bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ calibration of miniature sensors implanted into the anterior cruciate ligament. Part II: Force probe measurements
Authors: Markolf Keith L. , Willems Matthew J. , Jackson Steven R. , Finerman Gerald A. M.
Published: February 2005

The arthroscopically implantable force probe transducer, which measures the effects of local ligament fiber tension, was inserted into the anteromedial band of the anterior cruciate ligament after measurements with the differential variable reluctance transducer were completed in Part I of this study. The overall goals in Part II remained the same, with additional experiments included to determine the sensitivity of output voltage from the transducer to medial‐lateral placement of the device within the anteromedial band and to depth of placement within a given insertion hole. Calibration curves of output voltage from the arthroscopically implantable force probe transducer versus resultant force in the ligament were generated during a separate series of knee‐loading experiments identical to those performed in Part I. The output voltage for a given probe placement was highly sensitive to the depth of implantation into the anteromedial band. When the probe was completely buried within the ligament, voltage outputs were often sporadic or absent even though surface fibers had clearly developed tension. When the probe was only partially inserted into the hole, such that the end of the probe was slightly proud to the surface, voltage output was significantly, higher as the device measured tension in the superficial fibers. Voltage outputs for proud placement were always significantly higher than corresponding voltages for deep placements for all test conditions. With proud placements, voltage outputs were not sensitive to small deviations in medial‐lateral position within the anteromedial band. Mean coefficients of variation for output voltage (four repeated placements of the probe into the same central hole) ranged from 0.156 to 0.359 (deep and proud insertions). Output voltage from the probe generally followed the pattern of resultant force in the ligament during passive knee extension. For anterior tibial loading, the contribution of deep fibers to resultant force did not depend on the knee flexion angle at which the test was conducted; the contribution of superficial fibers was greatest beyond 45° of flexion and least at full extension. The contributions of the anteromedial band to resultant force in the ligament were not significantly different between the three modes of loading (anterior tibial force, internal tibia torque, and varus moment) at either 0 or 10° of flexion; this was true for both superficial and deep fibers. We found it necessary to secure the probe within the insertion site using a suture (for both deep and proud placements) to obtain repeatable readings. Puncturing the anteromedial band clearly produced tissue damage; the insertion hole often produced a permanent plane of cleavage in the anteromedial band. However, this tissue damage did not alter the overall ability of the ligament to generate resultant force.
Histochemical and molecular analyses of distraction osteogenesis in a mouse model
Authors: Tay B. K‐B. , Le A. X. , Gould S. E. , Helms J. A.
Published: February 2005

A tibial lengthening scheme in the mouse was used to study the molecular and cellular events regulating tissue regeneration during distraction osteogenesis. Here, we report on the surgical technique and frame design and describe the histochemical and molecular aspects of distraction during different phases of treatment. A total of 26 mice were used in this study. The treatment protocol was divided into a latency period of 7 days, a phase of active distraction that lasted 10 days with a distraction rate of 0.42 mm/day, and a maturation phase of 9 days. During latency, the distraction site resembled a stabilized fracture callus bn both a histochemical and a molecular level. During active distraction, the gap was characterized by a central fibrous interzone bordered by primary matrix fronts, regenerate bone aligned with the distraction force, parallel columns of vascular sinusoids, and a medullary cavity. Alkaline phosphatase activity was detectedin the endosteal and periosteal surfaces of the bone ends. Tartrate resistant acid phosphatase staining revealed that osteoclasts remodeled the bone regenerate as it formed. Collagen type I was expressed in the periosteum and the primary matrix front during distraction, whereas collagen type‐II transcripts were localizedto discrete regions on the periosteal surfaces, immediately adjacent to the osteotomy ends. Collagen type‐II transcripts were not detected in the fibrous interzone. During the maturation phase, cells within the fibrous interzone expressed collagen type I and exhibited abundant alkaline phosphatase activity, suggesting that they had begun to terminally differentiate. Collectively, these data demonstrate the utility of a mouse model to study the molecular and cellular bases for the regeneration and remodeling of tissue.
Publication rate of abstracts presented at the annual meeting of the orthopaedic research society
Authors: Daluiski Aaron , Kuhns Craig A. , Jackson Kent R. , Lieberman Jay R.
Published: February 2005

Although the timely conveyance of information at national meetings like those of the Orthopaedic Research Society is critical to the dissemination of new scientific research, the ultimate goal of most researchers is to publish work in peer‐reviewed journals referenced in Medline. All of the abstracts that were presented at the podium at the 1991. 1992. and 1993 annual meetings of the Orthopaedic Research Society and printed in the appropriate yearly transactions were included in this study (n = 888, 296 per year). A detailed computerized Medline search of each author on the abstract and the appropriate keywords from the title was performed until a publication was found; otherwise, the abstract was excluded. The database was searched through June 30. 1997. A total of 463 (52%) of the abstracts were published by July 1, 1997. The percentages for each individual year were similar: 148 (50%) were published in 1991,162 (55%) in 1992, and 153 (52%) in 1993. Publication of the majority of these papers (93.1%, 431 of 463) occurred within 4 years of the respective meeting. The Journal of Orthopaedic Research published the majority of these papers (17.5%), followed by The Journal of Bone and Joint Surgery (American), the Journal of Biomechanics, Clinical Orthopaedics and Related Research, and Spine (each 5.2%). No significant differences in the rate of publication were observed between papers of 10 broad subject categories (p = 0.103). These results are similar to those from other basic science meetings and to the recently reported results for the annual meeting of the American Academy of Orthopaedic Surgeons.
Localization of tyrosine‐phosphorylated proteins in cultured mouse dorsal root ganglion neurons
Authors: Shirasu Mikihiro , Morihara Toru , Okajima Seiichiro , Tamai Kazuo , Mizoguchi Akira , Ide Chizuka , Hirasawa Yasusuke
Published: February 2005

