bluuebunny/crossref_metadata_2025 huggingface dataset:
Femoral prosthesis implantation induces changes in bone stress that depend on the extent of porous coating
Authors: Skinner Harry B. , Kim Agnes S. , Keyak Joyce H. , Mote C. D.
Published: February 2005

The objective of this study was to evaluate the effect of implantation of porous‐coated anatomic medullary fitting prostheses on stress in the proximal femur. Three‐dimensional finite element models of a cadaveric femur before and after implantation were used to evaluate the resulting changes in stress in the bone. Models of the femur were generated automatically from computed tomographic scan data with use of an innovative mesh‐generation technique. The models were analyzed for three levels of porous coating (proximal, 5/8, and full), with the assumption of ideal ingrowth (perfect bonding) over porous areas and a frictionless, tension‐free surface on smooth areas. All models were loaded and restrained to represent conditions of normal gait. The stresses predicted in the implanted femur are consistent with clinical observations of proximal cortical atrophy (normal stress reduced to 6‐9% of normal at the calcar and 50–55% at mid‐prosthesis) and of hypertrophy at the porous coating junctions (normal stress at the 5/8‐coating junction, 123% of stress proximal to the junction) and hypertrophy near the distal tip of the prosthesis (anterior and posterior normal stresses 200–800% of normal). The fully coated prosthesis induced stresses in the bone near the tip of the prosthesis that were most like stresses in the normal femur (medial and lateral normal stress 105 and 102% of the stress in the normal femur). Below the collar, the normal stress associated with the proximally coated prosthesis was 6% greater than that produced with the other two levels of coating but still was only 2% of normal. The 5/8‐coated prosthesis appeared to combine the worst features of the fully coated and proximally coated prostheses–greater stress‐shielding at the calcar and higher stress near the tip of the prosthesis.
Flexor tendon growth in chickens
Authors: Nishijima Naoki , Yamamuro Takao , Ueba Yasuo
Published: February 2005

We investigated the longitudinal growth of the flexor tendon in detail by marking tendons along their lengths in young chickens, using a microsurgical technique, and observing the separation of the marks at various times during tendon growth to establish normative standardized data on the longitudinal growth of flexor tendons. The interstitium throughout the entire tendon was found to increase in length, although the growth at the insertion zone was less marked than that in other areas. To determine the relationship between the growth of the tendon and the growth of the underlying bone, the lengths of the phalanges and metatarsus were measured. The distance from the insertion to the bifurcation of the tendon and the distance from the bifurcation to the most distal point of the musculotendinous junction also were measured. The findings suggest that the growth of tendon is proportionate to the growth of underlying bone. Tendon growth at the musculotendinous junction was studied in further detail, and no significant difference was found between growth at the most proximal zone of the tendon and growth at the zone within the musculotendinous junction.
Effect of sterilization on bone morphogenetic protein
Authors: Ijiri Shinichiro , Yamamuro Takao , Nakamura Takashi , Kotani Seiya , Notoya Kouchei
Published: February 2005

Demineralized bone matrix and bone morphogenetic protein have been used clinically to accelerate bone regeneration. However, the best method of sterilization has been the subject of controversy. Some investigators have used ethylene oxide, but others have reported that doses adequate for sterilization destroyed the osteoinductivity of demineralized bone matrix and that gamma irradiation was less harmful in this respect. We used partially purified bone morphogenetic protein and type‐I collagen to investigate the effects of sterilization by ethylene oxide and gamma irradiation on the activity of bone morphogenetic protein. Osteoinductivity was reduced considerably after sterilization by gamma irradiation at 2.5 Mrad and by ethylene oxide at 37°C for 4 hours and at 55°C for 1 hour; however, the reduction induced by ethylene oxide at 29°C for 5 hours was about half of the control values. This study showed that ethylene oxide at 29°C for 5 hours can be used clinically for sterilization of bone morphogenetic protein. We also investigated the effect of gamma irradiation on bone morphogenetic protein and the collagen carrier separately and found that collagen was far more labile than bone morphogenetic protein.
Determination of a zero strain reference for the anteromedial band of the anterior cruciate ligament
Authors: Fleming B. C. , Beynnon B. D. , Tohyama H. , Johnson R. J. , Nichols C. E. , Renström P. , Pope M. H.
Published: February 2005

The objective of this study was to verify a method previously used to determine a reference length for calculations of anterior cruciate ligament strain. In nine knee specimens, an arthroscopic force probe and a Hall effect transducer were placed in the anteromedial band of the ligament. Anteroposterior‐directed shear loads then were applied to the knee joint with the knee flexed to 30°. From the sigmoidal curve for shear load versus displacement of the anterior cruciate ligament midsubstance, the length of the transducer at the inflection point was determined graphically by two independent examiners. Previous studies suggested that the inflection point corresponds to the slack‐taut transition of the anteromedial band. The force probe was used to determine the actual length of the transducer when the anteromedial band became load bearing. No significant differences were found between the reference lengths determined by the inflection point method and the force probe. The force probe demonstrated that the anterior cruciate ligament became load bearing when an anterior shear load of 8.8 N was applied to the tibia with the knee at 30° of flexion. Furthermore, multiple cycles of anteroposterior shear loading did not influence these values. The force probe verified that the inflection method provides a reasonable estimate of the absolute strain reference (within 0.7% strain).
Tensile and viscoelastic properties of human patellar tendon
Authors: Johnson Greg A. , Tramaglini Dawn M. , Levine Rebecca E. , Ohno Kazunori , Choi Nam‐Yong , L‐Y. Woo Savio
Published: February 2005

