Notani Naoki, Miyazaki Masashi, Kanezaki Shozo, Ishihara Toshinobu, Kawano Masanori, Tsumura Hiroshi
Department of Orthopaedic Surgery, Faculty of Medicine, Oita University, Oita, Japan.
Department of Orthopaedic Surgery, Faculty of Medicine, Oita University, Oita, Japan.
J Orthop Sci. 2017 Mar;22(2):207-212. doi: 10.1016/j.jos.2016.11.019. Epub 2016 Dec 23.
C1 lateral mass screws are increasingly being used as an effective anchoring system. Insufficient posterior arch height increases difficulty of inserting the screws using the Tan method. The general aim of our retrospective cross-sectional study was to clarify the atlas morphology of patients with developmental spinal canal stenosis to evaluate the usefulness of the Tan method.
A computed tomography myelogram was performed in 85 Japanese patients presenting with spinal disorders. The following morphological measures at the level of the atlas were obtained: anterior-posterior length (APL), medial-lateral width (MLW), lateral mass transverse diameter (LMTD), dural sac area (DSA), spinal cord area (SCA), lateral mass height (LMH), lateral mass width (LMW), lateral mass length (LML), posterior arch length (PAL), posterior lamina height (PLH), and posterior vertebral groove height (PVGH). Patients were classified into two groups: patients with developmental spinal canal stenosis (DCS), identified by a longitudinal diameter of the spinal canal <12 mm and patients without developmental spinal canal stenosis (NDCS), identified by a longitudinal diameter of the spinal canal ≥12 mm. Measures obtained on the computed tomography images were compared between the two groups.
Among the 85 patients in our study group, developmental spinal stenosis was identified in 47 patients. The APL, DSA, PAL and PVGH measurements were significantly smaller among the 47 patients in the DCS group, compared to the 38 patients in the NDCS group (p < 0.01). The mean height of the PVGH was <4.0 mm in 63.5% of the total study group.
The normally inserted C1 lateral mass screws have a diameter of 3.5-4.0 mm, and hence, the Tan method require a posterior arch height that exceeds this value. Our study provides evidence of a narrower posterior arch in Japanese individuals with developmental spinal canal stenosis. Therefore, the safe use of the Tan method to insert C1 lateral mass screws may be limited in Japanese individuals with developmental spinal canal stenosis.
C1侧块螺钉越来越多地被用作一种有效的锚固系统。后弓高度不足会增加使用Tan法插入螺钉的难度。我们这项回顾性横断面研究的总体目的是明确发育性椎管狭窄患者的寰椎形态，以评估Tan法的实用性。
对85例患有脊柱疾病的日本患者进行了计算机断层扫描脊髓造影。在寰椎水平获得了以下形态学测量值：前后径（APL）、内外侧宽度（MLW）、侧块横径（LMTD）、硬脊膜囊面积（DSA）、脊髓面积（SCA）、侧块高度（LMH）、侧块宽度（LMW）、侧块长度（LML）、后弓长度（PAL）、后椎板高度（PLH）和后椎沟高度（PVGH）。患者被分为两组：发育性椎管狭窄（DCS）患者，通过椎管纵径<12mm确定；无发育性椎管狭窄（NDCS）患者，通过椎管纵径≥12mm确定。比较两组在计算机断层扫描图像上获得的测量值。
在我们的研究组85例患者中，47例被确定为发育性脊柱狭窄。与NDCS组的38例患者相比，DCS组的47例患者的APL、DSA、PAL和PVGH测量值明显更小（p<0.01）。在整个研究组中，63.5%的患者PVGH平均高度<4.0mm。
正常植入的C1侧块螺钉直径为3.5 - 4.0mm，因此，Tan法需要后弓高度超过该值。我们的研究提供了证据，表明日本发育性椎管狭窄患者的后弓更窄。因此，对于日本发育性椎管狭窄患者，安全使用Tan法插入C1侧块螺钉可能会受到限制。
