Augmented reality navigation for spinal pedicle screw instrumentation using intraoperative 3D imaging

BACKGROUND CONTEXTDue to recent developments in augmented reality with head-mounted devices, holograms of a surgical plan can be displayed directly in the surgeon's field of view. To the best of our knowledge, three dimensional (3D) intraoperative fluoroscopy has not been explored for the use with holographic navigation by head-mounted devices in spine surgery.PURPOSETo evaluate the surgical accuracy of holographic pedicle screw navigation by head-mounted device using 3D intraoperative fluoroscopy.STUDY DESIGNIn this experimental cadaver study, the accuracy of surgical navigation using a head-mounted device was compared with navigation with a state-of-the-art pose-tracking system.METHODSThree lumbar cadaver spines were embedded in nontransparent agar gel, leaving only commonly visible anatomy in sight. Intraoperative registration of preoperative planning was achieved by 3D fluoroscopy and fiducial markers attached to lumbar vertebrae. Trackable custom-made drill sleeve guides enabled real-time navigation. In total, 20 K-wires were navigated into lumbar pedicles using AR-navigation, 10 K-wires by the state-of-the-art pose-tracking system. 3D models obtained from postexperimental CT scans were used to measure surgical accuracy. MF is the founder and shareholder of Incremed AG, a Balgrist University Hospital start-up focusing on the development of innovative techniques for surgical executions. The other authors declare no conflict of interest concerning the contents of this study. No external funding was received for this study.RESULTSNo significant difference in accuracy was measured between AR-navigated drillings and the gold standard with pose-tracking system with mean translational errors between entry points (3D vector distance; p=.85) of 3.4±1.6 mm compared with 3.2±2.0 mm, and mean angular errors between trajectories (3D angle; p=.30) of 4.3°±2.3° compared with 3.5°±1.4°.CONCLUSIONSIn conclusion, holographic navigation by use of a head-mounted device achieve accuracy comparable to the gold standard of high-end pose-tracking systems.CLINICAL SIGNIFICANCEThese promising results could result in a new way of surgical navigation with minimal infrastructural requirements but now have to be confirmed in clinical studies.     

骨科机器人辅助下脊柱椎弓根螺钉置入准确性与安全性的临床研究

目的:探讨骨科机器人与C形臂X线透视辅助下脊柱椎弓根螺钉置入的准确性与安全性.方法:对2019年1月至2020年8月采用外科治疗的36例脊柱疾患病例进行回顾性分析.36例患者中18例采用骨科机器人辅助下的椎弓根螺钉置入(观察组),男12例,女6例;年龄16～61 (38.44±3.60)岁;青少年脊柱侧弯1例,脊柱结核...     

Accuracy of fluoroscopically-assisted pedicle screw placement: analysis of 1,218 screws in 198 patients

Background contextWe retrospectively analyzed a total of 1,218 pedicle screws for accuracy, with postoperative computed tomography (CT), in 198 patients who were operated on between March 2004 and September 2012.PurposeTo determine the incidence of screw misplacement in patients who received a transpedicular screw fixation, with intraoperative fluoroscopy in the lateral and lateral with anteroposterior (AP) positions. The results are compared between the two groups.Study designRetrospective comparative study of accuracy of pedicle screw placement in thoracic and lumbar spine.Patient sampleThe sample consists of 198 consecutive patients who underwent transpedicular screw fixation.Outcome measuresAccuracy of screw placement was evaluated by postoperative CT scan. Misplacement was defined in cases where more than 25% of the screw size was residing outside the pedicle.MethodsThe indications for hardware placement, radiologic studies, patient demographics, and reoperation rates were recorded. Five hundred twenty-eight screws (Group A, n=81) were inserted into the vertebral body with the assistance of lateral fluoroscopy only, whereas 690 screws (Group B, n=117) were inserted with the assistance of lateral fluoroscopy, and the final positions of the screws were checked with AP fluoroscopy.ResultsA total of 1,218 screws were analyzed, with 962 screws placed at the lumbosacral region and 256 screws at the thoracic region. According to the postoperative CT scan, 27 screws (2.2%) were identified as breaching the pedicle. Nineteen of them (3.6%) were in Group A, whereas 8 (1.16%) were in Group B. The rate of pedicle breaches was significantly different between Group A and B (p=.0052). In Group A, the lateral violation of the pedicle was seen in 10 screws (1.9%), whereas medial violation was seen in 9 screws (1.7%). In Group B, the lateral violation of the pedicle was seen in six screws (0.87%), whereas medial violation was seen in two screws (0.29%). The medial and lateral penetration of screws were significantly different between Groups A and B (p<.05). A pedicle breach occurred in 21 patients, and 15 of them underwent a revision surgery to correct the misplaced screw. Of these patients, 11 (13.6%) were in Group A, and 4 (3.4%) were in Group B (p=.0335).ConclusionsIn this study, we evaluated and clarified the diagnostic value of intraoperative fluoroscopy in both the lateral and AP imaging that have not yet been evaluated in any comparative study. We concluded that the intraoperative use of fluoroscopy, especially in the AP position, significantly decreases the risk of screw misplacement and the results are comparable with other advanced techniques.     

