A carbon fiber implant to aid interbody lumbar fusion. Mechanical testing.

A carbon-fiber-reinforced polymer implant has been designed to aid interbody lumbar fusion. The cage-like implant has ridges or teeth to resist pullout or retropulsion, struts to support weight bearing, and a hollow center for packing of autologous bone graft. Because carbon is radiolucent, bony healing can be imaged by standard radiographic techniques. The device has been mechanically tested in cadaver spines and compared with posterior lumbar interbody fusion performed with donor bone. The carbon device required a pullout force of 353 N compared with 126 N for donor bone. In compression testing, posterior lumbar interbody fusion performed with the carbon device bore a load of 5,288 N before failure of the vertebral bone. Posterior lumbar interbody fusion performed with donor bone failed at 4,628 N, and unmodified motion segments failed at 6,043 N. The carbon fiber implant separates the mechanical and biologic functions of posterior lumbar interbody fusion.