Biomaterial scaffolds in cartilage-subchondral bone defects influencing the repair of autologous articular cartilage transplants.

The repair of articular cartilage typically involves the repair of cartilage-subchondral bone tissue defects. Although various bioactive materials have been used to repair bone defects, how these bioactive materials in subchondral bone defects influence the repair of autologous cartilage transplant remains unclear. The aim of this study was to investigate the effects of different subchondral biomaterial scaffolds on the repair of autologous cartilage transplant in a sheep model. Cylindrical cartilage-subchondral bone defects were created in the right femoral knee joint of each sheep. The subchondral bone defects were implanted with hydroxyapatite-ß-tricalcium phosphate (HA-TCP), poly lactic-glycolic acid (PLGA)-HA-TCP dual-layered composite scaffolds (PLGA/HA-TCP scaffolds), or autologous bone chips. The autologous cartilage layer was placed on top of the subchondral materials. After 3 months, the effect of different subchondral scaffolds on the repair of autologous cartilage transplant was systematically studied by investigating the mechanical strength, structural integration, and histological responses. The results showed that the transplanted cartilage layer supported by HA-TCP scaffolds had better structural integration and higher mechanical strength than that supported by PLGA/HA-TCP scaffolds. Furthermore, HA-TCP-supported cartilage showed higher expression of acid mucosubstances and glycol-amino-glycan contents than that supported by PLGA/HA-TCP scaffolds. Our results suggested that the physicochemical properties, including the inherent mechanical strength and material chemistry of the scaffolds, play important roles in influencing the repair of autologous cartilage transplants. The study may provide useful information for the design and selection of proper subchondral biomaterials to support the repair of both subchondral bone and cartilage defects.

Reliability of clinical measurement for assessing spinal fusion: an experimental sheep study.

STUDY DESIGN: A sheep study designed to compare the accuracy of static radiographs, dynamic radiographs, and computed tomographic (CT) scans for the assessment of thoracolumbar facet joint fusion as determined by micro-CT scanning. OBJECTIVE: To determine the accuracy and reliability of conventional imaging techniques in identifying the status of thoracolumbar (T13-L1) facet joint fusion in a sheep model. SUMMARY OF BACKGROUND DATA: Plain radiographs are commonly used to determine the integrity of surgical arthrodesis of the thoracolumbar spine. Many previous studies of fusion success have relied solely on postoperative assessment of plain radiographs, a technique lacking sensitivity for pseudarthrosis. CT may be a more reliable technique, but is less well characterized. METHODS: Eleven adult sheep were randomized to either attempted arthrodesis using autogenous bone graft and internal fixation (n = 3) or intentional pseudarthrosis (IP) using oxidized cellulose and internal fixation (n = 8). After 6 months, facet joint fusion was assessed by independent observers, using (1) plain static radiography alone, (2) additional dynamic radiographs, and (3) additional reconstructed spiral CT imaging. These assessments were correlated with high-resolution micro-CT imaging to predict the utility of the conventional imaging techniques in the estimation of fusion success. RESULTS: The capacity of plain radiography alone to correctly predict fusion or pseudarthrosis was 43% and was not improved using plain radiography and dynamic radiography with also a 43% accuracy. Adding assessment by reformatted CT imaging to the plain radiography techniques increased the capacity to predict fusion outcome to 86% correctly. The sensitivity, specificity, and accuracy of static radiography were 0.33, 0.55, and 0.43, respectively, those of dynamic radiography were 0.46, 0.40, and 0.43, respectively, and those of radiography plus CT were 0.88, 0.85, and 0.86, respectively. CONCLUSION: CT-based evaluation correlated most closely with high-resolution micro-CT imaging. Neither plain static nor dynamic radiographs were able to predict fusion outcome accurately.

Transplanted abdominal granulation tissue induced bone formation--an in vivo study in sheep.

Many wounds to both soft and hard tissues heal via the formation of a granulation tissue bed. This bed is supportive of neoangiogenesis and releases proangiogenic, migratory, and proliferative growth factors and cytokines. In this study granulation tissue was grown on an intraperitoneal implant (4 mm diameter, 20 mm length) in a sheep. After 2 weeks, this implant was removed and transplanted into a femoral bone defect (4 mm diameter, 20 mm length). The sheep were sacrificed after 3 months, and the implant site examined using micro-CT and histology. A bone plaque formed adjacent to the implant, only in the presence of the peritoneal granulation tissue. This suggests that the formation of granulation tissue is a relatively conserved response at various locations in the body and its transplantation from one location to another can be used to induce tissue healing. This technique may prove useful as a method of improving physiological response to biomaterials.

Nanoceramics for blood-borne virus removal.

The development of nanoscience and nanotechnology in the field of ceramics has brought new opportunities for the development of virus-removal techniques. A number of nanoceramics, including nanostructured alumina, titania and zirconia, have been introduced for the applications in virus removal or separation. Filtration or adsorption of viruses, and thus the removal of viruses through nanoceramics, such as nanoporous/mesoporous ceramic membranes, ceramic nanofibers and ceramic nanoparticles, will make it possible to produce an efficient system for virus removal from blood and one with excellent chemical/thermal stability. Currently, nanoceramic membranes and filters based on sol-gel alumina membranes and NanoCeram nanofiber filters have been commercialized and applied to remove viruses from the blood. Nevertheless, filtration using nanoporous filters is limited to the removal of only free viruses in the bloodstream.

Cardiovascular changes after pulmonary embolism from injecting calcium phosphate cement.

Concerns have been raised that the use of calcium phosphate (CaP) cements for the augmentation of fractured, osteoporotic bones may aggravate cardiovascular deterioration in the event of pulmonary cement embolism by stimulating coagulation. The aim of the present study was therefore to investigate the cardiovascular changes after pulmonary embolism of CaP cement using an animal model. In 14 sheep, 2.0 mL CaP or polymethylmethacrylate cement were injected intravenously. Cardiovascular parameters and antithrombin levels were monitored until 60 min postinjection. Postmortem, lungs were subjected to CT scanning, and 3D reconstruction of the cement was performed. Intravenous injection of CaP cement resulted in a more severe increase in pulmonary arterial pressure and decrease in arterial blood pressure. Disintegration of the CaP cement seemed to be the reason for the more severe reaction. There was no evidence of thromboembolism. Disintegration of CaP cement in circulating blood does not only compromise the mechanical properties, but also represents a risk of cardiovascular complications. Reliable cohesion of CaP cements in an aqueous environment is essential for clinical applications such as osteoporotic bone augmentation.

Effects of increased ambient temperature on the development of in vitro derived bovine zygotes.

In this study, presumptive bovine zygotes were subjected to two consecutive 24-h cycles of heat treatment during the first 48 h (Experiment I) of in vitro culture (IVC) or 24h of heat treatment during the fourth day of IVC (Experiment II). In Experiment I, the percentage of heat treatment zygotes that developed to > or =8-cell stage embryos after 72 h IVC was 2.0% (n = 459) compared with 28.4% (n = 458) for the control zygotes (P<0.001). The subsequent yield of morulae or blastocysts after 144 h IVC for the heat treatment and control groups was 0.9% (n = 457) and 12.3% (n = 456) (P<0.001), respectively. These results demonstrate that heat treatment during the first 48 h of IVC significantly impaired embryo development. In Experiment II, the percentage of zygotes that developed into morulae and blastocysts following heat treatment during the fourth day of IVC was 4.5% (n = 468) compared to 10.5% (n = 456) for the control group (P<0.001). This study has demonstrated that in vitro heat stress during the critical stage of early embryo development significantly increases the incidence of early embryonic mortality.