计算机导航在脊柱外科手术应用实验和临床研究

目的探讨计算机导航技术在脊柱外科中的应用价值。方法自2002年12月将红外线主动诱导计算机导航系统应用于脊柱外科，进行了相关的实验和临床研究。实验研究采用40具成人颈椎标本，分别采用盲法、透视法、透视导航法、CT三维导航法和Iso—C术中三维导航法进行下颈椎椎弓根螺钉植入。术后通过大体解剖观察评价植钉的准确性。同时对163例采用不同导航方式（包括透视导航、CT三维导航和Iso—C术中三维导航）辅助下脊柱外科手术进行回顾性分析，通过术后影像学检查判断内固定术的植钉准确性。结果实验研究共植入螺钉398枚。盲法组平均手术时间27min；优29枚（36.3％），良21枚（26.3％），差30枚（37．5％）。透视法组平均手术时间112min；优35枚（44．9％），良29枚（37.2％），差14枚（17．9％）。透视导航法组平均手术时间69min；优34枚（42．5％），良36枚（45．0％），差10枚（12．5％）。CT三维导航法组平均手术时间98min；优70枚（87．5％），良10枚（12．5％），无差的螺钉。Iso—C术中三维导航法组平均手术时间91min；优72枚（90％），良8枚（10％），无差的螺钉。临床病例中，透视导航组共272枚螺钉，优243枚（89．3％），良29枚（10．7％）。CT导航组共571枚螺钉，优485枚（84．9％），良82枚（14．4％），差4枚（0．7％，均发生于早期颈椎手术病例）。Iso—C术中三维导航组共142枚螺钉，优136枚（95．8％），良6枚（4．2％，5枚为颈椎，1枚为腰椎）。结论正确应用计算机导航系统能显著提高脊柱外科手术的安全性。三种导航方法各有优缺点，Iso—C术中三维导航技术具有良好的应用前景并有可能逐渐替代其他两种导航技术。     

3D打印导航模板引导双侧下颈椎前路椎弓根螺钉置钉的可行性

目的 :通过3D打印技术及骨科数字化技术制作下颈椎前路椎弓根螺钉置钉导航模板,观察模板辅助下置钉的准确性。方法:选取正常成人颈椎湿性标本10具(男、女各5具),将椎前软组织剔除,采用64排薄层CT扫描后获取其DICOM格式数据,导入Mimics软件后三维建模并为颈前路椎弓根螺钉选取理想钉道,设计建立螺钉导航模板后导出其STL数据,通过3D打印机快速打印成型。在导航导板引导下进行下颈椎前路椎弓根螺钉置钉,通过X线及CT评价螺钉的准确性。结果:10具尸体分别于C3~T1每节段置入2枚螺钉,共计120枚,根据螺钉的位置将其分为4级:0级,螺钉完全在椎弓根内,共115枚;1级,螺钉穿破椎弓根皮质,穿出部分小于螺钉直径的25%,1枚;2级,螺钉穿破椎弓根皮质,穿出部分为螺钉直径的25%~50%,3枚;3级,螺钉穿出椎弓根部分大于螺钉直径的50%,1枚。5枚穿破椎弓根皮质者2枚穿破椎弓根内侧皮质,3枚穿破外侧皮质,总体准确性为95.8%。结论:在湿性尸体颈椎标本上应用3D打印及骨科数字化技术制作的导航模板辅助行下颈椎前路椎弓根螺钉置钉的准确性高,为临床应用提供了依据。     

