PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (972475)

Clipboard (0)
None

Related Articles

1.  Clinical results of XMR-assisted percutaneous transforaminal endoscopic lumbar discectomy 
Background
Although percutaneous endoscopic lumbar discectomy (PELD) has shown favorable outcomes in the majority of lumbar discectomy cases, there were also some failures. The most common cause of failure is the incomplete removal of disc fragments. The skin entry point for the guide-needle trajectory and the optimal placement of the working sleeve are largely blind, which might lead to the inadequate removal of disc fragments. The objective of this study was to present our early experiences with image-guided PELD using a specially designed fluoroscope with magnetic resonance imaging-equipped operative suite (XMR) for the treatment of lumbar disc herniation.
Methods
This prospective study included 89 patients who had undergone PELD via the transforaminal approach using an XMR protocol. Pre- and postoperative examinations (at 12 weeks) included a detailed clinical history, visual analogue scale (VAS), Oswestry disability index (ODI), and radiological workups. The results were categorized as excellent, good, fair, and poor according to MacNab's criteria. At the final follow-up, the minimum follow-up time for the subjects was 2 years. The need for revision surgeries and postoperative complications were noted on follow-up.
Results
Postoperative mean ODI decreased from 67.4% to 5.61%. Mean VAS score for back and leg pain improved significantly from 4 to 2.3 and from 7.99 to 1.04, respectively. Four (4.49%) patients underwent a second-stage PELD after intraoperative XMR had shown remnant fragments after the first stage. As per MacNab's criteria, 76 patients (85.4%) showed excellent, 8 (8.89%) good, 3 (3.37%) fair, and 2 (2.25) poor results. Four (4.49%) patients had remnant disc fragments on XMR, which were removed during the same procedure. All of these patients had either highly migrated or sequestrated disc fragments preoperatively. Four (4.49%) other patients needed a second, open surgery due to symptomatic postoperative hematoma (n = 2) and recurrent disc herniation (n = 2).
Conclusions
This prospective analysis indicates that XMR-assisted PELD provides a precise skin entry point. It also confirms that decompression occurs intraoperatively, which negates the need for a separate surgery and thus increases the success rate of PELD, particularly in highly migrated or sequestrated discs. However, further extensive experience is required to confirm the advantages and feasibility of PELD in terms of cost effectiveness.
doi:10.1186/1749-799X-8-14
PMCID: PMC3668223  PMID: 23705685
Percutaneous endoscopic lumbar discectomy; Incomplete disc removal; XMR-guided procedure; High success rate
2.  Comparison of two novel fluoroscopy-based stereotactic methods for cervical pedicle screw placement and review of the literature 
European Spine Journal  2008;17(4):564-575.
This experimental study was designed to compare two different fluoroscopy-based stereotactic surgical techniques for transcutaneous cervical pedicle screw (CPS) placement in the subaxial human cervical spine: (1) a custom-made aiming frame (AF) in combination with conventional fluoroscopy versus (2) a targeting device in combination with a computer-assisted image guidance system [i.e. virtual fluoroscopy (VF)]. Surgery was carried out on six preserved human total body specimens in a laboratory setting. Sixty pedicles (levels C3–C7) were measured in a multislice computed tomography (CT) image data set prior to surgery. Two groups consisting of three specimens and 30 pedicles each were defined according to the surgical technique. The AF consisted of radiolucent components with a fully adjustable arm for carrying the instruments necessary for placing the screws. The arm was angled according to the cervical pedicle axis, as determined by the preoperative CT scans and intraoperative lateral fluoroscopy. For VF, a targeting device was combined with a computer-assisted image-guided surgery unit. For both stereotactic techniques, 3.5 mm screws made of carbon fibre polyetheretherketone (ECF-PEEK) were inserted transcutaneously through stab incisions. Screw placement was assessed using a four-point grading system ranging from ideal (I) to unacceptable (III) where I = screw centred in pedicle, IIa = perforation of pedicle wall is less than one-fourth of the screw diameter, IIb = perforation of the pedicle wall is more than one-fourth of the screw diameter without contact to neurovascular structures, and III = CPS in contact with neurovascular structures. Fifty-eight pedicle screws could be evaluated without interfering metal artefacts according to the same CT protocol that was used preoperatively. The AF technique achieved a significantly smaller number of screws in contact with neurovascular structures compared with the VF technique (P = 0.021; Fisher’s exact test) (Grade I n = 15; 64.3% AF vs. n = 13; 43.3% VF and Grade III n = 2; 7.1% AF vs. n = 10; 33.3% VF). Although neither of the two techniques was capable of completely preventing CPS perforations, transcutaneous CPS placement with a conventional fluoroscopy-based stereotactic AF can be considered a less expensive alternative to VF. This AF technique is able to reduce the number and severity of lateral pedicle wall violations compared to screw placement via the wide standard posterior open midline approach to the subaxial cervical spine. The results of this study are discussed in context with those obtained from different published modifications, since the first technical description of this surgical technique in 1994 by Abumi and co-workers.
doi:10.1007/s00586-008-0584-2
PMCID: PMC2295280  PMID: 18210169
Cervical spine; Morphometry; Cervical pedicle screws; Frame-based stereotaxis; Computer-assisted fluoroscopic navigation
3.  Percutaneous endoscopic lumbar discectomy for migrated disc herniation: classification of disc migration and surgical approaches 
European Spine Journal  2006;16(3):431-437.