The present study, using confocal laser scanning microscopy and immunoelectron microscopy, examined the intracellular localization of tyrosine‐phosphorylated proteins in cultured mouse dorsal root ganglion neurons with special reference to their growth cones. The growth cone is the specialized structure formed at the growing tip of the axon; characteristically highly motile with filopodia on the surface, it is responsible for the extension and guidance of the neurites to the appropriate targets during nerve regeneration. It has been suggested that protein‐tyrosine phosphorylation plays an important role in the intracellular signal transduction that regulates the extension and motility of growth cones. By fluorescence immunocyto‐chemistry, phosphotyrosine immunoreactivity was found in the growth cones and neurites. Some of the filopodia exhibited strong immunoreactivity at their tips. By immunoelectron microscopy, a large number of immunogold particles (gold particles conjugated to the secondary antibody) were seen to be distributed in the cytoplasm and some were observed on the plasma membrane in the growth cones, whereas in the neurites the density of immunogold particles was the same in the axoplasm as on the plasma membranes. These findings suggest that in the growth cones phosphotyrosines might mainly be involved in intracellular signaling for maintaining their high motility whereas in the neurites they might mostly be associated with the receptor proteins at the plasma membrane for adhesion as well as for growth of neurites. Thus, tyrosine phosphorylation might contribute to different functions for growth cones and neurites.
Interleukin‐10 inhibits cytokine synthesis in monocytes stimulated by titanium particles: Evidence of an anti‐inflammatory regulatory pathway
Authors: Pollice Paul F. , Hsu James , Hicks David G. , Bukata Susan , Rosier Randy N. , Reynolds Paul R. , Puzas J. Edward , O'Keefe Regis J.
Published: February 2005

The anti‐inflammatory mediator interleukin‐10 was investigated as a potential inhibitor of pro‐inflammatory cytokine release in human peripheral blood monocytes activated with titanium particles. It inhibited the secretion of both tumor necrosis factor‐alpha and interleukin‐6 in a dose‐dependent manner, with complete inhibition observed at 2 ng/ml. Co‐culture experiments were performed to determine whether this cytokine may have functional importance as an inhibitor of the inflammatory response. When unstimulated lymphocytes and monocytes were co‐cultured with titanium‐stimulated monocytes, they significantly suppressed the secretion of both interleukin‐6 and tumor necrosis factor‐alpha. The inhibitory effect of these co‐cultured cells could be partially blocked with the addition of an interleukin‐10 neutralizing antibody. Interleukin‐10 levels were measured in monocyte cultures treated with titanium particles as well as in fresh monocyte cultures treated with conditioned medium from titanium‐stimulated monocytes. The latter experiments demonstrated marked stimulation of interleukin‐10 secretion in conditioned medium‐treated cultures, an effect that was related to the presence of tumor necrosis factor‐alpha in the conditioned medium. The addition of titanium to conditioned medium‐treated cultures markedly reduced the secretion of interleukin‐10, suggesting that the most responsive cells are unstimulated monocytes exposed to agents released from activated monocytes. Altogether, the expression and responsiveness to interleukin‐10 suggest a potential role for anti‐inflammatory cytokines in regulation of the inflammatory response to wear debris.
Measurement of the charge properties of articular cartilage by an electrokinetic method
Authors: Minassian A. , O'Hare D. , Parker K. H. , Urban J. P. G. , Warensjo K. , Winlove C. P.
Published: February 2005

The charge structure of the surface of articular cartilage determines its interactions with the macromolecules and cells of synovial fluid. It may thereby be important to the physiological function and pathological degeneration of the tissue. To determine whether the electrokinetic properties of the surface differ from those of the bulk tissue, we measured the streaming potential generated by the flow of electrolyte over the surface of a cartilage plug mounted in a chamber built for that purpose. We then calculated the effective surface charge density. In nonfibrillated cartilage from the human femoral head, the surface charge density, 0.037 ± 0.004 Cm−2 (mean ± SD), was approximately half that measured at the surface of slices cut from the middle and deep zones. In addition, the surface charge density fell relatively little at low pH; this is consistent with a higher proportion of strongly acidic groups. The variations in surface charge density were found to be similar to those in total fixed charge density in the slices by the tracer cation method. Therefore, no evidence exists that the actual surface differs in composition from the immediately underlying matrix. The addition of synovial fluid (0.0025 ml/ml) to the superfusing solution reduced the surface charge density by 25 ± 9% (n = 5), and we attributed this to the binding of synovial‐fluid macromolecules.
Deformation of articular cartilage collagen structure under static and cyclic loading
Authors: Kääb Max J. , Ito Keita , Clark John M. , Nötzli Hubert P.
Published: February 2005