Ultrasound-based navigated pedicle screw insertion without intraoperative radiation: feasibility study on porcine cadavers

BACKGROUNDNavigation systems for spinal fusion surgery rely on intraoperative computed tomography (CT) or fluoroscopy imaging. Both expose patient, surgeons and operating room staff to significant amounts of radiation. Alternative methods involving intraoperative ultrasound (iUS) imaging have recently shown promise for image-to-patient registration. Yet, the feasibility and safety of iUS navigation in spinal fusion have not been demonstrated.PURPOSETo evaluate the accuracy of pedicle screw insertion in lumbar and thoracolumbar spinal fusion using a fully automated iUS navigation system.STUDY DESIGNProspective porcine cadaver study.METHODSFive porcine cadavers were used to instrument the lumbar and thoracolumbar spine using posterior open surgery. During the procedure, iUS images were acquired and used to establish automatic registration between the anatomy and preoperative CT images. Navigation was performed with the preoperative CT using tracked instruments. The accuracy of the system was measured as the distance of manually collected points to the preoperative CT vertebral surface and compared against fiducial-based registration. A postoperative CT was acquired, and screw placements were manually verified. We report breach rates, as well as axial and sagittal screw deviations.RESULTSA total of 56 screws were inserted (5.50 mm diameter n=50, and 6.50 mm diameter n=6). Fifty-two screws were inserted safely without breach. Four screws (7.14%) presented a medial breach with an average deviation of 1.35±0.37 mm (all <2 mm). Two breaches were caused by 6.50 mm diameter screws, and two by 5.50 mm screws. For vertebrae instrumented with 5.50 mm screws, the average axial diameter of the pedicle was 9.29 mm leaving a 1.89 mm margin in the left and right pedicle. For vertebrae instrumented with 6.50 mm screws, the average axial diameter of the pedicle was 8.99 mm leaving a 1.24 mm error margin in the left and right pedicle. The average distance to the vertebral surface was 0.96 mm using iUS registration and 0.97 mm using fiducial-based registration.CONCLUSIONSWe successfully implanted all pedicle screws in the thoracolumbar spine using the ultrasound-based navigation system. All breaches recorded were minor (<2 mm) and the breach rate (7.14%) was comparable to existing literature. More investigation is needed to evaluate consistency, reproducibility, and performance in surgical context.CLINICAL SIGNIFICANCEIntraoperative US-based navigation is feasible and practical for pedicle screw insertion in a porcine model. It might be used as a low-cost and radiation-free alternative to intraoperative CT and fluoroscopy in the future.     

Comparison of Radiation Exposure in Lumbar Pedicle Screw Placement With Fluoroscopy Vs Computer-Assisted Image Guidance With Intraoperative Three-Dimensional Imaging

Background/objective: Little is known about the long-term effects of chronic exposure to ionizingradiation. Studies have shown that spine surgeons may be exposed to significantly more radiation than thatobserved in surgery on the appendicular skeleton. Computer-assisted image guidance systems have beenshown in preliminary studies to enable accurate instrumentation of the spine. Computer-assisted image guidance systems may havesignificant application to the surgical management of spinal trauma and deformity. The objective of this study was to compare C-arm fluoroscopy and computer-assisted imageguidance in terms of radiation exposure to the operative surgeon when placing pedicle screw-rod constructsin cadaver specimens.

