic surface preparations were prepared to survey a range of interface roughness and loading modes. Adhesion at the interface could not be characterized with a single‐valueu material property but was found to exhibit resistance‐curve behavior in which resistance to debonding increased with both the initialdebond extension and the roughness of the interface. Values of debonding. initiation. Go, were relatively insensitive to the roughness of the surface and the loading mode, whereas steady‐state fracture resistance of the interface. Gss, increased significantly with the roughness and shear loading of the interface. These quantitative results suggest that debonding of the prosthetic/polymethyl methacrylate interface may be primarily attributed to surface interactions such as interlocking and the pullout of rough asperities thai occur behind the debond tip. A simple mechanics analysis of such interactions was performed and revealed increases in the fracture resistance of the interface that were consistent with experimentally measured values.
Response of chondrocyte subpopulations cultured within unloaded and loaded agarose
Authors: Lee David A. , Noguchi Takashi , Knight Martin M. , O'donnell Liam , Bentley George , Bader Dan L. 
Published: February 2005

AbstractAlthough it is well known that the metabolism of chondrocytes can be altered by the application of mechanical strain, it is unclear whether chondrocytes from the superficial and deep zones of cartilage respond in a similar manner. In this study, chondrocytes from the uppermost 15‐20% (superficial cells) and the remaining tissue (deep cells) from bovine articular cartilage were isolated separately and cultured in agarose constructs. Cell deformation on application of a 15% static compressive strain was identical for both subpopulations after 24 and 72 hours in culture. The constructs were incubated under static and dynamic (0.3,1, and 3 Hz) strains of 15% amplitude. Glycosaminoglycan synthesis by deep cells was unaffected by static strain or 3 Hz dynamic strain, whereas 0.3 Hz produced a significant reduction and 1 Hz induced a highly significant 50% stimulation of glycosaminoglycan synthesis (p < 0.001). Superficial cells exhibited a general inhibition of glycosaminoglycan synthesis. By contrast, proliferation of superficial cells was stimulated by dynamic strain whereas deep cells were not influenced. It has been suggested previously that mechanotransduction‐induced controls of glycosaminoglycan synthesis and proliferation in chondrocytes embedded in agarose are uncoupled. Data presented in this study demonstrate that the two processes do, in fact, occur in different sub‐populations of chondrocytes within the full‐depth cell isolate.
Transport of tissue inhibitor of metalloproteinases‐1 through cartilage: Contributions of fluid flow and electrical migration
Authors: Garcia A Minerva , Lark Michael W. , Trippel Stephen B. , Grodzinsky Alan J. 
Published: February 2005

AbstractThe preservation of the structure of articular cartilage depends on the availability of inhibitors of matrix‐degrading enzymes. Tissue inhibitor of metalloproteinases‐1 is thought to be an important contributor to the integrity of the matrix of articular cartilage, but the mechanisms that regulate its availability within the tissue are poorly understood. These studies elucidate the contributions of diffusion, fluid flow, and electrical migration to the transport of iodinated recombinant human tissue inhibitor of metalloproteinases‐1 through explants of adult bovine articular cartilage under conditions relevant to the loading of cartilage. With use of measured partition coefficients of the cartilage explants, the diffusivity of the inhibitor was 0.5‐1.6 × 10−7 cm2/sec. Fluid velocities that were induced by applying an electrical current across the cartilage disks increased the flux of the inhibitor by approximately 20 to more than 150‐fold compared with the effect of diffusion alone for the range of current densities that were applied. We examined the contribution of electrophoretic migration by titrating the charge on the inhibitor during measurements of flux and found that flux in the presence of the applied current decreased as the inhibitor became more negatively charged. Enhancements in the flux of the inhibitor were observed relative to the flux during diffusion alone even under conditions in which electrophoretic migration opposed the flux due to fluid flow, suggesting that of the transport mechanisms tested, fluid flow was dominant. These results suggest that the physical phenomena present during physiologic loading conditions (e.g., fluid flows and streaming currents) can affect the transport of tissue inhibitor of metalloproteinases‐1 through the matrix of cartilage.
Ultrahigh molecular weight polyethylene particles have direct effects on proliferation, differentiation, and local factor production of MG63 osteoblast‐like cells
Authors: Dean D. D. , Schwartz Z. , Blanchard C. R. , Liu Y. , Agrawal C. M. , Lohmann C. H. , Sylvia V. L. , Boyan B. D. 
Published: February 2005

AbstractSmall particles of ultrahigh molecular weight polyethylene stimulate formation of foreign‐body granulomas and bone resorption. Bone formation may also be affected by wear debris. To determine if wear debris directly affects osteoblasts, we characterized a commercial preparation of ultrahigh molecular weight polyethylene (GUR4150) particles and examined their effect on MG63 osteoblast‐like cells. In aliquots of the culture medium containing ultrahigh molecular weight polyethylene, 79% of the particles were less than 1 μm in diameter, indicating that the cells were exposed to particles of less than 1 μm. MG63 cell response to the particles was measured by assaying cell number. [3H]thymidine incorporation, alkaline phosphatase specific activity, osteocalcin production, [35S]sulfate incorporation, and production of prostaglandin E2 and transforming growth factor‐β. Cell number and [3H]thymidine incorporation were increased in a dose‐dependent manner. Alkaline phosphatase specific activity, a marker of cell differentiation for the cultures, was significantly decreased, but osteocalcin production was not affected. [35S]sulfate incorporation, a measure of extracellular matrix production, was reduced. Prostaglandin E2 release was increased, but transforming growth factor‐β production was decreased in a dose‐dependent manner. This shows that ultrahigh molecular weight polyethylene particles affect MG63 proliferation, differentiation, extracellular matrix synthesis, and local factor production. These effects were direct and dose dependent. The findings suggest that ultrahigh molecular weight polyethylene wear debris particles with an average size of approximately 1 μm may inhibit bone formation by inhibiting cell differentiation and reducing transforming growth factor‐β production and matrix synthesis. In addition, increases in prostaglandin E2 production may not only affect osteoblasts by an autocrine pathway but may also stimulate the proliferation and activation of cells in the monocytic lineage. These changes favor decreased bone formation and increased bone resorption as occur in osteolysis.