Operating room radiation exposure in cone beam computed tomography-based, image-guided spinal surgery: clinical article

[Spinal navigation with preoperative computed tomography]

OBJECTIVE

Safe placement of posterior cervical-sacral pedicle screws, S2-Ala-iliac screws, iliac screws, transarticular screws C1/2, translaminar screws C2 or cervical lateral mass screws under the guidance of spinal navigation.

INDICATIONS

All posterior spinal instrumentations with screws: instabilities and deformities of rheumatic, traumatic, neoplastic, infectious, iatrogenic or congenital origin; multilevel cervical spinal stenosis with degenerative instability or kyphosis of the affected spinal segment.

CONTRAINDICATIONS

There are no absolute contraindications for spinal navigation.

SURGICAL TECHNIQUE

Cervical spine: Prone position on a gel mattress, rigid head fixation, e.g., with Mayfield tongs; if appropriate, closed reduction under lateral image intensification; thoracic + lumbar spine: prone position on a cushioned frame; midline posterior surgical approach at the level of the segments to be instrumented; if necessary, open reduction; insertion of the cervical/upper thoracic screws under the guidance of spinal navigation; if necessary, posterior decompression; instrumentation longitudinal rods; if fusion is to be obtained, decortication of the posterior bone elements with a high-speed burr and onlay of cancellous bone or bone substitutes.

POSTOPERATIVE MANAGEMENT

In stable instrumentations, no postoperative immobilization with orthosis is necessary, removal of drains (if used) 2-3 days postoperatively (postop), removal of the sutures 14 days postop, clinical and x‑ray controls 3 and 12 months postop or in case of clinical or neurological deterioration.

RESULTS

Numerous studies showed that the use of spinal navigation significantly reduces implant malplacement rates, complications, and revision surgery. Furthermore, intraoperative radiation exposure to the operation team can be reduced by up to 90%.

Perioperative Comparison of Robotic-Assisted Versus Fluoroscopically Guided Minimally Invasive Transforaminal Lumbar Interbody Fusion

OBJECTIVE

Robotic surgical systems have been developed to improve spine surgery accuracy. Studies have found significant reductions in screw revision rates and radiation exposure with robotic assistance compared with open surgery. The aim of the present study was to compare the perioperative outcomes between robot-assisted (RA) and fluoroscopically guided (FG) minimally invasive (MI) transforaminal lumbar interbody fusion (TLIF) performed by a single surgeon.

METHODS

The present retrospective cohort study analyzed all patients with lumbar degenerative disease who had undergone MI-TLIF by a single surgeon from July 2017 to March 2020. One group had undergone FG MI-TLIF and one group had undergone RA MI-TLIF.

RESULTS

Of the 101 patients included in the present study, 52 had undergone RA MI-TLIF and 49, FG MI-TLIF. We found no statistically significant differences in the operative time (RA, 241 ± 69.3 minutes; FG, 246.2 ± 56.3 minutes; P = 0.681). The mean radiation time for the RA group was 32.8 ± 28.8 seconds, and the mean fluoroscopy dose was 31.5 ± 30 mGy. The RA radiation exposure data were compared with similar data for the FG MI-TLIF group in a previous study (59.5 ± 60.4 mGy), with our patients' radiation exposure significantly lower (P = 0.035). The postoperative complications and rates of surgical revision were comparable.

CONCLUSIONS

Our results have demonstrated that RA MI-TLIF provides perioperative outcomes comparable to those with FG MI-TLIF. A reduced radiation dose to the patient was observed with RA compared with FG MI-TLIF. No differences were noted between the RA and FG cohorts in operative times, complication rates, revision rates, or length of stay.

Metal artifacts in intraoperative O-arm CBCT scans

Background

Cone-beam computed tomography (CBCT) has become an increasingly important medical imaging modality in orthopedic operating rooms. Metal implants and related image artifacts create challenges for image quality optimization in CBCT. The purpose of this study was to develop a robust and quantitative method for the comprehensive determination of metal artifacts in novel CBCT applications.

Methods

The image quality of an O-arm CBCT device was assessed with an anthropomorphic pelvis phantom in the presence of metal implants. Three different kilovoltage and two different exposure settings were used to scan the phantom both with and without the presence of metal rods.

Results

The amount of metal artifact was related to the applied CBCT imaging protocol parameters. The size of the artifact was moderate with all imaging settings. The highest applied kilovoltage and exposure level distinctly increased artifact severity.

Conclusions

The developed method offers a practical and robust way to quantify metal artifacts in CBCT. Changes in imaging parameters may have nonlinear effects on image quality which are not anticipated based on physics.

Intraoperative image guidance for cervical spine surgery

Intraoperative image-guidance in spinal surgery has been influenced by various technological developments in imaging science since the early 1990s. The technology has evolved from simple fluoroscopic-based guidance to state-of-art intraoperative computed tomography (iCT)-based navigation systems. Although the intraoperative navigation is more commonly used in thoracolumbar spine surgery, this newer imaging platform has rapidly gained popularity in cervical approaches. The purpose of this manuscript is to address the applications of advanced image-guidance in cervical spine surgery and to describe the use of intraoperative neuro-navigation in surgical planning and execution. In this review, we aim to cover the following surgical techniques: anterior cervical approaches, atlanto-axial fixation, subaxial instrumentation, percutaneous interfacet cage implantation as well as minimally invasive posterior cervical foraminotomy (PCF) and unilateral laminotomy for bilateral decompression. The currently available data suggested that the use of 3D navigation significantly reduces the screw malposition, operative time, mean blood loss, radiation exposure, and complication rates in comparison to the conventional fluoroscopic-guidance. With the advancements in technology and surgical techniques, 3D navigation has potential to replace conventional fluoroscopy completely.

