Department of Orthopedic Surgery, Keio University School of Medicine, Shinjuku, Tokyo, Japan.
Department of Orthopedic Surgery, International University of Health and Welfare School of Medicine, Narita, Chiba, Japan.
PLoS One. 2018 Jun 28;13(6):e0199362. doi: 10.1371/journal.pone.0199362. eCollection 2018.
Pull-out force and insertion torque have not been generally used as intraoperative measures for the evaluation of pedicle screw stability because of their invasiveness. On the other hand, resonance frequency analysis is a non-invasive and repeatable technique that has been clinically used in dentistry to evaluate implant stability e.g. by the Osstell apparatus. In this study, the characteristics of the implant stability quotient (ISQ) value obtained by the Osstell apparatus in the field of spinal surgery were investigated. Biomechanical test materials simulating human bone were used to provide a comparative platform for evaluating each fixation strength measure, including pull-out force, insertion torque, and the ISQ value. To perform pull-out force measurement and to repeat pedicle screw insertion and removal, loosening was artificially created, and its effect was investigated. The grade of loosening was quantified on a micro-CT image after pedicle screw removal. In the comparison of the 3 fixation strength measures, the correlations of the ISQ value with the pull-out force (R2 = 0.339 p <0.0001) and the insertion torque (R2 = 0.337 p <0.0001) were lower than the correlation between pull-out force and insertion torque (R2 = 0.918 p <0.0001). On a micro-CT study, the material volume of the internal threads disappeared after destruction of its integrity due to repeated pedicle screw insertion and removal. Material integrity destruction of the internal threads decreased only the pull-out force and the insertion torque, but it did not affect the ISQ value. The ISQ value only decreased when the material volume of the internal threads disappeared, probably because the ISQ value reflects the resistance against a force in the perpendicular direction of the screw, unlike the conventional measures of fixation strength, such as pull-out force and insertion torque, which reflect axial load.
拔出力和插入扭矩通常不作为评价椎弓根螺钉稳定性的术中测量指标，因为它们具有侵袭性。另一方面，共振频率分析是一种非侵入性且可重复的技术，已在牙科临床中用于评估种植体稳定性，例如使用 Osstell 仪器。在本研究中，研究了 Osstell 仪器在脊柱外科领域获得的种植体稳定性指数（ISQ）值的特征。使用模拟人体骨骼的生物力学测试材料为评估每种固定强度测量方法（包括拔出力、插入扭矩和 ISQ 值）提供了一个比较平台。为了进行拔出力测量并重复椎弓根螺钉的插入和移除，人为地造成松动，并研究了其效果。在移除椎弓根螺钉后，通过微 CT 图像对松动程度进行量化。在 3 种固定强度测量方法的比较中，ISQ 值与拔出力（R2 = 0.339，p <0.0001）和插入扭矩（R2 = 0.337，p <0.0001）的相关性低于拔出力和插入扭矩之间的相关性（R2 = 0.918，p <0.0001）。在微 CT 研究中，由于椎弓根螺钉的反复插入和移除破坏了其完整性，内部螺纹的材料体积消失。内部螺纹的材料完整性破坏仅降低了拔出力和插入扭矩，但不影响 ISQ 值。只有当内部螺纹的材料体积消失时，ISQ 值才会降低，这可能是因为 ISQ 值反映了垂直于螺钉方向的阻力，而不像拔出力和插入扭矩等传统固定强度测量方法，它们反映的是轴向载荷。
