bluuebunny/crossref_metadata_2025 huggingface dataset:
Are leg electromyogram profiles symmetrical?
Authors: Pierotti Stephen E. , Brand Richard A. , Gabel Ronald H. , Pedersen Douglas R. , Clarke William R.
Published: February 2005

Electromyographic (EMG) patterns reflect function of the neuromuscular system. Abnormality of a given pattern may be established by comparison with that of the contralateral (presumably normal) limb if one ensures a difference beyond normal degrees of symmetry. We studied EMG patterns in six homologous knee muscles during freely selected, slow, and fast gaits in normal subjects. EMG signals were electronically conditioned to produce linear envelopes; envelopes from at least eight cycles from each subject at each speed were ensemble averaged. Grand ensemble averages for each muscle and speed were assembled from all subjects for right and left muscles. Transformed correlation coefficients (r′) and variance ratios established the degree of similarity. All muscles exhibited a fair degree of symmetry (mean r′ = 0.797 − 0.953), but we saw exceptions. On rare occasion, muscles repeatedly exhibited monophasic signals on one side and biphasic on the other. With increasing speed, signals generally became more repeatable, but we occasionally saw monophasic patterns becoming biphasic or vice versa. Considerable caution is essential before presuming any given pattern is abnormal. To ensure that a given pattern is abnormal one could establish that the pattern lies outside some statistical limits for normal population pattern controlled for speed and outside statistical limits for normal symmetry. Alternatively, one could determine the level of statistical differences in EMG patterns associated with distinct differences in level of functional performance between normal subjects and patients.
Measurement reproducibility of two commercial knee test devices
Authors: Torzilli Peter A. , Panariello Robert A. , Forbes Andrew , Santner Thomas J. , Warren Russell F.
Published: February 2005

Objective evaluation of patients' knee motion using mechanical devices, whether for diagnostic purposes or for assessing rehabilitative procedures, requires that these devices be reproducible, in order to avoid errors independent of the patients' condition. This study prospectively evaluates the reproducibility of two commercial knee test systems, the KT 1000 Knee Ligament Arthrometer and the Genucom Knee Analysis System, by performing repeated measurements on twenty normal men. Average knee motion, between‐subject variance, and within‐subject variance were determined by performing repeat tests on the same day and one week later. No significant difference was found between measurements taken on the two different test days, but the within‐subject variation was high. We found that larger applied forces or moments resulted in a larger variation in mean displacements. However, the percent variation about the mean (coefficient of variation) decreased with increasing applied loads. The coefficient of variation for the KT 1000 varied from 8 to 33% and for the Genucom, from 13 to 87%. On an individual basis, large variations were found in repeated measures for both devices. To minimize errors, we recommend that repeated tests be performed, higher forces and moments utilized, and specific flexion angles be used for each device and test. Even under these conditions, caution must be exercised when evaluating individual subjects.
An evaluation of three loading configurations for the in vitro testing of femoral strains in total hip arthroplasty
Authors: Finlay J. Bryan , Chess David G. , Hardie W. Robert , Rorabeck Cecil H. , Bourne Robert B.
Published: February 2005

Despite recent advances in total hip arthroplasty, proximal femoral resorption and osteopenia remain problems. To analyze the proximal strain effects of three different loading conditions, strains produced in intact and postarthroplasty femora have been compared. Ten adult cadaveric femora of similar size, shape, and rigidity were tested. Ten strain‐gauge rosettes were positioned on each femur. To simulate the “single leg support” phase of gait, fixtures were developed to load the femora under three different configurations: the VS (vertical shaft) configuration, with a vertically orientated femur having rotational freedom proximally and distally; the ITB (iliotibial band) configuration of a femur with rotational freedom positioned 11° from the vertical, with a strain‐gauge adjustable metallic simulation of the lateral muscles of the thigh; and the ABD (abductor) configuration of a femur with rotational freedom positioned 11° from the vertical, with a strain‐gauge adjustable metallic simulation of the abductor muscles. Each femur was loaded ⩽600 N through the medial point, located at one sixth of the transcondylar distance. Strain patterns and magnitudes produced by the three loading configurations were quite different in both the intact and postarthroplasty femora. Both the ITB and the ABD configurations resulted in greater proximal medial compression and lateral tension than did the VS configuration. The magnitudes of the proximal strains were significantly greater in the ABD configuration (p < 0.05). Postarthroplasty femora showed similar proximal results. It is proposed that meaningful strain data for the physiologically loaded femur can be obtained only with simulations that include the forces produced by the iliotibial band. To overcome the indeterminate nature and biological variation in these forces, the studies have to consider a range of forces.
The biologic effects of implant materials
Authors: Galante Jorge O. , Lemons Jack , Spector Myron , Wilson Philip D. , Wright Timothy M.
Published: February 2005

The interaction between implant materials and the surrounding biological environment continues to be an area of intense research and clinical interest. This article presents the information presented in a symposium, held during the 36th Annual Meeting of the Orthopaedic Research Society, in which several important issues concerning the biologic effects of implant materials were discussed. These issues included the mechanisms by which implant materials are released to the surrounding tissues and the ways in which these tissues respond to implant materials. The problem of bone loss around cementless implants was discussed as a specific example of a biologic effect resulting in both bone remodelling and endosteal erosion.
The effects of ischemia on long bone vascular resistance
Authors: Davis Timothy R. C. , Wood Michael B.
Published: February 2005