The tensile and viscoelastic properties of fresh‐frozen, nonirradiated human patellar tendon were investigated in two groups of 15 specimens: one group was from individuals 29–50 years old and the other group was from individuals 64–93 years old. The central portion of each patella‐patellar tendon‐tibia complex was subjected to cyclic preconditioning, stress‐relaxation, cyclic stress‐relaxation, and load to failure tests. For each age group, stress‐relaxation and stress‐strain curves were obtained, from which percentage relaxation, ultimate tensile strength, strain at failure, modulus, and strain energy density were determined. Viscoelastic behavior was described with use of quasilinear viscoelasticity. The younger group showed a 46 ± 9% (mean ± SD) decrease in stress after 15 minutes, whereas the older group exhibited a 50 ± 6% decrease. The values for ultimate tensile strength and strain at failure, respectively, were 64.7 ± 15.0 MPa and 14 ± 6% for the younger group and 53.6 ± 10.0 MPa and 15 ± 5% for the older group. Modulus values were 660 ± 266 MPa for the younger group and 504 ± 222 MPa for the older group. Except for ultimate tensile strength, which was 17% less for the older group than for the younger one, no statistically significant differences were found in tensile or viscoelastic properties. This study indicated that there were minimal differences in biomechanical properties of the substance of the patellar tendon between younger and older age groups.
Systemic immune response to peripheral nerve transplants across major histocompatibility class‐I and class‐II barriers
Authors: Trumble Thomas E. , Gunlikson Ryan , Parvin Dara
Published: February 2005

The use of peripheral nerve transplantation in limb reconstruction has been limited by tissue rejection. In order to identify the major histocompatibility antigens involved in tissue rejection, mutant strains of inbred mice, differing from the parent strain (C57BL/6) by either major histocompatibility complex Class I (B6.C‐H2bml mice) or Class II (B6.C‐H2bml2 mice), were used in models of nerve transplantation. One, 2, and 3 weeks after nerve or skin transplantation, the immune response in the recipient animal was monitored with use of lymphocyte‐dependent cytotoxicity and complement‐dependent cytotoxicity assays. Skin transplants were used for comparison as the gold standard of a nonvascularized graft with an easily observable success or failure. There was no significant cellular immune response by the lymphocyte‐mediated cytotoxicity assay when nerve or skin transplants involved an isolated Class‐I or Class‐II mismatch, but there was a significant response 2 weeks after transplantations across a combined Class‐I and Class‐II barrier for nerve (p < 0.04) or skin (p < 0.03). An antibody response to the grafts occurred for both skin and nerve transplants but only when a combined barrier was involved. This preliminary study, using a mouse model, suggests that nerve transplantation may be performed without systemic evidence of rejection with only a partial cross match of the major histocompatibility complexes, thus decreasing the complexity of tissue typing necessary for tissue banking.
Effects of freeze/thaw conditioning on the tensile properties and failure mode of bone‐muscle‐bone units: A biomechanical and histological study in dogs
Authors: Gottsauner‐Wolf Florian , Grabowski John J. , Chao Edmund Y. S. , An Kai‐Nan
Published: February 2005

Eight pairs of canine supraspinatus bone‐muscle‐bone units were mechanically tested to failure in tension. One side was tested immediately post mortem, and the other side was tested after exposure to a standard freeze/thaw process (−60°C). The failure site was analyzed histologically. Fresh specimens had greater values for ultimate strength (p < 0.001), stiffness (p < 0.001), and energy to failure (p < 0.001). All specimens failed in the muscle close to the musculotendinous junction. The length of muscles subjected to the freezing process was reduced (9.3%). In addition, the load‐displacement curves for the fresh and frozen specimens showed marked differences in shape. The loss of tensile strength in muscle tissue is due to damage of the intracellular contractile elements caused by postmortem autolysis; this type of damage is increased as a result of the freeze/thaw process. The freeze/thaw process significantly altered the tensile properties of normal muscle tissue, no matter how carefully it was done. One cannot expect to receive representative data if muscle is frozen and thawed.
Indomethacin inhibition of ossification induced by direct current stimulation
Authors: Ijiri Kosei , Matsunaga Shunji , Fukuda Takeo , Shimizu Takao
Published: February 2005