Relatively little is known about the morphology of articuar cartilage under conditions of normal use. yet a more profound knowledge is both critical to the understanding of cartilage function and helpful for the validation of tissue‐engineered cartilage. In this study, the deformation of the articular cartilage of the tibial plateau under compressive static and cyclic loading is characterized. Whole knee joints of rabbits were loaded ex vivo while the knee was held statically or allowed to move against resistance. Load magnitudes of quadriceps were maintained at either three (high) or one (low) times body weight for 30 minutes. For cyclic loading, the tibia was flexed between 70 and 150° relative to the femur at 1 Hz with either a cyclic or constant force. The recovery of cartilage after unloading was examined for each loading condition. At the end of the loading, specimens were cryofixed while under load, freeze‐substituted, and prepared for scanning electron microscopy. Morphological examination demonstrated significantly higher deformation of the collagen structure throughout all cartilage zones under static loading conditions compared with cyclic loading condition's in which deformation was limited to the superficial regions. The minimum thickness of the cartilage that remained after loading was dependent on the magnitude of load and was significantly smaller with static loads (54% of the thickness of the unloaded controls) than after cyclic loading or constant‐force cyclic loading (78 or 66% of the thickness of the unloaded controls, p < 0.05). Acute bending of the collagen fibers was observed under both loading conditions: in the superficial half of the articular cartilage after static loading and in the superficial quarter after cyclic loading. Complete recovery of all deformation occurred within 30 minutes but was significantly faster after cyclic loading. These data suggest that the structure of the collagen of articular cartilage exhibits a zone‐specific deformation that is dependent on the magnitude and type of load.
Foot asymmetry in healthy adults: Elliptic fourier analysis of standardized footprints
Authors: Sforza Chiarella , Michielon Giovanni , Fragnito Nicola , Ferrario Virgilio F.
Published: February 2005

The size and shape of paired structures differ in the left and right sides of the body, Shape characteristics should be analyzed separately from size to supply information about the normal variations of human organs, In the present study, the within‐subject normal symmetry of footprint shape and size was analyzed from a mathematical standpoint. On the standardized left and right footprints of 46 healthy adults (23 women and 23 men; 19–26 years old), the outline of each foot excluding the toes was identified and its shape was quantified independently from size by the elliptic Fourier analysis. The symmetry in shape was quantified on an intra‐subject basis by calculating a morphologic distance D between the mathematical reconstructions of the left and right footprints of each subject, Symmetry in size was assessed by the right‐to‐left area ratio and found to be very good for all subjects; it ranged from 0.948 to 1.049. The subjects were also grouped by sex, and mean values were calculated, Within‐subject symmetry in the footprint shape appeared high, with morphologic distances ranging between 8.94 and 2.66 in men and between 7.15 and 3.09 in women, No consistent associations between footprint symmetry and age, body height and weight, or shoe size were found, On average, women had more symmetric size‐standardized footprints than did men (women: mean 4.57, SD 1.14; men: mean 5.46. SD 1.7; p 0.05), Mean size‐independent shapes of male and female left and right footprints were also calculated, Together with the analysis of individual asymmetry, they could be used for the quantitative diagnosis of borderline patients.
Patellar tendon augmentation after removal of its central third limits joint tissue changes
Authors: Atkinson P. J. , Oyen‐Tiesma M. , Zukosky D. K. , DeCamp C. E. , Mackenzie C. D. , Haut R. C.
Published: February 2005

The central third of the patellar tendon is commonly used to reconstruct the injured anterior cruciate ligament. Some studies have noted changes in joint tissues following this procedure. It has been postulated that these changes may be associated with increased stress on the remaining tendon following harvest of the graft. In our study, the central third of the patellar tendon was excised in three groups of rabbits. The central tendon defects in two of the three groups were fitted with different augmentation devices to augment the host tendon during the healing process. All rabbits followed a daily treadmill exercise regimen for 12 weeks following the operation. Biomechanical testing of the tendon revealed that in nonaugmented tendons the cross‐sectional area and the length of the patellar tendon significantly increased 112 and 16%, respectively. There was histological evidence of host‐tendon remodeling throughout the cross section and extensive fibrosis in the infrapatellar fat pad. Augmentation of the tendon significantly reduced these changes, with the least change noted in the group with the greatest augmentation. The rabbits with augmentation devices retained tendon dimensions similar to those of the contralateral intact tendon, and tendon remodeling occurred only in the defect area. The rabbits with augmentation devices exhibited little to no fibrosis of the fat pad. Structural properties of augmented and nonaugmented tendons were similar despite the size differences, indicating higher tissue quality in the augmented tendons. This study suggested that complications of the knee joint (i.e., tendon proliferation and fat pad fibrosis) noted after anterior cruciate‐ligament reconstruction with the autogenous patellar tendon may be limited by the implantation of an augmentation device.
Elastic anisotropy and collagen orientation of osteonal bone are dependent on the mechanical strain distribution
Authors: Takano Yuichi , Turner Charles H. , Owan Ichiro , Martin R. Bruce , Lau Stanley T. , Forwood Mark R. , Burr David B.
Published: February 2005