An in vitro canine tibia model was used to assess the effects of 48 h of hypothermic (4°C) ischemia on bone vascular resistance and on responsiveness of intraosseous blood vessels to circulating norepinephrine. Three groups of bones were studied: Group I (n = 11), 48 h hypothermic ischemia; Group II (n = 11), 48 h hypothermic ischemia with pretreatment with allopurinol and oxypurinol; and Group III (n = 10), no ischemia. Resting vascular resistance in both ischemic groups (79 and 74 mmHg/ml/min) was significantly higher (p < 0.0001) than in the nonischemic group (22 mmHg/ml/min). Effects of norepinephrine on vascular resistance were significantly greater in both ischemic groups (p < 0.004). In all three groups, acetylcholine infusion attenuated the increases in perfusion pressure caused by norepinephrine. This demonstrates secretion of endothelial‐mediated relaxing factors (EDRF) and prostaglandin for up to 48 h of hypothermic ischemia. As no significant differences were detected between the two ischemic groups, this study failed to demonstrate any protective effect of xanthine oxidase inhibitors.
Response of cortical bone to local controlled release of sodium fluoride: The effect of implant insertion site
Authors: Anderson Paul A. , Copenhaver James C. , Tencer Allan F. , Clark John M.
Published: February 2005

In a previous experiment, sodium fluoride in a biodegradable polymer matrix was introduced into the femoral canal of the rabbit and bone formation was compared with contralateral controls. We noted significant bone formation, but only in the distal third of the periosteal surface of the femur. This experiment was performed to distinguish fluoride‐induced periosteal bone formation from that due to the reactive osteogenic changes associated with local injury caused by the process of implantation. A proximal approach on the right leg and a distal approach on the left were used for the insertion of the implants in rabbits. Femurs were removed after 30 days and tested for stiffness and load to failure. The cross‐sectional area of mineralized bone was determined at proximal, midshaft, and distal locations. Fluorescent bone tissue growth labels were injected at weekly intervals to measure the rate of new periosteal bone formation. The results were compared with a control group that received sham implants. Results showed no difference between measured properties in right and left femurs in the control group or in those exposed to fluoride. A significant increase was found in the fluoride group in load to failure, along with cross‐sectional area of mineralized bone, and periosteal growth rates compared with the control group, but no difference was seen in stiffness. No difference was detected between the response proximally and distally in the fluoride group regardless of the location of insertion. There were no detectable changes in serum fluoride level after implantation of the poly L‐lactic acid/sodium fluoride matrix. These results show that fluoride exerts its osteogenic effects equally at proximal, midshaft, and distal regions of diaphyseal bone and is uninfluenced by the site of local injury due to insertion of the implant.
Computational methods for analyzing the structure of cancellous bone in planar sections
Authors: Kuo Arthur D. , Carter Dennis R.
Published: February 2005

Conventional stereologic methods for expressing the orientation of anisotropic materials are limited to materials assumed to possess orthogonal directions of orientation. In many substances, including cancellous bone, this assumption is unsubstantiated. Presented here are two simple methods for characterizing the orientation of any anisotropic material within a plane. By modeling the substance as a series of lines oriented in particular directions, it is possible to arrive at either a “phase distribution” that expresses the degree of orientation distributed over a range of angles or a series of “primary orientations” that express the degree of orientation at a select number of angles, with an additional measure of the degree of isotropy. This characterization of anisotropy is highly dependent on such parameters as feature size, sample size, test line spacing, and test line width. Given the careful selection of these parameters, the new methods provide simple measures of orientation, which may prove useful in testing Wolff's trajectorial theory of the relationship between mechanical stresses and the orientation of cancellous bone.
The reliability of the mankin score for osteoarthritis
Authors: van der Sluijs J. A. , Geesink R. G. T. , van der Linden A. J. , Bulstra S. K. , Kuyer R. , Drukker J.
Published: February 2005

For the histopathological classification of the severity of osteoarthritic lesions of cartilage, the Mankin score is frequently used. A necessary constraint on the validity of this scoring system is the consistency with which cartilage lesions are classified. The intra‐ and interobserver agreement of the Mankin score was determined. The intra‐ and interobserver agreement of the 14‐point Mankin score was adequate. Between observers 95% of differences were less than ∼7 points. By a more strict definition of the elements of the Mankin score, the intraobserver differences were reduced only for some observers. The interobserver differences were only slightly reduced: between observers 95% of differences were less than ∼6 points. We found the Mankin score to be an adequate histopathological tool.
Rabbit knee immobilization: Bone remodeling precedes cartilage degradation
Authors: Lane Smith R. , Thomas K. D. , Schurman D. J. , Carter D. R. , Wong M. , van der Meulen M. C.
Published: February 2005