In this study, we sought to clarify the mechanism of ossification induced by direct current stimulation by analyzing changes in local blood flow and vascular permeability and by examining the involvement of chemical mediators. Changes in blood flow were studied with laser Doppler flowmetry, and vascular permeability was determined by microquantification. To examine the involvement of chemical mediators, we determined the effect on vascular permeability of histamine H1 and H2‐receptor blockers and indomethacin. In addition, direct current stimulation was performed during administration of indomethacin to determine whether indomethacin inhibits electrically induced callus formation. Local blood flow remained unchanged in the control group and in the group receiving 5 μA of stimulation, but it increased in the groups receiving 10 and 50 μA. Vascular permeability increased in the 5 and 10 μA stimulation groups. This increase was not suppressed by histamine‐receptor blockers, but it was suppressed by indomethacin. Two weeks of electrical stimulation without concomitant indomethacin treatment resulted in active callus formation around the needle electrode and in the vicinity of the endosteum; however, direct current stimulation during administration of indomethacin inhibited callus formation. The results suggest that these changes serve as microenvironmental factors that play an important role in the promotion of ossification and that a prostaglandin‐mediated mechanism is involved in the promotion of ossification by direct current stimulation.
Rabbit medial collateral ligament scar weakness is associated with decreased collagen pyridinoline crosslink density
Authors: Frank C. , McDonald D. , Wilson J. , Eyre D. , Shrive N.
Published: February 2005

This study was carried out to quantify the potential associations between material strength and both collagen concentration and pyridinoline collagen crosslink density in the healing medial collateral ligament of the rabbit and to compare these parameters with those of normal ligaments. The right hindlimbs of 24 skeletally mature (12‐month‐old) New Zealand White rabbits were subjected to a standardized 4 mm midsubstance “gap” injury to the medial collateral ligament. The animals were killed in groups of six at postoperative intervals of 3, 6, 14, or 40 weeks, and the femur‐medial collateral ligament‐tibia complexes were mechanically tested in tension to failure. Subsequent to mechanical testing, the failure sites of the ligaments were assessed for concentrations of hydroxyproline and hydroxylysyl pyridinoline. Nine additional rabbits served as age‐matched normal controls. In healing ligaments, normal collagen concentrations were reached in less than 14 weeks, but the hydroxylysyl pyridinoline crosslink densities remained low and were only 45% of the control values after 40 weeks of healing. Similarly, mechanical values remained much less than the controls. Linear regression analysis of data on scar tissue alone showed a moderately strong positive correlation between hydroxyproline concentration and material strength (r2 = 0.51, p = 0.0001) but no correlation between crosslink density and strength of scar tissue. A similar pattern of correlation was obtained between the elastic modulus of the scar tissue and the biochemical variables, but the r2 values were lower. When control data were included, the results of stepwise regression showed a very high positive correlation between crosslink density and material strength (r2 = 0.83, p < 0.0001) and discriminant analysis demonstrated crosslink density to be the best classifier of group membership. Combined with hydroxyproline concentration, crosslink values correctly identified healing interval and group 90% of the time. These results suggest that although collagen concentration definitely plays a more important role in determining the early material behaviour of healing medial collateral ligaments, reduced crosslink density in collagen in scar tissue may offer a more specific explanation for the mechanical inferiority, in the rabbit, of healing medial collateral ligaments compared with normal ligaments over time.
Effect of growth factors on the proliferation of fibroblasts from the medial collateral and anterior cruciate ligaments
Authors: Schmidt C. C. , Georgescu H. I. , Kwoh C. K. , Blomstrom G. L. , Engle C. P. , Larkin L. A. , Evans C. H. , Woo S. L‐Y.
Published: February 2005

Growth factors have been shown to stimulate fibroblast division and thus may influence ligament healing. We analyzed the effects of individual growth factors on the proliferation of fibroblasts from the medial collateral and anterior cruciate ligaments of the rabbit in vitro in order to identify growth factors that might enhance proliferation of fibroblasts and to compare the responses of the fibroblasts from the two ligaments to these growth factors. Through measurement of the uptake of [3H]‐thymidine into DNA, fibroblasts from these ligaments that had been treated with epidermal growth factor and basic fibroblast growth factor were found to proliferate nearly eight times more than control fibroblasts. Additionally, the fibroblasts of both ligaments proliferated at similar rates when exposed to platelet‐derived growth factor‐AA, platelet‐derived growth factor‐BB, basic fibroblast growth factor, insulin‐like growth factor‐1, and interleukin‐1‐alpha. However, epidermal growth factor and transforming growth factor‐beta caused the fibroblasts from the medial collateral ligament to proliferate at a rate 1.3–1.4 times greater than that of fibroblasts from the anterior cruciate ligament. The reverse was true with acidic fibroblast growth factor, which stimulated the fibroblasts from the anterior cruciate ligament to proliferate at a rate 1.3–1.6 times greater than that of fibroblasts from the medial collateral ligament. This study demonstrated that growth factors can stimulate cell division in ligaments and may be effective in enhancing ligament healing but that these differences were not great enough to explain fully the clinical differences observed between healing of the medial collateral and anterior cruciate ligaments.
Structure of chondroitin sulfate on aggrecan isolated from bovine tibial and costochondral growth plates
Authors: Deutsch Angela J. , Midura Ronald J. , Plaas Anna H. K.
Published: February 2005

