Genauigkeit der CT-basierten Navigation von Pedikelschrauben an der Brustwirbelsäule im Vergleich zur konventionellen Technik

The goal of this study was to evaluate the accuracy of CT-based computer-assisted pedicle screw insertion in the thoracic spine in patients with fractures, metastases, and spondylodiscitis compared to a conventional technique. A total of 324 pedicle screws were inserted in the thoracic spines of 85 patients: 211 screws were placed using a CT-based optoelectronic navigation system assisted by an image intensifier and 113 screws were placed with a conventional technique. Screw positions were evaluated with postoperative CT scans by an independent radiologist. In the computer-assisted group, 174 (82.5%) screws were found completely within their pedicles compared with 77 (68.1%) correctly placed screws in the conventional group ( p<0.003). Despite use of the navigation system, 1.9% of the computer-assisted screws perforated the pedicle wall by more than 4 mm. The additional use of the image intensifier helped to identify the correct vertebral body and avoided cranial or caudal pedicle wall perforations.     

Stereotactic navigation for placement of pedicle screws in the thoracic spine

OBJECTIVE: Pedicle screw fixation in the lumbar spine has become the standard of care for various causes of spinal instability. However, because of the smaller size and more complex morphology of the thoracic pedicle, screw placement in the thoracic spine can be extremely challenging. In several published series, cortical violations have been reported in up to 50% of screws placed with standard fluoroscopic techniques. The goal of this study is to evaluate the accuracy of thoracic pedicle screw placement by use of image-guided techniques. METHODS: During the past 4 years, 266 image-guided thoracic pedicle screws were placed in 65 patients at the University of Michigan Medical Center. Postoperative thin-cut computed tomographic scans were obtained in 52 of these patients who were available to enroll in the study. An impartial neuroradiologist evaluated 224 screws by use of a standardized grading scheme. All levels of the thoracic spine were included in the study. RESULTS: Chart review revealed no incidence of neurological, cardiovascular, or pulmonary injury. Of the 224 screws reviewed, there were 19 cortical violations (8.5%). Eleven (4.9%) were Grade II (< or =2 mm), and eight (3.6%) were Grade III (>2 mm) violations. Only five screws (2.2%), however, were thought to exhibit unintentional, structurally significant violations. Statistical analysis revealed a significantly higher rate of cortical perforation in the midthoracic spine (T4-T8, 16.7%; T1-T4, 8.8%; and T9-T12, 5.6%). CONCLUSION: The low rate of cortical perforations (8.5%) and structurally significant violations (2.2%) in this retrospective series compares favorably with previously published results that used anatomic landmarks and intraoperative fluoroscopy. This study provides further evidence that stereotactic placement of pedicle screws can be performed safely and effectively at all levels of the thoracic spine.     

Accuracy of pedicle screw insertion with and without computer assistance: a randomised controlled clinical study in 100 consecutive patients

We performed a randomised controlled study to assess the accuracy of computer-assisted pedicle screw insertion versus conventional screw placement under clinical conditions. One hundred patients scheduled for posterior thoracolumbar or lumbosacral pedicle screw instrumentation were randomised into two groups, either for conventional pedicle screw placement or computer-assisted screw application using an optoelectronic navigation system. From the computer-assisted group, nine patients were excluded: one because of an inadequate preoperative computed tomography study, seven because of problems with the specific instruments or the computer system, and one because of an intraoperative anesthesiological complication. Thus, there were 50 patients in the conventional group and 41 in the computer-assisted group, and the number of screws inserted was 277 and 219, respectively. There was no statistical difference between the groups concerning age, gender, diagnosis, type of operation performed, mean operating time, blood loss, or number of screws inserted. The time taken for screw insertion was significantly longer in the computer-assisted group. Postoperatively, screw positions were assessed by an independent radiologist using a sophisticated CT imaging protocol. The pedicle perforation rate was 13.4% in the conventional group and 4.6% in the computer-assisted group (P = 0.006). Pedicle perforations of more than 4 mm were found in 1.4% (4/277) of the screw insertions in the conventional group, and none in the computer-assisted group. Complications not related to pedicle screws were two L5 nerve root lesions, one end plate fracture, one major intraoperative bleeding and one postoperative death in the conventional group, and one deep infection in the computer-assisted group. In conclusion, pedicular screws were inserted more accurately with image-guided computer navigation than with conventional methods. Received: 11 October 1999 Revised: 2 February 2000 Accepted: 15 February 2000     

