P7. Hierarchical surface roughness produced with additive manufacturing technology significantly increases osteogenic cellular differentiation and gene expression when compared to PEEK and smooth titanium surfaces

BACKGROUND CONTEXT Spine interbody fusion devices are used to stabilize and treat diseased and degenerative spine conditions. Commonly utilized interbody fusion devices are comprised of polyetheretherketone (PEEK) or titanium (Ti). PEEK interbody devices have a hydrophobic surface that does not directly bond to bone and promotes fibrous tissue formation. In contrast, Tispinal fusion devices have favorable osseointegration properties especially for those with roughened surfaces. PURPOSE Previous studies have shown that nano-scale surface features created by subtractive grit blasting and acid etching increase osteogenic differentiation and gene expression when compared to PEEK or smooth Ti (Sm Ti) surfaces. More recently, proprietary 3D additive manufacturing processes have been used to create implants that have a hierarchical surface roughness that spans from the macro to nano-scale. The objective of this study was to evaluate whether the P3D surface increases osteogenic differentiation and gene expression when compared to PEEK or smooth Ti surfaces, as similarly seen in acid etch surfaces. STUDY DESIGN/SETTING N/A PATIENT SAMPLE N/A OUTCOME MEASURES N/A METHODS The P3D implants with hierarchical surface roughness were produced on a Q 10+ 3D printer (Arcam). Bone marrow was harvested from a BAC transgenic reporter mouse. Primary bone marrow stem cells (BMSC) were cultured under basal conditions and seeded onto P3D, Sm Ti, or PEEK constructs. Cell-constructs cultured in osteogenic condition were harvested at days 3, 7, 14 and 22. Cells were removed by accutase for fluorescence image cytometry. RNA evaluation was performed by submerging in trizol and physical scraping. cDNA synthesis and qPCR utilized sequences for 18S, osteocalcin, collagen type 1, alkaline phosphatase, osterix and PHEX. Students 2-tailed t-test was utilized to evaluate statistical differences. RESULTS Significantly more (p CONCLUSIONS Compared to PEEK and Sm Ti surfaces, the P3D rough Ti surface enabled a significantly greater proportion of BMSC to enter the osteogenic lineage and resulted in faster and significantly greater osteogenic gene expression. Similar to prior publications that demonstrated increased osteogenesis on nanotopography surfaces, P3D with macro to nano-scale surface roughness also increased osteogenesis. The increased osteogenic response from the 3DP surface features may lead to quicker bone/implant fixation which would provide a stable environment for fusion to occur and reduce the risk of complications. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.