bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular shape and pressure may mediate mechanical control of tissue composition in tendons
Authors: Giori N. J. , Beaupré G. S. , Carter D. R.
Published: February 2005

In vivo studies have suggested that mechanical factors are involved in the regulation of the morphology and biochemical composition of tendons that wrap around bones. In these tendons fibrocartilage is found in the segment wrapped around the bone, and tendon far from the bone displays normal tendon histomorphology. Recent in vitro studies have shown that intermittently loaded connective tissue cells are sensitive to changes in cellular shape and hydrostatic pressure: stretching and distortion of the cells enhances production of fibrous matrix and hydrostatic pressure enhances production of cartilaginous matrix. We used finite‐element analysis to determine whether the regions of increased development of cartilaginous matrix in tendons that wrap around bones correspond to regions in which tendon cells are subjected to higher pressures, and whether the maintenance and rearrangement of fibrous extracellular matrix in these tendons is associated with regions of stretching and distortion of cells. We found that regions of cartilaginous matrix and fibrous matrix formation and turnover correlate well with patterns of hydrostatic compressive stress and distortional strain in the tendon. Although further experiments clearly are needed to establish the predictive value of our approach, hydrostatic stress and distortional strain history—parameters intimately related to changes in cellular pressure and shape, respectively—appear to be important tissue‐level mechanical stimuli that regulate cartilaginous and fibrous matrix composition of connective tissues.
In vitro biomechanical analysis of suture methods for flexor tendon repair
Authors: Noguchi Masahiko , Seiler John G. , Gelberman Richard H. , Sofranko Richard A. , Woo Savio L‐Y.
Published: February 2005

This study was designed to compare five different suture methods that are used clinically for tendon repair. The flexor digitorum profundus tendons from the digits of adult mongrel dogs and adult human cadavers were used as models. The tendons in zone II of the hand, defined as the region from the distal palmar crease to the insertion of the flexor digitorum superficialis tendon at the middle phalanx, were transected and then were repaired by one of the suture methods developed by Kessler, Tsuge, Tajima, Savage, or Lee. The gliding function and tensile properties of the repaired tendons were evaluated biomechanically at time zero. The Tajima and Savage methods produced better gliding function than the other techniques. In the canine specimens that had been repaired by one of these two methods, the rotation of the distal interphalangeal joint was more than 60% of the rotation of the canine control specimens; only the Savage technique produced a rotation 124% that of the human control specimens. After the Tajima repair, the rotation of the proximal interphalangeal joint was 113% that of the canine control specimens and 157% that of the human controls. In the canine specimens that had had the Tajima or Savage repair, excursion of the tendon was greater than 55% that of the controls. The tendons repaired by the Savage method tolerated a significantly higher ultimate load to failure (14 and 25% that of the canine and human control specimens, respectively) than the other methods. Of the suture methods that were tested, the Savage technique provides sufficiently satisfactory gliding function and has enough initial stiffness and strength that it may be able to withstand early active mobilization following primary repair of flexor tendons.
Method to determine collagen density distributions in fibrous tissues
Authors: Mommersteeg T. J. A. , Kauer J. M. G. , Huiskes R. , Blankevoort L.
Published: February 2005

We present a method for the measurement of hydroxyproline density distributions, as an estimate for collagen density distributions, in fibrous tissues such as ligments and tendons. To evaluate this method, a single flexor tendon of a human hand was divided into seven tissue locations. Triplicate determinations of the dry weight tissue mass, volume, and hydroxyproline mass were made at each location: two samples were analyzed at the same time (a and b) and one was analyzed later (c). The intralocation variation is an estimate for the measurement error variance, which indicates both the precision (a compared with b) and the repeatability (b compared with c) of the technique for determination of volume, dry weight tissue mass, hydroxyproline concentration, and hydroxyproline density. The precision was about 5% for all variables, and the repeatability ranged from 1.5–4.3%. In comparison with the interlocation variations, the error variances were small, except for collagen concentration. This indicates that despite the measurement errors, differences in hydroxyproline density can be detected within fibrous tissues with the proposed method. The use of only a single tendon is adequate to evaluate the measurement error of the method, but more tendons should be measured to generalize the absolute values of the variables.
Enhancement of bone growth into metal screws implanted in the medullary canal of the femur in rats
Authors: Hazan R. , Oron U.
Published: February 2005

The kinetics of growth of bone into control (nontreated) and heat‐treated screws made of stainless steel (type 316L) and Ti‐6Al‐4V, implanted in the medullary canal of the femur in rats, were studied by mechanical, histological, and biochemical methods. A progressive and significant increase in the ingrowth of bone, as reflected by interfacial shear strengths of the screws, was measured with time after implantation. At all time intervals for as long as 35 days after implantation, the shear strength of the heat‐treated Ti‐6Al‐4V and stainless‐steel screws was significantly higher than (1.6–3.4 times) that of the control screws. The specific activity of alkaline phosphatase in extracts of tissue from around the implanted screws peaked 6 days after insertion, with significantly higher values at 5, 6, and 7 days postoperatively for the heat‐treated screws than for the controls. The extent of calcification also was higher at all time intervals for the heat‐treated screws than for the controls. The histological evaluation of formation of bone between the ridges of the implanted screw corroborated the mechanical and biochemical measurements. At each time interval, a more mature bone was noted around the heat‐treated screws than around the controls. It was concluded that the heat treatment of metal implants before insertion can result in augmentation of osseous ingrowth 1.6–5.3 times that into control implants in an in vivo experimental model.
Pulsed magnetic fields improve osteoblast activity during the repair of an experimental osseous defect
Authors: Canè Valerio , Botti Paolo , Soana Silvana
Published: February 2005

