Department of Spinal Surgery, Nanfang Hospital, Southern Medical University, 1838 North Guangzhou Avenue, Guangzhou, China.
Department of Orthopaedic Surgery, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
Eur Spine J. 2019 Oct;28(10):2342-2351. doi: 10.1007/s00586-019-06039-5. Epub 2019 Jul 3.
A clivus screw and plate was invented and proved to strengthen the stability of the craniovertebral junction (CVJ). However, it is unclear whether the clivus screw and plate could be placed onto the CVJ by transoral approach. Therefore, the present study aims to evaluate the feasibility of clivus screw and plate placement by transoral approach and investigate its relative anatomic parameters.
A total of 80 normal adults (40 males/40 females) with an average age of 60.4 ± 11.6 years old were enrolled in this study. All parameters were measured in a supposed maximums mouth-opening status on computed tomography images, where the vertex of lower incisor was defined as Point A. The vertical intersection from Point A to extracranial clivus was defined as Point B, and its distance to the bottom of clivus was measured as B length. Point B was considered as ideal screw entry point. All the cases were divided into three types based on the location of Point B: above the top portion (Type 1), between the top and bottom portion (Type 2), and below the bottom portion (Type 3) of extracranial clivus. The B Length was defined as a minus value if the case belonged to Type 3. The anterior skull base angle, the angles between tangent of extracranial clivus and the lines from Point A to different parts of clivus, and distances between Point A and clivus and C1-3 vertebra were also measured.
One in eighty cases (1.2%) belonged to Type 1 with a B Length of 32.12 mm. Most cases (61.3%) were Type 2 with a B Length of 8.7 mm, while Type 3's was - 9.7 mm occupying for 37.5%. Significant statistic differences were found in anterior skull base angle between these three types (128.9°, 122.7° and 118.5° for Type 1, 2 and 3, respectively). The distances from Point A to the top and bottom portion of the clivus and the pharyngeal tubercle were 97.5, 96.0 and 96.8 mm, respectively. The angles between the tangent of the clivus and the lines from Point A to the above three structures were 75.7°, 92.3° and 84.0°, respectively. The distances from Point A to the middle point of anterior margin of C1 anterior tubercle, C2 vertebra and C3 vertebra were 79.1, 73.4 and 61.5 mm, respectively.
The clivus screw and plate placement could be accomplished with optimal screw angle by transoral approach in most of patients. Mandibular splitting would be needed in patients with greater anterior skull angle. These slides can be retrieved under Electronic Supplementary Material.
寰枢椎后路经口寰枢椎侧块钉板固定系统的临床应用及相关解剖学研究。
80 例正常成人（男 40 例，女 40 例），年龄 60.4±11.6 岁。在最大张口位 CT 上测量各项解剖学参数。以切牙顶点为 A 点，A 点到颅外板的垂线交点为 B 点，B 点到颅底的距离为 B 长度。B 点为理想的进钉点，根据 B 点在颅外板的位置将病例分为 3 型：B 点位于颅外板上 1/3（A型）、中外 1/3（B 型）、颅外板下 1/3（C 型）。B 长度为负值表示 C 型。测量前颅底角，颅外板切线与 A 点至枢椎各点连线的夹角，A 点到枢椎及 C1-3 椎体的距离。
A型 1 例（1.2%），B 长度 32.12mm；B 型 49 例（61.3%），B 长度 8.7mm；C 型 29 例（36.5%），B 长度-9.7mm。3 型间前颅底角差异有统计学意义（128.9°、122.7°、118.5°）。A 点到颅底、颅外板上缘、咽结节的距离分别为 97.5mm、96.0mm、96.8mm；A 点到上述 3 点连线与颅外板切线的夹角分别为 75.7°、92.3°、84.0°。A 点到寰椎前结节中点、枢椎椎体中点、C3 椎体中点的距离分别为 79.1mm、73.4mm、61.5mm。
经口寰枢椎后路侧块钉板固定系统固定在大多数患者中可获得理想的置钉角度。对于前颅底角度较大的患者，可能需要行下颌骨劈开。可在补充材料中查看幻灯片。
