Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Sungnam, Republic of Korea.
Spine (Phila Pa 1976). 2010 Jul 15;35(16):1562-70. doi: 10.1097/BRS.0b013e3181c15a84.
Radiologic evaluation of computed tomography (CT) scans using screw insertion simulation software.
To investigate the optimal entry point and trajectory of atlantooccipital transarticular screws.
To our knowledge, no large series focusing on the placement of atlantooccipital transarticular screws have been published.
We used 1.0-mm sliced CT scans and 3-dimensional screw trajectory software to simulate 4.0-mm screw placement. Four entry points were evaluated. Screw placement success rate, safe range of medial angulation, and screw length using each entry point were determined.
CT scans of 126 patients were evaluated, for a total of 252 screws for each entry point. On simulation, the 2 lateral entry points showed significantly higher success rates and safe range of medial angulation than the 2 middle points. The 2 lateral entry points had similar success rates (98.0% for anteriolateral (AL) point and 97.6% for posteriolateral (PL) point). Although the safe range of medial angulation was significantly wider for the AL point (26.1 degrees) than for the PL point (23.7 degrees), the screw lengths were significantly longer for the PL point (32.6 mm) than for the AL point (29.4 mm). For both points, 30 degrees of medial angulation led to highest rate of successful screw placement, but the rate was only 79.4% and 80.2%, respectively.
Although there was no significant difference in success rates between AL and PL points, PL is likely the best entry point. Although 30 degrees medial and approximately 5 degrees upward angulation led to the highest rate of successful screw placement, the rate was only around 80%. Given the wide individual variation, we recommend that a preoperative 3-dimensional CT scan be obtained when attempting atlantooccipital transarticular screw fixation.
使用螺钉插入模拟软件对计算机断层扫描（CT）进行影像学评估。
探讨寰枕经关节螺钉的最佳进钉点和进钉轨迹。
据我们所知，目前尚无专门针对寰枕经关节螺钉置钉的大型研究系列报道。
我们使用 1.0mm 层厚的 CT 扫描和三维螺钉轨迹软件来模拟 4.0mm 螺钉的置入。评估了 4 个进钉点。确定了每个进钉点的螺钉置入成功率、内侧成角的安全范围和螺钉长度。
共评估了 126 例患者的 CT 扫描，每个进钉点共有 252 枚螺钉。模拟结果显示，2 个侧方进钉点的成功率和内侧成角的安全范围明显高于 2 个中间进钉点。2 个侧方进钉点的成功率相似（前外侧点为 98.0%，后外侧点为 97.6%）。虽然前外侧点的内侧成角安全范围（26.1°）明显大于后外侧点（23.7°），但后外侧点的螺钉长度（32.6mm）明显长于前外侧点（29.4mm）。对于这两个点，30°的内侧成角可使螺钉置入成功率最高，但成功率分别仅为 79.4%和 80.2%。
虽然前外侧点和后外侧点的成功率无显著差异，但后外侧点可能是最佳进钉点。虽然 30°的内侧和大约 5°的向上成角可使螺钉置入成功率最高，但成功率仅在 80%左右。鉴于个体差异较大，我们建议在尝试寰枕经关节螺钉固定时，应进行术前三维 CT 扫描。