The structure of chondroitin sulfate on aggrecan isolated from the rib and proximal tibial growth plates of bovine fetuses was investigated, and the previously reported increase in the hydrodynamic size of chondroitin sulfate chains between the reserve and hypertrophic zones of the rib was confirmed in the tibial growth plate. Superose 6 gel chromatography, calibrated for chondroitin sulfate chain length by monosaccharide analysis, showed that the average molecular mass of chondroitin sulfate in the reserve and maturing zones of both growth plates was 21,600 and 30,400, respectively. Determination by capillary zone electrophoresis of the disaccharide composition of chains following chondroitinase digestion showed that ΔDi‐0S, ΔDi‐4S, and ΔDi‐6S together accounted for more than 98% of the disaccharides in the digests from all zones of both growth plates; Δdisulfated and Δtrisulfated disaccharides were not detected. Furthermore, this analysis revealed a gradient in chondroitin sulfate composition from the reserve to the hypertrophic zone, characterized by a marked increase in the content of ΔDi‐6S (from about 32% to about 52%) and a marked decrease in the content of ΔDi‐4S (from about 53% to about 35%). Moreover, this altered pattern of sulfation was detected on chains of all sizes in the hypertrophic zone, suggesting that a proportion of the reserve zone aggrecan might be removed and replaced with aggrecan rich in chondroitin‐6‐sulfate synthesized during the proliferative and maturation stages of the resident chondrocytes. These data are discussed in relation to the biosynthetic mechanisms that control chondroitin sulfate chain length and sulfation on aggrecan and their modification during chondrocyte proliferation, maturation, and hypertrophy in the growth plate.
Subchondral bone density in the human elbow assessed by computed tomography osteoabsorptiometry: A reflection of the loading history of the joint surfaces
Authors: Eckstein Felix , Müller‐Gerbl Magdalena , Steinlechner Martin , Kierse Robert , Putz Reinhard
Published: February 2005

The functional adaptation of bone tissue to the mechanical stresses acting on it has been convincingly established. This association should apply as well to the subchondral bone, reflecting the long‐term distribution of stress over the joint surfaces. Thirty‐six specimens of the human elbow joint were investigated by computed tomography osteoabsorptiometry in order to assess the distribution of he subchondral mineralization. The distal surfaces usually were more highly mineralized than the proximal components of the joint, whereas the humeroulnar and the humeroradial parts exhibited a similar degree of mineralization. The fovea of the radial head always showed a central density maximum, and the trochlear notch usually presented a bicentric distribution pattern, with maxima beneath the ventral and dorsal regions of the articular surface. The different patterns of subchondral mineralization were shown to reflect the loading history of the overlying articular surfaces, which is determined mainly by geometrical factors. The flatter socket of the humeroradial joint leads to central load transmission, but the deeper socket of the humeroulnar joint will, by contrast, give rise to bicentric stress distribution.
Co‐contraction of lumbar muscles during the development of time‐varying triaxial moments
Authors: Thelen D. G. , Schultz A. B. , Ashton‐Miller J. A.
Published: February 2005

The recruitment and co‐contraction of lumbar muscles were investigated during the voluntary development of slowly and rapidly varying trunk flexion and extension, lateral bending, and axial twisting moments. Myoelectric signals were recorded from 14 lumbar muscles in nine young men during maximum voluntary exertions and cyclic isometric exertions. System identification techniques were used to calibrate dynamic models of the relationship between myoelectric signals and force. To assess co‐contraction, the predicted muscle forces were subdivided into a task‐moment set of muscle forces that minimally satisfied moment equilibrium and a co‐contraction set of muscle forces that produced zero net moment. The sum of co‐contraction muscle forces was used to quantify the degree of co‐contraction present. Co‐contraction was largely dependent on the direction of exertion and relatively less dependent on the subject or the rate of exertion. Co‐contractions were estimated to contribute approximately 16–19% to the sum of muscle forces at a lumbar cross section during attempted extension of the trunk. Estimated co‐contractions during attempted lateral bending and axial twisting were two to three times greater, which demonstrates that co‐contraction is a major determinant of spinal loading in these tasks. This analysis suggests that substantial contractions of lumbar muscles, especially during asymmetric exertions, are used for reasons other than equilibrating moments at the L3‐L4 level.
Chondrocyte deformation and local tissue strain in articular cartilage: A confocal microscopy study
Authors: Guilak Farshid , Ratcliffe Anthony , Mow Van C.
Published: February 2005

It is well accepted that mechanical forces can modulate the metabolic activity of chondrocytes, although the specific mechanisms of mechanical signal transduction in articular cartilage are still unknown. One proposed pathway through which chondrocytes may perceive changes in their mechanical environment is directly through cellular deformation. An important step toward understanding the role of chondrocyte deformation in signal transduction is to determine the changes in the shape and volume of chondrocytes during applied compression of the tissue. Recently, a technique was developed for quantitative morphometry of viable chondrocytes within the extracellular matrix using three‐dimensional confocal scanning laser microscopy. In the present study, this method was used to quantify changes in chondrocyte morphology and local tissue deformation in the surface, middle, and deep zones in explants of canine articular cartilage subjected to physiological levels of matrix deformation. The results indicated that at 15% surface‐to‐surface equilibrium strain in the tissue, a similar magnitude of local tissue strain occurs in the middle and deep zones. In the surface zone, local strains of 19% were observed, indicating that the compressive stiffness of the surface zone is significantly less than that of the middle and deep zones. With this degree of tissue deformation, significant decreases in cellular height of 26, 19, and 20% and in cell volume of 22, 16, and 17% were observed in the surface, middle, and deep zones, respectively. The deformation of chondrocytes in the surface zone was anisotropic, with significant lateral expansion occurring in the direction perpendicular to the local split‐line pattern. When compression was removed, there was complete recovery of cellular morphology in all cases. These observations support the hypothesis that deformation of chondrocytes or a change in their volume may occur during in vivo joint loading and may have a role in the mechanical signal transduction pathway of articular cartilage.
Comparative study of the size and shape of human anterior and posterior cruciate ligaments
Authors: Harner C. D. , Livesay G. A. , Kashiwaguchi S. , Fujie H. , Choi N. Y. , Woo S. L.‐Y.
Published: February 2005

