Surgeon radiation exposure in cone beam computed tomography-based, image-guided spinal surgery

Pedicle Screw Placement Aided by C-Arm Fluoroscopy: A "Nevermore without" Technology to Pursue Optimal Spine Fixation

The surgical technique and the intraoperative technology that support spinal pedicle screw placement have consistently evolved over the past decades to decrease the misplacement rate of pedicle screws. We retrospectively evaluated our case series by analyzing the period 2016-2020. Patients undergoing pedicle screw fixation for cervical, thoracic, or lumbar spine degenerative diseases have been included. Surgery was carried out with the aid of intraoperative 3D C-arm fluoroscopy to assess and optimize screw placement and/or correct possible mispositioning. Each patient underwent a postoperative CT scan. Our aim was to evaluate the safety and accuracy of pedicle screw placement and estimate the variation in mispositioning rates. We carried out 329 surgical procedures, as follows: 70 cervical, 78 thoracic spine, and 181 lumbar spine surgeries. An excellent overall pedicle screw positioning was obtained, with slight differences between the cervical (98.6%), thoracic (100%), and lumbar (98.9%) tracts. Accordingly, only three patients required a revision surgery owing to mispositioning (0.91%). In particular, intraoperative C-arm fluoroscopy significatively improved the accuracy of thoracic screw positioning, as shown by postoperative CT scans. Our experience proves the crucial role of intraoperative C-arm fluoroscopy in pursuing optimal technical results and improving patient outcomes at follow-up.

The Clinical Impact of Image Guidance and Robotics in Spinal Surgery: A Review of Safety, Accuracy, Efficiency, and Complication Reduction

Image guidance (IG) and robotic-assisted (RA) surgery are modern technological advancements that have provided novel ways to perform precise and accurate spinal surgery. These innovations supply real-time, three-dimensional imaging information to aid in instrumentation, decompression, and implant placement. Although nothing can replace the knowledge and expertise of an experienced spine surgeon, these platforms do have the potential to supplement the individual surgeon's capabilities. Specific advantages include more precise pedicle screw placement, minimally invasive surgery with less reliance on intraoperative fluoroscopy, and lower radiation exposure to the surgeon and staff. As these technologies have become more widely adopted over the years, novel uses such as tumor resection have been explored. Disadvantages include the cost of implementing IG and robotics platforms, the initial learning curve for both the surgeon and the staff, and increased patient radiation exposure in scoliosis surgery. Also, given the relatively recent transition of many procedures from inpatient settings to ambulatory surgery centers, access to current devices may be cost prohibitive and not as readily available at some centers. Regarding patient-related outcomes, much further research is warranted. The short-term benefits of minimally invasive surgery often bolster the perioperative and early postoperative outcomes in many retrospective studies on IG and RA surgery. Randomized controlled trials limiting such confounding factors are warranted to definitively show potential independent improvements in patient-related outcomes specifically attributable to IG and RA alone. Nonetheless, irrespective of these current unknowns, it is clear that these technologies have changed the field and the practice of spine surgery. Surgeons should be familiar with the potential benefits and tradeoffs of these platforms when considering adopting IG and robotics in their practices.

Navigation and Robotic-Assisted Single-Position Prone Lateral Lumbar Interbody Fusion: Technique, Feasibility, Safety, and Case Series

BACKGROUND

Single-position prone lateral interbody fusion is a recently introduced technical modification of the minimally invasive retroperitoneal transpsoas approach for lateral lumbar interbody fusion (LLIF). Several technical descriptions of single-position prone LLIF have been published with traditional fluoroscopy for guidance. However, there has been no investigation of either three-dimensional computed tomography-based navigation for prone LLIF or integration with robotic assistance platforms with the prone lateral technique. This study evaluated the feasibility and safety of spinal navigation and robotic assistance for single-position prone LLIF.

METHODS

Retrospective review of medical records and a prospectively acquired database for a single center was performed to examine immediate and 30-day clinical and radiographic outcomes for consecutive patients undergoing single-position prone LLIF with spinal navigation and/or robotic assistance.

