bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunofluorescent localization of structural collagen types in endochondral fracture repair
Authors: Lane Joseph M. , Suda Marilyn , von der Mark Klaus , Timpl Rupert
Published: February 2005

A nonimmobilized rat tibial fracture model of endochondral osseous repair was examined for the unique localizations of specific collagen genetic types. At various stages of the healing process, the demineralized callus was reacted with immunofluorescent antibodies directed against the type specific forms of matrix collagen. Type III collagen rapidly appeared (day 8–10) and remained in the primitive mesenchymal callus until remodeled. It was particularly prominent in the highly vasoformative regions and the pericallus encapsulation but not present in preexisting cortical and neoformed lamellar bone. The type II collagen, a marker of cartilage, was uniquely located only in areas of chondroid differentiation and calcification. Type II collagen was absnet from all bone and was not identified beneath the repairing intact periosteum. The differentiating chondrocytes synthesized type II collagen on an underlayer of type III collagen already within the mesenchymal matrix. From these studies of genetically unique collagen markers, it appears that only in areas of motion or anoxia does an intermediate of chondroid tissue appear. The utilization of specific type II and type III collagen immunofluorescent antibodies has facilitated the understanding of the fracture repair process and has acted as an indicator for unique matrix components.
Effect of hyperbaric oxygen exposure on oxygen tension within the medullary canal in the rabbit tibial osteomyelitis model
Authors: Esterhai John L. , Clark James M. , Morton Harry E. , Smith David W. , Steinbach Andrew , Richter Susan D.
Published: February 2005

The effect on intramedullary oxygen tension of 100% oxygen exposure at 1, 2, 2.4, and 3 atm pressure was studied in 12 New Zealand white rabbits with chronic right tibial osteomyelitis. The model, modified from that described by others, incorporates a multipuncture silastic closure plug placed transcortically in the proximal tibial metaphysis through which platinum needle, polarographic electrode oxygen tension determinations can be made without repeat surgical exposure. In 40% of the control, left, noninfected tibial metaphyses the baseline oxygen tension with the animals breathing room air at sea level was suboptimal for leukocyte bacterial killing. This oxygen tension was depressed further in the infected right tibia. Medullary canal oxygen tension increased in response to hyperbaric oxygen exposure in both the infected and noninfected tibiae. Whereas the amount of the oxygen tension increase varied with the presence of infection and depth of dive, neither the time for oxygen tension to plateau nor the time required for return to baseline tension after completion of hyperbaric oxygen exposure varied with the presence of infection or depth of dive. After completion of hyperbaric oxygen exposure, the oxygen tension within the medullary canal returned to baseline within 15 min.
Effects of mechanical and osmotic pressure on the rate of glycosaminoglycan synthesis in the human adult femoral head cartilage: An in vitro study
Authors: Schneiderman R. , Keret D. , Maroudas A.
Published: February 2005

We studied the effects of mechanical and osmotic compression on sulphate incorporation into glycosaminoglycans of human femoral head cartilage. We found that both mechanical and osmotic compression produce the same lowering of sulphate uptake relative to uncompressed controls. It appears that this effect is not associated with changes in solute transport or changes in solute concentration in the matrix, but is due, in part at least, to an increased osmotic pressure acting on the chondrocytes. A second mechanism of action might be involved directly through the increased proteoglycan concentration in the pericellular environment, resulting from a reduction in the water content. We also found that glycosaminoglycan synthesis returned to its control level when the conditions prevailing in the matrix, in the absence of pressure or added solute, were restored.
Pathogenesis of osteochondrosis juvenilis scheuermann
Authors: Aufdermaur M. , Spycher M.
Published: February 2005

In osteochondrosis juvenilis Scheuermann, foci of various sizes in the cartilaginous end plates of the vertebral bodies display a loosening or complete interruption of the collagen fibers. These findings, together with an alteration and occasional absence of the growth zone, may result in the typical deformation of the vertebral bodies. Electron micrographs of the areas with optically absent collagen fibers reveal collagen fibrils. They are arranged in an irregular pattern. We conclude that a disturbance of collagen or ground substance biosynthesis is of importance in the pathogenesis of juvenile osteochondrosis.
A compliant interface for total knee arthroplasty
Authors: Miegel R. E. , Walker P. S. , Nelson P. C. , Inadomi J. , Needelman L. , Maxine M.
Published: February 2005

Low pressure sensitive Fujifilm was used to measure the load distribution between the resected tibial surface and a tibial component at axial loads up to 3,000 N for a rigid interface, a compliant interface of dacron double‐sided velour, and a cemented interface. The pressure patterns consisted of a multitude of small red dots, generally reflecting the slight irregularities of the cut surface and the stiffness of the cancellous bone at the surface. The pressure patterns were photographed with high‐contrast film and input into a computer using a photodiode matrix camera. The data were analyzed to yield the number of contact points for each sample. The velour was more effective in distribution of load to the proximal tibia than the rigid and cemented interfaces, while there was no significant difference between the cemented interface and the rigid interface. A second series of tests showed significant increases in contact points from rigid to one layer to two layers of velour. Cyclic axial loading tests were performed to study the characteristics of rigid and compliant interfaces in a model of in vitro subsidence. Static pressure patterns taken at regular intervals showed that subsidence occurred in vitro in up to ⅓ of the tibias, and that the regions of load transfer could change with time. A model of subsidence was proposed and it was suggested that a velour layer could inhibit the subsidence.
Indium‐111 leukocyte scintigraphic detection of subclinical osteomyelitis complicating delayed and nonunion long bone fractures: A prospective study
Authors: Esterhai John L. , Goll Stephen R. , McCarthy Kevin E. , Velchik Michael , Alavi Abass , Brighton Carl T. , Heppenstall R. Bruce
Published: February 2005

