Considering Pedicle Screw Resistance in Electromyography of the Spine

2020 ◽  
Vol 20 (1) ◽  
pp. 69-73
Author(s):  
Jonathan Norton ◽  
Michael Kindrachuk ◽  
Daryl R Fourney
Keyword(s):  
Pedicle Screw ◽  
Image Guidance ◽  
Pedicle Screws ◽  
Electrical Stimulus ◽  
Nerve Roots ◽  
Screw Head ◽  
Integrity Testing ◽  
Testing Resistance ◽  
Ieee Standards ◽  
Muscle Potential

Abstract BACKGROUND Evoked electromyographic (EMG) monitoring of pedicle screws has been shown to be an effective adjuvant to image guidance or direct visualization of pedicle screw placement. Electrical stimulation is delivered to the head of the screw at various intensities until a muscle potential is evoked. This practice is based on the fact that an intact pedicle effectively shields nerve roots from electrical stimulus. Several factors have been debated that may affect the interpretation of results; however, to the best of our knowledge, the electrical resistance of modern manufactured pedicle screws and stimulation devices has not been studied. OBJECTIVE To determine if pedicle screw resistances affect triggered EMG. METHODS Samples of the most commonly implanted pedicle screws in Canada were obtained, with diameters ranging from 4.5 to 7 mm. The resistance between the screw head and thread and core at the midpoint and tip of the screw was recorded using a Multimeter in accordance with IEEE standards. For screws with variable threads, the midpoint was considered the point at which the thread pitch changed. RESULTS All screws had low impedances when tested at the point of the screw, but much higher when the cup is tested. The resistance of different manufactures' screws was significantly different, ranging from 0.514 to 2156 Ohms. CONCLUSION Despite differences in resistance, most screws had resistances in ranges that allow for triggered EMG pedicle integrity testing. Resistance from pedicle screws is an important consideration in EMG monitoring of the spine.

The accuracy of pedicle screw placement using intraoperative image guidance systems

2014 ◽  
Vol 20 (2) ◽  
pp. 196-203 ◽  
Author(s):  
Alexander Mason ◽  
Renee Paulsen ◽  
Jason M. Babuska ◽  
Sharad Rajpal ◽  
Sigita Burneikiene ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Image Guidance ◽  
Pedicle Screws ◽  
Screw Placement ◽  
Data Sets ◽  
Pedicle Screw Placement ◽  
Fluoroscopic Image ◽  
Fluoroscopic Navigation ◽  
Guidance Systems ◽  
Accuracy Rates

Object Several retrospective studies have demonstrated higher accuracy rates and increased safety for navigated pedicle screw placement than for free-hand techniques; however, the accuracy differences between navigation systems has not been extensively studied. In some instances, 3D fluoroscopic navigation methods have been reported to not be more accurate than 2D navigation methods for pedicle screw placement. The authors of this study endeavored to identify if 3D fluoroscopic navigation methods resulted in a higher placement accuracy of pedicle screws. Methods A systematic analysis was conducted to examine pedicle screw insertion accuracy based on the use of 2D, 3D, and conventional fluoroscopic image guidance systems. A PubMed and MEDLINE database search was conducted to review the published literature that focused on the accuracy of pedicle screw placement using intraoperative, real-time fluoroscopic image guidance in spine fusion surgeries. The pedicle screw accuracy rates were segregated according to spinal level because each spinal region has individual anatomical and morphological variations. Descriptive statistics were used to compare the pedicle screw insertion accuracy rate differences among the navigation methods. Results A total of 30 studies were included in the analysis. The data were abstracted and analyzed for the following groups: 12 data sets that used conventional fluoroscopy, 8 data sets that used 2D fluoroscopic navigation, and 20 data sets that used 3D fluoroscopic navigation. These studies included 1973 patients in whom 9310 pedicle screws were inserted. With conventional fluoroscopy, 2532 of 3719 screws were inserted accurately (68.1% accuracy); with 2D fluoroscopic navigation, 1031 of 1223 screws were inserted accurately (84.3% accuracy); and with 3D fluoroscopic navigation, 4170 of 4368 screws were inserted accurately (95.5% accuracy). The accuracy rates when 3D was compared with 2D fluoroscopic navigation were also consistently higher throughout all individual spinal levels. Conclusions Three-dimensional fluoroscopic image guidance systems demonstrated a significantly higher pedicle screw placement accuracy than conventional fluoroscopy or 2D fluoroscopic image guidance methods.