RESULTS

Nine patients were treated, 4 women and 5 men. Mean age was 65.4 years (range, 46-75 years), and body mass index was 30.2 kg/m² (range, 24-38 kg/m²). The most common surgical indication was adjacent segment disease (44.4%), followed by pseudarthrosis (22.2%), spondylolisthesis (11.1%), degenerative disc disease (11.1%), and recurrent stenosis (11.1%). Postoperative approach-related complications included pain-limited bilateral hip flexor weakness (4/5) and pain-limited left knee extension weakness (4/5) in 1 patient (11.1%) and right lateral thigh numbness and dysesthesia in 1 patient (11.1%). All cages were placed within quarters 2-3, signifying the middle portion of the disc space. There were no instances of misguidance by navigation.

CONCLUSIONS

Integration of spinal navigation and robotic assistance appears feasible, accurate, and safe as an alternative to fluoroscopic guidance for single-position LLIF.

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.

Intraoperative image guidance for lateral position surgery

Recent advances in minimally invasive spine surgery techniques have precipitated the popularity of lateral position spine surgery, such as lateral lumbar interbody fusion (LLIF) and oblique lumbar interbody fusion (OLIF). Lateral position surgery offers a unique, minimally invasive approach to the lumbar spine that allows for preservation of anterior and posterior spinal elements. Traditionally, surgeons have relied upon fluoroscopy for triangulation and implant placement. Over the last decade, intraoperative 3-dimensional navigation (ION) has risen to the forefront of innovation in LLIF and OLIF. This technology utilizes intra-operative advanced imaging, such as comminuted tomography (CT), to map the patient’s 3D anatomy and allows the surgeon to accurately visualize instruments and implants in spatial relationship to the patient’s anatomy in real time. ION has the potential to improve accuracy during instrumentation, decrease operating room times, lower radiation exposure to the surgeon and staff, and increase feasibility of single-position surgery during which the spine is instrumented both laterally and posteriorly while the patient remains in the lateral decubitus position. Despite the advantages of ION, the intra-operative radiation exposure risk to patients is controversial. Future directions include continued innovation in ultra low radiation imaging (ULRI) techniques and image enhancement technology and in uses of robot-assisted navigation in single-position spine surgery.

Device profile of the XVision-spine (XVS) augmented-reality surgical navigation system: overview of its safety and efficacy

Introduction: The field of augmented reality mediated spine surgery is growing rapidly and holds great promise for improving surgical capabilities and patient outcomes. Augmented reality can assist with complex or atypical cases involving challenging anatomy. As neuronavigation evolves, fundamental technical limitations remain in line-of-sight interruption and operator attention shift, which this novel augmented reality technology helps to address.Areas covered: XVision is a recently FDA-approved head mounted display for intraoperative neuronavigation, compatible with all current conventional pedicle screw technology. The device is a wireless, customizable headset with an integrated surgical tracking system and transparent retinal display. This review discusses the available literature on the safety and efficacy of XVision, as well as the current state of augmented reality technology in spine surgery.Expert opinion: Augmented-reality spine surgery is an emerging technology that may increase precision, efficiency, and safety as well as decrease radiation exposure of manual and robotic computer-navigated pedicle screw insertion techniques. The initial clinical experience with XVision has shown good outcomes and it has received positive operator feedback. Now that initial clinical safety and efficacy has been demonstrated, ongoing experience must be studied to empirically validate this technology and generate further innovation in this rapidly evolving field.

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.

Conventional versus stereotactic image guided pedicle screw placement during spinal deformity correction: a retrospective propensity score-matched study of a national longitudinal database

PURPOSE/AIM

To compare complications, readmissions, revisions, and payments between navigated and conventional pedicle screw fixation for treatment of spine deformity.

METHODS

The Thomson Reuters MarketScan national longitudinal database was used to identify patients undergoing osteotomy, posterior instrumentation, and fusion for treatment of spinal deformity with or without image-guided navigation between 2007-2016. Conventional and navigated groups were propensity-matched (1:1) to normalize differences between demographics, comorbidities, and surgical characteristics. Clinical outcomes and charges were compared between matched groups using bivariate analyses.