This study analyzed processes underlying osteoporosis and osteoarthrosis after short‐term immobilization of the right hind limb of postadolescent (2.8 kg) and mature (4.0 kg) rabbits. After 3 weeks, the lateral posterior aspect of the lateral tibial plateau and the lateral femoral condyle of the immobilized limb exhibited prominent subchondral vascular eruptions. Femoral metaphyseal bone density decreased 27 and 18% in the immobilized limbs of postadolescent and mature rabbits, respectively. Calcein green fluorescence increased 1.9‐fold (p < 0.001) in the metaphyseal trabeculae of immobilized femurs. With immobilization, sulfate incorporation into femoral cartilage glycosaminoglycan increased, although total cartilage glycosaminoglycan and hydroxyproline levels were unchanged. Thymidine incorporation into DNA increased four‐ to fivefold in tibial and femoral cartilage of the immobilized limb. In this study, bone loss and remodeling preceded erosive cartilage degradation.
A finite element study of the initiation of failure of fixation in cemented femoral total hip components
Authors: Harrigan T. P. , Kareh J. A. , O'Connor D. O. , Burke D. W. , Harris W. H.
Published: February 2005

In order to study initial mechanisms of failure in cemented femoral total hip components, an anatomically accurate three‐dimensional linear finite element model was constructed and verified against experimental strain measurements in the cement mantle. Good agreement was found between predicted and measured strains. The likelihood of failure initiation due to cement‐prosthesis debonding and crack initiation at voids was studied for loading conditions simulating both one‐legged stance and stair climbing. The “out of plane” forces involved in stair climbing appear to be the greatest threat to the fixation of total hip replacements. In stair climbing, cement‐prosthesis debonding and pore crack initiation were probable in the proximal anteromedial region of the cement mantle, and near the distal tip of the implant. The proximal stresses in stair climbing were higher than the distal stresses in either stair climbing or one‐legged stance.
Biochemically discrete zones of canine flexor tendon: Evaluation of properties with a new photographic method
Authors: Amadio Peter C. , Berglund Lawrence J. , An Kai‐Nan
Published: February 2005

We describe a photographic method that we have found useful for studying small strain fields within a larger zone of interest. We have used this method to document differences in material properties which correlate with zones of different biochemical makeup in the canine flexor digitorum profundus tendon. This method may be useful in analysis of experimental injury and wound healing in this model and may have application in evaluating material properties of soft tissue in other models as well.
The effects of pulsed electromagnetic fields on blood vessel growth in the rabbit ear chamber
Authors: Greenough C. G.
Published: February 2005

A double‐blind, controlled trial of the effects of pulsed electromagnetic field on capillary growth in the rabbit ear chamber in adult New Zealand white rabbits has been performed. Three waveforms have been investigated. The first, a pulse burst waveform, produced a significant increase in the rate of growth of the vascular tissue within the chamber, but had no effect on macroscopic tissue maturation. The second and third, two different single pulse waveforms, had, in contrast, no significant effect on the rate of vascular growth and only an effect on vessel characteristics, with increased maturation of vessels using the second waveform. It is concluded that some of the observed effects of pulsed electromagnetic fields on tissue healing may be mediated through a primary effect on vascular growth.
The achilles functional index
Authors: Murrell George A. C. , Lilly Edward G. , Davies Helen , Best Thomas M. , Goldner Richard D. , Seaber Anthony V.
Published: February 2005

The literature regarding the management of spontaneous rupture of the Achilles tendon is controversial and confusing. The relative infrequency of the condition in any one center prohibits the completion of well‐designed clinical studies. Many of the disputes could be addressed and innovations tested if an appropriate animal model were available. We present a method for evaluating Achilles tendon function from measurements of the prints, preserved in bromphenol‐blue‐impregnated photocopying paper, of the hindfeet of walking rats. The stimulus for this study was derived from de Medinaceli's method for assessing the functional condition of rat sciatic nerves (de Medinaceli L, Freed WJ, Wyatt RJ: An index of the functional condition of rat sciatic nerve based on measurements made from walking tracks. Exp Neurol 77:634–643, 1982). Four variables were measured from these walking tracks, and comparsions between the damaged (experimental) and intact (normal) side were converted to proportional deficits. The relative contribution of each parameter to the overall deficit was determined by multiple linear regression analysis, and the variables were weighted accordingly to obtain an “Achilles Functional Index” (AFI). A sham operation produced no functional deficit, whereas animals subjected to a 0.5‐cm midsubstance Achilles tendon defect demonstrated a markedly impaired AFI. Animals with repaired transected Achilles tendons also demonstrated a significant, but less severly impaired AFI. The functional deficit in this repair group returned to control values by postoperative day 15, whereas animals with a defect remained impaired at day 15. Furthermore, an excellent correlation was found between the functional recovery and biomechanical properties (ultimate failure load) of the healing tendon (r = 0.94; p < 0.001). In summary, this method provides a relatively inexpensive, sensitive, and reproducible means of assessing the functional performance of the Achilles tendon after injury in the rat.
Microstructurally based model analysis of γ‐irradiated tendon allografts
Authors: Belkoff S. M. , Haut R. C.
Published: February 2005

