bluuebunny/crossref_metadata_2025 huggingface dataset:
Proteoglycans of human rotator cuff tendons
Authors: Berenson Matthew C. , Blevins Field T. , Plaas Anna H. K. , Vogel Kathryn G.
Published: February 2005

Rotator cuff and biceps tendons that appeared grossly normal were procured from adult cadavers without a history of shoulder problems. These tendons were analyzed for the amount and type of glycosaminoglycan, type of proteoglycan, and histology. When compared with the distal/tensional region of biceps tendon, the glycosaminoglycan content of supraspinatus, infraspinatus, and subscapularis tendons was 2.5‐fold higher and the glycosaminoglycan content of the proximal/compressed region of biceps tendon was 3‐fold higher. The ratio of hyaluronic acid to chondroitin sulfate/dermatan sulfate in all three cuff tendons was approximately 1. Rotator cuff tendons contained large proteoglycan similar to aggrecan, as demonstrated by sodium dodecyl sulfate‐polyacrylamide gel migration, elution from Sepharose CL‐4B, and content of both chondroitin sulfate and keratan sulfate chains. Both decorin and biglycan were also present, as demonstrated by migration in sodium dodecyl sulfate‐polyacrylamide gels and core protein immunoreactivity. In contrast, decorin was the only proteoglycan prominent in distal/tensional regions of biceps tendon. Histological analysis showed layers of loosely organized, alcian blue‐stained material running between the longitudinal collagen fiber bundles. The proteoglycan content of rotator cuff tendons was similar to fibrocartilage in tendons that have been subjected to compressive loads in situ. This suggests that cells of normal adult rotator cuff tendons have adapted to loads distinct from pure tension. However, the histological organization did not resemble mature fibrocartilage. The increased amount of proteoglycan in rotator cuff tendons may serve to separate and lubricate collagen bundles as they move relative to each other during normal shoulder motion.
Comparison of functional deficits in the rabbit tibialis anterior following tourniquet ischemia and tourniquet compression
Authors: Ohara William M. , Pedowitz Robert A. , Oyama Brian K. , Gershuni David H.
Published: February 2005

The purpose of this study was to measure the contractile properties of skeletal muscle after direct compression with a tourniquet and to compare these properties with those found after a similar period of tourniquet ischemia. A rabbit model of tourniquet compression of the tibialis anterior was developed and tested for this investigation. Fifty‐seven animals then were divided into four protocol groups: (a) thigh tourniquet (ischemia) at 350 mm Hg (46.7 kPa), (b) leg tourniquet (compression) at 350 mm Hg (46.7 kPa), (c) leg tourniquet at 125 mm Hg (16.7 kPa), and (d) controls. A significant decrease in maximum tetanic tension was demonstrated in all three experimental groups. Direct compression at 350 mm Hg resulted in the greatest decline in maximum tetanic tension (22.6% of control), followed by compression at 125 mm Hg (30.5% ) and ischemic injury (40.2% ). In addition, direct compression at 350 mm Hg resulted in a significantly greater loss of force‐generating capacity when compared with the ischemic group (p < 0.01). A similar pattern was noted for the rate of rise in maximum tetanic tension. Gross histologic examination of the tibialis anterior sections was consistent with the results of functional testing, with the more severe abnormalities noted in the compressed specimens. These results clearly demonstrate that tourniquet compression injury results in a more significant loss of functional strength and contractile speed than tourniquet ischemia. Further investigations on the safe limits of tourniquet use thus should be directed toward measuring the effect of the pneumatic tourniquet on the underlying soft tissues.
A mechanism for rotation restraints in the knee joint
Authors: Blankevoort L. , Huiskes R.
Published: February 2005

Ligament function in restraining axial rotation of the tibia relative to the femur cannot be revealed by analysis of ligament forces alone. The action of the articular surfaces should be taken into account as well. In this study, three‐dimensional mathematical models of four human knee joints were used to determine the limits of axial rotation between 0 and 90° of flexion, whereby the forces in the ligaments and articular contact were calculated, together with their contribution to the restraint moment that was required to counterbalance the applied axial moment of 3 Nm. In external rotation, the direct axial restraint was provided by the collateral ligaments. In internal rotation, when the cruciate ligaments and medial collateral ligament were predominantly loaded, the direct restraint moment resulting from the ligament forces was not sufficient to counterbalance the applied moment. The articular contact forces, which resulted from balancing the axial components of the ligament forces, contributed considerably to the restraint of internal rotation, Depending on the flexion angle, the contact forces provided approximately 50–50% of the internal restraint, whereas 95–100% of the external rotation restraint was accounted for by the ligament forces.
Relationship between bone growth rate and hypertrophic chondrocyte volume in new zealand white rabbits of varying ages
Authors: Kuhn Janet L. , Delacey Jonathan H. , Leenellett Elizabeth E.
Published: February 2005

