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

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          Abstract

          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.

          Methods

          Minimally invasive pedicle screw placement in T8 to S1 pedicles of eight fresh-frozen human cadaveric torsos was guided with EMF or standard fluoroscopy. Set-up, insertion, and fluoroscopic times and radiation exposure and accuracy (measured with post-procedural computed tomography) were analyzed in each group.

          Results

          Sixty-two pedicle screws were placed under fluoroscopic guidance and 60 under EMF guidance. Ideal trajectories were achieved more frequently with EMF over all segments (62.7% vs. 40%; p = 0.01). Greatest EMF accuracy was achieved in the lumbar spine, with significant improvements in both ideal trajectory and reduction of pedicle breaches over fluoroscopically guided placement (64.9% vs. 40%, p = 0.03, and 16.2% vs. 42.5%, p = 0.01, respectively). Fluoroscopy time was reduced 77% with the use of EMF (22 s vs. 5 s per level; p < 0.0001) over all spinal segments. Radiation exposure at the hand and body was reduced 60% ( p = 0.058) and 32% ( p = 0.073), respectively. Time for insertion did not vary between the two techniques.

          Conclusions

          Minimally invasive pedicle screw placement with the aid of EMF image guidance reduces fluoroscopy time and increases placement accuracy when compared with traditional fluoroscopic guidance while adding no additional time to the procedure.

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          Most cited references32

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          Pedicle screw placement accuracy: a meta-analysis.

          A meta-analysis of the published literature was conducted specifically looking at accuracy and the postoperative methods used for the assessment of pedicle screw placement in the human spine. This study specifically aimed to identify postoperative methods used for pedicle screw placement assessment, including the most common method, and to report cumulative pedicle screw placement study statistics from synthesis of the published literature. Safety concerns have driven specific interests in the accuracy and precision of pedicle screw placement. A large variation in reported accuracy may exist partly due to the lack of a standardized evaluation method and/or the lack of consensus to what, or in which range, is pedicle screw placement accuracy considered satisfactory. A MEDLINE search was executed covering the span from 1966 until 2006, and references from identified papers were reviewed. An extensive database was constructed for synthesis of the identified studies. Subgroups and descriptive statistics were determined based on the type of population, in vivo or cadaveric, and separated based on whether the assistance of navigation was employed. In total, we report on 130 studies resulting in 37,337 total pedicle screws implanted, of which 34,107 (91.3%) were identified as accurately placed for the combined in vivo and cadaveric populations. The most common assessment method identified pedicle screw violations simply as either present or absent. Overall, the median placement accuracy for the in vivo assisted navigation subgroup (95.2%) was higher than that of the subgroup without the use of navigation (90.3%). Navigation does indeed provide a higher accuracy in the placement of pedicle screws for most of the subgroups presented. However, an exception is found at the thoracic levels for both the in vivo and cadaveric populations, where no advantage in the use of navigation was found.
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            Radiation exposure to the spine surgeon during fluoroscopically assisted pedicle screw insertion.

            In vitro study to determine occupational radiation exposure during lumbar fluoroscopy. To assess radiation exposure to the spine surgeon during fluoroscopically assisted thoracolumbar pedicle screw placement. Occupational radiation exposure during a variety of fluoroscopically assisted musculoskeletal procedures has been previously evaluated. No prior study has assessed fluoroscopy-related radiation exposure to the spine surgeon. Bilateral pedicle screw placement (T11-S1) was performed in six cadavers using lateral fluoroscopic imaging. Radiation dose rates to the surgeon's neck, torso, and dominant hand were measured with dosimeter badges and thermolucent dosimeter (TLD) rings. Radiation levels were also quantified at various distances from the dorsal lumbar surface using an ion chamber radiation survey meter. The mean dose rate to the neck was 8.3 mrem/min. The dose rate to the torso was greatest when the surgeon was positioned ipsilateral to the beam source (53.3 mrem/min, compared with 2.2 mrem/min on the contralateral side). The average hand dose rate was 58.2 mrem/min. A significant increase in hand dose rate was associated with placement of screws ipsilateral to the beam source (P = 0.0005) and larger specimens (P = 0.0007). Radiation levels significantly decreased as distance from the beam source and dorsal body surface increased. The greatest levels of radiation were noted on the side where the primary radiograph beam entered the cadaver. Fluoroscopically assisted thoracolumbar pedicle screw placement exposes the spine surgeon to significantly greater radiation levels than other, nonspinal musculoskeletal procedures that involve the use of a fluoroscope. In fact, dose rates are up to 10-12 times greater. Spine surgeons performing fluoroscopically assisted thoracolumbar procedures should monitor their annual radiation exposure. Measures to reduce radiation exposure and surgeon awareness of high-exposure body and hand positions are certainly called for.
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              Minimally invasive lumbar fusion.

              Review article. To provide an overview of current techniques for minimally invasive lumbar fusion. Minimally invasive techniques have revolutionized the management of pathologic conditions in various surgical disciplines. Although these same principles have been used in the treatment of lumbar disc disease for many years, minimally invasive lumbar fusion procedures have only recently been developed. The goals of these procedures are to reduce the approach-related morbidity associated with traditional lumbar fusion, yet allow the surgery to be performed in an effective and safe manner. The authors' clinical experience with minimally invasive lumbar fusion was reviewed, and the pertinent literature was surveyed. Minimally invasive approaches have been developed for common lumbar procedures such as anterior and posterior interbody fusion, posterolateral onlay fusion, and internal fixation. As with all new surgical techniques, minimally invasive lumbar fusion has a learning curve. As well, there are benefits and disadvantages associated with each technique. However, because these techniques are new and evolving, evidence to support their potential benefits is largely anecdotal. Additionally, there are few long-term studies to document clinical outcomes. Preliminary clinical results suggest that minimally invasive lumbar fusion will have a beneficial impact on the care of patients with spinal disorders. Outcome studies with long-term follow-up will be necessary to validate its success and allow minimally invasive lumbar fusion to become more widely accepted.
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                Author and article information

                Contributors
                +1-617-6693200 , +1-781-9790108 , drvonjako@comcast.net
                Journal
                Acta Neurochir (Wien)
                Acta Neurochirurgica
                Springer Vienna (Vienna )
                0001-6268
                0942-0940
                14 December 2010
                14 December 2010
                March 2011
                : 153
                : 3
                : 589-596
                Affiliations
                [1 ]GE Healthcare, Boston, MA USA
                [2 ]Department of Neurosurgery, University of Utah, Salt Lake City, UT USA
                [3 ]Texas Back Institute, Scottsdale, AZ USA
                [4 ]University of California, Los Angeles, CA USA
                [5 ]Department of Radiology, Johns Hopkins University, Baltimore, MD USA
                [6 ]Department of Neurosurgery, William Beaumont Hospital, Royal Oak, MI USA
                [7 ]GE Healthcare, 301 Ballardvale St, Wilmington, MA 01887 USA
                Article
                882
                10.1007/s00701-010-0882-4
                3040822
                21153669
                dc51168f-0d8a-462a-be5f-7f53630bcd90
                © The Author(s) 2010
                History
                : 21 July 2010
                : 12 November 2010
                Categories
                Experimental Research
                Custom metadata
                © Springer-Verlag 2011

                Surgery
                pedicle screw,electromagnetic field navigation,fluoroscopy,minimally invasive,accuracy
                Surgery
                pedicle screw, electromagnetic field navigation, fluoroscopy, minimally invasive, accuracy

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