A mathematical model of the collagenous microstructure of tendon was used to analyze the mechanical responses of γ‐irradiated patellar tendon allografts and nonirradiated controls. The model was fit to tensile test response curves from 10 pairs of allografts. Donors ranged in age from 16–64 years (six males, four females). The model indicated a decrease in elastic modulus of irradiated tendon collagen. It also suggested a significant increase in the degree and range of collagen fiber crimping following γ irradiation. The model results agree with the literature and histological observations. The model fit the experimental response curves well and provided a structurally based, objective method of quantitatively studying the mechanical response of tendons and the consequences of irradiation sterilization.
Primary and coupled motions in the intact and the ACL‐deficient knee: An in vitro study in the goat model
Authors: Oster David M. , Grood Edward S. , Feder Seth M. , Butler David L. , Levy Martin S.
Published: February 2005

Quadrupeds are commonly used as animal models to study healing of anterior cruciate ligament (ACL) reconstructions. While rabbits, dogs, goats, and sheep have been used, goats and sheep are increasingly being employed because of the larger joint size that facilitates surgery, ease of availability, and lower expense to maintain in the farm environment. In spite of this, little is known about the function of the ACL in controlling primary and coupled motions in the quadruped. We report here on the measurements of these motions in goats, with the application of anterior‐posterior forces, varus‐valgus moments, and internal‐external moments in the intact and ACL‐deficient knee. Sectioning the ACL caused significant increases in primary anterior translation, and in varus‐valgus and internal rotations. The increases in anterior translation were similar in amount and dependence on flexion angle to those seen in human knees. The increase in varus averaged 7° and did not depend on flexion angle, whereas the increase in valgus was significant only in the flexed knee. The increases in internal tibial rotation were greatest in extension, whereas the increases in external rotation were small and independent of flexion angle. When the ACL was cut, coupled internal rotation increased with an anterior force as well as a valgus moment. Large increases were seen in coupled anterior translation with the application of varus and valgus moments, whereas smaller increases were seen with internal and external moments. These findings demonstrate that the ACL restrains multiple motions in the goat knee. This study also provides baseline data for future studies of ACL reconstruction.
Healing of the medial collateral ligament following a triad injury: A biomechanical and histological study of the knee in rabbits
Authors: Anderson D. Ron , Weiss Jeffrey A. , Takai Shinro , Ohland Karen J. , Woo Savio L‐Y.
Published: February 2005

The effect of a partial medial meniscectomy and anterior cruciate ligament (ACL) transection on medial collateral ligament (MCL) healing was studied in skeletally mature rabbits. Two groups of animals, group I (isolated MCL rupture) and group II (MCL rupture with ACL transection and partial medial meniscectomy), were examined. At 6 and 12 weeks postoperatively, histological examination of the healing MCL and biomechanical evaluation of the varus‐valgus (V–V) knee rotation and tensile properties of the femur‐MCL‐tibia complex (FMTC) were performed. Group II animals experienced substantial joint degeneration by 6 weeks. Progressive osteophyte formation was observed adjacent to the MCL insertions along with proximal migration of the MCL tibial insertion between 6 and 12 weeks. Histologic examination of the healing MCL substance from both groups showed disorganized collagen, inflammation, and fibroblast proliferation that decreased over time. For group II knees, the V–V knee rotation was found to be significantly elevated (4.7 to 5.2 times the contralateral control), and did not decrease with time. In contrast, the V–V knee rotations of the group I specimens were 1.8 times greater than control immediately following injury, and approached control values by 12 weeks. Tensile testing of the FMTCs revealed that the ultimate load increased with time for both groups, but group I had significantly higher values than group II. The linear stiffness in group I was not different than that group II and did not increase with time. For the mechanical (material) properties of the healed MCL substance, the modulus of the healing tissue for group II was only 40% that of group I. The structural properties of the FMTC and the mechanical properties of the MCL substance from both groups at 6 and 12 weeks were significantly different from the contralateral controls. We further demonstrated that immediately after ACL reconstruction, the V–V rotation of group II knees could be restored to group I levels. Recent clinical studies of MCL healing following isolated complete ligament tears have suggested that nonoperative management without immobilization leads to excellent treatment outcome. However, in more severe injuries involving additional tissues, poor quality of the healed ligament tissue and articular degeneration are observed. Our results demonstrate the deleterious effects of an untreated triad injury on the healing of the MCL substance and its insertions. Examination of the MCL substance suggests that a much larger healing mass is formed following a triad injury, which partially compensates for inferior ligament mechanical properties. Therefore, this study indicates that alternative methods may be necessary to optimize MCL healing following a triad injury. Future studies will determine the consequences of such approaches.
Quantitation of in situ contact areas at the glenohumeral joint: A biomechanical study
Authors: Soslowsky L. J. , Flatow E. L. , Bigliani L. U. , Pawluk R. J. , Ateshian G. A. , Mow V. C.
Published: February 2005