颈椎椎弓根螺钉定位系统的实验研究

目的 寻找～种新的颈椎椎弓根螺钉植入方法 ,提高手术安全性并减少手术费用. 方法 以不锈钢材料制造颈椎椎弓根螺钉定位系统.取自愿捐赠的尸体颈椎标本10个,按照配伍组设计,左、右侧分别为对照组和实验组.对照组采用Abumi徒手植钉法,实验组采用定位系统引导植钉法,于C2～7,各植入螺钉60枚.观察螺钉植入情况,以螺钉是否穿出椎弓根壁为标准衡量植钉准确性. 结果 对照组行椎弓根内植钉32枚(53.33%),椎弓根外植钉28枚(46.67%);造成神经根损伤9枚(15.00%),椎动脉损伤5枚(8.33%),无脊髓损伤;植钉准确率:优32枚,可14枚,差14枚,合格率76.67%.实验组行椎弓根内植钉54枚(90.00%),椎弓根外植钉6枚(10.00%);造成椎动脉损伤1枚(1.67%),无神经根和脊髓损伤;植钉准确率:优54枚,可5枚,差1枚,合格率98.33%,与对照组比较差异有统计学意义(P<0.05). 结论 颈椎椎弓根螺钉定位系统引导下植钉准确、操作简便、费用较低,通过进一步研究可应用于临床.     

CT三维导航系统辅助颈椎椎弓根螺钉内固定技术的临床应用

目的探讨计算机CT三维导航系统辅助下进行颈椎椎弓根螺钉内固定的可行性和置钉精确性。方法总结CT三维导航系统辅助下置入的159枚颈椎(C2-7)椎弓根螺钉,术后进行经椎弓根螺钉水平的CT平扫,观察椎弓根螺钉置入的精确性。同时总结X线透视引导下145枚颈椎椎弓根螺钉的置钉准确性,并与CT三维导航引导组进行对比分析。并对其中20例患者进行术中导航操作时间和精确性的监测。结果CT三维导航系统引导组螺钉置入满意率为97.5%,X线透视引导组螺钉置入满意率为91.7%,两组满意率差异有显著性意义(P<0.05)。导航组位置不满意的4枚螺钉均发生于早期病例,导航系统使用熟练后未再出现置钉不满意病例。两组病例均未出现明显的神经、血管损伤并发症。术中工具注册和参考点照合时间平均3.5min(2～8min),位置误差率平均0.31mm(0.12～0.56mm,导航仪自动计算)。每枚椎弓根螺钉定位针置入所需时间平均2min(1～3.5min)。术中只需进行2次C型臂X线机透视印证螺钉定位针和螺钉置入的准确性。结论采用CT三维导航系统辅助进行颈椎椎弓根螺钉内固定是可行的,与X线透视引导相比,能显著提高椎弓根螺钉置入的精确性、安全性。     

3D打印个体化导航模板在胸椎和颈椎椎弓根螺钉植入的临床应用

目的 研究数字化(3D)打印技术的个性化导航模板设计在胸椎和颈椎手术个性化置钉应用的准确性和安全性。方法 2014年7月至2014年11月,对7例需要行胸椎、颈椎椎弓根螺钉植入手术的患者术前通过CT扫描、Mimics软件三维重建建立三维仿真模型。并使用Geomagic软件设计最佳的内固定钉道,然后根据钉道设计导航模板,用3D打印机打印导航模板,用于手术时辅助置钉;术中辅助植入胸椎、颈椎椎弓根螺钉共24枚,术后CT扫描评价螺钉位置,记录有无与螺钉植入的相关并发症。结果 通过导航模板辅助植入的24枚椎弓根螺钉,23枚完全在椎弓根内,1枚穿破椎弓根外壁,穿出距离均小于1.2 mm,椎弓根穿破率为4%,植钉准确率为96%,螺钉位置可接受率为100%。无一例出现螺钉植入有关的神经、血管损伤等并发症。结论 3D打印个体化导航模板辅助胸椎、颈椎椎弓根螺钉植入的植钉准确性高、安全。     