RESULTS

A total of 4,604 patients were identified as having undergone deformity correction, of which 286 (6.2%) were navigated. Propensity-matching resulted in a total of 572 well-matched patients for subsequent analyses, of which half were navigated. Rate of mechanical instrumentation-related complications was found to be significantly lower for navigated procedures (p = 0.0371). Navigation was also associated with lower rates of 90-day unplanned readmissions (p = 0.0295), as well as 30- and 90-day postoperative revisions (30-day: p = 0.0304, 90-day: p = 0.0059). Hospital, physician, and total payments favored the conventional group for initial admission (p = 0.0481, 0.0001, 0.0019, respectively); however, when taking into account costs of readmissions, hospital payments became insignificantly different between the two groups.

CONCLUSIONS

Procedures involving image-guided navigation resulted in decreased instrumentation-related complications, unplanned readmissions, and postoperative revisions, highlighting its potential utility for the treatment of spine deformity. Future advances in navigation technologies and methodologies can continue to improve clinical outcomes, decrease costs, and facilitate widespread adoption of navigation for deformity correction.

The Navigated Oblique Lumbar Interbody Fusion: Accuracy Rate, Effect on Surgical Time, and Complications

Objective

The oblique lumbar interbody fusion (OLIF) can be done with either fluoroscopy or navigation. However, it is unclear how navigation affects the overall flow of the procedure. We wished to report on the accuracy of this technique using navigation and on how navigation affects surgical time and complications.

Methods

A retrospective review was undertaken to evaluate patients who underwent OLIF using spinal navigation at University of California San Francisco. Data collected were demographic variables, perioperative variables, and radiographic images. Postoperative lateral radiographs were analyzed for accuracy of cage placement. The disc space was divided into 4 quadrants from anterior to posterior, zone 1 being anterior, and zone 4 being posterior. The accuracy of cage placement was assessed by placement.

Results

There were 214 patients who met the inclusion criteria. A total of 350 levels were instrumented from L1 to L5 using navigation. The mean follow-up time was 17.42 months. The mean surgical time was 211 minutes, and the average surgical time per level was 129.01 minutes. After radiographic analysis, 94.86% of cages were placed within quartiles 1 to 3. One patient (0.47%) underwent revision surgery because of suboptimal cage placement. For approach-related complications, transient neurological symptoms were 10.28%, there was no vascular injury.

Conclusion

The use of navigation to perform OLIF from L1 to L5 resulted in a cage placement accuracy rate of 94.86% in 214 patients.

Conventional Versus Stereotactic Image-guided Pedicle Screw Placement During Posterior Lumbar Fusions: A Retrospective Propensity Score-matched Study of a National Longitudinal Database

STUDY DESIGN

Retrospective 1:1 propensity score-matched analysis on a national longitudinal database between 2007 and 2016.

OBJECTIVE

The aim of this study was to compare complication rates, revision rates, and payment differences between navigated and conventional posterior lumbar fusion (PLF) procedures with instrumentation.

SUMMARY OF BACKGROUND DATA

Stereotactic navigation techniques for spinal instrumentation have been widely demonstrated to improve screw placement accuracies and decrease perforation rates when compared to conventional fluoroscopic and free-hand techniques. However, the clinical utility of navigation for instrumented PLF remains controversial.

METHODS

Patients who underwent elective laminectomy and instrumented PLF were stratified into "single level" and "3- to 6-level" cohorts. Navigation and conventional groups within each cohort were balanced using 1:1 propensity score matching, resulting in 1786 navigated and conventional patients in the single-level cohort and 2060 in the 3 to 6 level cohort. Outcomes were compared using bivariate analysis.

RESULTS

For the single-level cohort, there were no significant differences in rates of complications, readmissions, revisions, and length of stay between the navigation and conventional groups. For the 3- to 6-level cohort, length of stay was significantly longer in the navigation group (P < 0.0001). Rates of readmissions were, however, greater for the conventional group (30-day: P = 0.0239; 90-day: P = 0.0449). Overall complications were also greater for the conventional group (P = 0.0338), whereas revision rate was not significantly different between the 2 groups. Total payments were significantly greater for the navigation group in both the single level and 3- to 6-level cohorts (P < 0.0001).