Glenohumeral arthritis may result from abnormal articular mechanics, and shoulder reconstructive procedures often rely implicitly on the belief that the restoration of normal articular mechanics is required to obtain satisfactory clinical results. Despite this, limited knowledge of normal or pathologic glenohumeral joint articular mechanics and contact is available. This study uses a stereophotogrammetry technique to determine contact areas in normal cadaver glenohumeral joints with intact ligaments and capsule through a large range of motion using simulated forces of the four rotator cuff muscles and three deltoid heads. All shoulders were first elevated to their maximum elevation in the scapular plane at an external rotation (starting rotation = 40 ± 8°), which allowed each shoulder to attain its maximal elevation in the scapular plane, and then repeated at 20° internal to this rotation. Contact areas consistently increased with increasing elevation until 120° to an average of 5.07 cm2 before decreasing with further increased elevation to an average of 2.59 cm2 at 180° of total arm elevation. At 20° internal to the starting rotation, contact areas reached high values 60° earlier (averaged 4.56 cm2 at 60° of total arm elevation) and then remained fairly constant through 120° before decreasing with further increased elevation to 2.51 cm2 at 180° total arm elevation. With increasing elevation in the external starting rotation, humeral head contact dramatically migrates from an inferior region to a superocentral‐posterior region while glenoid contact shifts posteriorly. When the humeral shaft is positioned 20° internal to the starting rotation, humeral head contact shifts from inferocentral‐anterior to superocentral‐posterior regions. Simultaneously, a similar posterior shift in glenoid contact is observed. Furthermore, whereas only a small portion of the humeral head surface area is in contact in any given position, contact on the glenoid surface is much more uniformly distributed over its entire articulating surface.
Metabolic and biochemical status of articular cartilage following cryopreservation and transplantation: A rabbit model
Authors: Schachar N. , McAllister D. , Stevenson M. , Novak K. , McGann L.
Published: February 2005

To determine the fate of transplanted cryopreserved articular cartilage, an animal model employing the proximal humerus in the rabbit has been developed. Previous studies have been hindered by problems of postoperative joint instability, secondary injury due to immobilization, and paucity of cartilage for analysis. This experiment demonstrates the survival and function of transplanted cartilage by quantitative assessment of metabolic and biochemical parameters. Forty‐five New Zealand white rabbits underwent transplantation of the right proximal humerus. In 29 animals, the proximal half of the humerus was resected and replaced by a cryopreserved osteoarticular allograft. Autograft procedures were carried out in the remaining animals. Following sacrifice at 3, 6, 9, and 12 months postoperatively, articular cartilage was analyzed for gross appearance, collagen synthesis, proteoglycan synthesis, and water, hydroxyproline, hexosamine, and hexuronic acid contents. The results indicate that the cryopreserved osteoarticular allografts retained their metabolic and biochemical intergrity and behaved as viable and biologically functional units 1 year postoperatively.
Link protein shows species variation in its susceptibility to proteolysis
Authors: Liu J. , Cassidy J. D. , Allan A. , Neame P. J. , Mort J. S. , Roughley P. J.
Published: February 2005

Human cartilage link protein exists as three native components, while equine, bovine, and porcine cartilage link protein exist as two and Swarm rat chondrosarcoma link protein exists as only one component. These nonhuman link protein components represent intact protein structures, and there is little evidence for proteolytically modified forms in nonhuman tissues. In human cartilage, the proteolytic production of modified link proteins increases with age, whereas high amounts of such products were not seen in the nonhuman tissues. However, the small amounts of link protein fragments that were observed in the nonhuman cartilages were of a similar size to their human counterparts. On digestion of human proteoglycan aggregate with stromelysin, rapid modification of the link protein components occurred, whereas the aggregates from nonhuman cartilages showed incomplete cleavage of their link protein components. The relative resistance of nonhuman link protein to stromelysin may in part be due to a unique amino acid substitution present near the enzymic cleave site.
Initial characterization of the metabolism of intervertebral disc cells encapsulated in microspheres
Authors: Maldonado Brian A. , Oegema Theodore R.
Published: February 2005

Adult, canine intervertebral disc cells were isolated with a sequential digestion of pronase and bacterial collagenase. The nonchondrodystrophoid nucleus pulposus exhibits two populations of cells: large notochordal cells and smaller chondrocyte‐like cells. The cells from the transition zone and anulus fibrosus are uniform in size, ranging from 17 to 21 μm. The isolated cells were encapsulated in alginate beads and cultured in Ham's F‐12 medium containing 5% heat‐inactivated fetal bovine serum. Alginate bead formation requires calcium ions and can be reversed with a suitable chelator, thus releasing viable cells. We observed that 58% of the newly synthesized proteoglycans formed large‐molecular‐weight aggregates with hyaluronic acid. The proteoglycans contained low amounts of keratan sulfate (KS) (<5% of the total glycosaminoglycans synthesized). The chondroitin sulfates (CS) consisted of 51–67% as 6‐O‐sulfate and 29–39% as 4‐O‐sulfate, with the remainder (4–10%) present as 4,6‐sulfate for all three zones of the disc. The majority of cells synthesized significant amounts of matrix as evidenced by Alcian Blue staining. By immunohistochemical analysis, the matrix contained chondroitin 6‐sulfate as demonstrated by monoclonal antibodies to the unsaturated disaccharides remaining on the proteoglycan core after chondroitinase ABC digestion. Keratan sulfate was also present in the majority of the matrices around cells. These results emphasize the similarity of the newly synthesized proteoglycans secreted by cells grown in alginate beads to those synthesized by the neonate disc. These experiments also demonstrate the usefulness of this method as a microculture technique for disc cells.
Chondrocytes in agarose culture synthesize a mechanically functional extracellular matrix
Authors: Buschmann Michael D. , Gluzband Yehezkiel A. , Grodzinsky Alan J. , Kimura James H. , Hunziker Ernst B.
Published: February 2005