The dynamics of longitudinal bone growth are very complex, and potential targets for control could be any one of a number of cells or physiologic processes. Previous studies have demonstrated a linear relationship between hypertrophic cell morphology and bone growth rate in various growth plates and animals. It is unclear whether this relationship varies with age or growth plate. This study tested for significant correlations between mean terminal hypertrophic cell volume and bone growth rate as a function of age and growth plate in the New Zealand White rabbit. Three male rabbits in each of five age groups (2, 3, 5, 8, and 12 weeks old) were used to analyze growth plates from the proximal femur, proximal tibia, and proximal and distal radius. With use of tetracycline labeling and stereological techniques, bone growth rates and hypertrophic chondrocyte volumes were measured. The data were stratified by age and growth plate location and were analyzed using linear regressions. Analyses of covariance were used to test for significant differences. First, there were significant differences due to age. Linear relationships between bone growth rate and hypertrophic chondrocyte volume existed only for the older age groups (all r2 > 0.8), not for the 2 or 3‐week‐old groups. Also, the slope of the relationship was significantly higher in 5‐week‐old rabbits than in the 8 and 12‐week‐old groups, Second, there were significant differences between species. A comparison of the rabbit data with pig and rat data in the literature showed significant differences between all three species. Third, significant differences between growth plates were found. Although hypertrophic chondrocyte volume plays an important role in bone growth, its function may be dependent on age, species, and location.
Effects of postmortem freezing on tensile failure properties of rabbit extensor digitorum longus muscle tendon complex
Authors: Leitschuh Paul H. , Doherty Tammy J. , Taylor Dean C. , Brooks Daniel E. , Ryan John B.
Published: February 2005

The tensile failures of extensor digitorum longus muscle tendon units from 16 male New Zealand White rabbits were studied in the fresh state (less than 30 minutes after death) and in the frozen/thawed state (frozen at −80°C for 28 days and then warmed to 38°C). Frozen/thawed extensor digitorum longus muscle tendon units had significantly lower values for load to failure (p < 0.01), energy absorbed to failure (p < 0.01), and strain at failure (p < 0.01), and they tended to fail at a different anatomic location (p < 0.01) (broadly at the fascia‐muscle interface as compared with horizontally at the musculotendinous junction) than fresh units. The results of this study suggest that freezing muscle tendon units significantly alters their tensile failure characteristics.
Subchondral plate thickness reflects tensile stress in the primate acetabulum
Authors: Dewire Peter , Simkin Peter A.
Published: February 2005

To evaluate possible relationships between body size and articular architecture, femoral head radius and subchondral plate thickness were assessed in skeletal hip joints from normal primates. The relative “contact pressure” on bearing surfaces was estimated from the measured radius and the normal body mass in species ranging from Cebuella pygmaea (0.1 kg) to Gorilla gorilla (170 kg). Subchondral plate thickness was evaluated by computed tomography in species ranging from Cercopithecus neglectus (4.0 kg) to Gorilla gorilla. Neither the “contact pressure” nor the thickness of the femoral subchondral plate varied substantially among species. In contrast, the acetabular subchondral plate thickened significantly (p = 0.01) as body size increased. This finding is interpreted as an osseous response to tensile acetabular stress, which can be expected to increase directly with the radius of curvature.
Prevention of bacterial adherence to implant surfaces with a crosslinked albumin coating in vitro
Authors: An Y. H. , Stuart G. W. , McDowell S. J. , McDaniel S. E. , Kang Q. , Friedman R. J.
Published: February 2005

Titanium surfaces were coated with bovine serum albumin using carbodiimide, a crosslinking agent. The durability of the coated surfaces and the inhibitory effect of the albumin coating on bacterial adherence were tested in vitro for 20 consecutive days at 37°C in phosphate buffered saline, with intermittent agitation. The results showed that only 10% of the coated bovine serum albumin decayed off the surface during the 20‐day incubation period. The inhibition rate of the albumin coating on bacterial adherence remained high (greater than 85% ) throughout the experiment. The results suggested potential use of this crosslinked albumin coating to reduce bacterial adherence and thus the subsequent possibility of prosthetic or implant infection in vivo.
Role of different loading conditions on resorption of hydroxyapatite coating evaluated by histomorphometric and stereological methods
Authors: Overgaard S. , Søballe K. , Josephsen K. , Hansen E. S. , Bünger C.
Published: February 2005

The role of different loading conditions on resorption of plasma‐sprayed hydroxyapatite coating was investigated in an experimental study. Resorption of hydroxyapatite was quantified by histomorphometric and stereological methods on backscattered scanning electron images. Hydroxyapatite‐coated titanium implants were inserted unilaterally into the medial femoral condyle of the knee in 14 mature dogs. Initially, all implants were subjected to controlled micromotion of 150 μm. After 4 weeks, the dogs were randomly assigned either to have the implant surgically immobilized to prevent further micromovement or to have a sham operation. Sixteen weeks after the first operation, the implants were analyzed. Six noninserted implants served as controls. The surface area and volume of the hydroxyapatite coating were reduced on the immobilized implants by 53 and 67% (p < 0.05), respectively, and were further significantly reduced on the continuously loaded implants by 83 and 87%, respectively, compared with the control implants. The hydroxyapatite coating was significantly thinner on immobilized (15 μm) and continuously loaded (15 μm) implants as compared with control implants (23 μm), but no difference between the inserted implants was found. Areas not covered with hydroxyapatite had 29 and 24% bone coverage on the immobilized and continuously loaded implants (not significant). Resorption of hydroxyapatite coating did occur in vivo. Continuous loading of the implants accelerated resorption significantly compared with immobilization of the implants. It is suggested that completely resorbed hydroxyapatite was partly replaced by bone in direct contact with the metal implant surface.
Bone growth after osteotomy and internal fixation in young rabbits
Authors: Albanese Stephen A. , Spadaro Joseph A. , Chase Sharon E. , Geel Christoph W.
Published: February 2005