Percutaneous endoscopic lumbar discectomy (PELD) for migrated disc herniations is technically demanding due to the absence of the technical guideline. The purposes of this study were to propose a radiologic classification of disc migration and surgical approaches of PELD according to the classification. A prospective study of 116 consecutive patients undergoing single-level PELD was conducted. According to preoperative MRI findings, disc migration was classified into four zones based on the direction and distance from the disc space: zone 1 (far up), zone 2 (near up), zone 3 (near down), zone 4 (far down). Two surgical approaches were used according to this classification. Near-migrated discs were treated with “half-and-half” technique, which involved positioning a beveled working sheath across the disc space to the epidural space. Far-migrated discs were treated with “epiduroscopic” technique, which involved introducing the endoscope into the epidural space completely. The mean follow-up period was 14.5 (range 9–20) months. According to the Macnab criteria, satisfactory results were as follows: 91.6% (98/107) in the down-migrated discs; 88.9% (8/9) in the up-migrated discs; 97.4% (76/78) in the near-migrated discs; and 78.9% (30/38) in the far-migrated discs. The mean VAS score decreased from 7.5 ± 1.7 preoperatively to 2.6 ± 1.8 at the final follow-up (P < 0.0001). There were no recurrence and no approach-related complications during the follow-up period. The proposed classification and approaches will provide appropriate surgical guideline of PELD for migrated disc herniation. Based on our results, open surgery should be considered for far-migrated disc herniations.
doi:10.1007/s00586-006-0219-4
PMCID: PMC2200706  PMID: 16972067
Percutaneous endoscopic lumbar discectomy; Migrated disc herniation; Radiologic classification
4.  Clinical and radiological association with positive lumbar discography in patients with chronic low back pain 
Study design: Retrospective cohort study.
Objectives: To find out (1) if magnetic resonance imaging (MRI) findings associated with positive discography in patients with lumbar discogenic pain are caused by degenerative disc disease (DDD). (2) If clinical risk factors associated with positive discography in patients with lumbar discogenic pain are caused by DDD.
Methods: Thirty-three discographies were performed in 20 consecutive patients with chronic low back pain (LBP). All examinations were performed in the lumbar spine between L3 and S1. Patient assessment consisted of a clinical and radiological examination through a protocol that contained data on the history, visual analogue scale for pain (VAS), functional questionnaire (Oswestry), and MRI findings. Discography was considered positive using the Walsh's criteria. We examined the association between MRI and clinical findings with positive discography using logistic regression.
Results: Fourteen discographies (42%) were positive and 19 (58%) were negative. The mean age of patients with positive discography was 40.7 years (range, 25–56 years) and negative discography 43.1 years (range, 30–55 years). Men had a positive discography rate of 43.5% and women 40%. Patients with LBP had reduced odds of a positive discography compared with those with LBP and sciatica (OR = .5; 95% CI: 0.1–2.7); however, this association was not statistically significant. Patients with more than four previous episodes of pain versus patients with one to four episodes had greater odds of a positive discography (OR = 3.8; 95% CI: 0.07–184); but this association was not statistically significant. Patients with various pathologies on MRI had greater odds of a positive discography; however, these associations were not statistically significant either.
Conclusions: Patients with a chief complaint of LBP associated with sciatica, with more than four episodes of previous LBP exacerbations and the presence of a high intensity zone (HIZ) on MRI have a higher rate of positive discography. These findings are not statistically significant, probably due to a small sample size. During discography, we found the end point resistance to be more prevalent in asymptomatic discs.
doi:10.1055/s-0031-1298598
PMCID: PMC3503511  PMID: 23236303
5.  Radiation dose reduction in CT-guided sacroiliac joint injections to levels of pulsed fluoroscopy: a comparative study with technical considerations 
Journal of Pain Research  2012;5:265-269.
Background
The sacroiliac (SI) joint is frequently the primary source of low back pain. Over the past decades, a number of different SI injection techniques have been used in its diagnosis and therapy. Despite the concerns regarding exposure to radiation, image-guided injection techniques are the preferred method to achieve safe and precise intra-articular needle placement. The following study presents a comparison of radiation doses, calculated for fluoroscopy and CT-guided SI joint injections in standard and low-dose protocol and presents the technical possibility of CT-guidance with maximum radiation dose reduction to levels of fluoroscopic-guidance for a precise intra-articular injection technique.
Objective
To evaluate the possibility of dose reduction in CT-guided sacroiliac joint injections to pulsed-fluoroscopy-guidance levels and to compare the doses of pulsed-fluoroscopy-, CT-guidance, and low-dose CT-guidance for intra-articular SI joint injections.
Study design
Comparative study with technical considerations.
Methods
A total of 30 CT-guided intra-articular SI joint injections were performed in January 2012 in a developed low-dose mode and the radiation doses were calculated. They were compared to 30 pulsed-fluoroscopy-guided SI joint injections, which were performed in the month before, and to five injections, performed in standard CT-guided biopsy mode for spinal interventions. The statistical significance was calculated with the SPSS software using the Mann–Whitney U-Test. Technical details and anatomical considerations were provided.
Results
A significant dose reduction of average 94.01% was achieved using the low-dose protocol for CT-guided SI joint injections. The radiation dose could be approximated to pulsed-fluoroscopy- guidance levels.
Conclusion
Radiation dose of CT-guided SI joint injections can be decreased to levels of pulsed fluoroscopy with a precise intra-articular needle placement using the low-dose protocol. The technique is simple to perform, fast, and reproducible.
doi:10.2147/JPR.S34429
PMCID: PMC3442745  PMID: 23028237
sacroiliac joint pain; computed tomography; guided injections; low-dose protocol; sacroiliac joint injection; low back pain; radiation dose
6.  Comparison of Percutaneous Endoscopic Lumbar Discectomy and Open Lumbar Microdiscectomy for Recurrent Disc Herniation 
Objective
The purpose of this study was to compare clinical and radiological outcomes of percutaneous endoscopic lumbar discectomy (PELD) and open lumbar microdiscectomy (OLM) for recurrent disc herniation.
Methods
Fifty-four patients, who underwent surgery, either PELD (25 patients) or repeated OLM (29 patients), due to recurrent disc herniation at L4-5 level, were divided into two groups according to the surgical methods. Excluded were patients with sequestrated disc, calcified disc, severe neurological deficit, or instability. Clinical outcomes were assessed using Visual Analogue Scale (VAS) score and Oswestry Disability Index (ODI). Radiological variables were assessed using plain radiography and/or magnetic resonance imaging.
Results
Mean operating time and hospital stay were significantly shorter in PELD group (45.8 minutes and 0.9 day, respectively) than OLM group (73.8 minutes and 3.8 days, respectively) (p < 0.001). Complications occurred in 4% in PELD group and 10.3% in OLM group in the perioperative period. At a mean follow-up duration of 34.2 months, the mean improvements of back pain, leg pain, and functional improvement were 4.0, 5.5, and 40.9% for PELD group and 2.3, 5.1, and 45.0% for OLM group, respectively. Second recurrence occurred in 4% after PELD and 10.3% after OLM. Disc height did not change after PELD, but significantly decreased after OLM (p = 0.0001). Neither sagittal rotation angle nor volume of multifidus muscle changed significantly in both groups.
