Jin Michael, Asadoorian Mariet, Hiller Lucas P, Hughes Tudor H
Department of Radiology, University of California San Diego School of Medicine, 200 W. Arbor Drive, San Diego, CA 92103, USA.
Department of Radiology, University of California San Diego School of Medicine, 200 W. Arbor Drive, San Diego, CA 92103, USA.
Spine J. 2014 Jul 1;14(7):1155-8. doi: 10.1016/j.spinee.2013.07.482. Epub 2013 Nov 5.
Nonunion of the posterior arch of the atlas is an uncommon but normal developmental variant. It is usually asymptomatic in the patient but may be associated with greater incidence of fracture because of increased stress on the anterior arch.
We sought to determine whether anterior arch hypertrophy is present in cases of congenital nonunion of the posterior arch of the atlas.
STUDY DESIGN/SETTING: A retrospective analysis of 1 year (February 2005-January 2006) of computed tomography cervical spine studies requested by the University of California San Diego Medical Center Trauma Department was undertaken.
All patients matching the search criteria (see Study design) were included.
Area density product, defined as the midline cross-sectional area of the anterior arch on sagittal reformat multiplied by the average areal radiodensity in Hounsfield units (HU) as measured by two raters, was calculated for cases and controls.
Cases of posterior arch nonunion were identified and matched to controls. The significance of differences in area density product between cases and controls were established by the Student t test. Interrater correlation was calculated.
Posterior arch nonunion was identified in 26 individuals (3.1% of 839 studies reviewed). Compared with age- and sex-matched controls, a 21% increase in area density product of the midline anterior arch was observed in posterior arch nonunion cases (773 HU-cm2 in cases vs. 637 HU-cm2 in controls; p<.001). This increase was attributable to a 21% increase in cross-sectional area (1.05 cm2 in cases vs. 0.87 cm2 in controls; p<.002). In contrast, there was no significant difference with regard to increased average radiodensity.
It has long been subjectively recognized but not objectively quantified, until the present study, that the anterior arch of the atlas is hypertrophied in cases of posterior arch nonunion. Anterior arch hypertrophy may represent an adaptive response to chronically elevated mechanical stress and loss of hoop strength in cases of posterior nonunion.
寰椎后弓不连是一种罕见但正常的发育变异。患者通常无症状，但由于前弓应力增加，可能与骨折发生率增加有关。
我们试图确定先天性寰椎后弓不连病例中是否存在前弓肥大。
研究设计/地点：对加利福尼亚大学圣地亚哥分校医学中心创伤科在2005年2月至2006年1月期间要求进行的1年颈椎计算机断层扫描研究进行回顾性分析。
纳入所有符合搜索标准（见研究设计）的患者。
计算病例组和对照组的面积密度乘积，定义为矢状面重建上前弓的中线横截面积乘以两名评估者测量的平均面积放射密度（亨氏单位，HU）。
识别后弓不连病例并与对照组匹配。通过学生t检验确定病例组和对照组面积密度乘积差异的显著性。计算评估者间的相关性。
在839项研究中，有26例（3.1%）被确定为后弓不连。与年龄和性别匹配的对照组相比，后弓不连病例的中线前弓面积密度乘积增加了21%（病例组为773HU-cm²，对照组为637HU-cm²；p<0.001）。这种增加归因于横截面积增加了21%（病例组为1.05cm²，对照组为0.87cm²；p<0.002）。相比之下，平均放射密度增加没有显著差异。
长期以来，人们一直主观地认识到，但直到本研究才客观量化，寰椎后弓不连病例中前弓肥大。前弓肥大可能代表了对后弓不连情况下长期升高的机械应力和环向强度丧失的适应性反应。