Placement of thoracic transvertebral pedicle screws using 3D image guidance

2013 ◽  
Vol 18 (5) ◽  
pp. 479-483 ◽  
Author(s):  
Eric W. Nottmeier ◽  
Stephen M. Pirris
Keyword(s):  
Pedicle Screw ◽  
Image Guidance ◽  
Pedicle Screws ◽  
Guidance System ◽  
Ct Scans ◽  
Screw Placement ◽  
Clinical Consequence ◽  
3D Image ◽  
Cortical Layers ◽  
Disc Space

Object Transvertebral pedicle screws have successfully been used in the treatment of high-grade L5–S1 spondylolisthesis. An advantage of transvertebral pedicle screws is the purchase of multiple cortical layers across 2 vertebrae, thereby increasing the stability of the construct. At the lumbosacral junction, transvertebral pedicle screws have been shown to be biomechanically superior to pedicle screws placed in the standard fashion. The use of transvertebral pedicle screws at spinal levels other than L5–S1 has not been reported in the literature. The authors describe their technique of transvertebral pedicle screw placement in the thoracic spine using 3D image guidance. Methods Twelve patients undergoing cervicothoracic or thoracolumbar fusion had 41 thoracic transvertebral pedicle screws placed across 26 spinal levels using this technique. Indications for placement of thoracic transvertebral pedicle screws in earlier cases included osteoporosis and pedicle screw salvage. However, in subsequent cases screws were placed in patients undergoing multilevel thoracolumbar fusion without osteoporosis, particularly near the top of the construct. Image guidance in this study was accomplished using the Medtronic StealthStation S7 image guidance system used in conjunction with the O-arm. All patients were slated to undergo postoperative CT scanning at approximately 4–6 months for fusion assessment, which also allowed for grading of the transvertebral pedicle screws. Results No thoracic transvertebral pedicle screw placed in this study had to be replaced or repositioned after intraoperative review of the cone beam CT scans. Review of the postoperative CT scans revealed all transvertebral screws to be across the superior disc space with the tips in the superior vertebral body. Six pedicle screws were placed using the in-out-in technique in patients with narrow pedicles, leaving 35 screws that underwent breach analysis. No pedicle breach was noted in 34 of 35 screws. A Grade 1 (< 2 mm) medial breach was noted in 1 screw without clinical consequence. Solid fusion was observed across 25 of 26 spinal levels that underwent transvertebral screw placement including 7 spinal levels located at the top of a multilevel construct. Conclusions This report describes the authors' initial in vivo experience with the 3D image-guided placement of 41 thoracic transvertebral pedicle screws. Advantages of thoracic transvertebral screws include the purchase of 2 vertebral segments across multiple cortical layers. A high fusion rate was observed across spinal levels in which transvertebral screws were placed. A formal biomechanical study is needed to assess the biomechanical advantages of this technique and is currently being planned.

