title: In vitro and in vivo degradation of bioabsorbable PLLA spinal fusion cages.
abstract: The in vitro and in vivo degradation of poly-L-lactic acid cages used as an adjunct to spinal arthrodesis was investigated. In the in vitro experiments cages were subjected to aging up to 73 weeks in phosphate-buffered solution (pH 7.4) at 37 degrees C. Inherent viscosity, crystallinity, and mechanical strength were determined at different time points. In the in vivo study, the poly-L-lactic acid cages were packed with bone graft and implanted in the L3-L4 spinal motion segment of 18 Dutch milk goats. At 12, 26, and 52 weeks, the motion segments were isolated and poly-L-lactic acid samples retrieved. On evaluation, the in vivo implanted cages showed an advanced decline in inherent viscosity compared to the cages subjected to in vitro degradation experiments. At 6 months of implantation, the geometrical shape and original height of 10 mm was maintained during 6 months of follow up. This finding fits well with the observation that mechanical strength was maintained for a period of 6 months in vitro. At 12 months, the poly-L-lactic acid cage had been disintegrated into multiple fragments with signs of absorption. Despite the high-load-bearing conditions, the poly-L-lactic acid cage allowed interbody fusion to occur without collapse of the cage.
authors.affiliation: Department of Orthopaedic Surgery, Vrije Universiteit Medical Center, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: van Dijk
authors.forename: D C
authors.initials: DC
authors.lastname: Tunc
authors.forename: T H
authors.initials: TH
authors.lastname: Smit
authors.forename: P
authors.initials: P
authors.lastname: Higham
authors.forename: E H
authors.initials: EH
authors.lastname: Burger
authors.forename: P I J M
authors.initials: PI
authors.lastname: Wuisman
mesh_terms: D000042:Absorption; D000818:Animals; D001672:Biocompatible Materials / Q000378:metabolism*; D001673:Biodegradation, Environmental; D015194:Diffusion Chambers, Culture; D005260:Female; D006041:Goats; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000378:metabolism*; D008159:Lumbar Vertebrae / Q000601:surgery; D008422:Materials Testing; D023421:Models, Animal; D011091:Polyesters; D011108:Polymers / Q000378:metabolism*; D013123:Spinal Fusion / Q000295:instrumentation*; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)