ISSN:0736-0266    

DOI:10.1002/jor.1100170102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

ISSN:0736-0266    

DOI:10.1002/jor.1100170103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

AbstractSmall particles of ultrahigh molecular weight polyethylene stimulate formation of foreign‐body granulomas and bone resorption. Bone formation may also be affected by wear debris. To determine if wear debris directly affects osteoblasts, we characterized a commercial preparation of ultrahigh molecular weight polyethylene (GUR4150) particles and examined their effect on MG63 osteoblast‐like cells. In aliquots of the culture medium containing ultrahigh molecular weight polyethylene, 79% of the particles were less than 1 μm in diameter, indicating that the cells were exposed to particles of less than 1 μm. MG63 cell response to the particles was measured by assaying cell number. [3H]thymidine incorporation, alkaline phosphatase specific activity, osteocalcin production, [35S]sulfate incorporation, and production of prostaglandin E2and transforming growth factor‐β. Cell number and [3H]thymidine incorporation were increased in a dose‐dependent manner. Alkaline phosphatase specific activity, a marker of cell differentiation for the cultures, was significantly decreased, but osteocalcin production was not affected. [35S]sulfate incorporation, a measure of extracellular matrix production, was reduced. Prostaglandin E2release was increased, but transforming growth factor‐β production was decreased in a dose‐dependent manner. This shows that ultrahigh molecular weight polyethylene particles affect MG63 proliferation, differentiation, extracellular matrix synthesis, and local factor production. These effects were direct and dose dependent. The findings suggest that ultrahigh molecular weight polyethylene wear debris particles with an average size of approximately 1 μm may inhibit bone formation by inhibiting cell differentiation and reducing transforming growth factor‐β production and matrix synthesis. In addition, increases in prostaglandin E2production may not only affect osteoblasts by an autocrine pathway but may also stimulate the proliferation and activation of cells in the monocytic lineage. These changes favor decreased bone formation and increased bone resorption as

ISSN:0736-0266    

DOI:10.1002/jor.1100170104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

AbstractThe anterior cruciate ligament is a complex tissue composed of structural proteins, proteoglycans, and cells. The histology of the human anterior cruciate ligament is characterized by the specific distribution and density of the fibroblast phenotype as well as by the unique organization of the structural proteins. A notable finding of this study was the identification of three histologically different zones along the anteromedial bundle as it coursed from the femoral to the tibial attachment. Two of the zones, the fusiform and ovoid, were located in the proximal one‐quarter of the bundle; the third zone, the spheroid, occupied the distal three quarters of the bundle fascicles. The fusiform cell zone was characterized by a high number density of longitudinally oriented cells with a fusiform‐shaped nucleus, longitudinal blood vessels, and high crimp length. The cytoplasm of the cells in this zone appeared to be intimately attached to the extracellular collagen and followed the crimp waveform of the fibers. Fusiform cells were noted to stain positively for the α‐smooth muscle actin isoform in this region, particularly at areas of crimp disruption. The ovoid cell zone was characterized by a high number density of cells with an ovoid‐shaped nucleus, longitudinal vessels, and a high crimp length. In this zone as well, the cytoplasm of the cells appeared to follow the waveform of the adjacent collagen. Ovoid cells were noted to stain positively for the α‐smooth muscle actin isoform in this region. The spheroid cell zone was characterized by a low density of spheroid cells, few blood vessels, and short crimp length. Cells were noted within and among fascicles, as well as within lacunae. In selected areas, as many as 50% of the cells in this region stained positively for the α‐smooth muscle actin isoform. This is also the first report of cells expressing the α‐smooth muscle actin isoform in the intact human anterior cruciate ligament. This specific type of contractile actin, initially identified only in smooth‐muscle cells, pericytes, and myofibroblasts, was seen in cells with various morphologies and predominantly in cells located at areas of crimp disruption. Further work is necessary to elucidate the role of the various fibroblast phenotypes in the maintenance of the human anterio