The influence of pulsed low‐frequency electromagnetic fields (PEMFs) on bone formation was investigated in studies of the healing process of transcortical holes, bored at the diaphyseal region of metacarpal bones of six adult horses, exposed for 30 days to PEMFs (28 G peak amplitude, 1.3 ms rise time, and 75 Hz repetition rate). A pair of Helmholtz coils, continuously powered by a pulse generator, was applied for 30 days to the left metacarpal bone, through which two holes, of equal diameter and depth, had been bored at the diaphyseal region. Two equal holes, bored at the same level in the right metacarpal and surrounded by an inactive pair of Helmholtz coils, were used as controls. All horses were given an intravenous injection of 25–30 mg/kg of tetracyline chloride on the 15th and again on the 25th day after the operation and were killed 5 days later. The histomorphometric analysis indicated that both the amount of bone formed during 30 days and the mineral apposition rate during 10 days (deduced from the interval between the two tetracycline labels) were significantly greater (p < 0.01 and p < 0.0001, respectively) in the PEMF‐treated holes than in the controls. As did a previous investigation, these preliminary findings indicate that PEMFs at low frequency not only stimulate bone repair but also seem to improve the osteogenic phase of the healing process, at least in our experimental conditions.
Proteoglycan synthesis in canine intervertebral discs after long‐distance running training
Authors: Puustjärvi K. , Lammi M. , Kiviranta I. , Helminen H. J. , Tammi M.
Published: February 2005

The alterations and distribution of proteoglycan (PG) synthesis in the intervertebral discs of young dogs exercised with long‐distance running (40 km/day) were studied with a method based on image analysis of tissue sections. Ten dogs were run on a treadmill daily for 55 weeks, and 10 dogs from the same litters served as controls. The daily running distance gradually was increased to 40 km and was maintained at that level for the final 15 weeks. Midsagittal disc segments C7‐T1, T8‐9, and L1‐2 were labeled with 35SO4, and histological sections of the segments were apposed against autoradiographic film to determine the synthesis of PGs. Next, the same sections were stained with safranin O to estimate possible alterations in PG concentration. The radiographs and stained sections were digitized with a flatbed scanner and measured by image analysis. The lumbar discs of the runners displayed a significantly lower rate of 35SO4 incorporation, while a tendency toward enhanced incorporation was seen in the cervical and thoracic discs. Safranin O staining showed a pattern just opposite to 35SO4 incorporation: decreased staining in the cervical and thoracic discs and increased staining in the lumbar disc of the runners. The results demonstrate qualitatively different influences of long‐term running training on PG metabolism at the cervical, thoracic, and lumbar levels in young dogs.
Electromyographic studies of the lumbar trunk musculature during the generation of low‐level trunk acceleration
Authors: Marras W. S. , Mirka G. A.
Published: February 2005

An understanding of how the support mechanisms of the spine behave during lifting may yield insight into the loading of the spine under occupational conditions and help shed light on the etiology of low‐back disorders. Previous controlled laboratory studies of spinal loadings have been limited to isometric and isokinetic conditions. To evaluate the behavior of the trunk during acceleration, we recorded intra‐abdominal pressure and trunk muscle activities during low‐level acceleration. Twenty subjects performed controlled accelerations of the trunk under different trunk loading conditions. Muscle activity decreased as acceleration increased; however, the rate of decrease differed among muscles (mean decrease, ⩽1% of maximum per 10°/s2 increase in acceleration), with the activity of the erector spinae muscles decreasing the most (1.88% of the maximum per 10°/s2 increase in acceleration). No changes in intra‐abdominal pressure were found as a function of acceleration. Relative coactivation of the muscles increased; however, this was a function of increases in trunk velocity and torque.
The effects of acidosis and alkalosis on long bone vascular resistance
Authors: Davis Timothy R. C. , Wood Michael B.
Published: February 2005

This study used an ex vivo perfusion model to investigate the direct effects of acidosis and alkalosis on the vascular resistance of the canine tibia. Baseline vascular resistance (BVR) and the vascular smooth muscle response to bolus doses of norepinephrine (NE) (0.025–3.2 nmol) and periarterial sympathetic nerve stimulation (NS) (10–25 Hz: 9 V, 2 ms pulses, 10 s) were studied. In Group I, these parameters were measured at normal pH (duration 7.34–7.44) and then during acidosis (pH 7.2–7.33). In Group II, they were measured at normal pH and then during alkalosis (pH 7.47–7.58). In Group III (control), they were measured serially at a normal pH. Alkalosis increased BVR by 56% (p < 0.0001). Acidosis attenuated (18% reduction) and alkalosis enhanced (66% increase) the vasoconstrictor action of NE (p < 0.0001). Acidosis also attenuated (11% reduction) the effect of sympathetic NS (p = 0.012). It is concluded that perfusion pH influences the sensitivity of long bone resistance vessels to circulating NE and sympathetic NS. Thus, local concentration of hydrogen ions may provide bone with a mechanism to autoregulate blood flow.
Primary culture of microvascular endothelial cells from canine meniscus
Authors: Miller Raymond R. , Rydell Pamela A.
Published: February 2005