Conclusion
Both PELD and repeated OLM showed favorable outcomes for recurrent disc herniation, but PELD had advantages in terms of shorter operating time, hospital stay, and disc height preservation.
doi:10.3340/jkns.2009.46.6.515
PMCID: PMC2803265  PMID: 20062565
Reherniation; Discectomy; Lumbar spine
7.  Risk of whole body radiation exposure and protective measures in fluoroscopically guided interventional techniques: a prospective evaluation 
BMC Anesthesiology  2003;3:2.
Background
Fluoroscopic guidance is frequently utilized in interventional pain management. The major purpose of fluoroscopy is correct needle placement to ensure target specificity and accurate delivery of the injectate. Radiation exposure may be associated with risks to physician, patient and personnel. While there have been many studies evaluating the risk of radiation exposure and techniques to reduce this risk in the upper part of the body, the literature is scant in evaluating the risk of radiation exposure in the lower part of the body.
Methods
Radiation exposure risk to the physician was evaluated in 1156 patients undergoing interventional procedures under fluoroscopy by 3 physicians. Monitoring of scattered radiation exposure in the upper and lower body, inside and outside the lead apron was carried out.
Results
The average exposure per procedure was 12.0 ± 9.8 seconds, 9.0 ± 0.37 seconds, and 7.5 ± 1.27 seconds in Groups I, II, and III respectively. Scatter radiation exposure ranged from a low of 3.7 ± 0.29 seconds for caudal/interlaminar epidurals to 61.0 ± 9.0 seconds for discography. Inside the apron, over the thyroid collar on the neck, the scatter radiation exposure was 68 mREM in Group I consisting of 201 patients who had a total of 330 procedures with an average of 0.2060 mREM per procedure and 25 mREM in Group II consisting of 446 patients who had a total of 662 procedures with average of 0.0378 mREM per procedure. The scatter radiation exposure was 0 mREM in Group III consisting of 509 patients who had a total 827 procedures. Increased levels of exposures were observed in Groups I and II compared to Group III, and Group I compared to Group II.
Groin exposure showed 0 mREM exposure in Groups I and II and 15 mREM in Group III. Scatter radiation exposure for groin outside the apron in Group I was 1260 mREM and per procedure was 3.8182 mREM. In Group II the scatter radiation exposure was 400 mREM and with 0.6042 mREM per procedure. In Group III the scatter radiation exposure was 1152 mREM with 1.3930 mREM per procedure.
Conclusion
Results of this study showed that scatter radiation exposure to both the upper and lower parts of the physician's body is present. Protection was offered by traditional measures to the upper body only.
doi:10.1186/1471-2253-3-2
PMCID: PMC194671  PMID: 12904269
8.  Percutaneous pedicle screw placement in the thoracic spine: A cadaveric study 
Asian Journal of Neurosurgery  2013;8(3):153-156.
Study Design:
A cadaveric study to determine the accuracy of percutaneous screw placement in the thoracic spine using standard fluoroscopic guidance.
Summary of Background Data:
While use of percutaneous pedicle screws in the lumbar spine has increased rapidly, its acceptance in the thoracic spine has been slower. As indications for pedicle screw fixation increase in the thoracic spine so will the need to perform accurate and safe placement of percutaneous screws with or without image navigation. To date, no study has determined the accuracy of percutaneous thoracic pedicle screw placement without use of stereotactic imaging guidance.
Materials and Methods:
Eighty-six thoracic pedicle screw placements were performed in four cadaveric thoracic spines from T1 to T12. At each level, Ferguson anterior–posterior fluoroscopy was used to localize the pedicle and define the entry point. Screw placement was attempted unless the borders of the pedicle could not be delineated solely using intraoperative fluoroscopic guidance. The cadavers were assessed using pre- and postprocedural computed tomography (CT) scans as well as dissected and visually inspected in order to determine the medial breach rate.
Results:
Ninety pedicles were attempted and 86 screws were placed. CT analysis of screw placement accuracy revealed that only one screw (1.2%) breached the medial aspect of the pedicle by more than 2 mm. A total of four screws (4.7%) were found to have breached medially by visual inspection (three Grade 1 and one Grade 2). One (1.2%) lateral breach was greater than 2 mm and no screw violated the neural foramen. The correlation coefficient of pedicle screw violations and pedicle diameter was found to be 0.96.
Conclusions:
This cadaveric study shows that percutaneous pedicle screw placement can be performed in the thoracic spine without a significant increase in the pedicle breach rate as compared with standard open techniques. A small percentage (4.4%) of pedicles, especially high in the thoracic spine, may not be safely visualized.
doi:10.4103/1793-5482.121687
PMCID: PMC3877502  PMID: 24403958
Minimally invasive surgery; pedicle screw; thoracic spine
9.  Novel free-hand T1 pedicle screw method: Review of 44 consecutive cases 
Summary of Background Data:
Multilevel posterior cervical instrumented fusions are becoming more prevalent in current practice. Biomechanical characteristics of the cervicothoracic junction may necessitate extending the construct to upper thoracic segments. However, fixation in upper thoracic spine can be technically demanding owing to transitional anatomy while suboptimal placement facilitates vascular and neurologic complications. Thoracic instrumentation methods include free-hand, fluoroscopic guidance, and CT-based image guidance. However, fluoroscopy of upper thoracic spine is challenging secondary to vertebral geometry and patient positioning, while image-guided systems present substantial financial commitment and are not readily available at most centers. Additionally, imaging modalities increase radiation exposure to the patient and surgeon while potentially lengthening surgical time.
Materials and Methods:
Retrospective review of 44 consecutive patients undergoing a cervicothoracic fusion by a single surgeon using the novel free-hand T1 pedicle screw technique between June 2009 and November 2012. A starting point medial and cephalad to classic entry as well as new trajectory were utilized. No imaging modalities were employed during screw insertion. Postoperative CT scans were obtained on day 1. Screw accuracy was independently evaluated according to the Heary classification.
