Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
Department of Orthopaedic Surgery, HKU-Shenzhen Hospital, Shenzhen, China.
Spine Deform. 2023 Jul;11(4):887-895. doi: 10.1007/s43390-023-00679-w. Epub 2023 Apr 4.
Tether breakage is the most common complication of Vertebral Body Tethering (VBT) occurring in up to 52% of Adolescent Idiopathic Scoliosis (AIS) patients and risks continued progression and revision. Radiographical diagnosis of tether breakage is commonly defined by a 5° increase in inter-screw angle and associates breakage with loss of correction. However, the sensitivity of this method was 56% only, suggesting that tethers can break without an increase in angulation, which was supported by other studies. To our knowledge, current literature lacks a method merely focusing on the diagnosis of tether breakage radiographically that does not associate the breakages with loss of correction.
This was a retrospective review of prospectively collected data of AIS patients who underwent VBT. The "inter-screw index" is defined as the percentage increase in inter-screw distance since post-op, with ≥ 13% increase defined as tether breakage as suggested by our mechanical tests. CTs were reviewed to identify the breakages and compared with inter-screw angle and inter-screw index.
94 segments from 13 CTs were reviewed, and 15 tether breakages were identified. Use of inter-screw index correctly identified 14 breakages (93%), whereas ≥ 5° increase in inter-screw angle only identified 12 breakages (80%).
Use of inter-screw index is proven to be more sensitive than inter-screw angle in identifying tether breakages. Therefore, we propose the use of inter-screw index to diagnose tether breakages radiographically. Tether breakages were not necessarily accompanied by a loss of segmental correction leading to an increase in inter-screw angle, especially after skeletal maturity.
Level 3.
椎体拴系（VBT）最常见的并发症是拴系断裂，在青少年特发性脊柱侧凸（AIS）患者中发生率高达 52%，并增加进展和翻修的风险。拴系断裂的影像学诊断通常定义为螺钉间角度增加 5°，并与矫正丢失相关。然而，这种方法的敏感性仅为 56%，这表明即使没有角度增加，拴系也可能断裂，其他研究也支持这一观点。据我们所知，目前的文献缺乏一种仅专注于影像学诊断拴系断裂而不与矫正丢失相关联的方法。
这是一项对接受 VBT 的 AIS 患者前瞻性收集数据的回顾性研究。“螺钉间指数”定义为术后螺钉间距离的百分比增加，我们的机械测试建议螺钉间指数增加≥13%定义为拴系断裂。对 CT 进行回顾以识别断裂，并与螺钉间角度和螺钉间指数进行比较。
对 13 份 CT 中的 94 个节段进行了回顾，共发现 15 个拴系断裂。使用螺钉间指数正确识别了 14 个断裂（93%），而螺钉间角度增加≥5°仅识别了 12 个断裂（80%）。
螺钉间指数在识别拴系断裂方面的敏感性优于螺钉间角度。因此，我们建议使用螺钉间指数进行影像学诊断拴系断裂。拴系断裂不一定伴有节段矫正丢失，导致螺钉间角度增加，尤其是在骨骼成熟后。
3 级。
