The in vivo response to a novel ti coating compared to PEEK: evaluation of the periphery and inner surfaces of an implant

Publication date: Available online 26 February 2018
Source:The Spine Journal
Author(s): W.R. Walsh, M. Pelletier, C. Christou, J. He, F. Vizesi, S.D. Boden
BackgroundContext: Increasing bone ongrowth and ingrowth of PEEK interbody fusion devices has the potential to improve clinical outcomes.PurposeThis study evaluated the in vivo response of promoting new bone growth and bone apposition with NM compared to PEEK alone in a cancellous implantation site with an empty aperture.Study DesignThis is a randomized control animal studyMethodsImplants and funding for this study were provided by SeaSpine (60,000 USD).Cylindrical dowels with two apertures were prepared as PEEK with a sub-micron layer of the titanium (NanoMetalene, NM). The titanium coating was applied over the entire implant (Group 1) or just the apertures (Group 2). PEEK implants with no coating served as controls (Group 3). Implants were placed in the cancellous bone of the distal femur or proximal tibia with no graft material placed in the apertures in eight adult sheep. Bone ongrowth to the surface of the implant and ingrowth into the apertures was assessed at 4 and 8 week after surgery with micro-computed tomography and undecalcified histology.ResultsThe apertures in the implants were notably empty in the PEEK group at 4 and 8 weeks. In contrast, new bone formation into the apertures was found in samples coated with NM even though no graft material was placed into the defect. The bone growing into the aperture tracked along the titanium layer. Apertures with the titanium coating demonstrated significantly more bone by micro-CT qualitative grading compared to PEEK with average bone coverage scores of Group 1 (NM) 1.62±0.89, Group 2 (NM apertures only) 1.62±0.77 and Group 3 (PEEK) 0.43±0.51 respectively at 4 weeks (p<0.01) and Group 1 (NM) 1.79±1.19, Group 2 (NM apertures only) 1.98±1.18 and Group 3 (PEEK) 0.69±0.87 respectively at 8 weeks (p<0.05). The amount of bone in the apertures (ingrowth) quantified using the volumetric data from the micro computed tomography supported an overall increase in bone volume inside the apertures with the titanium coating compared to PEEK. Histology showed newly formed woven bone tracked along the surface of the titanium in the apertures. The PEEK interface presented the typical non-reactive fibrous tissue inside the apertures at 4 weeks and some focal contact with bone on the outside at 4 weeks and 8 weeksConclusionsMicro-computed tomography and histology demonstrated bone ongrowth to the surfaces coated with NM where the newly formed bone tracked along the thin titanium coated surfaces. PEEK surfaces presented the non-reactive fibrous tissue at the interface as previously reported in pre-clinical scenarios.



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