Twenty patients were studied prospectively with indium‐labled leukocyte imaging to evaluate its effectiveness in differentiating noninfected delayed or nonunion from osteomyelitis complicating these entities. All patients underwent an open surgical procedure within 24h of the scan. Bone specimens from the nonunion site were obtained for microbiological and histological analysis to confirm the presence or absence of osteomyelitis. In these twenty patients, the sensitivity of the indium scintigraphy was 100%, the specificity 100%, and the overall accuracy 100%. Indium‐labeled leukocyte scintigraphy is significantly more accurate than 99mtechnetium and 67gallium imaging had been, when studied earlier, in detecting subclinical osteomyelitis complicating nonunion. Indium‐labeled leukocyte scintigraphy should supplant sequential technetium and gallium studies in this patient population when the surgeon must determine whether subclinical osteomyelitis is complicating fracture management of delayed and nonunions.
Biochemical characterization of fracture callus proteoglycans
Authors: Kopman C. R. , Boskey A. L. , Lane J. M. , Pita J. C. , Eaton B.
Published: February 2005

The changes in proteoglycan molecules during the initial stages of fracture healing in rats were characterized. Following extraction of callus proteoglycan components with dissociative solvents, the components were purified in a cesium chloride density gradient. The recovered proteoglycans were characterized with respect to their molecular size distribution using gel filtration chromatography and a centrifugal transport methodology. During this early healing period, a decrease was observed in the relative proportion of the aggregate and in the hydrodynamic size and sedimentation coefficients of these molecules. While some molecular degradation could have occurred during the early stages of fracture healing, the dominant change of the proteoglycan molecules seemed to be disaggregation. No significant difference was observed in the proportion of aggregates reformed when exogenous hyaluronate and link glycoproteins. The molecular changes of the proteoglycan molecules seem to parallel those occurring during endochondral calcification of rat epiphyseal cartilage.
Influence of stable fixation on trabecular bone healing: A morphologic assessment in dogs
Authors: Uhthoff Hans K. , Goto Sumio , Cerckel Paul‐Henri
Published: February 2005

The healing patterns of trabecular bone are different from those of compact bone. In order to investigate further this observation, a histomorphometric assessment was undertaken. The influence of internal fixation devices on trabecular bone healing was also studied. Intercondylar osteotomies were produced in 19 dogs and fixed with screws. All dogs were killed between 1 and 14 weeks; eight of them had the screws removed 4 weeks after osteotomy and were killed 4 or 10 weeks later. The results of morphometry were compared to the histologic and radiologic pictures. Anatomic reduction with stable fixation led to contact healing characterized by a narrow endosteal bone formation at the osteotomy site that disappeared only after union was complete (4 weeks). In gap healing, the endosteal bone formation was greater. Internal fixation devices appeared to cause a diffuse osteopenia once union was complete. Their removal just after completion of union seems to prevent the bone loss. Screws induced bone formation around their threads; after they were removed, the reaction disappeared but the screw holes were not filled with normal trabeculate 10 weeks later. Union of fractures through trabecular bone can be assessed radiologically. A decrease of band‐like bone density at the fracture site indicates completion of union. This is the optimal time for implant removal. It prevents the osteopenia observed in cases of continuous presence of screws.
Controlled bending instability in the healing of diaphyseal osteotomies in the rat femur
Authors: Mølster Anders O. , Gjerdet Nils R. , Langeland Norvald , Lekven Jon , Alho Antti
Published: February 2005

Ninety‐six rats underwent a midshaft transverse osteotomy followed by osteosynthesis with an intramedullary nail, so that the effect of bending instability on time to union and on the mechanical properties of experimental diaphyseal fracture could be evaluted. Rotation was reduced by cementing both nail ends to the bone. Rigid nails made of stainless steel were used on one group and flexible nails made of polyacetal resin were used on another group. Serial radiographs were evaluated at 4‐6‐week intervals. Twelve animals with either nail type were killed at 4, 8, 16, and 24 week. Both femora were mechanically tested and the callus diameters were measured. There was no significant difference in time to union between the two groups. The cross‐sectional area of callus was significantly higher at 8 and 16 weeks in femora with flexible nails. The strength, toughness, and resilience of the bone increased in this group until 24 week. Between 16 and 24 weeks, these parameters did not improve in femora with rigid nails. Poorer mechanical properties in femora with steel nails are interpreted as an effect of stress protection of the bone. This study, therefore, indicates that flexible nails prevent stress protection effects without delaying union.
Viscoelastic properties of proteoglycan solutions with varying proportions present as aggregates
Authors: Hardingham T. E. , Muir H. , Kwan M. K. , Lai W. M. , Mow V. C.
Published: February 2005