CONCLUSION

Although use of navigation for 3- to 6-level instrumented PLF was associated with increased length of stay and payments, the concurrent decreased overall complication and readmission rates alluded to its potential clinical utility. However, for single-level instrumented PLF, no differences in outcomes were found between groups, suggesting that the value in navigation may lie in more complex procedures.

LEVEL OF EVIDENCE

3.

Effect of computer navigation-assisted minimally invasive direct lateral interbody fusion in the treatment of patients with lumbar tuberculosis: A retrospective study

The benefits of navigation-assisted technologies are not entirely understood. Therefore, this study aimed to examine the outcomes of patients with lumbar tuberculosis who received computer navigation-assisted minimally invasive direct lateral interbody fusion (DLIF).This was a retrospective study of 33 patients with lumbar tuberculosis who underwent minimally invasive DLIF at the Department of Spine and Orthopedics of Guigang People's Hospital (Guangxi, China) between January 2015 and December 2016. The patients were pathologically diagnosed as lumbar tuberculosis and grouped into the navigation-assisted fluoroscopy (NAV; n = 18) and non-navigation-assisted fluoroscopy (non-NAV; n = 15) groups. X-ray exposure and operation times were assessed in all patients.All surgical procedures were successfully completed. No case was converted into open surgery. The NAV group had longer surgical preparation time but shorter operation time compared with the non-NAV group (both P <.01). Total operation time showed no significant difference between the 2 groups (P = .1). The time of radiation exposure in the non-NAV group was longer compared with that of the NAV group (53.2 ± 9.9 vs 13.5 ± 2.6 s; P <.01). There were no significant differences regarding intraoperative blood loss, postoperative drainage volume, length of hospital stay, bone fusion and complications between the 2 groups (all P >.05).Computer navigation-assisted minimally invasive DLIF could significantly reduce intraoperative radiation exposure, with no increase in total operation time.

Fate of S2-Alar-Iliac Screws After 12-Month Minimum Radiographic Follow-up: Preliminary Results

BACKGROUND

S2-alar-iliac (S2AI) screws are 1 technique for lumbopelvic fixation to improve fusion rates across the lumbosacral junction that has gained wider acceptance. The S2AI screw crosses the cortical surfaces of the sacroiliac joint (SIJ), which may improve the biomechanical strength of the instrumentation.

OBJECTIVE

To report preliminary radiographic outcomes of patients who underwent lumbopelvic fixation with S2AI screws with a minimum 12-month follow-up.

METHODS

We retrospectively reviewed adult patients who underwent lumbopelvic fixation with S2AI screws. Patients with computed tomography (CT) scans obtained preoperatively and ≥12 months postoperatively were reviewed to determine whether there was S2AI screw backout or breakage, periscrew lucency, or SIJ degeneration, and to assess L5-S1 fusion status.

RESULTS

Twenty-six S2AI screws in 13 patients were evaluated (mean follow-up 24.8 months [14-52 months]). Nine patients had L5-S1 interbody grafts. Partial periscrew lucency was identified in 7 S2AI screws (27%) in 5 patients (38%), and L5-S1 fusion occurred in 92% of patients. L5-S1 nonunion was seen in 1 patient (8%), who had evidence of bilateral screw loosening in the sacral portion. Four patients with screw loosening had an osseous L5-S1 fusion. No patients had radiographic evidence of progression of SIJ degeneration, experienced screw backout or breakage, required reoperation for L5-S1 nonunion, or had S2AI screw-related complication.

CONCLUSION

S2AI screws maintained their integrity without causing SIJ degeneration or major screw-related complications in this small retrospective series with short follow-up. Long-term results are needed to evaluate the durability of S2AI screws over time.

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.

Intraoperative navigation for accurate midline placement of anterior lumbar interbody fusion and total disc replacement prosthesis

Anterior lumbar approach techniques for the management of discogenic back pain and placement of spinal instrumentation such as fusion and disc replacement prosthesis is becoming increasingly popular. To date, no studies have reported the clinical usage of spinal navigation with anterior lumber interbody fusion (ALIF) and total disk replacement (TDR). We describe a surgical procedure of a 35-year-old patient presenting with discogenic lower back pain treated with an anterior lumbar interbody fusion and total disc replacement procedure to highlight the clinical advantages of intraoperative CT spinal navigation for accurate implant placement, therefore optimising peri- and post-operative outcomes.

