Bioresorbable polylactide interbody implants in an ovine anterior cervical discectomy and fusion model: three-year results.
METHODS
In vivo study of anterior discectomy and fusion using a bioresorbable 70:30 poly(l-lactide-co-d,l-lactide) interbody implant in an ovine model.


OBJECTIVE
To evaluate the efficacy of the polylactide implant to function as an interbody fusion device, and to assess the tissue reaction to the material during the resorption process.


BACKGROUND
The use of polylactide as a cervical interbody implant has several potential advantages when compared with traditional materials. Having an elastic modulus very similar to bone minimizes the potential for stress shielding, and as the material resorbs additional loading is transferred to the developing fusion mass. Although preclinical and clinical studies have demonstrated the suitability of polylactide implants for lumbar interbody fusion, detailed information on cervical anterior cervical discectomy and fusion (ACDF) with polylactide devices is desirable.


METHODS
Single level ACDF was performed in 8 skeletally mature ewes. Bioresorbable 70:30 poly (l-lactide-co-d,l-lactide) interbody implants packed with autograft were used with single-level metallic plates. Radiographs were made every 3 months up to 1 year, and yearly thereafter. The animals were killed at 6 months (3 animals), 12 months (3 animals), and 36 months (2 animals). In addition to the serial plain radiographs, the specimens were evaluated by nondestructive biomechanical testing and undecalcified histologic analysis.


RESULTS
The bioresorbable polylactide implants were effective in achieving interbody fusion. The 6-month animals appeared fused radiographically and biomechanically, whereas histologic sections demonstrated partial fusion (in 3 of 3 animals). Radiographic fusion was confirmed histologically and biomechanically at 12 months (3 of 3 animals) and 36 months (2 of 2 animals). A mild chronic inflammatory response to the resorbing polylactide implant was observed at both 6 months and 12 months. At 36 months, the operative levels were solidly fused and the implants were completely resorbed. No adverse tissue response was observed in any animal at any time period.


CONCLUSIONS
Interbody fusion was achieved using bioresorbable polylactide implants, with no evidence of implant collapse, extrusion, or adverse tissue response to the material. The use of polylactide as a cervical interbody device appears both safe and effective based on these ACDF animal model results.
Thomas
Kevin A
KA
MacroPore Biosurgery, a Cytori Therapeutics Company, San Diego, California 92121, USA. kthomas2@san.rr.com
Toth
Jeffrey M
JM
Crawford
Neil R
NR
Seim
Howard B
HB
Shi
Lewis L
LL
Harris
Mitchel B
MB
Turner
A Simon
AS
D020341:Absorbable Implants; D000818:Animals; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000601:surgery*; D017586:Diskectomy / Q000295:instrumentation*; D005260:Female; D011091:Polyesters; D016059:Range of Motion, Articular; D034561:Sheep, Domestic; D013123:Spinal Fusion / Q000295:instrumentation*
D011091:Polyesters; C033616:poly(lactide)