bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of failure of the ligamentum flavum of the spine during in vitro tensile tests
Authors: Sikoryn T. A. , Hukins D. W. L. 
Published: February 2005

AbstractThirty ligamenta flava were dissected from pig lumbar spines with their attachments to the bone of the laminae still intact. These specimens were tested to failure, in tension, at strain rates of 0.03 and 0.2s‐1. Video recordings ligaments became detached from the bone. The maximum stress that the ligaments were able to transmit was approxmately 3 MPa. However, the corresponding strain was higher when testing at the slower strain rate than at the faster rate; these strains were 1.6 ± 0.5 and 1.0 ± 0.3, respectively. All specimens were able to transmit stress after the maximum value had been attained because threads of ligament continued to remain attached to bone. Complete failure did not occur until the last of these threads had pulled away. Scanning electron micrographs showed no ligament, other than a few isolated pieces of fibre, adhering to bone after failure had occurred.
Effects of variation in systemic blood pressure on intraosseous pressure, PO2, and PCO2
Authors: Kiær Thomas , Grønlund Jørgen , Jensen Birgit , Svalastoga Eiliv 
Published: February 2005

AbstractSeveral regulatory mechanisms have been shown to influence the intraosseous circulation. The influence of general hypovolemia on bone circulation and possible regulatory effects were investigated by recording the intraosseous pressure and PO2 and PCO2 continuously by mass spectrometry in rabbits. Hypovolemia was induced by repeated bleedings. The intraosseous and arterial pressures were found to be linearly related. The intraosseous PO2 already decreased after the first step of bleeding and decreased more than 50% of the initial value after an average blood loss of 40 ml. The intraosseous PCO2 showed an opposite pattern. The experimental PO2 vs. arterial pressure curves were similar to curves obtained by a computer simulation that assumes the blood flow to be proportional to the intraosseous pressure.
A reduced‐modulus acrylic bone cement: Preliminary results
Authors: Litsky Alan S. , Rose Robert M. , Rubin Clinton T. , Thrasher Elliott L. 
Published: February 2005

AbstractExcessive local contact stress is implicated as an important factor in the initiation of the loosening process after total joint arthroplasties. A reduced‐modulus acrylic bone cement, which decreases the bone‐cement interface stresses, was developed to test this hypothesis. The formulation consists of butylmethacrylate beads, having a glass transition temperature of 27°C in a methylmethacrylate matrix. This cement, polybutylmethylmethacrylate (PBMMA), has an elastic modulus one‐eighth that of standard PMMA bone cement, 0.27 vs. 2.1 GPa, at body temperature. In vivo use in a pilot study using the sheep total hip arthroplasty model shows a reduction in the rate of loosening of femoral components when compared both radiographically and mechanically with PMMA controls.
The geometry of the adult canine proximal femur
Authors: Sumner Dale R. , Devlin Terrance C. , Winkelman D. , Turner Thomas M. 
Published: February 2005

AbstractThe canine is often used as a model to study functional bone adaptation after total hip replacement. To improve our understanding of the model, we defined the central tendencies and statistical variations in the crosssectional geometry, angle of anteversion, and cervicodiaphyseal angle of the proximal femur in 15 adult male mongrel dogs and compared the results with published reports of the human femur. Numerous similarities in the crosssectional geometry of the canine and the human femur were noted, supporting the use of the canine as a model. The two species differed in that the orientation of the principal axes in the proximal cross sections was not related to the angle of anteversion in the canine femur, whereas these angles are related in humans. In addition, the canine medullary canal is larger than the human medullary canal relative to the external dimensions of the femur, and hence the canine has relatively thinner cortical bone. This difference in femoral crosssectional geometry may explain, in part, why the canine provides an accentuated model of bone loss in hip arthroplasty experiments.
Wrist‐joint ligament length changes in flexion and deviation of the hand: An experimental study
Authors: de Lange A. , Huiskes R. , Kauer J. M. G. 
Published: February 2005