Intraoperative risks of radiation exposure for the surgeon and patient

Intraoperative radiological imaging serves an essential role in many spine surgery procedures. It is critical that patients, staff and physicians have an adequate understanding of the risks and benefits associated with radiation exposure for all involved. In this review, we briefly introduce the current trends associated with intraoperative radiological imaging. With the increased utilization of minimally invasive spine surgery (MIS) techniques, the benefits of intraoperative imaging have become even more important. Less surgical exposure, however, often equates to an increased requirement for intraoperative imaging. Understanding the conventions for radiation measurement, radiological fundamental concepts, along with deterministic or stochastic effects gives a framework for conceptualizing how radiation exposure relates to the risk of various sequela. Additionally, we describe the various options surgeons have for intraoperative imaging modalities including those based on conventional fluoroscopy, computer tomography, and magnetic resonance imaging. We also describe different ways to prevent unnecessary radiation exposure including dose reduction, better education, and use of personal protective equipment (PPE). Finally, we conclude with a reflection on the progress that has been made to limit intraoperative radiation exposure and the promise of future technology and policy.

The effectiveness of a free-standing lead-shield in reducing spine surgeon radiation exposure during intraoperative 3-dimensional imaging

BACKGROUND

CONTEXT Intraoperative three-dimensional (3D) computed tomography (CT) imaging has become increasingly popular in spine surgery. Previous spine surgeon radiation exposure research has focused largely on procedures using fluoroscopy, however, few studies have been performed on the subject since the introduction of the 3D imaging systems. As a result, concerns have re-emerged over surgeon radiation exposure and the effectiveness of operating room (OR) protocols for decreasing workplace radiation. Current radiation safety guidelines require surgeons wear full body protective lead while any type of radiation is being administered during surgery. As a result, local institutions do not allow for the use of free-standing lead shields for sole radiation protection in the operating room. However, there is no data available to demonstrate whether the additional personal lead is required, or if in fact the lead shield alone is sufficient.

PURPOSE

This study investigated the effectiveness of a free-standing lead shield in reducing spine surgeon radiation exposure in the operating room during intraoperative imaging.

STUDY DESIGN/SETTING

A prospective clinical research study at a large, tertiary care center.

PATIENT SAMPLE

Twenty-seven patients undergoing instrumented spinal procedures between June and August 2019.

OUTCOME MEASURES

Fluoroscopy time, total fluoroscopy dose delivered, 3D dose delivered, total 3D spins, number of HD spins, number of standard spins, number of fluoroscopic images, number of spine levels operated on, patient size setting, shield distance from patient, radiation dose in front of shield, radiation dose behind shield.

METHODS

Twenty-seven instrumented spinal procedures using the O-Arm Imaging System (Medtronic, Minneapolis, MN) were observed to determine radiation exposure to a spine surgeon standing behind a lead shield in the OR. Two thermoluminescent dosimeters were used to measure scatter radiation in front of and behind lead shields. Both fluoroscopy and intraoperative CT based radiation exposure was recorded. The dosimeter readings were compared to determine the degree of radiation attenuation by the lead shield. Regression analysis of the exposure values from behind the shield, shield distance from the patient, and radiation dose delivered by the imaging system was utilized to estimate the number of cases required to surpass annual exposure limits. Case numbers were calculated for the highest "worst case" and "average case" exposure values. The safe annual occupation exposure limit determined by the National Council on Radiation Protection is five roentgen equivalent man (rem) or 50,000 microsieverts (μSv).

RESULTS

Average surgeon radiation exposure per case was 0.694 μSv (SD: 0.501, Range: 0.105-2.167) behind the lead shield compared to 14.577 μSv (SD: 9.864, Range: 2.185-44.492) in front of the lead shield. The average radiation dose reduction by the lead shield was 13.962 μSv (SD: 9.49, Range: 2.08-42.72) per case, which is equivalent to an average of 95.65% (SD: 1.71) radiation attenuation by lead shielding. If surgeons stand behind lead shields in the OR, the annual number of 3D image-guided spinal procedures required to surpass exposure limits is 15,479 and 67,060 based on "worst case" and "average case" analyses, respectively.

CONCLUSIONS

Our study demonstrates standing behind intraoperative lead shields is very effective at decreasing radiation exposure to surgeons. Additionally, surgeon radiation doses behind lead shielding fall far below annual exposure limits. Surgeons should not need additional protective equipment when a lead shield is used.

The feasibility of computer-assisted 3D navigation in multiple-level lateral lumbar interbody fusion in combination with posterior instrumentation for adult spinal deformity

OBJECTIVE

The lateral lumbar interbody fusion (LLIF) technique is used to treat many common spinal degenerative pathologies including kyphoscoliosis. The use of spinal navigation for LLIF has not been broadly adopted, especially in adult spinal deformity. The purpose of this study was to evaluate the feasibility as well as the intraoperative and navigation-related complications of computer-assisted 3D navigation (CaN) during multiple-level LLIF for spinal deformity.

METHODS

Retrospective analysis of clinical and operative characteristics was performed for all patients > 18 years of age who underwent multiple-level CaN LLIF combined with posterior instrumentation for adult spinal deformity at the University of Michigan between 2014 and 2020. Intraoperative CaN-related complications, LLIF approach–related postoperative complications, and medical postoperative complications were assessed.

RESULTS

Fifty-nine patients were identified. The mean age was 66.3 years (range 42–83 years) and body mass index was 27.6 kg/m2 (range 18–43 kg/m2). The average coronal Cobb angle was 26.8° (range 3.6°–67.0°) and sagittal vertical axis was 6.3 cm (range −2.3 to 14.7 cm). The average number of LLIF and posterior instrumentation levels were 2.97 cages (range 2–5 cages) and 5.78 levels (range 3–14 levels), respectively. A total of 6 intraoperative complications related to the LLIF stage occurred in 5 patients. Three of these were CaN-related and occurred in 2 patients (3.4%), including 1 misplaced lateral interbody cage (0.6% of 175 total lateral cages placed) requiring intraoperative revision. No patient required a return to the operating room for a misplaced interbody cage. A total of 12 intraoperative complications related to the posterior stage occurred in 11 patients, with 5 being CaN-related and occurring in 4 patients (6.8%). Univariate and multivariate analyses revealed no statistically significant risk factors for intraoperative and CaN-related complications. Transient hip weakness and numbness were found to be in 20.3% and 22.0% of patients, respectively. At the 1-month follow-up, weakness was observed in 3.4% and numbness in 11.9% of patients.