Microvascular endothelial cells were isolated and cloned from canine knee menisci. Intitially, the endothelial cell colonies in culture exhibited a cobblestone morphology. With passage and time, these cultures adopted a fibroblastic or fusiform morphology. The endothelial nature of the cells was demonstrated by positive immunostaining with antibodies to von Willebrand factor, laminin, and type‐IV collagen and by capillary‐like tube formation on Matrigel. These endothelial cells could be passaged as many as 10 times with retention of the endothelial characteristics. This population of meniscal microvascular endothelial cells will facilitate studies on the role of blood vessels in meniscal repair.
Calcium‐dependent neutral proteinase (calpain) in fracture healing in rats
Authors: Nakagawa Yasuaki , Shimizu Katsuji , Hamamoto Takashi , Suzuki Kiichi , Ueda Michiko , Yamamuro Takao
Published: February 2005

Calpain refers to Ca2+‐dependent neutral cysteine proteinase, which originally was thought to be an intracellular proteinase but recently has been shown to function extracellularly as well. This report describes the immunohistochemical demonstration of calpain and biochemical changes in the amount of calpain during fracture healing in rats. The tibiae of 6‐week‐old Wistar rats were fractured, and calluses were obtained 5–28 days after fracture. A frozen section of the fracture callus was stained by the immunoperoxidase method with use of polyclonal antibodies of calpains I and II. Positive staining was noted with the anti‐calpain II antibody in the perivascular areas, chondrocytes, and cartilage matrix in calluses at 5, 7, and 10 days. Less intense staining was seen in older calluses. The caseinolytic activity of calpain II reached its maximum on the 5th day, was high on the 7th and 10th days, and decreased rapidly thereafter. The quantity of calpain II was dependent on the process of fracture healing. It was concluded that calpain was working as one of the matrix proteinases in fracture callus.
Articular cartilage thickness and glycosaminoglycan distribution in the young canine knee joint after remobilization of the immobilized limb
Authors: Kiviranta Ilkka , Tammi Markku , Jurvelin Jukka , Arokoski Jari , Säämänen Anna‐Marja , Helminen Heikki J.
Published: February 2005

The recovery of articular cartilage from atrophy induced by joint immobilization was investigated in immature dogs. In a previous study, we showed that 11 weeks of immobilization of the knee (stifle) joint of young dogs reduced the concentration of articular cartilage glycosaminoglycans (GAGs) by 13–47%. In the present study, right hindlimbs from six female beagles were immobilized for 11 weeks, as in the previous study, and then were remobilized for 15 weeks. Cartilage from the knee joint was compared with cartilage from nonimmobilized knees of eight age‐matched control beagles. Histological samples taken from 11 different locations of the knee joint were stained with safranin O, and microspectrophotometry was used to demonstrate distribution of GAGs in the tissue. After remobilization, GAG concentration was restored in the patellofemoral region and tibial condyles. On the summits of the femoral condyles, and especially at the periphery of the femoral condyles, GAG concentration remained 8–26% less than the control values. On the summits, the thickness of the uncalcified cartilage was as much as 15% less than in the age‐matched controls. Consequently, the changes induced by unloading were reversible to a great extent, but a full restoration of articular cartilage was not obtained at all sites of the knee joint within the 15 weeks of remobilization. Immobilization of the skeletally immature joint therefore may affect the development of articular cartilage in such a way that very slow recovery or permanent alterations are induced.
Site‐specific cartilage changes in murine degenerative knee joint disease induced by iodoacetate and collagenase
Authors: Van Osch G. J. V. M. , Van Der Kraan P. M. , Van Den Berg W. B.
Published: February 2005