Accuracy of upper thoracic pedicle screw placement using three-dimensional image guidance

Background contextPedicle screw malposition rates using conventional techniques have been reported to occur with a frequency of 6% to 41%. The upper thoracic spine (T1–T3) is a challenging area for pedicle screw placement secondary to the small size of the pedicles, the inability to visualize this area with lateral fluoroscopy, and significant consequences for malpositioned screws. We describe our experience placing 150 pedicle screws in the T1–T3 levels using three-dimensional (3D) image guidance.PurposeThe aim of this study was to assess the accuracy of 3D image guidance for placing pedicle screws in the first three thoracic vertebrae.Study designThe accuracy of pedicle screw placement in the first three thoracic vertebrae was evaluated using postoperative thin-section computed tomography (CT) scans of the cervicothoracic region.Patient sampleThirty-four patients who underwent cervicothoracic fusion were included.Outcome measuresRadiological investigation with CT scans was performed during the postoperative period.MethodsThirty-four consecutive patients underwent cervicothoracic instrumentation and fusion for a total of 150 pedicle screws placed in the first three thoracic vertebrae. All screws were placed using 3D image guidance. Medical records and postoperative imaging of the cervicothoracic junction for each patient were retrospectively reviewed. An independent radiologist reviewed the placement of the pedicle screws and assessed for pedicle breach. All cortical violations were reported as Grade 1, 0 to 2 mm; Grade 2, 2 to 4 mm; and Grade 3, greater than 4 mm.ResultsOverall, 140 (93.3%) out of 150 screws were contained solely in the desired pedicle. All 10 pedicle violations were Grade 1. The direction of pedicle violation included three medial, four inferior, two superior, and one minor anterolateral vertebral body. No complication occurred as a result of screw placement or the use of image guidance.ConclusionsUpper thoracic pedicle screw placement is technically demanding as a result of variable pedicle anatomy and difficulty with two-dimensional visualization. This study demonstrates the accuracy and reliability of 3D image guidance when placing pedicle screws in this region. Advantages of this technology in our practice include safe and accurate placement of spinal instrumentation with little to no radiation exposure to the surgeon and operating room staff.     

导航辅助脊柱胸腰段椎弓根钉植入的临床应用

目的探讨临床运用计算机影像导航技术引导脊柱胸腰段椎弓根钉植入的准确性。方法2003年5月-2007年5月，29例患者接受116枚计算机影像导航技术引导脊柱胸腰段椎弓根钉植入手术治疗，T10-T1250枚胸椎弓根钉，L1-L3 66枚腰椎弓根钉。术中记录椎弓根钉植入所需时间及C-臂透视工作次数，椎弓根钉植入完成后，即行C-臂正侧位摄片并与导航路径进行比较测量。术后CT进行椎弓根层面扫描，根据椎弓根钉与椎弓根皮质问关系分为四级：A=在椎弓根内；B=突破皮质，〈2mm；C=突破皮质，2-4mm；C=突破皮质，〉4mm。结果术后CT椎弓根位置扫描显示：A级101枚（87．07％）；B级10枚（8．62％）；C级2枚（1．72％）；D级3枚（2．59％）。1枚椎弓根钉植入平均所需时间：2．73±0．64min（1．15～4．02min）。下胸椎9枚（7．75％）胸椎弓根钉突破皮质，上腰椎6枚（5．17％）腰椎弓根钉突破皮质，且临床观察未发现与椎弓根钉突破皮质相关的神经血管等并发症。植入的椎弓根钉C-臂正侧位摄片与导航路径吻合比较，进钉点均差2．6mm（最大3．1mm），角度均差3．3°（最大5．4°）。结论计算机影像导航辅助脊柱胸腰段椎弓根钉植入，提供二维、多平面实时显示，保证了脊柱胸腰段椎弓根钉植入的准确性及安全性，明显减少放射线的暴露强度。     

