bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of cement pressure and bone strength on polymethylmethacrylate fixation
Authors: Askew Michael J. , Steege John W. , Lewis Jack L. , Ranieri John R. , Wixson Richard L. 
Published: February 2005

AbstractThe effect of the quality of the bone and of the cement pressurization magnitude and duration on the fixation achieved with polymethylmethacrylate (PMMA) bone cement is studied in vitro. Seventy‐one cementbone interface specimens, prepared under various conditions of pressurization of low‐viscosity bone cement, are tested in tension. The load at failure and the maximum cement penetration are measured to assess the fixation achieved, and the quality of the bone is assessed by determining the compressive strength of each of the bone specimens. Statistical analysis of the data indicates that the pressure magnitude is the most influential of the factors considered in the cement penetration behavior and in the development of failure load capacity. The duration of the pressure does not appear to be a significant factor. The cement penetration is a decreasing function of the bone strength, reflecting a decrease in the porosity and an increase in the area fraction. Although not directly measured in these tests, these latter bone properties are indirectly measured by the bone compressive strength. The effect of increasing bone strength on the failure load is nonlinear. The development of adequate failure load capacity is the result of a balance between the cement penetration allowed by the porosity of the bone and the inherent strength of the cancellous bone itself. Weak bone, although adequately penetrated by cement, cannot provide strong fixation. Stronger, denser bone limits cement penetration, but pressurization enhances development of failure load capacity through more complete infusion and interlocking of the cement in the available pore space. The strength of the fixation achievable for any bone is limited by the intrinsic strength of the bone. An optimal depth of cement penetration of 4 mm and an optimal bone area fraction of 0.20 are suggested for the most effective fixation.
Effects of fat admixture on the strengths of conventional and low‐viscosity bone cements
Authors: Ferracane J. L. , Wixson R. L. , Lautenschlager E. P. 
Published: February 2005

AbstractThe diametral tensile and compressive strengths of both conventional doughy and low‐viscosity (LVC) bone cements were tested with sequential admixtures of up to 50% (by weight) liquified fat. The addition of as little as 5% (by weight) fat caused a significant reduction (p = 0.05) in the strengths of both cements. The LVC appeared to be affected to a greater degree by fat contaminations than did the conventional cement, although the strengths of the LVC were generally equal to or higher than those of the conventional cement. The enhanced effect of fat contamination on the LVC was thought to be due to the more fluid, tacky nature of this material during administration.
Dynamic radioisotope bone imaging as a noninvasive indicator of canine tibial blood flow
Authors: Nutton Richard W. , Fitzgerald Robert H. , Brown Manuel L. , Kelly Patrick J. 
Published: February 2005

AbstractThe relative values of dynamic and static bone imaging with hydroxymethylenediphosphonate technetium 99m (99mTc HDP) as an indicator of bone blood flow was investigated in the tibia of mature dogs. The dynamic bone scan consisted of 60 1‐s images formed after the intravenous injection of 99m Tc HDP, and the static bone scan was a 45‐min uptake image. Blood flow to the tibia was determined by using radioactively labeled microspheres. Studies were carried out in control dogs, in dogs in which blood flow was increased in one leg with ATP, and in dogs in which blood flow was decreased in one leg with norepinephrine. A significant (p < 0.001) linear relationship between the dynamic scan values and bone blood flow was found at a wide range of blood flow rates. When blood flow increased by more than 50%, the effects of “diffusion limitation” were seen in the static scans: increase in tracer uptake was disproportionately small for a significant increase in blood flow. There is no method currently available for estimating bone blood flow by a noninvasive technique. The method described here may be useful for providing a semiquantitative measure of bone blood flow. This improved versatility of bone imaging may have a role in the management of osteomyelitis or complicated fractures, or in assessing the viability of vascularized bone grafts.
Invalidity of single‐passage measurements of the extraction of bone‐seeking tracers in rats and rabbits
Authors: Tothill P. , Hooper G. 
Published: February 2005