A comparison of two techniques in image-guided thoracic pedicle screw placement: a retrospective study of 37 patients and 277 pedicle screws

2007 ◽  
Vol 7 (4) ◽  
pp. 393-398 ◽  
Author(s):  
Gregory P. Lekovic ◽  
Eric A. Potts ◽  
Dean G. Karahalios ◽  
Graham Hall
Keyword(s):  
Pedicle Screw ◽  
Image Guidance ◽  
Vascular Complications ◽  
Pedicle Screws ◽  
Guidance System ◽  
Screw Placement ◽  
Pedicle Screw Placement ◽  
3D Navigation ◽  
Thoracic Pedicle Screw ◽  
Computed Tomography Scanning

Object The goal of this study was to compare the accuracy of thoracic pedicle screw placement aided by two different image-guidance modalities. Methods The charts of 40 consecutive patients who had undergone stabilization of the thoracic spine between January 2003 and January 2005 were retrospectively reviewed. Three patients were excluded from the study because, on the basis of preoperative findings, small pedicle diameter precluded the use of pedicle screws. Thus, a total of 37 patients had 277 screws placed with the aid of either virtual fluoroscopy or isocentric C-arm 3D navigation. The indications for surgery included trauma, degenerative disease, and tumor, and were similar in both groups. All 37 patients underwent postoperative computed tomography scanning, and an independent reviewer graded all screws based on axial, sagittal, and coronal projections for a full determination of the placement of the screw in the pedicle. Results The rate of unintended perforations was found to depend on pedicle diameter (p < 0.0001). There were no statistical differences between groups with regard to rate or grade of cortical perforations. Overall, the rate and grade of perforations was low, and there were no neurological or vascular complications. Conclusions The authors have shown that either image-guidance system may be used with a high degree of accuracy and safety. Because both systems were found to be comparably safe and accurate, the choice of image-guidance modality may be determined by the level of surgeon comfort and/or availability of the system.

scholarly journals Cost-Effectiveness of Image-Guided Spine Surgery

2010 ◽  
Vol 4 (1) ◽  
pp. 228-233 ◽  
Author(s):  
Robert Green Watkins ◽  
Akash Gupta ◽  
Robert Green Watkins
Keyword(s):  
Pedicle Screw ◽  
Spine Surgery ◽  
Image Guidance ◽  
Pedicle Screws ◽  
Cost Savings ◽  
Cost Effective ◽  
Guidance System ◽  
Screw Placement ◽  
Image Guided ◽  
Time Required

Objective: To determine if image-guided spine surgery is cost effective. Methods: A prospective case series of the first 100 patients undergoing thoracolumbar pedicle screw instrumentation under image-guidance was compared to a retrospective control group of the last 100 patients who underwent screw placement prior to the use of image-guidance. The image-guidance system was NaviVision (Vector Vision-BrainLAB) and Arcadis Orbic (Siemens). Results: The rate of revision surgery was reduced from 3% to 0% with the use of image guidance (p=0.08). The cost savings of image guidance for the placement of pedicle screws was $71,286 per 100 cases. Time required for pedicle screw placement with image guidance was 20 minutes for 2 screws, 29 minutes for 4 screws, 38 minutes for 6 screws, and 50 min for 8 screws. Cost savings for the time required for placement of pedicle screws with image guidance can be estimated by subtracting the time required with currently used techniques without image guidance from the above averages, then multiplying by $93 per minute. The approximate costs of the navigation system is $475,000 ( $225,000 for Vector Vision-BrainLAB and $250,000 for Arcadis Orbic-Siemens). Conclusion: Image guidance for the placement of pedicle screws may be cost effective in spine practices with heavy volume, that perform surgery in difficult cases, and that require long surgical times for the placement of pedicle screws.

scholarly journals Evaluation of the Effect of Fixation Angle between Polyaxial Pedicle Screw Head and Rod on the Failure of Screw-Rod Connection

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Engin Çetin ◽  
Mustafa Özkaya ◽  
Ümit Özgür Güler ◽  
Emre Acaroğlu ◽  
Teyfik Demir
Keyword(s):  
Mechanical Properties ◽  
Pedicle Screw ◽  
Pedicle Screws ◽  
Maximum Load ◽  
Test Results ◽  
Screw Head ◽  
Pull Out ◽  
Flexion Moment ◽  
Polyaxial Screws ◽  
Different Diameters

