bluuebunny/crossref_metadata_2025 huggingface dataset:
Reimplantation of growth plate chondrocytes into growth plate defects in sheep
Authors: Foster B. K. , Hansen A. L. , Gibson G. J. , Hopwood J. J. , Binns G. F. , Wiebkin O. W.
Published: February 2005

Defects in growth plates due to trauma, infection, or genetic causes can result in bone formation across the defect, bridging the epiphysis and metaphysis, resulting in growth arrest and limb deformation. We have investigated the capacity of implanted chondrocyte cultures to prevent this process. Sheep growth plate chondrocytes were isolated, and after culture at high density produced easily manipulated cartilaginous disc. The tissue was implanted into growth plate defects produced in lambs and the response was assessed histologically. Following implantation, cultures continued to proliferate and maintain a cartilage‐like matrix. 8 to 12 weeks, hypertrophic maturation, chondrocyte columnation, and associated endochondral calcification were observed. Culture implantation was always associated with local immune inflammatory feaction, which continued throughout the course of investigation. Cellular survival was variable and resulted in the presence of viable implants as well as residual cartilage matrix devoid of chondrocytes; however, implanted chondrocyte discs always prevented bone bridge formation. These findings encourage the expectation that cultured chondrocytes may provide a useful replacement for the inert interpositional materials currently used in the treatment used in the treatment of growth arrest. The potential of this technique for growth plate replacement, however, requires a more predictable rate of implant survival. The likely reasons for implant loss are discussed.
Fatigue fractures in thoroughbred racehorses: Relationships with age, peak bone strain, and training
Authors: Nunamaker D. M. , Butterweck D. M. , Provost M. T.
Published: February 2005

The North American Thoroughbred racehorse was chosen as a model to study the pathogenesis of fatigue failure of bone. This species has a high incidence of spontaneous fatigue failure of bone (bucked shins) during its early training. In vivo strain gauge studies of the third metacarpal bone o four young racehorses running at racing speeds showed high principal compressive strains [−4,841 ± 572 (SD) microstrain] while two older horses had lower principal compressive strains (−3,317 microstrain measured at racing speed, −3,250 microstrain extrapolated from a slower speed run). Previously reported intertial property measurements of the third metacarpal bone were related to the diffeence in bone strains seen in young and older horses. The high strains on the surface of the third metacarpal bone associated with young horses in training may lead to high strain, low cycle fatigue. The changing shape of the third metacarpal bone during maturation may be consistent with the lower strains recorded during high speed exercise in theo lder animals. This phenomenon may allow for the accumulation of additional strain cycles in older animals beore failure occurs.
Combined treatment with cyclosporin A and cortisone acetate minimizes the adverse bone effects of either agent alone
Authors: Movsowitz C. , Schlosberg M. , Epstein S. , Ismail F. , Fallon M. , Thomas S.
Published: February 2005

Although cyclosporin A (CsA) and cortisone acetate (CRT) adversely affect bone, their combined effect on bone is unknown. Sprague Dawley rats were therefore administered either vehicle or CsA (7.5 mg/kg/day) by gavage and saline or CRT (2 mg/100 mg/day) by s.c. injection for 28 days. Group A received vehicle plus saline, group B CsA plus saline, group C vehicle plus CRT, and group D CsA/CRT. Serial bloods were sampled over a 28‐day period for ionized calcium (Ca), PTH, 1,25 dihydroxyvitamin D (1,25(OH)2D), and bone gla protein (BGP osteocalcin) and tibia were examined on day 28 for histomorphometry. Results were compared with group A. Ca and PTH levels in groups B, C, and D were similar to those in group A during the study period. Group B had lower body weights, elevated levels of BGP, and an increase in 1,25(OH)2D. Group C developed weight loss and a decrease in BGP and 1,25(OH)2D. Group D had weight loss, BGP levels between those of group A and group C, and 1,25(OH)2D values similar to group A. Bone histomorphometry revealed high turnover osteopenia in group B and hyperostosis in group C with a decrease in bone formation and osteoclastlike cells. Combination therapy returned these to control values. In conclusion, the adverse effects of either CsA or CRT on bone in rats are minimized by combined therapy.
An approach for time‐dependent bone modeling and remodeling—theoretical development
Authors: Beaupré G. S. , Orr T. E. , Carter D. R.
Published: February 2005

A time‐dependent approach for emulating bone modeling and remodeling in response to the daily loading history is presented. We postulate that genotype, systemic metabolic conditions, and local tissue interactions establish the level of local tissue mechanical stimulation (attractor state) appropriate for the maintenance of bone tissue. The net daily rate of apposition or resorption on a bone surface is determined by the difference between the actual stimulus and the tissue attractor state and can be modulated by other biologic factors. In calculating the net change in local bone apparent density, the technique takes into account the bone surface area available for osteoblastic and osteoclastic activity. Endosteal, periosteal, haversian, and cancellous bone modeling and remodeling are thereby treated in a consistent, unified fashion.
Electromagnetic effects on bone formation at implants in the medullary canal in rabbits
Authors: Spadaro J. A. , Albanese S. A. , Chase S. E.
Published: February 2005

