Significance of interstitial bone ingrowth under load-bearing conditions: a comparison between solid and porous implant materials.

Interstitial bone ingrowth is extremely important for optimum fixation of implanted materials under load-bearing conditions. In this study, three types of biomaterial test piece were manufactured in solid and open-pore structures, and implanted into dog femoral condyles. Bone formation and remodelling were observed histologically and roentgenologically for 24 weeks thereafter. The study demonstrated that, 24 weeks after implantation, thick fibrous tissue surrounded by corticalized bone formed around both solid smooth-surfaced alumina and titanium implants. On the other hand, however, with an implant made of an artificial osteochondral composite material, thickening of ingrown trabeculae could be observed as early as 4 weeks. Bone ingrowth into the titanium fibre mesh was ambundant and increased with time after implantation. This interstitial bone ingrowth resulted in the complete integration of this implant and the viable host bone. Our findings suggest that interstitial bone ingrowth has great significance, even though new bone formation and remodelling follows Wolff's law after the completion of the bonding between the bone and implanted material under load-bearing conditions. The artificial osteochondral composite material could lead to complete integration of the implant and viable bone, suggesting that it is a promising material for joint replacements. Moreover, the tibial joint surface which bore against the polyvinyl alcohol hydrogel surface of this implant remained intact, which suggests that this composite is a very promising biomaterial for use in joint prostheses.

Synthetic osteochondral replacement of the femoral articular surface.

We have studied damage to the tibial articular surface after replacement of the femoral surface in dogs. We inserted pairs of implants made of alumina, titanium and polyvinyl alcohol (PVA) hydrogel on titanium fibre mesh into the femoral condyles. The two hard materials caused marked pathological changes in the articular cartilage and menisci, but the hydrogel composite replacement caused minimal damage. The composite osteochondral device became rapidly attached to host bone by ingrowth into the supporting mesh. We discuss the clinical implications of the possible use of this material in articular resurfacing and joint replacement.

[Effect of xiao chaihu decoction on experimental alkaline reflux gastritis in rats].

UNLABELLED: The effects of Xiao Chaihu Decoction (XCHD) on alkaline reflux gastritis and gastric secretion in rats was observed. RESULTS: (1) 5g/kg, 20 g/kg of XCHD might markedly inhibit the gastric lesion induced by gastric feeding of sodium taurocholate; (2) 5g/kg, 20g/kg of XCHD might significantly prevent the gastric lesion induced by gastric feeding of intestinal juice; (3) On chronic reflux gastritis model induced by spring-expanded pylorus after 4 or 8 weeks, 4g/kg-20g/kg of XCHD might lower the incidence of gastritis, and reduce the intragastric bile acid; (4) 5g/kg and 20g/kg of XCHD might significantly inhibit the secretion of gastric juice and acid as well as the activity of pepsin. The results suggested that XCHD had anti-reflux gastritis effect.

[Effects of 3 Chinese medical prescriptions on alkaline reflux gastritis in rats].

The experimental alkaline reflux gastritis in rats was established after 9 weeks of anastomosis between stomach and jejunum. The experiment shows that xiangsha liujunzi decoction, xiaochaihu decoction and dahuang gancao decoction all help to inhibit edema, hyperamia and extravasted blood, as well as depress inflammatory infiltration and hyperplasia. The number of intestinal metaplasia in the group treated with xiangsha liujunzi decoction is decreased. All the three prescriptions are not able to lower the contents of bile acid in the stomach.

Bone remodeling around implanted ceramics.

Bone formation and remodeling around implanted materials is influenced by the kind of material, its surface properties, and the anatomical site of implantation. In this study, differences in bone formation around three kinds of ceramics and the importance of the implant location in the tibia were investigated. In the first experiment, we placed three kinds of ceramics--alumina, zirconia and hydroxyapatite (HA)--into the medullary cavity of rabbit tibiae and examined histologically the time-dependent formation of bone around the materials for up to 24 weeks postoperatively. We found that bone formation depends on whether or not the materials are in direct contact with the endosteum. In the second experiment, the same three ceramic materials were implanted transcortically into rabbit tibiae. The bone formed around the implants was most abundant in regions adjacent to the periosteum, followed by the endosteum and the marrow cavity in the approximate ratios of 70%, 40%, and 10%, respectively. In these two experiments, the difference between bioactive and bioinert ceramics could be seen in the interface between the implanted material and the bone. It can be concluded that bone formation around these materials is related to the osteoconductivity of the materials and to the osteogenic capacity of the tissues.

Influence of various structure treatments on histological fixation of titanium implants.

In this study, three types of titanium test pieces were manufactured with different surfaces and implanted into dog femoral condyles, and tissue response was assessed histologically and radiographically for 24 weeks thereafter. The study confirmed that thickening of lamellar bone could be observed around titanium plasma spray-coated titanium alloy implants 24 weeks after implantation, whereas thick fibrous tissue surrounded by corticalized bone formed around those made of smooth-sided titanium alloy. With an implant made of an artificial osteochondral composite material, thickening of ingrown trabeculae could be observed as early as 4 weeks, and abundant bone growth into the titanium fiber mesh continued to increased with time. This bone ingrowth resulted in the complete integration of this composite device implant and the host bone. Our findings suggest that cell response to the various implants is quite different, even though the implants were made of the same kind of material. The implants with the open-pore structure has great significance in the ideal fixation between the implants and the viable bone.

Histologic comparison of tibial articular surfaces against rigid materials and artificial articular cartilage.

After endoprosthetic replacement of the femoral head, marked pathologic changes of the acetabulum, such as penetration and ulceration, often occur. These changes are caused by the rigid material surface properties of the prosthesis and the lack of damping effects. In this study, we compared the time-dependent changes of tibial articular surfaces with three kinds of femoral implant under loading conditions in dogs. Marked pathologic changes of the menisci and tibial articular cartilage were observed from 8 weeks after implantation with hard material implants, whereas the tibial joint surface against an artificial articular cartilage was still intact 24 weeks postoperatively. These results showed clearly that marked pathologic changes of the articular cartilage against rigid materials occurred and were caused by the surface properties of the counterfaces and high friction coefficients of ceramic and metal materials used.

Bone formation and remodeling around implanted materials under load-bearing conditions.

Bone formation and remodeling around implanted materials are influenced by the load-bearing conditions. In this study, three types of material were implanted into dog femoral condyles and bone formation and remodeling were observed for 24 weeks thereafter. Even thickening of lamellar bone was observed around bead-coated alumina implants, whereas thick fibrous tissue surrounded by corticalized bone formed around those made of smooth alumina. With an implant made of an artificial osteo-chondral composite material, abundant bone ingrowth into the titanium fibers was observed 8 weeks after the operation and this ingrowth resulted in firm attachment of this composite material to the host bone site. The tibial joint surface against the polyvinyl alcohol (PVA)-hydrogel articular surface of this implant remained intact, which suggests this artificial osteochondral composite material is a very promising joint prosthetic material.