There is evidence that the collagen microarchitecture of bone is influenced by mechanical stresses or strains. We hypothesized that peak functional strains correlate with the elastic anisotropy and collagen orientation of bone tissue and that the bone anisotropy might be changed by altering the strain patterns in canine radii for 12 months. We tested these hypotheses in studies using nine adult foxhounds. The baseline group (n=3) had three rosette strain gauges placed around the midshaft of the radius, and strain distributions were measured during walking. The osteotomy osteotomy group (n=3) had 2 cm of the ulna surgically removed, and the sham group (n=3) received a sham osteotomy. The osteotomy and sham groups were allowed free movement in cages with runs for 12 months, after which strain distributions were measured on the radii during walking. Bone‐tissue anisotropy and collagen architecture were measured in radii from which the in vivo longitudinal strain patterns had been measured. The collagen birefringence patterns were measured with use of a circularly polarized light technique, and the elastic anisotropy of the bone, mineral, and collagen matrix was evaluated with a novel acoustic microscopy technique. Peak longitudinal strains in the radius correlated with the normalized longitudinal structure index (a polarized light measure of collagen birefringence) and the tissue anisotropy ratio. The average anisotropy ratio was 1.28 ± 0.01 in the posterior (compressive) cortex and 1.43 ± 0.01 in the anterior (tensile) cortex (these values are significantly different at p < 0.0001). The ulnar osteotomy changed the strain pattern on the radius, causing increased tensile strains in the medial cortex by more than 5‐fold that were associated with a significant increase in the anisotropy ratio in the bone tissue. The longitudinal structure index was strongly correlated (r=0.62, p < 0.005) with the anisotropy ratio of demineralized bone but was not correlated with that of deproteinized bone; this indicates that it reflects collagen fibril orientation in the bone matrix. These results indicate that mechanical strains affect both collagen and mineral microarchitecture in bone tissue, i.e., tensile strains are associated with increased tissue anisotropy and compressive strains, with decreased anisotropy.
Bioreactor cultivation conditions modulate the composition and mechanical properties of tissue‐engineered cartilage
Authors: Vunjak‐Novakovic G. , Martin I. , Obradovic B. , Treppo S. , Grodzinsky A. J. , Langer R. , Freed L. E.
Published: February 2005

Cartilaginous constructs have been grown in vitro with use of isolated cells, biodegradable polymer scaffolds, and bioreactors. In the present work, the relationships between the composition and mechanical properties of engineered cartilage constructs were studied by culturing bovine calf articular chondrocytes on fibrous polyglycolic acid scaffolds (5 mm in diameter, 2‐mm thick, and 97% porous) in three different environments: static flasks, mixed flasks, and rotating vessels. After 6 weeks of cultivation, the composition, morphology, and mechanical function of the constructs in radially confined static and dynamic compression all depended on the conditions of in vitro cultivation. Static culture yielded small and fragile constructs, while turbulent flow in mixed flasks yielded constructs with fibrous outer capsules; both environments resulted in constructs with poor mechanical properties. The constructs that were cultured freely suspended in a dynamic laminar flow field in rotating vessels were the largest, contained continuous cartilage‐like extracellular matrices with the highest fractions of glycosaminoglycan and collagen, and had the best mechanical properties. The equilibrium modulus, hydraulic permeability, dynamic stiffness, and streaming potential correlated with the wet‐weight fractions of glycosaminoglycan, collagen, and water. These findings suggest that the hydrodynamic conditions in tissue‐culture bioreactors can modulate the composition, morphology, mechanical properties, and electromechanical function of engineered cartilage.
Biologic model of bone transport distraction osteogenesis and vascular response
Authors: DeCoster Thomas A. , Simpson A. H. R. W. , Wood Martin , Li Gang , Kenwright J.
Published: February 2005

We developed an experimental model in the rabbit of distraction osteogenesis through bone transport that closely corresponds to the clinical use of bone transport in humans. We also applied injection angiography to study the arterial response of a limb undergoing bone transport. This model includes a proximal osteotomy and bone transport to fill in a segmental tibial diaphyseal defect. Regenerate bone formed well in the gap that was created that trailed the transport segment, and slow healing at the docking site was observed, as seen in humans. The angiographic techniques clearly revealed, by radiography and anatomic dissection, the arterial response to bone transport. The results showed that the transport segment had an arterial supply after osteotomy and after transport. They also demonstrated an extensive increase in vessels in limbs that had undergone distraction osteogenesis, an observation made clinically in humans but not well demonstrated experimentally. Furthermore, angiography showed proximal stretching and distal kinking of the major artery of the leg. This model closely resembles distraction osteogenesis through bone transport in humans and definitively demonstrates that the transport segment can maintain blood supply and remain viable during the transport process. The results of this study provide a basis for further work on factors that enhance and interfere with successful bone transport in humans.
Intramedullary pressure and bone marrow fat extravasation in reamed and unreamed femoral nailing
Authors: Kröpfl Albert , Davies James , Berger Udo , Hertz Harald , Schlag Günther
Published: February 2005

