Intraoperative Three-dimensional Navigation Research Articles

Intraoperative three-dimensional navigation for surgical treatment of osteoid osteoma in the upper extremity: A series of 19 cases.

The surgical treatment for osteoid osteoma (OO) in the upper extremity is challenging due to the difficulty in locating the lesion and the crowding of sensitive structures within the anatomy. This study aimed to describe the outcomes of navigated minimally invasive radiofrequency ablation and those of navigated mini open-intralesional curettage in treating these lesions. Nineteen consecutive patients with OO in the upper limb who underwent navigated surgery were included. The average QuickDASH and Numeric Pain Rating Scale improved from 62.2 ± 23.7 to 11.7 ± 16.9 and from 8.1 ± 1.6 to 0.5 ± 1.8, respectively (p < .01 each) following the procedure. Two complications were recorded: one patient had persistent radial nerve palsy, and one patient had transient partial radial nerve weakness. In conclusion, navigation is an important tool in the surgical treatment of OO in the upper limb. A mini open approach to identify and protect neurovascular structures is recommended.

Minimally invasive and invasive liver surgery based on augmented reality training: a review of the literature.

A liver surgeon's knowledge of anatomy is critical. Due to the patient's small field of vision, patient specific, complex nerve system, and other factors, even a minor loss can result in irreversible damage. Surgeons could benefit from the use of augmented reality (AR) technology, which would bring three-dimensional image data into the operating room. AR visualization can improve surgical procedures, facilitate intraoperative planning, and enhance surgical guidance for the anatomy of interest, all of which contribute to the application's minimal invasiveness. This literature review on image guidance in liver surgery provides the reader with information about AR techniques. To ascertain the current state of Augmented reality technology's application in liver surgery, a PubMed and Embase search were conducted using the following keywords: < (Augmented reality) AND (liver surgery) > and < 'Augmented reality' AND 'liver surgery' > (publication date from January 1991 until Jun 2022). The query yielded a total of 205 publications-excluded papers in other languages, virtual reality (VR), and reviews leaving 135 studies for review. After removing duplication, the titles and abstracts of those studies were manually reviewed. Finally, 31 pertinent studies were determined to be pertinent to the subject. Generally, augmented reality technology includes preoperative planning and three-dimensional reconstruction, intraoperative three-dimensional navigation, and registration. Visualization may be aided by virtual three-dimensional reconstruction models of the liver from Computed Tomography/Magnetic Resonance Imaging scans. The results demonstrate that by utilizing augmented reality technology, blood vessels and tumor structures in the liver can be visualized during surgery, allowing for precise navigation during complicated surgical procedures. Augmented reality has been demonstrated to be safe and effective in both minimally invasive and invasive liver surgery. With recent advancements and significant effort by liver surgeons, augmented reality technologies have the potential to increase hepatobiliary surgical procedures dramatically. However, further clinical trials will be necessary to evaluate augmented reality as a tool for reducing post-operative morbidity and mortality. The impact of these cutting-edge computerized image guidance techniques on clinically relevant outcome parameters should be assessed in the future.

Intraoperative three-dimensional navigation for surgical treatment of osteoid osteoma in the foot and ankle – A series of 14 cases

BackgroundThe surgical treatment for osteoid osteoma (OO) in the foot and ankle is challenging. It is difficult to locate the lesion and the anatomy is crowded by sensitive structures. The purpose of this study was to describe the outcomes of navigated mini open-intralesional curettage (NMIC) or navigated minimally invasive radiofrequency ablation (NMRFA) in treating these lesions. MethodsAll patients who underwent surgery for OO in the foot and ankle between 2015 and 2020 were included. O-arm navigation was used in All procedures. The choice of NMIC versus NMRFA was made by the surgeon according to the location of the lesion and its proximity to sensitive anatomic structures. ResultsFourteen patients were included. Ten were operated by NMRFA and 4 by NMIC. All patients’ symptoms related to OO resolved following a single procedure. Average AOFAS score increased by 18.7 (P < .001). Three patients had the following complications: pathologic fracture, superficial infection and transient deep peroneal nerve sensory loss. ConclusionNavigated surgical treatment of OO in the foot and ankle is accurate, efficient and safe.

