bluuebunny/crossref_metadata_2025_split huggingface dataset:
Restoration of tissue components after insertion of absorbable fracture fixation devices of polyglycolide through the articular surface: An experimental study in the distal rabbit femur
Authors: Böstman Ole , Päivärinta Unto 
Published: February 2005

AbstractAbsorbable implants for fracture fixation do not require a secondary removal procedure, a fact that could make them particularly suitable for intra‐articular fixation, provided the degree of regeneration of the articular surface is acceptable. To determine the restoration pattern in distal rabbit femurs after the intra‐articular insertion of absorbable fixation devices, polyglycolide pins and screws were implanted through the articular surface of the intercondylar portion of the bone in adult animals. The polymer was known to have a degradation time of approximately 20 weeks. At follow‐up times of 3–48 weeks, the restoration of the tissue components was examined histomorphometrically and microradiographically. The intact contralateral femur served as an internal control. The first signs of degradation of the implants were seen at 6 weeks. The mean fractional osteoid formation surface of the bone trabeculae within the sample fields showed significantly increased values until 6 weeks but thereafter approached the level of the control femur. In the 36‐week and 48‐week specimens, the polyglycolide had been absorbed and the intra‐articular entrance of the implant channel had become filled either with firm whitish tissue resembling mature articular cartilage or with soft undifferentiated mesenchymal tissue only. Good restoration of the trabecular bone archtecture corresponding to the original subchondral bone was a prerequisite for the regeneration of the articular cartilage. The causes of the dichotomous pattern of restoration could not be identified, but possibly it represented a normal biologic variation. Since instability associated with fracture fixation, not an issue of this study, could affect the quality of tissue restoration, the present findings call for caution if large‐diameter absorbable devices are to be inserted through articular surfaces in clinical practice.
Role of fibronectin in staphylococcal adhesion to metallic surfaces used as models of orthopaedic devices
Authors: Delmi M. , Vaudaux P. , Lew D. P. , Vasey H. 
Published: February 2005

AbstractStaphylococcal infection of various prosthetic and internal fixation devices is a major complication associated with orthopaedic surgery. This study investigated the role of the host protein fibronectin in promoting adhesion of Staphylococcus aureus and Staphylococcus epidermidis to metallic surfaces representing materials used for orthopaedic devices. Pure human fibronectin was adsorbed in vitro onto coverslips (0.8 × 0.8 cm) of stainless steel, pure titanium, or titanium‐aluminum‐niobium alloy. In vitro bacterial adhesion was promoted more strongly by the metallic surfaces coated with fibronectin than by albumin‐coated controls for two strains of S. aureus and one strain of S. epidermidis. Furthermore, with the fibronectin‐coated coverslips, bacterial adhesion to titanium alloy was significantly greater than adhesion to stainless steel. Adhesion of the three staphylococcal strains was promoted more strongly by coverslips explanted from the subcutaneous space of guinea pigs and tested under similar conditions than by albumin‐coated controls. Incubation of either in vitro fibronectin‐coated or explanted metallic coverslips with anti‐fibronectin antibodies produced a significant decrease in staphylococcal adhesion. These results suggest that the presence of fibronectin on the surface of implanted metallic devices is an important determinant of colonization of orthopaedic biomaterials by staphylococi.
Histomorphometric analysis of the repair of a segmental diaphyseal defect with ceramic and titanium fibermetal implants: Effects of bone marrow
Authors: Wolff David , Goldberg Victor M. , Stevenson Sharon 
Published: February 2005

AbstractWe used a rat femoral diaphyseal defect/implant model to quantify the ingrowth of bone, cartilage, and fibrous connective tissue in a comparative study of woven sintered titanium fibermetal and porous hydroxyapatite/tricalcium phosphate ceramic implanted with and without the addition of syngeneic bone marrow cells. The patterns of tissue growth into the implants were analyzed with respect to time, type of implant, and the presence or absence of syngeneic marrow. Significantly more bone was found in ceramic implants than in fibermetal implants, with the addition of syngeneic marrow than without it, and at 4 months than at 2 months. Significantly more bone was found at both time periods in ceramic implants with bone marrow than in any other combination studied. We hypothesize that these findings resulted from interactions between the implanted material and its surroundings, specifically its ability to serve as a substratum for cell attachment, and cells in and around the defect, whether surgically implanted or arising from the soft‐tissue bed.
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

AbstractThe 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

AbstractWe 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

AbstractDemineralized 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractEight 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

AbstractIn 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

AbstractThis 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

AbstractGrowth 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.