改良3D打印导板辅助颈椎椎弓根螺钉置钉的准确性研究

【摘要】 目的：探讨改良3D打印导板辅助颈椎椎弓根螺钉置钉的准确性。方法：回顾性分析2016年1月~2023年1月在我院行颈椎后路椎弓根螺钉内固定手术的60例患者的临床资料,其中男30例,女30例,年龄58.7±13.8岁（17~84岁）;根据颈椎后路手术是否使用导板辅助置钉分为导板组及徒手置钉组。导板组（30例）采用改良3D打印导板辅助颈椎椎弓根置钉,徒手置钉组（30例）采用角度尺辅助颈椎弓根置钉,两组患者年龄、性别、术前诊断无统计学差异（P＞0.05）。所有患者术后1周行颈椎CT扫描,按照Kaneyama标准判断椎弓根置钉准确性：0级,螺钉完全处于椎弓根中,没有穿破骨皮质;1级,螺钉穿破皮质<螺钉直径的50％;2级,螺钉穿破皮质≥螺钉直径的50％但没完全穿出;3级,完全穿出骨皮质。记录椎弓根置钉准确率（0级+1级螺钉占比）及因螺钉误置导致的血管神经损伤、切口感染、脑脊液漏、螺钉松动断裂等并发症。结果：导板组共置入椎弓根螺钉152枚,其中0级74枚,1级68枚,2级10枚,3级0枚,置钉准确率93.4%;徒手置钉组共置入椎弓根螺钉136枚,其中0级53枚,1级61枚,2级18枚,3级4枚,置钉准确率83.8%,导板组置钉准确率高于徒手置钉组（P＜0.05）。所有患者均未出现因椎弓根螺钉误置导致的血管神经损伤、切口感染及脑脊液漏等相关并发症。所有患者随访5～29个月（14.2±7.7个月）,无内固定松动、断裂等并发症。结论：改良3D打印导板辅助颈椎椎弓根置钉可提高置钉精准度。     

导航辅助置入下颈椎椎弓根螺钉的误差分析

[目的]探讨导航辅助置入下颈椎椎弓根螺钉的准确性和产生误差的原因.[方法]25例下颈椎疾患手术病人,导航辅助下置入144枚颈椎(C3-7,)椎弓根螺钉,术后行X线、CT检查,横断位测量螺钉中线与椎弓根内壁的相对位置、与椎体中线的角度;矢状位测量螺钉中线与椎弓根上壁的相对位置、与椎体上缘的角度;并与导航图像的对应数据进行统计学分析.[结果]2枚螺钉穿出椎弓根上壁,3枚螺钉穿出椎弓根外壁入椎动脉孔,其它螺钉术后CT和术中导航图像所显示的位置角度无显著性差异,导航图像的显示是基于坚硬物体原则,颈椎手术本身特点不可能完全满足如此要求,两者偏差表现为"漂移"现象.[结论]导航辅助置入下颈椎椎弓根螺钉准确性显著提高,术中漂移是置钉偏差的原因.     

电磁导航系统结合Stagnara投照法在特发性脊柱侧凸手术中的应用

目的:探讨在特发性脊柱侧凸三维矫形术中应用电磁导航系统结合Stagnara投照法采集C型臂X线透视图像对椎弓根螺钉置入准确性与安全性的影响.方法:2006年4月～2008年12月在电磁导航辅助下行特发性脊柱侧凸三维矫形术47例(导航组),共置入椎弓根螺钉492枚:2004年6月～2006年4月在C型臂X线机透视下行特发性脊柱侧凸三维矫形术39例(透视组),共置入椎弓根螺钉454枚,两组均采用Stagnara投照法采集C型臂X线透视图像.术后行CT薄层平扫加椎弓根矢状面二维重建,通过测量椎弓根皮质外缘与穿出的螺钉边缘的垂直距离对椎弓根螺钉位置进行评价,并分为A、B、C、D级,以A级和B级合并计算优良率.结果:导航组的手术时间为165～420min,平均233.7min,透视组为175～365min.平均236.1min,两组比较无显著性差异(P>0.05);导航组术中出血量为450～1650ml,平均712.2ml.透视组为550～1900ml,平均794.9ml,两组比较有显著性差异(P<0.05).导航组术后椎弓根螺钉位置A级476枚,B级9枚,C级5枚,D级2枚,优良率为98.5%;透视组A级411枚,B级14枚,C级17枚,D级12枚,优良率为93.6%,两组置钉优良率比较有显著性差异(P<0.05).导航组无神经、血管并发症发生.透视组2例在术中发生螺钉损伤硬膜囊,1例术后发现螺钉刺激神经根.结论:在特发性脊柱侧凸三维矫形术中应用电磁导航系统结合Stagnara投照法采集C型臂X线透视图像可降低椎弓根螺钉的误置率,减少术中出血量,提高手术安全性.     