Total Navigation in Spine Surgery; A Concise Guide to Eliminate Fluoroscopy Using a Portable Intraoperative Computed Tomography 3-Dimensional Navigation System

BACKGROUND

Portable intraoperative computed tomography (iCT) with integrated 3-dimensional navigation (NAV) offers new opportunities for more precise navigation in spinal surgery, eliminates radiation exposure for the surgical team, and accelerates surgical workflows. We present the concept of "total navigation" using iCT NAV in spinal surgery. Therefore, we propose a step-by-step guideline demonstrating how total navigation can eliminate fluoroscopy with time-efficient workflows integrating iCT NAV into daily practice.

METHODS

A prospective study was conducted on collected data from patients undergoing iCT NAV-guided spine surgery. Number of scans, radiation exposure, and workflow of iCT NAV (e.g., instrumentation, cage placement, localization) were documented. Finally, the accuracy of pedicle screws and time for instrumentation were determined.

RESULTS

iCT NAV was successfully performed in 117 cases for various indications and in all regions of the spine. More than half (61%) of cases were performed in a minimally invasive manner. Navigation was used for skin incision, localization of index level, and verification of implant position. iCT NAV was used to evaluate neural decompression achieved in spinal fusion surgeries. Total navigation eliminates fluoroscopy in 75%, thus reducing staff radiation exposure entirely. The average times for iCT NAV setup and pedicle screw insertion were 12.1 and 3.1 minutes, respectively, achieving a pedicle screw accuracy of 99%.

CONCLUSIONS

Total navigation makes spine surgery safer and more accurate, and it enhances efficient and reproducible workflows. Fluoroscopy and radiation exposure for the surgical staff can be eliminated in the majority of cases.

Segmental Surface Referencing during Intraoperative Three-dimensional Image-Guided Spine Navigation: An Early Validation with Comparison to Automated Referencing

Study Design Interventional human cadaver study. Objective Intraoperative three-dimensional (3-D)-guided navigation improves spine instrumentation accuracy. However, image acquisition may need to be repeated with segment hypermobility or distant target from reference frame (RF). The current study evaluates the usefulness of internal metal fiducials (IMFs) as surface references in enhancing registration accuracy and avoiding repeating imaging. Methods Six fresh-frozen cadaveric human torsos were utilized. Posterior C1-T2 exposure was done, and three IMFs were inserted per level; intraoperative 3-D images were then acquired. Two registration methods were utilized: autoregistration (AR, group 1) and point registration using IMF (IMFR, group 2). Registration accuracy was checked by identifying IMFs in both groups. Pedicle screws inserted into C2, C4, C5, and C7 based on the two registration methods (three cadavers each) with RF on C7 and then on C2. Results The mean registration error was lower with IMFR compared with AR (0.35 ± 0.5 mm versus 2.02 ± 0.85 mm, p = 0.0001). Overall, 34 pedicle screws were inserted (AR, 18; IMFR, 16). Final screw placement was comparable using both techniques (p = 0.58). Lateral screws violations were observed in four IMFR screws (1 to 2 mm) as compared with five in AR group (2 to 3 mm). Reregistration after moving RF to C2 was possible using surface screws in IMFR group, thus avoiding new 3-D image acquisition. Conclusion During intraoperative 3-D navigation in spine procedures, surface fiducial registration using IMF provided superior accuracy over automated registration. It allowed repeat registration without repeating radiation during long spine segment instrumentations. More studies are needed to clarify both practical and clinical application of this method.

A service for monitoring the quality of intraoperative cone beam CT images

In recent years, operating rooms (ORs) have transformed into integrated operating rooms, where devices are able to communicate, exchange data, or even steer and control each other. However, image data processing is commonly done by dedicated workstations for specific clinical use-cases. In this paper, we propose a concept for a dynamic service component for image data processing on the example of automatic image quality assessment (AQUA) of intraoperative cone beam computed tomography (CBCT) images. The service is build using the Open Surgical Communication Protocol (OSCP) and the standard for Digital Imaging and Communications in Medicine (DICOM). We have validated the proposed concept in an integrated demonstrator OR.

