|Year : 2016 | Volume
| Issue : 1 | Page : 6-13
Accuracy of spinal screw fixation using intraoperative O-arm navigation: Consecutive series of 118 screws
Shao-Wei Feng, Yun-Ju Yang, Chiao-Zhu Li, Meng-Chi Lin, Tzu-Tsao Chung, Yuan-Hao Chen
Department of Neurological Surgery, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
|Date of Submission||23-Nov-2015|
|Date of Decision||29-Nov-2015|
|Date of Acceptance||01-Dec-2015|
|Date of Web Publication||23-Feb-2016|
No. 325, Section 2, Cheng-Kung Road, Neihu 11490, Taipei, Taiwan
Republic of China
Source of Support: None, Conflict of Interest: None
Background: Imaging-guided surgery provides intraoperative realtime navigation for spinal surgery to prevent neurovascular injury. However, the initial experience of O-arm three-dimensional (3D) navigation is less clarified. The study aims to evaluate the accuracy of O-arm 3D navigation-assisted spinal implantation. Materials and Methods: Total 118 transpedicle/lateral mass screws in 17 consecutive patients performed through O-arm 3D computed tomography (CT) imaging navigation. Screws accuracy, Visual analogue scale (VAS), and operation time were assessed. O-arm 3D navigation included 96 pedicle screws and 22 lateral mass screws. Results: There accuracy rate of screw implantation was 96.6% (114/118) without breach (Grade 0), whereas 3.4% (4/118) breach between 2 and 4 mm (Grade 2). In the cervical spinal, 12 pedicle screws were placed in 4 patients; 16.7% (2/12) exhibited a Grade 2 breach in one patient, who developed a new neurological deficit and required revision. In the lumbosacral spine, 2.78% (2/72) exhibited a Grade 2 breach in 2 patients. The mean ± standard deviation VAS of the patients in postoperative and preoperative status was 1.47 ± 0.50 and 3.58 ± 1.00, respectively. The operation time was significantly longer in O-arm navigation than in C-arm guidance (426.5 ± 180.4 vs. 317.9 ± 133.6 min, P < 0.05). Conclusion: O-arm 3D navigation achieves a relatively high accuracy of pedicle and lateral mass screws implantation. The accumulation of experience for O-arm 3D CT during initial learning curve is still warranted to promote the accuracy of screws position and shorten operation time.
Keywords: O-arm three-dimensional navigation, spinal instrumentation, pedicle screw, lateral mass screw
|How to cite this article:|
Feng SW, Yang YJ, Li CZ, Lin MC, Chung TT, Chen YH. Accuracy of spinal screw fixation using intraoperative O-arm navigation: Consecutive series of 118 screws. J Med Sci 2016;36:6-13
|How to cite this URL:|
Feng SW, Yang YJ, Li CZ, Lin MC, Chung TT, Chen YH. Accuracy of spinal screw fixation using intraoperative O-arm navigation: Consecutive series of 118 screws. J Med Sci [serial online] 2016 [cited 2020 Dec 2];36:6-13. Available from: https://www.jmedscindmc.com/text.asp?2016/36/1/6/177169
| Introduction|| |
With the advances in modern spinal surgery, transpedicle screws have been well established for the treatment of spinal disease. However, malpositioning of the instrumentation may lead to severe neurological injuries or vessels damage, even with conventional fluoroscopic C-arm guidance during the procedure. There have been rapid technological advancements in image-guided spinal surgery in the past decade, and this has led to a lower incidence of malpositioning spinal instrumentation.,
There used to be only three main types of spinal image guidance; preoperative computed tomography (CT)-based, fluoroscopy-based, and three-dimensional (3D) fluoroscopy-based. However, the anatomy of the spine in the prone position during surgery may not be the same as preoperative CT images, thereby leading to registration bias and a longer operative time. Conventional fluoroscopy-based and 3D fluoroscopy-based imaging systems cannot provide a high enough image quality to monitor the implant location during the operation. However, the new imaging technique of intraoperative CT image-guided navigation has greatly improved the image quality and virtual real-time 3D navigation in spinal surgery. The O-arm/Stealth system (Medtronic, Inc., Minneapolis, MN, USA) is one such system. The cone beam-based images of the O-arm system combined with a flat-panel detector can configure two-dimensional (2D) fluoroscopic images and 3D CT images. The 2D images have a bigger and better image quality than the general C-arm. The full 360° cone-beam scans in a closed O-shape can provide the 3D imaging within 30 s depending on the required resolution. The 3D images are then automatically transferred to the navigation computer workstation (StealthStation, Medtronic, Co, USA) for automatic registration, offering real-time intraoperative 3D navigation for precise, and safe implantation of spinal instrumentation with exposure to a small dose of radiation for the surgeons.,,, However, the initial experience of O-arm 3D navigation is less clarified.