AbstractSingle‐passage experiments in which bone‐seeking tracers are injected arterially at the same time as microspheres to determine an extraction ratio are only valid if the maximum transit time through bone is less than the minimum recirculation time. This validity was investigated by injecting various intravascular and more diffusible tracers into the hearts or aortas of rats and rabbits at different times before the rapid cessation of circulation. At no time between 4 and 60 s after injection did the bone concentration of any of the tracers fall to negligible values. Removal of unbound tracer is therefore not complete before recirculation starts, and the single‐passage technique is invalid. Measurements of bone blood flow based on the clearance of 18F cannot be substantiated, as its extraction is flow dependent.
Changes in long‐bone structural properties during the first 8 weeks of plate implantation
Authors: Carter D. R. , Shimaoka E. E. , Harris W. H. , Gates E. I. , Caler W. E. , McCarthy J. C. 
Published: February 2005

AbstractThe midplate structural rigidities of metal‐ and plastic‐plated intact canine femora were experimentally determined after initial plate application and 8 weeks after in vivo implantation. Composite beam theory significantly overestimated the bending rigidities of the metal‐plated bones. The rigidities of the plastic‐plated bones were nearly identical to that of the isolated bone, as composite beam theory predicted. Plating with either plate increased the intracortical porosity and caused the deposition of periosteal new bone, which was greater with plastic than with metal plates. The increased rigidities provided by the attachment of the metal plates and, hence, the degree of bone strain shielding were variable. Platings for 8 weeks which provided little strain shielding with either metal or plastic plates caused an increase in bone flexural rigidity (measured after plate removal) with respect to the contralateral control. Platings that provided increasing amounts of strain shielding caused a decreasing midplate bone rigidity (measured after plate removal) and increasing bone deposition at the outer screws. These findings suggest that the surgical implantation of any plate (metal or plastic) will provide a net stimulus to bone formation and consequently increased bone structural rigidity, even though intracortical porosity is increased. If the plate significantly reduces the normal loads borne by the bone, however, there is a net stimulus to remove bone, resulting in a loss of midplate structural rigidity within 8 weeks of implantation.
Partial purification and characterization of a proteoglycan‐degrading neutral protease from bovine epiphyseal cartilage
Authors: Ehrlich Michael G. , Armstrong Ann L. , Mankin Henry J. 
Published: February 2005

AbstractDegradation of the proteoglycan matrix is considered an essential step in the process of calcification in the growth plate. This laboratory has just described the presence of a protease in human growth plate cartilage that degrades proteoglycan at neutral pH. We report here the isolation, partial purification, and characterization of these proteoglycan‐degrading neutral proteases of bovine epiphyseal cartilage. It appears that there is more than a single enzyme active at neutral pH. These enzymes are of low molecular weight (below 30,000), poorly charged, and inhibited by metal chelating agents. Activity is best restored in the presence of zinc. This represents the first characterization of this important enzyme group.
Spontaneous degenerative spinal disease in the laboratory rabbit
Authors: Green P. W. B. , Fox R. R. , Sokoloff L. 
Published: February 2005

AbstractThe spines of 35 rabbits (32 New Zealand white and 3 AC/J), ranging in age from 3 months to 8½ years, were investigated systematically for spontaneous degenerative changes. Three types of lesion were observed. (1) The nucleus pulposus underwent chondroid metaplasia throughout the length of the vertebral column by the age of 2 years. (2) Hydroxyapatite deposition was found in the nucleus pulposus in 12 of 20 animals examined roentgenographically. The lesion occurred principally in the distal thoracic segments and was first observed in 3‐month‐old rabbits. (3) Spondylosis occurred in each of four macerated spines from animals >24 months old. Portions of the spine spared by disc calcification were affected.
Response of amputated rat limbs to fetal nerve tissue implants and direct current
Authors: Sisken Betty F. , Fowler Ira , Romm Sharon 
Published: February 2005

