Osseointegration of boron-coated implants in the animal spine model

Aim: In today's world, instrumentation plays a significant role in the treatment of spinal disorders, which are important causes of cost and morbidity. Over the years, many implants have been tried by dentists and orthopedic surgeons and developed by biomechanical engineers. Throughout this development, implantology has gained increasing importance, and the osseointegration of implants, i.e., the interface between bone and implant, has been further detailed. The popularity of this field has provided a certain standardization in the evaluation of osseointegration, initially through invasive methods such as histological analyses. With the advancement of technology, there has been a growing trend towards non-invasive methods such as micro-computed tomography (mCT). As a result, research in this field has gained momentum, and attempts have been made to address the shortcomings of implants through surface modifications and coatings.The contribution of the boron element to bone formation and osseointegration has been evident in many recent studies, with highly positive results obtained from implants coated with boron. Additionally, most of these studies lack in vivo experiments, and due to their size, spinal instrumentation has not been tested in any experimental animal. With our study, we aim to present, for the first time from the perspective of neurosurgery, the evaluation of osseointegration in the vertebrae of rats through in vivo micro-computed tomography analysis using the physically vapor-deposited (PVD) boron-coated implants, a method applied for the first time. Materials and methods: In this study, a total of 24 male Wistar albino rats were used, with 12 randomly assigned to receive titanium alloy (Ti6Al4V) implants (n=12) and the other 12 to receive titanium alloy implants coated with boron using the physically vapor-deposited (PVD) method (n=12). The implants were unilaterally implanted into the lumbar vertebrae of the subjects using the same surgical method. All implants were 4 mm in length and consisted of uniform screws with a diameter of 1.6 mm. The groups receiving coated and uncoated implants were sacrificed at 1 and 2 months post-implantation, and they were further divided into two subgroups (n=6) for micro-computed tomography (mCT) analysis. The mCT analysis aimed to investigate the degrees of osseointegration based on bone-to-implant contact (BIC) and bone volume fraction (BV/TV) ratios at 1 and 2 months after implantation for both coated and uncoated implant groups. Results: According to the mBT analysis conducted at the end of the 1-month observation period, statistically significant differences were detected in the BIC (p=0.025) and BV/TV (p=0.016) values in the vertebral regions of the subjects with boron-coated implants, favoring the implants treated with boron. Similarly, at the end of the 2nd month, the analysis revealed significant results in favor of boron-coated implants in both BIC (p=0.037) and BV/TV (p=0.037) values. Conclusions: When traditionally used titanium alloy implants undergo surface modification with boron, it has been observed that they provide a significantly beneficial osseointegration with higher bone-to-implant contact (BIC) and bone volume fraction (BV/TV) ratios, resulting in a more effective bone-implant interface. This study, which represents the first example in the field of neurosurgery and spinal implantation for boron-modified implants, suggests that their usage holds promise due to their high osseointegration potential. The conclusion reached is that further research in this area could be beneficial, given the promising results observed in terms of osseointegration.