Biomechanical comparison between C-7 lateral mass and pedicle screws in subaxial cervical constructs
Biomechanical comparison between C-7 lateral mass and pedicle screws in subaxial cervical constructs
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DOI：
10.3171/2010.5.spine09712
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发表时间：
2010-12-01
影响因子：
2.8
通讯作者：
Bydon, Ali
中科院分区：
文献类型：
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作者：
Xu, Risheng;McGirt, Matthew J.;Bydon, Ali
Object.本研究的目的是进行第一次体外生物力学比较的即时和后循环刚度的C-7侧块与C-7椎弓根螺钉在后路C4-7结构。对10例成人尸体脊柱标本分别采用C4-6侧块螺钉和C7侧块螺钉（5例）与椎弓根螺钉（5例）固定。将脊柱灌封在聚甲基丙烯酸甲酯骨水泥中，并置于材料试验机上。使用被动回射标记和红外运动捕捉相机测量绕弯曲轴的旋转。在未使用内固定、内固定后即刻以及在1 Hz下进行4 Nm屈伸和侧弯力矩的40，000次循环后，评估了C-4相对于C-7的屈伸和侧弯运动。分析内固定和周期性负荷对C4-7旋转运动的影响。两个队列的预内固定脊柱在骨密度和屈曲-伸展（p = 0.33）和侧弯（p = 0.16）活动度方面具有可比性。侧块和椎弓根螺钉结构显著减少了屈伸过程中的活动度（侧块螺钉为11.3度-0.26度，p = 0.002;椎弓根螺钉为10.51度-0.30度，p = 0.008）和侧弯（侧块螺钉为7.38度-0.27度，p = 0.003;椎弓根螺钉为11.65度-0.49度，p = 0.03）。在两个队列中，在周期性负荷后，在屈伸期间C4-7的旋转运动增加（侧块螺钉为0.26 °-0.68 °;椎弓根螺钉为0.30 °-1.31 °）和侧弯（分别为0.27度-0.39度和0.49度-0.80度），尽管增加没有统计学意义（p > 0.05）。侧块螺钉和椎弓根螺钉在周期后屈伸（p = 0.20）和侧弯（0.10）方面无统计学差异。C-7侧块和C-7椎弓根螺钉均允许对终止于C-7的轴下侧块结构进行同样的刚性固定。在固定后即刻和模拟6周内，C-7侧块螺钉在生物力学稳定长轴下侧块结构方面可能与C-7椎弓根螺钉一样有效。(DOI：10.3171/2010.5.5P1NE09712）
Object. The aim of this study was to conduct the first in vitro biomechanical comparison of immediate and postcyclical rigidities of C-7 lateral mass versus C-7 pedicle screws in posterior C4-7 constructs.Methods. Ten human cadaveric spines were treated with C4-6 lateral mass screw and C-7 lateral mass (5 specimens) versus pedicle (5 specimens) screw fixation. Spines were potted in polymethylmethacrylate bone cement and placed on a materials testing machine. Rotation about the axis of bending was measured using passive retroreflective markers and infrared motion capture cameras. The motion of C-4 relative to C-7 in flexion-extension and lateral bending was assessed uninstrumented, immediately after instrumentation, and following 40,000 cycles of 4 Nm of flexion-extension and lateral bending moments at 1 Hz. The effect of instrumentation and cyclical loading on rotational motion across C4-7 was analyzed for significance.Results. Preinstrumented spines for the 2 cohorts were comparable in bone mineral density and range of motion in both flexion-extension (p = 0.33) and lateral bending (p = 0.16). Lateral mass and pedicle screw constructs significantly reduced motion during flexion-extension (11.3 degrees-0.26 degrees for lateral mass screws, p = 0.002; 10.51 degrees-0.30 degrees for pedicle screws, p = 0.008) and lateral bending (7.38 degrees-0.27 degrees for lateral mass screws, p = 0.003; 11.65 degrees-0.49 degrees for pedicle screws, p = 0.03). After cyclical loading in both cohorts, rotational motion over C4-7 was increased during flexion-extension (0.26 degrees-0.68 degrees for lateral mass screws; 0.30 degrees-1.31 degrees for pedicle screws) and lateral bending (0.27 degrees-0.39 degrees and 0.49 degrees-0.80 degrees, respectively), although the increase was not statistically significant (p > 0.05). There was no statistical difference in postcyclical flexion-extension (p = 0.20) and lateral bending (0.10) between lateral mass and pedicle screws.Conclusions. Both C-7 lateral mass and C-7 pedicle screws allow equally rigid fixation of subaxial lateral mass constructs ending at C-7. Immediately and within a simulated 6-week postfixation period, C-7 lateral mass screws may be as effective as C-7 pedicle screws in biomechanically stabilizing long subaxial lateral mass constructs. (DOI: 10.3171/2010.5.5P1NE09712)