In this study, we present our preliminary results using O-arm 3D imaging navigation in the implantation of spinal instrumentation. This study also provides a solution for challenging cases with severe degenerative lumbar scoliosis using intraoperative O-arm 3D navigation to overcome the difficulty in handling severe deformities of anatomical structure and distortion of pedicle trajectory to conduct transpedicle screw fixation precisely. The operation time, learning curves, and potential technique tips were addressed.
| Materials and Methods|| |
This study was approved by the Institutional Review Board of our institute (approval number: 1-102-05-032). Between October 2013 and March 2014, 118 lateral mass/pedicle screws instrumentation were implanted in 17 consecutive patients in the cervical (give number), thoracic (give number), or lumbar (give number) spine under O-arm 3D navigation with Stealth system [Table 1].
Indications of O-arm three-dimensional computed tomography navigation
The indications of the O-arm 3D navigation for screws placement followed the previous studies, including (1) Patient with severe spinal deformity, rotation, and distorted anatomical landmark, (2) posterior cervical spinal surgery, (3) high thoracic spinal surgery, and (4) patient with very small pedicle size.,,,
All patients were placed in the prone position with appropriate padding and sterile preparation. A Mayfield skull clamp was used in the patients who underwent cervical instrumentation. Both transpedicle screws and lateral mass screws were inserted in the cervical region. The skin incision was longitudinal midline or paramidline to expose the cervical, thoracic, or lumbar-sacrum region where instrumentation was to be performed based on the surgical level. Two methods were used to affix the Stealth reference arc to the patients: (1) Directly affix the reference arc to the exposed spinous process or (2) a percutaneous pin was placed over the posterior iliac crest, and then the reference arc was attached to the iliac pin. The spinal instrumentations were placed before or after decompression procedures in all patients. The 3D CT images were obtained by the O-arm system and then transferred to a workstation (StealthStation, Medtronic). The registration was made automatically. The workstation calculated multiplanar and 3D images, and the surgeons could use these realtime images and reference-guiding device to decide the trajectory of the screws. A ball-tipped feeler probe was used to make the screw tract. Even though the Medtronic screw system has its own navigation screwdriver, we implanted the screws free hand along the pathway made by the navigation probe. After the screws had been placed, the O-arm 3D images were checked intraoperatively.
Accuracy of screw position confirmation with the O-arm
Intraoperative CT images were obtained from the O-arm system to assess the position of the screws. Based on the CT images, the position of the screws was classified as grade 0, without perforation of the pedicle or lateral mass; Grade 1, with perforation of the cortex <2 mm; Grade 2, perforation of the cortex between 2 and 4 mm; and Grade 3, perforation of the cortex >4 mm [Table 2]., Once a cortex breach was found, the length of breach was calculated.
Clinical outcomes assessment
Neurological examinations and visual analog pain score (VAS) preoperatively and postoperatively were assessed in patients undergoing O-arm 3D CT-navigated implantation of lateral mass/pedicle screws.
Operation time assessment
The total operation time was recorded in our patient population underwent the O-arm 3D CT-guidance for spinal instrumentation implantation in comparison with matched control group with the same kind screws and the same amount of implantation with conventional C-arm guidance. The statistic difference of operation time was assessed by Student's t-test.
| Results|| |
Utilizing O-arm 3D imaging/navigation achieved 96.6% accuracy in terms of pedicle/lateral mass screw placement (e.g., without spinal breach). Lateral mass screws were placed in 4 patients, 3 of 4 also had placed transpedicle screws. In the cervical spine, 12 pedicle screws were placed in 4 patients with the O-arm; 83.3% were applied without breach (10/12, Grade 0). However, 16.7% (2/12) exhibited a Grade 2 breach (1 patient) that patient developed a new neurological deficit and required operative revision. In the thoracic spine, there was 100% (12/12, Grade 0) accuracy (e.g., no breaches). Finally, the accuracy of pedicle screw instrumentation in the lumbosacral spine was 97.22% (70/72, Grade 0) without a breach in 10/12 patients; 2 screws 2.78% (2/72) exhibited a Grade 2 breach but without newly onset neurological deficits, and required no additional surgery. Furthermore, the accuracy was 100% (20/20, Grade 0) without breach for severe degenerative lumbar scoliosis [Table 3].
Clinical outcome assessed by visual analog pain score
All but one patient demonstrated significant clinical/neurological improvement. The VAS significantly improved in postoperative versus preoperative status (1.47 ± 0.50 vs. 3.58 ± 1.00 scores).