The effectiveness of preoperative assessment using a patient-specific three-dimensional pseudoarticulation model for minimally invasive posterior resection in a patient with Bertolotti\u2019s syndrome: a case report

BackgroundBertolotti’s syndrome is widely known to cause low back pain in young patients and must be considered as a differential diagnosis. Its treatment such as conservative therapy or surgery remains controversial. Surgical procedure is recommended for intractable low back pain. The three-dimensional (3D) lumbosacral transitional vertebrae anatomy should be completely understood for a successful surgery. Using an intraoperative 3D navigation and preoperative preliminary surgical planning with a patient-specific 3D plaster model contribute for safe surgery and good outcome.Case presentationA case of a 22-year-old Japanese male patient with intractable left low back pain due to lumbosacral transitional vertebrae with Bertolotti’s syndrome. The symptom resisted the conservative treatment, and anesthetic injection at pseudoarticulation only provided a short-term pain relief. Posterior resection using intraoperative three-dimensional (3D) navigation has been performed through microendoscopic view. Pseudoarticulation was totally and successfully resected in a safe manner.ConclusionsPreoperative surgical planning and rehearsal using a patient-specific 3D plaster model was greatly useful and effective for surgeons in performing accurate and safe pseudoarticulation resection.

Minimally Invasive Percutaneous C1-C2 Fixation Using an Intraoperative Three-Dimensional Imaging–Based Navigation System for Management of Odontoid Fractures

Odontoid fractures are the most common lesions of the upper cervical spine in patients >70 years old. These fractures are associated with frequent comorbidities, and minimally invasive techniques might have the potential to reduce postoperative complications while ensuring better precision. The aim of this study was to report an innovative technique and preliminary results of minimally invasive atlantoaxial fixation using a three-dimensional intraoperative navigation system and percutaneous approach. This retrospective study included 5 consecutive patients with an acute traumatic odontoid type II fracture managed using a percutaneous Harms fixation under three-dimensional intraoperative navigation guidance. C1 lateral mass screws and C2 isthmus screws were successfully placed in all patients. In all cases (100%), adequate screw positioning with no medial breach and no transverse foramen obstruction was observed. No intraoperative complications, such as injury of the vertebral artery, spinal nerve root, or spinal cord, occurred. None of the 5 patients received blood transfusion during or after the procedure. During the follow-up period (mean, 11.2 months; range, 5-16 months), 4 patients (80%) demonstrated a favorable clinical recovery, and only 1 patient required occasional medication for moderate pain. Mean radiation exposure was 4.83 mSV for each patient and 0 mSv for surgical staff. Minimally invasive atlantoaxial fixation using an intraoperative three-dimensional navigation system is a safe and effective alternative to the conventional approach that reduces postoperative morbidity.

A Review of Techniques, Time Demand, Radiation Exposure, and Outcomes of Skin-anchored Intraoperative 3D Navigation in Minimally Invasive Lumbar Spinal Surgery.