CONCLUSIONS

Use of CaN in multiple-level LLIF in the treatment of adult spinal deformity appears to be a safe and effective technique. The incidence of approach-related complications with CaN was 3.4% and cage placement accuracy was high.

Precise Surgical Treatment of Thoracic Ossification of Ligamentum Flavum Assisted by O-Arm Computer Navigation: A Retrospective Study

OBJECTIVE

O-arm computer navigation-assisted technology (OACNAT) has been widely used in the treatment of thoracic ossification of ligamentum flavum (TOLF) in recent years, but there are few in-depth studies on the safety and effectiveness of this approach. The purpose of this study was to investigate the clinical effect of accurate surgical treatment for TOLF with OACNAT.

METHODS

From January 2010 to January 2018, the clinical data of 64 patients with TOLF who underwent laminectomy and internal fixation in the Third Hospital of Hebei Medical University were retrospectively reviewed. The patients were divided into group A (with OACNAT, n = 33) and group B (without OACNAT, n = 31) according to the application of OACNAT during the operation. The possible operation-related variables, imaging results, and clinical effects were compared between the 2 groups.

RESULTS

In terms of demographics, there were no significant differences between group A and group B in age, sex, body mass index, smoking, drinking, heart disease, hypertension and diabetes (P > 0.05). In terms of operation-related variables, imaging results, and clinical efficacy, there were significant differences in operation time, wound length, postoperative modified Japanese Orthopaedic Association (JOA) score, JOA score improvement rate, accuracy of screw placement, number of intraoperative fluoroscopy procedures, and cerebrospinal fluid leakage between group A and group B (P < 0.05). There were no significant differences in other variables between the 2 groups (P > 0.05). In contrast to group A, in group B, 2 patients had incorrect segmental localization, 3 patients had residual ossified ligamentum flavum after the operation, and 1 patient had postoperative neurologic impairment. On further analysis, compared with group B, group A had a shorter operation time, more accurate screw placement, fewer fluoroscopy procedures, higher JOA score improvement rate, and lower incidence of complications.

CONCLUSIONS

The use of OACNAT accurately located the position, size, shape, and boundary of ossification of the ligamentum flavum during the operation, which could guide accurate decompression and improve the accuracy of pedicle screw placement. This approach not only reduced the incidence of incorrect segmental localization and incomplete or excessive decompression but also reduced the risk of related complications and improved the accuracy, safety, and effectiveness of the operation.

Effect of Instrument Navigation on C-arm Radiation and Time during Spinal Procedures: A Clinical Evaluation

Introduction

As minimally invasive spine surgery gains popularity, a focused effort must be made to reduce intraoperative radiation exposure to levels as low as reasonably achievable. Here, we demonstrate the clinical efficacy of a novel technology to aid in instrument navigation that aims to reduce intraoperative radiation exposure, number of fluoroscopic images, and time required to perform the most radiation intensive portions of a multitude of spinal procedures.

Methods

An internally randomized controlled study was performed over a 1-month period in order to clinically evaluate the effect of the C-arm assisted instrument tracking system, TrackX, on surgeon workflow, time, and radiation emitted. Three surgeons performed multiple spinal procedures on a total of 10 study patients and an additional 3 control patients. The surgeries encompassed minimally invasive spinal techniques and spanned extreme lateral interbody fusion, oblique lumbar interbody fusion, transforaminal lumbar interbody fusion along with percutaneous iliac screw placement, hardware removal, and kyphoplasty. The tasks studied included skin marking, first dilator insertion, localization for hardware placement and hardware removal.

Results

Overall radiation reduction was 83% (P < .0001). Overall reduction in x-rays taken was 78% (P < .0001). Overall time reduction was 81% (P = .0003). Statistical significance held for each surgeon studied and for nearly every procedure type. In these 10 study procedures, over 2 hours of overall operating room time was saved, all while requiring negligible set up time and no system calibration or supplementary x-rays to be taken. There were no adverse outcomes for any study patient, and there was no case where TrackX was not able to successfully complete a given portion of a procedure.

Conclusions

TrackX instrument navigation is a clinically efficacious and accurate instrument tracking modality. This is the first instrument navigational technology that reduces radiation exposure and images required to complete a procedure while decreasing operative time. TrackX thus allows increased surgical efficiency while increasing operative efficiency and improving intraoperative safety.

Level of Evidence

2.

Customized anterior craniocervical reconstruction via a modified high-cervical retropharyngeal approach following resection of a spinal tumor involving C1-2/C1-3

OBJECTIVE

The surgical treatment of an upper cervical spinal tumor (UCST) at C1-2/C1-3 is challenging due to anterior exposure and reconstruction. Limited information has been published concerning the effective approach and reconstruction for an anterior procedure after C1-2/C1-3 UCST resection. The authors attempted to introduce a novel, customized, anterior craniocervical reconstruction between the occipital condyles and inferior vertebrae through a modified high-cervical retropharyngeal approach (mHCRA) in addressing C1-2/C1-3 spinal tumors.

METHODS

Seven consecutive patients underwent 2-stage UCST resection with circumferential reconstruction. Posterior decompression and occiput-cervical instrumentation was conducted at the stage 1 operation, and anterior craniocervical reconstruction using a 3D-printed implant was performed between the occipital condyles and inferior vertebrae via an mHCRA. The clinical characteristics, perioperative complications, and radiological outcomes were reviewed, and the rationale for anterior craniocervical reconstruction was also clarified.