Degenerative joint disease was induced in the knee joints of mice by intraarticular injection of two different stimuli: iodoacetate and highly purified collagenase. Proteoglycan synthesis was measured in vivo at different time points in four topographical areas of the knee joint (central and peripheral parts of the patella and central parts of the medial and lateral tibial plateaus) and was compared with histological observations of localized damage to the joint. In vitro incubation with iodoacetate had a direct effect on proteoglycan metabolism. Intra‐articular injection of iodoacetate in vivo inhibited the proteoglycan synthesis in cartilage from the central part of the patella. In the peripheral part of the patella, inhibition on day 1 was followed by stimulation of synthesis on days 3–30. Proteoglycan synthesis also was inhibited in the central parts of the medial and lateral tibial plateaus. The areas with inhibited synthesis had loss of safranin O staining on histology. In vitro incubation with collagenase did not have a direct effect on the proteoglycan metabolism of intact cartilage; this led to the assumption that osteoarthritis after injection of collagenase is caused by ligamentous injury, which leads to an unstable joint. Injection of collagenase in vivo stimulated the proteoglycan synthesis in cartilage from the central and peripheral parts of the patella. In an early stage of the process, the cartilage from the tibial plateaus also was slightly stimulated. From 30 days after injection of collagenase, synthesis in the lateral tibial plateau decreased, whereas synthesis in the patella remained stimulated and synthesis in the medial tibial plateau remained normal. On histology, cartilage from the patella and the medial tibial plateau had a normal appearance, and there was loss of cartilage from the lateral tibial plateau. Our data indicate that the variation in response of cartilage from different anatomical areas of the knee joint depends on the stimulus used. This suggests that the location of cartilage damage depends on the etiological factor responsible for induction of the osteoarthritic process.
Radial tie fibers influence the tensile properties of the bovine medial meniscus
Authors: Skaggs D. L. , Warden W. H. , Mow V. C.
Published: February 2005

Although collagen fibers are arranged predominantly in the circumferential direction in the knee meniscus, there is evidence for radially oriented fibers within human menisci. A bovine medial meniscus model was used to study the hypothesis that radial fibers alter the radial tensile properties of the meniscus. The architecture of the collagen network and tensile properties of the bovine medial meniscus were examined; attention was given to large “radial tie fibers” and their regional variation. Menisci were sectioned serially into slices 400 μm thick. Polarized light microscopy showed that the distribution of radial tie fibers varied greatly among the anterior, central, and posterior regions. These radial tie fibers were larger and more frequent in the posterior region. Radial fibers persisted over many adjacent sections with similar architecture, which led to our hypothesis that they may be arranged in continuous sheets in which the morphology varies by region. Radially oriented specimens for tensile testing were grouped according to the number of radial tie fibers (full, partial, and no fiber) and region (anterior, central, and posterior). Uniaxial tensile testing was performed on a testing machine at a strain rate of 0.00017 sec−1 until failure. The tensile modulus, ultimate tensile stress, and ultimate tensile strain were determined. The presence of radial tie fibers in the specimen had a significant effect on the tensile modulus and ultimate tensile stress. Specimens containing full radial tie fibers were stiffest and failed at the lowest strains; in specimens from the posterior region, the tensile modulus was 392%, the ultimate tensile stress was 314%, and the ultimate tensile strain was 68% that of the specimens with no radial fibers. In no‐fiber specimens, the tensile modulus in the posterior region was 225% of the modulus in the anterior region, and the ultimate tensile strain in the posterior region was 68% that of the strain in the anterior region. The abundance of radial tie fibers in the posterior region seems to contribute to the increased stiffness of this region. The preferential stiffening of the posterior region by these radial fibrous sheets may be well suited to the manner in which the bovine medial meniscus functions in load‐bearing.
Kinematics of the normal trapeziometacarpal joint
Authors: Imaeda Toshihiko , Niebur Glen , Cooney William P. , Linscheid Ronald L. , An Kai‐Nan
Published: February 2005

Motion of the trapeziometacarpal joint was studied in 12 hands from fresh human cadavera. By use of a magnetic tracking system, a full range of motion of the first metacarpal was analyzed with respect to a defined trapezial coordinate system. The traces of the reference points on the head and base of the first metacarpal were monitored, and the instantaneous centers of rotation were calculated. During circumduction, the reference points on the head and base followed elliptical paths but in opposite directions. The average instantaneous center of circumduction was at approximately the center of the trapezial joint surface. In flexion‐extension, the axis of rotation was located within the trapezium, and the path of the head was identical to the path of the base. In abduction‐adduction, the axis of rotation was located distal to the trapezium within the base of the first metacarpal, and the base and head moved in opposite directions. There was no single center of rotation: rather, instantaneous motion occurred reciprocally between these centers of rotation within the trapezium and metacarpal base in the normal thumb. This changing instantaneous center of rotation results in a unique pattern of motion which is related to congruent, tightly constrained joint surfaces of two reciprocal saddle joints and to precisely positioned extraarticular ligaments.
Osteoarthritis in cynomolgus macaques: A primate model of naturally occurring disease
Authors: Carlson Cathy S. , Loeser Richard F. , Jayo Manuel J. , Weaver David S. , Adams Michael R. , Jerome Christopher P.
Published: February 2005

The objective of the present study was to determine if naturally occurring osteoarthritis of the knee joints that is similar to the condition in humans develops in cynomolgus macaques. Knee joints from 58 young adult (mean age, 7.4 years) female cynomolgus macaques were studies with x‐ray densitometry, high‐detail radiography, and histology. The animals studied were subjects in a triad designed to examine the effects of the administration of sex steroids on atherosclerosis; except for a control group, the monkeys had been either ovariectomized or treated with sex steroids for 2 years. Therefore, the data were analyzed to determine if these treatments, both of which can influence bone density, affected the severity of osteoarthritis. There was a high prevalence of osteoarthritic lesions, morphologically similar to those seen in humans. Bone changes were more common and severe than cartilage changes and morphologically appeared to precede the cartilage changes. Treatment with testosterone resulted in increased body weight, body mass index, and bone mineral content in the femur and tibia but did not affect the severity of osteoarthritis. These data indicate that naturally occurring osteoarthritis developed in the knee joints of cynomolgus macaques; these animals may be a useful model for the study of osteoarthritis in humans.
Healing of the rabbit medial collateral ligament following an o'donoghue triad injury: Effects of anterior cruciate ligament reconstruction
Authors: Engle Carolyn P. , Noguchi Masahiko , Ohland Karen J. , Shelley Franz J. , L‐Y. Woo Savio
Published: February 2005