Results:
In total, 87 pedicle screws placed were at T1. Grade 1 placement occurred in 72 (82.8%) screws, Grade 2 in 4 (4.6%) screws and Grade 3 in 9 (10.3%) screws. All Grade 2 and 3 breaches were <2 mm except one Grade 3 screw breaching 2-4 mm laterally. Only two screws (2.3%) were noted to be Grade 4, both breaching medially by less than 2 mm. No new neurological deficits or returns to operating room took place postoperatively.
Conclusions:
This modification of the traditional starting point and trajectory at T1 is safe and effective. It attenuates additional bone removal or imaging modalities while maintaining a high rate of successful screw placement compared to historical controls.
doi:10.4103/0976-3147.139974
PMCID: PMC4173230  PMID: 25288835
Cervicothoracic; free-hand; pedicle screw; technique; thoracic; thoracic starting points
10.  Ultrasound-Guided (Needle In-Plane) Perineural Catheter Insertion: The Effect of Catheter Insertion Distance on Postoperative Analgesia 
Background
When using ultrasound guidance to place a perineural catheter for a continuous peripheral nerve block, keeping the needle-in plane and nerve in short-axis results in a perpendicular needle-to-nerve orientation. Many have opined that when placing a perineural catheter via the needle, the acute angle may result in the catheter bypassing the target nerve when advanced beyond the needle tip. Theoretically, greater catheter tip-to-nerve distances result in less local anesthetic-to-nerve contact during the subsequent perineural infusion, leading to inferior analgesia. While a potential solution may appear obvious—advancing the catheter tip only to the tip of the needle, leaving the catheter tip at the target nerve—this technique has not been prospectively evaluated. We therefore hypothesized that during needle in-plane ultrasound-guided perineural catheter placement, inserting the catheter a minimum distance (0-1 cm) past the needle tip is associated with improved postoperative analgesia compared with inserting the catheter a more-traditional 5-6 cm past the needle tip.
Methods
Preoperatively, subjects received a popliteal-sciatic perineural catheter for foot or ankle surgery using ultrasound guidance exclusively. Subjects were randomly assigned to have a single-orifice, flexible catheter inserted either 0-1 (n=50) or 5-6 cm (n=50) past the needle tip. All subjects received a single-injection mepivacaine (40 mL of 1.5% with epinephrine) nerve block via the needle, followed by catheter insertion and a ropivacaine 0.2% infusion (basal 6 mL/h, bolus 4 mL, 30 min lockout), through at least the day following surgery. The primary end point was average surgical pain as measured with a 0-10 numeric rating scale the day following surgery. Secondary end points included time for catheter insertion, incidence of catheter dislodgement, maximum (“worst”) pain scores, opioid requirements, fluid leakage at the catheter site, and the subjective degree of an insensate extremity.
Results
Average pain scores the day following surgery for subjects of the 0-1 cm group was a median (interquartile) of 2.5 (0.0-5.0), compared with 2.0 (0.0-4.0) for subjects of the 5-6 cm group (p=0.42). Similarly, among the secondary end points, no statistically significant differences were found between the two treatment groups. There was a trend of more catheter dislodgements in the minimum-insertion group (5 vs. 1; p=0.20).
Conclusions
This study did not find evidence to support the hypothesis that for popliteal-sciatic perineural catheters placed using ultrasound guidance and a needle in-plane technique, inserting the catheter a minimum distance (0-1 cm) past the needle tip improves (or worsens) postoperative analgesia compared with inserting the catheter a more-traditional distance (5-6 cm). Caution is warranted if extrapolating these results to other catheter designs, ultrasound approaches, or anatomic insertion sites.
doi:10.1097/AAP.0b013e31820f3b80
PMCID: PMC3085850  PMID: 21519311
11.  3D cone-beam CT guidance, a novel technique in renal biopsy—results in 41 patients with suspected renal masses 
European Radiology  2012;22(11):2547-2552.
Objective
To determine whether 3D cone-beam computed tomography (CBCT) guidance allows safe and accurate biopsy of suspected small renal masses (SRM), especially in hard-to-reach anatomical locations.
Materials and methods
CBCT guidance was used to perform 41 stereotactic biopsy procedures of lesions that were inaccessible for ultrasound guidance or CT guidance. In CBCT guidance, a 3D-volume data set is acquired by rotating a C-arm flat-panel detector angiosystem around the patient. In the data set, a needle trajectory is determined and, after co-registration, a fusion image is created from fluoroscopy and a slice from the data set, enabling the needle to be positioned in real time.
Results
Of the 41 lesions, 22 were malignant, 17 were benign, and 2 were nondiagnostic. The two nondiagnostic lesions proved to be renal cell carcinoma. There was no growth during follow-up imaging of the benign lesions (mean 29 months). This resulted in a sensitivity, specificity, PPV, NPV, and accuracy of 91.7, 100, 100, 89.5, and 95.1%, respectively. Mean dose-area product value was 44.0 Gy·cm2 (range 16.5–126.5). There was one minor bleeding complication.
Conclusion
With CBCT guidance, safe and accurate biopsy of a suspected SRM is feasible, especially in hard-to-reach locations of the kidney.
Key Points
• Cone-beam computed tomography has potential advantages over conventional CT for interventional procedures.
• CBCT guidance incorporates 3D CBCT data, fluoroscopy, and guidance software.
• In hard-to-reach renal masses, CBCT guidance offers an alternative biopsy method.
• CBCT guidance offers good outcome and safety and has potential clinical significance.
doi:10.1007/s00330-012-2498-y
PMCID: PMC3472072  PMID: 22660984
Percutaneous biopsy; Cone-beam CT; Small renal masses; Outcome; Hard-to-reach
12.  An Evaluation of Image-Guided Technologies in the Placement of Anterior Thoracic Vertebral Body Screws in Spinal Trauma: A Cadaver Study 
Background:
Image guidance provides additional anatomic information to the surgeon, which may allow more accurate insertion of spinal implants. Imprecise placement of anterior thoracic screws places the spinal cord and paraspinal structures at risk for injury. Image guidance may afford a safety benefit to patients when anterior thoracic screws are required in the setting of spinal stabilization after trauma.