The factors leading to overgrowth following fixation of long‐bone fractures in children have never been clearly understood. The amount of trauma and the type of fixation may play a role. A rabbit model was used to investigate the influence of a femoral osteotomy and plate fixation on subsequent growth. Unilateral midshaft femoral osteotomy was performed in 6‐week‐old rabbits, and the bone was fixed internally with a plate and screws. End‐to‐end reduction was performed either at full length or with a segment removed. Bone length measurements at the end of growth revealed no significant difference in growth between the control femur and the femur that had undergone osteotomy and plate fixation. Shortened plated femora also showed no tendency to grow longer or faster than full‐length fixed femora or controls. Interestingly, in the ipsilateral tibia a small but statistically significant length increase, equivalent to about 2% increase in additional growth, was observed, whereas technetium‐99 methylene diphosphonate uptake was reduced in the tibial physes. In the context of the rabbit experimental model chosen, these results suggest that significant femoral overgrowth does not occur following femoral osteotomy and plate fixation.
Human anterior and posterior cervical longitudinal ligaments possess similar tensile properties
Authors: Przybylski Gregory J. , Carlin Gregory J. , Patel Prakash R. , Woo Savio L‐Y.
Published: February 2005

One hundred bone‐ligament‐bone complexes were isolated from the cervical spines of 20 fresh‐frozen human cadavers and mechanically tested in uniaxial tension. Load‐elongation curves representing the structural properties of the complex were obtained, and stiffness, ultimate load, energy at failure, and elongation were determined from the curves. Stress‐strain curves representing the mechanical properties of the ligament substance were also obtained, and elastic modulus was determined from these curves. Comparisons were made between anterior and posterior longitudinal ligaments and among cervical levels. The cross‐sectional area of the anterior ligament was smaller at the C2‐C3 level than at subaxial levels. There was a trend toward less stiffness but more energy at failure and greater elastic modulus for the anterior compared with the posterior ligaments at subaxial levels, although the differences were not statistically significant (p > 0.05).
Muscle activation at the human knee during isometric flexion‐extension and varus‐valgus loads
Authors: Buchanan Thomas S. , Lloyd David G.
Published: February 2005

We examined the role of muscles in counteracting static loads in the transverse plane at the knee to determine if (a) knee muscles are activated to counteract isometric varus or valgus loads, (b) muscle activity during varus and valgus loads changes with the angle of knee flexion, and (c) the direction of a muscle's activation can be predicted by its moment arm orientations. For seven subjects, muscle activity was recorded during isometric tasks using surface and intramuscular electrodes from 10 muscles that span the knee. A six‐degree‐of‐freedom load cell was rigidly attached to each subjects lower leg just above the ankle, and the subjects were instructed to push against the load cell so as to produce moments in the flexion‐extension‐varus‐valgus plane at the knee. Moments in this plane were all of equal magnitude and varied in direction the full 360° in 20° increments. Most muscles were not activated to stabilize the knee against varus‐valgus loads, but the sartorius, gracilis, and tensor fasciae latae showed substantial electromyographic activation in these directions. The load directions where muscles were principally active were observed to be dependent on joint angle for some muscles. In particular, the principal directions of activation for these three muscles changed as the angle of knee flexion changed. Similarly, a muscle's moment arm orientation was a good predictor of direction of activation for some muscles and a poor one for others. These results suggest that different muscles may play different roles in providing joint stability and that these roles are complex functions of muscle moment arm orientations, joint angles, external load directions possibly and other undetermined parameters.
Rat model of distraction osteogenesis
Authors: Aronson J. , Shen X. C. , Skinner R. A. , Hogue W. R. , Badger T. M. , Lumpkin C. K.
Published: February 2005

Prior studies of distraction osteogenesis in dog and rabbit models have shown predominantly intramembranous bone formation. Other models of fracture healing normally display mixtures of both endochondral and intramembranous bone formation. We have established a rat model of tibial lengthening that reliably reproduces the pattern of zonal osteogenesis previously observed in dog and rabbit models. A distraction rate of 0.25 mm twice a day with a 0‐day latency period produced intramembranous bone with zones of progressive mineralization from collagen. With this protocol, rats bridged the distraction gap with a 25% increase in the tibial bone length. After 20 days of distraction and 50 days of consolidation, the three‐point bending stiffness, as a percentage of the contralateral control, reached a level equivalent to that measured in the canine model for a 15% lengthening (28‐day distraction and 84‐day consolidation). Radiodensitometric analysis of the regenerate bones measured 97% of the unaffected contralateral tibial densities, and mineral analyses demonstrated that calcium and phosphorus levels in the regenerate bone reached 78% of contralateral tibial levels by day 70. We concluded that a rat model of distraction ostegenesis will be useful for a wide range of studies involving rapid intramembranous bone formation.
Stimulation of bone formation by intraosseous application of recombinant basic fibroblast growth factor in normal and ovariectomized rabbits
Authors: Nakamura Kozo , Kawaguchi Hiroshi , Aoyama Ikuo , Hanada Keigo , Hiyama Yoshiyuki , Awa Takao , Tamura Makoto , Kurokawa Takahide
Published: February 2005