The effects of healing time and anterior cruciate ligament reconstruction on healing of the medial collateral ligament and stability of the knee joint were evaluated in a rabbit model of an O'Donoghue triad injury (rupture of the medial collateral ligament with removal of the anterior cruciate ligament and part of the medial meniscus). At time 0 and at 6 and 12 weeks postoperatively, the anterior‐posterior translation and varus‐valgus rotation of the knee, the structural properties of the femur‐medial collateral ligament‐tibia complex, and the mechanical properties of the substance of the medial collateral ligament were evaluated. Although anterior‐posterior translation increased significantly with time, we could not demonstrate a significant temporal effect on varus‐valgus rotation. The ultimate load, elongation at failure, and energy absorbed to failure improved with time. In addition, with time, failure of the complex occurred more often in the ligament substance than at the osseous insertion. Because healing time did not affect the cross‐sectional area or modulus of the medial collateral ligament, the improved structural properties of the complex resulted not from improvements in the mechanical properties of the tissue but rather from healing of the tibial insertion site. By 12 weeks, the reconstructed knees had only minor signs of osteoarthrosis on the tibiofemoral surfaces; this is in contrast to the findings in anterior cruciate ligament‐deficient knees in our earlier study. Initially, reconstruction also improved stability of the knee. Additionally, at 12 weeks, the stiffness of the complexes from the reconstructed group was 1.3 times that of the anterior cruciate ligament‐deficient group (p < 0.05), and the ultimate load had increased by a factor of 1.6 (p < 0.05). Our findings demonstrate that reconstruction of the anterior cruciate ligament in the rabbit helps to stabilize the joint, improves healing of the medial collateral ligament, and may decrease the incidence of early‐onset osteoarthrosis after an O'Donoghue triad injury.
Mechanical Properties of Canine Articular Cartilage Are Significantly Altered Following Transection of the Anterior Cruciate Ligament
Authors: Setton L. A. , Mow V. C. , Müller F. J. , Pita J. C. , Howell D. S.
Published: February 2005

The compressive, tensile, and swelling properties of articular cartilage were studied at two time periods following transection of the anterior cruciate ligament in the knee of greyhound dogs. An experimental protocol was designed to quantify the essential equilibrium and biphasic material properties of cartilage in tension, compression, and shear, as well as the parameters of isometric swelling behavior. All properties were measured at several sites to elicit differences between sites of frequent and less frequent contact. Hydration was determined at each site and was compared with the material properties of cartilage from corresponding sites. There were extensive changes in all compressive, tensile, and swelling properties of cartilage after transection of the anterior cruciate ligament. Twelve weeks after surgery, the intrinsic moduli were reduced significantly in compression (approximately 24% of control values), tension (approximately 64%), and shear (approximately 24%), and the hydraulic permeability was elevated significantly (approximately 48%). Significant increases in hydration (approximately 9%) also were observed, as well as a strong correlation of hydration with hydraulic permeability. The pattern of these changes was not found to differ with site in the joint, but significant differences were observed in the magnitude of change for cartilage from the femoral groove and the femoral condyle. The pattern and extent of changes in the material properties following transection of the anterior cruciate ligament indicate that altered loading of the joint severely compromises the overall mechanical behavior of articular cartilage. The observed loss of matrix stiffness in compression, tension, and shear is associated with increases in the deformation of the solid matrix, a diminished ability to resist swelling, and the increase in hydration observed in this study. The increased swelling and elevated water content were related directly to the increase inhydraulic permeability; this suggests an associated loss of fluid pressurization as the load support mechanism in the degenerated cartilage. Without a successful mechanism for repair, damage to the solid matrix may progress and lead to further degenerative changes in the biochemistry, morphology, and mechanical behavior of articular cartilage.
Diurnal fluid changes of lumbar discs measured indirectly by magnetic resonance imaging
Authors: Paajanen Hannu , Lehto Ilkka , Alanen Anu , Erkintalo Minna , Komu Markku
Published: February 2005

The feasibility of magnetic resonance imaging and the magnetization transfer technique for measurement of diurnal fluid changes in lumbar discs was studied with the use of 13 healthy subjects. The diurnal height loss of the subjects ranged from 13 to 21 mm. The disc signal in T2‐weighted magnetic resonance imaging increased as much as 25% after overnight bed rest, presumably due to the enhanced influx of water. The change in magnetization transfer parameters also suggested increased hydration of the disc after bed rest. Magnetic resonance imaging techniques can be used for indirect measurement of the changes in fluid content and the interaction of water with macromolecules in the disc.
Relationship of donor site to chondrogenic potential of periosteumin vitro
Authors: Gallay Stephen H. , Miura Yasushi , Commisso Cinzia N. , Fitzsimmons James S. , O'Driscoll Shawn W.
Published: February 2005