As an important step toward determination of the function of cruciate ligaments, the cross‐sectional shapes and areas of the anterior cruciate, posterior cruciate, and meniscofemoral ligaments were evaluated in situ within the same knee with use of a laser micrometer system. Measurements were made in eight human cadaveric knees at five levels along the midsubstance of each ligament, with the knee at 0°, 30°, 60°, and 90° of flexion. The posterior cruciate ligament was found to be widest in the medial‐lateral direction, whereas the anterior cruciate ligament usually was larger in the anterior‐posterior direction. The cross‐sectional shapes of the anterior cruciate ligament generally were noted to be more circular along the entire midsubstance than were those of the posterior cruciate ligament. In contrast, the cross‐sectional shapes of the posterior cruciate ligament were more circular near the tibia, becoming progressively more elongated toward the femur. The meniscofemoral ligaments were more circular than the cruciate ligaments, with an occasional medial‐lateral widening similar to that of the posterior cruciate ligament. The cross‐sectional area of both the cruciate ligaments changed along the length of the midsubstance, with the anterior cruciate ligament becoming slightly larger distally and the posterior cruciate ligament enlarging proximally. The angle of flexion of the knee was not found to have a significant effect on the cross‐sectional areas of the ligaments but was noted to alter the cross‐sectional shapes. Using within‐specimen comparisons, the cross‐sectional area of the posterior cruciate ligament was found to be approximately 1.5 times larger than that of the anterior cruciate ligament at the proximal and midsubstance levels but was only 1.2 times larger at the most distal level. The total cross‐sectional area of the meniscofemoral ligaments was approximately 22% that of the posterior cruciate ligament.
Endochondral resorption of chick sterna in culture
Authors: Gibson Gary J. , Lin Dan Li , Schaffler Mitchell B. , Kimura James H.
Published: February 2005

Endochondral resorption is most clearly recognized at the metaphyseal interface of the growth plate with the adjacent vasculature: however, apparently identical processes of endochondral resorption are seen in sites of primary and secondary ossification of the cartilaginous anlage of bones and in ossifying fracture callus. Recent evidence of the expression of the hypertrophic phenotype in osteoarthrotic articular cartilage suggests that endochondral resorption also may be a factor in the loss of articular cartilage in this condition. To investigate the mechanism of endochondral resorption, a model culture system was developed and characterized. The two primary centers of ossification with surrounding cartilage were dissected from embryonic chick sterna prior to (18‐day‐old embryos) or after (20‐day‐old embryos) the initiation of resorption. They were cultured either in plastic culture dishes or on chorioallantoic membranes, and resorption was detected by analysis of the loss of types II and X collagen and by histological characterization. Only sterna showing active resorption in vivo were resorbed when cultured on chorioallantoic membrane. The histological appearance of the resorption site and the specificity of resorption to the primary ossification center, seen from both the analysis of loss of collagen and histological observation, suggested that the resorption of sterna cultured on chorioallantoic membrane was similar to that observed in vivo. These studies further indicated that both vascular cells and viable chondrocytes were required for resorption. Susceptibility to resorption could be induced in resistant primary ossification centers by prior culture in the absence of vascular cells, and it is suggested that it results from the accumulation of resorption‐susceptible cells and matrix as a result of continued chondrocyte development.
Effect of tissue culture storage on the in vivo survival of canine osteochondral allografts
Authors: Oates K. M. , Chen A. C. , Young E. P. , Kwan M. K. , Amiel D. , Convery F. R.
Published: February 2005

In vitro studies in our laboratory have shown that the biomechanical and biochemical characteristics of osteochondral grafts can be preserved for as long as 28 days under tissue culture conditions. This study represents an attempt to extend these results to an in vivo model. In adult mongrel dogs, either an autograft, a fresh allograft, or a stored allograft was placed in a standardized defect on the weight‐bearing surface of the medial femoral condyle. The stored grafts were kept at 4°C in tissue culture medium for 14 days prior to implantation. The animals were killed at 12 weeks. Cartilage from the contralateral knee served as a control. The modulus and permeability of the cartilage were assessed with confined compression creep tests. The collagen and glycosaminoglycan contents were measured, and the cartilage was analyzed histologically with hematoxylin and eosin and safranin O stains. Grossly, the cartilage appeared viable at harvest. The histologic results were similar in the treatment groups, with the same spectrum of mild degenerative changes being noted in each group. The glycosaminoglycan content was significantly less in the autograft group than in its control group and than in the fresh allograft group. The glycosaminoglycan content did not differ significantly between fresh and stored allografts. The collagen content, modulus, and permeability did not differ either between experimental and control groups or between graft types. Our results support the conclusion that osteochondral allografts can be stored for as many as 14 days without significantly affecting the results of the procedure.
Tensile properties of the supraspinatus tendon
Authors: Itoi Eiji , Berglund Lawrence J. , Grabowski John J. , Schultz Fredrick M. , Growney Eric S. , Morrey Bernard F. , An Kai‐Nan
Published: February 2005