The effect on intraosseous bone formation of a single local injection of recombinant human basic fibroblast growth factor into the distal femur was examined in normal and ovariectomized rabbits. In normal rabbits, basic fibroblast growth factor increased bone mineral density around the injected site in a dose‐dependent manner at 4 weeks, with significant effects at concentrations of 400 μg and greater. Doses of 400 and 1,600 μg of basic fibroblast growth factor increased bone mineral density by 8 and 9%, respectively, compared with the opposite control femur. Histological examination showed that basic fibroblast growth factor (400 μg) induced the proliferation or recruitment of undifferentiated mesenchymal cells around the existing trabeculae at 3 days after the injection. For the first 2 weeks, osteoid formation was strongly stimulated, and this was followed by mineral apposition for another 2 weeks, at which time the femurs were harvested. Consequently, basic fibroblast growth factor stimulated intraosseous bone formation at 4 weeks. We speculate that the direct action of basic fibroblast growth factor on bone formation may be to stimulate proliferation or recruitment of minimally differentiated mesenchymal cells and to initiate the cascade of events in later stages of bone formation. In ovariectomized rabbits, basic fibroblast growth factor (400 μg) also increased bone mineral density, histomorphometrical bone formation markers, and trabecular connectivity to levels similar to those in rabbits who had received sham operations.
Method to impact in vivo rabbit femoral cartilage with blows of quantifiable stress
Authors: Vrahas M. S. , Smith G. A. , Roseer D. M. , Baratta R. V.
Published: February 2005

The purpose of this study was to develop a technique by which a known stress could be applied uniformly across the femoral cartilage of a rabbit as a model for the development of post‐traumatic arthritis. A system to impact the cartilage was designed that consisted of an apparatus to deliver a blow of quantifiable force, a method to apply the stress uniformly over the impact area, and a way to accurately measure the impact area. The knee joints of cadaveric New Zealand White rabbits were surgically exposed with the knee flexed so that the distal femoral articular surface was perpendicular to an impactor. With the knee fixed in, position, a cup containing polymethylmethacrylate bone cement was applied to create an exact contour of the femoral surface, and the cement was allowed to cure. The form was then rested on the rabbit knee, and a drop tower, released a weight of known mass from a known height onto an impactor (instrumented with strain gauges to measure the compressive force) that was attached to the cup. The area of the impacted surface was determined and, with the measured force, was used to calculate an accurate estimate of the impact stress. This method can be performed under sterile conditions, and therefore it is well suited for survival experiments in which the long‐term effects of impact to cartilage will be studied.
Alterations in the mechanical behavior of the human lumbar nucleus pulposus with degeneration and aging
Authors: Iatridis James C. , Setton Lori A. , Weidenbaum Mark , Mow Van C.
Published: February 2005

This study tested the hypothesis that changes in the morphology and composition of the nucleus pulposus with age and degeneration have associated changes in its mechanical properties. A torsional shear experiment was used to determine viscoelastic shear properties of cylindrical samples of human nucleus pulposus with large ranges of grades of morphological degeneration (normal to severely degenerated) and ages (range: 16–88 years; average: 57 ± 21.5 years). Viscoclastic shear properties were determined from stress‐relaxation and dynamic sinusoidal tests. A linear viscoelastic law with a variable‐amplitude relaxation spectrum was used to model experimental behaviors of nucleus pulposus specimens. A statistically significant increase in the instantaneous and dynamic shear moduli was found with increasing age and grade of degeneration; the values for moduli ranged from 5.0 to 60 kPa. A significant decrease in tanδ was also detected; the values ranged from 0.43 to 0.33, indicating a decreased capacity for the nucleus pulposus to dissipate energy. The dynamic modulus and tanδ were also significantly affected by frequency. It was generally concluded that the nucleus pulposus undergoes a transition from “fluid‐like” behavior to more “solid‐like” behavior with aging and degeneration.
Characterization of regional and age‐related variations in the growth of the rabbit distal femur
Authors: Lerner Amy L. , Kuhn Janet L.
Published: February 2005

Fluorochrome labeling and microcomputed tomography were used to completely characterize the regional and age‐related variations in bone growth in the distal femur of the very young rabbit. Use of the microcomputed tomography system, in conjunction with the more routine fluorochrome labeling, allows the investigation of changes in shape that occur during development. The growth plate in the distal femur studied here is remarkable for several reasons. First, growth rates of as much as 700 μm/day were measured, a much higher rate than those typically measured in other species or in more mature animals. In addition, regional variations in bone growth rates of as much as 300 μm/day were identified in the 6‐week‐old rabbit. These variations resulted in the formation of a complex curvature in the growth plate, including four mammillary processes. Identifying the factors that regulate this type of regional variation may be especially useful in understanding the causes for angular deformities such as tibia vara or developmental dysplasias.
Acute effects of periarterial sympathectomy on the cutaneous microcirculation
Authors: Pollock David C. , Li Zhongyu , Rosencrance Eileen , Krome Jonathan , Koman L. Andrew , Smith Thomas L.
Published: February 2005