AbstractA method to study ligament‐length patterns in situ with roentgenstereophotogrammetry, using strings of glued tantalum markers, was developed. The method was tested against a bone‐to‐bone marking method in five carpal ligaments in three specimens, whereby the hand was moved through dorsopalmar flexion and radioulnar deviation. The “glued‐string” marking method was found to be superior to the bone‐to‐bone marking method. The length patterns obtained were found to be reproducible in the specimens and different from earlier expectations presented in the literature. The radiocapitate ligament seems to limit the displacements of the capitate in both radial and ulnar deviation, and dorsal flexion. The radiolunate ligament has the same effect for the lunate. Both the dorsal radiotriquetrum and the palmar triquetrocapitate ligaments seem to play a stabilizing role in the neutral position of the hand, whereas the radiotriquetrum ligament also has a function in palmar flexion and the triquetrocapitate ligament functions in dorsal flexion, ultimately resisting these excursions. These findings require confirmation in more extensive experiments, whereby the relationship between ligament length patterns and carpal motion axes is investigated.
Effect of direct current stimulation on bone growth after distraction epiphysiolysis of the rabbit tibia
Authors: van Roermund Peter M. , Hoekstra Anne , Visser Walter J. , Renooij Willem 
Published: February 2005

AbstractThe effect of direct current stimulation on bone formation during limb lengthening was tested in a lower leg lengthening model in the rabbit. Limb lengthening was performed by distraction epiphysiolysis. A specially designed external distraction device was placed at the tibia. The distractor allowed 10 mm of lengthening in 4 weeks. Two weeks after starting the distraction, a platinum electrode was passed through the anterior cortex below the tibial tuberosity and advanced via the medullary cavity so that the tip rested in the elongated zone. Stimulation started at the time of placement of the electrodes and was continued for 3 weeks. The electrode in the elongated zone served as the cathode; the anode was placed subcutaneously. A 20 μA stimulus was selected. A control group received the same treatment without stimulation. Bone formation in the elongated zone was evaluated by histology and scintigraphy. The data from this experiment show that direct current stimulation in the early phase of a limb lengthening procedure had no effect on the extent of bone formation in the elongated zone.
Biochemical characterization of long‐term culture of the swarm rat chondrosarcoma chondrocytes in agarose
Authors: Kucharska Anna M. , Kuettner Klaus E. , Kimura James H. 
Published: February 2005

AbstractDifficulty in maintaining phenotypic stability of the Swarm rat chondrosarcoma in long‐term monolayer cultures has prompted investigation of alternative conditions that would enable extended maintenance of these cells, permitting use of the tumor as a model system for the long‐term study of proteoglycan metabolism. Morphological analysis of the growth of the chondrosarcoma chondrocytes in agarose has shown stability of the culture over a 20 day period with respect to the ability of the cells to proliferate and synthesize an Alcian blue‐positive extracellular matrix. The present study confirms these findings through analysis of the growth characteristics of the culture and the pattern of proteoglycan‐rich matrix at a rate dependent on the initial plating density and concentration of serum in the culture medium. These factors similarly affect the proliferative capabilities of the culture as demonstrated by the growth curves obtained at different culture conditions. During 20 days in culture, the cells synthesize an aggregating chondroitin sulfate proteoglycan and collagen type II, typical of cartilage and this chondrosarcoma. In addition, small molecular weight proteoglycans were found to be present at concentrations of up to 10% of the total proteoglycan population. Degradative rates are slow, the proteoglycan half‐life is about 30 days, but can be enhanced with retinol, reducing the half‐life to 2 days.
Attachment of epiphyseal cartilage cells and 17/28 rat osteosarcoma osteoblasts using mussel adhesive protein
Authors: Fulkerson John P. , Norton Louis A. , Gronowicz Gloria , Picciano Paul , Massicotte J. Mathieu , Nissen Carl W. 
Published: February 2005

