Crossed Intralaminar Screws for Fusion of the Cervicothoracic Junction and the Thoracic Spine: The Experience in an Iberic Service with Case Series and Review of the Current Literature with Technique Description

The treatment of pathologies in the thoracic spine is a challenge. The periodic failure of pedicle screw insertion and anatomical variations make the search for an alternative to pedicle screws in thoracic spine surgery necessary. The interlaminar crossed screws is a well-known and secure method for fusion in cervical spine, and in thoracic spine there used to be insufficient clinical data to support this technique, until now. We demonstrate in an initial series of 10 cases treated with interlaminar fusion in association of other fusion techniques in the thoracic spine with good results. Objective: Intralaminar screws have been shown to be a biomechanical salvage technique in the thoracic spine, especially in long cervicothoracic, thoracic and thoracolumbar fixation. The goals of this article are to demonstrate our initial experience and the range of indications for thoracic crossed intralaminar screws. Methods: In this article we describe our initial series performed at S&#227o Teot&#243nio Hospital in Viseu, Portugal, and our results, and also provide a comprehensive review of the recent literature in the use of intralaminar crossed fixation.

A finite element modeling of posterior atlantoaxial fixation and biomechanical analysis of C2 intralaminar screw fixation

Background The objective of this study was to use three-dimensional finite element （FE） models to analyze the stability and the biomechanics of two upper cervical fixation methods：the C2 intralaminar screw method and the C2 pedicle screw method.Methods From computed tomography images,a nonlinear three-dimensional FE model from C0 （occiput） to C3 was developed with anatomic detail.The C2 intralaminar screw and the C2 pedicle screw systems were added to the model,in parallel to establish the interlaminar model and the pedicle model.The two models were operated with all possible states of motion and physiological loads to simulate normal movement.Results Both the C2 intralaminar screw method and the C2 pedicle screw method significantly reduced motion compared with the intact model.There were no statistically significant differences between the two methods.The Von Mises stresses of the internal and external laminar walls were similar between the two methods.Stability was also similar.Conclusions The C2 intralaminar screw method can complement but cannot completely replace the C2 pedicle screw method.Clinicians would need to assess and decide which approach to adopt for the best therapeutic effect.

国人腰椎峡部裂直接修补螺钉的解剖学参数测量

目的:测量国人下腰段腰椎峡部裂直接修补螺钉的手术相关解剖学参数,探讨国人应用该方法的可行性及适当的螺钉规格.方法:随机选取18至40岁成年人腰椎三维CT影像资料男女各40名作为研究对象,在其第3、4、5腰椎3个节段确定以椎板下缘中点为理想进钉点,与峡部上下表面最凹陷两点连线中点所在线段止于同侧椎弓根上切迹骨皮质最凹陷处为理想钉道,测量所在矢状面进钉长度、峡部上径、下径、外径、进钉角度及水平面正中距离、冠状面外偏角度等手术相关参数,统计性别与节段间各参数的差异.结果:各节段间左右双侧各参数无差异,平均进钉长度第3腰椎35.79 mm大于第4腰椎34.74 mm、大于第5腰椎31.52mm,平均外径第3腰椎6.98 mm小于第4腰椎7.52mm、小于第5腰椎7.91mm,平均正中距离第3腰椎9.26 mm小于第4腰椎10.64mm、小于第5腰椎12.99mm,平均外偏角第3腰椎7.23°大于第4腰椎6.41°、大于第5腰椎4.06°,差异均具有统计学意义;各节段头偏角度无差异.男性各节段进钉长度及头偏、外偏角度均大于女性.结论:峡部裂直接修补螺钉既定的理想进钉点与钉道适用于国人第3～5腰椎各节段的峡部裂解剖学特征,大部分研究对象适用4.5mm直径的螺钉.

枢椎椎板螺钉用于颅颈交界区后路固定的疗效评价

目的 评价枢椎（C2）椎板螺钉固定的安全性及有效性。方法2004年5月至2010年8月，回顾性总结分析14例c2椎板螺钉固定患者的临床资料。手术前后分别行MRI及CT薄层扫描及重建，评价脊髓受压程度，螺钉位置及脱位复位程度，3—6个月后复查CT观察骨融合情况。结果14例患者的28枚螺钉中，27枚位置良好，仅1枚突破c2椎板外层皮质，但没有影响到固定的稳定性；11例脱位患者均获得满意的复位及脊髓减压。随访中13例6个月时骨融合，1例3个月时出现复位丢失。结论c2椎板螺钉植入简单、安全，但其长期有效性及能否替代C2椎弓根螺钉仍有待进一步观察研究。