The clinical effects of peripheral sympathectomy on patients with vaso‐occlusive disease are often dramatic and include relief of pain, improved quality of life, and healing of ulcers. Peripheral periarterial sympathectomy is known to increase skin temperature and to maximize the nutritional component of peripheral blood flow, but the pathophysiology of vaso‐occlusive disease and the physiologic mechanisms of this treatment are unknown. In this study, the acute effects of periarterial sympathectomy were directly observed in a rabbit ear model of digital microcirculation (arterioles, arteriovenous anastomoses, and venules). The effects of periarterial sympathectomy on cutaneous perfusion and total flow were also examined using laser Doppler. Perfusion imaging and digital temperature measurements. The central auricular artery became dilated (50–100%) immediately after sympathectomy; the arterioles, arteriovenous anastomoses, and venules dilated to 165,156, and.223%, respectively, at 30 minutes and to 187,174, and 204%, respectively, at 60 minutes, relative to their baseline diameters prior to sympathectomy. Laser Doppler perfusion imaging values and ear temperatures were noted to increase after sympathectomy (8.9%, 3°C), although the core temperature of the rabbit did not change. Thus, acute periarterial sympathectomy can (a) effectively reduce the vascular tone of the distal microvasculature and (b) increase total microcirculatory perfusion—cutaneous and thermoregulatory—by both venular and arteriolar dilation. Periarterial sympathectomy has the clinical potential to increase nutritional blood flow, thereby ameliorating the signs and symptoms of ischemia associated with thermoregulatory abnormalities. Dilation of the arteriovenous anastomoses, with a subsequent reduction in vascular resistance, may contribute to the increased cutaneous temperature noted after sympathectomy.
Age‐related decline in chondrocyte response to insulin‐like growth factor‐I: The role of growth factor binding proteins
Authors: Martin James A. , Ellerbroek Shawn M. , Buckwalter Joseph A.
Published: February 2005

The synthetic activity of chondrocytes in articular cartilage declines with age, possibly as a result of decreased sensitivity to anabolic growth factors such as insulin‐like growth factor‐I. The sensitivity of these cells to insulin‐like growth factor‐I is regulated, in pan, by the synthesis of insulin‐like growth factor‐I binding proteins. We hypothesized that, as cartilage ages, an increase in the expression of these binding proteins suppresses the synthetic response of chondrocytes to insulin‐like growth factor‐I, To test this hypothesis, we measured proteoglycan synthesis (incorporation of [35S]sulfate per cell) in alginate cultures of chondrocytes from the articular cartilage of 1,3, 12, and 24‐month‐old rats. A dose‐response to insulin‐like growth factor‐I was determined for cells from each age group; incorporation of [35S]sulfate per cell declined with age, regardless of the dose. The sharpest decline was found between cells from the 1 and 3‐month‐old groups. Using the Western ligand b ot technique, we then compared the expression of insulin‐like growth factor‐1 binding protein in chondrocytes from the 1 and 3‐month‐old rats and found that it was increased in the cells from the older animals. Recombinant insulin‐like growth factor‐3, when added to the cell cultures of the 1‐month‐old rats, inhibited incorporation of [35S]sulfate and blocked responses to insulin‐like growth factor‐I. These findings suggest that the age‐related decline in the synthetic response of chondrocytes to insulin‐like growth factor‐I results, at least in part, from increased expression of insulin‐like growth factor binding protein.
Depth‐dependent confined compression modulus of full‐thickness bovine articular cartilage
Authors: Schinagl Robert M. , Gurskis Donnell , Chen Albert C. , Sah Robert L.
Published: February 2005

The objective of this study was to determine the equilibrium confined compression modulus of bovine articular cartilage as it varies with depth from the articular surface. Osteochondral samples were compressed by 8, 16, 24, and 32% of the cartilage thickness and allowed to equilibrate. Intratissue displacement within the cartilage was measured with use of fluorescently labeled chondrocyte nuclei as intrinsic, fiducial markers. Axial strain was then calculated in nine sequential 125 m̈m thick cartilage layers comprising the superficial 1,125 m̈m and in a 250 m̈mm thick layer of cartilage adjacent to the cartilage‐bone interface. Adjacent osteochondral cores were also tested in confined compression to determine the equilibrium stresses required to achieve the same levels of compression. Stress‐strain data for each layer of each sample were fit to a finite deformation stress‐strain relation to determine the equilibrium confined compression modulus in each tissue layer. The compressive modulus increased significantly with depth from the articular surface and ranged from 0.079 ± 0.039 MPa in the superficial layer to 1.14 ± 0.44 MPa in the ninth layer. The deepest layer. 250 m̈m thick, had a modulus of 2.10 ± 2.69 MPa. These moduli were markedly different from the apparent “homogeneous” modulus for full‐thickness cartilage (0.38 ± 0.12 MPa) and ranged from 21 to 560% of that value. The relatively low moduli and the compression‐induced stiffening of the superficial layers suggest that these layers greatly affect the biomechanical behavior of cartilage, such as during confined compression testing. The delineation of the depth‐dependent modulus provides a basis for detailed study of the relationship between the composition, structure, and function of cartilage in such processes as aging, repair, and degeneration.
Oxygen consumption of calvarial bone cells in vitro
Authors: Schirrmacher K. , Lauterbach S. , Bingmann D.
Published: February 2005