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.

The evolution of image-guided lumbosacral spine surgery

Techniques and approaches of spinal fusion have considerably evolved since their first description in the early 1900s. The incorporation of pedicle screw constructs into lumbosacral spine surgery is among the most significant advances in the field, offering immediate stability and decreased rates of pseudarthrosis compared to previously described methods. However, early studies describing pedicle screw fixation and numerous studies thereafter have demonstrated clinically significant sequelae of inaccurate surgical fusion hardware placement. A number of image guidance systems have been developed to reduce morbidity from hardware malposition in increasingly complex spine surgeries. Advanced image guidance systems such as intraoperative stereotaxis improve the accuracy of pedicle screw placement using a variety of surgical approaches, however their clinical indications and clinical impact remain debated. Beginning with intraoperative fluoroscopy, this article describes the evolution of image guided lumbosacral spinal fusion, emphasizing two-dimensional (2D) and three-dimensional (3D) navigational methods.

Three-Dimensional Computed Tomography-Based Spinal Navigation in Minimally Invasive Lateral Lumbar Interbody Fusion: Feasibility, Technique, and Initial Results

BACKGROUND

As with most minimally invasive spine procedures, lateral lumbar interbody fusion (LLIF) requires the use of biplanar fluoroscopy for localization and safe interbody cage placement. Computed tomography (CT)-based intraoperative spinal navigation has been shown to be more effective than fluoroscopic guidance for posterior-based approaches such as pedicle screw instrumentation. However, the use of spinal navigation in LLIF has not been well studied.

OBJECTIVE

To present the technique for using an intraoperative cone-beam CT and image-guided navigation system in LLIF and to provide a preliminary analysis of outcomes.

METHODS

We retrospectively analyzed a prospectively acquired database and the electronic records of patients undergoing LLIF with spinal navigation. Eight patients were identified. Postoperative neurological deficits were recorded. All patients underwent postprocedural CT and x-ray imaging for analysis of accuracy of cage placement. Accuracy of cage placement was determined by location within the disk space.

RESULTS

The mean age was 66 years, and 6 patients were women. A mean 2.8 levels were treated with a total of 22 lateral cages implanted via navigation. All cages were placed within quarters 1 to 2 or 2 to 3, signifying the anterior half or middle portions of the disk space. There were no sensory or motor deficits postoperatively.

CONCLUSION

Use of an intraoperative cone-beam CT with an image-guided navigation system is feasible and safe and appears to be accurate, although a larger study is required to confirm these results.

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.

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.

2013 Young Investigator Award winner: how safe is lateral lumbar interbody fusion for the surgeon? A prospective in vivo radiation exposure study

STUDY DESIGN

Prospective in vivo radiation exposure study.

OBJECTIVE

To assess surgeon exposure to ionizing radiation in the setting of lateral lumbar interbody fusion (LLIF).

SUMMARY OF BACKGROUND DATA

Minimally invasive spine surgery relies heavily on image guidance. Rapid popularization of minimally invasive spine surgery procedures, such as LLIF, is appropriately accompanied by concern regarding occupational radiation exposure related to intraoperative fluoroscopy.

METHODS

Optically stimulated luminescence technology dosimeters were used to record radiation exposure prospectively at 5 anatomic locations during 18 LLIF procedures: (1) eye, (2) thyroid, (3) chest, (4) axilla, and (5) gluteal region. Additionally, a ring dosimeter was worn during 13 of the LLIF cases.

RESULTS

Average fluoroscopy time was 88.7 ± 36.8 seconds and skin dose to the patient was 25.2 ± 21.1 mGy. The chest dosimeter protected by lead recorded the lowest readings per procedure (0.44 ± 0.49 mrem). The gluteal dosimeter recorded an average exposure of 2.31 ± 4.50 mrem and the dosimeter at the axilla recorded an average of 4.20 ± 7.76 mrem per procedure. Exposure to the thyroid and eye were 2.19 ± 2.07 mrem and 2.64 ± 2.76 mrem, respectively. With the exception of the gluteal region, dosimeter readings from all unprotected areas were significantly higher than those from the chest dosimeter (P < 0.0125). In the course of 13 procedures, 190 mrem of exposure to the hand was recorded by the ring dosimeters. More than 2700 LLIF procedures may be performed annually before occupational limits are exceeded.