Methods: Twelve single-level (2 contiguous vertebral bodies) lumbar pedicle screw-rod constructs (48screws) in 4 fresh cadavers were placed using standard C-arm fluoroscopy and computer-assisted imageguidance (Stealth Station with lso-C^3D ).Pedicle screw-rod constructs were placed at L1-L2, L3-L4, and L5-S1 in 4 fresh cadaver specimens. Imaging was alternated between C-arm fluoroscopy and computer-assistedimage guidance with Stealth Station lso-C^3D. Radiation exposure was measured using ringand badge dosimeters to monitor the thyroid, torso, and index finger. Postprocedure CT scans were obtained to judge accuracy of screw placement.

Results: Mean radiation exposure to the torso was 4.33 ± 2.66 mRemfor procedures performed with standard fluoroscopy and 0.33 ± 0.82 mRem for procedures performed with computer-assisted image guidance. This difference was statistically significant (P = 0.012). Radiation exposure to the index finger and thyroid was negligible for all procedures. The accuracy of screw placement was similar for both techniques.

Conclusions: Computer-assisted image guidance systems allow for the safe and accurate placement ofpedicle screw-rod constructs with a significant reduction in exposure to ionizing radiation to the torso of theoperating surgeon.     

骨科机器人辅助微创精准手术治疗胸腰段骨折的初步经验

目的 比较骨科机器人辅助经皮椎弓根螺钉内固定术治疗胸腰段骨折与传统后路椎弓根螺钉内固定术、C形臂X线机透视导航经皮椎弓根螺钉内固定术的临床疗效,探讨机器人辅助手术治疗胸腰段骨折的微创化与精准化价值。方法 2018年2月—2019年6月,收治无神经症状胸腰段骨折患者52例,18例接受机器人辅助经皮椎弓根螺钉内固定术治疗（机器人组）,15例接受C形臂X线机透视导航经皮椎弓根螺钉内固定术治疗（透视组）,19例接受传统后路椎弓根螺钉内固定术治疗（传统组）。记录并比较3组的手术时间、透视时间、辐射剂量、术中出血量、置钉准确率、卧床时间、住院天数,术前、术后6个月伤椎前缘相对高度及Cobb角,以及术前、术后3 d、术后6个月的疼痛视觉模拟量表（VAS）评分和日本骨科学会（JOA）评分。结果 所有手术顺利完成,未出现手术相关并发症。所有患者随访6~12个月,平均8个月。机器人组和透视组的手术时间、术中出血量、卧床时间、住院天数均少于传统组,差异有统计学意义（P<0.05）;透视组透视时间最长、辐射剂量最大,机器人组透视时间最短、辐射剂量最少,差异有统计学意义（P<0.05）;机器人组置钉准确率高于透视组和传统组,差异有统计学意义（P<0.05）。3组患者术后6个月伤椎前缘相对高度、Cobb角、VAS评分和JOA评分均较术前改善,差异有统计学意义（P<0.05）。3组术前、术后3 d和术后6个月伤椎前缘相对高度、Cobb角及JOA评分差异无统计学意义（P>0.05）;机器人组与透视组术后3 d VAS评分优于传统组且差异有统计学意义（P<0.05）,术前及术后6个月3组VAS评分差异无统计学意义（P>0.05）。结论 机器人辅助经皮内固定术是治疗无神经症状胸腰段骨折的有效方法,具有手术时间短、精度高、创伤小、辐射少、患者术后恢复快等优势,满足适应证时可作为优先选择。     

Minimally invasive percutaneous transpedicular screw fixation: increased accuracy and reduced radiation exposure by means of a novel electromagnetic navigation system

Background  

Minimally invasive percutaneous pedicle screw instrumentation methods may increase the need for intraoperative fluoroscopy, resulting in excessive radiation exposure for the patient, surgeon, and support staff. Electromagnetic field (EMF)-based navigation may aid more accurate placement of percutaneous pedicle screws while reducing fluoroscopic exposure. We compared the accuracy, time of insertion, and radiation exposure of EMF with traditional fluoroscopic percutaneous pedicle screw placement.     

