Blaskiewicz Donald J, Harris Jeffrey E, Han Patrick P, Turner Alexander W, Mundis Gregory M
Neurosurgical Medical Clinic, Inc., 8010 Frost St. Suite 414, San Diego, CA, 92123, USA.
NuVasive, Inc., San Diego, CA, USA.
Eur Spine J. 2018 Feb;27(2):433-441. doi: 10.1007/s00586-017-5110-y. Epub 2017 May 13.
Cervical spine malalignment can develop as a consequence of degenerative disc disease or following spinal surgery. When normal sagittal alignment of the spine is disrupted, further degeneration may occur adjacent to the deformity. The purpose of this study was to investigate changes in lordosis and sagittal alignment in the cervical spine after insertion of supraphysiologic lordotic implants.
Eight cadaveric cervical spines (Occiput-T1) were tested. The occiput was free to translate horizontally and vertically but constrained from angular rotation. The T1 vertebra was rigidly fixed with a T1 tilt of 23°. Implants with varying degrees of lordosis were inserted starting with single-level constructs (C5-C6), followed by two (C5-C7), and three-level (C4-C7) constructs. Changes in sagittal alignment, Occ-C2 angle, cervical lordosis (C2-7), and segmental lordosis were measured.
Increasing cage lordosis led to global increases in cervical lordosis. As implanted segmental lordosis increased, the axial levels compensated by decreasing in lordosis to maintain horizontal gaze. An increase in cage lordosis also corresponded with larger changes in SVA.
Reciprocal compensation was observed in the axial and sub-axial cervical spine, with the Occ-C2 segment undergoing the largest compensation. Adding more implant lordosis led to larger reciprocal changes and changes in SVA. Implants with supraphysiologic lordosis may allow for additional capabilities in correcting cervical sagittal plane deformity, following further clinical evaluation.
颈椎排列不齐可因椎间盘退变疾病或脊柱手术后发生。当脊柱正常矢状面排列被破坏时，畸形相邻部位可能会发生进一步退变。本研究的目的是调查插入超生理前凸植入物后颈椎前凸和矢状面排列的变化。
对8个尸体颈椎（枕骨 - T1）进行测试。枕骨可在水平和垂直方向自由平移，但限制角旋转。T1椎体以23°的T1倾斜度牢固固定。从单节段结构（C5 - C6）开始，依次插入不同程度前凸的植入物，随后是双节段（C5 - C7）和三节段（C4 - C7）结构。测量矢状面排列、枕骨 - C2角、颈椎前凸（C2 - 7）和节段性前凸的变化。
椎间融合器前凸增加导致颈椎前凸整体增加。随着植入节段性前凸增加，轴向节段通过前凸减小进行代偿以维持水平注视。椎间融合器前凸增加也与矢状面垂直轴偏移（SVA）的更大变化相对应。
在颈椎轴性节段和下位节段观察到相互代偿，其中枕骨 - C2节段代偿最大。增加植入物前凸导致更大的相互变化和SVA变化。经过进一步临床评估，具有超生理前凸的植入物可能在矫正颈椎矢状面畸形方面具有额外能力。
