Eiji Tsuji

Comparative bone growth behavior in granules of bioceramic materials of various sizes

Various bioceramic materials were implanted into 6-mm-diameter holes made in the femoral condyles of mature Japanese white rabbits using different-sized granules to find an optimal material and granule diameter for use as a bone graft. Bioceramics include a bioinert ceramic (Alumina), surface-bioactive ceramics [hydroxyapatite (HAp) and Bioglass(R)], and resorbable bioactive ceramics [alphatricalcium phosphate (alpha-TCP), beta-TCP, tetracalcium phosphate (TeCP), Te. DCPD, Te. DCPA, and low-crystalline HAp]. Granule sizes were 100-300, 10, and 1-3 microm. Bone growth behavior varied with the kind of bioceramic and the size used. For surface-bioactive ceramics, 45S5 Bioglass(R) led to more rapid bone proliferation than synthetic HAp. In resorbable bioactive ceramics, the order of resorption was: low-crystalline HAp and OCP > TeCP, Te DCPD, Te DCPA > alpha-TCP, beta-TCP. In terms of biocompatibility, alpha-TCP was better than beta-TCP.

Particulate bioglass compared with hydroxyapatite as a bone graft substitute

Bioactive ceramics, notably hydroxyapatite, have been used clinically in various situations in which bone augmentation and restoration are required. Particulate material has been used either alone or in conjunction with freeze dried or autologous bone, with variable clinical success. In this study a bioactive glass, 45S5 Bioglass, has been compared with hydroxyapatite in an animal model to discover whether the 2 major disadvantages of hydroxyapatite may be overcome. These are the difficulty of placing and retaining the particulate in the defect and the length of time needed before full bony restoration is achieved. Bioglass is shown to be easy to manipulate and hemostatic and allows full restoration of bone in 2 weeks, rather than the 12 weeks needed for the particulate hydroxyapatite to produce a comparable response. The Bioglass particulate is used up in the process, and any problems that may be associated with the production of a composite of bone and biomaterial are avoided in the fully restored bone. In any procedure that requires bony augmentation, this rapid response to Bioglass is expected to provide a clinical advantage.

Quantitative comparison of bone growth behavior in granules of Bioglass®, A-W glass-ceramic, and hydroxyapatite

The hypothesis that bioactive glass particulate increases the rate of bone proliferation over that of synthetic hydroxyapatite and bioactive glass-ceramic was tested in these experiments. Three types of bioactive particles-45S5 Bioglass(R), synthetic hydroxyapatite, and A-W glass-ceramic-were implanted in 6-mm-diameter holes drilled in the femoral condyles of mature rabbits. Bone growth rate was measured using an image processor. 45S5 Bioglass(R) produced bone more rapidly than either A-W glass-ceramic or hydroxyapatite. At the later time periods, 45S5 Bioglass(R) was resorbed more quickly than A-W glass-ceramic. Synthetic hydroxyapatite was not resorbed at all. Backscattered electron imaging suggested that the resorption process occurred by solution-mediated dissolution, which produced chemical changes in the enclosed particulate. It was concluded that the rate of bone growth correlates with the rate of dissolution of silica as the particles resorb.

Bone Growth into Spaces Between 45S5 Bioglass Granules

ABSTRACT Granules of Bioglass® 100–300 μm in diameter were implanted into 6mm diameter holes made in the femoral condyles of mature rabbits. As a control, HA granules of similar size were used. After 12 days new bone had grown into the defect to a depth of 1500 μm, equivalent to 10 layers of granules. Of these layers three or four were completely enclosed in new bone. By three weeks the whole defect was filled (to 3,000 μm) and approximately 10 layers of granules were completely enclosed. At five weeks this bone had continued to densify. In contrast only the outer layer of HA granules was surrounded by bone at two weeks although bone had infiltrated to the third or fourth layer. By three weeks bone had reached 1000 μm but even after six weeks had not reached, the center, being only 2500μm in thickness. In conclusion, the speed of bone growth around Bioglass® particles was faster and the new bone was denser than that associated with hydroxyapatite granules.

Needs of Bioceramics to Longevity of Total Joint Arthroplasty

Wear on alumina / UHMWPE-THP decreased by 25-30% of that on met al / UHMWPE in hip simulator test and clinical results. Wear on THP of alum ina / alumina was near zero in hip simulator test. In knee simulator test, UHMWPE wear against lumina decreased to 1/10 of that against metal. Clinically we have no revision case due to PE we ar problems for 23 years. In retrieved cases, UHMWPE surface against alumina was very s mooth. On UHMWPE surface against metal, many fibrils and scratches were found. In IBBC loosening in acetabulum occurred in 2.5% in 268 joints in only early cases at 16 to 14 years after THA. Only one joint was revised. At revision THA with massive bone defect, HA granules were filled. Socket migrations in two joints and partial spaces in two joints occurred in total 40 joints at 17 to 5 years. Bioceramics was found to be indispensable in enduring total joint arthroplasty . Introduction In order to keep the longevity of total joint arthroplasty, extrem ely low wear bearing materials and maintaining adequate fixability to the bone forever are desired. In our experimental and long term clinical experiences, it has been found that bioceramics, including bioinnert and bioactive ceramics, have been playing a maj or p rt in enduring total joint arthroplasty. The production of particulate wear debris from implant materials a nd subsequent osteolysis has been recognized as the major cause of long term failure in tot al hip replacement. The basic strategy to address the problem of osteolysis should be to reduce the number of polyethylene particles generated by improving the materials at the articulating count erfaces. The use of a ceramic femoral head has been advocated especially in young active patients because it produces less polyethylene wear compared with a conventional metal femoral head. However, an attempt to eliminate the use of polyethylene has been made through the use of metal-on-metal and ceramic-on-ceramic articulations. In 1970, to increase the wear resistance of polyethylene, wear te sts w re performed on RCH 1000 [ultrahigh molecular weight polyethylene (UHMWPE), molecular we ight, 106] irradiated at several levels of high-dose gamma radiation emitted by 60Co. The wear ra te was smallest at 100 Mrad. Sockets cross-linked by gamma radiation at 100 Mrad were used clinically from 1971 to 1978. We also experimentally confirmed that UHMWPE (molecular weig ht, 6 x 106) showed less wear in an alumina-on-UHMWPE combination than in the metal-on-UHMWPE combina tion. In 1977, we began to use 28 mm alumina balls. In our clinical experience, it was found that the thicker the poly ethylene socket, the lower the wear rate. To use a thicker UHMWPE sockets, the femoral head size was decreased with time: 26 mm alumina femoral heads were used from 1989 to 1994, 22 mm alumina femoral h eads were used from 1994 to 1995, and 22 mm zirconia femoral heads were used from 1995 to 1996. S ince 1996, Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 735-754 doi:10.4028/www.scientific.net/KEM.240-242.735