基于术中三维影像的经皮枢椎椎弓根螺钉内固定治疗Hangman骨折

目的探讨基于术中三维影像的经皮枢椎椎弓根螺钉内固定治疗Hangman骨折的精准性和可行性。方法2015年11月—2016年11月,在O形臂X线机引导下采用经皮椎弓根螺钉内固定治疗Hangman骨折患者12例(微创组),其中4例行单侧C2椎弓根螺钉内固定,8例行双侧C2椎弓根螺钉内固定;同期在C形臂X线机引导下开放手术治疗Hangman骨折患者10例(开放组),均行C2椎弓根螺钉和C3侧块螺钉内固定植骨融合术。记录手术时间、术中辐射剂量、出血量、螺钉精准度、术前和术后6个月颈部疼痛视觉模拟量表(VAS)评分及颈椎功能障碍指数(NDI)。结果所有手术顺利完成,所有患者随访 6个月。微创组手术时间及术中出血量均低于开放组,但术中透视辐射剂量明显高于开放组,差异均有统计学意义(P 0.05)。微创组术后6个月VAS评分及NDI均优于开放组,差异均有统计学意义(P 0.05)。2组共置入螺钉60枚,其中C2椎弓根螺钉40枚,C3侧块螺钉20枚,均无螺钉相关的神经、血管损伤。术后1级螺钉,微创组有85%(17/20),开放组有80%(32/40),组间比较差异无统计学意义(P 0.05),且2组均无3级螺钉。结论联合微创和术中三维成像技术,可以安全精准地治疗Hangman骨折,并可降低软组织剥离损伤和术中出血量,可以作为Hangman骨折微创治疗的选择之一。     

Navigation of vertebro-pelvic fixations based on CT-fluoro matching

Different navigation procedures (based on 2D-, 3D-fluoroscopy or CT modalities) with their respective limitations are established in orthopedic surgery. The hypothesis is that intraoperative matching of different modalities (fluoro and CT) increases the precision of navigated screw placement and reduces the fluoroscopy time. Vertical unstable pelvic ring fractures of 12 patients were treated with vertebro-pelvic fixations (6 in the standard technique and 6 using the fluoro-CT navigation). An optimal osseous corridor could be determined by the navigation procedure increasing the overall precision of screw placement (no misplacement in the second group as compared to one malplaced pedicle screw in the standard group). The achieved screw lengths were [(mean ± SE) 78 ± 5 vs. 53 ± 4 mm, p < 0.001). Less invasive open approaches and a reduction of fluoroscopy time (time per screw in seconds: 121 vs. 62 s) were observed. CT-fluoro-matched navigation improves the intraoperative visualization of osseous structures and increases the precision of screw placement with less radiation exposure.     

Robot assisted navigated drilling for percutaneous pedicle screw placement: A preliminary animal study

Background:There is much more radiation exposure to the surgeons during minimally invasive pedicle screws placement. In order to ease the surgeon''s hand-eye coordination and to reduce the iatrogenic radiation injury to the surgeons, a robot assisted percutaneous pedicle screw placement is useful. This study assesses the feasibility and clinical value of robot assisted navigated drilling for pedicle screw placement and the results thus achieved formed the basis for the development of a new robot for pedicle screw fixation surgery.Results:Assisted by spine robot system, the average time for system registration was (343.4 ± 18.4) s, the average time for procedure of drilling one pedicle screw trajectory was (89.5 ± 6.1) s, times of fluoroscopy for drilling one pedicle screw were (2.9 ± 0.8) times. Overall, 12 (15.0%) of the 80 K-wires violated the pedicle wall. Four screws (5.0%) were medial to the pedicle and 8 (10.5%) were lateral. The number of K-wires wholly within the pedicle were 68 (85%).Conclusions:The preliminary study supports the view that computer assisted pedicle screw fixation using spinal robot is feasible and the robot can decrease the intraoperative fluoroscopy time during the minimally invasive pedicle screw fixation surgery. As spine robotic surgery is still in its infancy, further research in this field is worthwhile especially the accuracy of spine robot system should be improved.     

Safety and accuracy of robot-assisted placement of pedicle screws compared to conventional free-hand technique: a systematic review and meta-analysis

