Shah Furqan A, Johansson Martin L, Omar Omar, Simonsson Hanna, Palmquist Anders, Thomsen Peter
Department of Biomaterials, Institute of Clinical Sciences, Sahlgrenska Academy at University of Gothenburg, Göteborg, Sweden.
BIOMATCELL VINN Excellence Center of Biomaterials and Cell Therapy, Gothenburg, Sweden.
PLoS One. 2016 Jun 14;11(6):e0157504. doi: 10.1371/journal.pone.0157504. eCollection 2016.
Osseointegrated implants inserted in the temporal bone are a vital component of bone-anchored hearing systems (BAHS). Despite low implant failure levels, early loading protocols and simplified procedures necessitate the application of implants which promote bone formation, bone bonding and biomechanical stability. Here, screw-shaped, commercially pure titanium implants were selectively laser ablated within the thread valley using an Nd:YAG laser to produce a microtopography with a superimposed nanotexture and a thickened surface oxide layer. State-of-the-art machined implants served as controls. After eight weeks' implantation in rabbit tibiae, resonance frequency analysis (RFA) values increased from insertion to retrieval for both implant types, while removal torque (RTQ) measurements showed 153% higher biomechanical anchorage of the laser-modified implants. Comparably high bone area (BA) and bone-implant contact (BIC) were recorded for both implant types but with distinctly different failure patterns following biomechanical testing. Fracture lines appeared within the bone ~30-50 μm from the laser-modified surface, while separation occurred at the bone-implant interface for the machined surface. Strong correlations were found between RTQ and BIC and between RFA at retrieval and BA. In the endosteal threads, where all the bone had formed de novo, the extracellular matrix composition, the mineralised bone area and osteocyte densities were comparable for the two types of implant. Using resin cast etching, osteocyte canaliculi were observed directly approaching the laser-modified implant surface. Transmission electron microscopy showed canaliculi in close proximity to the laser-modified surface, in addition to a highly ordered arrangement of collagen fibrils aligned parallel to the implant surface contour. It is concluded that the physico-chemical surface properties of laser-modified surfaces (thicker oxide, micro- and nanoscale texture) promote bone bonding which may be of benefit in situations where large demands are imposed on biomechanically stable interfaces, such as in early loading and in compromised conditions.
植入颞骨的骨整合植入物是骨锚式听力系统（BAHS）的重要组成部分。尽管植入物失败率较低，但早期加载方案和简化程序需要应用能够促进骨形成、骨结合和生物力学稳定性的植入物。在此，使用Nd:YAG激光对商业纯钛螺旋形植入物的螺纹槽进行选择性激光烧蚀，以产生具有叠加纳米纹理和增厚表面氧化层的微观形貌。采用先进的机械加工植入物作为对照。在兔胫骨中植入八周后，两种植入物的共振频率分析（RFA）值从植入到取出均有所增加，而取出扭矩（RTQ）测量显示激光改性植入物的生物力学锚固力高153%。两种植入物的骨面积（BA）和骨-植入物接触面积（BIC）相当，但在生物力学测试后具有明显不同的失效模式。激光改性表面约30-50μm处的骨内出现骨折线，而机械加工表面的骨折线则出现在骨-植入物界面处。发现RTQ与BIC之间以及取出时的RFA与BA之间存在强相关性。在所有骨均为新生骨的骨内膜螺纹中，两种植入物的细胞外基质组成、矿化骨面积和骨细胞密度相当。使用树脂铸型蚀刻法，观察到骨细胞小管直接靠近激光改性植入物表面。透射电子显微镜显示，除了与植入物表面轮廓平行排列的高度有序的胶原纤维外，小管也靠近激光改性表面。得出的结论是，激光改性表面的物理化学表面特性（更厚的氧化物、微米和纳米级纹理）促进了骨结合，这在对生物力学稳定界面有高要求的情况下可能是有益的，例如在早期加载和受损条件下。