Objectives:
To compare the accuracy of anterior thoracic screw placement using standard fluoroscopy, computer-assisted fluoroscopic image guidance, Iso-C3D image guidance, and electromagnetic fluoroscopic image guidance.
Study Design:
A surgical simulation study in human cadaver spine specimens.
Methods:
After an open thoracotomy approach, anterior thoracic screws were placed by experienced spine surgeons using 4 different image-guided techniques in 4 human cadaver thoracic spines. Screws were placed in the 9th, 10th, and 11th thoracic vertebrae of each specimen. The specimens were then examined with thin-cut computed tomography (CT) scans, and with sagittal and coronal reconstructions. Measurements included the distance of the screw from the spinal canal, the angle of the screw path in relation to a perpendicular to a line that bisects the spinous process, and the angle of screw divergence from the superior endplate.
Results:
There was no evidence of spinal canal penetrance with any of the image-guided techniques used to place anterior thoracic vertebral body screws. Screws inserted with standard fluoroscopy tended to aim anterolaterally by 18°. The image-guidance systems allowed more accurate placement of anterior thoracic screws in the transverse plane compared with standard fluoroscopy. There was no statistically significant difference in coronal plane screw angulation (angle of divergence with the superior endplate) between any of the imaging methods.
Conclusions:
Spinal image-guidance systems may allow spine surgeons to place anterior thoracic screws more precisely, particularly in the axial plane. The improved accuracy of spinal implant insertion could ultimately provide a benefit to patient safety, especially in the setting of malaligned vertebral bodies after trauma.
PMCID: PMC1864896  PMID: 16396380
Image-guided surgery; StealthStation; FluoroNav; Iso-C3D; Spinal instrumentation; Thoracic spine fixation; Anterior thoracic screws; Spinal cord injuries; Trauma
13.  Computed tomography-guided vertebroplasty using a stereotactic guidance system (stereo-guide) 
Background
In order to make it easy to perform computed tomography (CT)-guided vertebroplasty a stereotactic guidance system called the "stereo-guide" was designed. A method to perform CT-guided vertebroplasty using this system is described.
Methods
The device is a rectangular flat plastic block. One of the flat surfaces of the block has deeply grooved protractor markings at 5-degree intervals; ranging from 0 to 30 degrees. The procedure is performed on the CT table. Based on distances and angle measurements obtained from CT images the device is placed on an appropriate location on the back of the patient and the needle is advanced to the target through the pedicle guided by the grooves on the device. Ten procedures were performed in nine patients with lumbar and thoracic pathology.
Results
The system was easy to use and proved to be accurate. No complication resulted from the procedure.
Conclusion
The stereo-guide proved to be simple and easy to use. Intraoperative scans helped to plan the trajectory and follow the injection of the cement.
doi:10.4103/2152-7806.63912
PMCID: PMC2908353  PMID: 20657698
Computed tomography guidance; stereotactic; vertebral fracture; vertebroplasty
14.  Cardiac embolization of an implanted fiducial marker for hepatic stereotactic body radiotherapy: a case report 
Introduction
In liver stereotactic body radiotherapy, reduction of normal tissue irradiation requires daily image guidance. This is typically accomplished by imaging a surrogate to the tumor. The surrogate is often an implanted metal fiducial marker. There are few reports addressing the specific risks of hepatic fiducial marker implantation. These risks are assumed to be similar to percutaneous liver biopsies which are associated with a 1-4% complication rate - almost always pain or bleeding. To the best of our knowledge, we present the first case of such a fiducial marker migrating to the heart.
Case presentation
An 81-year-old Caucasian man (5 years post-gastrectomy for a gastric adenocarcinoma) was referred post-second line palliative chemotherapy for radiotherapy of an isolated liver metastasis. It was decided to proceed with treatment and platinum fiducials were chosen for radiation targeting. Under local anesthesia, three Nester embolization coils (Cook Medical Inc., Bloomington, IN, USA) were implanted under computed tomography guidance. Before the placement of each coil, the location of the tip of the delivery needle was confirmed by computed tomography imaging. During the procedure, the third coil unexpectedly migrated through the hepatic vein to the inferior vena cava and lodged at the junction of the vena cava and the right atrium. The patient remained asymptomatic. He was immediately referred to angiography for extraction of the coil. Using fluoroscopic guidance, an EN Snare Retrieval System (Hatch Medical L.L.C., Snellville, GA, USA) was introduced through a jugular catheter; it successfully grasped the coil and the coil was removed. The patient was kept overnight for observation and no immediate or delayed complications were encountered due to the migration or retrieval of the coil. He subsequently went on to be treated using the remaining fiducials.
Conclusion
Implanted fiducial markers are increasingly used for stereotactic radiotherapy. There is sparse literature on the risks of such procedures. Although uncommon, the risk of migration does exist and therefore physicians (surgeons, oncologists and radiologists) and patients should be aware of this possibility.
doi:10.1186/1752-1947-3-140
PMCID: PMC2783068  PMID: 19946545
15.  Ultrasound as a Screening Tool for Performing Caudal Epidural Injections 
Iranian Journal of Radiology  2014;11(2):e13262.
Background:
The caudal approach to the epidural space has been used for decades to treat low back pain caused by lumbosacral root compression. The use of fluoroscopy during epidural steroid injection is the preferred method for placing the needle more accurately in the sacral hiatus, but it carries the risk of radiation hazard.
Objectives:
The aim of the study was to assess the anatomical structure of the sacral hiatus and the feasibility of caudal epidural injections under ultrasound guidance.
Patients and Methods:
Two hundred and forty patients (male = 100, female = 140) with low back pain and sciatica who were candidates for caudal epidural injection were enrolled into this study. Ultrasound images of the sacral hiatus and bilateral cornua were obtained by a real-time linear array ultrasound transducer. The distance between bilateral cornua and the anterior and posterior wall of the sacrum were measured at the base (sacral hiatus). Under the guide of ultrasonography, we defined the injection successful if turbulence of medication fluid was observed in the sacral canal, but correct placement of the needle and injectant was confirmed on fluoroscopic view as the gold standard technique.
