Background

Total ankle arthrpoplasty (TAA) was performed frequently for ankle deformity caused by rheumatoid arthritis (RA) and osteoarthritis (OA). TAA has some advantages over ankle arthrodesis in range of motion (ROM). However, loosening and sinking of implant have been reported with several prostheses, especially constrained designs. Recently, we have performed mobile bearing TAA and report short term results of this prosthesis followed average 3 years.

Introduction: Fibroin sponge is purified silk protein from which high-strength gel sponge can be produced. The purified fibroin sponge causes no immune response. This study evaluates unique performances of the fibroin sponge for articular-cartilage regeneration, and mechanical properties of regenerated cartilage were also measured.

Methods: Refined silk yarn was dissolved in 9M lithium bromide aqueous solutions, and was frozen in −20& #8451 freezer for 12 hours. Hydrogel sponge was formed under the room temperature. Articular cartilage slices were taken from the proximal humerus, distal femur and proximal tibia of 4-week-old Japanese white rabbits. The cartilage slices cut into small pieces and were digested with 0.25% trypsin in DMEM containing antibiotics for 30 min at 37& #8451. After rinsing with Tyrode’s balanced solution and centrifuging at 180 G for 5 min, the chondrocytes were isolated with 0.25% collagenase for 8 h at 37& #8451. These cells were harvested and inoculated into the fibroin sponge. The constructs of the chondrocytes and the fibroin sponge were cultured in DMEM containing 10& #65285 FCS and 50mL L-ascorbate for 4weeks. Indentation test and dynamic visco-elastic measurement were carried out for these constructs.

Results and discussion: Cell density of the inoculated chondrocytes was increased to about five times as much as initial volume. This regenerated tissue was intensely stained with safranin-O fast green and showed a meta-chromatic reaction. This also stained positively with immunostain for type & #8545 collagen, but negatively with immunostain for type & #8544 collagen. Mechanical tests showed that time constants of compressive creep and E’ values were increased with cultivation days, and the peak value and frequency of tan& #948 shifted to a lower amount. The change in dynamic visco-elastic properties of the regenerated cartilage is caused by synthesis of extracellular matrix.

Introduction: Several types of “ Total Joint Regeneration System” were proposed where wide defect of cartilage expected to be regenerated under proper mechanical environment. Several types of therapeutic equipments for the Total Joint Regeneration System were designed and animal trial for the system was performed. Fundamental experiment evaluating cartilage generation under continuous sliding motion is also reported.

Material and methods: Three Japanese white rabbits (male, 12~15 weeks-old) weighing 3.0& #13199; and one beagle dog (male) weighing 15& #13199; were used for the trial operation for the Total Joint Regeneration System. A large full-thickness defect of the articular cartilage was made on both knees. And Internal-support type device was fixed to the knee of one side. The device is consisting of 2 parts (the screw and the T-bar). The screw was fixed in tibia from the fore part of ACL attachment to anterior part of the tibia. The rod of the T-bar was inserted into the inner hole of the screw. The upper part of the T-bar hold the femoral intercondyle and keep the regenerated portion in non-weight-bearing condition. Regeneration at the osteochondral defect was evaluated at 4 weeks postoperatively. [Cartilage generation by continuous sliding motion] A coccygeal vertebra of F344 rats (7weeks-old) was osteot-omized, and the distal part of the vertebrae was moved continuously in sliding motion using mobile external fixation.

Results and discussion: Walking conditions were comparatively good in all animals. Macroscopic observation shows better appearance of defected area in the supported side, however the apparent histological difference between control side and internal-support side could not be recognized in the rabbits cases because of inappropriate fitting of the devices. Hyaline cartilage tissue with better metachromatic matrix with safranin-O staining was observed on the supported side of dog knee. Result of fundamental experiment also showed the importance of setting mechanical environment where hyaline cartilage with layer structure similar to normal articular cartilage was produced by controlled sliding motion. We are now improving the design of the Total Joint Regeneration System refering to those results.