RESULTS

The mean age of the 7 patients in the study was 47.6 ± 19.0 years (range 12-72 years) when referred to the authors' center. Six patients (85.7%) had recurrent tumor status, and the interval from primary to recurrence status was 53.0 ± 33.7 months (range 24-105 months). Four patients (57.1%) were diagnosed with a spinal tumor involving C1-3, and 3 patients (42.9%) with a C1-2 tumor. For the anterior procedure, the mean surgical duration and average blood loss were 4.1 ± 0.9 hours (range 3.0-6.0 hours) and 558.3 ± 400.5 ml (range 100-1300 ml), respectively. No severe perioperative complications occurred, except 1 patient with transient dysphagia. The mean pre- and postoperative visual analog scale scores were 8.0 ± 0.8 (range 7-9) and 2.4 ± 0.5 (range 2.0-3.0; p < 0.001), respectively, and the mean improvement rate of cervical spinal cord function was 54.7% ± 13.8% (range 42.9%-83.3%) based on the modified Japanese Orthopaedic Association scale score (p < 0.001). Circumferential instrumentation was in good position and no evidence of disease was found at the mean follow-up of 14.8 months (range 7.3-24.2 months).

CONCLUSIONS

The mHCRA provides optimal access to the surgical field at the C0-3 level. Customized anterior craniocervical fixation between the occipital condyles and inferior vertebrae can be feasible and effective in managing anterior reconstruction after UCST resection.

[Relevance of spinal navigation in reconstructive surgery of the cervical spine]

BACKGROUND

Spinal navigation has made significant advances in the last two decades. After initial experiences with pedicle screws in the thoracic and lumbar spine, technological improvements have resulted in their increased application in the cervical spine. Instrumentation techniques like cervical pedicle screws, lateral mass screws in C1 and transarticular screws C1/C2 have become standard due to the application of image guidance.

TECHNIQUE

Different navigation techniques can be distinguished based on the type of imaging. In the cervical spine, the preoperative computer tomography (CT) scan that requires intraoperative matching is still the standard of care due to the high image quality. 3D fluoroscopy navigation techniques are currently widely used in the lumbar spine, but the reduced image quality obviates the application in the more sophisticated cervical anatomy or the cervicothoracic region. The future availability of intraoperative CT scans (iCT) combines the advantages of high image quality with those of intraoperative image acquisition. This will lead to a wider use of image guidance in the cervical spine and will enable the surgeon to apply minimally invasive techniques with higher accuracy.

APPLICATION

The successful application of spinal navigation is based on the technical knowledge of navigation systems and its exercise in daily routine. Only the sufficient experience of the clinical staff makes it possible to standardize operational procedures to increase patient safety, reduce radiation dose and shorten operation time.

Evaluation of surgeon and patient radiation exposure by imaging technology in patients undergoing thoracolumbar fusion: systematic review of the literature

BACKGROUND CONTEXT

Minimally invasive spine techniques are becoming increasingly popular owing to their ability to reduce operative morbidity and recovery times. The downside to these new procedures is their need for intraoperative radiation guidance.

PURPOSE

To establish which technologies provide the lowest radiation exposure to both patient and surgeon.

STUDY DESIGN/SETTING

Systematic review OUTCOME MEASURES: Average intraoperative radiation exposure (in mSv per screw placed) to surgeon and patient. Average fluoroscopy time per screw placed.

METHODS

We reviewed the available English medical literature to identify all articles reporting patient and/or surgeon radiation exposure in patients undergoing image-guided thoracolumbar instrumentation. Quantitative meta-analysis was performed for studies providing radiation exposure or fluoroscopy use per screw placed to determine which navigation modality was associated with the lowest intraoperative radiation exposure. Values on meta-analysis were reported as mean ± standard deviation.

RESULTS

We identified 4956 unique articles, of which 85 met inclusion/exclusion criteria. Forty-one articles were included in the meta-analysis. Patient radiation exposure per screw placed for each modality was: conventional fluoroscopy without navigation (0.26±0.38 mSv), conventional fluoroscopy with pre-operative CT-based navigation (0.027±0.010 mSv), intraoperative CT-based navigation (1.20±0.91 mSv), and robot-assisted instrumentation (0.04±0.30 mSv). Values for fluoroscopy used per screw were: conventional fluoroscopy without navigation (11.1±9.0 seconds), conventional fluoroscopy with navigation (7.20±3.93 s), 3D fluoroscopy (16.2±9.6 s), intraoperative CT-based navigation (19.96±17.09 s), and robot-assistance (20.07±17.22 s). Surgeon dose per screw: conventional fluoroscopy without navigation (6.0±7.9 × 10^-3 mSv), conventional fluoroscopy with navigation (1.8±2.5 × 10^-3 mSv), 3D Fluoroscopy (0.3±1.9 × 10^-3 mSv), intraoperative CT-based navigation (0±0 mSv), and robot-assisted instrumentation (2.0±4.0 × 10^-3 mSv).

CONCLUSION

All image guidance modalities are associated with surgeon radiation exposures well below current safety limits. Intraoperative CT-based (iCT) navigation produces the lowest radiation exposure to surgeon albeit at the cost of increased radiation exposure to the patient relative to conventional fluoroscopy-based methods.

[Spinal navigation for posterior cervical and cervicothoracic instrumentation]

OBJECTIVE

Safe placement of posterior cervical or high-thoracic pedicle screws, transarticular screws C1/2, translaminar screws C2 or cervical lateral mass screws under the guidance of spinal navigation.