AbstractWe have previously shown that implanted fetal nerve tissue stimulates the regeneration of amputated chick limbs. The purpose of this study was to determine whether a similar phenomenon would occur in amputated rat limbs and if addition of applied direct current (DC) would affect this process. Thus, fetal nerve tissue was implanted into amputated stumps of 3‐week‐old rats; variable tissue regeneration was induced that was dependent on the age of the donor implant and the presence of applied DC. Twelve or 14 day fetal neural implants induced new accessory bones containing epiphyseal plates and marrow cavities and occasionally formed joint‐like structures with the host humerus. Addition of DC to 12 day neural implants increased the number of new bones formed. Eighteen day neural tissue with applied DC did not induce new bone formation but stimulated the maximal elongation of the host humerus and outgrowth of nerve fibers to the cut surface. Implantation of fetal heart tissue or implantation of fetal neural tissue into unamputated limbs failed to induce new bone formation. Although true limb regeneration was not achieved, formation of new skeletal elements did occur and this effect was enhanced by applied DC.
In vitro contact stress distribution on the femoral condyles
Authors: Brown Thomas D. , Shaw Daniel T. 
Published: February 2005

AbstractContact stress distributions were measured across the tibiofemoral joints of 11 fresh‐frozen normal cadaver specimens. Local stress magnitudes were sensed by arrays of miniature piezoressistive transducers inset superficially in the cartilage of the femoral condyles. Knee joints were tested at 0, 10, 20, and 30° of flexion and later retested at 0° following medial and dual meniscectomies. For the intact joint, both the spatial mean and peak local contact stresses rose approximately linearly with the joint resultant, reaching levels of 2.6 and 8.0 MPa, respectively, at 3 kN of applied loading. Flexion angle variations in the range studied failed to cause significant changes in the major contact parameters. Although meniscectomies involved contact area reductions and consequent stress increases, such effects were more moderate than results previously seen for static loading of the tibial plateau.
Microinjury to the synovial membrane may cause disaggregation of proteoglycans in rabbit knee joint articular cartilage
Authors: Frost Linda , Ghosh Peter 
Published: February 2005

AbstractProteoglycans (PGs) isolated from articular cartilage (AC) of mature rabbits subjected to two or more consecutive intraarticular (IA) injections of sterile saline 24 h apart showed an aggregation defect in the presence of excess hyaluronic acid (HA). Although the PG contents of experimental and control cartilages were indistinguishable, a higher proportion of PGs were extractable from the 3 × IA tissues, as assessed by uronic acid analysis. Proteoglycans from experimental and control cartilages when examined by Sepharose CL‐2B chromatography showed two subunit populations, the smaller (KAV = 0.70) containing more ketatan sulphate than the larger (KAV = 0.31). Cultures of AC from IA joints released more 35SO4‐labelled PGs into the media over 72 h than control tissues and consisted mainly of PG degradation products although 20% could aggregate in the presence of HA. Examination of PG aggregation 2 weeks after 2 × IA or 3 × IA injections showed that the defect initiated was still present; however, cartilage of immature rabbits was not affected by the 2 × IA procedure.
Pathogenesis of chronic inflammation in experimental ferritin‐induced arthritis. V. Electron microscopic localization of specific antibodies in the synovial membrane
Authors: Sakata Toshiro , Ohno Osamu , Ishikawa Hitoshi , Hirohata Kazushi , Cooke T. D. V. 
Published: February 2005

AbstractAntibody synthesis by the arthritic synovium of rabbits with antigen‐induced arthritis has been demonstrated, but knowledge of the details of the specific localization of antibody in the membrane is limited. Specific antibody in the synovium of ferritin‐induced arthritis was detected by electron microscopic observation of bound ferritin. The specific antibodies were localized in the cisternae of the endoplasmic reticulum and perinuclear spaces within plasma cells. In the extracellular matrix, specific antibody was found distributed as a network within collagen bundles and in the basement membrane of the subsynovial small blood vessels.
Biomechanics of bipolar hip endoprostheses
Authors: Krein S. W. , Chao E. Y. S. 
Published: February 2005