Introduction.Polyaxial screws had been only tested according to the ASTM standards (when they were perpendicularly positioned to the rod). In this study, effects of the pedicle screws angled fixation to the rod on the mechanical properties of fixation were investigated.Materials and Method.30 vertically fixed screws and 30 screws fixed with angle were used in the study. Screws were used in three different diameters which were 6.5 mm, 7.0 mm, and 7.5 mm, in equal numbers. Axial pull-out and flexion moment tests were performed. Test results compared with each other using appropriate statistical methods.Results.In pull-out test, vertically fixed screws, in 6.5 mm and 7.0 mm diameter, had significantly higher maximum load values than angled fixed screws with the same diameters (P<0.01). Additionally, vertically fixed screws, in all diameters, had significantly greater stiffness according to corresponding size fixed with angle (P<0.005).Conclusion.Fixing the pedicle screw to the rod with angle significantly decreased the pull-out stiffness in all diameters. Similarly, pedicle screw instrumentation fixed with angle decreased the minimum sagittal angle between the rod and the screw in all diameters for flexion moment test but the differences were not significant.

Early experience of placing image-guided minimally invasive pedicle screws without K-wires or bone-anchored trackers

2018 ◽  
Vol 28 (4) ◽  
pp. 357-363 ◽  
Author(s):  
Gregory M. Malham ◽  
Rhiannon M. Parker
Keyword(s):  
Pedicle Screw ◽  
Image Guidance ◽  
Pedicle Screws ◽  
Early Experience ◽  
Intraoperative Neuromonitoring ◽  
Screw Placement ◽  
Pedicle Screw Placement ◽  
Image Guided ◽  
K Wires ◽  
Percutaneous Screws

OBJECTIVEImage guidance for spine surgery has been reported to improve the accuracy of pedicle screw placement and reduce revision rates and radiation exposure. Current navigation and robot-assisted techniques for percutaneous screws rely on bone-anchored trackers and Kirchner wires (K-wires). There is a paucity of published data regarding the placement of image-guided percutaneous screws without K-wires. A new skin-adhesive stereotactic patient tracker (SpineMask) eliminates both an invasive bone-anchored tracker and K-wires for pedicle screw placement. This study reports the authors’ early experience with the use of SpineMask for “K-wireless” placement of minimally invasive pedicle screws and makes recommendations for its potential applications in lumbar fusion.METHODSForty-five consecutive patients (involving 204 screws inserted) underwent K-wireless lumbar pedicle screw fixation with SpineMask and intraoperative neuromonitoring. Screws were inserted by percutaneous stab or Wiltse incisions. If required, decompression with or without interbody fusion was performed using mini-open midline incisions. Multimodality intraoperative neuromonitoring assessing motor and sensory responses with triggered electromyography (tEMG) was performed. Computed tomography scans were obtained 2 days postoperatively to assess screw placement and any cortical breaches. A breach was defined as any violation of a pedicle screw involving the cortical bone of the pedicle.RESULTSFourteen screws (7%) required intraoperative revision. Screws were removed and repositioned due to a tEMG response < 13 mA, tactile feedback, and 3D fluoroscopic assessment. All screws were revised using the SpineMask with the same screw placement technique. The highest proportion of revisions occurred with Wiltse incisions (4/12, 33%) as this caused the greatest degree of SpineMask deformation, followed by a mini midline incision (3/26, 12%). Percutaneous screws via a single stab incision resulted in the fewest revisions (7/166, 4%). Postoperative CT demonstrated 7 pedicle screw breaches (3%; 5 lateral, 1 medial, 1 superior), all with percutaneous stab incisions (7/166, 4%). The radiological accuracy of the SpineMask tracker was 97% (197/204 screws). No patients suffered neural injury or required postoperative screw revision.CONCLUSIONSThe noninvasive cutaneous SpineMask tracker with 3D image guidance and tEMG monitoring provided high accuracy (97%) for percutaneous pedicle screw placement via stab incisions without K-wires.