Tissues with tortuous and narrow diffusion pathways and cells that are remote from blood vessels nonetheless can show high metabolic activity of which the underlying bases (transport mechanisms) are not fully understood. In one such bone tissue, the O2 consumption was measured by analyzing the decrease in the partial pressure of oxygen (PO2) in a closed chamber containing calvarial fragments from adult guinea pigs (250–400 g) or from neonatal rats and guinea pigs. The O2 consumption of fragments from adult guinea pigs amounted to 0.05. 0.066, and 0.095 ml/100 g * minute at 24. 27, and 36.5°C, respectively. When the temperature exceeded 43°C, O2 consumption irreversibly stopped. Both antimycin A and rotenone, which block the respiratory chain, reduced O2 consumption to approximately 20% of control values. O2 consumption was significantly higher in neonatal animals (0.369 ml/100 g * minute at 27°C) and could be blocked completely by antimycin A. On the basis of the high consumption of O2 by bone cells. we hypothesize that specialized transport systems, i.e., gap junctions, are required to provide a sufficient supply of nutrients to cells in osseous tissue.
Selective ablation of rat knee joint innervation with injected immunotoxin: A potential new model for the study of neuropathic arthritis
Authors: Salo Paul T. , Theriault Elizabeth , Wiley R. G.
Published: February 2005

Neuropathic arthropathy is a severe chronic degenerative condition associated with decreased or absent I sensory innervation of the involved joint. Existing animal models of neuropathic arthritis are limited by the technical difficulties of obtaining either highly selective or complete joint denervation in a minimally invasive fashion. We undertook experiments to determine the feasibility of using the newly described method of selective neuronal lesioning with injected immunotoxin as a means of creating a more tractable model of neuropathic arthritis. Retrograde tracing with fluorochrome revealed that the knee joint of the female Wistar rat is supplied by 581 ± 31 (mean ± SD) joint afferents. Immunohistochemistry confirmed that virtually all sensory neurons in the rat express the cell surface receptor Thy I. Injection of rat knee joints with an immunotoxin targeted toward Thy 1 resulted in the selective ablation of an average of 88% of the joint afferents identified with fluorochroime that are normally found in the ipsilateral L3 and L4 ganglia.
Primary immunolocalization of androgen target cells in the human anterior cruciate ligament
Authors: Hamlet Ward P. , Liu Stephen H. , Panossian Vaché , Finerman Gerald A. M.
Published: February 2005

To identify androgen target cells in the human anterior cruciate ligament, immunohistochemical localization of the androgen receptor was performed in 31 specimens of the ligament. All of the specimens were obtained at surgery. Seventeen specimens were from women, and 14 were from men; the average age of the patients was 45.2 years (range: 18–78 years). An immunoperoxidase method using monoclonal antibodies to the androgen receptor was employed to identity androgen target cells in the ligament. Consistent staining of the androgen receptor was demonstrable in six specimens obtained from young men 18–24 years old, and equivocal positive staining was seen in two other specimens from young men. No receptors were demonstrated by this method in any of the specimens from women or older men. Androgen receptors were localized to synoviocytes in the synovium and under the synovial lining, fibroblasts in the ligament stroma, and cells lining the blood‐vessel walls of the anterior cruciate ligament. The demonstration of androgen receptors in the cells of the anterior cruciate ligament strongly suggests that male sex hormones may have an effect on the structure and composition of this ligament in young men.
Influence of stem geometry on mechanics of cemented femoral hip components with a proximal bond
Authors: Mann Kenneth A. , Bartel Donald L. , Ayers David C.
Published: February 2005

Nonlinear, three‐dimensional, finite element models of cemented femoral hip components with a proximal stem‐Cement bond were developed with use of a Charnley stem geometry and a modified Charnley stem geometry that had a cylindrical cross section over the distal two‐thirds of the stem (Distal‐Round). Peak tensile stresses in the proximal cement mantle increased 63 and 74% for the Charnley and Distal‐Round stems, respectively, when the proximal stem‐cement interface was debonded, The shear stresses over the stem‐cement interface with a proximal bond were 29%. larger for the Distal‐Round stem than for the Charnley stem. After the proximal stem‐cement interface was debonded. the peak tensile stresses in the cement mantle were 15% larger for the Distal‐Round stem than for the Charnley stem. The results illustrate that stresses within the proximal cement mantle could be substantially reduced for both Charnley and Distal‐Round stems through use of a proximal stem‐cement bond. However, the risk of debonding may be higher for the Distal‐Round stem because of increased shear stresses, and once debonded the risk of further loosening due to failure of the cement mantle would also be higher for the Distal‐Round stem.
Laxity and flexibility of the ankle following reconstruction with the Chrisman‐Snook procedure
Authors: Tohyama Harukazu , Beynnon Bruce D. , Pope Malcolm H. , Haugh Larry D. , Renström Per A.
Published: February 2005