O-arm计算机导航辅助脊柱椎弓根螺钉置入的准确性

[目的]分析O-arm计算机辅助导航技术在脊柱椎弓根螺钉置入的准确性。[方法]回顾性分析2017年1月~2018年9月本院椎弓根螺钉置入患者575例,根据椎弓根螺钉置入方式不同,分为两组。导航组采用O-arm计算机辅助导航技术系统置入椎弓根螺钉233例,传统组采用传统徒手法置入椎弓根螺钉342例。行CT检查,依据Neo分型评估置钉准确性。[结果]导航组共置入1459枚椎弓根螺钉,其中C1~7置入222枚,T1~12置入535枚,L1~5置入652枚,S1置入50枚。每名患者置钉数量1~24枚,平均(6.26±3.77)枚。传统组共置入1724枚椎弓根螺钉,其中C1~7置入269枚,T1~12置入601枚,L1~5置入785枚,S1置入87枚。每名患者置钉数量1~20枚,平均(5.67±4.11)枚。导航组全部病例顺利完成手术,术中无血管、神经损伤等并发症,置钉安全率为100%,传统组有4例发生血管、神经损伤等并发症。所有患者术后进行12~24个月随访,随访过程均未发生不良事件。依据CT影像Neo分级标准,导航0型及1型椎弓根螺钉的成功置入率达98.01%,而传统组0型及1型椎弓根螺钉的成功置入率91.85%;两组间置入螺钉准确性的差异具有统计学意义(P<0.05)。[结论]与传统C臂X线机等徒手置钉方式相比,O-arm计算机辅助导航技术可提高脊柱椎弓根螺钉置入准确性,同时降低神经、血管等并发症的发生。     

Comparative results between conventional and computer-assisted pedicle screw installation in the thoracic, lumbar, and sacral spine

STUDY DESIGN: A comparative study on the position of pedicle screws in patients treated surgically with and without computer assistance. OBJECTIVES: To evaluate the accuracy of computer-assisted pedicle screw installation, and to evaluate its clinical benefit as compared with conventional pedicle screw installation techniques. SUMMARY OF BACKGROUND DATA: In vitro and clinical studies have documented a significant rate of misplaced screws in the thoracolumbar area. Neurologic complications are recognized problems caused by screw misplacement. METHODS: Patients treated surgically with computer assistance were compared with a historical control group of patients treated surgically with conventional techniques in the same hospital and by the same surgical team. All screw positions were measured with a postoperative magnetic resonance tomography, and cortical effractions were categorized in 2-mm increments. Patients' charts also were reviewed to assess individual neurologic outcomes. RESULTS: The control cohort was composed of 100 patients, with 544 screws from T5 to S1. The computer-assisted cohort was composed of 50 patients, with 294 screws from T2 to S1. In the control cohort, 461 of 544 screws (85%) were found completely within their pedicles as compared with 278 of 294 screws (95%) correctly placed in the computer-assisted group (P < 0.0001). All 16 screws incorrectly placed with computer assistance were found 0.1 mm to 2 mm from the pedicle cortex. In the control cohort, 68 screws were found 0.1 mm to 2 mm, 10 screws 2.1 mm to 4 mm, and 5 screws more than 4 mm from the pedicle cortex. Seven patients in the control cohort were surgically retreated because of postoperative neurologic deficits, whereas no patients in the computer-assisted group were surgically retreated. CONCLUSIONS: Computer assistance can decrease the incidence of incorrectly positioned pedicle screws.     

Accuracy of powered surgical instruments compared with manual instruments for pedicle screw insertion: Evaluation using o-arm-based navigation in scoliosis surgery

Background

Though powered surgical instruments for pedicle screw insertion combined with navigation have been developed to reduce time taken for spine surgery, clinical evidence demonstrating the safety and effectiveness of powered surgical instruments is limited. The goals of the present study were to compare the accuracy of powered instruments and manual instruments using O-arm-based navigation in surgery for scoliosis.

快速成形3D导板辅助下置入下颈椎前路椎弓根螺钉与徒手置钉的对比研究

目的:比较快速成形3D导板辅助下和徒手置入下颈椎前路椎弓根螺钉的位置差异,评价两种置钉方法的安全性.方法:8具甲醛浸泡后的成人下颈椎尸体标本,男4具,女4具;年龄32～65(40.3±5.6)岁,行X线片检查排除骨质破坏和畸形后,随机选取其中4具(3D导板组)行CT扫描后获得DICOM格式数据,导入Mimics软件建模...     

胸椎椎弓根螺钉置入位置的CT评价

目的:探讨胸椎椎弓根螺钉置入的准确性和安全性。方法:对37例胸椎椎弓根螺钉内固定患者术后行CT断层扫描,观察螺钉在椎弓根内的位置,记录螺钉穿透骨壁的位置、数目和距离。结果:37例患者共置入405枚胸椎椎弓根螺钉,124枚螺钉(30.61%)穿透骨壁,其中76枚(18.77%)穿透椎弓根外侧壁,32枚(7.90%)穿透椎弓根内侧壁,16枚(3.95%)穿透椎体前壁。66枚(16.30%)穿透距离<2mm,37枚(9.14%)穿透距离在2mm~4mm之间,21枚(5.9%)穿透距离>4mm。结论:胸椎椎弓根螺钉骨壁穿透率较高,应严格按照胸椎椎弓根螺钉置入方法,仔细操作,避免出现因螺钉置入不当造成神经、血管或内脏损伤等并发症。     

Screw perforation features in 129 consecutive patients performed computer-guided cervical pedicle screw insertion

Study design

A cross-sectional study of the data retrospectively collected by chart review.