Periosteum has been shownin vitroandin vivoto have a chondrogenic potential that permits it to be used for cartilage regeneration. A useful donor site should have good chondrogenic potential, availability of a large quantity of periosteum, and relative ease of access, and it should be associated with a low rate of morbidity. We hypothesized that the chondrogenic potential of periosteum varies from one bone to another and among different regions of the periosteum from a single bone. A total of 370 periosteal and 37 fascia lata (control) explants were taken from the skull, the ilium, the scapula, the upper, middle, and lower medial proximal tibia, the posterior proximal tibia, and the distal tibia of 2‐month‐old New Zealand rabbits. The explants were cultured for 6 weeks in agarose/Dulbecco's modified Eagle medium to which 10 ng/ml of transforming growth factor‐β1 was added during the first 2 weeks. Skeletal muscle and fascia lata were used as controls. In addition, the thickness, cell density, and total cell count of the cambium layer were measured in 24 explants from the donor sites on the ilium and the upper, middle, and lower proximal tibia. At 6 weeks, histomorphometry and quantitative collagen typing were performed. The periosteal donor sites could be grouped into three categories according to chondrogenic potential: ilium (best), scapula and tibia, and skull (no chondrogenesis). The scapular periosteum was slightly better than that from the tibia. Within the tibia, the upper and middle zones of the proximal region were similar and were slightly better than the lower proximal tibia or the distal tibia. The cellularity of the cambium layer correlated positively with the amount of cartilage as a percentage of the total area. The results of this study indicate that iliac periosteum exhibited the best overall chondrogenic potentialin vitrobut that periosteum from the traditionally used medial proximal tibia also was excellent. Periosteum from the skull was not chondrogenic. The chondrogenic potential of periosteum varies from bone to bone and within the periosteum from one bone. This variation in chondrogenic potential among donor sites may be due to a difference in the total cell count of the cambium layer.
Culture surfaces coated with various implant materials affect chondrocyte growth and metabolism
Authors: Hambleton J. , Schwartz Z. , Khare A. , Windeler S. W. , Luna M. , Brooks B. P. , Dean D. D. , Boyan B. D.
Published: February 2005

The effect on chondrocyte metabolism of culture surfaces sputter‐coated with various materials used for orthopaedic implants was studied and correlated with the stage of cartilage cell maturation. Confluent, fourth‐passage chondrocyts from the costochondral resting zone and growth zone of rats were cultured for 6 or 9 days on 24‐well plates sputter‐coated with ultrathin films of titanium, titanium dioxide, aluminum oxide, zirconium oxide, and calcium phosphate (1.67:1). Corona‐discharged tissue culture plastic served as the control. The effect of surface material was examined with regard to cell morphology; cell proliferation (cell number) and DNA synthesis ([3H]thymidine incorporation); RNA synthesis ([3H]uridine incorporation); collagenase‐digestible protein, noncollagenase‐digestible protein, and percentage of collagen production; and alkaline phosphatase‐specific activity, both in the cell layer and in trypsinized chondrocytes. Cell morphology was dependent on surface material; only cells cultured on titanium had an appearance similar to that of cells cultured on plastic. While titanium or titanium dioxide surfaces had no effect on cell number or [3H]thymidine incorporation, aluminum oxide, calcium phosphate, and zirconium oxide surfaces inhibited both parameters. Cells cultured on aluminum oxide, calcium phosphate, zirconium oxide, and titanium dioxide exhibited decreased collagenase‐digestible protein, noncollagenase‐digestible protein, and percentage of collagen production, but [3H]uridine incorporation was decreased only in those chondrocytes cultured on aluminum oxide, calcium phosphate, or zirconium oxide. Chondrocytes cultured on titanium had greater alkaline phosphatase‐specific activity than did cells cultured on plastic, but the incorporation of [3H]uridine and production of collagenase‐digestible protein, noncollagenase‐digestible protein, and percentage of collagen was comparable. The response of chrondrocytes from the growth zone and resting zone to culture surface was comparable, differing primarily in magnitude. Cell maturation‐dependent effects were evident when enzyme activity in trypsinized and scraped cells was compared. These results indicate that different surface materials affect chondrocyte metabolism and phenotypic expression in vitro and suggest that implant materials may modulate the phenotypic expression of cells in vivo.
Influence of exogenous growth factors on the expression of plasminogen activators and plasminogen activator inhibitors by cells isolated from normal and healing rabbit ligaments
Authors: Murphy Patricia G. , Hart David A.
Published: February 2005