INDICATIONS

All posterior cervical and cervicothoracic instrumentation with screws: instabilities and deformities of rheumatoid, traumatic, neoplastic, infectious, iatrogenic or congenital origin; multilevel cervical spinal stenosis with degenerative instability or kyphosis of the affected spinal segment.

CONTRAINDICATIONS

There are no absolute contraindications.

SURGICAL TECHNIQUE

Prone position on a gel mattress, rigid head fixation, e.g., with Mayfield tongs; if appropriate, closed reduction under lateral image intensification; midline posterior surgical approach at the level of the segments to be instrumented; if necessary, open reduction; insertion of the cervical/upper thoracic screws under the guidance of spinal navigation; if necessary, posterior decompression; instrumentation longitudinal rods; if a fusion is to be obtained, decortication of the posterior bone elements with a high-speed burr and onlay of cancellous bone or bone substitutes.

POSTOPERATIVE MANAGEMENT

In stable instrumentation, no postoperative immobilization with cervical collar is necessary. Drain removal on postoperative day 2-3, suture removal on postoperative day 14, clinical and x‑ray control 3 and 12 months after surgery or in case of clinical or neurological deterioration.

RESULTS

Numerous studies showed that the use of spinal navigation reduces implant malplacement rates significantly. Furthermore, it allows a reduction of the radiation dose for the operation team up to 90%.

Use of the Airo mobile intraoperative CT system versus the O-arm for transpedicular screw fixation in the thoracic and lumbar spine: a retrospective cohort study of 263 patients

OBJECTIVE

Navigation-enabling technology such as 3D-platform (O-arm) or intraoperative mobile CT (iCT-Airo) systems for use in spinal surgery has considerably improved accuracy over that of traditional fluoroscopy-guided techniques during pedicular screw positioning. In this study, the authors compared 2 intraoperative imaging systems with navigation, available in their neurosurgical unit, in terms of the accuracy they provided for transpedicular screw fixation in the thoracic and lumbar spine.

METHODS

The authors performed a retrospective analysis of clinical and surgical data of 263 consecutive patients who underwent thoracic and lumbar spine screw placement in the same center. Data on 97 patients who underwent surgery with iCT-Airo navigation (iCT-Airo group) and 166 with O-arm navigation (O-arm group) were analyzed. Most patients underwent surgery for a degenerative or traumatic condition that involved thoracic and lumbar pedicle screw fixation using an open or percutaneous technique. The primary endpoint was the proportion of patients with at least 1 screw not correctly positioned according to the last intraoperative image. Secondary endpoints were the proportion of screws that were repositioned during surgery, the proportion of patients with a postoperative complication related to screw malposition, surgical time, and radiation exposure. A blinded radiologist graded screw positions in the last intraoperative image according to the Heary classification (grade 1–3 screws were considered correctly placed).

RESULTS

A total of 1361 screws placed in 97 patients in the iCT-Airo group (503 screws) and in 166 in the O-arm group (858 screws) were graded. Of those screws, 3 (0.6%) in the iCT-Airo group and 4 (0.5%) in the O-arm group were misplaced. No statistically significant difference in final accuracy between these 2 groups or in the subpopulation of patients who underwent percutaneous surgery was found. Three patients in the iCT-Airo group (3.1%, 95% CI 0%–6.9%) and 3 in the O-arm group (1.8%, 95% CI 0%–4.0%) had a misplaced screw (Heary grade 4 or 5). Seven (1.4%) screws in the iCT-Airo group and 37 (4.3%) in the O-arm group were repositioned intraoperatively (p = 0.003). One patient in the iCT-Airo group and 2 in the O-arm group experienced postoperative neurological deficits related to hardware malposition. The mean surgical times in both groups were similar (276 [iCT-Airo] and 279 [O-arm] minutes). The mean exposure to radiation in the iCT-Airo group was significantly lower than that in the O-arm group (15.82 vs 19.12 mSv, respectively; p = 0.02).

CONCLUSIONS

Introduction of a mobile CT scanner reduced the rate of screw repositioning, which enhanced patient safety and diminished radiation exposure for patients, but it did not improve overall accuracy compared to that of a mobile 3D platform.

[Radiation protection measures: Implications on the design of neurosurgery operating rooms]

OBJECTIVE

To describe pros and cons of some radiation protection measures and the implications on the design of a neurosurgery operating room.

MATERIAL AND METHODS

Concurring with the acquisition and use of an O-arm device, a structural remodeling of our neurosurgery operating room was carried out. The theater was enlarged, the shielding was reinforced and a foldable leaded screen was installed inside the operating room. Radiation doses were measured in front of and behind the screen.

RESULTS

The screen provides whole-body radiation protection for all the personnel inside the theater (effective dose <5μSv at 2,5 m from the gantry per O-arm exploration; 0,0μSv received behind the screen per O-arm exploration; and undetectable cumulative annual radiation dose behind the screen), obviates the need for leaded aprons and personal dosimeters, and minimizes the circulation of personnel. Enlarging the size of the operating room allows storing the equipment inside and minimizes the risk of collision and contamination. Rectangular rooms provide greater distance from the source of radiation.

CONCLUSION

Floor, ceiling and walls shielding, a rectangular-shaped and large enough theater, the presence of a foldable leaded screen, and the security systems precluding an unexpected irruption into the operating room during irradiation are relevant issues to consider when designing a neurosurgery operating theater.

Comparison Perioperative Factors During Minimally Invasive Pre-Psoas Lateral Interbody Fusion of the Lumbar Spine Using Either Navigation or Conventional Fluoroscopy

STUDY DESIGN

Retrospective clinical study.

OBJECTIVES

The aim of this study was to compare intraoperative conditions and clinical results of patients undergoing pre-psoas oblique lateral interbody fusion (OLIF) using navigation or conventional fluoroscopy (C-ARM) techniques.