The ability of chondrocytes from calf articular cartilage to synthesize and assemble a mechanically functional cartilage‐like extracellular matrix was quantified in high cell density (∼ 107 cell/ml) agarose gel culture. The time evolution of chondrocyte proliferation, proteoglycan synthesis and loss to the media, and total deposition of glycosaminoglycan (GAG)‐containing matrix within agarose gels was characterized during 10 weeks in culture. To assess whether the matrix deposited within the agarose gel was mechanically and electromechanically functional, we measured in parallel cultures the time evolution of dynamic mechanical stiffness and oscillatory streaming potential in uniaxial confined compression, and determined the intrinsic equilibrium modulus, hydraulic permeability, and electrokinetic coupling coefficient of the developing cultures. Biosynthetic rates were initially high, but by 1 month had fallen to a level similar to that found in the parent calf articular cartilage from which the cells were extracted. The majority of the newly synthesized proteoglycans remained in the gel. Histological sections showed matrix rich in proteoglycans and collagen fibrils developing around individual cells. The equilibrium modulus, dynamic stiffness, and oscillatory streaming potential rose to many times (>5X) their initial values at the start of the culture; the hydraulic permeability decreased to a fraction (∼1/10) that of the cell‐laden porous agarose at the beginning of the culture. By day 35 of culture, DNA concentration (cell density), GAG concentration, stiffness, and streaming potential were all ∼25% that of calf articular cartilage. The frequency dependence of the dynamic stiffness and potential was similar to that of calf articular cartilage. Together, these results suggested the formation of mechanically functional matrix.
Intraosseous infusion using the osteoport implant in the caprine tibia
Authors: Welch R. D. , Waldron M. J. , Hulse D. A. , Johnston C. E. , Hargis B. M.
Published: February 2005

We evaluated the in vivo animal tolerance to intraosseous infusion via the Osteoport pediatric implant (model 2005PSO, Lifequest Medical, San Antonio, TX, U.S.A.) into the proximal tibia of immature goats and investigated the osseous effects of intermittent and sustained increases in intraosseous pressure (IOP). In group 1 (n = 3) autogenous whole blood was continuously infused (CI) for 5 days at flow rates producing an IOP of 30–45 mm Hg. Group 2 animals (n = 3) underwent a 5‐s high‐pressure infusion (HPI) of lactated Ringer solution (LRS) producing an IOP of 90–125 mm Hg twice daily for 10 days. In group 3, the Osteoports were left in place 5 (n = 2) or 10 days (n = 2) and evaluated for patency at 72‐h intervals. An IOP > 35 mm Hg produced clinical evidence of bone pain. Bone mineral density was significantly increased (p < 0.05) in all implanted tibias (mean 1.04 g/cm2; range 0.87–1.21 g/cm2) compared with controls (mean 0.67 g/cm2; range 0.65–0.71 g/cm2). A nonsignificant increase (+9% to +31%) in periosteal new bone formation occurred in all implanted tibias. In the continuously infused group, there was a significant increase (p < 0.05) in cancellous new bone formation (+ 483%), percentage eroded bone surface (+ 143%), and osteoclast covered bone surface (+ 255%) compared with controls. HPI of LRS did not produce significant bone changes. Seemingly, the Osteoport provided a ready means of intraosseous infusion and may be associated with less complications than current methods of continual vascular access. Bone changes correlated more with the duration than the magnitude of increased intraosseous pressures.
Strains and forces in selected carpal ligaments during in vitro flexion and deviation movements of the hand
Authors: Savelberg H. H. C. M. , Kooloos J. G. M. , Huiskes R. , Kauer J. M. G.
Published: February 2005