This study was designed to investigate whether intramedullary pressure and embolization of bone marrow fat are different in unreamed compared with conventional reamed femoral nailing in vivo. In a baboon model, the femoral shaft was stabilized with interlocking nailing after a midshaft osteotomy. Intramedullary pressure was measured in the distal femoral shaft fragment at the supracondylar region. Extravasation of bone marrow fat was determined by the modified Gurd test (range: 0–5) with blood samples from the vena cava inferior. Data were monitored in eight unreamed and eight reamed intramedullary femoral nailing procedures. Intramedullary pressure increased in the unreamed group to 76 ± 25 mm Hg (10.1 ± 3.3 kPa) during insertion of 7‐mm nails and in the reamed group to 879 ± 44 mm Hg (117.2 ± 5.9 kPa) during reaming of the medullary cavity. Insertion of 9‐mm nails after the medullary cavity had been reamed to 10 mm produced an intramedullary pressure of 254 ± 94 mm Hg (33.9 ± 12.5 kPa) (p < 0.05). Fat extravasation in the unreamed group was recorded with a score of 2.9 ± 0.4 for the Gurd test during nailing with 7‐mm nails, whereas in the reamed group significantly more fat extravasation was noticed during the reaming procedures, with a score of 4.6 ± 0.1. Liberation of fat during insertion of 9‐mm nails after reaming was recorded with a score of 3.5 ± 0.4. In both groups, a positive correlation of fat extravasation with the rise in intramedullary pressure was found (reamed group: rs = 0.868: unreamed group: rs = 0.698), resulting in significantly less liberation of bone marrow fat in the unreamed stabilized group than in the reamed control group (p < 0.05). The data indicate that fat embolization during nailing procedures after femoral osteotomy increases with increasing intramedullary pressure and occurs in a lesser degree in unreamed than in reamed intramedullary femoral shaft stabilization.
Failure of partial cementation to achieve implant stability and bone ingrowth: A long‐term roentgen stereophotogrammetric study of tibial components
Authors: Ryd Leif , Hansson Ulrik , Blunn Gordon , Lindstrand Anders , Toksvig‐Larsen Sören
Published: February 2005

Thirty patients with gonarthrosis were operated on with the PCA primary total knee prosthesis and had the tibial component fixed to the bone by partial cementation. In the first two groups of patients, cementation was by a peripheral rim of high and low‐viscosity cement, respectively. In the third group, the pegs were cemented with the low‐viscosity cement. Follow‐up was performed with use of clinical parameters and roentgen stereophotogrammetric analysis. Clinically, the series was successful apart from a problem with tibial component wear, necessitating revision in five patients. At 8 years, the mean Hospital for Special Surgery score was 81 points. Venn‐diagram scores revealed four failures and three acceptable cases; the remaining cases were satisfactory. Apart from one loose patellar component, there was no mechanical loosening. Roentgen stereophotogrammetric analysis showed that the tibial components moved relative to the bone; this indicated fibrous tissue fixation. which was corroborated histologically in two patients. The objective, to achieve bone ingrowth, was thus not successfully met. Radiolucent lines were consistently seen, and their size correlated with the migration as measured by roentgen stereophotogrammetric analysis. Furthermore, five continuously migrating prostheses showed significantly larger radiolucent zones than the prostheses that migrated only initially, and they were less well bonded to the bone at 1 year. In conclusion, partial cementation does not appear to be a way to achieve bone ingrowth in porous‐coated implants under load.
Mechanical behavior of human trabecular bone after overloading
Authors: Keaveny Tony M. , Wachtel Edward F. , Kopperdahl David L.
Published: February 2005

With the etiology of osteoporotic fractures as motivation, the goal of this study was to characterize the mechanical behavior of human trabecular bone after overloading. Specifically, we quantified the reductions in modulus and strength and the development of residual deformations and determined the dependence of these parameters on the applied strain and apparent density. Forty cylindrical specimens of human L1 vertebral trabecular bone were destructively loaded in compression at 0.5% strain per second to strains of up to 3.0% and then immediately unloaded to zero stress and reloaded. (An ancillary experiment on more readily available bovine bone had been performed previously to develop this testing protocol.) In general, the reloading stress‐strain curve had a short initial nonlinear region with a tangent modulus similar to Young's modulus. This was followed by an approximately linear region spanning to 0.7% strain, with a reduced residual modulus. The reloading curve always approached the extrapolated envelope of the original loading curve. Percent modulus reduction (between Young's and residual), a quantitative measure of mechanical damage, ranged from 5.2 to 91.0% across the specimens. It increased with increasing plastic strain (r2 = 0.97) but was not related to modulus or apparent density. Percent strength reduction, in the range of 3.6–63.8%, increased with increasing plastic strain (r2 = 0.61) and decreasing apparent density (r2 = 0.23). The residual strains of up to 1.05% depended strongly on applied strain (r2 = 0.96). Statistical comparisons with previous data for bovine tibial bone lend substantial generality to these trends and provide an envelope of expected behavior for other sites. In addition to providing a basis for biomechanical analysis of the effects of damage in trabecular bone at the organ level, these findings support the concept that occasional overloads may increase the risk of fracture by substantially degrading the mechanical properties of the underlying trabecular bone.
Assessment of subchondral bone blood flow in the rabbit femoral condyle using the laser speckle method
Authors: Fukuoka Shinji , Hotokebuchi Takao , Terada Kazumasa , Kobara Nobuo , Fujii Hitoshi , Sugioka Yoichi , Iwamoto Yukihide
Published: February 2005