Monomer and aggregated proteoglycans were prepared from piglaryngeal cartilage. Vascoelastic flow properties, comprising linear complex dynamic shear modulus, nonlinear steady‐state shear‐rate dependent viscosity, and primary normal stress difference, were measured in proteoglycan solutions containing varying proportions of aggregate (0–80%) and at different concentrations (10–50 mg/ml). Results were analyzed using the simple Oldroyd four‐parameter nonlinear rate‐type rheological equation. All solution properties were strongly dependent on proteoglycan concentration and on the proportion of aggregates present. Aggregation was found to have a great effect on the zero shear‐rate viscosity at 50 mg/ml, which increased fivefold from 0–100% aggregate. The results showed that network formation in proteoglycan solutions increased with concentration from 10–50 mg/ml and also increased with aggregation. All proteoglycan solutions showed shear thinning, which was most marked with aggregated proteoglycan at high concentration (50 mg/ml), where the viscosity decreased tenfold from the zero shear‐rate limit to the infinite shear‐rate limit. The intermolecular interactions in the network were therefore increasingly disrupted by increasing shear rate, but repeated measurements showed that these were reversible changes and that testing did not induce disaggregation or degradation of proteoglycan. These rheological properties show that aggregation is likely to immobilize proteoglycan at high concentration within cartilage and to contribute to the material properties of the porous solid matrix of articular cartilage that are important for its load‐bearing function.
Cytosolic calcium concentration in bovine growth plate chondrocytes
Authors: Star Andrew M. , Iannotti Joseph P. , Brighton Carl T. , Armstrong Peter F.
Published: February 2005

The cytosolic free calcium ion concentration for mammalian cell systems is believed to be maintained within a narrow range compatible with cellular homeostasis. Growth plate chondrocytes have been shown to accumulate large quantities of calcium within their mitochondria, but the cytosolic free calcium concentration has not been determined. This study measures the cytosolic free ionic calcium concentration in growth plate chondrocytes using two variations of the Quin II fluorescence technique. The results indicate that in isolated growth plate chondrocytes, the cytosolic free ionic calcium concentration is similar to other nonmineralizing mammalian cell types (106–137 nM).
Experimental study on the repair of full thickness articular cartilage defects: Effects of varying periods of continuous passive motion, cage activity, and immobilization
Authors: Shimizu Tomio , Videman Tapio , Shimazaki Kazuhisa , Mooney Vert
Published: February 2005

In order to clarify the dose/response characteristics of continuous passive motion (CPM), the repair response of full thickness articular cartilage defects was studied in a rabbit model. The following combinations of CPM and immobilization, 16 h/day; (3) CPM, 2 h/day and Imm 22 h/day; (4) Imm 24 h/day; and (5) normal cage activity. These regimens were used only in the initial week and then all rabbits were permitted to move freely in their cages, except for a sixth Imm‐CPM group that was kept immobilized in the initial week and then CPM 24 h/day for another week. The CPM 24 h/day and the CPM 8 h/day groups (groups 1 and 4, respectively) showed better repair than the other groups, i.e., better surface congruity, larger positive Safranin‐O staining area, and greater number of chondrocytes in the repair tissue. The CPM 2 h/day group (group 3), however, showed only slightly better repair than the Imm group (group 4). The CPM following immobilization was not effective to overcome the harmful effect of immobilization. We conclude that in the present model, CPM for 8 or 24 h/day is effective for adequate cartilage repair even with some component of immobilization. Its application should be at least 8 h/day. On the contrary, if CPM is delayed for a week following immobilization, the effect of CPM on cartilage will be reduced.
Osteoregulatory nature of mechanical stimuli: Function as a determinant for adaptive remodeling in bone
Authors: Rubin Clinton T. , Lanyon Lance E.
Published: February 2005

The capacity for functional adaptation within the skeleton was studied using the functionally isolated turkey ulna preparation. The results of this study would suggest that adaptive bone remodeling is extremely sensitive to alterations in both the magnitude and distribution of the strain generated within the bone tissue. At present, it appears that a loading regime can only influence bone remodeling when it is dynamic in nature. The full osteogenic potential of its influence is then achieved after only an extremely short exposure to this stimulus. The potency of the stimulus appears to be proportional to the magnitude of the strain engendered. As strain levels that are acceptable in one location induce adaptive remodeling in others, it would appear that each region of each bone is “genetically programmed” to accept a particular amount and pattern of intermittent strain as “normal.” Deviation from this “optimal strain enviroment” will stimulate changes in the bone's remodeling balance, resulting in adaptive increases or decreases in its mass.
Experimental vascularized bone grafts: Histopathologic correlations with postoperative bone scan: The risk of false‐positive results
Authors: Shaffer J. W. , Field G. A. , Wilber R. G. , Goldberg V. M.
Published: February 2005

A positive bone scan in an experimental model of bilateral ulna diaphyseal bone grafts demonstrated early bone repair in both vascularized and nonvascularized orthotopic ulna autografts. A positive bone scan did not correlate with the perfusion of the vascularized and nonvascularized grafts as measured by microangiograms done 1 week postoperatively. In this model, if the bone scan is intended to monitor the circulatory status and viability of the bone graft, it must be done earlier than 1 week postoperative prior to the onset of creeping repair in both vascularized and nonvascular ulna autografts.
Valgus stability of the elbow
Authors: Hotchkiss Robert N. , Weiland Andrew J.
Published: February 2005