计算机导航系统和C臂机透视引导颈椎椎弓根螺钉内固定技术的临床对比研究

目的探讨颈椎（C1-C7）椎弓根螺钉内固定的可行性和两种不同置钉方法的精确性。方法通过术后进行X线摄片、CT或术后Iso-C断层扫描等方法,判断C臂机透视引导下置入的145枚和三维导航系统（CT三维导航或Iso—C术中三维导航）辅助下187枚颈椎椎弓根螺钉病例的置钉准确性。结果三维导航系统引导组螺钉置入满意率（97．9％,183／187）明显高于C臂机透视引导组（91．7％,133／145）（χ2=6．705,P=0．010）。且三维导航系统引导组位置不满意的4枚螺钉均发生于早期病例,导航系统使用熟练后未再出现置钉不满意的病例。两组病例均未出现明显的神经血管损伤并发症（C臂机透视引导组2例术后一过性上肢疼痛）。对三维导航系统引导组中25例进行术中导航操作时间和导航精确性的监测。CT三维导航术中工具注册和参考点照合时间平均3．5min（2—8rain）,位置误差率平均0．31mm（0．12—0．56mm,导航仪自动计算）;Iso—C术中三维导航图像采集和传输时间平均6．2min（5—7min）,每颗椎弓根螺钉定位针置入所需时间平均2min（1—3．5min）;术中只需进行2次C臂机透视印证螺钉定位针和螺钉置入的准确性。结论采用三维导航系统辅助,能显著提高椎弓根螺钉置入的精确性,其操作技术有待完善。     

3D打印椎弓根导航模板在下颈椎椎弓根置钉中的临床应用

【摘要】 目的：探讨采用优化设计的3D打印椎弓根导航模板辅助下颈椎椎弓根螺钉置入的安全性和准确性。方法：回顾性分析2016年8月~2022年10月在我科行颈椎后路椎弓根螺钉内固定手术的患者42例,年龄32~74岁（50.1±9.8岁）,随访13~25个月（19.6±3.2个月）。根据置钉方式分为导板组（n=22）和徒手组（n=20）：导板组采用优化的椎弓根钻孔导航模板设计方案,3D打印制作下颈椎椎弓根导航模板辅助椎弓根置钉,其中男性12例,女性10例,颈椎损伤或颈脊髓损伤6例,后纵韧带骨化症（OPLL）9例,颈椎管肿瘤5例,脊髓型颈椎病2例;徒手组根据术前颈椎CT测量椎弓根角度、直径等参数,采用徒手置钉,其中男、女各10例,颈椎损伤或颈脊髓损伤4例,OPLL 10例,颈椎管肿瘤5例,脊髓型颈椎病1例。两组患者性别构成、年龄、诊断、术前VAS评分、JOA评分比较无统计学差异（P>0.05）。记录两组患者手术时间、术中出血量;术后1周颈椎CT扫描,按照Kaneyama方法评估椎弓根置钉的准确性：0级,螺钉完全位于椎弓根内;1级,穿破椎弓根的部分<螺钉直径的50%;2级,穿破椎弓根的部分>螺钉直径的50%;3级,椎弓根螺钉完全位于椎弓根外。0级或1级定义为椎弓根置钉准确,2级或3级为螺钉误置。记录患者的围手术期并发症,统计并比较两组术后12个月疼痛视觉模拟评分（VAS）、日本骨科学会（JOA）评分。结果：42例患者手术顺利,导板组手术时间102.2±16.1min,术中出血量89.3±17.7mL;均少于徒手组142.8±20.9min,133.3±34.0mL（P<0.01）。42例患者共置入下颈椎椎弓根螺钉216枚：导板组118枚,其中0级90枚,1级22枚,2级5枚,3级1枚,置钉准确率94.9%（112/118）;徒手组98枚,其中0级48枚,1级36枚,2级10枚,3级4枚,置钉准确率85.7%（84/98）。导板组置钉准确率显著性高于徒手组（P<0.05）。两组患者均未出现螺钉相关神经血管损伤,无内固定松动断裂并发症,术后12个月VAS评分较术前显著性降低（P<0.01）,JOA评分较术前显著性提高（P<0.01）,两组间比较无显著性差异（P>0.05）。结论：3D打印椎弓根导航模板的优化设计方案有助于提高下颈椎椎弓根置钉的准确性。     

