INTRODUCTION

Vertebral body replacement represents one of the most challenging, complex and invasive spinal procedures. Even though modern surgical techniques for en bloc resection of vertebral body are consolidating, this procedure is burdened by complication rates as high as 45.5%. Among the complications, surgical site infections are particularly critical and difficult to treat. Poor bone regeneration and mechanical instability are further issues, also correlated with infections. The project proposes to implement personalized vertebral prosthesis optimizing implant architecture by 3D modeling and additive manufacturing technologies and combining a nanostructured antibacterial coatings of silver to prevent infections combined with hydroxyapatite or bone apatite to promote fast and effective bone regeneration.

METHODS

In order to develop a 3D-printed customized vertebra prosthesis an optimization of the design and manufacturing has been performed. Nanostructured and biomimetic coatings with antibacterial activity have been realized exploring and comparing different deposition techniques (Ionized Jet Deposition and Magnetron Sputtering). Chemical-physical investigations (i.e. FT-IR, EDS, SEM, scratch and wettability tests) and microbiological assays with representative bacterial strains (S. Aureus and E.Coli) have been performed as well as preclinical in vitro and in vivo biocompatibility test to investigate the efficacy of the proposed approach.

RESULTS

The work on device optimization lead to the selection of giroyd deformed structure with porosity of 90% and pore size in principal of 1.3 x 2.6 mm. The results from physic-chemical investigations showed that both investigated techniques ensured good transfer in composition from target to the coatings which possessed  nanostructured surface morphology and homogeneous distribution of the elements concentration. Coatings were no cytotoxic (UNI EN ISO 10993-5 rules) and the selected coatings exerted an inhibitory activity against bacterial growth. In vitro bioactivity of the selected nanostructured coatings showed primary human osteoblast viability, proliferation, adhesion and differentiation. In vivo macroscopic and microscopic analysis indicated that nanostructured coating did not cause inflammatory or adverse tissue reactions but they were able to promote osteointegration process.

DISCUSSION

The implementation of a personalized custom device by combining nanostructured antibacterial and biomimetic coatings with the simultaneous optimization of implant architecture by 3D modeling and additive manufacturing can represent an exploitable approach to increase patients’ surgical options after spine resection.

ACKNOWLEDGEMENTS: These activities were funded by National Funding Organisations (Ministero della Salute – IMH, Italy) under the frame of EuroNanoMed III Project “Next generation antibacterial nanostructured osseointegrated customized vertebral replacement – NANOVERTEBRA” Joint Transnational call for proposals (JTC 2018).