This experiment was aimed at illuminating the relationship between electromagnetic and mechanical stimuli of bone formation when present simultaneously. Movable and stationary intramedullary wire implants were studied in rabbits treated with a pulsing electromagnetic field (PEMF) 4 h/day for 3 weeks, and were compared with identical control animals without PEMF. Trabecular bone formed routinely at spontaneously movable implants, but not at stationary ones. On average, PEMF‐treated movable implants in the femur induced 44% more bone than untreated movable implants. Also, in the PEMF‐treated femora, a 22% enlargement of the area of the medullary canal was observed compared with no‐field controls. In the tibia, these effects were weak or nonexistent. The PEMF used did not induce bone at stationary implants, suggesting that under these conditions it is not a primary trigger in vivo.
Osteoarthrosis induced by intra‐articular hydrogen peroxide injection and running load
Authors: Kaiki Genkyo , Tsuji Haruo , Yonezawa Takanobu , Sekido Hiromichi , Takano Takashi , Yamashita Shinichiro , Hirano Norikazu , Sano Akimi
Published: February 2005

Osteoarthrosis of the rat knee joint was induced successfully by intra‐articular injection of 2% hydrogen peroxide (H2O2) and running load. In the group receiving two injections of physiological saline with running load, no histological osteoarthrotic knees were developed up to 8 weeks after the injection. In the group receiving two 2% H2O2 injections and running load, advanced osteoarthrosis occurred in all knees 8 weeks after the first injection, and the Mankin's score of osteoarthrotic knees appeared to be higher than the group receiving two 2% H2O2 injections without running load (p < 0.004, Kruskal‐Wallis H test). In the rats receiving a single 2% H2O2 injection with running load and a vitamin E‐enriched diet, the inhibitory effect of vitamin E on the development of osteoarthrosis was statistically significant compared to the regular diet group (p < 0.05, Wilcoxon rank test).
Visualization of living terminal hypertrophic chondrocytes of growth plate cartilage in situ by differential interference contrast microscopy and time‐lapse cinematography
Authors: Farnum Cornelia E. , Turgai John , Wilsman Norman J.
Published: February 2005

The functional unit within the growth plate consists of a column of chondrocytes that passes through a sequence of phases including proliferation, hypertrophy, and death. It is important to our understanding of the biology of the growth plate to determine if distal hypertrophic cells are viable, highly differentiated cells with the potential of actively controlling terminal events of endochondral ossification prior to their death at the chondro‐osseous junction. This study for the first time reports on the visualization of living hypertrophic chondrocytes in situ, including the terminal hypertrophic chondrocyte. Chondrocytes in growth plate explants are visualized using rectified differential interference contrast microscopy. We record and measure, using time‐lapse cinematography, the rate of movement of subcellular organelles at the limit of resolution of this light microscopy system. Control experiments to assess viability of hypertrophic chondrocytes include coincubating organ cultures with the intravital dye fluorescein diacetate to assess the integrity of the plasma membrane and cytoplasmic esterases. In this system, all hypertrophic chondrocytes, including the very terminal chondrocyte, exist as rounded, fully hydrated cells. By the criteria of intravital dye staining and organelle movement, distal hypertrophic chondrocytes are identical to chondrocytes in the proliferative and early hypertrophic cell zones.
A model of Staphylococcus aureus bacteremia, septic arthritis, and osteomyelitis in chickens
Authors: Daum Robert S. , Davis W. Hodges , Farris K. Barton , Campeau Richard J. , Mulvihill Denise M. , Shane Simon M.
Published: February 2005

We studied the occurrence, magnitude, and kinetics of bacteremia and the resultant osteomyelitis and septic arthritis in an avian model of Staphylococcus aureus infection. Thirty‐day‐old male broiler chicks were inoculated i.v. with 105, 106, or 107 cfu of strain Duntravis, a β‐hemolytic, coagulaseproducing, capsular type 8 isolate from the synovial fluid of a 2‐year‐old black boy. Bacteremia occured in 80%, 90%, and 100% of animals inoculated with 105, 106, or 107 cfu, respectively. The magnitude of bacteremia in surviving, bacteremic animals increased for 96 hours after inoculation and then decreased after a plateau phase. Osteomyelitis and septic arthritis occurred only in chicks that were continuously bacteremic. The occurrence of osteomyelitis was uniform among continuously bacteremic animals and developed 1 to 23 hours after inoculation. Chickens are susceptible to systemic infections with S. aureus. Bacteremia, osteomyelitis, and septic arthritis may be induced in healthy chickens without prior manipulations that depress their resistance.
Evaluation of a microcomputed tomography system to study trabecular bone structure
Authors: Kuhn J. L. , Goldstein S. A. , Feldkamp L. A. , Goulet R. W. , Jesion G.
Published: February 2005