METHODS

Forty-two patients (22 patients by navigation and 20 by fluoroscopy) underwent the OLIF procedure at 2 medical centers, and records were reviewed. Clinical data was collected and compared between the 2 groups. Patients were followed-up with a range of 6 to 24 months.

RESULTS

There were no significant differences on demographic data between groups. The navigation group had zero radiation exposure (RE) to the surgeon and radiation time compared to the C-ARM group, with total RE of 44.59 ± 26.65 mGy and radiation time of 88.30 ± 58.28 seconds (P < .05). The RE to the patient was significantly lower in the O-ARM group (9.38 mGy) compared to the C-ARM group (44.59 ± 26.65 mGy). Operating room time was slightly longer in the navigation group (2.49 ± 1.35 hours) compared to the C-ARM group (2.30 ± 1.17 hours; P > .05), although not statistically significant. No differences were found in estimated blood loss, length of hospitalization, surgery-related complications, and outcome scores with an average of 8-month follow-up.

CONCLUSIONS

Compared with C-ARM techniques, using navigation can eliminate RE to surgeon and decrease RE to the patient, and it had no significant effect on operating time, estimated blood loss, length of hospitalization, or perioperative complications in the patients with OLIF procedure. This study shows that navigation is a safe alternative to fluoroscopy during the OLIF procedure in the treatment of degenerative lumbar conditions.

The Great Unknown-A systematic literature review about risk associated with intraoperative imaging during orthopaedic surgeries

INTRODUCTION

Modern techniques in orthopaedic surgery using minimally invasive procedures, and increased use of fluoroscopic imaging present a potential increased risk to surgeons due to ionizing radiation exposure. This article is a systematic review of recent literature on radiation exposure of orthopaedic surgeons.

MATERIALS AND METHODS

Pubmed and Cochrane searches were performed on intraoperative radiation exposure covering English and German articles published between 1.1.2000 and 11.8.2014. Inclusion criteria were clinical studies and systematic literature reviews focusing on radiation exposure of orthopaedic surgeons during surgical procedures of the musculoskeletal system reporting either effective dose (whole body) or equivalent dose at the organ level. All included articles were reviewed with focus on the surgical specialty, the procedure type, the imaging system used, the radiation measurement method, the fluoroscopy time, the radiation exposure, the use of radiation protection, and any references to specific safety guidelines.

RESULTS

Thirty-four eligible publications were identified. However, the lack of well-designed studies focusing on radiation exposure of surgeons prevents pooling of data. Highest exposure and subsequent equivalent doses were reported from spinal surgery (up to 4.8mSv of equivalent dose to the hand) and intramedullary nailing (up to 0.142mSV of equivalent dose to the thyroid). Radiation exposure was reduced by 96.9% and 94.2% when wearing a thyroid collar and a lead apron.

CONCLUSIONS

With the increasing use of intraoperative imaging, there is a growing need for radiation awareness by the operating surgeon. Strict adherence to radiation protection should be enforced to protect in-training surgeons. Strategies to reduce exposure include C-arm position, distance, protective wear, and new imaging technologies. Radiation exposure is harmful and action should be taken to minimize exposure.

Radiation exposure and reduction in the operating room: Perspectives and future directions in spine surgery

Intraoperative imaging is vital for accurate placement of instrumentation in spine surgery. However, the use of biplanar fluoroscopy and other intraoperative imaging modalities is associated with the risk of significant radiation exposure in the patient, surgeon, and surgical staff. Radiation exposure in the form of ionizing radiation can lead to cellular damage via the induction of DNA lesions and the production of reactive oxygen species. These effects often result in cell death or genomic instability, leading to various radiation-associated pathologies including an increased risk of malignancy. In attempts to reduce radiation-associated health risks, radiation safety has become an important topic in the medical field. All practitioners, regardless of practice setting, can practice radiation safety techniques including shielding and distance to reduce radiation exposure. Additionally, optimization of fluoroscopic settings and techniques can be used as an effective method of radiation dose reduction. New imaging modalities and spinal navigation systems have also been developed in an effort to replace conventional fluoroscopy and reduce radiation doses. These modalities include Isocentric Three-Dimensional C-Arms, O-Arms, and intraoperative magnetic resonance imaging. While this influx of new technology has advanced radiation safety within the field of spine surgery, more work is still required to overcome specific limitations involving increased costs and inadequate training.

Significant reduction of fluoroscopy repetition with lumbar localization system in minimally invasive spine surgery: A prospective study

The conventional location methods for minimally invasive spinal surgery (MISS) were mainly based on repeated fluoroscopy in a trial-and-error manner preoperatively and intraoperatively. Localization system mainly consisted of preoperative applied radiopaque frame and intraoperative guiding device, which has the potential to minimize fluoroscopy repetition in MISS. The study aimed to evaluate the efficacy of a novel lumbar localization system in reducing radiation exposure to patients.Included patients underwent minimally invasive transforaminal lumbar interbody fusion (MISTLIF) or percutaneous transforaminal endoscopic discectomy (PTED). Patients treated with novel localization system were regarded as Group A, and patients treated without novel localization system were regarded as Group B.For PTED, The estimated effective dose was 0.41 ± 0.13 mSv in Group A and 0.57 ± 0.14 mSv in Group B (P < .001); the fluoroscopy exposure time of PTED was 22.18 ± 7.30 seconds in Group A and 30.53 ± 7.56 seconds in Group B (P < .001); The estimated cancer risk of radiation exposure was 22.68 ± 7.38 (10) in Group A and 31.20 ± 7.96 (10) in Group B (P < .001). For MISTLIF, the estimated effective dose was 0.45 ± 0.09 mSv in Group A and 0.58 ± 0.09 mSv in Group B (P < .001); The fluoroscopy exposure time was 25.41 ± 5.52 seconds in Group A and 32.82 ± 5.03 seconds in Group B (P < .001); The estimated cancer risk was 24.90 ± 5.15 (10) in Group A and 31.96 ± 5.04 (10) in Group B (P < .001). There were also significant differences in localization time and operation time between the 2 groups either for MISTLIF or PTED.The lumbar localization system could be a potential protection strategy for minimizing radiation hazards.