ISSN:0736-0266    

DOI:10.1002/jor.1100170105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

AbstractThe central third of the patellar tendon is commonly used to reconstruct the injured anterior cruciate ligament. Some studies have noted changes in joint tissues following this procedure. It has been postulated that these changes may be associated with increased stress on the remaining tendon following harvest of the graft. In our study, the central third of the patellar tendon was excised in three groups of rabbits. The central tendon defects in two of the three groups were fitted with different augmentation devices to augment the host tendon during the healing process. All rabbits followed a daily treadmill exercise regimen for 12 weeks following the operation. Biomechanical testing of the tendon revealed that in nonaugmented tendons the cross‐sectional area and the length of the patellar tendon significantly increased 112 and 16%, respectively. There was histological evidence of host‐tendon remodeling throughout the cross section and extensive fibrosis in the infrapatellar fat pad. Augmentation of the tendon significantly reduced these changes, with the least change noted in the group with the greatest augmentation. The rabbits with augmentation devices retained tendon dimensions similar to those of the contralateral intact tendon, and tendon remodeling occurred only in the defect area. The rabbits with augmentation devices exhibited little to no fibrosis of the fat pad. Structural properties of augmented and nonaugmented tendons were similar despite the size differences, indicating higher tissue quality in the augmented tendons. This study suggested that complications of the knee joint (i.e., tendon proliferation and fat pad fibrosis) noted after anterior cruciate‐ligament reconstruction with the autogenous patellar tendon may be limited by the implantation of an augmentation d

ISSN:0736-0266    

DOI:10.1002/jor.1100170106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

AbstractGene therapy is a technique that may offer advantages over current methods of cytokine delivery to ligaments. To determine if implanted genes could be expressed in normal and injured knee ligaments, the medial collateral ligament and anterior cruciate ligament were studied in 18 rabbits. A retroviralex vivotechnique using allograft medial collateral ligament and anterior cruciate ligament fibroblasts and an adenoviralin vivotechnique were compared as methods for delivering the LacZ marker gene to knee ligaments. Bilateral knee surgeries were performed, and the rabbits were equally divided into three groups. Group 1 received the retrovirus and the medial collateral ligament was ruptured, Group 2 received the adenovirus and the medial collateral ligament was ruptured, and Group 3 received the adenovirus and the medial collateral ligament was not injured. The anterior cruciate ligament was not injured in any group. The medial collateral and anterior cruciate ligaments of the right knees received 106allografted, transduced ligament fibroblasts or 109adenovirus particles, whereas the ligaments of the left knee received a similar volume of saline solution only. Equal numbers of rabbits were killed at 10 days. 3 weeks, and 6 weeks following the procedure. Ligament samples were stained with X‐gal to detect the expression of the LacZ gene product, β‐galactosidase. LacZ gene expression was evident in ruptured and uninjured medial collateral ligaments as well as in the anterior cruciate ligament. The expression lasted between 10 days and 3 weeks in the medial collateral and anterior cruciate ligaments with use of the retrovirus and between 3 and 6 weeks in the medial collateral ligament and at least 6 weeks in the anterior cruciate ligament with the adenovirus. The length of gene expression in the ruptured and uninjured medial collateral ligaments did not differ. These preliminary studies indicate that gene transfer to normal and injured knee ligaments is poss