A new microcomputed tomography (micro‐CT) system and thresholding procedure was evaluated as a tool for nondestructive analysis of trabecular bone. Images of 6‐mm trabecular bone cubes acquired from the micro‐CT system were compared with optical images of corresponding histologic sections to determine the accuracy of representation. The stereologic measures of bone volume fraction (Pp) and trabecular plate densty (PL) were used to quantify the comparisons. The results showed that the micro‐CT measures of Pp were not significantly different from those measured from histologic sections and therefore were very accurate. Measures of PL were different by approximately 14%, which translated into discrepancies in trabecular plate thicknesses of about 19 μm. This difference was significantly correlated to the microstructural characteristics of the specific specimen scanned. The precision of both measurements was excellent.
Effects of retinacular release and tibial tubercle elevation in patellofemoral degenerative joint disease
Authors: Lewallen David G. , Riegger Chery L. , Myers Elizabeth R. , Hayes Wilson C.
Published: February 2005

Release of the patellar retinaculum and tibial tubercle elevation have both been advocated for the treatment of patellofemoral degeneration. Questions remain, however, regarding the magnitude and predictability of such effects in diseased joints. Using cadaver knee joints exhibiting a range of patellofemoral cartilage degeneration, we investigated the effects on joint contact pressures on release of the patellar retinaculum, followed by tibial tubercle elevations of 1.25 and 2.5 cm. Retinacular release failed to alter the joint‐loading parameters significantly. Tibial tubercle elevation reduced the patello‐femoral joint contact area and contact force, but failed to cause a consistent change in contact pressure. Tibial tubercle elevation also caused a migration of the joint contact area superolaterally on the retropatellar surface. This migration occurred in conjunction with ventral tilting of the inferior pole of the patella as the tubercle was elevated, suggesting that significant changes in joint kinematics may result from this procedure.
The effect of porous coating processing on the corrosion behavior of cast Co–Cr–Mo surgical implant alloys
Authors: Jacobs J. J. , Latanision R. M. , Rose R. M. , Veeck S. J.
Published: February 2005

The manufacture of porous coated cobalt‐based surgical implant alloys requires sintering–a high temperature process above the incipient melting temperature of this alloy system. The metallurgical changes produced by the high temperature sinter cycle consist of dissolution of interdendritic carbides, massive precipitation of lamellar carbide eutectic phases at grain boundaries, localized porosity from incipient melting that is not completely eliminated by subsequent hot isostatic pressing, and grain growth in fine‐grained meterials. These microstructural changes, which are known to affect the mechanical properties, do not affect the static in vitro localized and generalized corrosion behavior of the bulk material as determined by anodic polarization measurements in a buffered saline environment and direct examination by scanning electron and optical microscopy. Additionally, cast Co‐Cr‐Mo surgical implant alloys are found to be immune to crevice corrosion (in the absence of mechanical fretting) in the saline environment studied. The hystertic component of the anodic polarization curve is not due to crevice corrosion; rather, as suggested by the electrochemical tests and Auger spectroscopy, the hysteresis is due to redox reactions in the chromium‐rich surface layer.
The effects of hydrostatic pressure on matrix synthesis in articular cartilage
Authors: Hall A. C. , Urban J. P. G. , Gehl K. A.
Published: February 2005

The direct effects of hydrostatic pressure on matrix synthesis in articular cartilage can be studied independently of the other factors that change during loading. We have found that the influence of hydrostatic pressure on incorporation rates of 35SO4 and [3H]proline into adult bovine articular cartilage slices in vitro depends on the pressure level and on the time at pressure. Pressures in the “physiological” range (5–15 MPa) applied for 20s or for 5 min could stimulate tracer incorporation (30–130%) during the following 2 h, but higher pressures (20–50 MPa) had no effect on incorporation rates. The degree of stimulation in cartilage obtained from different animals was found to vary; in some animals none was seen. Stimulation also varied with position along the joint. Physiological pressures (5–10 MPa) applied continuously for the 2‐h incubation period also stimulated incorporation rates, but pressures >20 MPa always produced a decrease that was related to the applied pressure and that was reversible. These results suggests that the hydrostatic pressure that occurs during loading is a signal that can stimulate matrix synthesis rates in articular cartilage.
Demineralized allogeneic bone matrix for cartilage repair
Authors: Dahlberg Leif , Kreicbergs Andris
Published: February 2005

We tested the chondrogenic potential of demineralized allogeneic bone matrix (DABM) in the repair of osteochondral defects. In 42 adult rabbits, a 5‐mm2 or 15‐mm2 defect was created bilaterally in the intercondylar groove of distal femur. DABM was inserted directly in 37 defects, whereas in 35 it was inserted after previous placement in muscle for 4, 16, or 19 days. Another 12 defects were left empty, serving as controls. Subgroups of animals were killed at 6, 12, 18, and 26 weeks. The distal femora were excised and prepared for histologic evaluation in hematoxylin‐eosin and toluidine blue. Cartilage‐like repair tissue was observed in the majority of defects. However, there was a great variability in the experimental groups without any clear relationship to type of DABM implant, defect size, or postoperative time. Even individual knees exhibited varying stages of cartilage differentiation. Overall, DABM placed in muscle for 19 days appeared to yield the best repair of the defects. The most consistent findings of the present study were bone formation in the marrow of distal femur and, notably, the absence of bone differentiation toward the joint surface. Hence, it seems that the synovial environment prevents bone formation otherwise induced by DABM in vascular tissue. Although tissue formed in articular defects supplemented with DABM is of cartilaginous differentiation, which is retained over time, it is of highly variable quality. Hence, the described approach has to be optimized before it can be applied for the purpose suggested.
Histochemical and ultrastructural observations on brown degeneration of human intervertebral disc
Authors: Ishii Tsutomu , Tsuji Haruo , Sano Akimi , Katoh Yoshiharu , Matsui Hisao , Terahata Nobuo
Published: February 2005