The forces induced in tiny wrist joint ligaments must be estimated in order to understand their role in the mechanism of the joint. We estimated forces in a number of selected ligaments in seven human wrist joint specimens, using a noninvasive method. The method is based on the rationale that the force generated in a ligament depends on its change of length with the joint under load. In vitro length changes of the ligaments were determined during flexion and deviation movements of the hand, using a roentgenstereophotogrammetric analysis technique. Subsequently, bone‐ligament‐bone (BLB) preparations were dissected from teh specimens. From these BLB preparations the zero‐force length and the force‐elongation relationship were determined in a material testing machine. The forces generated in the ligaments during flexion and deviation were calculated by combining results on the in vitro ligament length changes, the zero‐force length, and the force‐elongation relationship. Large interspecimen variations of the force patterns were found. Due to this variability, it is not possible to obtain quantitative models for the kinetic behavior of the ligaments. However, qualitative trends could be distilled from the strain and force patterns. It is clear that for most ligaments, the zero‐force lengths were not equal to the lengths they possessed in the neutral position of the hand. Furthermore, it could be shown which motions of the hand would most likely strain a particular ligament. It could be shown that the variations in the force patterns originate mainly from variations in the zero‐force lengths, and from variations in the force‐strain relationship between specimens. These variations might result from real differences between individuals as well as from artifacts introduced by the test method. Uncontrolled effects of frozen storage and unintentional preconditioning might negatively influence the variation. Because these artifacts are present from the initiation of the contribution of ligament forces to the kinematics of the wrist joint, which is very consistent between specimens, is of minor importance.
Forces and moments on the human leg in the frontal plane during static bipedal stance
Authors: Macmahon Edward B. , Carmines David V.
Published: February 2005

An experimental apparatus was assembled that permitted measurement of the vertical and lateral ground reaction forces as the hip is abducted, resulting in foot separations ranging from 0.25 to 71 cm, with the knee in 0° flexion. Twelve healthy volunteers (8 men and 4 women) were tested. The hip joint was located by means of center of rotation measurements on each subject's legs, and the location of the knee joint was determined using anatomical measurements. It was observed that the mediolateral force was nonzero and directed toward the body midline, even when the subject's feet were placed together. With the feet placed at shoulder width, the population mean mediolateral force was 3% of body weight. It was determined that simplifying assumptions based upon either “zero lateral force,” or “zero hip moment,” produced errors, when compared with our measured values, over various ranges of foot separation, with the zero hip moment assumption providing accuracy over a broader range. The inclination of the tibial plateau, with respect to the long axis of the tibia, that would produce minimal mediolateral shear at the knee is presented. Research and clinical applications of our results and techniques are discussed.
Proteoglycans in the compressed region of human tibialis posterior tendon and in ligaments
Authors: Vogel Kathryn G. , Ördög András , Pogány Gábor , Oláh Juliana
Published: February 2005

Proteoglycan content and tissue morphology were examined in tendons and ligaments from 24 cadavers, ranging in age at the time of death from 1.5 months to 83 years. The region of the human tibialis posterior tendon that passes under the medial malleolus was characterized by cells having a rounded shape, positive staining with alcian blue, and higher glycosaminoglycanuronic acid content than in the more proximal region of the same tendon. Analysis of proteoglycans by sodium dodecyl sulfate/polyacrylamide gel electrophoresis indicated that the predominant small proteoglycan of the proximal/tensional region was decorin, whereas two types of small proteoglycans (decorin and biglycan) and large proteoglycans were present in the region passing under the medial malleolus and presumably subjected to compressive and shear forces in addition to tension. The pattern of proteoglycan accumulation in the compressed region of tendon was basically similar for all individuals and showed no distinctive trends related to age after puberty. In terms of type and amount of proteoglycan, the patellar tendon was like the tensional region of the tibialis posterior. Glycosaminoglycan content in the lateral collateral ligament and anterior cruciate ligament, however, was twofold higher than in the tendons. The ligaments contained large as well as small proteoglycans, just as in the compressed region of tendon.
In vivo effects of naproxen on composition, proteoglycan metabolism, and matrix metalloproteinase activities in canine articular cartilage
Authors: Ratcliffee Anthony , Azzo Walid , Saed‐Nejad Fatemeh , Lane Nancy , Rosenwasser Melvin P. , Mow Van C.
Published: February 2005

Naproxen is a nonsteroidal anti‐inflammatory drug commonly used in the clinical treatment of joint disease. In this study, its effect in vivo on the biochemical composition, metabolic activities, and metalloproteinase activities of normal canine articular cartilage was analyzed. The articular cartilage from the knee joints of dogs who had been given naproxen for 4 weeks to maintain a serum level of 40–50 μg/ml was examined. Control animals were given a placebo. Treatment with naproxen was not found to change the composition (water, collagen, and proteoglycan) of the articular cartilage. The culture studies of cartilage explants indicated that proteoglycan synthesis rates were unaffected by the treatment with naproxen but that proteoglycan release from the tissue was suppressed. Analysis of the cartilage for matrix metalloproteinase activities showed reduced activity of neutral matrix metalloproteinase by 80%, of collagenase by 40%, and of gelatinase by 87%, with no change in activity of acid metalloproteinase or of tissue inhibitor for metalloproteinase. These findings indicate that in vivo treatment with naproxen has the capacity to modulate catabolic activities in articular cartilage.
Dynamic elongation behavior in the medical collateral and anterior cruciate ligaments during lateral impact loading
Authors: Yasuda Kazunori , Erickson Ann R. , Beynnon Bruce D. , Johnson Robert J. , Pope Malcolm H.
Published: February 2005