ISSN:0736-0266    

DOI:10.1002/jor.1100170107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

AbstractThis study reports that recombinant adenovirus‐mediated human bone morphogenetic protein‐2 gene transfer can induce mesenchymal progenitor cell differentiation and bone formation. The recombinant adenovirus with the human bone morphogenetic protein‐2 gene was constructed, and mature human bone morphogenetic protein‐2 expression mediated by adenovirus gene transfer was detected by specific antibody. Under adenovirus‐mediated bone morphogenetic‐protein gene transfer, mesenchymal progenitor cell line C3H/10T 1/2 showed cell proliferation dependent on adenovirus bone morphogenetic‐protein dose. The C3H/10T 1/2 cells transduced by adenovirus bone morphogenetic protein also exhibited differentiation to osteoblast phenotype, which indicates alkaline phosphatase activity. Injection of the C3H/10T 1/2 cells into the thigh muscles of nude mice led to ossicle development detectable on radiographs. Histological analysis indicated that the new ossicles that developed in the thigh muscles of the mice had different osseous components including bone trabeculae, bone marrow, and chondrified tissue. The results of this study demonstrate the potential for gene therapy by adenovirus‐mediated bone morphogenetic‐prot

ISSN:0736-0266    

DOI:10.1002/jor.1100170108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

AbstractCytokines that stimulate bone resorption are produced by cells found in bone marrow. However, marrow cells produce multiple factors, some of which may be inhibitors of osteoclast differentiation or activity. Thus, it is not possible to predicta prioriwhether the mixture of factors produced by marrow cells will have a net stimulatory or inhibitory effect on bone resorption. In this study, we showed that the net effect of whole marrow is to inhibit osteoclast activity induced by parathyroid hormone. Fractionation of the marrow revealed that the inhibitory activity was in the marrow fluid. However, conditioned media obtained from marrow cell cultures also inhibited osteoclast activity. Thus, it is likely that the inhibitory factors are producedin vivoby cells residing in the marrow. These inhibitory factors may represent a physiological regulatory process that plays an important role in maintaining the balance between bone resorption and formation. Because we have previously shown that interleukin‐6 is one of the cytokines that parathyroid hormone induces in osteoblastic cells to stimulate osteoclast activity, one potential mechanism by which the marrow‐derived inhibitory factors might act is by preventing this production of interleukin‐6. However, we found that the marrow cell‐conditioned media do not inhibit the production or activity of interleukin‐6. Thus, the inhibitory factors appear to block osteoclast activity through a mechanism that does not involve interleukin‐6. Taken together, these results demonstrate the importance of factors that inhibit bone resorption and emphasize that the presence of cytokines that stimulate bone resorption in conditions such as osteoporosis and orthopaedic implant loosening should be interpreted with caution unless evidence exists demonstrating their functional

ISSN:0736-0266    

DOI:10.1002/jor.1100170109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

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

ISSN:0736-0266    

DOI:10.1002/jor.1100170110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY

摘要:

AbstractThe ability to mechanically reinforce an osteoporotic vertebral body could impede spinal compression fracture and the associated pain and complications. Previous studies have shown that reinforcement of fractured vertebrae with conventional acrylic cement can relieve symptoms and avoid further collapse. In this study, we explored the use of a carbonated apatite cement combined with a minimally invasive injection technique to improve the compressive mechanical properties of cadaveric vertebral bodies. After establishing the biomechanical characteristics of cement formulations intended to have appropriate viscosities, we evaluated the infiltration of the cements into thoracic vertebral bodies using a combined suction‐injection technique. The energy‐absorption capabilities of the reinforced vertebral bodies were then measured during axial compressive tests and compared with those of nonreinforced vertebrae. The ultimate compressive strength of the cement formulations averaged from 11.6 to 17.7 MPa, depending on curing conditions. The suction‐injection technique allowed from one‐half to two‐thirds of each vertebral body to be infiltrated with cement. Energy absorption was significantly higher (p<0.05) between 25 and 70% collapse of the vertebral body in the specimens that received the apatite injection as compared with the controls. These results suggest that osteoporotic vertebral‐body augmentation with the injection of apatite cement could prevent further collapse after initial failure has occurred. The osteoconductive nature of the cement and its ability to be remodeled by bone, together with its compressive strength, which is higher than that of cancellous bone, could provide better clinical results than those of current treatments with acr

ISSN:0736-0266    

DOI:10.1002/jor.1100170111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1999

数据来源: WILEY