Thirty‐eight fresh human intervertebral discs collected during anterior interbody fusion surgery were histochemically and ultrastructurally analyzed for pigments. Macroscopically, five stages of degeneration were classified according to the color, fibrosis, and fragility of the nucleus pulposus of the discs. In order to demonstrate lipofuscin granules, specimens were subjected to special staining procedures, including carbol fuchsin lipofuscin stain, the Schmorl's reaction, and autofluorescence. Lipofuscin granules were distributed from the inner layer of the annulus fibrosus to the nucleus pulposus. Such granules were numerous in cases of slight or severe degeneration, whereas fewer granules were found in cases of moderate degeneration. However, the stage of macroscopic degeneration of the intervertebral disc did not necessarily correlate with the incidence of lipofuscin granules. By ultrastructural observation, the morphological features of the components of the intervertebral disc and the ultrastructure of the lipofuscin granule were clarified. The ultrastructure of the “brown degeneration” disc exhibited markedly increased amorphous electron‐dense bodies located among collagen fibrils in the matrix.
[99mTc]diphosphonate uptake and hemodynamics in arthritis of the immature dog knee
Authors: Hansen Ebbe Stender , Søballe Kjeld , Henriksen Tine Brink , Hjortdal Vibeke Elisabeth , Bünger Cody
Published: February 2005

The relationship between [99mTc]diphosphonate uptake and bone hemodynamics was studied in canine carrageenan‐induced juvenile chronic arthritis. Blood flow was determined with microspheres, plasma and red cell volumes were measured by labeled fibrinogen and red cells, and the microvascular volume and mean transit time of blood were calculated. Normal femoral epiphyses had lower central and higher subchondral blood flow and diphosphonate uptake values. Epiphyseal vascular volume was uniform, resulting in a greater transit time of blood centrally. In arthritis, blood flow and diphosphonate uptake were increased subchondrally and unaffected centrally, while epiphyseal vascular volume was increased throughout, leading to prolonged transit time centrally. The normal metaphyses had low blood flow and diphosphonate uptake values in cancellous bone and very high values in growth plates, but a large vascular volume throughout. The mean transit time therefore was low in growth plates and high in adjacent cancellous bone. Arthritis caused decreased blood flow and diphosphonate uptake in growth plates but increased vascular volume and transit time of blood. Diphosphonate uptake correlated positively with blood flow and plasma volume and negatively with red cell volume in a nonlinear fashion. Thus, changes in diphosphonate uptake and microvascular hemodynamics occur in both epiphyseal and metaphyseal bone in chronic synovitis of the immature knee. The [99mTc]diphosphonate bone scan seems to reflect blood flow, plasma volume, and red cell volume of bone.
Necrosis of the capital femoral epiphysis and medial approaches to the hip in piglets
Authors: Fisher Edward H. , Beck Pul A. , Hoffer M. Mark
Published: February 2005

In an attempt to produce necrosis of the femoral head, the medial femoral circumflex vessels were disrupted in 13 normal piglet hips through a medial approach. Femoral heads were recovered 3–6 months (average 4.2 months) postoperatively. None of these hips showed gross, radiographic, or microscopic evidence of necrosis. This demonstrates that necrosis, which may occur after the medial approach in the hip of a child, is not due to the direct damage to the medial femoral circumflex vessels.
Anterior and posterior internal fixation of vertical shear fractures of the pelvis
Authors: Stocks Gregory W. , Gabel Gerard T. , Noble Philip C. , Hanson Gregory W. , Tullos Hugh S.
Published: February 2005

A laboratory study was undertaken to evaluate the effectiveness of alternative methods of fixation of unilateral vertical shear fractures of the pelvis. Prior to experimental testing, a biomechanical analysis was performed to estimate the forces that displace the hemipelvis in the presence of two different patterns of injury: an interforaminal sacral fracture and a disruption of the sacroiliac joint. These lesions were then experimentally created in five unembalmed human pelvises and sequentially fixed with an external Hoffmann frame alone, a Hoffmann frame with sacral bars, or sacral bars with either one or two bone plates placed across the symphysis pubis. Each pelvis/fixator system was mechanically tested by loading along the direction of the resultant muscle force predicted by the biomechanical analysis. During loading the proximal migration of the ilium was continuously recored with a transducer. At intervals during loading, the three‐dimensional displacement of the detached hemipelvis at the pubic symphysis was also measured using a stereophotographic technique. With both the sacral frature and the sacroiliac disruption, the addition of posterior sacral rods substantially increased the strength and rigidity of fixation provided by the Hoffmann fixation frame alone (p < 0.01). In speciments with a sacral fracture, the use of anterior plates with posterior rods restored 65–71% of the strength of the intact pelvis, in comparison with 46% observed with the combination of sacral rods with an anterior Hoffmann frame (p < 0.01). All of the methods of fixation evaluated in this study were less successful in stabilizing the sacroiliac distruption. In this case there was no significant difference between the fixation achieved with one or two anterior bone plates or a Hoffmann frame placed anteriorly in combination with sacral rods placed posteriorly. In both patterns of injury treated with posterior sacral rods, the use of two anterior base plates led to no significant enhancement of the strength or the rigidity of fixation compared with one anterior plate alone.
Purified staphylococcal culture medium stimulates neutral metalloprotease secretion from human articular cartilage
Authors: Williams Riley J. , Smith R. Lane , Schurman David J.
Published: February 2005

