滑动杆推簧排齐前牙的运用2例

正畸排齐前牙时,使用0．5 mm 直径不锈钢丝弯制滑动杆,在拥挤前牙两侧放置镍钛推簧,在交互力系下推开间隙、维持间隙的同时排齐前牙,用于治疗2例前牙轻中度拥挤患者,成功矫正了前牙拥挤、中线不齐等畸形。     

Anterior thoracic posture increases thoracolumbar disc loading

In the absence of external forces, the largest contributor to intervertebral disc (IVD) loads and stresses is trunk muscular activity. The relationship between trunk posture, spine geometry, extensor muscle activity, and the loads and stresses acting on the IVD is not well understood. The objective of this study was to characterize changes in thoracolumbar disc loads and extensor muscle forces following anterior translation of the thoracic spine in the upright posture. Vertebral body geometries (C2 to S1) and the location of the femoral head and acetabulum centroids were obtained by digitizing lateral, full-spine radiographs of 13 men and five women volunteers without previous history of back pain. Two standing, lateral, full-spine radiographic views were obtained for each subject: a neutral-posture lateral radiograph and a radiograph during anterior translation of the thorax relative to the pelvis (while keeping T1 aligned over T12). Extensor muscle loads, and compression and shear stresses acting on the IVDs, were calculated for each posture using a previously validated biomechanical model. Comparing vertebral centroids for the neutral posture to the anterior posture, subjects were able to anterior translate +101.5 mm±33.0 mm (C7–hip axis), +81.5 mm±39.2 mm (C7–S1) (vertebral centroid of C7 compared with a vertical line through the vertebral centroid of S1), and +58.9 mm±19.1 mm (T12–S1). In the anterior translated posture, disc loads and stresses were significantly increased for all levels below T9. Increases in IVD compressive loads and shear loads, and the corresponding stresses, were most marked at the L5–S1 level and L3–L4 level, respectively. The extensor muscle loads required to maintain static equilibrium in the upright posture increased from 147.2 N (mean, neutral posture) to 667.1 N (mean, translated posture) at L5–S1. Compressive loads on the anterior and posterior L5–S1 disc nearly doubled in the anterior translated posture. Anterior translation of the thorax resulted in significantly increased loads and stresses acting on the thoracolumbar spine. This posture is common in lumbar spinal disorders and could contribute to lumbar disc pathologies, progression of L5–S1 spondylolisthesis deformities, and poor outcomes after lumbar spine surgery. In conclusion, anterior trunk translation in the standing subject increases extensor muscle activity and loads and stresses acting on the intervertebral disc in the lower thoracic and lumbar regions.This study was presented, in part, at the 29th annual meeting of the International Society for the Study of the Lumbar Spine, Cleveland, OH, USA, 2002 May 14–18     

Improved accuracy of navigated drilling using a drill alignment device.

Drilling procedures are common in orthopedic surgery and are one specific task that may be aided by computer-assisted navigation. However, the inherent flexibility of drill bit bending may make this the limiting factor in achieving acceptable accuracy when using these systems. We designed an alignment device that was fit to a standard orthopedic drill that allowed an extension of the stabilizing point of a drill bit. In foam blocks with a similar density as cancellous bone, 208 total navigated drilling trials were performed, using four different sized drill bits (2.5, 3.2, 3.5, and 4.5 mm) with and without the alignment device. Drilling tracts of 80 mm were made towards an intended target on the other side of the block. Reduction in deviation from the intended target was significantly improved with the use of the guide, ranging from 33% to 45% for the four drill sizes. For the trails using the alignment device, the 2.5-mm drill bit was significantly less accurate than the three larger drills. Our results demonstrate that the use of external devices to augment drill bit stabilization can improve drilling accuracy. This may have particular importance when using navigation systems to drill into small anatomic confines.     