The valgus stabilizers of the elbow have been identified anatomically, but their relative importance has not been quantified. The purpose of this study was to analyze the acute changes of the torque‐displacement curve to valgus stress following (a) section of the posterior portion of the medial collateral ligament; (b) excision of the radial head; (c) prosthetic replacement of the radial head; and (d) excision of the anterior portion of the medical collateral ligament. Thirty cadaver specimens underwent load‐displacement testing in three positions: 0°, 45°, and 90° of flexion. The anterior portion of the medial collateral ligament was the primary stabilizer of the elbow to valgus stress. The relative contribution of the posterior ligament was minimal. After excision of the radial head alone, the slope of the load‐displacement curve decreased an average of 30%. Silicone rubber radial head replacement did not significantly improve the stability to valgus stress after radial head excision.
Site‐related variations in glycosaminoglycan content and swelling properties of bovine flexor tendon
Authors: Koob Thomas J. , Vogel Kathryn G.
Published: February 2005

The presence of morphologically distinct tissues within the adult bovine deep flexor tendon presented a model which we examined for correlations between proteoglycan content and tissue swelling properties. The proximal portion which experiences only tensile forces contained low levels of glycosaminoglycan (0.2% glycosaminoglycan hexosamine as percentage of dry weight) that were evenly distributed throughout its length and thickness. Collagen accounted for 80% of tissue mass, and collagen fibers formed parallel arrays running longitudinal to the direction of tensile force. In equilibrium bulk swelling tests, the properties of proximal tissue were uniform throughout the tissue and typical of collagenous tissues in which the response to equilibration in low ionic strength buffers or acid pH is dominated by the collagen network. The anterior aspect of the distal deep flexor tendon articulates with the stiff paratendinous sheath and sesamoid bones and is subjected to compressive and frictional forces in addition to longitudinal tensile forces. Along this anterior surface and extending partially into the tendon is tissue that resembles fibrocartilage with collagen fibers organized as a random network. Greatest glycosaminoglycan hexosamine contents (2–3% of dry weight) were found in the distal surface layer, and large proteoglycans were concentrated at the site receiving direct compressive and frictional loads. Equilibrium bulk swelling tests on distal tissue showed that the articulating surface layer possessed unique material properties. Distal surface layers swelled when counter ions were washed from the tissue, whereas lowered pH had little effect on distal tissue volume. Swelling properties of distal tissue correlated directly with proteoglycan content and were similar to swelling properties of articular cartilage. These results suggest that the articulating layer of distal flexor tendon is adapted for a unique set of mechanical requirements and that an elevated proteoglycan content at the site of compressive and frictional forces contributes to meeting these functional needs.
Mechanical behavior of the human lumbar spine. II. Fatigue strength during dynamic compressive loading
Authors: Hansson T. H. , Keller T. S. , Spengler D. M.
Published: February 2005

Seventeen cadaveric human lumbar motion segments from eight spines were cyclically loaded in vitro under axial compression. Loading frequency and magnitude were chosen to simulate rigorous activity within an in vivo physiological level. The load magnitude was determined as a percentage of the ultimate compressive load, the latter estimated from the bone mineral content (BMC) of lumbar vertebrae determined by dual‐photon absorptiometry. Following testing, the degree of macroscopic disc degeneration was assessed and the type of fracture in each specimen was determined from serial sagittal sections. Fractures were found in all but one specimen. Three types of fractures were formed: the node of Schmorl and Junghanns (type I), central endplate fracture (type II), and a crush or burst fracture (type III). The results suggested that type I fractures were predominantly associated with segments with normal disce, type II fractures were found primarily in segments with moderately degenerated discs, and type III fractures were associated with segments that failed on the first cycle. Segment stiffness and fatigue strength (cycles to failure) were correlated with disc degeneration, age, and segment BMC, the latter an in vivo measure of bone density. Fatigue strength also decreased in proportion to a power coefficient with increasing relative stress (cyclic stress range/ultimate stress).
Load displacement behavior of the human Lumbo‐sacral joint
Authors: McGlashen K. M. , Miller J. A. A. , Schultz A. B. , Andersson G. B. J.
Published: February 2005

The three‐dimensional load displacement behavior of nine fresh adult L5‐S1 spine motion segments was studied. Static test forces up to 160 N in anterior, posterior, and lateral shear, test forces up to 320 N in compression, and test moments up to 15.7 Nm in flexion, extension, lateral bending, and torsion were used. The six displacements of the center of the inferior L5 endplate were measured 15 and 60 s after the load was applied. Specimens were then retested after posterior element excision. The results show that at the maximum test force, intact specimen mean (sd) displacements ranged from 1.65 mm (0.63 mm) in lateral shear to 2.21 mm (0.87 mm) in posterior shear. Posterior element excision resulted in an average 1.66‐fold increase in shear translations. At the maximum moment, rotations ranged from 3.38° (1.03°) in torsion to 7.19° (1.77°) in flexion. Posterior element excision resulted in an average 2.09‐fold increase in bending rotations and a 2.74‐fold increase in the average torsional rotation. In general, these L5‐S1 joints were stiffer than more cranial lumbar segments in flexion, extension, and lateral bending and were less stiff in torsion tests.
Chondrons in cartilage: Ultrastructural analysis of the pericellular microenvironment in adult human articular cartilages
Authors: Poole C. Anthony , Flint Michael H. , Beaumont Brent W.
Published: February 2005

