Hong Jae Taek, Tomoyuki Takigawa, Jain Ashish, Orías Alejandro A Espinoza, Inoue Nozomu, An Howard S
Department of Neurosurgery, St. Vincent's Hospital, Catholic University of Korea, Suwon, South Korea.
Department of Orthopaedic Surgery, Okayama University Hospital, Okayama, Japan.
Eur Spine J. 2017 Sep;26(9):2417-2424. doi: 10.1007/s00586-017-5239-8. Epub 2017 Jul 27.
The pedicle screw construct is the most widely used technique for instrumentation at cervicothoracic junction (CTJ) because of its high biomechanical stability. However, we may need salvage fixation options for it as there might be a situation when pedicle screw is not available or it initially fails in order to obviate the need to instrument an additional motion segment. We aimed to evaluate the ability of using salvage screw fixations at CTJ (C7, T1, T2), when the initial fixation method fails.
Fifteen fresh-frozen cadaveric specimens (C7-T2) were tested for pull-out strength (POS, N) and insertion torque (IT, Nm) of three C7 fixation techniques (lateral mass, pedicle and laminar screw) and three upper thoracic spine instrumentation (pedicle screws with straight trajectory, anatomical trajectory pedicle screws and laminar screw). Data are shown as mean ± standard deviation (SD).
C7 pedicle screws generated statistically greater IT and POS than other C7 fixation techniques (P < 0.05). Similar trends were observed with pedicle fixation as a salvage procedure (P < 0.05). Laminar screws yielded significantly higher POS values than lateral mass fixation when applied as a salvage C7 fixation (mean POS: lateral mass screw-299.4 ± 173.8 N, laminar screw-629.3 ± 216.1, P = 0.013). Significant relationship was established between IT and POS for all screws using Pearson correlation coefficient analysis (r = 0.624, P < 0.01). Pedicle screw with different trajectory (anatomical vs straightforward) did not show any significant difference in terms of POS as the initial and salvage fixation of upper thoracic spine. As a salvage fixation technique, there was no significant difference between laminar screw and a pedicle screw with different trajectory (P > 0.05).
Laminar screws appear to provide stronger and more reproducible salvage fixation than lateral mass screws for C7 fixation, if pedicle screw should fail. If failure of initial pedicle screw is verified at the upper thoracic spine, both laminar screw and pedicle screw with different trajectory could be an option of salvage fixation. Our results suggest that pedicle screws and laminar screw similarly provide a strong fixation for salvage applications in the cervicothoracic junction.
由于其较高的生物力学稳定性，椎弓根螺钉结构是颈椎胸段交界处（CTJ）最广泛使用的内固定技术。然而，我们可能需要其挽救性固定方案，因为可能存在椎弓根螺钉不可用或最初失败的情况，以便避免对额外运动节段进行内固定。我们旨在评估当初始固定方法失败时，在CTJ（C7、T1、T2）使用挽救性螺钉固定的能力。
对15个新鲜冷冻尸体标本（C7-T2）测试三种C7固定技术（侧块、椎弓根和椎板螺钉）以及三种上胸椎内固定（直轨迹椎弓根螺钉、解剖轨迹椎弓根螺钉和椎板螺钉）的拔出强度（POS，N）和插入扭矩（IT，Nm）。数据以平均值±标准差（SD）表示。
C7椎弓根螺钉产生的IT和POS在统计学上高于其他C7固定技术（P<0.05）。作为挽救性手术的椎弓根固定也观察到类似趋势（P<0.05）。当作为挽救性C7固定应用时，椎板螺钉产生的POS值显著高于侧块固定（平均POS：侧块螺钉-299.4±173.8 N，椎板螺钉-629.3±²16.1，P = 0.013）。使用Pearson相关系数分析，所有螺钉的IT和POS之间建立了显著关系（r = 0.624，P<0.01）。不同轨迹（解剖与直形）的椎弓根螺钉作为上胸椎的初始和挽救性固定，在POS方面没有显示出任何显著差异。作为挽救性固定技术，椎板螺钉和不同轨迹的椎弓根螺钉之间没有显著差异（P>0.05）。
如果椎弓根螺钉失败，对于C7固定，椎板螺钉似乎比侧块螺钉提供更强且更可重复的挽救性固定。如果在上胸椎证实初始椎弓根螺钉失败，椎板螺钉和不同轨迹的椎弓根螺钉都可以是挽救性固定的选择。我们的结果表明，椎弓根螺钉和椎板螺钉同样为颈椎胸段交界处的挽救性应用提供了牢固的固定。