Human articular cartilage released significantly increased levels of metal‐dependent enzymes capable of degrading collagen, casein, and gelatin at a neutral pH following exposure to a sterile, purified fraction of Staphylococcus aureus culture medium. Neutral metalloprotease activity was determined by radiolabeled substrate assays and substrate gel analysis. The enzymes were activated with 4‐aminophenylmercuric acetate and were inhibited by 1, 10‐phenanthroline and ethylenediamine tetraacetic acid. Protein immunoblots demonstrated that type I collagenase and stromelysin (matrix metalloproteinase III) secretion was increased following staphylococcal medium challenge. The profile of enzymatic activity induced by staphylococcal medium was directly comparable to that observed with interleukin‐1, which was used as a positive control. The staphylococcal medium had no inherent proteolytic activity. Increased production of the neutral metalloproteases collagenase and stromelysin may significantly contribute to the extensive cartilage destruction noted in staphylococcal septic arthritis.
Effect of Staphylococcus epidermidis on adherence of Pseudomonas aeruginosa and Proteus mirabilis to polymethyl methacrylate (PMMA) and gentamicin‐containing PMMA
Authors: Chang Chung Che , Merritt Katharine
Published: February 2005

The goals of this study were to determine (1) effect of Staphylococcus epidermidis adherence and biofilm production on adherence of the opportunistic pathogens Proteus mirabilis and Pseudomonas aeruginosa to polymethyl methacrylate (PMMA); (2) if the biofilm killed by autoclaving altered adherence of other organisms; (3) if adherence of S. epidermidis to gentamicin‐containing PMMA altered adherence of the opportunistic pathogens P. mirabilis and P. aeruginosa to gentamicin‐containing PMMA. Results show that biofilms formed by S. epidermidis, whether alive or dead, significantly increased adherence of Pseudomonas. Adherence of Proteus was significantly increased on dead biofilms and increased, but not significantly (p = < 0.1), on live ones. Greatest adherence seen in the study was to autoclaved biofilms. Significant adherence of Proteus and Pseudomonas was found on gentamicin‐containing PMMA specimens, which were preincubated with S. epidermidis for formation of the biofilm. These results indicate that a biofilm is formed on PMMA‐gentamicin specimens and this may impair the ability of gentamicin to kill other organisms.
Ischemic necrosis of cartilage in spontaneous and experimental lesions of osteochondrosis
Authors: Carlson C. S. , Meuten D. J. , Richardson D. C.
Published: February 2005

This study was designed to examine the association of spontaneous lesions of osteochondrosis with vascular supply to epiphyseal cartilage, and to determine whether similar lesions could be experimentally reproduced by selective interruption of cartilage canal blood supply. The vascular supply to the articular–epiphyseal cartilage complex of the distal end of the femur was studied in 27 microfil‐ or barium‐injected and cleared specimens and 24 serially sectioned microangiographic specimens from 27 clinically normal female swine (3.6 to 71.0 kg). Blood vessels supplying the articular‐epiphyseal cartilage complex were consistently restricted to the epiphyseal region and the number of vessels decreased as the pigs increased in weight (p < 0.001). Spontaneous lesions of osteochondrosis (i.e., cartilage necrosis) were initially seen in the first areas of epiphyseal cartilage to become avascular and were associated with necrotic blood vessels. The number and size of foci of necrotic cartilage increased as the pigs increased in weight (p < 0.001). Blood supply to epiphyseal cartilage from cartilage canal vessels was surgically interrupted in a highly vascular area of the medial femoral condyle in eight additional 23‐kg female swine. This procedure resulted in necrosis of blood vessels within cartilage canals followed by necrosis of surrounding cartilage, lesions that appeared to be identical to early spontaneous lesions of osteochondrosis. These results suggest that the viability of epiphyseal cartilage in the articularepiphyseal cartilage complex is highly dependent on an adequate blood supply from cartilage canal vessels, and strongly implicates a defect in blood supply in the pathogenesis of osteochondrosis.
Effect of extracellular fatty acids on lipid metabolism in cultured rabbit articular chondrocytes
Authors: Nagao Masato , Ishii Seiichi , Murata Yoshihisa , Akino Toyoaki
Published: February 2005