A combination of scanning and transmission electron microscopy was used to investigate the morphology and ultrastructure of normal human articular cartilage sampled from adult amputation specimens. This study confirms our previous observations on canine articular cartilage, which showed middle and deep layer chondrocytes surrounded by a pericellular matrix and enclosed within a pericellular capsule composed of filamentous and fine fibrillar materials. Pores in the “felt‐like” organization of the capsular weave progressively decreased in size from the inner to the outer border of the capsule. Matrix vesicles were found embedded within the capsular weave and distributed throughout the territorial matrix. It is suggested that the chondrocyte, its pericellular matrix, and capsule together constitute the “chondron,” a primary functional and metabolic unit of cartilage that acts hydrodynamically to protect the integrity of the chondrocyte and its pericellular microenvironment during compressive loading.
Protease inhibitors decrease rabbit cartilage degradation after meniscectomy
Authors: Caputo Claudia B. , Sygowski Linda A. , Patton Steven P. , Wolanin Donald J. , Shaw Andrew , Roberts Richard A. , Dipasquale Gene
Published: February 2005

In vitro proteoglycan (PG) synthesis and release were measured on cartilage removed from rabbit knees within 1 week of meniscectomy. Three days following partial lateral meniscectomy, 72% of the femurs and 82% of the tibias had visible ulcers. Cartilage from the weight‐bearing areas incorporated 2.0–2.9 times more 35S‐sulfate in vitro than cartilage from the opposite, unoperated knees. 3H‐thymidine incorporation was 2.5–3.4 times higher for surgical than control groups. 35S‐sulfate incorporation by the surgical group was inhibited by 22% in the presence of 10−4 M U24522, an inhibitor of rabbit chondrocyte metalloprotease (CMP). 3H‐thymidine incorporation by the surgical group was inhibited by 28% by 10−4 M U24522. In vitro PG release from cartilage removed 2 days after surgery was 1.6–3.7 times higher for the surgical than the control group. PG release by the surgical group after 22 h of incubation was reduced to the control level by three CMP inhibitors, U24278, U24279, and U24522. PG release by cartilage from the nonsurgical group was also reduced by these compounds at 22 h. These results suggest that both the anabolic and catabolic processes that are stimulated by surgery can be isolated in vitro and that CMP may be involved in the catabolic process.
Biochemistry of fusion mass consolidation in the sheep spine
Authors: Slater Robert , Nagel Donald , Smith R. Lane
Published: February 2005

We report here the biochemistry of fusion mass consolidation in sheep spines during a 1‐year period following autogenous cortical‐cancellous bone grafting and stabilization with Harrington distraction rods. Biochemical analysis of vertebral fusion mass included determination of wet weight and dry weight and quantification of glycosaminoglycan, collagen, calcium, and phosphate following extraction with neutral EDTA and proteolytic hydrolysis with papain. Our results showed that at 1 week after surgery, the fusion mass consisted of original cortical and cancellous bone graft material. The cortical bone graft was partially resistant to EDTA‐papain treatment, resulting in a residue containing hydroxyproline and mineral. At 12 weeks after surgery, the fusion mass had become a homogeneous material, which, like cancellous bone graft, was completely susceptible to treatment by EDTA‐papain. Collagen content of consolidating fusion mass was highest at 16 weeks after surgery when normalized to dry weight; glycosaminoglycan content was highest within 6 weeks after surgery. Mineral content was lowest at the 6‐week stage but by 12 weeks after surgery, it was comparable with original bone grafting material. At 24 and 52 weeks after surgery, fusion mass consolidation was characterized by an increase in the proportion of organic and mineral components resistant to EDTA‐papain. The appearance of the EDTA‐papain‐resistant material in the fusion mass coincided with formation of lamellar bone and successful consolidation.
Response of immature chicken meniscus to strenuous exercise: Biochemical studies of proteoglycan and collagen
Authors: Pedrini‐Mille Angiola , Pedrini Vittorio A. , Maynard Jerry A. , Vailas Arthur C.
Published: February 2005

Male white Leghorn chickens were exercised on a treadmill at 70–80% of their maximal oxygen consumption starting at 4 weeks and continuing up to 20 weeks of age. The effect of the strenuous exercise regime on the extracellular matrix of menisci was followed through studies of proteoglycans and collagen. Avian menisci contain type I collagen, chondroitin sulfate proteoglycans, which increase with age in amount and degree of aggregation, and dermatan sulfate proteoglycans, which decrease with age. Five weeks of exercise cause a premature decrease of dermatan sulfate proteoglycans, while the chondroitin sulfate–containing molecules become significantly more aggregrated than those of the tissue of age‐matched controls. Strenuous exercise also causes a significant decrease in the number of pyridinoline crosslinks per mole of collagen in the menisci of young runners. The exercise‐induced changes of proteoglycan and collagen occur only during the period of active growth, and all parameters return to normal when the animals reach skeletal maturity. The early proteoglycan aggregation and dermatan sulfate decrease induced by exercise are probably an adaption to the increased loading. Although the mechanism by which strenuous exercise reduces or delays the formation of collagen pyridinoline crosslinks in menisci of skeletally immature animals is unknown, their decrease could negatively affect the mechanical properties of the tissue during the period of active growth.
Intramuscular pressure in the supraspinatus muscle
Authors: Järvholm Ulf , Palmerud Gunnar , Styf Jorma , Herberts Peter , Kadefors Roland
Published: February 2005

