Abstract：
The Zero-P spacer was primarily developed aiming to reduce the morbidity associated with the traditional anterior cervical plate. During the past decade, many authors have reported the use of Zero-P spacers for anterior cervical discectomy and fusion (ACDF) of one or two segments. Nevertheless, there is still a paucity of knowledge on the safety and feasibility of using Zero-P spacers for 3-level fixation. The objective of this study was to investigate the clinical and radiological outcomes, with a focus on the sagittal alignment reconstruction of 3-level ACDF surgery using Zero-P spacers versus those using a traditional plate and cage system. From Sep 2013 to Aug 2016, a total of 44 patients who received 3-level ACDF surgery due to cervical spondylotic myelopathy were recruited. The Zero-P spacer was used in 23 patients (group ZP) and the traditional plate and cage system in 21 (group PC). Clinical outcomes were analyzed by Neck Disability Index (NDI) and Japanese Orthopedic Association (JOA) scores, and dysphagia was evaluated using the Bazaz score. Radiological outcomes, including fusion rate, adjacent segment degeneration (ASD), and especially changes in cervical sagittal alignment, were analyzed. The NDI and JOA scores did not differ significantly between the two groups postoperatively (p > 0.05); however, there was significantly less dysphagia in patients using Zero-P spacers at the 3- and 6-month follow-up (p < 0.05). At the 24-month follow-up, the fusion rate and ASD were similar between the two groups (p > 0.05). Interestingly, patients using Zero-P spacers had a significantly lower postoperative C2-7 Cobb angle and fused segment Cobb angle, compared to those using a traditional plate and cage system (p < 0.05); meanwhile, the fused segment disc wedge was also found to be significantly smaller in patients using Zero-P spacers after surgery (p < 0.05). Moreover, we further divided patients into subgroups according to their cervical lordosis. In patients with a preoperative C2-7 Cobb angle ≤ 10°, significantly less cervical and local lordosis, as well as disc wedge, were seen in group ZP after surgery (p < 0.05), while in others with a preoperative C2-7 Cobb angle > 10°, no significant difference in postoperative changes of the cervical sagittal alignment was seen between group ZP and group PC (p > 0.05). Zero-P spacers used in 3-level ACDF surgery could provide equivalent clinical outcomes and a lower rate of postoperative dysphagia, compared to the traditional plate and cage system. However, our results showed that it was inferior to the cervical plate in terms of sagittal alignment reconstruction for 3-level fixation. We recommend applying Zero-P spacers for 3-level ACDF in patients with good preoperative cervical lordosis (C2-7 Cobb angle > 10°), in order to restore and maintain physiological curvature of the cervical spine postoperatively.
摘要：
Zero-P间隔器的主要开发目的是降低与传统颈椎前板相关的发病率。在过去的十年里，许多作者报道了Zero-P间隔器用于颈椎前路椎间盘切除和融合（ACDF）的一个或两个节段。然而，关于使用Zero-P垫片进行3级固定的安全性和可行性的知识仍然很少。这项研究的目的是调查临床和放射学结果，重点是使用Zero-P垫片与使用传统板和笼系统的3级ACDF手术的矢状对齐重建。从2013年9月至2016年8月，共招募了44例因脊髓型颈椎病而接受3级ACDF手术的患者。23例患者（ZP组）使用Zero-P垫片，21例（PC组）使用传统的板和笼系统。通过颈部残疾指数（NDI）和日本骨科协会（JOA）评分分析临床结果，使用Bazaz评分评估吞咽困难。放射学结果，包括融合率，相邻节段变性（ASD），尤其是颈椎矢状位的变化，进行了分析。两组术后NDI和JOA评分无显著差异(p>0.05);在随访3个月和6个月时,使用Zero-P间隔器的患者吞咽困难明显减少(p<0.05).在24个月的随访中，两组间融合率和ASD相似(p>0.05)。有趣的是,使用Zero-P垫片的患者术后C2-7Cobb角和融合节段Cobb角明显降低，与使用传统板笼系统的系统相比(p<0.05)；同时，术后使用Zero-P垫片的患者融合节段椎间盘楔形也明显变小(p<0.05)。此外，我们根据患者的宫颈前凸度进一步将患者分为亚组。术前C2-7Cobb角≤10°的患者，宫颈和局部脊柱前凸明显减少，以及圆盘楔，ZP组在手术后观察到（p＆lt;0.05），而在其他术前为C2-7Cobb角>10°的情况下，ZP组和PC组术后颈椎矢状位变化无明显差异（p＆gt;0.05）。在3级ACDF手术中使用的零P间隔器可以提供同等的临床结果和较低的术后吞咽困难率，与传统的板笼系统相比。然而,我们的结果表明，在3级固定的矢状面对齐重建方面，它不如颈椎钢板。我们建议在术前宫颈前凸良好（C2-7Cobb角＆gt;10°）的患者中应用Zero-P垫片用于3级ACDF，以恢复和维持颈椎术后的生理曲度。
