58. Benefits of macroscale topography features on and within interbody cages

Abstract

BACKGROUND CONTEXT Implant design, material, surfaces, graft and surgical techniques play important roles in the success of interbody fusions and the ability to radiographically assess. PEEK's positive attributes of mechanical properties and radiolucency are maintained using a molecularly bonded submicron deposition of titanium to improve bone on-growth. Novel macroscale topography features on the endplate surfaces and inside the aperture were hypothesized to allow early bone integration and mechanical stability. PURPOSE To evaluate the effect of macroscale topography on a PEEK/Titanium composite cage in a large animal model of interbody fusion. STUDY DESIGN/SETTING Preclinical large animal model. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Not applicable METHODS Lateral L45 interbody fusions were performed in 4-5-year-old ewes using a PEEK/titanium composite cage (Control group) compared to the same cage with macro 3D features on the endplate and inside the aperture (Test group). Iliac crest autograft was placed in the aperture and bilateral pedicle screws and rods for posterior stabilisation. Fusion assessment at 6 and 12 weeks (n=10 per group) included manual palpation, X-rays, mCT, tensile testing and pmMA histology. RESULTS The Test group's manual palpation was 9/10 and 10/10 at 6 and 12 weeks while the control was 4/10 and 7/10 at 6 and 12 weeks. Radiographs and mCT confirmed new bone formation in the aperture of the Control group cages with time while some areas of aperture radiolucency were present. Radiographs and mCT of the Test group cages revealed new bone formation and integration within the topography features on the endplates and inside the aperture which progressed with time. Histology confirmed the radiographic findings in the control group and integration with the host endplates and remodeled bone within the apertures in the Test group. Tensile testing demonstrated nearly a 3-fold statistically significant increase in mechanical properties at both time points for the Test group vs the control group. CONCLUSIONS The macroscale features in the Test group provided multiple opportunities for bone integration between the host endplates and graft within the aperture. Early bony integration translated to a statistically significant increase in mechanical strength compared to the control cage which did not include the same geometric features. Promising data in this clinically relevant animal model warrants further study in humans. FDA DEVICE/DRUG STATUS Shoreline RT (Approved for this indication).