Bonding of alkali- and heat-treated tantalum implants to bone

Alkali- and heat-treated tantalum (Ta) has been shown to bond to bone. The purpose of this study was to investigate the effects of chemical treatments on the bone-bonding ability of tantalum implants in rabbit tibiae, Miyazak i et al, reported in vitro that alkali- and heat-treated tantalum had an ap atite forming ability in an acellular simulated body fluid (SBF). In this s tudy, smooth-surfaced rectangular plates (15 x 10 x 2 mm) of pure tantalum and treated tantalum were prepared. The plates were implanted transcortical ly into the proximal metaphyses of bilateral rabbit tibiae, alkali- and hea t-treated plates for one limb and untreated plates for the contralateral li mb, which served as a paired control. Bone bonding at the bone/implant inte rface was evaluated by tensile testing and undecalcified histological exami nation, at 8 and 16 weeks after implantation. The treated implants showed w eak bonding to bone at 8 weeks, and exhibited significantly higher tensile failure loads compared with untreated tantalum implants at 16 weeks. The un treated implants showed almost no bonding, even at 16 weeks. Histological e xamination by Giemsa surface staining, contact microradiography (CMR), and scanning electron microscopy (SEM) revealed that treated tantalum implants bonded directly to bone tissue. In contrast, the untreated tantalum implant s had a intervening fibrous tissue layer between the bone and the plate and did not bond to bone at 8 and 16 weeks. It is clear from these results tha t alkali and heat treatment induce the bone-bonding ability of tantalum, Th is new bioactive tantalum should be an effective material for weight-bearin g and bone-bonding orthopedic devices. (C) 2000 John Wiley & Sons, Inc.