The objectives of this experimental study were to determine (a) how quickly the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) elongate when a lateral impact force is imparted to the knee and if a person can react rapidly enough to provide protective muscle forces in the case of such an impact. (b) if the MCL and the ACL elongate simultaneously during a lateral impact, and (c) if resection of the ACL affects elongation of the MCL during a lateral impact. Eight whole‐leg cadaver specimens were used. Each leg was mounted vertically in a testing‐frame with the knee in 0 and 30° of flexion. A submaximal impact was delivered from the lateral side by a pendulum instrumented with a force transducer. Elongation of the midsubstance of the MCL and the ACL was measured with Hall‐effect displacement transducers. The ACL was resected and the entire test sequence was repeated. Following a lateral impact, elongation of the MCL and ACL reached peak values by 70 ms. This study indicated that contraction of the leg musculature would not protect the MCL and ACL from injury when a lateral impact load is applied to the knee. The MCL and the ACL never elongated simultaneously during a lateral impact. After lateral impact loading, the time required to reach maximum elongation (peak delay) averaged 52 ms in the anterior MCL fibers and 61 ms in the ACL when the knee was in 0° of flexion. At 30° of flexion, the peak delay averaged 38 ms in the anterior MCL fibers and 22 ms in the ACL. The peak delay of the ACL was significantly greater than that of the MCL at 0° of the flexion (p < 0.05). The opposite was true at 30° of flexion. Resection of the ACL had only minimal effect on the elongation behavior of the MCL.
The maquet procedure: Effect of tibial shingle length on patellofemoral pressures
Authors: Pan H. Q. , Kish V. , Boyd R. D. , Burr D. B. , Radin E. L.
Published: February 2005

The Maquet procedure — elevation of the anterior tibial tubercle — has been recommended for treatment of symptomatic osteoarthrosis of the patellofemoral joint. Although the operation was first described 30 years ago, it remains controversial, both on a clinical and on a biomechanical basis. In addition, deterioration of the long‐term results has been suggested. One of the variables that has been ignored in both clinical and biomechanical studies has been tibial shingle length. In order to judge its effect, we examined contact pressures and areas in 15 cadaver knees with 7 and 20 cm tibial shingle lengths. We found significant patellofemoral pressure diminution only with 2 cm elevations. The short anterior tibial shingle with 2 cm of elevation tipped the patella on its superior pole, with a significant change in angle between the patella and the shingle. We suggest that this creates a potentially less than desirable biomechanical circumstance and believe it may explain the discrepancies among previously published reports.
Antibiotic‐loaded biodegradable bone cement for prophylaxis and treatment of experimental osteomyelitis in rats
Authors: Gerhart T. N. , Roux R. D. , Hanff P. A. , Horowitz G. L. , Renshaw A. A. , Hayes W. C.
Published: February 2005

A biodegradable, particulate composite bone cement containing gentamicin and vancomycin was used for both treatment and prophylaxis of Staphylococus aureus osteomyelitis in rats. Osteomyelitis was established by inoculating S. aureus into holes that were drilled in the proximal tibiae and were filled with polymethylmethacrylate (PMMA) cylinders. The cylinders were left in place for 3 weeks. The infections were serially evaluated by clinical and radiographic examination and by quantitative culture for colony forming units (CFUs) at the time the rats were killed. For treatment, cements containing antibiotic were implanted in animals that had established osteomyelitis and were left in place for an additional 3 weeks. Sites treated with biodegradable cement containing antibiotics exhibited significantly fewer CFUs in comparison with controls (p ≤ 0.01). Sites treated prophylactically with the biodegradable cement developed no infections as evaluated by clinical or radiographic criteria or by quantitative culture. At this relatively early time, no significant difference in therapeutic effectiveness was found when either the biodegradable cement or PMMA was used as a carrier for antibiotics.
A standardized experimental fracture in the mouse tibia
Authors: Hiltunen Ari , Vuorio Eero , Aro Hannu T.
Published: February 2005

The increased use of transgenic mice as experimental animals provides new opportunities to study the biology of fracture repair. We have developed a technique for the production of a standard closed experimental fracture in the mouse tibia. A 0.2 mm stainless‐steel rod was introduced into the medullary cavity and the pre‐nailed tibial shaft was fractured by an impact device, which resulted in a reproducible transverse or slightly oblique fracture pattern. The intramedullary rod maintained axial alignment, and the fractures united without displacement. On the basis of measurements of callus geometry, four‐point bending tests, biochemical analyses, and quantitative histology, the progress of callus formation and remodeling occurred in a predictable sequence of healing phases. The ultimate bending loads of the fractures increased with time, reaching 74% of the strength of intact control tibias in 4 weeks. The stiffness values of the fractures returned to normal levels and, as determined radiographically, the fractures united by external callus in 4 weeks. Radiographically, callus size, cross‐sectional callus area, and callus mass peaked at 2 weeks and decreased thereafter, indicating the start of external remodeling. Histologically, the amount of mesenchymal tissue was maximal at days 5 and 7. The callus cartilage area peaked at day 9; at its maximum, it accounted for 46% of the total callus area. Early periosteal formation of membranous new bone, followed by endochondral ossification, resulted in a linear increase of callus bone during the healing process. The healing sequence of the mouse tibial fracture was similar to that seen in the rat tibia. The major difference is the small size of the mouse, which makes the surgical technique and anesthetic procedures more demanding.