Molina Camilo, Sciubba Daniel M, Chaput Christopher, Tortolani P Justin, Jallo George I, Kretzer Ryan M
Department of Neurosurgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
J Neurosurg Pediatr. 2012 Jan;9(1):27-34. doi: 10.3171/2011.10.PEDS11121.
Translaminar screws (TLSs) were originally described as a safer alternative to pedicle and transarticular screw placement at C-2 in adult patients. More recently, TLSs have been used in both the cervical and thoracic spine of pediatric patients as a primary fixation technique and as a bailout procedure when dysplastic pedicle morphology prohibits safe pedicle screw placement. Although authors have reported the anatomical characteristics of the cervical and thoracic lamina in adults as well as those of the cervical lamina in pediatric patients, no such data exist to guide safe TLS placement in the thoracic spine of the pediatric population. The goal of this study was to report the anatomical feasibility of TLS placement in the thoracic spine of pediatric patients.
Fifty-two patients (26 males and 26 females), with an average age of 9.5 ± 4.8 years, were selected by retrospective review of a trauma registry database after institutional review board approval. Study inclusion criteria were an age from 2 to 16 years, standardized axial bone-window CT images of the thoracic spine, and the absence of spinal trauma. For each thoracic lamina the following anatomical features were measured using eFilm Lite software: laminar width (outer cortical and cancellous), laminar height (LH), maximal screw length, and optimal screw trajectory. Patients were stratified by age (an age < 8 versus ≥ 8 years) and sex.
Collected data demonstrate the following general trends as one descends the thoracic spine from T-1 to T-12: 1) increasing laminar width to T-4 followed by a steady decrease to T-12, 2) increasing LH, 3) decreasing maximal screw length, and 4) increasing ideal screw trajectory angle. When stratified by age and sex, male patients older than 8 years of age had significantly larger laminae in terms of both width and height and allowed significantly longer screw placement at all thoracic levels compared with their female counterparts. Importantly, it was found that 78% of individual thoracic laminae, regardless of age or sex, could accept a 4.0-mm screw with 1.0 mm of clearance. As expected, when stratifying by age and sex, it was found that older male patients had the highest acceptance rates.
Data in the present study provide information regarding optimal TLS length, diameter, and trajectory for each thoracic spinal level in pediatric patients. Importantly, the data collected demonstrate no anatomical limitations within the pediatric thoracic spine to TLS instrumentation, although acceptance rates are lower for younger (< 8 years old) and/or female patients. Lastly, given the anatomical variation found in this study, CT scanning can be useful in the preoperative setting when planning TLS use in the thoracic spine of pediatric patients.
经椎板螺钉（TLS）最初被描述为成年患者C2节段椎弓根螺钉和经关节突螺钉置入的一种更安全的替代方法。最近，TLS已被用于小儿患者的颈椎和胸椎，作为一种主要的固定技术，以及在发育不良的椎弓根形态禁止安全的椎弓根螺钉置入时作为一种补救措施。尽管已有作者报道了成人颈椎和胸椎椎板以及小儿患者颈椎椎板的解剖特征，但尚无此类数据可指导小儿胸椎TLS的安全置入。本研究的目的是报告小儿胸椎TLS置入的解剖学可行性。
在机构审查委员会批准后，通过回顾性审查创伤登记数据库，选择了52例患者（26例男性和26例女性），平均年龄为9.5±4.8岁。研究纳入标准为年龄在2至16岁之间、胸椎的标准化轴向骨窗CT图像以及无脊柱创伤。使用eFilm Lite软件测量每个胸椎椎板的以下解剖特征：椎板宽度（外层皮质和松质骨）、椎板高度（LH）、最大螺钉长度和最佳螺钉轨迹。患者按年龄（年龄＜8岁与≥8岁）和性别分层。
收集的数据显示，当从T1至T12沿胸椎向下时呈现以下一般趋势：1）椎板宽度增加至T4，随后稳定下降至T12；2）LH增加；3）最大螺钉长度减小；4）理想螺钉轨迹角度增加。按年龄和性别分层时，8岁以上男性患者的椎板在宽度和高度方面均明显大于女性患者，并且在所有胸椎节段允许置入的螺钉明显更长。重要的是，发现无论年龄或性别，78%的单个胸椎椎板可容纳直径4.0 mm且有1.0 mm间隙的螺钉。正如预期的那样，按年龄和性别分层时，发现年龄较大的男性患者接受率最高。
本研究中的数据提供了小儿患者每个胸椎节段最佳TLS长度、直径和轨迹的信息。重要的是，收集的数据表明小儿胸椎内对TLS器械置入无解剖学限制，尽管年龄较小（＜8岁）和/或女性患者的接受率较低。最后，鉴于本研究中发现的解剖学变异，在术前计划小儿胸椎TLS使用时，CT扫描可能会有所帮助。