AbstractThese experiments show that mussel adhesive protein (MAP) enhances the attachment of osteoblasts and epiphyseal cartilage cells to plastic culture dishes and Vitallium. When MAP was applied to culture plate surfaces, there were two‐ to fivefold increases in the numbers of cells attaching compared to control surfaces (no MAP). Results were confirmed using two different cell attachment assay techniques. Osteoblast replication and culture on MAP is possible, suggesting that MAP is not toxic to cells. MAP also holds applied cells to surfaces as initially attached.
The use of two nutritional indicators in identifying long bone fracture patients who do and do not develop infections
Authors: Puskarich Cheryl L. , Nelson Carl L. , Nusbickel Fred R. , Stroope Henry F. 
Published: February 2005

AbstractOne hundred consecutive orthopedic long bone fracture patients requiring surgical fixation were nutritionally assessed using both the nutritional index of Rainey‐MacDonald et al. and total lymphocyte count. The ability of these two parameters to identify correctly those patients who do and do not develop postoperative complications was assessed using several error rate measures, which included sensitivity, specificity, positive predictive value, negative predictive value, and accuracy. Fourteen of our patients developed postoperative complications. All complications observed were infections. The accuracy of the nutritional index and total lymphocyte count in predicting patient outcome was 78 and 51%, respectively. The positive and negative predictive values calculated for the nutritional index were 36 and 94%, respectively. Total lymphocyte count analysis resulted in positive and negative predictive values of 15 and 87%, respectively. In our sample of patients, the nutritional index was a better predictor of patient outcome than total lymphocyte count, as indicated by the higher accuracy rate calculated for the nutritional index. Based upon positive predictive value results, neither of these indicators was most accurate in identifying patients who did develop infections. Not unexpectedly, both indicators were best in identifying those patients who did not develop postopertive infections.
Proteoglycan alterations following immobilization and remobilization in the articular cartilage of young canine knee (stifle) joint
Authors: Säämänen Anna‐Marja , Tammi Markku , Jurvelin Jukka , Kiviranta Ilkka , Helminen Heikki J. 
Published: February 2005

AbstractThe distribution of proteoglycans (PGs) at 11 sites on the knee (stifle joint) cartilage of young female beagle dogs was studied following cast immobilization for 11 weeks in 90° flexion and after a subsequent remobilization for 15 weeks. Immobilization induced a reduction in PG uronic acid at all sites (mean of −38%), but the greatest depletion ( −64%) occured at the anterior and posterior extremes of the femoral condyles, i.e., at locations where the immobilized cartilage lost contact to the opposing cartilage. Following remobilization, the content of uronic acid remained lower than in the agematched controls (−18% on average), particularly at the minimum contact sites most affected by immobilization (−33%). The chondroitin‐6‐sulfate to chondroitin‐4‐sulfate ratio was reduced by immobilization in most locations (average of −14%) and returned to control values after remobilization. There was no consistent change in the percentage of aggregating PGs observed in Sephacryl S‐100 gel filtration after immobilization or remobilization. However, following remobilization, the aggregating PGs showed an enhanced proportion of the slower mobility band in agarose gel electrophoresis, indicative of a larger monomer size. In the contralateral, load‐bearing knee joint, both the uronic acid content and PG monomer type distribution were identical to those observed in the experimental joint, suggesting that the state reached after the remobilization period was due to factor(s) influencing both side. The results suggest that contact forces between articulating surfaces are required to maintain normal PG content and that the control mechanism works locally at each cartilage site. Restriction of joint mobility and loading in young animals is concluded to cause persistent changes in cartilage matrix. Furthermore, the use of the contralateral joint as the sole control in this kind of studies, although experimentally convenient, seems not to be appropriate.
Immunohistochemical and biochemical demonstration of calcium‐dependent cysteine proteinase (calpain) in calcifying cartilage of rats
Authors: Shimizu Katsuji , Hamamoto Takashi , Hamakubo Takao , Lee Woon Joo , Suzuki Kiichi , Nakagawa Yasuaki , Murachi Takashi , Yamamuro Takao 
Published: February 2005