In this investigation, we demonstrate that cells from normal and healing rabbit ligaments are selective in their responsiveness to various growth factors. The cells analyzed included fibroblasts isolated from the synovium, the anterior cruciate ligament, and the medial collateral ligament (midsubstance and epiligament). Fibroblasts isolated from scar tissue of medial collateral ligament that had been allowed to heal for 3 weeks also were analyzed. The addition of insulin‐like growth factor‐2 or transforming growth factor‐β1 was observed to alter, in a dose‐dependent manner, the expression of plasminogen activator and plasminogen activator inhibitor by connective tissue cells. However, the response to these growth factors was cell specific. Fibroblasts isolated from the midsubstance, epiligament, and scar tissue of the medial collateral ligament were responsive to these growth factors; fibroblasts isolated from the anterior cruciate ligament and synovium did not have a detectable response. The cells from the normal and healing medial collateral ligament responded to both growth factors by increasing plasminogen activator inhibitor activity. This was observed at both the protein and RNA level. In contrast, the addition of insulin‐like growth factor‐1 or acidic or basic fibroblast growth factor to cells derived from normal or healing ligament did not result in any detectable alteration of plasminogen activator or plasminogen activator inhibitor activity. These results are similar to those observed with an explant system and indicate that cells isolated from ligament tissue maintain their responsiveness to these growth factors in the absence of matrix. As the major effect of insulin‐like growth factor‐2 and transforming growth factor‐β1 on the cells tested was to increase plasminogen activator inhibitor activity, such an alteration should diminish the activity of plasminogen activator, an enzyme capable of directly and indirectly proteolyzing matrix molecules, and thus contribute to a more anabolic environment.
Effect of anterior cruciate ligament deficiency on economy of walking and jogging
Authors: McHugh Malachy P. , Spitz Amy L. , Lorei Matthew P. , Nicholas Stephen J. , Hershman Elliott B. , Gleim Gilbert W.
Published: February 2005

The metabolic cost of walking and jogging following injury to the anterior cruciate ligament is unknown. Economy of motion refers to the oxygen consumption for a submaximal work rate. The purpose of this study was to compare the economy of walking and jogging of an anterior cruciate ligament‐deficient population with that of a control population without orthopaedic abnormalities. Steady‐state oxygen consumption was measured in 30 patients and 98 controls while they were on a treadmill at various speeds. Deficiency of the anterior cruciate ligament was diagnosed arthroscopically. The patients also were tested for isokinetic knee extension‐flexion strength, hip flexion, and abduction and adduction strength and underwent arthrometic measurement of anterior tibial displacement. The patients had a statistically significant increase in oxygen consumption when jogging at 160.9 m/min (p = 0.007); however, there was no significant effect of anterior cruciate ligament deficiency on economy at the other speeds tested. The patients had significant deficits in strength of all muscle groups tested. Steady‐state oxygen consumption at 160.9 m/min tended to be inversely related to the deficit of strength of knee flexion (r = −0.44, p = 0.07). Arthrometric measurements and chronicity of injury were unrelated to steady‐state oxygen consumption. These data indicate that anterior cruciate ligament deficiency increases oxygen consumption during jogging. In long‐distance running, this decreased economy translates into significant additional caloric requirements, which may result in earlier fatigue.
An assay to measure adriamycin binding in osteosarcoma cells
Authors: Gebhardt Mark C. , Kusuzaki Katsuyuki , Mankin Henry J. , Springfield Dempsey S.
Published: February 2005

Adjuvant chemotherapy is currently employed in the treatment of patients with osteosarcoma, but the drug regiments, although effective in improving disease‐free survival, are unsuccessful in 20–40% of patients and very toxic. It would be useful to know whether tumor cells are sensitive to a given drug prior to its use. To this end, we developed a method of assessing Adriamycin (doxorubicin) binding to tumor nuclei as a possible means of detecting sensitivity to the drug. Adriamycin‐sensitive murine osteosarcoma cells were used to develop the assay. The in vitro conditions (drug concentration, duration of incubation, and temperature) were optimized with use of the murine osteosarcoma cells in culture. After the cells had been incubated with Adriamycin, cell viability was determined and Adriamycin fluorescence intensity was measured with a cytofluorometer. The optimal parameters for Adriamycin binding were found to be a 30‐minute incubation in a 10 μg/ml concentration of Adriamycin at 37°C the frequency of cells that emitted Adriamycin fluorescence from the nucleus compared with the total number of livin cells reached 100% under these conditions. In a murine leukemia cell line with known sensitivity to Adriamycin, the cells emitted red fluorescence from the nucleus and cytoplasm, whereas in a resistant line the cells emitted Adriamycin fluorescence from only the cytoplasm. We demonstrated that it is possible to differentiate nuclear from cytoplasmic concentration of Adriamycin in a tumor cell with use of a fluorescent microscope and that resistant cell lines can be distinguished from sensitive cell lines by this method. Since Adriamycin acts by intercalating to DNA, its absence in the nucleus probably indicates a resistant cell. This is a rapid technique that may allow prediction of drug sensitivity at the time of diagnosis or relapse.
Evaluation of muscle force prediction models of the lumbar trunk using surface electromyography
Authors: Hughes Richard E. , Chaffin Don B. , Lavender Steven A. , Andersson Gunnar B. J.
Published: February 2005