The tensile properties of the supraspinatus tendon were investigated in 11 shoulders from fresh cadavers. The tendon was divided into three longitudinal strips: anterior, middle, and posterior. Each specimen was mounted on a materials testing machine, with four fluorescent markers placed on both surfaces of the tendon strip. The positions of these markers were recorded during the test by two synchronized video cameras. Load‐deformation and strain curves were determined, and the stress‐strain curve, strength, and modulus of elasticity were calculated. The posterior strip was thinner in cross section than the others (p = 0.0355). The ultimate load and ultimate stress were significantly greater in the anterior strip (16.5 ±7.1 MPa) than in the middle (6.0 ± 2.6 MPa) and posterior (4.1 ± 1.3 MPa) strips (p < 0.0001). The modulus of elasticity also was significantly greater in the anterior strip (p < 0.0001), but there was no significant difference between the superficial and deep surfaces. It is concluded that the anterior portion of the supraspinatus tendon is mechanically stronger than the other portions, and it seems to perform the main functional role of the tendon.
Biomechanical analysis of the ankle anterior drawer test for anterior talofibular ligament injuries
Authors: Tohyama Harukazu , Beynnon Bruce D. , Renström Per A. , Theis Maureen J. , Fleming Braden C. , Pope Malcolm H.
Published: February 2005

The effect of sectioning the anterior talofibular ligament on the load‐displacemnt behavior of the ankle was evaluated in vitro during the anterior drawer test using the flexibility approach. Controlled forces were applied across the ankle joint in the anterior‐posterior direction, and the resulting displacements were measured at four flexion angles (10° of dorsiflexion, neutral, and 10° and 20° of plantar flexion). The anterior talofibular ligament then was sectioned, and the anterior‐posterior loadings were repeated at the four flexion angles. Two parameters were developed to describe the nonlinear load‐displacemnt response of the ankle joint: neutral zone laxity (joint displacement between ± 2.5 N) and flexibility (a measure of the nonlinear load‐displacement response of the ankle between 10 and 50 N of anterior drawer loading). After sectioning the anterior talofibular ligament, significant increases in neutral zone laxity were observed at all angles of ankle flexion. The largest increases in neutral zone laxity were found with the ankle in 10° of plantar flexion (76.3% increase) and 20° of plantar flexion (89.7% increase). After sectioning the ligament, a significant increase (19.3%) in flexibility of the ankle was observed at 10° of dorsiflexion, but no change in flexibility was observed with the ankle in the neutral and plantar flexed positions. These findings indicate that anterior drawer testing of the anterior talofibular ligament‐deficient ankle between 10° and 20° of plantar flexion results in the largest increase in neutral zone laxity compared with the normal ankle with intact ligaments. They also suggest that an excessive magnitude of force during clinical application of the anterior drawer examination may not be needed to diagnose disruption of the anterior talofibular ligament.
Proliferative and phenotypic responses of bone‐like cells to mechanical deformation
Authors: Stanford C. M. , Morcuende J. A. , Brand R. A.
Published: February 2005

Limited in vivo and in vitro experiments suggest that bone and bone‐like cells respond to mechanical signals in a trigger‐like rather than a dose‐response fashion; i.e., they fail to respond until they have been stimulated with some given number of cycles of loading, and then once they respond, additional cycles produce little or no effect. To explore this notion, rat calvaria‐derived osteoblast‐like cells and the cell line MC3T3‐E1 were plated at a high cell density (5,000 cells/mm2) on silicone membranes coated with type‐I collagen and were allowed to attach for 24 hours. The membranes then were exposed to vacuum pressure (−1 kPa, 0.5 Hz) on a daily basis, and cultures were assayed every 2 days for 2 weeks. The proliferation of nontransformed cells increased 7‐fold with as few as four daily cycles but not with one cycle per day. Furthermore, 1,800 cycles of vacuum did not result in a greater response than four cycles per day. We observed inverse phenotypic responses: the expression of osteocalcin was depressed compared with controls in the cultures of osteoblast‐like cells that were strained with as few as four cycles per day. Alkaline phosphatase activity was depressed in the cultures of both the osteoblast‐like cells and the MC3T3‐E1 cells exposed to low vacuum pressures (−1 kPa) with four daily cycles of vacuum pressure. Increasing the vacuum magnitude did not affect the occurrence of a “trigger response” between one and four cycles of vacuum application. Bone‐like cells in vitro appear to exhibit trigger‐response behavior analogous to that seen in bone in vivo; the phenotypic response occurs in the opposite direction from the proliferative response.
Time‐dependent changes in the response of cartilage to static compression suggest interstitial pH is not the only signaling mechanism
Authors: Boustany Nada N. , Gray Martha L. , Black Ann C. , Hunziker Ernst B.
Published: February 2005