X线透视与计算机导航系统引导颈椎椎弓根螺钉内固定技术的对比研究

目的对X线透视下和计算机导航系统引导下颈椎椎弓根螺钉内固定的精确性进行对比研究。方法X线透视引导下145枚和CT三维导航系统辅助下置入的159枚颈椎椎弓根螺钉,术后进行经椎弓根螺钉水平的CT平扫或术后c型臂透视3D重建,观察椎弓根螺钉置入的精确性。结果X线透视引导组螺钉置入满意率为91．7％,CT三维导航系统引导组螺钉置入满意率为97．5％,两组满意率有显著性差异（P〈0．05）。两组病例均未出现明显的神经血管损伤并发症。对其中20例病例进行了术中导航操作时间和导航精确性的监测,术中工具注册和参考点照合时间平均3．5min（2～8min）,位置误差率平均0．31mm（0．12～0．56mm）。每颗椎弓根螺钉定位针置入所需时间平均2min（1-3．5min）。术中只需进行两次C型臂透视印证螺钉定位针和螺钉置入的准确性。结论采用CT三维导航系统辅助,能显著提高椎弓根螺钉置入的精确性。     

Accuracy of lower cervical pedicle screw placement with assistance of distinct navigation systems: a human cadaveric study

Purpose

Evaluate the accuracy of five different techniques for lower cervical pedicle screw placement.

Methods

Forty human cadaveric cervical spines were equally divided into five groups, and each group had eight specimens. Pedicle screws with dia. 3.5 mm were used. Group 1 was blind screw placement without any assistance; Group 2–5 was assisted by the X-ray fluoroscopy, virtual fluoroscopy navigation system, CT-based navigation system, and Iso-C 3D navigation system, respectively. Thereafter, cortical integrity of each pedicle was evaluated by anatomic dissection of the specimens.

Results

A total of 398 pedicle screws were inserted. In the Group 1–5, the average operation time per sample was 27 ± 3.0, 112 ± 10.3, 69 ± 6.4, 98 ± 11.0, and 91 ± 6.0 min, respectively. The outcome for excellent, fair and poor were 29 (36.3 %), 21 (26.2 %) and 30 (37.5 %) in Group 1; 35 (44.9 %), 29 (37.2 %) and 14 (17.9 %) in Group 2; 34 (42.5 %), 36 (45.0 %) and 10 (12.5 %) in Group 3; 70 (87.5 %), 10 (12.5 %) and 0 (0.0 %) in Group 4; 72 (90.0 %), 8 (10.0 %) and 0 (0.0 %) in Group 5.

