A biomechanical comparison between cortical bone trajectory fixation and pedicle screw fixation
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RESEARCH ARTICLE
Open Access
A biomechanical comparison between cortical bone trajectory fixation and pedicle screw fixation Hiroki Oshino1, Toshihiko Sakakibara2, Tadashi Inaba1, Takamasa Yoshikawa1, Takaya Kato3 and Yuichi Kasai2*
Abstract Purpose: There have been several reports on the pullout strength of cortical bone trajectory (CBT) screws, but only one study has reviewed the stability of functional spine units using the CBT method. The purpose of this study was to compare vertebral stability after CBT fixation with that after pedicle screw (PS) fixation. Methods: In this study, 20 lumbar spine (L5–6) specimens were assigned to two groups: the CBT model group that underwent CBT screw fixation (n = 10) and the PS model group that underwent pedicle screw fixation (n = 10). Using a six-axis material testing machine, bend and rotation tests were conducted on each model. The angular displacement from the time of no load to the time of maximum torque was defined as range of motion (ROM), and then, the mean ROM in the bend and rotation tests and the mean rate of relative change of ROM in both the bend and rotation tests were compared between the CBT and PS groups. Results: There were no significant differences between the CBT and PS groups with regard to the mean ROMs and the mean rate of relative change of ROMs in both the bend and rotation tests. Conclusion: Intervertebral stability after CBT fixation was similar to that after PS fixation. Keywords: Lumbar spine, Biomechanics, Spinal fusion, Spinal instrumentation, Stability
Introduction Spinal fusion using cortical bone trajectory (CBT) was devised by Santoni et al. [1] in 2009. The CBT method of spinal fusion has many advantages compared with pedicle screw (PS) fixation, including a low risk of nerve damage; low invasiveness, as the external side of the intervertebral joint need not be exposed [2]; and high stability among patients with osteoporosis or obesity having spinal diseases [3, 4]. Although several studies have reported that the pullout strength and insertion torque of CBT screws are higher than those of PSs [5, 6], only one study has evaluated the functional spine unit (FSU) and compared intervertebral stability between the two methods (Perez-Orribo et al. [7]), and this study only evaluated intervertebral stability after the CBT method in cases with no damage to the * Correspondence: [email protected] 2 Department of Spinal Surgery and Medical Engineering, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu City, Mie 514-8507, Japan Full list of author information is available at the end of the article
posterior vertebral elements and did not examine the stability of damaged vertebrae. In the present study, deer cadaver models with a damaged lumbar spine were used, and intervertebral stability with use of CBT or the conventional PS fixation methods was evaluated.
Materials and methods Twenty lumbar (L5–6) FSUs from a 3-year-old male deer cadaver (Sika deer, Cervus nippon) hunted for wild animal damage prevention were used
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