BACKGROUND CONTEXTThe introduction and integration of robot technology into modern spine surgery provides surgeons with millimeter accuracy for pedicle screw placement. Coupled with computer-based navigation platforms, robot-assisted spine surgery utilizes augmented reality to potentially improve the safety profile of instrumentation.PURPOSEIn this study, the authors seek to determine the safety and efficacy of robotic-assisted pedicle screw placement compared to conventional free-hand (FH) technique.STUDY DESIGN/SETTINGWe conducted a systematic review of the electronic databases using different MeSH terms from 1980 to 2020.OUTCOME MEASURESThe present study measures pedicle screw accuracy, complication rates, proximal-facet joint violation, intraoperative radiation time, radiation dosage, and length of surgery.RESULTSA total of 1,525 patients (7,379 pedicle screws) from 19 studies with 777 patients (51.0% with 3,684 pedicle screws) in the robotic-assisted group were included. Perfect pedicle screw accuracy, as categorized by Gerztbein-Robbin Grade A, was significantly superior with robotic-assisted surgery compared to FH-technique (Odds ratio [OR]: 1.68, 95% confidence interval [CI]: 1.20–2.35; p=.003). Similarly, clinically acceptable pedicle screw accuracy (Grade A+B) was significantly higher with robotic-assisted surgery versus FH-technique (OR: 1.54, 95% CI: 1.01–2.37; p=.05). Furthermore, the complication rates and proximal-facet joint violation were 69% (OR: 0.31, 95% CI: 0.20–0.48; p<.00001) and 92% less likely (OR: 0.08, 95% CI: 0.03–0.20; p<.00001) with robotic-assisted surgery versus FH-group. Robotic-assisted pedicle screw implantation significantly reduced intraoperative radiation time (MD: ?5.30, 95% CI: ?6.83–3.76; p<.00001) and radiation dosage (MD: ?3.70, 95% CI: ?4.80–2.60; p<.00001) compared to the conventional FH-group. However, the length of surgery was significantly higher with robotic-assisted surgery (MD: 22.70, 95% CI: 6.57–38.83; p=.006) compared to the FH-group.CONCLUSIONThis meta-analysis corroborates the accuracy of robot-assisted pedicle screw placement.     

骨科天玑机器人在手术治疗胸腰椎骨折的临床应用

目的：探讨骨科天玑机器人在微创经皮椎弓根螺钉内固定术治疗胸腰椎骨折的临床应用。方法：回顾性分析2018年6月至2020年1月甘肃省人民医院收治的46例胸腰椎骨折患者的临床资料。根据手术所应用的辅助设备不同,将其分为C形臂X线加机器人辅助置钉组（观察组）和单纯C形臂X辅助下置钉组（对照组）。其中观察组22例,男12例,女10例;年龄24~61（40.23±12.19）岁;T₁₁ 3例,T₁₂ 8例,L₁ 9例,L₂ 2例。对照组24例,男15例,女9例;年龄26~58（42.88±10.31）岁;T₁₁ 3例,T₁₂ 10例,L₁ 7例,L₂ 4例。分别记录并比较两组的手术时间、术中透视次数、术中出血量、住院天数及术后并发症,比较术前及术后3 d,1周及3个月的视觉模拟评分（visual analogue scale,VAS）评分,手术前后的伤椎矢状面Cobb角及椎体前缘高度百分比,并收集术后CT影像,依据Gertzbein-Robbins分类标准对置钉的准确性进行评估。结果：所有患者获得随访,时间5~12（7.07±0.83）个月。两组患者术中出血量、手术时间、住院天数比较差异无统计学意义（P>0.05）。术中透视次数观察组为（5.62±0.51）次,对照组为（12.54±0.52）次,两组差异有统计学意义（P<0.05）。两组术后各时间点VAS、伤椎前缘高度百分比及伤椎矢状面Cobb角较术前改善（P<0.05）,但两组比较差异无统计学意义（P>0.05）。术后对照组出现1例切口感染,经积极换药后痊愈。两组患者均未出现螺钉松动、断裂等严重并发症,两组之间并发症的发生率比较差异无统计学意义（P>0.05）。观察组和对照组术后置钉准确率分别为98.4%（126/128）和90.3%（121/134）,两组比较差异有统计学意义（P<0.05）。结论：在胸腰椎骨折的手术治疗中骨科天玑机器人辅助下椎弓根螺钉置入与单纯C形臂X线透视相比,前者克服了术者生理性震颤、疲劳及术中多次透视等缺点,提高了置钉准确率,是一种更加准确、安全的胸腰椎骨折椎弓根螺钉置入方式。     

Management decisions for adolescent idiopathic scoliosis significantly affect patient radiation exposure