Shoulder pain correlated to manual labour is an increasing problem. The etiology is multifactorial and often unclear. High local muscle load and muscle ischemia in the supraspinatus muscle is present in elevated arm positions, as shown in several electromyographic studies. The purpose of this study was to evaluate intramuscular pressure (IMP) as a way to describe local muscle load in the supraspinatus muscle. Measurements were made in 15 arm positions, and with hand loads of 0, 1, or 2 kg weight, in 12 shoulders. The IMP was recorded with microcapillary infusion technique. The method was found to be suitable in recording IMP at rest and during exercise. High intramuscular pressures, i.e., above 50 mm Hg (6.7kPa), were seen in moderate humeral abduction. The IMP increased further in abduction up to 90°, where mean IMP was 122 mm Hg (16.2 kPa). Added hand load increased intramuscular pressure in all positions except in shoulder flexion of 135°. The study thus demonstrated that intramuscular pressure offers important information about the load on the supraspinatus muscle in different positions of the arm. The results indicate that fatigue and shoulder pain related to elevated arm positions may be caused by muscle ischemia induced by the high intramuscular pressure present in these positions.
Pulsing electromagnetic field stimulation of the in vitro growth plate
Authors: Iannacone W. M. , Pienkowski D. , Pollack S. R. , Brighton C. T.
Published: February 2005

Specific pulsing electromagnetic fields (PEMFs) have been used to stimulate growth and repair of osteogenic tissues; however, the basis for this specificity is unknown. Previously, we determined the relevant electromagnetic field parameters of the clinically used PEMF and independently verified the beneficial effects of PEMFs on the rabbit fibula fracture healing model. The goal of the present study was to develop an in vitro model that would permit the effectiveness of various electric and magnetic field components of the PEMF to be determined.

The costochondral junction (CCJ) of the 21‐day‐old rat was exposed in vitro to PEMFs with various electric and magnetic field component amplitudes. Response of this model to PEMFs was determined by nondestructive macrophotographic measurement of CCJ growth. Preliminary data indicated that temperature effects were present in this in vitro system. Subsequent experiments designed to separate the effects of temperature and PEMFs on the growth of CCJs in tissue culture were performed.

Results indicate that accurate and frequent temperature measurements must be made for in vitro models being used to study effects of PEMFs. Small temperature differences induced by the coils used to produce PEMFs in the CCJ experimental system can have significant stimulatory effects, and the combined effects of temperature and PEMFs are not linearly additive in this model. Furthermore, our results suggest that thermal and PEMF stimuli could affect macrophotographically measured growth of the CCJ by separate mechanisms or could have a synergistic effect. Therefore, PEMF stimulation experiments should be performed under strictly “athermal” conditions.
Bone ingrowth into porous calcium phosphate ceramics: Influence of pulsing electromagnetic field
Authors: Shimizu Tomio , Zerwekh Joseph E. , Videman Tapio , Gill Kevin , Mooney Vert , Holmes Ralph E. , Hagler Herbert K.
Published: February 2005

The effect of a pulsing electromagnetic field (PEMF) on bone ingrowth into porous hydroxypatite (HA) and porous tricalcium phosphate (TCP) implanted in rabbit tibiae was studied. To quantitate the biological response, a recently developed method of surface measurement using a scanning electron microscope was used. The morphometrical findings in the HA pores demonstrated a significantly greater amount of bone and thicker bone trabeculae in the PEMF group as compared with the nonpulsed control group at 3 to 4 weeks postimplantation. No significant differences for these parameters were found in the TCP pores. Histologically, more bone and wider bone trabeculae were observed in the HA implants for the PEMF‐treated animals at the early time periods when compared with those of the control animals. Alternatively, the histological findings of the TCP implants were similar between these two groups. These histological results tended to correlate with the morphometrical data. Together, these results suggest that accelerated bone formation and bone maturation occurred in response to PEMF in the HA pores but was without effect in the TCP pores. This stimulatory effect is most significant after 3–4 weeks of PEMF stimulation.
Time‐varying magnetic fields: Effects of orientation on chondrocyte proliferation
Authors: Elliott J. P. , Smith R. L. , Block C. A.
Published: February 2005

The purpose of this study was to determine the effect of orientation of pulsed electromagnetic fields (PEMFs) on cellular proliferation and extracellular matrix synthesis. Bovine articular chondrocytes were cultured in PEMFs (repetitive pulse at 72 Hz) generated using Helmholtz coils oriented either parallel (horizontal) or perpendicular (vertical) to the plane of cell adhesion. Dissipation of signal energy in the form of heat increased the temperature of the PEMF coils by 2°C and the tissue culture medium by 1°C. Therefore, control coils, which emitted no PEMFs, were heated to the temperature of PEMF coils by circulating water. Chondrocytes were cultured in 16‐mm‐well culture plates, and the data for individual wells were pooled as triplicates. Although not observed by microscopic examination of individual wells, positionally dependent electric field effects may be minimized by this approach. PEMFs generated by coils oriented vertically significantly decreased chondrocyte proliferation. The effect was dependent on the concentration of serum in the culture media. At 3% serum concentration, the total cell number attained after 10 days of culture was reduced by 50% in stimulated cultures when compared with controls. At 5% serum concentration, there was no effect. PEMFs applied by coils oriented horizontally did not alter proliferation of articular chondrocytes. PEMFs had no effect on synthesis of extracellular matrix by chondrocytes plated at high density, irrespective of orientation.
Limb lengthening by low rate epiphyseal distraction. An experimental study in the caprine tibia
Authors: Fjeld Terje O. , Steen Harald
Published: February 2005

