Hydroxylapatite/poly(L‐lactide) composites: An animal study on push‐out strengths and interface histology

Abstract

In the development of new materials for resorbable systems for bone fixation and replacement, composites of hydroxylapatite and poly (L‐lactide) (HA/PLLA) were tested. In a transcortical implantation model in goats the interactions at the bone‐implant interface were studied with post‐operative intervals up to 1 year. Push‐out testing of the implants indicated that PLLA reinforced with 50 wt% hydroxylapatite coating of 50 μm thickness increases interfacial shear strength at 3 months of implantation when compared to unfilled poly(L‐lactide) (P < .01). Scanning electron microscopy showed that the failure mode was predominantly at the coating‐implant interface. Implantation periods longer than 3 months did not result in a significant increase in push‐out strength because of the resorbing PLLA matrix. In support of the above findings there was histological evidence, on a light microscopical level, of increased bone contact at the interface for the composites, HA incorporated in or coated on PLLA, compared to unfilled poly(L‐lactide). © 1993 John Wiley & Sons, Inc.