AbstractThe bipolar endoprosthesis was designed to alleviate problems encountered with conventional hip endoprostheses. Recent designs have advocated the use of offset centers of rotation between the inner and outer jointbearing surfaces to generate a valgus‐producing moment on loading (antivarus head dynamics). This study was undertaken to justify this biomechanical feature by performing (a) cyclic loading of the bipolar head in the varus position, (b) analysis of motion between the inner and outer bearing surfaces, and (c) evaluation of antivarus head dynamic function. Four endoprosthetic designs were studied: the Bateman UPF, Osteonics UHR, Giliberty II, and Bi‐Centric. Significant plastic deformation occurred in the UPF and UHR prostheses when loaded in an extreme varus position. Theoretically, motion is most likely to occur at the inner bearing if the frictional coefficients are equal at both surfaces. The UHR prosthesis with eccentric offset of bearing centers can provide the antivarus effect in laboratory conditions. Whether the antivarus effect and/or the dominant inner bearing motion will occur in vivo awaits careful clinical study.
Stress analysis of a partially slotted intramedullary nail
Authors: Beaupré Gary S. , Schneider Erich , Perren Stephan M. 
Published: February 2005

AbstractA finite element analysis of the Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) intramedullary femoral nail was performed to study the failure of the nail from circumferential cracking near the slot tip. These failures are evidently the result of a stress‐concentrating effect owing to the partially slotted nail design. Several finite element models were created of the proximal one‐fourth of the nail. One model of the nail incorporated the cloverleaf profile as it is presently manufactured, and one had a circular cross section. An additional three models were created with alternative slot‐tip geometries: a narrowed slot, a tapered slot, and a widened slot. Antero‐posterior (AP) and medio‐lateral (ML) bending loads and torsion loads were applied in two fundamentally different loading modes: (1) loads that were applied on both sides of the slot tip (spanned); and (2) loads that were self‐equilibrating distal to the slot tip (non‐spanned). For the load cases studied, for all models, the stresses predicted from the finite element models were locally highest at the junction between the open and closed cross sections. Alternative slot‐tip shapes had a marked effect on the predicted stresses, in one case reducing maximum stress by 40%. However, no alternative slot tip shape was uniformly superior for all load cases. Therefore, until the in vivo loading modes are known more precisely, an alternative slot‐tip shape cannot be proposed.
Fatigue performance of external fixator pins
Authors: Kasman Roberta A. , Chao Edmund Y. S. 
Published: February 2005

AbstractThe fatigue performance of several types of commonly used external fixator pins was examined. The pins were tested under a cyclic bending mode. A strength reduction factor (SRF) was defined to quantify the effect of stress concentration caused by the pin threads as compared with the smooth portion of the pin. The half pins tested had much higher SRF values than the corresponding full pins because of the smaller root diameter of the threaded regions. The use of finer threads and a cold rolling process appeared to increase the pin fatigue strength. In some pins, the depth markers on the smooth portion and the self‐tapping fluted region were sites of significant stress concentration. When certain half pins are severely loaded under clinical conditions, they may fracture because of fatigue.
Radiation sterilization and the wear rate of polyethylene
Authors: Rose R. M. , Goldfarb E. V. , Ellis E. , Crugnola A. N. 
Published: February 2005

AbstractThe resistance to sliding wear was measured in bovine serum for two polyethylenes with molecular weights of about 105 and 106 that had been irradiated in air and nitrogen with γ‐ray dosages up to 20 Mrad. Molecular weight measurements were performed after irradiation as well. Wear generally increased with dosage and contact stress, becoming measurable in many cases only after a critical dose (or stress) was exceeded. The most significant effect noted was that the irradiation changed the pressure dependence of the wear rate. Thus, whether or not a sterilizing (or resterilizing) dose will measurably increase the wear depends on the contact stress and, therefore, on the specific application. The increase in wear rate appeared to be due to a combination of scission and oxidation, suggesting the practical advisability of radiation sterilization under an inert atmosphere, as confirmed by comparative measurements at the higher dosages.
Interrupted and continuous microarteriorrhaphy techniques: A hemodynamic comparison
Authors: Blair William F. , Pedersen Douglas R. , Joos Karen , Bondi David 
Published: February 2005