Results:
The epidurogram showed that the injection was successful in 230 of the 240 patients (95.8%). In eight patients, the injection was not in the correct place in the sacral canal. The sacral hiatus could not be identified by ultrasound images in only two patients who had a closed sacral hiatus identified by fluoroscopy. The mean distance of the sacral hiatus was 4.7 ± 1.7 mm and the mean distance between bilateral cornua was 18.0 ± 2.8 mm. The mean duration of the procedure was 10.8 ± 6.8 minutes. No major complication was observed in the next month.
Conclusions:
In conclusion, ultrasound could be used as a safe, fast and reliable modality to observe the anatomic variation of the sacral hiatus and to perform caudal epidural injections.
doi:10.5812/iranjradiol.13262
PMCID: PMC4090639  PMID: 25035698
Anesthesia, Caudal; Ultrasonography; Low Back Pain
16.  Role of high-field intraoperative magnetic resonance imaging on a multi-image fusion-guided stereotactic biopsy of the basal ganglia: A case report 
Oncology Letters  2014;9(1):223-226.
The aim of the present case study was to investigate the advantages of intraoperative magnetic resonance imaging (iMRI) on the real-time guidance and monitoring of a stereotactic biopsy. The study describes a patient with intracranial lesions, which were examined by conventional MRI and diffusion tensor imaging using a 1.5T intraoperative MRI system. The digital and pre-operative positron emission/computed tomography image data were transferred to a BrainLAB planning workstation, and a variety of images were automatically fused. The BrainLAB software was then used to reconstruct the corticospinal tract (CST) and create a three-dimensional display of the anatomical association between the CST and the brain lesions. A Leksell surgical planning workstation was used to identify the ideal target site and a reasonable needle track for the biopsy. The 1.5T iMRI was used to effectively monitor the intracranial condition during the brain biopsy procedure. Post-operatively, the original symptoms of the patient were not aggravated and no further neurological deficits were apparent. The histopathological diagnosis of non-Hodgkin’s B-cell lymphoma was made. Using high-field iMRI, the multi-image fusion-guided stereotactic brain biopsy allows for a higher positive rate of biopsy and a lower incidence of complications. The approach of combining multi-image fusion images with the frame-based stereotactic biopsy may be clinically useful for intracranial lesions of deep functional areas.
doi:10.3892/ol.2014.2680
PMCID: PMC4246638  PMID: 25435963
intraoperative magnetic resonance imaging; multi-image fusion; stereotactic; biopsy
17.  Validation of a magnetic resonance imaging guided stereotactic access to the ovine brainstem 
BMC Veterinary Research  2014;10(1):216.
Background
Anatomical differences between humans and domestic mammals preclude the use of reported stereotactic approaches to the brainstem in animals. In animals, brainstem biopsies are required both for histopathological diagnosis of neurological disorders and for research purposes. Sheep are used as a translational model for various types of brain disease and therefore a species-specific approach needs to be developed. The aim of the present study was to establish a minimally invasive, accurate and reproducible stereotactic approach to the brainstem of sheep, using the magnetic resonance imaging guided BrainsightTM frameless stereotactic system.
Results
A transoccipital transcerebellar approach with an entry point in the occipital bone above the vermis between the transverse sinus and the external occipital protuberance was chosen. This approach provided access to the target site in all heads. The overall mean needle placement error was 1.85 ± 1.22 mm.
Conclusions
The developed transoccipital transcerebellar route is short, provides accurate access to the ovine caudal cranial fossa and is a promising approach to be further assessed in live animals.
doi:10.1186/s12917-014-0216-5
PMCID: PMC4177427  PMID: 25241810
Sheep; Brainstem; Stereotaxy; Transcerebellar route; Large animal model
18.  MR-guidance – a clinical study to evaluate a shuttle- based MR-linac connection to provide MR-guided radiotherapy 
Background
The purpose of this clinical study is to investigate the clinical feasibility and safety of a shuttle-based MR-linac connection to provide MR-guided radiotherapy.
Methods/Design
A total of 40 patients with an indication for a neoadjuvant, adjuvant or definitive radiation treatment will be recruited including tumors of the head and neck region, thorax, upper gastrointestinal tract and pelvic region. All study patients will receive standard therapy, i.e. highly conformal radiation techniques like CT-guided intensity-modulated radiotherapy (IMRT) with or without concomitant chemotherapy or other antitumor medication, and additionally daily short MR scans in treatment position with the same immobilisation equipment used for irradiation for position verification and imaging of the anatomical and functional changes during the course of radiotherapy. For daily position control, skin marks and a stereotactic frame will be used for both imaging modalities. Patient transfer between the MR device and the linear accelerator will be performed with a shuttle system which uses an air-bearing patient platform for both procedures. The daily acquired MR and CT data sets will be digitally registrated, correlated with the planning CT and compared with each other regarding translational and rotational errors. Aim of this clinical study is to establish a shuttle-based approach for realising MR-guided radiotherapy for certain clinical situations. Second objectives are to compare MR-guided radiotherapy with the gold standard of CT image guidance for quality assurance of radiotherapy, to establish an appropiate MR protocol therefore, and to assess the possibility of using MR-based image guidance not only for position verification but also for adaptive strategies in radiotherapy.
Discussion
Compared to CT, MRI might offer the advantage of providing IGRT without delivering an additional radiation dose to the patients and the possibility of optimisation of adaptive therapy strategies due to its superior soft tissue contrast. However, up to now, hybrid MR-linac devices are still under construction and not clinically applicable. For the near future, a shuttle-based approach would be a promising alternative for providing MR-guided radiotherapy, so that the present study was initiated to determine feasibility and safety of such an approach. Besides positioning information, daily MR data under treatment offer the possibility to assess tumor regression and functional parameters, with a potential impact not only on adaptive therapy strategies but also on early assessment of treatment response.
doi:10.1186/1748-717X-9-12
PMCID: PMC3904210  PMID: 24401489
IGRT; MR-guided radiotherapy; Dose reduction; Shuttle
19.  Piriformis syndrome after percutaneous endoscopic lumbar discectomy via the posterolateral approach 
European Spine Journal  2011;20(10):1663-1668.