The effect of reconstruction of the anterior talofibular ligament with the Chrisman‐Snook procedure on neutral zone laxity (anterior‐posterior displacement at low loads) and flexibility (a measure of the nonlinear load‐displacement response) of the ankle was investigated in vitro during the anterior drawer test. Neutral zone laxity was defined as the magnitude of anterior‐posterior displacement of the ankle joint at ±2.5 N of applied load. The flexibility parameter was defined as the slope of a line between the natural logarithm of the anterior load applied to the ankle and the resulting displacement. After reconstruction with the Chrisman‐Snook procedure, the values for neutral zone laxity of the ankle were significantly less than normal at 0° of plantar flexion, whereas the flexibility values were significantly greater than normal. This study revealed that, after the Chrisman‐Snook procedure, values for ankle flexibility are not restored to normal even if those for neutral zone laxity are reduced to less than normal. The findings suggest that this nonanatomical reconstruction procedure does not reproduce normal kinematics of the ankle joint. This may help explain some of the adverse clinical reports associated with the Chrisman‐Snook reconstruction procedure.
Degeneration at the insertion weakens the tensile strength of the supraspinatus tendon: A comparative mechanical and histologic study of the bone‐tendon complex
Authors: Sano Hirotaka , Ishii Hirotada , Yeadon Alan , Backman David S. , Brunet Jacques A. , Uhthoff Hans K.
Published: February 2005

The purpose of this investigation was to determine the relationship between the degree of degeneration at the supraspinatus insertion, the tensile strength, and the site of failure of this tendon. Thirty‐three fresh cadaveric shoulders (average age: 62 years; range: 39‐83 years) were examined. A tensile load to failure was applied at a constant crosshead speed of 25.4 mm/min to a 10 mm wide strip of the supraspinatus tendon that remained attached to the bone. Preexisting degenerative changes at the insertion were assessed and scored histologically and compared with the ultimate tensile stress. Twenty tendons failed at the insertion (the insertion group), and 11 failed in the midsubstance (the midsubstanee group). The histologic score of degeneration for the insertion group was significantly higher than that for the midsubstance group (p = 0.0026). There was a negative correlation between the ultimate tensile stress at the insertion and the degeneration score for the insertion group (r = −0.60; p = 0.013). Histologic observations revealed that disruptions of tendon fibers were located mostly in the articular half of the tendon and that they enlarged during mechanical testing in 90% of the specimens of the insertion group. It seems that degenerative changes at the supraspinatus insertion reduce the tensile strength of the tendon and constitute a primary pathogenetic factor of rotator cuff tear.
Radial tensile properties of the lumbar annulus fibrosus are site and degeneration dependent
Authors: Fujita Yoshi , Duncan Neil A. , Lotz Jeffrey C.
Published: February 2005

We conducted an in vitro study of the radial tensile properties of the annulus fibrosus. The stress‐strain response was nonlinear, with a mean tangent modulus of 0.19 MPa at zero strain and 0.47 MPa at 70% of the yield strain. We also investigated whether these properties varied as a function of location within the disc and degree of degeneration. Specimens harvested from the middle layers of the annulus were stiffer and failed at smaller strain magnitudes than those from the inner or outer annulus (analysis of covariance, p <0.05). Differences due to degeneration were evident; degenerated discs had a 30% decrease in yield and ultimate stress compared with normal discs. Similarity between our data and those reported for the annulus in compression suggests that these values reflect the material behavior of the interlaminar matrix and are an order of magnitude smaller than values used in previous analytical representations of this tissue. We expect that awareness of these data will result in improved understanding of the physical behavior and tolerance to injury of the annulus fibrosus.
Microhardness and anisotropy of the vital osseous interface and endosseous implant supporting bone
Authors: Huja S. S. , Katona T. R. , Moore B. K. , Roberts W. E.
Published: February 2005

Limited information is available on the mechanical properties of the rapidly remodeling bone that surrounds endosseous implants. Fifteen implant‐bone blocks were obtained from the mid‐femoral diaphyses of three mature male hounds 12 weeks after placement of the implants. To evaluate the microhardness and cortical anisotropy of bone, the implants were sectioned along their long axes. In this process, the femurs were sectioned transversely. Knoop microhardness measurements (HK) were made with a 50 g force on cortical bone and a 25 g force on periosteal callus, endocortical callus, and circumferential lamellar bone. The long diagonal of the indenter was placed parallel to the implant (in the radial bone direction). Measurements were made in cortical bone at 200, 400, 600, 800, 1,000. 1,500. 2,000. and 2,500 μm from both sides of the implant. To detect cortical anisotropy in the radial compared with the tangential direction, a second set of indentations was made perpendicular to the first. Microhardness of periosteal callus and endocortical callus and anisotropy of circumferential lamellar bone near the endocortical surfaces of the femur were also evaluated. Repeated measures analysis of variance showed significantly (p < 0.05) lower microhardness values (30.6 ± 0.8 HK [mean ± SEM]) for cortical bone at 200 μm than at any other location (range: 40.3–46.6 HK). Microhardness anisotropy was not detected in cortical bone. Furthermore, within 200 μm of the implant surface, the Knoop microhardness values were significantly lower for periosteal and endocortical calluses than for cortical bone. These data provide information about the mechanical properties of bone adjacent to endosseous implants at a microstructural level. The results are consistent with the high rate of remodeling seen adjacent to endosseous implants at 12 weeks after implantation.
Use of a bioabsorbable polymer for the delivery of ofloxacin during experimental osteomyelitis treatment
Authors: Nie Lin , Nicolau David P. , Tessier Pamela R. , Kourea Helen P. , Browner Bruce D. , Nightingale Charles H.
Published: February 2005