The laser speckle method is a new form of flowmetry that can obtain a two‐dimensional distribution of blood flow in tissue. This method is a noncontact, simple, and rapid technique that may aid in the diagnosis of osteonecrosis. We investigated whether the subchondral bone blood flow within the femoral condyles of rabbits could be measured by the laser speckle method. The hydrogen washout method was chosen as a comparison technique because of its ability to allow repetitive measurements of blood flow in various conditions in one rabbit and because of its realiability which already has been established. We simultaneously measured the bone blood flow in 20 femoral condyles of 10 rabbits with the laser speckle and hydrogen washout methods and found a significant correlation between the blood flow levels with use of these two methods. For the clinical application of the laser speckle method, we also investigated the influence of cartilage thickness on the measurements and the depth in the bone to which blood flow could be measured with this method. A cartilage thickness of 0.2 mm did not influence the measurement of the bone blood flow, and the depth in the bone to which the laser speckle method could be used was approximately 2 mm.
Mechanically induced calcium waves in articular chondrocytes are inhibited by gadolinium and amiloride
Authors: Guilak Farshid , Zell Richard A. , Erickson Geoffrey R. , Grande Daniel A. , Rubin Clinton T. , McLeod Kenneth J. , Donahue Henry J.
Published: February 2005

Chondrocytes in articular cartilage utilize mechanical signals from their environment to regulate their metabolic activity. However, the sequence of events involved in the transduction of mechanical signals to a biochemical signal is not fully understood. It has been proposed that an increase in the concentration of intracellular calcium ion ([Ca2+]i) is one of the earliest events in the process of cellular mechanical signal transduction. With use of fluorescent confocal microscopy, [Ca2+]i was monitored in isolated articular chondrocytes subjected to controlled deformation with the edge of a glass micropipette. Mechanical stimulation resulted in an immediate and transient increase in [Ca2+]i. The initiation of Ca2+ waves was abolished by removing Ca2+ from the extracellular media and was significantly inhibited by the presence of gadolinium ion (10 μM) or amiloride (1 mM), which have previously been reported to block mechanosensitive ion channels. Inhibitors of intracellular Ca2+ release (dantrolene and 8‐diethylaminooctyl 3,4,5‐trimethoxybenzoate hydrochloride) or cytoskeletal disrupting agents (cytochalasin D and colchicine) had no significant effect on the characteristics of the Ca2+ waves. These findings suggest that a possible mechanism of Ca2+ mobilization in this case is a self‐reinforcing influx of Ca2+ from the extracellular media, initiated by a Ca2+‐permeable mechanosensitive ion channel. Our results indicate that a transient increase in intracellular Ca2+ concentration may be one of the earliest events involved in the response of chondrocytes to mechanical stress and support the hypothesis that deformation‐induced Ca2+ waves are initiated through mechanosensitive ion channels.
Monitoring glycosaminoglycan replenishment in cartilage explants with gadolinium‐enhanced magnetic resonance imaging
Authors: Allen R. G. , Burstein D. , Gray M. L.
Published: February 2005

We previously devised a magnetic resonance imaging method that allows for the nondestructive and quantitative determination of glycosaminoglycan concentration in excised cartilage. The technique measures the concentration of the charged contrast agent Gd‐DTPA2− (gadolinium diethylenetriaminepentaacetic acid) equilibrated within cartilage, from which the tissue distribution of glycosaminoglycan can be calculated. The goals of our study were to determine the practicality of nondestructively monitoring glycosaminoglycan concentration in cartilage explants over a long‐term culture period and to determine if glycosaminoglycan could be restored to glycosaminoglycan‐depleted cartilage explants maintained in long‐term culture. To meet our objectives, we harvested bovine cartilage explants, treated them initially with trypsin to reduce the glycosaminoglycan concentration, and cultured them for as long as 8 weeks. Images depicting glycosaminoglycan concentration were calculated from magnetic resonance images acquired at selected intervals during the trypsinization process and the subsequent culture period. The results indicate that gadolinium‐enhanced magnetic resonance imaging can follow the reduction of glycosaminoglycan concentration over the course of enzymatic digestion and the replenishment of glycosaminoglycan over several weeks of culture and that cultured cartilage explants are capable of restoring glycosaminoglycan to 85% of its initial concentration. Of particular interest, samples cultured for 5 weeks indicated a depth dependence of glycosaminoglycan regeneration to values similar to the initial physiologic distribution. Thus, this magnetic resonance imaging method may be a very powerful means for exploring the spatial and temporal evolution of glycosaminoglycan in cartilage.
Coordinate upregulation of cartilage matrix synthesis in fibrin cultures supplemented with exogenous insulin‐like growth factor‐I
Authors: Fortier Lisa A. , Lust George , Mohammed Hussni O. , Nixon Alan J.
Published: February 2005

