Chen Zexing, Huang Xinzhao, Zou Xiaobao, Lian Peirong, Liu Guoqiang, Chen Junlin, Zhu Changrong, Ma Xiangyang
The First School of Clinical Medicine, Southern Medical University, Guangzhou, China.
Department of Orthopedics, General Hospital of Southern Theatre Command of PLA, Guangzhou, China.
Orthop Surg. 2025 Feb;17(2):437-445. doi: 10.1111/os.14309. Epub 2024 Dec 3.
To minimize the risk of V3 segment of vertebral artery (VA) injury in the atlantoaxial dislocation (AAD) patients with C1 pedicle height less than 4.0 mm and provide a strong toggle force in irreducible AAD and revision surgery. We evaluated the feasibility of C1 "Zero Angle" screw (C1ZAS) and safe entry point with "in-out-in" technique as an alternative option for C1 pedicle screw (PS) in cases with AAD.
Sixty-one patients with AAD or atlantoaxial instability (AAI) (45 male and 16 female) who underwent cervical computed tomography and magnetic resonance imaging scans in our center between January 1, 2022 and December 31, 2023 were retrospectively reviewed. Measurements were made around the ideal trajectory and entry point of C1ZAS using computerized tomography (CT) and magnetic resonance imaging (MRI) in 61 patients. Radiographic measurements included (A) the distance from the recess to the transverse foramen (RTF); (B) the tricortical screw zone (TSZ); (C) the lateral mass height along the C1ZAS trajectory (LMH); (D) the screw length of C1ZAS (ZSL); (E) the screw length of C1 PS (PSL); (F) the distances from the recess to the dura (RD); (G) the distance from the recess to the spinal cord (RSC); (H) the distance from the inner of lateral mass to the spinal cord (ILMSC). During the period of January 1, 2022 to December 31, 2023, C1ZAS placement with "in-out-in" technique was used as an alternative option for C1 PS in 8 patients with AAD and unilateral/bilateral narrow C1 pedicles.
The average RTF, TSZ, LMH, ZSL, RD, RSC, and ILMSC were 7.71, 6.14, 8.32, 33.23, 4.68, 10.02, and 2.91 mm respectively. The entry point of the C1ZAS was defined as the projection point of the inner of the recess to the posterior arch and the trajectory should be angled cephalad by 8.7° and medially by 0°. The 61 patients (122 sides) with AAD or AAI were classified into three groups: the low-risk (76 sides, 62%), the intermedial-risk (18 sides, 15%), and the high-risk (28 sides, 23%) groups. Satisfactory C1ZAS placement and atlantoaxial reduction were achieved in all eight patients with AAD and unilateral/bilateral narrow C1 pedicles. No instance of C1ZAS placement-related VA injury or dural laceration was observed.
When the placement of C1 PS is not feasible in patients with AAD and unilateral/bilateral narrow C1 pedicles, C1ZAS placement with "in-out-in" technique can be considered an effective alternative option, providing tricortical or quadricortical purchase for rigid fixation of the atlas.
将寰枢椎脱位（AAD）患者中椎动脉（VA）V3段损伤风险降至最低，这些患者的C1椎弓根高度小于4.0毫米，并在不可复位的AAD和翻修手术中提供强大的撑开力。我们评估了C1“零角度”螺钉（C1ZAS）及采用“进出进”技术的安全进针点作为AAD病例中C1椎弓根螺钉（PS）替代方案的可行性。
回顾性分析2022年1月1日至2023年12月31日期间在本中心接受颈椎计算机断层扫描和磁共振成像扫描的61例AAD或寰枢椎不稳（AAI）患者（45例男性，16例女性）。使用计算机断层扫描（CT）和磁共振成像（MRI）对61例患者C1ZAS的理想轨迹和进针点周围进行测量。影像学测量包括：（A）隐窝至横突孔的距离（RTF）；（B）三皮质螺钉区（TSZ）；（C）沿C1ZAS轨迹的侧块高度（LMH）；（D）C1ZAS的螺钉长度（ZSL）；（E）C1 PS的螺钉长度（PSL）；（F）隐窝至硬脑膜的距离（RD）；（G）隐窝至脊髓的距离（RSC）；（H）侧块内侧至脊髓的距离（ILMSC）。在2022年1月1日至2023年12月31日期间，8例AAD且C1椎弓根单侧/双侧狭窄的患者采用“进出进”技术置入C1ZAS作为C1 PS的替代方案。
平均RTF、TSZ、LMH、ZSL、RD、RSC和ILMSC分别为7.71、6.14、8.32、33.23、4.68、10.02和2.91毫米。C1ZAS的进针点定义为隐窝内侧至后弓的投影点，轨迹应向头侧成角8.7°，向内成角0°。61例AAD或AAI患者（122侧）分为三组：低风险组（76侧，62%）、中等风险组（18侧，15%）和高风险组（28侧，23%）。所有8例AAD且C1椎弓根单侧/双侧狭窄的患者C1ZAS置入及寰枢椎复位均满意。未观察到与C1ZAS置入相关的VA损伤或硬脑膜撕裂情况。
当AAD且C1椎弓根单侧/双侧狭窄患者无法置入C1 PS时，采用 “进出进” 技术置入C1ZAS可被视为一种有效的替代方案，可为寰椎提供三皮质或四皮质固定以实现坚强固定。