AbstractCalpain is a Ca2+‐dependent cysteine proteinase that has neutral pH optima. There are two classes of calpains that differ in their optimal calcium ion concentration for enzymatic activity. Calpain I requires a low concentration of Ca2+ for activation, and calpain II requires a much higher Ca2+ concentration. This report describes the immunohistochemical and biochemical demonstration of calpain II in calcifying cartilage in rats and also the degradation of the cartilage proteoglycan subunit by calpain II. Immunoperoxidase (peroxidase‐antiperoxidase) staining of the frozen sections of the knee joint from 3‐day‐old and 6‐day‐old Wistar rats, using polyclonal antibodies against the respective heavy subunits of calpains I and II, showed positive staining only with the anti‐calpain II antibody in the hypertrophic chondrocytes and surrounding cartilaginous matrix of the growth cartilage. Diethylaminoethyl‐cellulose chromatography of the cartilaginous extract from 3‐day‐old rats showed a peak of caseinolytic activity attributable to calpain as well as an inhibitory peak of calpastatin, a specific inhibitor protein of calpains. Immunoblotting using the anti‐calpain II antibody of the calpain peak demonstrated identity with the heavy subunit of calpain II (80 kDa). Proteoglycan‐degrading activity of calpain was assessed using porcine kidney calpain II and the porcine articular cartilage proteoglycan subunit. After incubation in the presence of Ca2+, degradation of proteoglycan was demonstrated by the change of the elution position on Sepharose‐2B chromatography. It is possible that calpain functions as one of the proteoglycan‐degrading proteolytic enzymes of growth cartilage. Intracellular localization of calpain in hypertrophic chondrocytes also suggests a role in the hypertrophic process of the chondrocyte in growth cartilage.
Biomechanical evaluation of a biodegradable composite as an adjunct to internal fixation of proximal femur fractures
Authors: Witschger Pierre M. , Gerhart Tobin N. , Goldman Janet B. , Edsberg Laura E. , Hayes Wilson C. 
Published: February 2005

AbstractInternal fixation of comminuted unstable fractures of the severely osteoporotic proximal femur is sometimes supplemented with polymethyl‐methacrylate (PMMA). We here report an in vitro biomechanical evaluation of a biodegradable particulate composite that might be used for similar purposes. The composite includes a matrix phase consisting of a hydrolyzable prepolymer [polypropylene fumarate (PPF)] cross‐linked with methacrylate monomer, and a particulate phase consisting of tricalcium phosphate and calcium carbonate. We implanted dynamic hip screws in 22 cadaveric proximal femora and measured the yield load for an oblique force applied to the femoral head. The hip screws were then reinforced with either PMMA or the PPF composite and tested again. On the basis of analysis of variance, the average increases in yield load for PMMA and PPF reinforcement of 1, 750 and 1,130 N were statistically significant (p < 0.00005), suggesting that both materials enhance congruence between implant and bone and thereby increase the projected load‐bearing area of the implant. The increase in yield force with PMMA was slightly higher than the increase with PPF (p < 0.05), but both values after reinforcement were close (3,790 ± 561 N for PMMA vs. 3,240 ± 669 N for PPF). If we can demonstrate that appropriate rates of degradation, bony ingrowth, and static and fatigue properties can be achieved in vivo with this system, our data suggest that this PPF composite may have potential as an adjunct to the internal fixation of unstable fractures of the osteoporotic hip.
Variables affecting disc size in the lumbar spine of rabbits: Anesthesia, paralysis, and disc injury
Authors: Neufeld J. Hulse , Machado T. , Margolin L. 
Published: February 2005