Percutaneous endoscopic lumbar discectomy (PELD) can be performed under local anesthesia with intravenous analgesics. To define the incidence of piriformis syndrome (PS) after PELD via the posterolateral approach under local anesthesia compared to that of general patients presenting with low back pain with/without lower leg pain. The incidence and time of occurrence of positive FAIR test after PELD within a 3-month follow-up period were evaluated retrospectively, and compared with the prevalence of general patients who visited the pain clinic for LBP with/without lower leg pain. Factors that may increase the incidence of PS after PELD were also evaluated. There was no patient with positive FAIR test immediately after PELD in the operation room and before walking. The prevalence of PS in general patients was 317/2,320 (13.7%); however, the incidence of PS after PELD within a 3-month follow-up period was 61/151 (40.4%), peaking at 32 days. High anxiety scale scores during operation led to increased incidence of PS after PELD. PELD under local anesthesia with high level of anxiety may increase the incidence of PS after walking, peaking around the first month, compared with the results for general patients with low back pain with/without lower leg pain.
doi:10.1007/s00586-011-1764-z
PMCID: PMC3175870  PMID: 21416279
Diskectomy; Endoscopy; Lumbar vertebrae; Percutaneous; Piriformis syndrome
20.  An Analysis of Location of Needle Entry Point and Palpated PSIS in S1 Nerve Root Block 
The Korean Journal of Pain  2010;23(4):242-246.
Background
The first sacral nerve root block (S1NRB) is a common procedure in pain clinic for patients complaining of low back pain with radiating pain. It can be performed in the office based setting without C-arm. The previously suggested method of locating the needle entry point begins with identifying the posterior superior iliac spine (PSIS). Then a line is drawn between two points, one of which is 1.5 cm medial to the PSIS, and the other of which is 1.5 cm lateral and cephalad to the ipsilateral cornu. After that, one point on the line, which is 1.5 cm cephalad to the level of the PSIS, is considered as the needle entry point. The purpose of this study was to analyze the location of needle entry point and palpated PSIS in S1NRB.
Methods
Fifty patients undergoing C-arm guided S1NRB in the prone position were examined. The surface anatomical relationships between the palpated PSIS and the needle entry point were assessed.
Results
The analysis revealed that the transverse and vertical distance between the needle entry point and PSIS were 28.7 ± 8.8 mm medially and 3.5 ± 14.0 mm caudally, respectively. The transverse distance was 27.8 ± 8.3 mm medially for male and 29.5 ± 9.3 mm medially for female. The vertical distance was 1.0 ± 14.1 mm cranially for male and 8.1 ± 12.7 mm caudally for female.
Conclusions
The needle entry point in S1NRB is located on the same line or in the caudal direction from the PSIS in a considerable number of cases. Therefore previous recommended methods cannot be applied to many cases.
doi:10.3344/kjp.2010.23.4.242
PMCID: PMC3000620  PMID: 21217887
first sacral nerve root block; needle entry point; posterior superior iliac spine
21.  Vertebral Artery Position in the Setting of Cervical Degenerative Disease: Implications for Selective Cervical Transforaminal Epidural Injections 
Interventional Neuroradiology  null;19(4):425-431.
Summary
Cervical transforaminal epidural injections (C-TfEI) are commonly performed in patients with cervical radiculopathy/pain. C-TfEIs are typically performed without incident but adverse events can occur. Using CT-fluoroscopy-guided C-TfEI, we commonly observe the vertebral artery in proximity to the target injection site. The purpose of this study was to assess the position of the vertebral artery relative to the typical C-TfEI injection point.
CT-fluoroscopy-guided C-TfEIs were performed at 70 levels in 68 patients with radiculopathy/neck pain (age range 19-83 yrs, mean 50.6 yrs). Degenerative neural foraminal narrowing at each level was characterized (normal-to-mild, moderate, severe). Vertebral artery position was categorized as: anterior (normal), partially covering neural foramen, complete/near-complete covering the neural foramen. Additional measured variables included angle of needle trajectory, foraminal angle, and whether or not needle trajectory intersected with the vertebral artery.
Foraminal vertebral artery covering correlated with severity of foraminal degenerative narrowing (p=0.003). Complete/near-complete covering was seen in: 65% severely narrowed foramina, 30% moderately narrowed foramina and 10% normal/mildly-narrowed foramina. Needle trajectory intersected with the vertebral artery in 30 of 70 injections (46%) by CT-fluoroscopy, frequently associated with shallow (lateral) approaches. Foraminal angle, approximating oblique fluoroscopic technique, suggests needle trajectory intersection with the vertebral artery in 27 of 70 foramina (39%).
Vertebral artery position is commonly displaced into the foramen in patients with advanced cervical degenerative disease. Operator awareness of altered vertebral artery position is important for determination of optimal needle trajectory and tip placement prior to injection in patients undergoing C-TfEI.
PMCID: PMC3902740  PMID: 24355145
cervical spine; cervical radiculopathy; neck pain; cervical transforaminal epidural injection; cervical nerve root block; computed tomography
22.  Real-Time MRI-Guided Cryoablation of Small Renal Tumors at 1.5 T 
Investigative radiology  2013;48(6):437-444.
Objectives
Real-time magnetic resonance imaging (MRI)-guided cryoablation has been investigated in open MRI systems with low magnetic fields (0.2–0.5 T). More advanced imaging techniques and faster imaging rates are possible at higher magnetic fields which often require a closed-bore magnet design. However, there is very little experience with real-time interventions in closed-bore 1.5 T MRI units. Herein, we report our initial experience with real-time MRI-guided cryoablation of small renal tumors using a prototype balanced steady-state free precession (bSSFP) imaging sequence in a closed-bore 1.5-T MRI system.
Materials and Methods
From August 2008 to April 2012, 18 patients underwent MRI-guided cryoablation of small renal tumors. A 1.5-T cylindrical MRI scanner with a 125 cm × 70 cm bore and a prototype bSSFP sequence (BEAT IRTTT) were used to guide the placement of 17-gauge cryoprobes in real time. Ice ball formation was monitored every 3 minutes in one or more imaging planes. Each ablation consisted of 2 freeze-thaw cycles. Contrast-enhanced MRI was performed after the second active thaw period. Follow-up consisted of clinical evaluation and renal protocol computed tomography (CT) or MRI performed at 1, 6, 12, 18, and 24 months and annually thereafter.