CONCLUSION

Prolonged exposure to "low-level" radiation as an occupational risk remains a concern for medical personnel. Radiation exposures to unprotected, radiosensitive locations, such as the axilla or eye, are worrisome. However, following radiation safety guidelines, 2700 LLIF procedures can be performed per year before exceeding occupational dose limits. Adherence to radiation safety guidelines is necessary to avoid sequelae related to an invisible but potentially deadly risk of minimally invasive spine surgery procedures.

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

OBJECT

Surgeon and operating room (OR) staff radiation exposure during spinal surgery is a concern, especially with the increasing use of multiplanar fluoroscopy in minimally invasive spinal surgery procedures. Cone beam computed tomography (cbCT)-based, 3D image guidance does not involve the use of active fluoroscopy during instrumentation placement and therefore decreases radiation exposure for the surgeon and OR staff during spinal fusion procedures. However, the radiation scatter of a cbCT device can be similar to that of a standard 64-slice CT scanner and thus could expose the surgeon and OR staff to radiation during image acquisition. The purpose of the present study was to measure radiation exposure at several unshielded locations in the OR when using cbCT in conjunction with 3D image-guided spinal surgery in 25 spinal surgery cases.

METHODS

Five unshielded badge dosimeters were placed at set locations in the OR during 25 spinal surgery cases in which cbCT-based, 3D image guidance was used. The cbCT device (O-ARM) was used in conjunction with the Stealth S7 image-guided platform. The radiology department analyzed the badge dosimeters after completion of the last case.

RESULTS

Fifty high-definition O-ARM spins were performed in 25 patients for spinal registration and to check instrumentation placement. Image-guided placement of 124 screws from C-2 to the ileum was accomplished without complication. Badge dosimetry analysis revealed minimal radiation exposure for the badges 6 feet from the gantry in the area of the anesthesiology equipment, as well as for the badges located 10-13 feet from the gantry on each side of the room (mean 0.7-3.6 mrem/spin). The greatest radiation exposure occurred on the badge attached to the OR table within the gantry (mean 176.9 mrem/spin), as well as on the control panel adjacent to the gantry (mean 128.0 mrem/spin).

CONCLUSIONS

Radiation scatter from the O-ARM was minimal at various distances outside of and not adjacent to the gantry. Although the average radiation exposure at these locations was low, an earlier study, undertaken in a similar fashion, revealed no radiation exposure when the surgeon stood behind a lead shield. This simple precaution can eliminate the small amount of radiation exposure to OR staff in cases in which the O-ARM is used.

Screw placement accuracy for minimally invasive transforaminal lumbar interbody fusion surgery: a study on 3-d neuronavigation-guided surgery

Purpose The aim of this study was to assess the impact of 3-D navigation for pedicle screw placement accuracy in minimally invasive transverse lumbar interbody fusion (MIS-TLIF). Methods A retrospective review of 52 patients who had MIS-TLIF assisted with 3D navigation is presented. Clinical outcomes were assessed with the Oswestry Disability Index (ODI), Visual Analog Scales (VAS), and MacNab scores. Radiographic outcomes were assessed using X-rays and thin-slice computed tomography. Result The mean age was 56.5 years, and 172 screws were implanted with 16 pedicle breaches (91.0% accuracy rate). Radiographic fusion rate at a mean follow-up of 15.6 months was 87.23%. No revision surgeries were required. The mean improvement in the VAS back pain, VAS leg pain, and ODI at 11.3 months follow-up was 4.3, 4.5, and 26.8 points, respectively. At last follow-up the mean postoperative disc height gain was 4.92 mm and the mean postoperative disc angle gain was 2.79 degrees. At L5-S1 level, there was a significant correlation between a greater disc space height gain and a lower VAS leg score. Conclusion Our data support that application of 3-D navigation in MIS-TLIF is associated with a high level of accuracy in the pedicle screw placement.