Low‐rate epiphyseal distraction of the left proximal tibia using a modified bilateral Hoffmann external fixation device, was accomplished in 14 goats (age 6–7 months). Daily distraction at a rate of 0.5 mm was continued for 5.5 weeks. Epiphysiolysis occurred after 5–9 days. After distraction had been discontinued, the external device was left in situ for fixation for 4 weeks. The animals in group 1 (n = 5), group 2 (n = 3), and group 3 (n = 5) were killed at 4, 16, and 32 weeks, respectively, from the end of the distraction period. The proximal growth plate of the elongated tibia appeared radiolucent at the conclusion of the study but was less distinct and reduced in height as compared with the control leg. The gained length at the end of the distraction period was on the average 2.2 cm (11.9%). This gain in length was reduced with further growth. In group 3, the final gain in length was reduced to half. A reduced cortical thickness of the bone within the area subjected to distractional force was observed. This finding is attributable to stress protection. An interesting observation comparing control and operated tibia was an increase of the cross‐sectional diameter of the elongated bone. Both tibiae of all animals were tested mechanically. The torsional strength of the elongated tibiae as compared with controls was on the average 29% in group 1, 79% in group 2, and 95% in group 3. We conclude that leg lengthening by low‐rate epiphyseal distraction in the proximal tibia is a justifiable alternative to other lengthening procedures in individuals approaching adolescence. In juveniles, lengthening by epiphyseal distraction may result in reduction in the longitudinal growth.
Keratan sulfate is a component of proteoglycans in the compressed region of adult bovine flexor tendon
Authors: Vogel Kathryn G. , Thonar Eugene J‐M. A.
Published: February 2005

A monoclonal antibody (ET‐4‐A‐4) was used to identify keratan sulfate (KS) as a constituent of bovine flexor tendon. KS was present in at least 500‐fold higher amounts in the fibrocartilaginous region of the tendon that is subjected to compressive forces in vivo (mean = 0.03% of tissue dry weight) than in the more proximal regions subjected only to tensional forces. The KS was associated with proteoglycans of three size categories that could be separated by Sepharose CL‐4B chromatography. The largest proteoglycan (Vo) contained ∼4% KS and was predominant in the surface region of the tendon subjected directly to compressive forces. A population of somewhat smaller molecules (Kav ≅0.3) contained ≤20% KS and proportionately less chondroitin sulfate (CS) or dermatan sulfate (DS). The KS chains of this population were not digested by keratanase. This population was dominant in tissue from the middle layer of the fibrocartilaginous region. A third population of small KS proteoglycans or fragments (Kav ≅ 0.6) comprised 40% of the KS found in the deepest layer of the compressed tendon region. This smaller component was independent of the small DS proteoglycans.
Evaluation of fluorescein diacetate for flow cytometric determination of cell viability in orthopaedic research
Authors: Bell R. S. , Bourret L. A. , Bell D. F. , Gebhardt M. C. , Rosenberg A. , Berrey H. B. , Treadwell B. V. , Tomford W. W. , Mankin H. J.
Published: February 2005

Accurate estimation of cellular viability is important both in research and in aspects of orthopaedic clinical practice. We have been interested in the potential for flow cytometric application of fluorescein diacetate (FDA) in evaluating chondrocyte survival following cryopreservation of osteochondral allografts as well as in the assessment of sarcoma necrosis following preoperative chemotherapy. In order to evaluate the suitability of this method for cell viability assays, this study compared FDA with more traditional methodology (trypan blue, clonigenic assay, metabolic activity analysis, measurement of DNA synthesis, and histological assessment of necrosis). Both chondrocytes and sarcoma cells were exposed to various experimental injuries prior to viability analysis. Although it is evident from these experiments that FDA accurately reflects cell survival after physical injury, it underestimates the effect of chemotherapy on cell reproductive potential in vitro. However, FDA is highly correlated with histological assessment of tumor viability after chemotherapy in vivo. It is apparent that the methodology chosen for determination of viability should be appropriate for the type of experimental injury and should analyze the cell function (i.e., metabolic activity or reproductive capacity) that is appropriate for the experimental model.
Pressure distribution in the wrist joint
Authors: Tencer A. F. , Viegas S. F. , Cantrell J. , Chang M. , Clegg P. , Hicks C. , O'Meara C. , Williamson J. B.
Published: February 2005