The addition of insulin‐like growth factor‐I to cartilage cultures is known to stimulate the synthesis of proteoglycan and type‐II collagen in explant and monolayer studies. The purpose of this study was to determine the effects of long‐term supplementation with insulin‐like growth factor‐I in chondrocytes cultured in fibrin discs as a preliminary investigation toin vivoapplication of chondrocyte/insulin‐like growth factor‐I/fibrin grafts to articular‐cartilage repair procedures. Chondrocyte‐fibrin cultures were maintained for 14 days, with insulin‐like growth factor‐I added at varying concentrations of 0, 10, 50, or 100 ng/ml medium. Cultures supplemented with 50 or 100 ng of growth factor/ml had increased levels of aggrecan and type‐IIB procollagen mRNA, and translation to aggrecan and type‐IIB collagen was confirmed by dye‐binding assay of total proteoglycan, type‐II collagen immunohistochemistry, and determination of collagen content by highperformance liquid chromatography. Maintenance of the chondrocyte phenotype during the 14 days of culture was confirmed by round cell morphology on routine staining, expression of type‐II procollagen mRNA onin situhybridization, evidence of production of pericellular type‐II collagen on immunocytochemistry, synthesis of large‐molecular‐size aggrecan monomer on CL‐2B column chromatography, and lack of appreciable message expression for type I or IIA collagen on Northern blot hybridization. Dose‐response effects of insulin‐like growth factor‐I on the expression of chondrocyte matrix constituents were most pronounced at 50 and 100 ng of growth factor per milliliter of medium. These data confirm that (a) culture of chondrocytes for extended periods in three‐dimensional cultures of fibrin maintains the chondrocyte phenotype and (b) supplementation with increasing concentrations of insulin‐like growth factor‐I enhances chondrocyte matrix synthesis and may provide a means to enhance chondrocyte phenotypic stability and function during transplantation grafting procedures.
Reduced bone stress as predicted by composite beam theory correlates with cortical bone loss following cemented total hip arthroplasty
Authors: Silva Matthew J. , Reed Karen L. , Robertson Douglas D. , Bragdon Charles , Harris William H. , Maloney William J.
Published: February 2005

Clinical and experimental evidence suggest that periprosthetic bone loss following total hip arthroplasty is caused in part by stress‐shielding. Changes in bone stress in the proximal femur following implantation can be estimated with use of composite beam theory. We hypothesized that the degree of stress‐shielding predicted by beam theory correlates with the magnitude of bone loss following cemented total hip arthroplasty. We analyzed cross sections from the proximal femur of 13 patients who had undergone unilateral cemented total hip arthroplasty. A matching implant was inserted contralaterally, and the cross‐sectional properties of the implant and bone and the bone density were determined. Bone loss was calculated on the basis of differences between contralateral (control) and ipsilateral (remodeled) sections and correlated to several beam‐theory parameters calculated from the control sections: implant rigidity, bone rigidity, ratio of implant to bone rigidity, and predicted decrease in bone stress. All parameters except implant rigidity were significantly correlated with bone loss (p < 0.05). Parameters that included implant and bone properties were more strongly correlated with bone loss than were those based on bone properties alone. The predicted decrease in bone stress explained 50‐60% of the variance in bone loss. The data also indicated that patients were not likely to lose substantial amounts of bone unless the reduction in bone stress exceeded a threshold value. Although limited by a small and heterogeneous sample, these results indicate that beam‐theory predictions correlate with the degree of femoral resorption and should be investigated further as a means to identify patients at high risk for bone loss.
Substance P and calcitonin gene‐related peptide expression at the extensor carpi radialis brevis muscle origin: Implications for the etiology of tennis elbow
Authors: Ljung Björn‐Ove , Forsgren Sture , Fridén Jan
Published: February 2005

With use of immunohistochemistry and antibodies to substance P and calcitonin gene‐related peptide, nerve fibers showing substance P‐like and calcitonin gene‐related peptide‐like immunoreactivity were demonstrated at the origin of the extensor carpi radialis brevis muscle in patients with tennis elbow (n = 6) and in healthy controls (n = 6). The nerve fibers were distributed in association with a subpopulation of small blood vessels and in nerve bundles but were not distributed in the tunica media‐adventitia junction of the arterioles. There were no inflammatory‐cell infiltrates and few solitary mast cells. The present study gives further evidence to previous suggestions that tennis elbow is not an inflammatory process in the sense of involving inflammatory cells. Frequent mechanical involvement affects sensory innervation, and substance P and calcitonin gene‐related peptide may have various important efferent effects, including microvascular leakage and local edema formation; therefore, the observations from this study constitute a morphological substrate for possible effects of substance P and calcitonin gene‐related peptide at the origin of the extensor carpi radialis brevis muscle.
Uniaxial yield strains for bovine trabecular bone are isotropic and asymmetric
Authors: Chang Wesley C. W. , Christensen Tennille M. , Pinilla Tania P. , Keaveny Tony M.
Published: February 2005