Rabbit articular chondrocytes were cultured for 8 h in the presence of various concentrations (5–500 μM) of [14C] oleic, [14C] linoleic, and [3H] arachidonic acids. The radioactive unsaturated fatty acids were incorporated into triacylglycerol (TG) and phosphatidylcholine (PC) in a concentration‐dependent manner; more fatty acids were incorporated into TG than into PC, at higher concentrations of extracellular fatty acids. Among these fatty acids, arachidonic acid was incorporated into TG much more than into PC, in spite of a very low concentration of arachidonic acid in TG. After transfer of the labeled cells to maintenance medium, the radioactivity in TG declined rapidly and [3H] arachidonic acid radioactivity in PC increased continuously during the chase time periods. Palmitoyl‐unsaturated species were mainly formed in PC when cultured at a concentration of 5 μM of each fatty acid. However, when cultured at 500 μM, unsaturated‐unsaturated species, specific for each unsaturated fatty acid were actively formed. These findings indicate that (1) fatty acid composition of TG and PC in articular chondrocytes is influenced by the degree of fatty acid supply, (2) formation and turnover of TG plays a role in fatty acid metabolism of cells, and (3) fatty acid pairing in PC is modulated by extracellular fatty acid concentrations.
Fatigue rates of vastus medialis oblique and vastus lateralis during static and dynamic knee extension
Authors: Grabiner M. D. , Koh T. J. , Miller G. F.
Published: February 2005

Fatigue rates of the vastus medialis oblique and vastus lateralis muscles were compared from static and dynamic exercise. Based upon clinical observations, it was expected that the vastus medialis oblique would demonstrate greater fatigability than the vastus lateralis. However, based upon physiological and morphological considerations, it was expected that the vastus lateralis would exhibit greater fatigability than the vastus medialis oblique. In the static exercise condition, nine subjects—having no history of knee problems—maintained an isometric knee extension torque at 30 and 60% of their maximum value until exhaustion, during which time electromyography (EMG) data were collected every 10 s. The knee angle was 20° flexion. In the dynamic exercise condition, a different group of seven subjects performed exercise sets consisting of eight cycles of concentric‐eccentric knee extension, with a resistance equal to 40% of the maximum isometric value. The range of motion was restricted to the terminal 30° of knee extension. Each set of eight repetitions was followed by a 1 s 50% maximum isometric knee extension, during which time EMG data were collected. The raw EMG data were numerically processed to extract the median frequency of the power density spectrum, which has been shown to reflect the metabolic processes associated with fatigue. Linear regression generated a slope coefficient representing the rate of change of the median frequency, with respect to contraction duration for each subject, muscle, and condition. Analyses of variance, with repeated measures from both exercise conditions suggest that “short‐arc” quadriceps exercise did not selectively fatigue either the vastus medialis oblique or vastus lateralis, thereby supporting neither clinical nor physiological expected outcomes. Therefore, the clinical contention that short‐arc quadriceps exercises selectively strengthen the vastus medialis oblique is questioned.
Relationship between lower limb dynamics and knee joint pain
Authors: Radin Eric L. , Yang King H. , Riegger Cheryl , Kish Vince L. , O'Connor John J.
Published: February 2005

To test the hypothesis that appropriate and timely neuromuscular control of limb motions plays an important role in the preservation of joint health, we kinematically and kinetically examined the behavior of the legs of young adult subjects at heel strike during natural walking. We compared a group of 18 volunteers, who, we presumed, were preosteoarthrotic because of mild, intermittent, activity‐related knee joint pain, with 14 age‐matched asymptomatic normal subjects. The two groups of subjects exhibited similar gait patterns with equivalent cadences, walking speeds, terminal stance phase knee flexion, maximum (peak) swing angular velocity, and overall shape of the vertical ground reaction. However, our instrumentation detected statistically significant differences between the two groups within a few milliseconds of heel strike. In the knee pain group, the heel hit the floor with a stronger impact in this brief interval. Just before heel strike, there was a faster downward velocity of the ankle with a larger angular velocity of the shank. The follow‐through of the leg immediately after heel strike was more violent with larger peak axial and angular accelerations of the leg echoed by a more rapid rise of the ground reaction force. This sequence of events represents repetitive impulsive loading, which consistently provoked osteoarthrosis in animal experiments. We refer to this micro‐incoordination of neuromuscular control not visible to the naked eye as “microklutziness.”
Macrophage exposure to polymethyl methacrylate leads to mediator release and injury
Authors: Horowitz Stephen M. , Gautsch Thomas L. , Frondoza Carmelita G. , Riley Lee
Published: February 2005

