Kienle Annette, Graf Nicolas, Tao Youping, Heuer Frank
Medical Device Testing, SpineServ GmbH & Co. KG, Ulm, DEU.
Spine Surgery, SpineServ GmbH & Co. KG, Ulm, DEU.
Cureus. 2023 Mar 29;15(3):e36845. doi: 10.7759/cureus.36845. eCollection 2023 Mar.
Background Anterior cage migration in anterior lumbar interbody fusion is a serious complication. To address this risk, cage designs are now available with integrated screw or blade fixation or specially designed surface geometries with large teeth or ridges. However, the implantation technique itself has not yet been addressed as a potential risk factor for cage migration. This study aimed to investigate whether a cage that is implantable without gouging the vertebral endplates has improved resistance to anterior migration. Methodology A novel three-piece modular cage was inserted between two vertebral body replacements (polyurethane (PU) foam grade 15 pcf) in two ways. In group 1 (modular), the cage was inserted in a wedge within a wedge fashion according to the manufacturer's instructions such that damage to the PU foam was minimized. In group 2 (mono-bloc), the modular cage was inserted pre-assembled as a one-piece, mono-bloc device. This insertion method required impaction and increased the potential of gouging the PU surfaces. Then, an axial preload was applied to the PU test blocks to simulate the preload on the spine in vivo and an anteriorly direct expulsion force was applied to the cages. Results The mean expulsion yield load in the test group with modular implantation was 392 ± 19 N compared to 287 ± 16 N in the test group where the mono-bloc implants were inserted and endplate gouging occurred. This difference was statistically significant (p < 0.05). Thus, the onset of cage migration occurred at significantly higher loads in the test group with modular insertion without endplate gouging compared to one-piece impaction with gouging taking place. In contrast, the stiffness and the ultimate load were similar in both test groups (p > 0.05). Conclusions This study showed that the cage insertion technique may have a significant effect on the cage migration risk. Prevention of endplate gouging during cage implantation has the potential to improve the primary stability of the cage.
腰椎前路椎间融合术中椎间融合器向前移位是一种严重的并发症。为应对这一风险，现在有了集成螺钉或刀片固定的椎间融合器设计，或具有大齿或脊的特殊设计表面几何形状。然而，植入技术本身尚未被视为椎间融合器移位的潜在风险因素。本研究旨在调查一种无需刮伤椎体终板即可植入的椎间融合器是否具有更好的抗向前移位能力。
一种新型三件式模块化椎间融合器以两种方式插入两个椎体替代物（15 pcf 聚氨酯（PU）泡沫）之间。在第 1 组（模块化）中，根据制造商的说明以楔内楔的方式插入椎间融合器，以使对 PU 泡沫的损伤最小化。在第 2 组（一体式）中，将模块化椎间融合器预先组装成一体式装置插入。这种插入方法需要冲击，增加了刮伤 PU 表面的可能性。然后，对 PU 测试块施加轴向预载荷以模拟体内脊柱上的预载荷，并对椎间融合器施加向前的直接推力。
模块化植入测试组的平均推出屈服载荷为 392±19 N，而一体式植入且发生终板刮伤的测试组为 287±16 N。这种差异具有统计学意义（p<0.05）。因此，与发生刮伤的一体式冲击相比，在无终板刮伤的模块化插入测试组中，椎间融合器移位的起始载荷明显更高。相比之下，两组测试的刚度和极限载荷相似（p>0.05）。
本研究表明，椎间融合器植入技术可能对椎间融合器移位风险有显著影响。在椎间融合器植入过程中防止终板刮伤有可能提高椎间融合器的初始稳定性。
