Axis vertebral dimensions for safe screw placement: A CT normative data analysis

IntroductionMorphometric evaluation of the pedicle and isthmus of second cervical vertebra (C2) (Axis) is extremely vital before contemplating any surgical stabilization involving the Craniovertebral region, in view of its proximity to the vertebral artery and the cervical nerve root. The dimensions of pedicles and isthmuses in C2 vary between individuals and there is paucity of data in the Indian population. This study strives to measure the average pedicle and isthmus dimensions in a sample of population, which would enable selection of screws with safest diameters to be used in C2; thereby avoiding injury to adjacent neurovascular structures.Materials and methodsOne Hundred patients in the age group between 18 and 70 years who underwent CT scan of head and neck region were included in the study. The aim of this study was to assess the anatomic suitability of transarticular and pedicle screw placement in Axis vertebrae of Indian population and determine the maximum safe diameter for screw placement. The following parameters were measured in millimeters: Pedicle width, Pedicle angle, Internal height and Isthmic height.ResultsThe Mean maximum diameter of potential pedicle screw was 4.99 ± 1.1 mm for the right side with the left side being slightly wider at 5.20 ± 1.16 mm. Twenty eight (28%; 56 out of 200 pedicles) had a measurement < 4.5 mm. The internal height in sagittal images representing the pedicle height was found to be 4.79 ± 0.96 mm on the right side and 4.75 ± 1.04 mm on the left side. Sixty five (65) out of 200 pedicles (32.5%) had measurements < 4.5 mm in sagittal plane. The Mean maximum diameter of potential Transarticular screw (outer diameter of isthmus) was 5.05 ± 0.78 mm for the right side and 5.18 ± 0.84 mm on the left side.DiscussionIsthmic height < 4.5 mm could potentially violate the vertebral foramen when a 3.5 mm screw is used. In our study 22.5% isthmuses were narrow (<4.5 mm). The mean maximum safe diameter for a potential transarticular screw in the present study was 5.11 mm. Though our patients had smaller isthmus dimensions compared with literature, 77.5% of C2 could take a 4 mm transarticular screw quite comfortably considering the 0.5 mm margin on either side. In the present study, 28% of pedicles were found to be inappropriately sized (<4.5 mm) to accommodate the standard 3.5 mm screw. The mean maximum diameter of a potential pedicle screw in our study was 5.09 mm; and in 72% of patients a 4 mm screw could be placed with confidence. Though our patients on an average can accommodate a 4 mm screw comfortably, we suggest a protocol of obtaining CT measurements of C2 prior to operative intervention for identifying those individuals at risk of neurovascular injury; 22.5% for transarticular screw and 28% for pedicle screw.     

寰椎椎板钩联合枢椎椎弓根螺钉治疗寰枢椎失稳的临床疗效

目的探讨后路寰椎椎板钩联合枢椎椎弓根螺钉技术治疗寰枢椎失稳的临床疗效。方法 2009年12月-2012年12月,行后路寰椎椎板钩联合枢椎椎弓根螺钉固定技术的寰枢椎失稳患者,有效随访资料36例,其中男26例,女10例;年龄21-66岁,平均42.3岁;有脊髓损伤症状者28例,日本骨科学会（Japanese Orthopaedic Association,JOA）评分9.3±1.8;有颈枕区疼痛症状者30例,颈枕区视觉模拟量表（visual analog scale,VAS）评分3.9±1.1;36例患者颈椎障碍功能指数（neck disability index,NDI）术前27.6±8.3;有发作性眩晕症状者6例;寰枢椎脱位26例,术前均行颅骨牵引术并达到复位。结果所有患者均顺利完成手术。术中出血量为80-600 mL,平均295 mL;手术时间95-210 min,平均157 min。术后随访个6-42个月,平均21个月,35例术后6月获得融合,影像学检查可见连续骨小梁,植骨融合率97.2%。末次随访JOA评分改善至13.7±2.0,平均改善率58%;术后VAS评分1.8±0.9;NDI降低至12.9±6.4。JOA评分、VAS评分和NDI评分术前与术后对比差异均具有统计学意义（P〈0.05）。术中未出现椎动脉、脊髓神经损伤或脑脊液漏等并发症。随访期间未发现椎板钩脱位、松动,6例有发作性眩晕患者眩晕症状消失。结论寰椎椎板钩联合枢椎椎弓根螺钉技术手术操作简单、风险低,手术时间短,有良好临床的效果,可作为治疗寰枢椎失稳的一种选择。     

Effects of prenatal ethanol exposure on hypothalamic-pituitary-adrenal responses to chronic cold stress in rats