To understand further the role of macrophages in the loosening of cemented arthroplasty, several in vitro effects of polymethyl methacrylate (PMMA) particle exposure in these cells were studied. The kinetics of arachidonic acid and derived inflammatory mediator release was characterized following macrophage exposure to either PMMA or control polystyrene particles. Temporal release of radiolabeled products by [14C]arachidonate–labeled cells was determined by sequential scintillation counting. Significant dosedependent release of arachidonic acid mediators by macrophages was observed within half an hour of exposure to either PMMA or styrene particles. Unexposed control cells incubated in media alone did not release detectable amounts of radiolabeled products. The leakage of intracellular lactate dehydrogenase (LDH), a marker of cell injury, was detected spectrophotometrically 4 h following exposure to PMMA but not styrene. PMMA‐induced LDH release was dose depedent. In contrast, polystyrene exposure failed to increase LDH release above unexposed control cells. These in vitro studies reveal that macrophages rapidly released arachidonic acid and derived inflammatory mediators in response to both PMMA and styrene particles. However, cells exposed to PMMA are lethally damaged, as reflected by the subsequent leakage of their intracellular LDH. We propose that a similar sequence of events may occur when macrophages encounter PMMA particles at the bone‐cement interface. This is characteristic of a foreign body granulomatous response.
Estimation of mechanical properties of cortical bone by computed tomography
Authors: Snyder Susan M. , Schneider Erich
Published: February 2005

It is difficult to assess from conventional x‐rays the amount of loading that a bone can tolerate. The question therefore was asked whether the mechanical properties of cortical bone could be estimated by using a computed tomography (CT) system typically employed in the clinical setting. In vitro cross sectional diaphyseal scans of adult human tibiae were made using a GE 9800 scanner and linear attenuation coefficients determined in several regions of the central cross sections. Samples from the mid‐diaphyses of these tibiae were harvested, tested in three‐point bending to failure, and mechanical properties as well as density and ash fraction determined. The respective relationships between CT measurements, mechanical properties and physical properties were calculated using regression analysis. In addition a solid calibration phantom (tricalciumphosphate) was scanned to evaluate the variability of CT measurements. The physical parameters measured in this study were found to be comparable with data from other authors but correlations coefficients with CT data: r = 0.55 (Young's modulus), r = 0.50 (strength), r = 0.65 (apparent density) and r = 0.46 (ash fraction). The correlation coefficients of these regressions for both linear and power fits were not significantly different. A high linear correlation (r = 0.99) was found between the chamber densities and the measured attenuation coefficients, but accuracy varied between 2 and 6%. The small range of specimen mechanical properties as well as the limitations inherent with the methods employed may explain these results. We conclude that clinical equipment as used in this study is not sufficient to accurately estimate the mechanical properties of cortical bone.
Experimental transplantation of the swarm rat chondrosarcoma into bone: Radiological and pathological studies
Authors: Kenan Samuel , Steiner German C.
Published: February 2005

The Swarm rat chondrosarcoma has been the subject of extensive biochemical studies. However, to our knowledge, there are no previous reports in the literature on transplantation of this tumor into bone. This article describes the natural history of the tumor when implanted into the bone of the rat, and correlates its histological growth pattern with its radiological appearance. Our results showed that the tumor grows slowly in the bone. The rate of intramedullary growth, however, was variable and was not the same in all the animals. Its growth pattern resembles human chondrosarcoma, with extensive invasion of the marrow and cortex. In the first few weeks after implantation, the only radiological changes noted were mild medullary radiopacities. At a later stage, 12–14 weeks postimplantation, as the tumor infiltrated the bone, significant radiological abnormalities were observed in the medullary cavity and cortex. Periosteal reaction was seen after the tumor invaded the cortex with the production of a soft‐tissue mass. Distant dissemination was rare; only 1 of 24 rats developed pulmonary metastases. The Swarm rat chondrosarcoma is a well‐differentiated malignant tumor that histologically resembles welldifferentiated human chondrosarcoma. Transplanted into bone, it may be useful as an experimental model for comparative studies with human chondrosarcoma.
An anatomic basis for spinal instability: A porcine trauma model
Authors: Oxland T. R. , Panjabi M. M. , Southern E. P. , Duranceau J. S.
Published: February 2005

To determine the anatomic basis for spinal instabilities, 16 porcine cervical spine specimens were subjected to a well‐defined sagittal plane trauma. The multidirectional instability of each specimen was measured before and after trauma. Detailed anatomic dissections were performed on each traumatized specimen to quantitate the extent of injury to several distinct anatomic structures and columns. Multiple regression models were constructed to determine which anatomic structures and columns correlated best with each multidirectional instability. Flexion instability correlated best with injury to the interspinous/supraspinous ligaments and the ligamentum flavum. Extension instability correlated best with anterior longitudinal ligament and pedicle injury. Axial rotation instability correlated best with anterior disc–end‐plate and capsular ligament injuries, while lateral bending instability correlated best with posterior disc–end‐plate injuries. Anterior column injuries correlated best with extension, axial rotation, and lateral bending instabilities, while posterior column injuries correlated best with flexion instability. Finally, individual anatomic structural injuries had higher correlations with multidirectional instabilities than did the injuries defined by the anatomic columns.
The effect of oxygen tension on proteoglycan synthesis and aggregation in mammalian growth plate chondrocytes
Authors: Clark Charles C. , Tolin Brad S. , Brighton Carl T.
Published: February 2005