Background contextAdolescent idiopathic scoliosis (AIS) patients treated before the 1990s have a 1% to 2% increased lifetime risk of developing breast and thyroid cancer as a result of ionizing radiation from plain radiographs. Although present plain radiographic techniques have been able to reduce some of the radiation exposure, modern treatment algorithms for scoliosis often include computed tomography (CT) and intraoperative fluoroscopy. The exact magnitude of exposure to ionizing radiation in adolescents during modern scoliosis treatment is therefore unclear.PurposeTo determine the difference in radiation exposures in patients undergoing various forms of treatment for AIS.Study designRetrospective cohort.Patient samplePatients aged 9 to 18 years with a diagnosis of AIS, followed and/or treated with nonoperative or operative management for a minimum of 2 years.Outcome measuresNumber of radiographs and total radiation exposure calculated.MethodsThe charts and radiographs of patients managed for AIS at a single institution between September 2007 and January 2012 were reviewed. Patients were divided into three groups: operative group, braced group, and observation group. Patient demographics, Cobb angles, and curve types were recorded. The number of radiographs per year that each patient received and the total radiation dose were recorded. The plain radiographic radiation exposure was then combined with the direct exposure recording from ancillary tests, such as fluoroscopy and CT, and a radiation exposure rate was calculated (mrad/y). A single-factor analysis of variance (α=0.01) with a Tukey honest significant difference post hoc analysis was used to test significance between groups.ResultsTwo hundred sixty-seven patients were evaluated: 86 operative, 80 brace, and 101 observation. All groups had similar demographics and curve type distribution. The mean initial Cobb angle at presentation was significantly different between the groups: operative (57°±11°), brace (24°±7.9°), and observation (18°±9.4°) (p<.01). There was a significant difference among the groups in terms of the mean number of radiographs received per year; operative group, 12.2 (95% confidence interval [CI]: 10.8–13.5; p<.001); braced group, 5.7 (95% CI: 5.2–6.2; p<.001), and observed group, 3.5 (95% CI: 3.160–3.864; p<.001). The operative group received 1,400 mrad per year (95% CI: 1,350–1,844; p<.001), braced group received 700 mrad per year (95% CI: 598–716; p<.001), and observed group received 400 mrad per year (95% CI: 363–444; p<.001). Importantly, 78% of radiation in the operative group was attributable to the operative fluoroscopy exposure.ConclusionsSignificant differences exist in the total radiation exposure in scoliosis patients with different treatment regimens, with operative patients receiving approximately 8 to 14 times more radiation than braced patients or those undergoing observation alone, respectively. Operative patients also receive more than twice the radiation per year than braced or observed patients. Almost 78% of the annual radiation exposure for operative patients occurs intraoperatively. Because children are notably more sensitive to the carcinogenic effects of ionizing radiation, judicious use of present imaging methods and a search for newer imaging methods with limited ionizing radiation should be undertaken.     

Effective dose of radiation per screw in surgery of adolescent idiopathic scoliosis: matched pair analysis of 293 pedicle screws inserted using three different techniques

PurposeReports on heterogenous groups of patients have indicated that pedicle screw insertion guided by navigation (PIN) leads to, for the patient, higher doses of radiation compared with pedicle screw insertion guided by fluoroscopy (PIF). This would be a major concern, especially in paediatric deformity correction.MethodsAfter a power analysis (aiming at > 0.8) 293 pedicle screws which were inserted in patients with adolescent idiopathic scoliosis were analyzed by comparing effective dose and fluoroscopy time per screw for three different techniques. Groups 2 and 3 were matched to Group 1 by Lenke type of scoliosis. Group 1 were prospectively enrolled consecutive patients that have been operated on by PIN with image acquisition by preoperative CT scan (CTS). Group 2 were consecutive retrospectively matched patients who have been operated on by PIN with image acquisition by an intraoperative 3D scan (3DS). Group 3 were consecutive retrospectively matched patients who have been operated on by PIF.ResultsMean dose of radiation per screw was 1.0 mSv (sd 0.8) per screw in CTS patients, 0.025 mSv (sd 0.001) per screw in 3DS patients and 0.781 mSv (sd 0.12) per screw in PIF patients. The difference was significant (p < 0.0001).ConclusionWhen we compared different techniques of navigation, navigation by image acquisition with CTS showed a significantly higher (by 97.5%) dose of radiation per screw for the patient than navigation by image acquisition by a 3DS. Navigation by 3DS showed significantly lower effective dose per screw for the adolescent patients than the fluoroscopic technique.Level of Evidence:II     

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.     

