Department of Spinal Surgery, Ningbo No. 6 Hospital, Zhejiang Province, China.
J Neurosurg Spine. 2013 Apr;18(4):372-7. doi: 10.3171/2013.1.SPINE12724. Epub 2013 Feb 1.
The aims of this study were to evaluate a large series of posterior C-1 lateral mass screws (LMSs) to determine accuracy based on CT scanning findings and to assess the perioperative complication rate related to errant screw placement.
Accuracy of screw placement was evaluated using postoperative CT scans obtained in 196 patients with atlantoaxial instability. Radiographic analysis included measurement of preoperative and postoperative CT scans to evaluate relevant anatomy and classify accuracy of instrumentation placement. Screws were graded using the following definitions: Type I, screw threads completely within the bone (ideal); Type II, less than half the diameter of the screw violates the surrounding cortex (safe); and Type III, clear violation of transverse foramen or spinal canal (unacceptable).
A total of 390 C-1 LMSs were placed, but 32 screws (8.2%) were excluded from accuracy measurements because of a lack of postoperative CT scans; patients in these cases were still included in the assessment of potential clinical complications based on clinical records. Of the 358 evaluable screws with postoperative CT scanning, 85.5% of screws (Type I) were rated as being in the ideal position, 11.7% of screws (Type II) were rated as occupying a safe position, and 10 screws (2.8%) were unacceptable (Type III). Overall, 97.2% of screws were rated Type I or II. Of the 10 screws that were unacceptable on postoperative CT scans, there were no known associated neurological or vertebral artery (VA) injuries. Seven unacceptable screws erred medially into the spinal canal, and 2 patients underwent revision surgery for medial screws. In 2 patients, unilateral C-1 LMSs penetrated the C-1 anterior cortex by approximately 4 mm. Neither patient with anterior C-1 penetration had evidence of internal carotid artery or hypoglossal nerve injury. Computed tomography scanning showed partial entry of C-1 LMSs into the VA foramen of C-1 in 10 cases; no occlusion, associated aneurysm, or fistula of the VA was found. Two patients complained of postoperative occipital neuralgia. This was transient in one patient and resolved by 2 months after surgery. The second patient developed persistent neuralgia, which remained 2 years after surgery, necessitating referral to the pain service.
The technique for freehand C-1 LMS fixation appears to be safe and effective without intraoperative fluoroscopy guidance. Preoperative planning and determination of the ideal screw insertion point, the ideal trajectory, and screw length are the most important considerations. In addition, fewer malpositioned screws were inserted as the study progressed, suggesting a learning curve to the technique.
本研究旨在评估大量后路 C1 侧块螺钉（LMS），通过 CT 扫描结果评估其准确性，并评估与螺钉位置不当相关的围手术期并发症发生率。
对 196 例寰枢椎不稳定患者进行术后 CT 扫描，评估螺钉放置的准确性。影像学分析包括测量术前和术后 CT 扫描，以评估相关解剖结构并对仪器放置的准确性进行分类。螺钉根据以下定义进行分级：I 型，螺钉螺纹完全在骨内（理想）；II 型，不到螺钉直径的一半破坏周围皮质（安全）；III 型，明显侵犯横突孔或椎管（不可接受）。
共放置了 390 枚 C1 LMS，但由于缺乏术后 CT 扫描，32 枚螺钉（8.2%）被排除在准确性测量之外；在这些情况下，仍根据临床记录评估潜在的临床并发症。在有术后 CT 扫描的 358 枚可评估螺钉中，85.5%（I 型）的螺钉被评为理想位置，11.7%（II 型）的螺钉被评为安全位置，10 枚（2.8%）的螺钉不可接受（III 型）。总的来说，97.2%的螺钉被评为 I 型或 II 型。在术后 CT 扫描中不可接受的 10 枚螺钉中，没有与神经或椎动脉（VA）损伤相关的已知关联。7 枚不可接受的螺钉向内侧进入椎管，2 例患者因内侧螺钉行翻修手术。在 2 例患者中，单侧 C1 LMS 穿透 C1 前皮质约 4mm。无 1 例 C1 前皮质穿透患者出现颈内动脉或舌下神经损伤的证据。CT 扫描显示 10 例 C1 LMS 部分进入 C1 横突孔；未发现 VA 孔闭塞、相关动脉瘤或 VA 瘘。2 例患者诉术后枕部神经痛。1 例患者为一过性，术后 2 个月缓解。第 2 例患者出现持续性神经痛，术后 2 年仍存在，需要转至疼痛科。
徒手 C1 LMS 固定技术似乎是安全有效的，无需术中透视引导。术前计划和确定理想的螺钉插入点、理想的轨迹和螺钉长度是最重要的考虑因素。此外，随着研究的进展，插入的错位螺钉数量减少，表明该技术存在学习曲线。