The mean operation time of surgery with O-arm navigation is 426.5 min, compare with convention C-arm guiding is 317.9 min. The O-arm group needs much longer time than C-arm group (P = 0.0312, t-test).
Illustration of a challenging case
The posterior approach with implantation of spinal instrumentation under C-arm guidance is extremely difficult because of severe deformity, hypertrophy, and rotation of the bone leading to difficulty in identifying the spinal anatomy. In our patients, O-arm 3D navigation provided excellent imaging guidance in dealing with difficult pedicle screw placement in a patient with severe degenerative scoliosis [Figure 1]a and b. This patient was a 77-year-old male with degenerative scoliosis and severe spinal stenosis from T12 to L5 and bilateral radiculopathy. He underwent bilateral hemilaminectomies at T12, total laminectomies at L2, L3, and L4 with discectomy at L4-L5, and internal fixation with pedicle screws from L2 to L5 [Figure 1]c-f. Postoperatively, his symptoms significantly improved, and the screws were placed perfectly without any medial or lateral breach.
|Figure 1: Case illustration in patient with severe degenerative lumbar scoliosis underwent pedicle screw implantation using O-arm navigation. Preoperative lateral view (a), anterioposterior view (b) of the lumbar spine, intraoperative anterioposterior view (c) acquired from the O-arm system. Postoperative lateral view (d), and anterioposterior view (e), and intraoperative axial view (f) obtained from the O-arm system|
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Notably, there were no cerebrospinal fluid (CSF) leaks or vascular injuries in this series. However, two patients sustained a Grade 2 pedicle screws breach in the lumbar spine in a patient who sustained no neurological deficit (e.g., no new deficit or CSF leak). However, one patient with a complicated Grade 2 internal breach following the placement of two cervical pedicle screws (e.g., confirmed utilizing postoperative CT) [Figure 2]a and b compromising the C5 and C7 roots, respectively, developed the new onset of right upper extremity weakness [Figure 2]a-d. The patient required revision of these pedicle screws with O-arm 3D navigation [Figure 2]e and f, and her deficit improved (e.g., from preoperative Grade 2 to postoperative Grade 3 at 4 weeks and Grade 4 at 4 months).
|Figure 2: The management in patient 2 with malposition of cervical pedicle screw using O-arm navigation. (a and b) Postoperative O-arm imaging found malposition of cervical pedicle screw with medial breach (arrow) at right C5 and C7 nerve foramens. (c and d) Postoperative computed tomography scan re-confirmed the medial breach. (e and f) Post revision O-arm imaging showed an ideal position of the screw in the cervical pedicle|
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| Discussion|| |
The initial experience of O-arm 3D navigation achieves a relatively high accuracy of pedicle and lateral mass screws implantation. The operation spends more time. The accumulation of experience for O-arm 3D navigation during initial learning curve is still warranted to promote the accuracy of screws position and shorten operation time.
Currently, there are still some debates for the indications of O-arm 3D navigation. Since the O-arm system is expensive and not widely available, we suggest that at the lumber level, the free-hand technique of transpedicle screw implantation under conventional fluoroscopy guidance still provides acceptable accuracy and safety. This is supported by a study by Shin et al., in which they stated that it is unnecessary to routinely use the O-arm system for every lumbar or lower thoracic spinal surgery to insert transpedicle screws. Patient with severe spinal deformity, rotation and distorted anatomical landmark are very challenging for the screw implantation due to hard to found the transpedicle insertion site under 2D C-arm guiding. In cervical spinal surgery for transpedicle screw implantation, a slight internal breach can lead to severe neurological deficits, and a lateral breach can injure the vertebral artery.,, The diameter of the cervical pedicle is smaller than other regions, and it is gradually being accepted that using O-arm 3D navigation at the posterior cervical and high thoracic levels can increase the accuracy., Jeswani et al. reported O-arm 3D navigation provide the accurate and safety pedicle screw implantation in small (<3 mm) and very small (<2 mm) pedicle size. Pedicle screws implantation for the congenital spinal deformity is difficult, cause of abnormal structure, altered pedicle direction, and anatomy. Under O-arm 3D navigation, the surgeon can perform screw implantation more precisely than the conventional way. Our study further supports the accuracy and safety of the implantation of transpedicle screws under O-arm imaging guidance for patients with severe lumbar spinal deformities.