Conclusions

Blind screw placement was surely unsafe. Lower cervical pedicle screw placement assisted by the CT-based navigation system or the Iso-C 3D navigation system significantly improved the accuracy compared to the fluoroscopy assistance and the virtual fluoroscopy navigation assistance.     

Accuracy of fluoroscopic navigation of pedicle screws. CT-based evaluation of bone screw placement

While the advantages of C-arm navigation in computer-assisted spine surgery are obvious, the accuracy of pedicle screw placement with virtual fluoroscopy still needs to be verified. The C-arm-based ION system (Medtronic Sofamor Danek) was used to navigate pedicle screw insertion in patients undergoing spinal surgery for various conditions. In a prospective study, a total of 160 screws were inserted in the first 30 consecutive patients since introduction of the system at our institution: 54 at the thoracic spine (highest level: TH4) and 106 at the lumbar spine. Computed tomography (CT) scans were performed postoperatively by two independent radiologists to control the accuracy of screw placement at the level of the pedicles after reconstruction of axial images according to Laine et al. The comparison of the calculated accuracy rate of pedicle screw placement using virtual fluoroscopy with reported results achieved with CT-based navigation shows similar results for virtual fluoroscopy and a remarkable increase of accuracy in comparison to reports on conventional pedicle screw placement.     

快速成型个体化导航模板辅助胸椎椎弓根螺钉置入可行性研究

[目的]通过尸体标本实验的方法探讨个体化导航模板辅助胸椎椎弓根螺钉置入的准确性及可行性.[方法]对6具胸椎尸体标本进行CT扫描,根据CT扫描资料,利用逆向工程原理及快速成型技术设计制造出个体化导航模板,利用个体化导航模板在尸体标本上辅助置入胸椎椎弓根螺钉,所有螺钉的置入由同一位具有腰椎椎弓根螺钉置钉经验但无胸椎椎弓根螺钉置钉经验的骨科医师进行操作,随后采用大体解剖的方法肉眼观察置钉的准确性;并根据螺钉是否穿破椎弓根、穿出距离及穿破方向进行分级.[结果]共设计制作了72个个体化导航模板辅助置入胸椎椎弓根螺钉144枚,132枚(91.7%)螺钉完全在椎弓根内;12(8.3%)枚螺钉穿破椎弓根,其中2枚螺钉穿破椎弓根内侧壁(穿破距离分别为0.6、0.8 mm),10枚螺钉穿破椎弓根外侧壁(9枚螺钉穿出距离<2 mm,1枚螺钉穿出距离为2.5 mm);没有椎弓根上方、下方及椎体前方穿破的螺钉.所有穿破椎弓根壁的螺钉均在安全可接受的范围内.[结论]快速成型个体化导航模板辅助胸椎椎弓根螺钉置入准确率高,对术者无特别的经验要求,手术操作简单、安全,可避免术中放射性损伤,为胸椎椎弓根螺钉的置入提供了一种新的可行方法,尤其适用于初学者.     

Transpedicular screw placement: image-guided versus lateral-view fluoroscopy: in vitro simulation.