AbstractThe purpose of this study was to compare interrupted and continuous suturing techniques in laboratory microarteriorrhaphy. The comparison was based on rat femoral artery hemodynamic variables, including blood velocities, lumen diameters, and calculated blood flow. These variables were calculated by an offline computer from Doppler frequency shifts that were measured by a 20‐MHz pulsed ultrasonic Doppler velocity meter. No statistical difference was noted postoperatively between the interrupted and continuous techniques relative to any hemodynamic variable. Average blood flow after the interrupted (n = 12) and continuous (n = 12) techniques was 6.59 ± 1.12 and 6.74 ± 1.20 ml/min, respectively. The two microarteriorrhaphy techniques result in equal postoperative vessel hemodynamics in a laboratory model.
Topographical variations in the morphology and biochemistry of adult canine tibial plateau articular cartilage
Authors: Bullough Peter G. , Yawitz Peter S. , Tafra Lorraine , Boskey Adele L. 
Published: February 2005

AbstractTopographically, there are both morphological and biochemical differences in the articular cartilage of the tibial plateau of normal adult dogs when the cartilage covered by the meniscus is compared with that more centrally placed and not covered by meniscus. Histologically, differences are present in the surface morphology, in intra‐ and extracellular lipid content, and in the morphology of the mineralization front. Electron microscopy shows, in the covered cartilage, variability in collagen fiber size, with evenly spaced fibers apparently randomly distributed and an orderly relationship between the proteoglycans and collagen, whereas in the uncovered area, the collagen is aggregated into bundles and appears to be dissociated in large part from the proteoglycans. The most striking feature in the biochemistry of the two regions is an increased water content in the uncovered cartilage, as compared with the covered. In addition, there is an increased amount of proteoglycans that can be extracted in the uncovered cartilage. The heterogeneity of the cartilage on the tibial plateau should be taken into account when considering both the histologic and biochemical variations found in osteoarthritic cartilage; and when reflecting on the pathogenesis of osteoarthritis.
Determination of callus quantity in 4‐ week‐old fractures of the rat tibia
Authors: Aro H. , Eerola E. , Aho A. J. 
Published: February 2005

AbstractIn clinical practice the quantity of fracture callus is usually estimated on the basis of radiographs. In experimental studies on fracture healing, more exact chemical measurements (total protein, DNA, and mineral contents) have been used to quantitate the amount of callus. It is not known, however, how these two parameters correlate with each other. In this study we used different (radiographic, histomorphometric, and chemical) methods to evaluate the quantity of fracture callus in 4‐week‐old tibial fractures of rats stabilized by intramedullary nailing. The wet and dry weights and the nitrogen, collagen, calcium, phosphorus, and DNA contents of the calluses showed no correlation with the radiographic size of the calluses. There was a strong correlation (p < 0.001), however, between radiographic and histomorphometric callus sizes. The mass of callus and the chemically defined parameters of callus production thus indicate different properties of the healing bone.
Binding sites in fetal and growth plate cartilage
Authors: Cruess Richard L. 
Published: February 2005

AbstractIn addition to genetic and nutritional factors, linear growth during the prenatal and postnatal periods is controlled by peptide, steroid, and thyroid hormones interacting with the receptors present on the membrane or in the cytosol and nuclei of growth plate cartilage. Using standard procedures, insulin and “nonsuppressible insulin‐like activity” (a somatomedin) showed significant binding in 600, 15,000 and 105,000 g membrane fractions of epiphyseal cartilage of immature animals. The binding of growth hormone and prolactin was small and probably not significant. Specific uptake of glucocorticoid was demonstrated in viable canine chondrocytes, but not of androgen, estrogen, or vitamin D3 metabolite. A triiodothyronine receptor was present in nuclei from dog epiphyseal cartilage. Hormones that lack binding may affect cartilage only indirectly. Hormone receptors were studied in those portions of fetal growth cartilage that will later evolve into an ossification center, articular cartilage, and epiphyseal cartilage. Cytosol fractions contained a receptor for glucocorticoid but not for androgen or estrogen. Zonal analysis showed a higher level in the peripheral and central sections than in the palisade section. Triiodothyronine binding was also detected in nuclei prepared from whole fetal cartilage. Heterogeneity of cell function was obvious in fetal cartilage. Cell division was high in the central and peripheral zones as well as the upper half of the palisade zone, but low in the lower palisade section. Proline and sulfate incorporation predominated in the palisade section compared with the central and peripheral sections. Disease states with changes of metabolic activities in the cartilage may perhaps be better understood with a clearer knowledge of receptor levels and interactions.