63. Three-dimensional printing of titanium without bone graft outperforms PEEK + autologous iliac crest bone graft in sheep interbody fusion model

BACKGROUND CONTEXT There have been significant advancements in three-dimensional titanium printing and implant surface technology. Interbody implants using three-dimensional printed titanium (3D-Ti) and surface technology mimic trabecular bone structure, roughness/porosity, and modulus of elasticity. In addition to providing biomechanical support and scaffolding, interbody implants may have osteoinductive properties similar to bone graft by inciting cellular response and resulting in enhanced fusion. However, the actual ability of these structural improvements to affect the in vivo fusion cascade has not been clearly defined. PURPOSE To evaluate fusion of 3D-Ti without bone graft compare to PEEK and autologous iliac crest bone graft (ICBG) in a sheep interbody model. STUDY DESIGN/SETTING Randomized in vivo sheep interbody fusion animal trial. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Fusion as assessed by histology, microCT, and traditional CT. METHODS Eight PEEK and eight 3D-Ti implants were randomized to anterior lumbar interbody fusions at L2-3 or L4-5 in a sheep model. The PEEK cages were implanted with autologous ICBG. CT scans were performed at 4 weeks. CT, microCT and histology were performed at sacrifice (8 weeks). The robustness of fusion was graded A-D, where A is no fusion, B is fusion spot-welding to the cage, C is fusion through the cage, and D is fusion outside of the cage. RESULTS At both 4 and 8 weeks, there was no CT evidence of fusion (type A) in PEEK + ICBG implants (0%). Histologic analysis at sacrifice revealed substantial osteolysis and cellular delamination surrounding the PEEK cage with unincorporated/floating ICBG fragments. At 4 weeks in the 3D-Ti group without graft, there were 6/8 (75%) type B fusions and 2/8 (25%) robust fusions (type D). On CT and microCT at 8 weeks, the entire 3D-Ti group (100%) showed evidence of through and outside of the cage (type D). Histologic analysis showed extensive lamellar and mature bone formation on the trabecular structure of the titanium. CONCLUSIONS In an in vivo sheep interbody fusion model, implants created with 3D-Ti and surface technology without bone graft outperform PEEK + autologous ICBG with regard to radiographic and histologic fusion. The three-dimensional titanium technology with biomechanically similar characteristics to trabecular bone allows for more rapid, robust fusion in an animal model and may minimize the need for bone grafting and osteoinductive compounds. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.