Animals prenatally exposed to ethanol typically exhibit hypothalamic-pituitary-adrenal (HPA) hyperresponsiveness to stressors. In contrast to previous studies that have investigated effects of prenatal ethanol exposure on HPA responses to acute or intermittent stressors, our study investigated HPA responses to a chronic continuous stressor, cold stress (4 degrees C for 0, 1, or 3 days). We tested the hypothesis that prenatal ethanol exposure would result in increased plasma corticosterone (CORT) and adrenocorticotropin (ACTH) responses and increased peptide [corticotropin-releasing factor and vasopressin] mRNA levels in the paraventricular nucleus (PVN) of the hypothalamus compared to that in control animals. In addition, CORT and ACTH responses were measured after exposure to an acute stressor (i.p. isotonic saline injection), superimposed during chronic cold exposure, to examine possible sensitization of the HPA response to the acute stress. Thus, blood samples were collected at the end of each of the three periods of cold exposure, either before (0 min) or 15 min after acute stress. The subjects were adult male and female Sprague-Dawley rat offspring from prenatal ethanol (E), pair-fed (PF), and ad libitum-fed control (C) treatment groups. Exposure to cold stress resulted in significant body weight loss in E males at 1 day and in both males and females of all prenatal treatment groups by 3 days of cold stress. Males in all prenatal groups also exhibited significant increases in adrenal weight:body weight ratios. Cold stress alone (0 min condition) increased CORT levels in E males and overall ACTH levels in E males and females compared to controls. ACTH levels were also higher overall in E compared to control males after acute stress (15 min condition). Sensitization of the CORT response to acute stress was observed in males but not females across all prenatal treatment groups. Corticotropin-releasing factor and vasopressin mRNA levels in the PVN were not significantly affected by prenatal treatment or chronic cold stress in either males or females. In contrast, both males and females displayed increases in PVN thyrotropin-releasing hormone (TRH) mRNA levels after cold stress. These data support and extend previous work demonstrating differential effects of prenatal ethanol exposure on HPA responsiveness of male and female offspring, and suggest that E males may be more vulnerable to the effects of chronic cold stress than E females.     

The spiral axis as a clinical tool to distinguish essential tremor from dystonia cases

BackgroundTremor is a common feature of a variety of neurological disorders. In genetic studies of essential tremor (ET), investigators need to screen potential enrollees by mail or telephone to exclude those with other neurological conditions, especially dystonia. In clinical settings, the differentiation of ET and dystonia may also be very challenging. We hypothesized that the spiral axis, described below, is a useful screening tool to distinguish ET cases from dystonia cases.MethodsWe analyzed the hand-drawn spirals of 135 individuals enrolled in a genetics study at Columbia University Medical Center. Each of the four spirals was assessed for the presence of a single identifiable tremor orientation axis, and a spiral axis score (range = 0–4) [a single axis on all 4 spirals] was assigned to each enrollee.ResultsThere were 120 ET cases and 15 cases with dystonic tremor. Most (101/120, 84.2%) ET cases had an axis score ≥1 vs. only half (8/15, 53.3%) of the dystonia cases (p = 0.02). Receiver Operator Curve (ROC) analysis revealed that the use of a spiral axis score ≥2 as a cut off would exclude 60.0% of dystonia cases while including 67.5% of ET cases.ConclusionHandwritten spirals appear to have a single predominant axis in more ET than dystonia cases. The evaluation of this axis has moderate diagnostic validity as a screening tool to distinguish ET cases from those with dystonia. Although this study did not assess the utility of this tool in clinical practice settings, future studies should do so.     