The goal of the present study was to reexamine the role of interstitial pH in regulating the biosynthetic rate in cartilage tissue by addressing two research questions: (a) Do small, short‐term changes in interstitial pH, induced independently by two different mechanisms (namely, by controlling the pH of the medium or by mechanical compression), result in biosynthetic rates commensurate with those expected from the “natural” relationship between interstitial pH and biosynthesis? and (b) Are the effects of changes in the pH of the medium or in compression the same for short‐term (14‐hour) and long‐term (60‐hour) exposures? Biosynthetic rates were estimated from incorporation of sulfate and proline into explants of bovine epiphyseal cartilage during the final 14 hours of culture. These rates decreased with decreasing pH of the medium, with increasing compression, and with decreasing native glycosaminoglycan content; or, expressed in terms of interstitial pH, acidification induced by compression or by lowering the pH of the medium resulted in a decreased biosynthetic rate, whereas interstitial acidification effected by increasing glycosaminoglycan content enhanced it. When the time for which tissue was exposed to changes in the pH of the medium was increased from 14 to 60 hours, the relationship between the biosynthetic rate and the pH remained constant whereas the relationship between the biosynthetic rate and compression was reversed. These data suggest that the transduction mechanisms underlying the response to pH of the medium and compression differ and that some adaptation or stimulation by modest levels of compression can occur with longer exposures. Interstitial pH is not the sole determinant of biosynthesis, and it cannot really account for the long‐term response of cartilage tissue to static compression.
Primary osteoarthrosis in guinea pigs: A stereological study
Authors: de Bri Edin , Reinholt Finn P. , Svensson Olle
Published: February 2005

Volumes and surfaces of articular cartilage and subchondral bone of the proximal tibial epiphysis were measured by unbiased stereological methods on the light microscopic level in groups of 6, 12, and 30‐month‐old (adult, middle‐aged, and old) guinea pigs with primary osteoarthrosis. At 12 months, structural changes similar to those of human osteoarthrosis had developed, predominantly on the central medial condyle, which was not covered with meniscus. The lateral condyle was virtually unaffected; this allowed separate analysis of age‐related and disease‐related changes. Fibrillation and destruction of cartilage was accompanied by a simultaneous increase of the volume of both cartilage (66%) and subchondral bone (50%). The epiphyseal volume increased by 27% at 12 months, predominantly on the medial (osteoarthrotic) condyle, whereas the volume of the lateral condyle increased only in the oldest age group; this indicated that the joint has a potential for growth and remodeling. Joint growth has been suggested as a pathogenic factor in osteoarthrosis. The 65% increase in thickness noted in subchondral bone was a further indication of the importance of proliferative bone changes in early osteoarthrosis. The low variability of osteoarthrosis in this animal model makes it possible to obtain stable quantitative data from relatively small groups of animals.
Arthritis not immobilization causes bone loss in the carrageenan injection model of inflammatory arthritis
Authors: Bogoch E. R. , Moran E. , Crowe S. , Fornasier V.
Published: February 2005

One suggested cause of the high turnover osteopenia of experimental inflammatory arthritis is disuse of affected joints. To compare the influence of immobilization or disuse, or both, with that of inflammatory arthritis on bone turnover, rabbits were placed into four groups. In group 1, arthritis was induced in the right knee by seven intra‐articular injections of 1% carrageenan, over 49 days; in group 2, a plaster cast was applied to immobilize the right hindlimb in flexion; in group 3, arthritis was induced and the hindlimb was immobilized; and in group 4, nothing was done (control). The fluorescent label calcein was administered in drinking water (0.05%) ad libitum to all groups on days 22‐36. On day 49, specimens were prepared for analysis of bone volume and new bone volume at a near site (right femur) and at remote sites (contralateral femur and ipsilateral humerus). The data were analysed by multiple regression and Bonferroni tests. In group 1, new bone volume was three times higher than in group 2 or 4 (p < 0.05 for each comparison); this indicated increased bone remodeling in the right femur. This contrasted with group 2, in which neither index of bone remodeling was changed. The combination of immobilization with arthritis resulted in more intense osseous effects of inflammatory arthritis, with a one‐quarter decrease in bone volume (group 3,30.99 ± 2.50; group 4, 42.07 ± 2.38, p < 0.05), as well as a 4‐fold increase in new bone volume (p < 0.001) compared with group 1. A possible systemic effect in this model of arthritis was evidenced by increased new bone volume in the contralateral femur in the group that had arthritis and immobilization (4.66 ± 0.57, p < 0.05).
Bisphosphonate (pamidronate/APD) prevents arthritis‐induced loss of fracture toughness in the rabbit femoral diaphysis
Authors: Bellingham Catherine M. , Lee J. Michael , Moran Erica L. , Bogoch Earl R.
Published: February 2005