Objectives

This study aimed to clarify screw perforation features in 129 consecutive patients treated with computer-assisted cervical pedicle screw (CPS) insertion and to determine important considerations for computer-assisted CPS insertion.

Summary of background data

CPS fixation has been criticized for the potential risk of serious injury to neurovascular structures. To avoid such serious risks, computed tomography (CT)-based navigation has been used during CPS insertion, but screw perforation can occur even with the use of a navigation system.

Methods

The records of 129 consecutive patients who underwent cervical (C2–C7) pedicle screw insertion using a CT-based navigation system from September 1997 to August 2013 were reviewed. Postoperative CT images were used to evaluate the accuracy of screw placement. The screw insertion status was classified as grade 1 (no perforation), indicating that the screw was accurately inserted in pedicle; grade 2 (minor perforation), indicating perforation of less than 50 % of the screw diameter; and grade 3 (major perforation), indicating perforation of 50 % or more of the screw diameter. We analyzed the direction and rate of screw perforation according to the vertebral level.

Results

The rate of grade 3 pedicle screw perforations was 6.7 % (39/579), whereas the combined rate of grades 2 and 3 perforations was 20.0 % (116/579). No clinically significant complications, such as vertebral artery injury, spinal cord injury, or nerve root injury, were caused by the screw perforations. Of the screws showing grade 3 perforation, 30.8 % screws were medially perforated and 69.2 % screws were laterally perforated. Of the screws showing grades 2 and 3 perforation, 21.6 % screws were medially perforated and 78.4 % screws were laterally perforated. Furthermore, we evaluated screw perforation rates according to the vertebral level. Grade 3 pedicle screw perforation occurred in 6.1 % of C2 screws; 7.5 % of C3 screws; 13.0 % of C4 screws; 6.5 % of C5 screws; 3.2 % of C6 screws; and 4.0 % of C7 screws. Grades 2 and 3 pedicle screw perforations occurred in 12.1 % of C2 screws, 22.6 % of C3 screws, 31.5 % of C4 screws, 22.2 % of C5 screws, 14.4 % of C6 screws, and 12.1 % of C7 screws. C3–5 screw perforation rate was significantly higher than C6–7 (p = 0.0024).

Conclusions

Careful insertion of pedicle screws is necessary, especially at C3 to C5, even when using a CT-based navigation system. Pedicle screws tend to be laterally perforated.     

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.     

Präzisionsanalyse navigationsgestützt implantierter thorakaler und lumbaler Pedikelschrauben Eine prospektive klinische Studie

A prospective clinical trial was performed to study the accuracy of pedicle screw placement of consecutive computer-aided and conventional techniques. Concerning the clinical performance of the navigation system, the average time of matching has been 8,4 minutes per vertebrae. For evaluation of the results, only complete intraosseous placement of the pedicle screw has been defined as correct position. Any medial or lateral perforation of the cortical structure of the pedicle was recorded as malplacement. In the CT-controlled patients complete intrapedicular placement of the screw was obtained in 36 of 45 thoracic (80%) and in 22 of 27 navigated lumbar (81%) pedicles. In the conventional cohort group 27 of 34 (79%) thoracal and 43 of 52 (83%) lumbar screws were completely in. No radicular neurologic damage, caused by a malplaced transpedicular screw has been observed in both groups. In the presented study is shown, that the application of the computer-assisted freehand navigation can improve results concerning the precision of spinal screw placement. Although, the spinal navigator has to consider a learning curve for the clinical inauguration of the system and the qualification of the implant system for computer-assisted application.     