AbstractMethods have been developed that permit repetitive radiographic measurement of the lumbar intervertebral disc space in a rostral‐caudal direction (width) in the anesthetized laboratory rabbit. Using isolated control discs and injured discs in which narrowing has been induced for chronic and acute periods, the widths of the lumbar intervertebral disc spaces determined radiographically correlate with widths determined histologically (p < 0.000, r = 0.75). Both an increase (widening) and a decrease (narrowing) in disc width were observed using radiography after different experimental treatments. Anesthesia and lower‐body paralysis (an experimentally induced inability to bear weight on and to perceive a pinch stimulus in hind limbs) caused widening of the discs: anesthesia causing a general widening throughout the lumbar spine and lower‐body paralysis causing a specific widening low in the lumbar spine. Both disc injection and piercing the disc with needles to recover nucleus pulposus material caused narrowing of the discs. Acridine‐orange injection induced a narrowing accompanied by osteophytosis. Experimentally induced narrowing at L4–5 (the result of injury to the disc) resulted in narrowing also at L2–3. These findings are consistent with the hypothesis that in vivo disc‐width size in the young rabbit depends on both the quantity of nucleus pulposus material and the force‐generating activities of the adjacent spinal muscles, and that disc injury at one level stimulates narrowing at other levels.
Three‐dimensional kinematics of glenohumeral elevation
Authors: An K.‐N. , Browne A. O. , Korinek S. , Tanaka S. , Morrey B. F. 
Published: February 2005

AbstractTo help resolve longstanding uncertainties about kinematics of the shoulder, we studied three‐dimensiona glenohumeral joint motion during arm elevation. A magnetic tracking system was used to monitor the threedimensional orientation of the humerus with respect to the scapula. Appropriate coordinate transformations were then performed for the calculation of glenohumeral joint rotation based on the defined Eulerian angle. The effects of the plane of elevation and the humeral rotation on the magnitude of arm elevation were documented. The maximum humeral elevation at the glenohumeral joint took place in a plane anterior to the scapular plane. Maximum elevation in all planes anterior to the scapular plane required external axial rotation of the humerus. Conversely, internal axial rotation was necessary for maximum elevation posterior to the scapular plane. Quantifying the obligatory axial rotation explains the relationship of internal and external rotation with maximum elevation.
A quantitative analysis of matrix alignment in ligament scars: A comparison of movement versus immobilization in an immature rabbit model
Authors: Frank C. , MacFarlane B. , Edwards P. , Rangayyan R. , Liu Z‐Q. , Walsh S. , Bray R. 
Published: February 2005

AbstractThis investigation quantified the alignment of fibrillar matrix in normal rabbit medial collateral ligaments (MCLs) and in healing MCLs from animals treated with or without knee immobilization. Twenty‐four immature female rabbits were given complete midsubstance injuries to their right MCLs. Fifteen of them had that knee pin immobilized in flexion, while the remaining nine were allowed unrestricted cage activity. Animals were sacrificed in groups of three at intervals of 3, 6, or 14 weeks after injury, and both healing MCLs and unoperated contralateral controls were fixed in situ for subsequent removal, freeze‐fracture, and preparation for scanning electron microscopy (SEM). A random sampling of SEM photographs followed by atuomated, statistically validated image processing was used to quantify alignment of matrix in all samples. Results showed that nonimmobilized MCL scars in this model do remodel over 14 weeks of healing, returning to normal alignment values in that time. Surprisingly, MCL scars in immobilized knees were even better, with mean matrix alignments falling statistically within normal MCL limits at all healing intervals studied. If not due to an unknown sampling or fixation artifact, these results suggest that gross knee flexion and extension is not a prerequisite for scar matrix alignment in this immature model of ligament healing.
Comparison of the stability of press‐fit hip prosthesis femoral stems using a synthetic model femur
Authors: McKellop H. , Ebramzadeh E. , Niederer P. G. , Sarmiento A. 
Published: February 2005

AbstractThe motion of three different press‐fit hip prosthesis femoral components was compared with that of a cemented stem and an Austin Moore noncemented hemiarthroplasty. Synthetic composite femurs were used as an experimental model to reduce the variations in shape and quality typical among cadaver femurs. Motion was measured under axial and rotational loading approximating a walking load. On the initial application of load, axial subsidence was as much as several millimeters for the noncemented stems. Considerable tightering occurred during the 5,000 walking cycles, such that the motion of the noncemented stems in some directions eventually was as small as that of the cemented stem, on the order of tens of microns.