scholarly journals Intraoperative image-guided spinal navigation: technical pitfalls and their avoidance

2014 ◽  
Vol 36 (3) ◽  
pp. E3 ◽  
Author(s):  
Gazanfar Rahmathulla ◽  
Eric W. Nottmeier ◽  
Stephen M. Pirris ◽  
H. Gordon Deen ◽  
Mark A. Pichelmann
Keyword(s):  
Pedicle Screw ◽  
3D Imaging ◽  
Image Guidance ◽  
Spinal Instrumentation ◽  
Pedicle Screws ◽  
Navigation Systems ◽  
Spinal Fixation ◽  
Pedicle Screw Placement ◽  
Screw Insertion ◽  
Spinal Navigation

Spinal instrumentation has made significant advances in the last two decades, with transpedicular constructs now widely used in spinal fixation. Pedicle screw constructs are routinely used in thoracolumbar-instrumented fusions, and in recent years, the cervical spine as well. Three-column fixations with pedicle screws provide the most rigid form of posterior stabilization. Surgical landmarks and fluoroscopy have been used routinely for pedicle screw insertion, but a number of studies reveal inaccuracies in placement using these conventional techniques (ranging from 10% to 50%). The ability to combine 3D imaging with intraoperative navigation systems has improved the accuracy and safety of pedicle screw placement, especially in more complex spinal deformities. However, in the authors' experience with image guidance in more than 1500 cases, several potential pitfalls have been identified while using intraoperative spinal navigation that could lead to suboptimal results. This article summarizes the authors' experience with these various pitfalls using spinal navigation, and gives practical tips on their avoidance and management.

Evaluation of registration techniques for spinal image guidance

2006 ◽  
Vol 4 (4) ◽  
pp. 323-328 ◽  
Author(s):  
Langston T. Holly ◽  
Orin Bloch ◽  
J. Patrick Johnson
Keyword(s):  
Image Guidance ◽  
Operating Time ◽  
Pedicle Screws ◽  
Reference Points ◽  
Surface Matching ◽  
Screw Head ◽  
Point Matching ◽  
Registration Error ◽  
The Mean ◽  
Spinal Image

Object Paired point matching alone and paired point matching combined with surface matching are the two techniques used for the registration step in preoperative computerized tomography–based spinal image guidance. In the present study the authors sought to compare paired point–matching registration alone with paired point matching supplemented with surface matching to determine if the addition of surface matching improves navigational accuracy. Methods Pedicle screws were placed in three embalmed human cervicothoracic spinal specimens during image guidance to serve as a reference points. The specimens were then rescanned, and each level was registered using paired point matching alone and then by paired point supplemented with surface matching. Navigational accuracy was assessed by placing the stereotactic probe in the center of the screw head, and measuring the apparent distance between the screw head and probe on the computer monitor. Statistical analysis was used to compare the registration error and navigational error between the two techniques. Seventy-five screws were placed at 46 vertebral levels. The mean registration error for the paired point matching/surface matching technique (0.5 mm) was significantly lower (p < 0.001) than that of the paired point matching alone technique (1.2 mm); however, the intertechnique difference in navigational error was nearly equivalent (1.3 mm compared with 1.4 mm) and statistically insignificant (p > 0.05). Conclusions Although the addition of surface matching to paired point registration significantly decreased the mean registration error, the actual navigational accuracy between the two techniques was equivalent when easily distinguishable points were meticulously selected. The use of paired point matching alone did not compromise the accuracy of navigation and is likely to result in decreased operating time.

scholarly journals Image-guid ed thoracic pedicle screw placement: a technical study in cadavers and preliminary clinical experience