Evaluation of a transpedicular drill guide for pedicle screw placement in the thoracic spine

Insertion of pedicle screws in the thoracic spine is technically difficult and may lead to major complications. Although many computer-assisted systems have been developed to optimize pedicle screw insertion, these systems are expensive, not user-friendly and involve significant radiation from pre-operative computed tomographic (CT) scan imaging. This study describes and evaluates a transpedicular drill guide (TDG) designed to assist in the proper placement of pedicle screws in the thoracic spine. Pilot holes were made manually using the TDG in the thoracic spine (T1-T11) of three human cadavers before inserting 4.5-mm-diameter screws. CT scans followed by visual inspection of the spines were performed to evaluate the position of the screws. Five of 66 screws (7.6%) violated the pedicle wall: two (3.0%) medially and three (4.5%) laterally. The medial and lateral perforations were within 1 mm and 2 mm of the pedicle wall, respectively. The medial perforations were not at risk of causing neurological complications. No screw penetrated the superior or inferior pedicle wall. The TDG is easy to use and can decrease the incidence of misplaced thoracic pedicle screws. The TDG could be used as a complement to fluoroscopy in certain applications, especially for training surgeons.     

Safety of thoracic pedicle screw application using the funnel technique in Asians: a cadaveric evaluation

The objective of this cadaveric study is to determine the safety and outcome of thoracic pedicle screw placement in Asians using the funnel technique. Pedicle screws have superior biomechanical as well as clinical data when compared to other methods of instrumentation. However, misplacement in the thoracic spine can result in major neurological implications. There is great variability of the thoracic pedicle morphometry between the Western and the Asian population. The feasibility of thoracic pedicle screw insertion in Asians has not been fully elucidated yet. A pre-insertion radiograph was performed and surgeons were blinded to the morphometry of the thoracic pedicles. 240 pedicle screws were inserted in ten Asian cadavers from T1 to T12 using the funnel technique. 5.0 mm screws were used from T1 to T6 while 6.0 mm screws were used from T7 to T12. Perforations were detected by direct visualization via a wide laminectomy. The narrowest pedicles are found between T3 and T6. T5 pedicle width is smallest measuring 4.1 ± 1.3 mm. There were 24 (10.0%) Grade 1 perforations and only 1 (0.4%) Grade 2 perforation. Grade 2 or worse perforation is considered significant perforation which would threaten the neural structures. There were twice as many lateral and inferior perforations compared to medial perforations. 48.0% of the perforations occurred at T1, T2 and T3 pedicles. Pedicle fracture occurred in 10.4% of pedicles. Intra-operatively, the absence of funnel was found in 24.5% of pedicles. In conclusion, thoracic pedicle screws using 5.0 mm at T1–T6 and 6.0 mm at T7–T12 can be inserted safely in Asian cadavers using the funnel technique despite having smaller thoracic pedicle morphometry.     

Anatomic evaluation of two different techniques for the percutaneous insertion of pedicle screws in the lumbar spine.

STUDY DESIGN: An in vitro study in which a human cadaver model was used to examine the accuracy of two different techniques of percutaneous pedicle screw insertion in the lumbar spine. OBJECTIVES: To investigate the in vitro misplacement rate of pedicle screw insertion for two different percutaneous techniques: 1) the well established Magerl technique, and 2) a new modified technique. SUMMARY OF BACKGROUND DATA: Numerous anatomic and biomechanical studies have been conducted to analyze the in vitro and in vivo characteristics of pedicle screw insertion in the lumbar spine via an open approach, whereas there is a lack of experimental data concerning the more sophisticated percutaneous procedure. METHODS: Thirty human specimens from L1 to S1 were separated into two groups (A and B). In group A, the screws were placed in accordance with the technique described by Magerl; in group B, a new modified technique developed by the authors' research group was used. After screw placement, the specimens were dissected, and pedicle violations were noted with respect to the degree and direction of the screw misplacement. RESULTS: The dissection of the specimens showed that of 360 pedicle screws, 37 were misplaced. This finding translates into an overall misplacement rate of 10%. With the Magerl technique, 23 pedicle violations (misplacement rate, 13%) were found; with the modified technique, only 14 dislocated pedicle screws (misplacement rate, 8%) were detected. This difference was not statistically significant (P = 0.118). In both groups, there were significantly more medical pedicle violations than lateral (32 medial and 5 lateral screw dislocations). The degree of the screw misplacements varied between 1.0 and 5.0 mm. The majority of pedicle violations (30 of 37) were minor, i.e., less than 3.0 mm. CONCLUSIONS: This in vitro study showed that the percutaneous technique of pedicle screw insertion in the lumbar spine is a safe and reliable procedure. Compared with the well-established Magerl technique, the new modified technique did not decrease the misplacement rate significantly, although less pedicle violations were found in the upper lumbar spine.     

