Gambhir Shanu, Wang Tian, Pelletier Matthew H, Walsh William R, Ball Jonathon R
Royal North Shore Hospital, St Leonards, New South Wales, Australia.
Surgical & Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW Sydney, Prince of Wales Hospital, Sydney, New South Wales, Australia.
World Neurosurg. 2019 Jun;126:e606-e611. doi: 10.1016/j.wneu.2019.02.100. Epub 2019 Mar 2.
Consideration of sagittal alignment is an integral part of spinal fusion surgery correlating with superior outcomes. Segmental lordosis is an important contributor to sagittal alignment. This study assessed surgical factors influencing segmental lordosis in a 360° fusion model, including cage dimensions, anterior longitudinal ligament resection, facetectomy, and posterior compression.
Six L3-4 synthetic spinal motion segments were used in a repeated measures design. Each sample was sequentially instrumented with lateral cages of increasing height and angle. Lordosis was assessed from lateral radiographs of intact and each instrumented condition. The effect of anterior longitudinal ligament resection, posterior compression with pedicle screws, and bilateral facetectomy was additionally examined.
A linear relationship between segmental lordosis and cage height was found. This effect was greater with the anterior longitudinal ligament divided. In cages of the same anterior height, increased intrinsic cage lordosis did not result in increased segmental lordosis; cages with no intrinsic lordosis resulted in the highest segmental lordosis. In examining this finding, it was shown that posterior cage height had a larger influence on segmental lordosis. Posterior compression with pedicle screws and bilateral facetectomy increased the segmental lordosis by a further 3.4° and 2.6°, respectively.
Cage height was a key factor, with posterior compression further increasing lordosis. The finding that 0° cages results in the most segmental lordosis was an unexpected finding and highlights the importance of appropriate sizing on resulting lordosis. These findings are relevant to cage selection but require further study prior to applying to clinical practice and may influence future cage design.
矢状面排列的考量是脊柱融合手术不可或缺的一部分，与更好的手术效果相关。节段性前凸是矢状面排列的重要影响因素。本研究评估了在360°融合模型中影响节段性前凸的手术因素，包括椎间融合器尺寸、前纵韧带切除、关节突切除和后路加压。
采用重复测量设计，使用6个L3 - 4合成脊柱运动节段。每个样本依次安装高度和角度逐渐增加的外侧椎间融合器。通过完整状态及每个植入状态的侧位X线片评估前凸情况。此外，还研究了前纵韧带切除、椎弓根螺钉后路加压和双侧关节突切除的影响。
发现节段性前凸与椎间融合器高度呈线性关系。在前纵韧带切断的情况下，这种影响更大。在相同前侧高度的椎间融合器中，椎间融合器本身前凸增加并不会导致节段性前凸增加；本身无前凸的椎间融合器导致的节段性前凸最高。在研究这一发现时发现，椎间融合器后侧高度对节段性前凸的影响更大。椎弓根螺钉后路加压和双侧关节突切除分别使节段性前凸进一步增加3.4°和2.6°。
椎间融合器高度是关键因素，后路加压会进一步增加前凸。0°椎间融合器导致最大节段性前凸这一发现是意外发现，凸显了合适尺寸对最终前凸的重要性。这些发现与椎间融合器的选择相关，但在应用于临床实践之前需要进一步研究，并且可能会影响未来椎间融合器的设计。
