经口咽入路枕骨髁螺钉置钉的影像学研究

Imaging study of transoral anterior occipital condylar screw placement

中文关键词:  枕骨髁  螺钉固定  经口咽  CT

英文关键词:Occipital condyle  Screw fixation  Transoral  CT

中文摘要:

  【摘要】 目的：探讨前路经口咽入路枕骨髁置钉的可行性及置钉的技术参数。方法：用Mimics软件对40例被检查者共80个枕骨髁的CT数据（层厚1mm）进行三维重建。女17例，男23例，年龄19~63岁，平均38.7岁；均无上颈椎手术史；CT扫描证实上颈椎结构完整，无上颈椎解剖畸形、感染、肿瘤、骨折。于枕骨髁的前方选定3个进钉点（中间点、内侧点、外侧点），中间进钉点位于寰椎侧块中线与枕骨大孔前缘水平线相交处，中间进钉点向两侧旁开5mm作为外侧进钉点及内侧进钉点。分别于各个进钉点模拟置入直径3.5mm枕骨髁螺钉。螺钉尾端位于枕骨髁与枕骨大孔连接处水平。比较各个进钉点间置钉成功率、螺钉长度及外倾角的安全范围。对于临床上具备可行性的进钉点，间隔1°调整进钉角度，比较不同角度置钉时置钉成功率的变化。结果：外侧进钉点置钉成功率为100%，螺钉长度为13.5~21.6mm，钉道外倾角度最小值为-19.5°~5.6°，最大值为-8.1°~24.9°；中间进钉点分别为88.6%，16.3~24.2mm，-4.1°~29.7°，12.6°~34.2°；内侧进钉点分别为72.5%，20.4~27.0mm，16.3°~40.3°，27.2°~44.8°；3个进钉点之间在置钉成功率、螺钉长度上均有显著性差异（P<0.01）。中间及外侧进钉点具备临床可行性，但没有固定的外倾角度可以满足所有螺钉安全置入，其中中间进钉点螺钉外倾20°达到最大的置钉成功率68.75%，而外侧进钉点平行矢状面置钉时达到最大置钉成功率80%。结论：经口咽前路枕骨髁置钉具备可行性，中间及外侧进钉点明显优于内侧进钉点，进钉点及钉道方向必须根据患者术前三维CT数据确定。

英文摘要:

  【Abstract】 Objectives: To investigate the feasibility and technical parameters of transoral anterior occipital condylar screw placement. Methods: Three dimensional reconstruction was performed in 80 occipital condyles of 40 cases by using 1mm sliced CT scans and MIMICS software. There were 17 females and 23 males with an average age of 38.7(range, 19-63). All of them had craniovertebral region intact. Infection and tumor were excluded in this study. 3 entry points(medial, middle and lateral) were selected. The middle entry point located at the cross junction of the foramen magnum and midline of atlas lateral mass. The medial and lateral entry points were located at 5mm medial and lateral to middle point respectively. Screw placement(3.5mm in diameter) was simulated at these three entry points. The end of the screw was located at the level of the junction of the occipital condyle and the rim of the foraman magnum. The screw length and safe range of extroversion among 3 entry points were compared. For the entry points available in clinical practice, the rate of successful screw placement for each degree of extroversion was compared. Results: The lateral entry point had the highest successful rate(100.0%) of screw placement with screw length of 13.5-21.6mm, minimum extroversion angle of (-19.5°)-5.6°, maximum extroversion angle of (-8.1°)-24.9°, and followed by the middle entry point of 88.6%, 16.3-24.2mm, (-4.1°)-29.7°, 12.6°-34.2°, respectively and medial entry point of 72.5%, 20.4-27.0mm, 16.3°-40.3°, 27.2°-44.8°, respectively. The three parameters for three entry points were significant different(P<0.01). It was difficult to recommend a general accepted extroversion angle. For the middle point, 20° extroversion angle had the highest successful rate of 68.75%. For the lateral entry point, paralleling to sagittal plane resulted in the successful screw placement in 80% of the cases. Conclusions: It is feasible to place transoral occipital condylar screw. The lateral and middle entry points are superior than the medial entry point. Determination of entry point and screw orientation must depend on preoperative 3-dimensional CT scan.