Optimization‐based models for prediction of muscle forces in the lumbar region of the torso are used to estimate the forces acting on spinal motion segments, especially for asymmetric tasks. The objectives of this study were to determine (a) which of four torso model formulations best predicted the electromyographic data, (b) the difference in muscular contribution to spinal compression force for the four models, and (c) the effect of using the lowest possible muscle stress bound in the model formulation. An approach for the investigation of competing optimization model formulations was developed and was illustrated with electromyographic data from static asymmetric loading conditions. This method is based on (a) the choice of experimental conditions in which models predict decidedly different muscle forces, and (b) the ability to ensure that the experimental conditions are such that the minimum number of assumptions about the force‐electromyogram relationship must be made in order to choose between competing model predictions. Of the four models analyzed, only the formulation with an objective function that was the sum of cubed muscle stresses predicted the electromyographic data acceptably. The muscular contribution to spinal compression force predicted by these models differed by as much as 160% for some experimental conditions. The use of the lowest possible muscle stress bound does not appear to predict muscle forces that are in agreement with electromyographic data.
Device for the application of a dynamic biaxially uniform and isotropic strain to a flexible cell culture membrane
Authors: Schaffer Jonathan L. , Rizen Michael , L'Italien Gilbert J. , Benbrahim Aziz , Megerman Joseph , Gerstenfeld Louis C. , Gray Martha L.
Published: February 2005

A large number of studies have demonstrated that mechanical perturbation modulates cellular metabolism; however, the systematic characterization of the molecular and cellular transduction mechanisms underlying mechanically induced metabolic modulation has been impeded, in part, by the limitations of the mechanical device. The objective of this investigation was to develop an in vitro experimental system that would provide independent control of the spatial and temporal biaxial strain distribution imposed on a flexible transparent tissue culture membrane that permits attachment, proliferation, and maintenance of the phenotypic expression of cultured embryonic osteoblasts. Such a device would permit a systematic investigation of the cellular response to specific, independently controlled parameters of mechanical deformation. Using a prototype device designed to impose a dynamic sinusoidal spatially isotropic biaxial strain profile, we confirmed experimentally that the strain was biaxially uniform and isotropic (radial = circumferential strain over the entire culture membrane) to within 14% (SD/mean) for the range of the peak strains tested (2.3–9.4%). Additionally, the uniformity was maintained at 1 Hz for at least 5 days of continuous operation. This experimental verfication of the theoretically predicted isotropic strain profile suggests that the design principle is sound. Embryonic osteoblasts cultured on the flexible substrate proliferated and exhibited a temporal pattern of phenotypic expression (extracellular matrix accumulation and mineralization) comparable with that observed on polystyrene of tissue culture grade.
Technique for producing controlled closed fractures in a rabbit model
Authors: Park Sang‐Hyun , Cassim Ahmed , Llinas Adolfo , McKellop Harry A. , Sarmiento Augusto
Published: February 2005

We describe a new technique to produce a closed fracture of the rabbit tibia with reproducible location and shape of the fracture. The hindlimb of a New Zealand White rabbit was enclosed in a bivalved cast, a 1.5 mm diameter hole was drilled through the lateral tibial cortex, and the tibia was fractured by loading in three‐point bending in an arbor press. The cast protected the soft tissues from being crushed while it concentrated the bending moment at the intended fracture site. The cortical hole functioned as a stress riser and fracture initiation site, such that the influence of the loading rate on the fracture characteristics was minimized. Transverse fractures or oblique fractures at any desired angle could be produced by variations of the position of the cortical drill hole relative to the central loading point. Thirty‐four tibial fractures (18 transverse and 16 oblique) were produced. The rabbits were killed immediately, and the fracture angle and the extent of tissue damage were evaluated radiographically, as well as macroscopically. This method produced a consistent location of the fracture, with 88% reproducibility of the fracture angle and only minor damage to the adjacent soft tissue.
Mechanical evaluation of six types of reconstruction following 25, 50, and 75% resection of the proximal femur
Authors: Kohles Sean S. , Markel Mark D. , Rock Michael G. , Chao Edmund Y. S. , Vanderby Ray
Published: February 2005

The structural stiffness and the stiffness of the osteotomy site after six types of reconstruction of the proximal femur were compared by testing in axial compression, mediolateral bending, and axial torsion in a canine model. An osteotomy was carried out for 25, 50, or 75% of the length of each femur, and the proximal portion was replaced by one of five allograft/endoprosthetic composites or a segmental replacement. The reconstructions included (a) a composite press‐fit proximally and cemented distally, (b) a composite cemented proximally and distally, (c) a composite cemented proximally and fixed with two plates at the allograft‐host bone interface, (d) a composite cemented proximally and secured distally with bicortical screws, (e) a composite secured proximally and distally with bicortical screws, and (f) a segmental prosthesis cemented into the distal femur. The results showed that the segmental reconstruction and the reconstruction with double‐plate fixation and a cemented endoprosthesis were structurally stiffer and had greater stiffness of the osteotomy site than the other reconstructions. In comparison, reconstructions that involved cement alone or cement and press‐fit techniques generally were more compliant than the others, both structurally and at the osteotomy site.