Accuracy of patient-specific template-guided vs. free-hand fluoroscopically controlled pedicle screw placement in the thoracic and lumbar spine: a randomized cadaveric study

Purpose

Dorsal spinal instrumentation with pedicle screw constructs is considered the gold standard for numerous spinal pathologies. Screw misplacement is biomechanically disadvantageous and may create severe complications. The aim of this study was to assess the accuracy of patient-specific template-guided pedicle screw placement in the thoracic and lumbar spine compared to the free-hand technique with fluoroscopy.

Methods

Patient-specific targeting guides were used for pedicle screw placement from Th2–L5 in three cadaveric specimens by three surgeons with different experience levels. Instrumentation for each side and level was randomized (template-guided vs. free-hand). Accuracy was assessed by computed tomography (CT), considering perforations of <2 mm as acceptable (safe zone). Time efficiency, radiation exposure and dependencies on surgical experience were compared between the two techniques.

Results

96 screws were inserted with an equal distribution of 48 screws (50 %) in each group. 58 % (n = 28) of template-guided (without fluoroscopy) vs. 44 % (n = 21) of free-hand screws (with fluoroscopy) were fully contained within the pedicle (p = 0.153). 97.9 % (n = 47) of template-guided vs. 81.3 % (n = 39) of free-hand screws were within the 2 mm safe zone (p = 0.008). The mean time for instrumentation per level was 01:14 ± 00:37 for the template-guided vs. 01:40 ± 00:59 min for the free-hand technique (p = 0.013), respectively. Increased radiation exposure was highly associated with lesser experience of the surgeon with the free-hand technique.

Conclusions

In a cadaver model, template-guided pedicle screw placement is faster considering intraoperative instrumentation time, has a higher accuracy particularly in the thoracic spine and creates less intraoperative radiation exposure compared to the free-hand technique.

     

Computer tomography assessment of pedicle screw placement in thoracic spine: comparison between free hand and a generic 3D-based navigation techniques

Introduction

Although pedicle screw fixation is a well-established technique for the lumbar spine, screw placement in the thoracic spine is more challenging because of the smaller pedicle size and more complex 3D anatomy. The intraoperative use of image guidance devices may allow surgeons a safer, more accurate method for placing thoracic pedicle screws while limiting radiation exposure. This generic 3D imaging technique is a new generation intraoperative CT imaging system designed without compromise to address the needs of a modern OR.

Aim

The aim of our study was to check the accuracy of this generic 3D navigated pedicle screw implants in comparison to free hand technique described by Roy-Camille at the thoracic spine using CT scans.

Material and methods

The material of this study was divided into two groups: free hand group (group I) (18 patients; 108 screws) and 3D group (27 patients; 100 screws). The patients were operated upon from January 2009 to March 2010. Screw implantation was performed during internal fixation for fractures, tumors, and spondylodiscitis of the thoracic spine as well as for degenerative lumbar scoliosis.

Results

The accuracy rate in our work was 89.8 % in the free hand group compared to 98 % in the generic 3D navigated group.

Conclusion

In conclusion, 3D navigation-assisted pedicle screw placement is superior to free hand technique in the thoracic spine.     

术中三维导航辅助微创经椎间孔入路腰椎椎间融合术中置钉偏出方向及程度分析

目的比较三维导航辅助Quadrant通道下微创经椎间孔入路腰椎椎间融合术(MIS-TLIF)与C形臂X线机透视下行MIS-TLIF治疗腰椎退行性疾病的置钉偏出方向及程度,并探讨三维导航在MIS-TLIF中的应用价值。方法回顾性分析2017年12月—2018年12月接受MIS-TLIF治疗的108例腰椎退行性疾病患者临床资料,术中采用三维导航辅助58例(导航组),采用C形臂X线机透视辅助50例(透视组)。收集2组患者的基本信息、手术时间、术中出血量,通过术后CT扫描与三维重建记录螺钉穿破骨皮质位置并测量穿透皮质距离。结果 2组患者年龄、性别、体质量指数、术前诊断及手术节段构成比差异无统计学意义(P 0.05)。导航组比透视组手术时间短、术中出血少,差异有统计学意义(P 0.05)。导航组共置钉272枚,皮质穿破率为9.9%;透视组共置钉236枚,皮质穿破率为22.5%,组间差异有统计学意义(P 0.05)。导航组内、外、前侧皮质及椎间孔穿破率分别为4.8%、1.5%、3.3%和0.3%,4个方向穿破率均低于透视组的8.5%、8.5%、4.7%和0.8%,但仅内、外侧皮质穿破率差异有统计学意义(P 0.05)。2组的螺钉穿破率除2级外,其他各级差异均有统计学意义(P 0.05)。2组患者术后6个月及末次随访时腰痛、下肢痛视觉模拟量表(VAS)评分和Oswestry功能障碍指数(ODI)均较术前显著改善,差异有统计学意义(P 0.05),各时间点组间比较差异无统计学意义(P 0.05)。结论与C形臂X线机透视下MIS-TLIF相比,导航辅助MIS-TLIF治疗腰椎退行性疾病从手术节段定位、钉道制备、椎管减压到融合器置入,全程提供三维影像,能提升整体置钉精确度,降低内、外侧皮质穿破率,具有手术时间短、出血量少、并发症少的特点,可以获得安全、有效的治疗结果。     

