Four-year follow-up of poly-L-lactic Acid cages for lumbar interbody fusion in goats.
BACKGROUND
New applications of bioabsorbable polymer implants demand for histologic evaluation because a host tissue response is elicited and late complications after polymer implantation have been reported. Furthermore, in load-bearing regions an accelerated polymer degradation and foreign body reaction may be observed.


METHODS
Lumbar interbody fusion procedures were performed using poly-L-lactic acid (PLLA) and titanium cages in 43 goats. At 3, 6, 12, 24, 36, and 48 months after surgery, sequential histologic analysis of instrumented motion segments, lymph nodes, and nervous structures was performed. Blood samples were retrieved for laboratory analysis.


RESULTS
No adverse local or distant histologic or systemic effects were observed during the absorption of the poly-L-lactic acid cages. Interbody fusion was maintained, and only a very mild inflammatory response was observed. In half the specimens complete absorption was observed, and in the remaining specimens an estimated 1-10% of the original PLLA was present at the 3-year follow-up. At the 4-year follow-up, five out of seven PLLA specimens showed no PLLA particles under polarized light microscopy. In the remaining two specimens an estimated 1% of the original PLLA could be observed.


CONCLUSIONS
Poly-L-lactic acid cages are feasible for lumbar interbody fusion, and the biocompatibility under high load bearing conditions is excellent during the complete absorption of the PLLA interbody fusion cages.
van Dijk
Martijn
M
Department of Orthopaedic Surgery, Vrije Universiteit Medical Center, Amsterdam, The Netherlands.
van Diest
Paul J
PJ
Smit
Theo H
TH
Berkhof
Hans
H
Burger
Elisabeth H
EH
Wuisman
Paul I J M
PI
D020341:Absorbable Implants; D000818:Animals; D001672:Biocompatible Materials; D001842:Bone and Bones / Q000473:pathology*; D004343:Drug Implants; D005260:Female; D005500:Follow-Up Studies; D006041:Goats; D019344:Lactic Acid; D008159:Lumbar Vertebrae; D011091:Polyesters; D011108:Polymers; D013123:Spinal Fusion
D001672:Biocompatible Materials; D004343:Drug Implants; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)