不同前路内固定方式治疗枢椎椎体横行骨折合并Hangman骨折稳定性的有限元分析

【摘要】 目的：应用有限元分析评价三种C2~C3前路内固定方式治疗枢椎椎体横行骨折合并Hangman骨折的生物力学稳定性,为临床手术方式选择提供理论参考。方法：选择1位35岁健康男性志愿者,采用16排螺旋CT对枕骨底（C0）~C3节段进行层厚0.5mm的薄层扫描,利用Mimics 10.01、Hypermesh V 10.0及ABAQUS 6.11软件,建立正常颈椎C0~C3节段三维六面体网格有限元模型（FE/Intact）并进行有效性验证。在已验证的C0~C3节段模型上通过弱化网格单元强度的方法模拟建立枢椎椎体横行骨折合并Hangman骨折模型（FE/Fracture）并进行验证;在FE/Fracture上分别建立三种C2~C3前路内固定模型：前路C2/3椎间盘切除、cage植骨融合+长钢板螺钉内固定模型（FE/cage+ACFLP）;前路齿状突螺钉固定+C2/3椎间盘切除、cage植骨融合+短钢板螺钉内固定模型（FE/AOSF+cage+ACFSP）;前路齿状突螺钉固定+C2/3椎间盘切除、cage植骨融合+长钢板螺钉内固定模型（FE/AOSF+cage+ACFLP）,对FE/Intact、FE/Fracture和三种内固定模型进行边界约束后分别施加前屈、后伸、侧屈、旋转四种生理载荷,比较各模型在不同工况下三维活动的角位移（ROM）及骨折端节点位移变化。结果：建立的FE/Intact外观逼真,几何相似性好,经验证有效。在相同条件下FE/Fracture模型三维活动度较FE/Intact模型明显增大,在前屈、后伸、侧屈及旋转方向上的ROM分别增加至FE/Fracture模型的244.7％、203.3％、188.9％、200％;FE/AOSF+cage+ACFLP在前屈、后伸、侧屈、旋转方向上的ROM分别为FE/Intact的60.5％、70％、66.7％、62.5％;FE/AOSF+cage+ACFSP在各方向的ROM分别为FE/Intact的118.4％、123.3％、148.1％、175％;FE/cage+ACFLP在各方向上的ROM分别为FE/Intact的123.7％、143.3％、122.2％、137.5％。FE/AOSF+cage+ACFLP稳定性最强,骨折端位移最小;FE/AOSF+cage+ACFSP稳定性较差,其在侧屈和旋转方向上ROM及骨折端位移最大;FE/cage+ACFLP在前屈及后伸方向上提供的稳定性最差,骨折端的位移最大。结论：FE/AOSF+cage+ACFLP固定可为枢椎椎体横行骨折合并Hangman骨折提供较强的生物力学稳定性,达到固定融合C2~C3节段和骨折断端以重建上颈椎稳定性的目的。     

An in vitro study into the accuracy of a novel method for recording the mandibular transverse horizontal axis

Objectives

To assess the accuracy of a novel, non-invasive method for determining the axis of rotation of articulated dental study casts.

Method

A 3D structured light scanner was constructed using a projector and two CMOS cameras. Dental stone casts were arbitrarily mounted on an average value articulator. With the teeth together, sets of 10 scans were taken from three different viewpoints. Each scan captured approximately six upper teeth and six lower teeth. The teeth were then propped open, creating 10 mm of incisal separation, and the three sets of 10 scans were repeated. From each pair of scans an axis of rotation was calculated using custom software. A total of 900 axes were created this way. The locations of these axes were plotted in sagittal planes located 57.5 mm left and right of the midline to represent the position of the temporo-mandibular joints (TMJs). The accuracy of axis location was then assessed.

Results

The average radius of error of the individual axes, compared to the real axis, was 2.65 ± 1.01 mm. 61.3% of the axes lay within 3 mm of the true axis, and 99.2% of the axes lay within 5 mm of the true axis.

Conclusions

The accuracy of this method is clinically acceptable. Further studies are required to confirm the accuracy of the virtual inter-occlusal records at the level of the dentition. Clinical studies are then indicated to determine whether the transverse horizontal axis on a patient can similarly be determined.     

组织多普勒成像技术评价正常胎儿心脏纵轴功能

目的利用组织多普勒成像技术（TDI）测量正常胎儿心肌运动速度,观察其心脏纵轴功能及临床应用价值。方法应用组织多普勒技术测量152例孕龄21—39周的正常胎儿心脏进行测量,在心尖四腔切面将取样容积分别放置于右室游离壁、室间隔、左室侧壁与房室环交界处,测量收缩期Sm波、舒张早期Em波和舒张晚期Am波,计算Em／Am比值,进行统计分析和处理。结果右心室收缩期Sm及舒张早期Em测值明显大于左心室及室间隔处,左、右心室Sm、Em、Am、Era／Am均随孕周的增加而增加,呈正相关关系。左、右心室的Sm与左、右心室的心输出量有相关性,左：右心室Em／Am与E／A有相关性。结论利用TDI评价胎儿心脏纵轴运动是安全、准确、可行的。     

肠道菌群与脑-肠轴功能相互影响的研究进展

人体肠道内的菌群参与了许多生理功能的维持和疾病的发生。作为大脑和胃肠道功能相互调节的重要桥梁,脑-肠轴功能的正常发挥是肠道菌群维持稳定的条件。脑-肠轴紊乱可激活肠黏膜免疫,对肠道菌群产生影响,使菌群结构发生改变。反之,肠道菌群结构改变亦会影响神经系统发育,导致脑-肠轴功能紊乱,其中迷走神经和血清代谢物质在脑-肠轴功能的调节中发挥重要作用。本文就肠道菌群与脑-肠轴功能相互影响的研究进展作一综述。