This study was performed to investigate the potential utility of ofloxacin‐impregnated bioabsorbable polymers for osteomyelitis therapy. Pseudomonas aeruginosa osteomyelitis was induced in 48 New Zealand White rabbits Four weeks after infection, the animals were randomized to one of four treatment groups: drug‐free polymer, ofloxacin polymer, systemic ofloxacin, or ofloxacin polymer plus systemic ofloxacin. Twentyeight days later, radiographs were taken of the affected area, the animals were killed, and bone was obtained for histoloeic evaluation. culture. and determination of ofloxacin concentrations. The percentage of sterile bone cultures was 33, 83, 75, and 91 for the groups treated with drug‐free polymer, ofloxacin polymer, systemic ofloxacin, and ofloxacin polymer plus systemic ofloxacin, respectively. When compared with the drug‐free polymer, both the ofloxacin polymer and the ofloxacin polymer plus systemic ofloxacin significantly improved the rate of sterilization. The mean concentrations of the drug in bone for the groups treated with ofloxacin polymer, systemic ofloxacin, and ofloxacin polymer plus systemic ofloxacin were 34.9 (range: 2–160), 1.9 (range: 0.8–3), and 26.0 μg/g (range: 9–100 μg/g), respectively. These data suggest that the DL‐lactide:glycolide polymer studied is a suitable vehicle for the delivery of high local concentrations of ofloxacin and that these concentrations result in eradication of the bacterial pathogen in this rabbit model.
Adenosine 5′‐triphosphate, uridine 5′‐triphosphate, bradykinin, and lysophosphatidic acid induce different patterns of calcium responses by human articular chondrocytes
Authors: Koolpe Mitchell , Rodrigo Juan J. , Benton Hilary P.
Published: February 2005

Small calcium‐mobilizing inflammatory mediators have been implicated in joint pathology. Here we demonstrate that bradykinin, adenosine 5′‐triphosphate, uridine 5′‐triphosphate, and lysophosphatidic acid raise the intracellular calcium concentration ([Ca2+]i) in human articular chondrocytes. Heterologous cross‐desensitization experiments showed that the uridine 5′‐triphosphate response was abolished by prior treatment with adenosine 5′‐triphosphate and conversely, that the adenosine 5′‐triphosphate response was abolished by prior treatment with uridine 5′‐triphosphate: this indicated competition for the same receptor site, whereas bradykinin and lysophosphatidic acid did not compete with other ligands. Pretreatment with thapsigargin abolished ligand‐mediated Ca2+ responses but not vice versa: this confirmed that Ca2+ release occurred from intracellular stores. Single‐cell analysis of Fura‐2 acetoxymethyl ester loaded chondrocytes showed mediator‐dependent patterns of oscillatory Ca2+ changes in a subset of cells when challenged with submaximal concentrations of bradykinin, adenosine 5′‐triphosphate, or uridine 5′‐triphosphate in the presence of extracellular Ca2+. However, no oscillatory responses were seen after a challenge with lysophosphatidic acid. Therefore, although a number of different Ca2+‐mobilizing ligands activate chondrocytes, the differences that occur in the temporal patterning of Ca2+ responses may result in unique mediator‐dependent changes in cellular activity.
Immunohistochemical detection of activin A, follistatin, and activin receptors during fracture healing in the rat
Authors: Nagamine Tomonori , Imamura Takeshi , Ishidou Yasuhird , Kato Mitsuyasu , Murata Fusayoshi , Dijke Peter ten , Sakou Takashi
Published: February 2005

Activins are multifunctional proteins that belong to the transforming growth factor‐β superfamily and are thought to play an important role in modulating the formation of bone. Activins exert their cellular effects by way of activin type‐I and type‐II serine/threonine kinase receptors. Follistatin is an activin‐binding protein that can suppress the biological effects of activins. In this study, the immunohistochemical expression of activin A, follistatin, and activin receptors was studied during fracture healing in the rat. Activin A was weakly detected in the periosteum near the fracture ends at an early stage but was absent in the chondrocytes around the fracture gap, where endochondral ossification took place. An antibody to follistatin stained osteogenic cells in the periosteum near the fracture ends; moderate and strong staining were observed in proliferating, mature, and hypertrophied chondrocytes at the sites of endochondral ossification. Levels of activin A and follistatin were high near the posteoblasts on the surface of the newly formed trabecular bone. In addition, an intense localization of activin A was noted where multinucleated osteoclast‐like cells were present. This study suggests that the activin‐follistatin system may contribute to cellular events related to the formation and remodeling of bone during fracture healing. Activin type‐I and type‐II receptors were co‐expressed in intramembranous and endochondral ossification sites. The expression of activin type‐I, type‐II, and type‐IIB receptors in the absence of activin A in the endochondral ossification suggests that other isoforms of activins may signal by way of these receptors.