Inserting pedicle screws in the upper thoracic spine without the use of fluoroscopy or image guidance. Is it safe?

Several studies have looked at accuracy of thoracic pedicle screw placement using fluoroscopy, image guidance, and anatomical landmarks. To our knowledge the upper thoracic spine (T1–T6) has not been specifically studied in the context of screw insertion and placement accuracy without the use of either image guidance or fluoroscopy. Our objective was to study the accuracy of upper thoracic screw placement without the use of fluoroscopy or image guidance, and report on implant related complications. A single surgeon inserted 60 screws in 13 consecutive non-scoliotic spine patients. These were the first 60 screws placed in the high thoracic spine in our institution. The most common diagnosis in our patient population was trauma. All screws were inserted using a modified Roy-Camille technique. Post-operative axial computed tomography (CT) images were obtained for each patient and analyzed by an independent senior radiologist for placement accuracy. Implant related complications were prospectively noted. No pedicle screw misplacement was found in 61.5% of the patients. In the remaining 38.5% of patients some misplacements were noted. Fifty-three screws out of the total 60 implanted were placed correctly within all the pedicle margins. The overall pedicle screw placement accuracy was 88.3% using our modified Roy-Camille technique. Five medial and two lateral violations were noted in the seven misplaced screws. One of the seven misplaced screws was considered to be questionable in terms of pedicle perforation. No implant related complications were noted. We found that inserting pedicle screws in the upper thoracic spine based solely on anatomical landmarks was safe with an accuracy comparable to that of published studies using image-guided navigation at the thoracic level.     

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.     

Effective in vivo radiation dose with image reconstruction controlled pedicle instrumentation vs. CT-based navigation

There is a rapid increase of computer-assisted surgery (CAS) in the spine for insertion of pedicle screws. In contrast to the traditional technique using fluoroscopy, CT is the primary source for surgical navigation systems. PURPOSE OF THE STUDY: To compare organ and effective doses of fluoroscopy-controlled versus computer-assisted pedicle screw insertion under the aspect of risk reduction and number needed to treat. MATERIALS AND METHODS: In 20 consecutive cases of traditional pedicle screw instrumentation under fluoroscopic control the effective doses were recorded in vivo and the organ doses then calculated. Simulating a spiral CT necessary for the 3-D-model for navigation we defined a spiral CT protocol for the instrumented levels and calculated organ and effective doses from Monte Carlo Results from CT examinations. RESULTS: Organ doses were clearly higher for the CT model than in any of the fluoroscopic procedures in vivo. The mean effective dose for the CT model was fifteen times higher than the fluoroscopic dose: 7.27 mSv versus 0.48 mSv. CONCLUSIONS: In experienced hands open pedicle screw insertion in the thoracic and lumbar spine using fluoroscopy-control requires a fifteen times lower radiation dose than do CT scans necessary for computer-assisted surgery. Regarding the published small percentage of neurological complications in traditional screw insertion technique the use of computer-assisted surgery in pedicle screw insertion using CT scan should be limited to carefully chosen indications. The development of navigation systems based on other data sources than CT should be encouraged.     

双平面骨科机器人系统辅助股骨颈骨折内固定的实验研究

目的 通过股骨近端模型骨的模拟手术,与传统方法徒手操作的临床病例进行对比,评价改进后的双平面骨科机器人系统辅助股骨颈骨折空心钉导针置入位置的准确性以及螺钉的平行性. 方法使用双平面骨科机器人系统对12根股骨近端模型骨进行辅助股骨颈空心钉置入的模拟手术,每例置入3枚导针,通过股骨颈截面的直接测量来评价机器人系统辅助操作的准确性;通过正、侧位X线片角度的测量和计算来评价机器人系统辅助下空心钉之间的平行性,与传统方法徒手操作的临床病例测算结果比较;同时比较两种操作方法所需的透视次数. 结果所有导针均一次成功置入,标本截面测量导针实际位置与规划位置相比误差范围在1 mm左右;对平行度参数的统计学分析结果显示正、侧位X线片上机器人辅助操作的螺钉平行度均优于徒手操作(P<0.05),稳定性也优于徒手操作(P<0.05);在透视次数上,机器人辅助操作组明显少于徒手操作组. 结论改进后的双平面骨科机器人系统可以有效地辅助完成股骨颈骨折空心钉内固定,导针位置的准确性能满足临床应用的需求.空心钉之间的平行性和操作的稳定性均明显优于传统的徒手操作,同时可以大大减少医患的放射线暴露时间.