Wear performance and debris-size distribution of vitamin E (DL-a tocopherol, VE)-added ultrahigh molecular weight polyethylene (UHMWPE) was evaluated using a knee-simulator test. VE was mixed with GUR 1050 UHMWPE powder at 0.3 wt%, and the tibial components of the knee joint were made by direct compression molding. The VE-added UHMWPE showed consistently lower wear volume throughout the test. ß

Accelerated ageing was conducted on UHMWPE with and without vitamin E (D, L-α tocopherol, VE). Wear performance was investigated using a knee simulator and wear debris was analysed. Aged UHMWPE with VE showed significantly lower wear volume than that of aged virgin UHMWPE and showed approximately similar wear volume as non-aged virgin UHMWPE. There were no significant differences among the materials as far as shape factor of the debris is concerned.

ABSTRACT. Poly-l-lactic acid (PLLA) has been clinically used as a bioabsorbable material and attains a piezoelectric charge upon molecular orientation by the application of a shear force to the C-axis of the crystal line region. Previous studies showed that implanted drawn PLLA films or rods accelerate the ossification due to piezoelectric effect. In this study, we originally designed helically-twisted PLLA fiber to produce piezoelectricity in bioabsorbable suture upon tensile stress. The piezoelectricity of the helical PLLA fibers was evaluated using a lock-in amplifier system in vitro. The ossification induced by helical PLLA fibers was examined by implanting them in the rat patellar ligament supporting a physiological tensile load. We observed that 57° and 45° twisted PLLA fibers generated a higher piezoelectric potential than did 27° twisted fibers. The animal experiment showed that the formation of osseous tissue around helical PLLA fibers was more significant than around non-helical control fibers at 4 weeks after their implantation. These results suggest that helical PLLA fiber may be useful for the surgical suture or artificial ligament, which connects to the bone. KEW WORDS: animal model, helical conformation, ossification, piezoelectricity, poly-l-lactic acid.doi: 10.1292/jvms.12-0323; J. Vet. Med. Sci. 75(9): 1187-1192, 2013 Ligament injury, such as anterior cruciate ligament rupture, is a common cause of lameness in small animal practice [6,15]. Various types of artificial ligaments including bioabsorbable material have been studied to reconstruct the injured ligament [3,27,31]. It has been suggested that early osteointegration of the grafted artificial ligament to the bone is important to improve the ligament function and durability [39].Poly-l-lactic acid (PLLA) is well known as a bioabsorbable material and has been clinically used as bioabsorbable mini-plate, screw and pin [2,13,14,30,33]. On the other hand, PLLA is known as a piezoelectric material. Fukada reported that an external mechanical stress to a drawn PLLA film gives rise to electrical polarization [10], and this piezoelectric effect is ascribed to the change in the microscopic orientation of crystals with a fundamentally asymmetrical structure [5,10,22,23]. Animal experiments showed that the piezoelectricity of drawn PLLA films and rods accelerated callus formation on bone [10,22,35]. Shimono et al. prepared three types of PLLA piezoelectric films with different oriented directions (0°, 45° or 90° to the drawing direction) and implanted them on the periosteum of the rabbit tibia [35]. These drawn PLLA films promoted ossification to a greater extent than undrawn PLLA films, and the effect of drawn PLLA films in promoting ossification was greatest when a shearing stress was applied at 45° to the axis of orientation. Ikada et al. prepared drawn PLLA rods with different draw ratios and implanted these rods intramedullary in the osteotomized tibia of cats [22]. Fracture healing was clearly promoted with increased callus formation as the draw...

No abstract