In vitro and in vivo degradation of bioabsorbable PLLA spinal fusion cages.
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.
van Dijk
M
M
Department of Orthopaedic Surgery, Vrije Universiteit Medical Center, Amsterdam, The Netherlands.
Tunc
D C
DC
Smit
T H
TH
Higham
P
P
Burger
E H
EH
Wuisman
P I J M
PI
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
D001672:Biocompatible Materials; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)