Non-invasive phakometric measurement of corneal and crystalline lens alignment in human eyes

We describe a non-invasive phakometric method for determining corneal axis rotation relative to the visual axis (beta) together with crystalline lens axis tilt (alpha) and decentration (d) relative to the corneal axis. This does not require corneal contact A-scan ultrasonography for the measurement of intraocular surface separations. Theoretical inherent errors of the method, evaluated by ray tracing through schematic eyes incorporating the full range of human ocular component variations, were found to be larger than the measurement errors (beta < 0.67 degrees , alpha < 0.72 degrees and d < 0.08 mm) observed in nine human eyes with known ocular component dimensions. Intersubject variations (mean +/- S.D.: beta = 6.2 +/- 3.4 degrees temporal, alpha = 0.2 +/- 1.8 degrees temporal and d = 0.1 +/- 0.1 mm temporal) and repeatability (1.96 x S.D. of difference between repeat readings: beta +/- 2.0 degrees , alpha +/- 1.8 degrees and d +/- 0.2 mm) were studied by measuring the left eyes of 45 subjects (aged 18-42 years, 29 females and 16 males, 15 Caucasians, 29 Indian Asians, one African, refractive error range -7.25 to +1.25 D mean spherical equivalent) on two occasions.     

家兔上矢状窦中1/3及其回流静脉结扎动物模型的建立

目的 建立一种新的上矢状窦中1／3及其回流静脉结扎的家兔动物模型，为上矢状窦的外科研究提供实验基础。方法 显微镜下暴露兔脑上矢状窦中1/3，用9-0无损伤显微缝合线结扎。同时结扎矢状窦两侧直径〉0．8mm的所有回流静脉。术后观察动物行为及脑组织病理变化，测定脑组织含水量。结果 上矢状窦中1/3及其回流静脉结扎可引起家兔偏瘫、肌张力减低等神经功能障碍，但大多能长期存活。结扎后主要病理改变：神经元变性，神经细胞与胶质细胞水肿。线粒体结构模糊．内质网扩张及窦旁皮质组织水肿；均能逐渐恢复。结论 家兔上矢状窦中1／3及其回流静脉结扎模型操作简单，易控制，稳定，重复性较好，病死率低，是比较理想的研究上矢状窦结扎的实验模型．     

家兔上矢状窦中1/3及其回流静脉结扎后SOD、MDA与脑含水量的变化

目的探讨家兔上矢状窦中1／3及其回流静脉结扎后窦旁皮质组织超氧化物歧化酶（SOD）活力、丙二醛（MDA）含量及脑含水量的变化及其意义。方法建立家兔上矢状窦中1／3及其回流静脉结扎的动物模型，结扎后于不同时间点（4h、8h、12h、24h、72h、90d）测定窦旁皮质组织SOD活力与MDA的含量以及脑含水量。结果家兔上矢状窦中1／3及其回流静脉结扎后．窦旁脑皮质组织MDA含量4h开始明显上升，8h达到峰值，12h以后逐渐降低，但24h仍然高于假手术对照组（P〈0．05），90d组基本接近对照组（P〉0．05）。SOD的活力变化与MDA含量变化相反；4h窦旁皮质组织出现脑水肿．8h到达高峰。以后随时间延长而逐渐减轻，90d组脑水肿接近于假手术对照组。结论家兔上矢状窦中1／3及其回流静脉结扎后在24h内氧自由基反应增强，防御氧自由基功能受损，以后逐渐恢复正常；结扎后窦旁皮质组织早期存在脑水肿，可能与脂质过氧化有关。     