With the increasing use of transpedicle screws to treat unstable spinal spondylolisthesis, it is important to increase the accuracy of transpedicle screw implantation to avoid complications such as injuring the spinal nerve and critical vessels to prevent neurological deficits. Image guidance techniques have been used in spinal surgery since the early 1990s. Most of these devices have been preoperative CT systems, in which a CT scan is taken before surgery and registration are done during the surgery using a navigation workstation by using landmarks on the skin. However, the anatomy of the spine may change during surgery because the position is different in the preoperative CT (supine position) and operational posture, especially in the cervical spine due to its flexibility. In a cadaveric study on cervical pedicle screw insertion, the malposition rate was not statistically significantly different between the preoperative CT navigation group and the traditional free-hand group. Many studies have supported a more accurate implantation of pedicle screws under O-arm 3D CT imaging assistance.,,,,
Our data revealed that operation time is longer in the group of O-arm guiding than in C-arm guiding group. Consistently, O-arm group needs longer preparation time for the setup of O-arm,  the learning curve for a beginner is steep. For setting the O-arm, the machine should move to the operation table in the correct location to scan the image. The operation crews should learn how to operate the O-arm with connecting the working station for auto-registration and setting the working station sensor in the operation room. The surgeon should familiar with the registered tool, the navigation system, and the spinal 3D anatomy to perform the instrumentation implantation. After well training and more experience, the surgery with O-arm will spend less time and getting higher accuracy rate.,
The radiation dosage in patent underwent O-arm navigation is 1.83 mSv, which equaled approximately half of a traditional diagnosed CT scanner (around 3.6 mSv)., The radiation exposed to the operation surgeon and scrub nurse are lower because when the O-arm began to scan, the member could take cover by the portable lead wall screen in the operation room or leave the theater.
[Table 4] summarized the literature search via PubMed for related articles on the accuracy of spinal instrumentation using O-arm navigation.,,,,,,,,,,,,,,, Our results are comparable with other studies in that thoracic, and lumbar pedicle screws had a good accuracy rate under the O-arm navigation. Our pedicle malposition rate in thoracic and lumbar-sacrum regions was 2.78% (2/72). Lateral mass had the same accuracy as in the report by Attia et al.,,,,,,,,,,,,,,, Cervical pedicle screws had a lower accuracy rate in our study with a malposition rate of 16.7% (2/12). Ishikawa et al. reported a cervical pedicle screw malposition rate of 11.2%, which was much higher than any other area under O-arm navigation. This may be because the cervical alignment changes when force is applied on the cervical spine to create a hole by an awl or probe even with a Mayfield rigid 3-point skeletal fixation.
|Table 4: Malposition rate of spinal screw fixation using O-arm navigation|
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Potential technique tips of O-arm navigation for spinal instrumentation includes never interrupted the reference arc when insertion of screws into the spine. The reference fiducial maker should always keep clean without contamination by blood to avoid discontinuation of navigation. The alteration of reference arc position should scan the spine to obtain new images again for navigation. This situation leads to operation time longer and makes patient exposure higher radiation dosage. Moreover, in the cervical spinal posterior screws implantation, the cervical alignment change or the reference arc move when force is applied on the cervical spine to create a hole by an awl or probe. This condition will make the navigation discontinue; we can use the navigation tool to make sure the insertion site and use the small burr to decortication first. This procedure can make the probe more easily to create a hole for screws implantation and less force delivery to the cervical spine that can avoid cervical alignment change or the reference arc movement. Furthermore, in the lumbar spinal screws implantation, if we performed decompression first, then we fix the reference to the adjacent spinal process for the navigation. It is possible that the frame will move because of the spinal structure is not as stable as before decompression. It is better to fix the reference arc to the posterior iliac crest when we decided to perform the decompression procedure before the screws implantation. With O-arm 3D images guidance, the reference fiducially markers can sometimes change due to respiratory movements and elasticity of the surgical table when using a probe to detect the trajectory of the screws. Importantly, using a hammer to punch a hole in the bone marrow can lead to loosening of the position of the reference markers. Double-checking the reference points should be performed before advancing the trajectory into the pedicle. It has been reported that intraoperative neurophysiological monitoring can provide additional value for the intraoperative real-time identification of potential neurological injuries.,,, Intraoperatively, neurophysiological monitoring can immediately detect changes in neurophysiological evoked potentials, providing additional information for the surgeons' reference.
The limitations of this study include the relatively small number of patients, only intraoperative O-arm 3D real-time anatomical navigation without postoperative CT imaging to compare in every case.
| Conclusions|| |
O-arm 3D navigation achieves relatively high accuracy of pedicle and lateral mass screws implantation. The accumulation of experience for O-arm 3D CT during initial learning curve is still warranted to promote the accuracy of screws position and shorten operation time.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]