Economic study: a cost-effectiveness analysis of an intraoperative compared with a preoperative image-guided system in lumbar pedicle screw fixation in patients with degenerative spondylolisthesis

Background contextIn spinal surgery, newly developed technology seems to play a key role, especially with the use of computer-assisted image-guided navigation, giving excellent results. However, these tools are expensive and may not be affordable for many facilities.PurposeTo compare the cost-effectiveness of preoperative versus intraoperative CT (computed tomography) guidance in spinal surgery.Study designA retrospective economic study.MethodsA cost-effectiveness study was performed analyzing the overall costs of a population of patients operated on for lumbar degenerative spondylolisthesis using an image-guided system (IGS) based on a CT scan. The population was divided into two groups according to the type of CT data set acquisition adopted: Group I (IGS based on a preoperative spiral CT scan), Group II (IGS based on an intraoperative CT scan—O-Arm system). The costs associated with each procedure were assessed through a process analysis, where clinical procedures were broken down into single phases and the related costs from each phase were evaluated. No benefits in any form have been or will be received from commercial parties directly or indirectly related to the subject of this article.ResultsFour hundred ninety-nine patients met the criteria for this study. In total, 2,542 screws were inserted with IGS. Baseline data were similar for the two groups, as were hospitalization and complications. The surgical time was 119±43 minutes in Group I and 92±31 minutes in Group II. The full cost of the two procedures was analyzed: the mean cost, using the O-Arm system (Group II), was found to be €255.83 (3.80%) less than the cost of Group I. Moreover, the O-Arm system was also used in other surgical procedures as an intraoperative control, thus reducing the final costs of radiologic examinations (a reduction of around 550 CT scans/year).ConclusionsIn conclusion, the authors of the study are of the opinion that the surgical procedure of pedicle screw fixation, using a CT-based computer-guidance system with support of the O-Arm system, allows a shortening of procedure time that might improve the clinical result. However, the present study failed to determine a clear cost-effectiveness with respect to other CT-based IGS.     

CT-navigation versus fluoroscopy-guided placement of pedicle screws at the thoracolumbar spine: single center experience of 4,500 screws

Purpose

Single center evaluation of the placement accuracy of thoracolumbar pedicle screws implanted either with fluoroscopy or under CT-navigation using 3D-reconstruction and intraoperative computed tomography control of the screw position. There is in fact a huge variation in the reported placement accuracy of pedicle screws, especially concerning the screw placement under conventional fluoroscopy most notably due to the lack of the definition of screw misplacement, combined with a potpourri of postinstrumentation evaluation methods.

Methods

The operation data of 1,006 patients operated on in our clinic between 1995 and 2005 is analyzed retrospectively. There were 2,422 screws placed with the help of CT-navigation compared to 2,002 screws placed under fluoroscopy. The postoperative computed tomography images were reviewed by a radiologist and an independent spine surgeon.

Results

In the lumbar spine, the placement accuracy was 96.4 % for CT-navigated screws and 93.9 % for pedicle screws placed under fluoroscopy, respectively. This difference in accuracy was statistically significant (Fishers Exact Test, p = 0.001). The difference in accuracy became more impressing in the thoracic spine, with a placement accuracy of 95.5 % in the CT-navigation group, compared to 79.0 % accuracy in the fluoroscopy group (p < 0.001).

Conclusion

This study underlines the relevance of CT-navigation-guided pedicle screw placement, especially when instrumentation of the middle and upper thoracic spine is carried out.