家兔上矢状窦中1/3及其回流静脉结扎后脑水肿变化和水通道蛋白-4表达的研究

目的探讨家兔上矢状窦中1/3及其回流静脉结扎后窦旁皮层组织水肿变化、水通道蛋白-4(AQP4) 的表达及其变化。方法建立家兔上矢状窦中1/3及其回流静脉结扎的动物模型,用干湿重法、免疫组化方法和半定量逆转录聚合酶链反应(RT-PCR)分别检测窦旁皮层组织脑水肿、AQP4蛋白和AQP4mRNA的表达及其变化。结果家兔上矢状窦中1/3及其回流静脉结扎后,家兔可长期存活而无死亡;窦旁皮层组织4 h出现脑水肿,8 h到达高峰,以后随时间延长而逐渐减轻,长期组脑水肿接近于假手术对照组。家兔上矢状窦中1/3及其回流静脉结扎后窦旁皮层组织存在AQP4蛋白的表达,结扎后4 h AQP4表达显著高于正常水平,8 h达到峰值,其表达水平以后随时间延长而逐渐回落。AQP4的表达与脑含水量呈显著正相关(r=0．778,P<0．01);而窦旁皮层组织也存在 AQP4mRNA的表达,其结果与AQP4蛋白的表达相似。AQP4mRNA的表达与脑含水量呈显著正相关(r=0．885,P <0．01)。AQP4mRNA与AQP4蛋白的表达呈显著正相关(r=0．753,P<0．01)。结论家兔上矢状窦中1/3及其回流静脉结扎后窦旁皮层组织存在脑水肿,AQP4蛋白与AQP4mRNA在兔脑中有表达。两者的表达增强可能与上矢状窦中1/3及其回流静脉结扎后脑水肿的形成和发展密切相关。AQP4可能参与结扎后脑水肿的形成。     

Influence of corneal asymmetry on the phakometric measurement of ocular surface alignment

Phakometric measurements of corneal and crystalline lens surface alignment are influenced by corneal asymmetry in which the corneal apex does not coincide with the limbal centre. The purpose of this study was to determine the horizontal separation (e) between these corneal landmarks. Measurements were made in 60 normal eyes (30 subjects) using the Orbscan IIz corneal analysis workstation. Our results show that both corneal landmarks typically coincide, so that e = 0, but that inter-subject variations of about +/-1 mm can be expected (so that the corneal apex may fall nasal or temporal to the visual axis). This suggests that no correction for corneal asymmetry is required when estimating average amounts of ocular alignment from samples of eyes but that the measurement of e is strongly recommended for measurements in individual eyes.     

Open wedge tibial osteotomies influence on axial rotation and tibial slope

Inaccurate coronal plane and inadvertent sagittal plane realignment is a common problem after high tibial osteotomies (HTO). While the effects of an HTO on the coronal have been studied extensively, the influence on axial rotation has not been described in detail. The current study examines the effect of HTO on tibial rotation in the axial plane as determined by computed tomography. We hypothesized that high tibial osteotomies have an effect on tibial rotation in the axial plane and that depending on the predefined osteosynthetic implant used, a corresponding change in the tibial slope would occur. HTOs with a tapered 12.5 mm Puddu plate were performed on 13 limbs under computer-navigated control. All limbs were CT scanned before and after the HTO. Using specific software, the CT data was converted into 3D computer models and the following parameters compared: (a) varus-valgus leg alignment; (b) tibial axial rotation; (c) tibial slope (including determination of lateral and medial tibial slope, (d) leg length including determination of the tibial length. Results revealed: (a) a varus-valgus alignment increase of 11 ± 4.7° (P < 0.005); (b) an axial tibial rotation of 2.7 ± 6.3° (P < 0.075) occurred with external rotation in 10 out of 13 limbs (12° max external; 9.5° max internal); (c) tibial slope revealed differences of 4.2 ± 5.9° (P < 0.025); (d) the tibial length increased after HTO by 7.1 ± 3.7 mm (P < 0.005), while there was no significant change in overall leg length. In summary, tibial rotation does occur in high tibial osteotomies with though the degree of external rotation in this study tended not to be statiscally significant. Tapered implants do not guarantee maintenance of a steady tibial slope, while tibial length changes significantly when HTOs are performed. The combined use of CT and 3D software measurement techniques is reproducible and can be used without any further invasive fixation devices.