STUDY DESIGN: In vitro evaluation of monitoring screw placement using an image-guided system compared with the routine use of an image intensifier. OBJECTIVES: To compare a new computer-guided method of monitoring pedicle screw placement with a well-known method of monitoring using an image intensifier, using measurements of screw placement time and accuracy. SUMMARY OF BACKGROUND DATA: Pedicle screw placement relies on the identification of anatomic landmarks for the point of entry of the pedicle. The direction and depth of screw penetration are guided by an intraoperative lateral-view image intensifier. The use of frameless stereotaxy for computer-aided pedicle screw placement may increase the accuracy and safety of the screw insertion. To the authors' knowledge, there are no published data comparing these systems on the basis of operative time and screw placement accuracy. METHOD: Eight human cadaveric sections of five vertebrae each were used for an in vitro simulation of pedicle screw placement. Four spine surgeons were chosen to simulate the transpedicular screw placement. Each surgeon placed one screw into each pedicle of two spine sections (10 vertebrae, 20 screws). The surgeon was assisted by the lateral-view image intensifier on one spine section and by the navigational system on the second one. The four surgeons placed 80 pedicle screws. Forty screw placements were monitored by fluoroscopy and 40 by the image-guided navigational system. The time spent to place one screw was recorded, as well as the remarks by each surgeons on each method. Spines were rescanned, and the positions of the screws were compared between the group on which the image intensifier has been used and the group on which the navigational system had been used. RESULTS: In the image-guided technique group, one thoracic screw disrupted the lateral cortex of the pedicle, the average distance to the anterior wall of the body was 5 mm, and the average time for the insertion of one screw was 13.5 minutes. In the other group, two screws disrupted the inner cortex of a thoracic pedicle, the average distance to the anterior wall was 10.7 mm, and the average time for the insertion of one screw was 4 minutes. CONCLUSIONS: In vitro computer-aided pedicle screw insertion is more accurate than lateral-view fluoroscopy in the thoracic spine. The main disadvantage is the time consumption compared with that required by lateral-view fluoroscopy. The total time of the surgical operation should be decreased with the future development of these techniques.     

Pedicle screw placement with O-arm and stealth navigation

Various navigation systems are available to aid pedicle screw placement. The O-arm replaces the need for fluoroscopy and generates a 3-dimensional volumetric dataset that can be viewed as transverse, coronal, and sagittal images of the spine, similar to computed tomography (CT) scanning. The dataset can be downloaded to the Stealth system (Medtronic Navigation, Louisville, Colorado) for real-time intraoperative navigation.The main objectives of the current study were to assess (1) accuracy of pedicle screw placement using the O-arm/Stealth system, and (2) time for draping, positioning of the O-arm, and screw placement. Of 188 screws (25 patients), 116 had adequate images for analysis. The average time for O-arm draping was 3.5 minutes. Initial O-arm positioning was 6.1 minutes, and final positioning was 4.9 minutes. Mean time for screw placement, including O-arm draping and positioning and array attachment, was 8.1 minutes per screw. Mean time for screw placement alone was 5.9 minutes per screw. Screw placements on final O-arm images were on average 3.14 mm deeper than on the snapshot navigation images. Three screws (2.6%) breached the medial cortex, and 3 screws (2.6%) were misaligned and did not follow the pilot hole trajectory.The use of the O-arm/Stealth system was associated with a low rate of pedicle screw misalignment. The time to place screws was less than previously reported with CT navigation, but longer than conventional techniques. It is important to be aware of the potential discrepancy between snapshot navigation images and actual screw placement on final O-arm images. Our findings suggest that final screw positions may be deeper than awl positions appear on navigation images.     

A cadaveric study comparing standard fluoroscopy with fluoroscopy-based computer navigation for screw fixation of the odontoid

Although direct osteosynthesis of certain types of odontoid fractures may increase union and decrease the need for prolonged immobilization, screw fixation remains a technically demanding procedure. This study compares radiation exposure, surgical time, and accuracy of hardware placement using standard fluoroscopy versus computer-assisted fluoroscopy-based navigation ("virtual fluoroscopy") to assist with the placement of odontoid screws. Twenty-two cadavers were divided into two groups and underwent placement of a single odontoid screw using either standard fluoroscopic or virtual fluoroscopic guidance. Following screw placement, dissection of the C1-C2 segments was performed to assess accuracy. A significant reduction in fluoroscopy time was noted with the computer-based fluoroscopy technique, whereas the surgical time was not found to differ significantly between the techniques. No critical breaches (those risking neurovascular injury) were noted in either group, and the rate of noncritical breaches did not differ. The authors conclude that fluoroscopy-based virtual navigation appears to have a safety profile similar to standard fluoroscopy while allowing a reduction in radiation exposure.