Preoperative Magnetic Resonance and Intraoperative Computed Tomography Fusion for Real-Time Neuronavigation in Intramedullary Lesion Surgery

BACKGROUND

Image-guided surgery techniques in spinal surgery are usually based upon fluoroscopy or computed tomography (CT) scan, which allow for a real-time navigation of bony structures, though not of neural structures and soft tissue remains.

OBJECTIVE

To verify the effectiveness and efficacy of a novel technique of imaging merging between preoperative magnetic resonance imaging (MRI) and intraoperative CT scan during removal of intramedullary lesions.

METHODS

Ten consecutive patients were treated for intramedullary lesions using a navigation system aid. Preoperative contrast-enhanced MRI was merged in the navigation software, with an intraoperative CT acquisition, performed using the O-arm TM system (Medtronic Sofamor Danek, Minneapolis, Minnesota). Dosimetric and timing data were also acquired for each patient.

RESULTS

The fusion process was achieved in all cases and was uneventful. The merged imaging information was useful in all cases for defining the exact area of laminectomy, dural opening, and the eventual extension of cordotomy, without requiring exposition corrections. The radiation dose for the patients was 0.78 mSv. Using the authors' protocol, it was possible to merge a preoperative MRI with navigation based on intraoperative CT scanning in all cases. Information gained with this technique was useful during the different surgical steps. However, there were some drawbacks, such as the merging process, which still remains partially manual.

CONCLUSION

In this initial experience, MRI and CT merging and its feasibility were tested, and we appreciated its safety, precision, and ease.

Internally Randomized Control Trial of Radiation Exposure Using Ultra-low Radiation Imaging Versus Traditional C-arm Fluoroscopy for Patients Undergoing Single-level Minimally Invasive Transforaminal Lumbar Interbody Fusion

STUDY DESIGN

Randomized controlled trial.

OBJECTIVE

To compare radiation exposure between ultra-low radiation imaging (ULRI) with image enhancement and standard-dose fluoroscopy for patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).

SUMMARY OF BACKGROUND DATA

Although the benefits of MIS are lauded by many, there is a significant amount of radiation exposure to surgeon and operating room personnel. Our goal with this work was to see if by using ultra-low dose radiation settings coupled with image enhancement, this exposure could be minimized.

METHODS

An institutional review board approved, prospective, internally randomized controlled trial was performed comparing ultra-low dose settings coupled with image enhancement software to conventional fluoroscopic imaging. In this study, each patient served as their own control, randomly assigning one side of MIS-TLIF for cannulation and K-wire placement using each imaging modality. Further, the case was also randomly divided into screw placement and cage placement/final images to allow further comparisons amongst patients. Radiation production from the C-arm fluoroscope and radiation exposure to all operating room personnel were recorded.

RESULTS

Twenty-four patients were randomly assigned to undergo a single level MIS-TLIF. In no case was low radiation imaging abandoned, and no patient had a neurologic decline or required hardware repositioning. Everyone in the operating room-the physician, scrub nurse, circulator, and anesthesiologist-all benefited with 61.6% to 83.5% reduction in radiation exposure during cannulation and K-wire placement to screw insertion aided by ULRI. In every case but the anesthesiologist dose, this was statistically significant (P < 0.05). This benefit required no additional time (P = 0.78 for K-wire placement).

CONCLUSION

ULRI, when aided by image enhancement software, affords the ability for all parties in the operating room to substantially decrease their radiation exposure compared with standard-dose C-arm fluoroscopy without adding additional time or an increased complication rate.

LEVEL OF EVIDENCE

2.

Use of 3D CT-based navigation in minimally invasive lateral lumbar interbody fusion

OBJECTIVE

Lateral lumbar interbody fusion (LLIF) is an increasingly popular technique used to treat degenerative lumbar disease. The technique of using an intraoperative cone-beam CT (iCBCT) and an image-guided navigation system (IGNS) for LLIF cage placement has been previously described. However, other than a small feasibility study, there has been no clinical study evaluating its accuracy or safety. Therefore, the purpose of this study was to evaluate the accuracy and safety of image-guided spinal navigation in LLIF.

METHODS

An analysis of a prospectively acquired database was performed. Thirty-one consecutive patients were identified. Accuracy was initially determined by comparison of the planned trajectory of the IGNS with post–cage placement intraoperative fluoroscopy. Accuracy was subsequently confirmed by postprocedural CT and/or radiography. Cage placement was graded based on a previously described system separating the disc space into quarters.

RESULTS

The mean patient age was 63.9 years. A total of 66 spinal levels were treated, with a mean of 2.1 levels (range 1–4) treated per patient. Cage placement was noted to be accurate using IGNS in each case, as confirmed with intraoperative fluoroscopy and postoperative imaging. Sixty-four (97%) cages were placed within Quarters 1 to 2 or 2 to 3, indicating placement of the cage in the anterior or middle portions of the disc space. There were no instances of misguidance by IGNS. There was 1 significant approach-related complication (psoas muscle abscess) that required intervention, and 8 patients with transient, mild thigh paresthesias or weakness.

CONCLUSIONS

LLIF can be safely and accurately performed utilizing iCBCT and IGNS. Accuracy is acceptable for multilevel procedures.

Redirecting pedicle screws: a revision spinal fusion strategy using three-dimensional image guidance

BACKGROUND

Pedicle screws are a preferred method for spinal fixation because of their three-column support and rigid posterior stabilization. The purpose of this study was to evaluate the outcome of patients requiring pedicle screw redirection, and to describe a technique using cone-beam computed tomography (cbCT).