We performed a study to determine pressure distribution properties of the normal radio‐carpal joint. A system was developed for measurement of the contact pressure within the wrist joint surfaces. The transducer was based on Fuji pressure‐sensitive paper, which was inserted into the joint space through a dorsal capsular incision. The hand was then positioned using a jig that permitted free axial loading of the joint. Each of five specimens was tested in 36 positions combining flexion/extension with radio/ulnar deviation and supination/pronation. The transducers were analyzed for contact area, scapholunate contact area ratio, pressure, and centroid locations using a microcomputer‐based video‐imaging system. The scaphoid and lunate contact areas on the radius and traingular fibrocartilage were separate and distinct in all wrist positions. Together these contact areas accounted for a relatively small fraction of the total joint surface area (average contact area/total joint area = 0.206, SD = 0.0495). For an applied 103 Newton compressive load, the high pressure averaged 3.17 MPa (SD = 0.83 MPa). Overall, the scaphoid contact area was 1.47 times that of the lunate, although variations occurred with position, as in flexion, in which the scaphoid/lunate area ratio was 0.83. The highpressure centroids of both scaphoid and lunate contact areas shifted palmarly from 20° of flexion to 20° of extension and then dorsally with further extension. The scaphoid‐lunate intercentroid distance averaged 14.91 mm with a range of 10–20 mm.
Strength reduction and the effects of treatment of long bones with diaphyseal defects involving 50% of the cortex
Authors: Leggon Robert E. , Lindsey Ronald W. , Panjabi Manohar M.
Published: February 2005

Currently, three criteria are accepted as indications for prophylactic internal fixation of metastatic disease in long bone, including lesions (a) destroying 50% or more of the cortex; (b) 2.5 cm or greater in diameter; or (c) with pain unrelieved by radiation therapy. Using an oblong defect configuration in which one half of the cross‐sectional area was destroyed, canine femora were torsion‐tested at high speed to determine (a) the actual strength reduction incurred by a lesion destroying 50% of the cortical circumference, and (b) the effects and benefits of internal fixation using polymethylmethacrylate and/or a six‐hole compression plate on such a defect. The femurs with a 50% circumferential cortical defect demonstrated only 12.7 ± 3.8% of intact strength. Defects treated with a combination of plating (all screws bicortical) and polymethylmethacrylate (torque to failure 4.39 ± 0.90 times greater than the defect alone or TE/TD = 4.39 ± 0.90) were statistically stronger than defects treated with polymethylmethacrylate alone (TE/TD = 2.48 ± 0.66; p < 0.025) or by plating alone (TE/TD = 2.61 ± 0.91; p < 0.025), but torque‐to‐failure was only increased to approximately 56% of an intact bone. Plated intact bones (TE/TD = 5.33 ± 0.41) were significantly weaker than intact bones (TE/TD = 8.50 ± 2.52; p < 0.001). Our results substantiate the need for using polymethylmethacrylate and internal fixation in combination when prophylactically fixing pathologic lesions of this proportion.
Juxtaarticular bone loss in experimental inflammatory arthritis
Authors: Bogoch Earl , Gschwend Norbert , Bogoch Barbara , Rahn Berton , Perren Stephan
Published: February 2005

The osteopenia associated with experimental inflammatory arthritis was studied by a histomorphometric method that exphasized net changes in bone composition. Juxtaarticular trabecular bone volume and turnover were studied in the carrageenan injection model of inflammatory arthritis of the mature rabbit knee. Trabecular bone volume was studied by histomorphometry of the femoral condyles and confirmed by photodensitometry on standard macroradiographs. Osteogenesis was studied by imaging of calcein fluorochrome‐labeled newly formed bone in undecalcified histological sections. A significant net loss of cancellous bone (∼20%) occurred over 49 days in both the medial and the lateral femoral condyle in the arthritis group compared with normal controls. Total osteogenesis was increased fourfold and it was calculated that an even greater increase in total bone resorption was responsible for the negative bone balance. There is evidence that the periarticular bone loss of human rheumatoid arthritis is also associated with increased bone turnover. Quantitative studies of the kinetics of bone remodeling in inflammatory arthritis will provide the basis for therapeutic attempts to prevent or reverse arthritis‐induced bone loss. Fracture risk in inflammatory arthritis may be increased not only by osteopenia, but additionally by the presence of a large proportion of newly formed (and presumably less mineralized) bone.
Metabolic and biochemical abnormalities of articular cartilage induced by implantation of a sterile sheet of polyethylene in the rabbit patellofemoral joint
Authors: Front Philippe , Garcia Fernando , Guillermet Veronique , Darmon Nicole , Garcia Gladys , Mitrovic Dragoslav R.
Published: February 2005

A polyethylene sheet was implanted in the patellofemoral joint of the right knee of the rabbit and the biochemical and metabolic changes in the articular cartilage from femoral trochleas (in contact with the implant) and femoral condyles (free of direct contact) were compared with those in their sham‐operated counterparts 7, 15, and 30 days after joint implantation. The results showed that there was an increase in the water content; the extraction yields of uronic acid‐, 35SO4−, and [3H]glycine‐containing compounds; and the incorporation of [3H]thymidine, [3H]glycine, and 35SO4. Concomitantly, the contents of uronic acid‐, hexosamine‐, neutral sugars‐, and hydroxyproline‐containing substances decreased in the femoral trochlear cartilage and, to a musch lesser extent, in the femoral condylar cartilage from implanted joints. The increased capacity of viable chondrocytes to incorporate metabolic radiolabeled precursors into newly synthesized macromolecules may represent a reparative cell response to the tissue injury induced by the implant. This is therefore a useful model for studying the response of chondrocytes to mechanical injury and tissue tolerance to intraarticularly implanted prosthetic materials.