Patients with rheumatoid and other inflammatory arthritis have an increased risk for fracture. This study was designed to determine the effect of experimental inflammatory arthritis on the material properties (fracture toughness and shear modulus) and structural properties (torque, angular defelection, and absorbed energy) of femoral diaphyseal bone tested in torsion to fracture, as well as the effect on these properties of APD (3‐amino‐1‐hydroxypropylidene‐1,1‐bisphosphonate), a drug known to block osteoclast activity. Two dose levels were investigated. Experimental inflammatory arthritis was induced by intra‐articular injection of carrageenan into the right tibiofemoral joint, given over 7 weeks, in three groups of animals. Simulataneously, daily subcutaneous injections of APD were given to three groups of rabbits. Five groups (12 animals each) were established: normal, arthritis, normal/high dose APD, arthritis/high dose APD, and arthritis/low dose APD. The diaphyses of each excised right femur were loaded to fracture in torsion at an angular deflection rate of 8°/sec. In the arthritis group, the fracture toughness was 39% lower than in the normal group, and the structural properties all were reduced significantly. By contrast, the shear modulus was unaffected by arthritis. In this study, the higher dose level (0.3 mg/kg of body weight) of APD prevented loss of fracture toughness and maintained the structural properties in experimental inflammatory arthritis; the low dose was not effective.
Induction of bone by a demineralized bone matrix gel: A study in a rat femoral defect model
Authors: Feighan John E. , Davy Dwight , Prewett Annamarie B. , Stevenson Sharon
Published: February 2005

Demineralized bone matrix contains osteoinductive factors and stimulates filling of gaps and defects with bone; however, it is difficult to handle by itself and various preparations have been tested. Demineralized bone matrix with a gel consistency now is available for clinical use. We studied, in a femoral segment defect in the rat, the effects of rat demineralized bone matrix gel with and without a ceramic substratum. This preparation is analogous to the human demineralized bone matrix in the same carrier, used clinically for humans. One hundred adult male Fischer rats were divided into 10 experimental groups. Independent variables included the presence or absence of hydroxyapatite ceramic cylinders, the presence of demineralized bone matrix in carrier or carrier alone (glycerol), and the duration of observation (1, 2 and 4 months). Defects filled with the gel alone had significantly higher radiographic scores for host‐graft union at 4 months compared with ceramic with the gel, ceramic alone, or carrier alone. Demineralized bone matrix gel significantly increased the total histologic score for host‐graft union, whether ceramic was present or not, and a three‐way interaction occurred among ceramic, the gel, and time. Demineralized bone matrix gel was an effective inducer of bone formation in this model. An additional substratum was not required; in fact, significantly more bone was formed in the absence of the ceramic cylinder. Neither the gel nor the ceramic were impediments to revascularization of the defect. Host‐graft union was enhanced by demineralized bone matrix gel but not by the ceramic cylinder.
Tumor osteolysis in osteopetrotic mice
Authors: Clohisy Denis R. , Ogilvie Christian M. , Ramnaraine Margaret L. R.
Published: February 2005

Details of the cellular and biochemical mechanisms involved in focal destruction of bone at sites of tumor osteolysis are unknown. It has been shown that tumors from sarcoma (2472) cell lines induce focal osteolysis in mice by stimulating formation and activation of osteoclasts. In this report, the influence of 2472 tumors on the skeletons of osteoclast‐deficient animals (op/op) was studied. After op/op femora had been inoculated with 2472 cells, tumors developed and focal osteolysis occurred. There were more osteoclasts per histologic section in sham‐injected femora (19 ± 5) than in tumor‐bearing femora (412 ± 129) (p < 0.05). The size of the osteoclasts also increased from 304 ± 81 μm2 in sham‐injected limbs to 407 ± 62 μm2 in tumor‐bearing limbs (p < 0.001). Conditioned media from 2472 op/op tumor explants contained macrophage colony‐stimulating factor. A deficiency of osteoclasts in op/op mice is the result of the absence of this factor; therefore, these data introduce the possibility that macrophage colony‐stimulating factor derived from 2472 tumor may be responsible for directing osteoclast‐mediated osteolysis at sites of the tumor.
Subfracture insult to the human cadaver patellofemoral joint produces occult injury
Authors: Atkinson Patrick J. , Haut Roger C.
Published: February 2005

The current criterion used by the automotive industry for injury to the lower extremity is based on visible bone fracture. Studies suggest, however, that chronic joint degeneration may occur after subfracture impact loads on the knee. We hypothesized that subfracture loading of the patellofemoral joint could result in previously undocumented microtrauma in areas of high contact pressure. In the current study, seven patellofemoral joints from human cadavers were subjected to impact with successively greater energy until visible fracture was noted. Transverse and comminuted fractures of the patella were noted at 6.7 kN of load. Approximately 45% of the impact energy then was delivered to the contralateral joint. Subfracture loads of 5.2 kN resulted in no gross bone fracture in five of seven specimens. Histological examination of the patellae revealed occult trauma in four of the seven specimens in the subfracture group; trauma consisted of a horizontal split fracture in the subchondral bone, at the tidemark, or at the interface of calcified cartilage and subchondral bone. The trauma appeared predominantly on the lateral facet, adjacent to or directly beneath preexisting fibrillation of the articular surface. Surface fibrillation was noted in histological sections of control patellae (not subjected to impact loading), but occult damages were not observed. Although the mechanism of this occult trauma is unknown, similar damage has been shown to occur from direct shear loading. As these microcracks can potentiate a disease process in the joint, this study may suggest that the current criterion for injury, based on bone fracture alone, is not sufficiently conservative.