2001 ◽  
Vol 10 (2) ◽  
pp. 1-5 ◽  
Author(s):  
Kee D. Kim ◽  
J. Patrick Johnson ◽  
Jesse D. Babbitz
Keyword(s):  
Pedicle Screw ◽  
Image Guidance ◽  
Pedicle Screws ◽  
Guidance System ◽  
Basic Knowledge ◽  
Screw Placement ◽  
Pedicle Screw Placement ◽  
Image Guided ◽  
Thoracic Pedicle Screw ◽  
Thoracic Pedicle Screws

Object Thoracic pedicle screw fixation is effective and reliable in providing short-segment stabilization. Although the procedure is becoming more widely used, accurate insertion of the screws is difficult due to the small dimensions of thoracic pedicles, and the associated risk is high due to the proximity of the spinal cord. In previous studies authors have shown the accuracy of image-guided lumbar pedicle screw placement, but there have been no reported investigations into the accuracy of image-guided thoracic pedicle screw placement. The authors report their experience with such an investigation. Methods To evaluate the accuracy of image-guided thoracic pedicle screw placement in vitro and in vivo, thoracic pedicle screws were placed with an image-guidance system in five human cadavers and 10 patients. In cadavers, the accuracy of screw placement was assessed by postoperative computerized tomography and visual inspection and in patients by postoperative imaging studies. Of the 120 pedicle screws placed in five cadavers pedicle violation occurred in 23 cases (19.2%); there was one pedicle violation (4.2%) in each of the last two cadavers. Of the 45 pedicle screws placed in 10 patients, pedicle violations occurred in three (6.7%). Conclusions In comparison with historical controls, the accuracy of thoracic pedicle screw placement is improved with the use of an image-guidance system. It allows the surgeon to visualize the thoracic pedicle and the surrounding structures that are normally out of the surgical field of view. The surgeon, however, must be aware of the limitations of an image-guidance system and have a sound basic knowledge of spinal anatomy to avoid causing serious complications.

Image-Guided Spinal Surgery and Robotics in MIS: Where Are We Now?

2018 ◽  
Vol 1 (2) ◽  
pp. 2
Author(s):  
Chiung Chyi Shen
Keyword(s):  
Pedicle Screw ◽  
Spinal Surgery ◽  
Surgical Navigation ◽  
Improve Patient Safety ◽  
Intraoperative Imaging ◽  
Spinal Instrumentation ◽  
Pedicle Screws ◽  
Computer Assisted ◽  
Navigation Systems ◽  
Image Guided

Use of pedicle screws is widespread in spinal surgery for degenerative, traumatic, and oncological diseases. The conventional technique is based on the recognition of anatomic landmarks, preparation and palpation of cortices of the pedicle under control of an intraoperative C-arm (iC-arm) fluoroscopy. With these conventional methods, the median pedicle screw accuracy ranges from 86.7% to 93.8%, even if perforation rates range from 21.1% to 39.8%.The development of novel intraoperative navigational techniques, commonly referred to as image-guided surgery (IGS), provide simultaneous and multiplanar views of spinal anatomy. IGS technology can increase the accuracy of spinal instrumentation procedures and improve patient safety. These systems, such as fluoroscopy-based image guidance ("virtual fluoroscopy") and computed tomography (CT)-based computer-guidance systems, have sensibly minimized risk of pedicle screw misplacement, with overall perforation rates ranging from between 14.3% and 9.3%, respectively."Virtual fluoroscopy" allows simultaneous two-dimensional (2D) guidance in multiple planes, but does not provide any axial images; quality of images is directly dependent on the resolution of the acquired fluoroscopic projections. Furthermore, computer-assisted surgical navigation systems decrease the reliance on intraoperative imaging, thus reducing the use of intraprocedure ionizing radiation. The major limitation of this technique is related to the variation of the position of the patient from the preoperative CT scan, usually obtained before surgery in a supine position, and the operative position (prone). The next technological evolution is the use of an intraoperative CT (iCT) scan, which would allow us to solve the position-dependent changes, granting a higher accuracy in the navigation system. 

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