METHODS

A retrospective review of 30 patients undergoing revision spinal fusion with redirection of pedicle screws was performed. Fifty pedicle screws were redirected in these patients using cbCT-based 3D image guidance. They were graded pre- and post-operatively using an established grading system.

RESULTS

No complications occurred in this study as a result of redirection. No pedicle breach was noted in all of the redirected pedicle screws.

CONCLUSION

Redirection of misplaced pedicle screws using cbCT-based 3D image guidance seems to be safe and accurate in our experience. Further studies are needed to establish its safety, accuracy, fusion rate, and clinical outcome compared with other methods. Copyright © 2016 John Wiley & Sons, Ltd.

Radiological Protection in Cone Beam Computed Tomography (CBCT). ICRP Publication 129

The objective of this publication is to provide guidance on radiological protection in the new technology of cone beam computed tomography (CBCT). Publications 87 and 102 dealt with patient dose management in computed tomography (CT) and multi-detector CT. The new applications of CBCT and the associated radiological protection issues are substantially different from those of conventional CT. The perception that CBCT involves lower doses was only true in initial applications. CBCT is now used widely by specialists who have little or no training in radiological protection. This publication provides recommendations on radiation dose management directed at different stakeholders, and covers principles of radiological protection, training, and quality assurance aspects. Advice on appropriate use of CBCT needs to be made widely available. Advice on optimisation of protection when using CBCT equipment needs to be strengthened, particularly with respect to the use of newer features of the equipment. Manufacturers should standardise radiation dose displays on CBCT equipment to assist users in optimisation of protection and comparisons of performance. Additional challenges to radiological protection are introduced when CBCT-capable equipment is used for both fluoroscopy and tomography during the same procedure. Standardised methods need to be established for tracking and reporting of patient radiation doses from these procedures. The recommendations provided in this publication may evolve in the future as CBCT equipment and applications evolve. As with previous ICRP publications, the Commission hopes that imaging professionals, medical physicists, and manufacturers will use the guidelines and recommendations provided in this publication for implementation of the Commission's principle of optimisation of protection of patients and medical workers, with the objective of keeping exposures as low as reasonably achievable, taking into account economic and societal factors, and consistent with achieving the necessary medical outcomes.

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

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.

The use of intraoperative navigation for complex upper cervical spine surgery

Imaging guidance using intraoperative CT (O-arm surgical imaging system) combined with a navigation system has been shown to increase accuracy in the placement of spinal instrumentation. The authors describe 4 complex upper cervical spine cases in which the O-arm combined with the StealthStation surgical navigation system was used to accurately place occipital screws, C-1 screws anteriorly and posteriorly, C-2 lateral mass screws, and pedicle screws in C-6. This combination was also used to navigate through complex bony anatomy altered by tumor growth and bony overgrowth. The 4 cases presented are: 1) a developmental deformity case in which the C-1 lateral mass was in the center of the cervical canal causing cord compression; 2) a case of odontoid compression of the spinal cord requiring an odontoidectomy in a patient with cerebral palsy; 3) a case of an en bloc resection of a C2-3 chordoma with instrumentation from the occiput to C-6 and placement of C-1 lateral mass screws anteriorly and posteriorly; and 4) a case of repeat surgery for a non-union at C1-2 with distortion of the anatomy and overgrowth of the bony structure at C-2.

Thoracolumbar instrumentation with CT-guided navigation (O-arm) in 270 consecutive patients: accuracy rates and lessons learned

Object

Thoracolumbar instrumentation has experienced a dramatic increase in utilization over the last 2 decades. However, pedicle screw fixation remains a challenging undertaking, with suboptimal placement contributing to postoperative pain, neurological deficit, vascular complications, and return to the operating suite. Image-guided spinal surgery has substantially improved the accuracy rates for these procedures. However, it is not without technical challenges and a learning curve for novice operators. The authors present their experience with the O-arm intraoperative imaging system and share the lessons they learned over nearly 5 years.

Methods

The authors performed a retrospective chart review of 270 consecutive patients who underwent thoracolumbar pedicle screw fixation utilizing the O-arm imaging system in conjunction with StealthStation navigation between April 2009 and September 2013 at a single tertiary care center; 266 of the patients underwent CT scanning on postoperative Day 1 to evaluate hardware placement. The CT scans were interpreted prospectively by 3 neuroradiologists as part of standard work flow and retrospectively by 2 neurosurgeons and a senior resident. Pedicle screws were evaluated for breaches according to the 3-tier classification proposed by Mirza et al.

Results

Of 270 patients, 266 (98.5%) were included in the final analysis based on the presence of a postoperative CT scan. Overall, 1651 pedicle screws were placed in 266 patients and yielded a 5.3% breach rate; 213 thoracic and 1438 lumbosacral pedicle screws were inserted with 6.6% and 5.1% breach rates, respectively. Of the 87 suboptimally placed screws, there were 13 Grade 1, 16 Grade 2, and 12 Grade 3 misses as well as 46 anterolateral or “tip-out” perforations at L-5. Four patients (1.5%) required a return to the operating room for pedicle screw revision, 2 of whom experienced transient radicular symptoms and 2 remained asymptomatic. Interestingly, the pedicle breach rate was higher than anticipated at 13.21% for the 30 patients over the initial 6-month period with the O-arm. After certain modifications to the authors' technique, the subsequent 30 patients experienced a statistically significant decrease in breach rate at 5.6% (p = 0.014).

Conclusions

Image-guided spinal surgery can be a great option in the operating room and provides high pedicle screw accuracy rates. With numerous systems commercially available, it is important to develop a systematic approach regardless of the technology in question. There is a learning curve for surgeons unfamiliar with image guidance that should be recognized and appreciated when transitioning to navigation-assisted spinal surgery. In fact, the authors' experience with a large patient cohort suggests that this learning curve may be more significant than previously reported.