Growth plate chondrocytes isolated from the proliferative and hypertrophic zones of bovine costochondral junctions were grown in vitro in the presence of various oxygen tensions ranging from 3 to 60%. Using [35S] sulfate as an index of glycosaminoglycan synthesis, incorporation was found to be maximal at 21% O2. In contrast, proteoglycan aggregation under the same conditions was found to be maximal at 3% O2. There were no consistent differences in response between cells from the different morphologic zones even though they are exposed to different oxygen tension in situ. These results show that proteoglycan synthesis and aggregation in growth plate chondrocytes in vitro are differentially affected by the ambient oxygen environment.
Evaluation of a new injury model to study medial collateral ligament healing: Primary repair versus nonoperative treatment
Authors: Weiss Jeffrey A. , Woo Savio L‐Y. , Ohland Karen J. , Horibe Shuji , Newton Peter O.
Published: February 2005

The medial collateral ligament (MCL) of the rabbit left hindlimb was ruptured by a rod placed beneath it, resulting in a “mop‐end” tear of the ligament substance with simultaneous injury to the insertion sites. Using this model, we compared primary ligament repair and nonoperative treatment using biomechanical and histologic techniques at time zero, 10 days, and 6 and 12 weeks postoperatively. Biomechanical evaluation included measurement of varus‐valgus (V‐V) knee rotation, in situ load on the MCL, and tensile testing of the femur‐MCL‐tibia complex (FMTC). The V‐V rotation of all experimental knees decreased over time. At 12 weeks, V‐V rotation of experimental knees was still 1.3 times larger than that of controls. Primary repair initially decreased V‐V rotation, but at 6 and 12 weeks there was no statistical difference between operated and nonoperated knees. The in situ load on the MCL followed the same trends. There was no significant effect of MCL repair on any of the tensile properties. However, postoperative healing time significantly improved the FMTC structural properties in both experimental groups. Failure modes of the FMTCs and histologic sections of the ligament insertion sites indicated that after injury the ligament insertion to bone recovered more slowly than the ligament substance. Tensile testing of the FMTC showed that even at 12 weeks postoperatively the mechanical properties of the healed ligament material remained significantly different from those of the controls.
Tensions in the anterior and posterior cruciate ligaments of the knee during passive loading: Predicting ligament loads from in situ measurements
Authors: Vahey J. W. , Draganich L. F.
Published: February 2005

Cruciate ligament tensions were predicted for anteroposterior (AP) tibial translation at 20°, 30°, 80°, and 90° of knee flexion based on in vitro measurements from six cadaver knees. A three‐dimensional trigonometric equation was derived to calculate ligament tension as functions of AP force applied to the tibia and knee flexion angle (KFA). AP forces ≤ 150 N were applied. Ligament tension increased with applied AP force. The relationship between ligament tension and applied AP force appeared linear, but a Hotteling's T2 test failed to demonstrate a linear relationship. Tensions in the anterior cruciate ligament (ACL) attained magnitudes of ≅ 140 N. Tensions in the posterior cruciate ligament (PCL) attained magnitudes of ≅ 220 N. An analysis was performed to determine the sensitivity of ligament tension to hypothetical errors in the experimentally measured parameters used to compute ligament tension. The new method we report can be used to determine tensions in the ligaments of the knee or other joints for various loading conditions.
Identification of human intervertebral disc stromelysin and its involvement in matrix degradation
Authors: Liu J. , Roughley P. J. , Mort J. S.
Published: February 2005

Human intervertebral disc when maintained in organ culture released a latent casein‐degrading metalloproteinase into the medium in a manner analogous to cultures of human cartilage. This enzyme was demonstrated to be immunologically identical to prostromelysin. It was also found that the amount of procollagenase secreated by both cartilage and disc cells was considerably less than that of prostromelysin. Tissue extraction confirmed that the low level of procollagenase observed was not due to retention of the enzyme within the tissue. Human intervertebral disc link proteins were found to possess the same N‐termini as those of their counterparts in human articular articular cartilage, whee it appears that stromelysin is responsible for generating molecular heterogeneity. These results suggest that intervertebral disc cells are capable of secreting prostromelysin, which can become activated within the extracellular matrix and hence contribute to the age‐related and degenerative changes in the disc.
Modulation of bone loss during disuse by pulsed electromagnetic fields
Authors: Skerry T. M. , Pead M. J. , Lanyon L. E.
Published: February 2005

The effect of pulsed electromagnetic fields (PEMFs) on bone loss associated with disuse was investigated by applying 1.5 Hz repetitions of 30 ms bursts of asymmetric pulses, varying from +2.5 to −135 mV, to bones deprived of their normal functional loading. The proximal portion of one fibula in each of a group of ovariectomised adult female beagle dogs was isolated from functional loading in vivo by proximal and distal osteotomies. Comparison of these prepared bones with their intact contralateral controls after 12 weeks, showed a 23% reduction in cross‐sectional area. In similarly prepared bones exposed to PEMFs for 1 h per day, 5 days per week, this bone loss was substantially and significantly reduced to 9% (p = 0.029). There was no evidence of any new bone formation on the periosteal surface of prepared fibulae in treated or untreated situations. PEMF treatment was not associated with any significant change in number of osteons per mm2 formed within the cortex of the bones, their radial closure rate, or their degree of closure. The modulation in loss of bone area associated with exposure to PEMFs can, therefore, be inferred to be due to a reduction in resorption on the bone surface.