Although evidence suggests that yield strains for trabecular bone are isotropic, i.e., independent of loading direction, decisive support for this hypothesis has remained elusive. To explicitly test whether yield strains for trabecular bone are isotropic, compressive and tensile yield strains of 51 specimens of bovine tibial trabecular bone (0.41 ± 0.08 g/cm3 [mean apparent density ± SD]) were measured without end artifacts in on‐axis (along the principal trabecular orientation) and off‐axis (30–40° oblique to on‐axis) orientations. Yield strains for the on‐axis and off‐axis orientations were similar in tension (0.80 ± 0.03% compared with 0.85 ± 0.04%, p = 0.21) and compression (0.97 ± 0.05% compared with 0.96 ± 0.07%, p > 0.99); as expected, modulus and strength depended on loading direction. When considered with an ancillary experiment on bovine tibial trabecular bone that showed yield strains to be similar between on‐axis and 90° off‐axis bone, these results firmly establish the isotropy of uniaxial yield strains for bovine tibial trabecular bone. This bone is of high density and has a strong, plate‐type, anisotropic architecture. Therefore, yield strains for uniaxial loading are expected to be isotropic, or nearly so, for other types of dense trabecular bone, although further work is required to confirm this and to establish this behavior for bone of lower density.
New segmental long bone defect model in sheep: Quantitative analysis of healing with dual energy X‐ray absorptiometry
Authors: den Boer Frank C. , Patka Peter , Bakker Fred C. , Wippermann Burkhard W. , van Lingen Arthur , Vink Ger Q. M. , Boshuizen Klaas , Haarman Henk J. Th. M.
Published: February 2005

An appropriate animal model is required for the study of treatments that enhance bone healing. A new segmental long bone defect model was developed for this purpose, and dual energy x‐ray absorptiometry was used to quantify healing of this bone defect. In 15 sheep, a 3‐cm segmental defect was created in the left tibia and fixed with an interlocking intramedullary nail. In seven animals, the defect was left empty for the assessment of the spontaneous healing response. In eight animals serving as a positive control, autologous bone grafting was performed. After 12 weeks, healing was evaluated with radiographs, a torsional test to failure, and dual energy x‐ray absorptiometry. The mechanical test results were used for the assessment of unions and nonunions. Radiographic determination of nonunion was not reliably accomplished in this model. By means of dual energy x‐ray absorptiometry, bone mineral density and content were measured in the middle of the defect. Bone mineral density was 91 ± 7% (mean ± SEM) and 72 ± 6% that of the contralateral intact tibia in, respectively, the autologous bone‐grafting and empty defect groups (p = 0.04). For bone mineral content, the values were, respectively, 117 ± 18 and 82 ± 9% (p = 0.07). Torsional strength and stiffness were also higher, although not significantly, in the group with autologous bone grafting than in that with the empty defect. Bone mineral density and content were closely related to the torsional properties (r2 ranged from 0.76 to 0.85, p ⩽ 0.0001). Because interlocking intramedullary nailing is a very common fixation method in patients, the newly developed segmental defect model has clinical relevance. The interlocking intramedullary nail provided adequate stability without implant failure. This model may be useful for the study of treatments that affect bone healing, and dual energy x‐ray absorptiometry may be somewhat helpful in the analysis of healing of this bone defect.
Macrophage colony‐stimulating factor and interleukin‐6 release by periprosthetic cells stimulates osteoclast formation and bone resorption
Authors: Neale Susan D. , Sabokbar Afsaneh , Howie Donald W. , Murray David W. , Athanasou Nicholas A.
Published: February 2005

Periprosthetic bone loss is an important contributory factor for aseptic loosening of total joint replacements. It has recently been shown that osteoclast precursor cells are present in the wear particle‐associated macrophage infiltrate found in the membrane surrounding loose implants and that these cells are capable of differentiating into osteoclastic bone‐resorbing cells. Long‐term co‐culture of arthroplasty‐derived macrophages and the rat osteoblast‐like cell line, UMR‐106, in the presence of 1,25 (OH)2D3 results in the formation of numerous multinucleated cells that are positive for tartrate‐resistant acid phosphatase and vitronectin receptor and capable of extensive lacunar bone resorption. The aim of this study was to determine the effect of cytokines/growth factors, known to be present in the arthroplasty membrane, on this process of osteoclast differentiation. During osteoclast formation, increased levels of macrophage colony‐stimulating factor, interleukin‐6, and to a lesser extent, interleukin‐1β, but not tumour necrosis factor α, were detected in the co‐culture supernatants. Addition of neutralising antibodies to human interleukin‐1β or tumour necrosis factor α to the co‐culture system did not inhibit osteoclast formation. In contrast, co‐cultures to which neutralising antibodies to human macrophage colony‐stimulating factor or interleukin‐6 were added contained fewer cells positive for tartrate‐resistant acid phosphatase and vitronectin receptor and formed significantly fewer resorption pits. Time‐course studies showed that macrophage colony‐stimulating factor and interleukin‐6 increase osteoclast formation mainly in the early stages of osteoclast differentiation. These results indicate that the release of macrophage colony‐stimulating factor and interleukin‐6 by activated cells in the arthroplasty membrane is likely to contribute to pathological bone resorption associated with aseptic loosening by stimulating differentiation of mononuclear phagocyte osteoclast precursors into mature bone‐resorbing cells.