Results
During the study period, we successfully ablated 18 tumors in 18 patients in 18 sessions. The mean tumor size was 2.2 cm (median, 2 cm; range: 1.2–4.4 cm). The number of cryoprobes used per patient was determined based on tumor size. The mean number of cryoprobes used per patient was 3 (median, 3 cryoprobes; range, 2–4 cryoprobes). Fifty-six cryoprobes, 9 biopsy needles, and 2 hydrodissection needles were successfully placed under real time MRI guidance using BEAT IRTTT sequence. Hydrodissection under MRI guidance was successfully performed in 4 patients. In each patient, contrast-enhanced MRI performed after the second active thaw period revealed a sharply defined avascular zone surrounding the targeted tumor, which confirmed complete ablation of the tumor with adequate margins. Although contrast media slowly accumulated in the targeted tumor in 9 patients immediately after the procedure, follow-up imaging studies performed at a mean of 16.7 months revealed no contrast enhancement within the ablation zone in these patients. Disease-specific, metastasis-free, and local recurrence–free survival rates were all 100%.
Conclusions
Real-time placement and manipulation of cryoprobes during MRI-guided cryoablation of small renal tumors in a closed-bore, high–magnetic field scanner is feasible. Technical and clinical success rates are similar to those of patients who undergo CT-guided radiofrequency ablation or cryoablation of small renal tumors. Our findings suggest that MRI-guided ablation has several advantages over CT-guided ablation, including real-time guidance for probe placement, multiplanar imaging, exquisite soft tissue contrast, and lack of ionizing radiation.
doi:10.1097/RLI.0b013e31828027c2
PMCID: PMC3899798  PMID: 23511191
Renal cell carcinoma; renal tumor; cryoablation; interventional MRI
23.  The Validation of Ultrasound-Guided Lumbar Facet Nerve Blocks as Confirmed by Fluoroscopy 
Asian Spine Journal  2012;6(3):163-167.
Study Design
This is a prospective study.
Purpose
To develop a methodological approach for conducting ultrasound-guided lumbar facet nerve block by defining essential ultrasound-guided landmarks in order to assess the feasibility of this method.
Overview of Literature
The current role of ultrasound guidance for musculoskeletal intervention treatments has been reported upon in previous literature.
Methods
Ultrasound-guided facet nerve block was done in 95 segments for 50 patients with chronic back pain by facet arthropathy. After the surface landmarks of the spinous process and iliac crest line were confirmed, longitudinal facet views were obtained by a curved array transducer to identify the different spinal segments. The spinous process and facet joint with transverse process were delineated by transverse sonograms at each level and the target point for the block was defined as lying on the upper edge of the transverse process. The needle was inserted toward the target point. After a contrast injection, the placement of the needle and contrast was checked by fluoroscopy.
Results
Eighty-seven segments (91.6%) could be guided successfully to the right facet nerve block by using ultrasound. After fluoroscopic control, 8 needles had to be corrected because of problems with other segments (3 cases) and lamina placements (5 cases). For the 42 patients who underwent successful block by ultrasound, however, the mean visual analogue score for back pain was improved from 6.2 ± 0.9 before the block to 4.0 ± 1.0 after the block (p = 0.001).
Conclusions
Ultrasound-guided longitudinal facet view and the surface landmarks of the spinous process and iliac crest line seems to be a promising guidance technique for the lumbar facet nerve block technique.
doi:10.4184/asj.2012.6.3.163
PMCID: PMC3429606  PMID: 22977695
Lumbosacral region; Nerve block; Ultrasonography
24.  The treatment of primary and metastatic renal cell carcinoma (RCC) with image-guided stereotactic body radiation therapy (SBRT) 
Purpose:
Brain metastases from renal cell carcinoma (RCC) have been successfully treated with stereotactic radiosurgery (SRS). Metastases to extra-cranial sites may be treated with similar success using stereotactic body radiation therapy (SBRT), where image-guidance allows for the delivery of precise high-dose radiation in a few fractions. This paper reports the authors’ initial experience with image-guided SBRT in treating primary and metastatic RCC.
Materials and methods:
The image-guided Brainlab Novalis stereotactic system was used. Fourteen patients with 23 extra-cranial metastatic RCC lesions (orbits, head and neck, lung, mediastinum, sternum, clavicle, scapula, humerus, rib, spine and abdominal wall) and two patients with biopsy-proven primary RCC (not surgical candidates) were treated with SBRT (24-40 Gy in 3-6 fractions over 1-2 weeks). All patients were immobilised in body cast or head and neck mask. Image-guidance was used for all fractions. PET/CT images were fused with simulation CT images to assist in target delineation and dose determination. SMART (simultaneous modulated accelerated radiation therapy) boost approach was adopted. 4D-CT was utilised to assess tumour/organ motion and assist in determining planning target volume margins.
Results:
Median follow-up was nine months. Thirteen patients (93%) who received SBRT to extra-cranial metastases achieved symptomatic relief. Two patients had local progression, yielding a local control rate of 87%. In the two patients with primary RCC, tumour size remained unchanged but their pain improved, and their renal function was unchanged post SBRT. There were no significant treatment-related side effects.
Conclusion:
Image-guided SBRT provides excellent symptom palliation and local control without any significant toxicity. SBRT may represent a novel, non-invasive, nephron-sparing option for the treatment of primary RCC as well as extra-cranial metastatic RCC.
doi:10.2349/biij.3.1.e6
PMCID: PMC3097653  PMID: 21614267
Renal cell carcinoma (RCC); primary and metastatic RCC; Image Guided Radiation Therapy (IGRT); Stereotactic Body Radiation Therapy (SBRT)
25.  Minimally invasive percutaneous transpedicular screw fixation: increased accuracy and reduced radiation exposure by means of a novel electromagnetic navigation system 
Acta Neurochirurgica  2010;153(3):589-596.
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.
doi:10.1007/s00701-010-0882-4
PMCID: PMC3040822  PMID: 21153669
Minimally invasive; Electromagnetic field navigation; Pedicle screw; Fluoroscopy; Accuracy

Results 1-25 (972475)