Retrospective cohort. To describe our technique for and evaluate the time demand, radiation exposure and outcomes of skin-anchored intraoperative three-dimensional navigation (ION) in minimally invasive (MIS) lumbar surgery, and to compare these parameters to 2D fluoroscopy for MI-TLIF. Limited visualization of anatomic landmarks and narrow access corridor in MIS procedures result in greater reliance on image guidance. Although two-dimensional fluoroscopy has historically been used, ION is gaining traction. Patients who underwent MIS lumbar microdiscectomy, laminectomy, or MI-TLIF using skin-anchored ION and MI-TLIF by the same surgeon using 2D fluoroscopy were selected. Operative variables, radiation exposure, and short-term outcomes of all procedures were summarized. Time-demand and radiation exposure of fluoroscopy and ION for MI-TLIF were compared. Of the 326 patients included, 232 were in the ION cohort (92 microdiscectomies, 65 laminectomies, and 75 MI-TLIFs) and 94 in the MI-TLIF using 2D fluoroscopy cohort. Time for ION setup and image acquisition was a median of 22 to 24 minutes. Total fluoroscopy time was a median of 10 seconds for microdiscectomy, 9 for laminectomy, and 26 for MI-TLIF. Radiation dose was a median of 15.2 mGy for microdiscectomy, 16.6 for laminectomy, and 44.6 for MI-TLIF, of this, 93%, 95%, and 37% for microdiscectomy, laminectomy, and MI-TLIF, respectively were for ION image acquisition, with the rest attributable to the procedure. There were no wrong-level surgeries. Compared with fluoroscopy, ION for MI-TLIF resulted in lower operative times (92 vs. 108 min, P < 0.0001), fluoroscopy time (26 vs. 144 s, P < 0.0001), and radiation dose (44.6 vs. 63.1 mGy, P = 0.002), with equivalent time-demand and length of stay. ION lowered the radiation dose by 29% for patients and 55% for operating room personnel. Skin-anchored ION does not increase time-demand compared with fluoroscopy, is feasible, safe and accurate, and results in low radiation exposure. 3.

Quantification of computational geometric congruence in surface-based registration for spinal intra-operative three-dimensional navigation.

Background ContextComputer-assisted navigation (CAN) may guide spinal instrumentation, and requires alignment of patient anatomy to imaging. Iterative closest-point (ICP) algorithms register anatomical and imaging surface datasets, which may fail in the presence of geometric symmetry (congruence), leading to failed registration or inaccurate navigation. Here we computationally quantify geometric congruence in posterior spinal exposures, and identify predictors of potential navigation inaccuracy.MethodsMidline posterior exposures were performed from C1-S1 in four human cadavers. An optically-based CAN generated surface maps of the posterior elements at each level. Maps were reconstructed to include bilateral hemilamina, or unilateral hemilamina with/without the base of the spinous process. Maps were fitted to symmetrical geometries (cylindrical/spherical/planar) using computational modelling, and the degree of model fit quantified based on the ratio of model inliers to total points.Geometric congruence was subsequently assessed clinically in 11 patients undergoing midline exposures in the cervical/thoracic/lumbar spine for posterior instrumented fusion.ResultsIn cadaveric testing, increased cylindrical/spherical/planar symmetry was seen in the high-cervical and subaxial cervical spine relative to the thoracolumbar spine (p<0.001). Extension of unilateral exposures to include the ipsilateral base of the spinous process decreased symmetry independent of spinal level (p<0.001).In clinical testing, increased cylindrical/spherical/planar symmetry was seen in the subaxial cervical relative to the thoracolumbar spine (p<0.001), and in the thoracic relative to the lumbar spine (p<0.001). Symmetry in unilateral exposures was decreased by 20% with inclusion of the ipsilateral base of the spinous process.ConclusionsGeometric congruence is most evident at C1 and the subaxial cervical spine, warranting greater vigilance in navigation accuracy verification. At all levels, inclusion of the base of the spinous process in unilateral registration decreases the likelihood of geometric symmetry and navigation error. This work is important to allow the extension of line-of-sight based registration techniques to minimally-invasive unilateral approaches.

Treatment of Post-traumatic Pediatric Ankle Varus Deformity with Physeal Bar Resection and Hemi-Epiphysiodesis.

Children presenting with partial physeal arrest and significant remaining growth may benefit from physeal bar resection, although the operation is a technique demanding procedure. This study evaluates the treatment of post-traumatic pediatric ankle varus deformity using physeal bar resection and hemi-epiphysiodesis with the assistance of two operative methods. Forty-five patients presenting with a distal tibial medial physeal bridge as well as ankle varus deformity following traumatic ankle physeal injury between 2009 and 2017 were followed. These patients were treated with physeal bar resection and hemi-epiphysiodesis, with the assistance of either fluoroscopy (10 cases) or intraoperative three-dimensional navigation (35 cases). Of the 45 cases, the median age was 9.0 years (range: 3-14 years) with 28 male and 17 female patients. The median of pre-operation ankle varus angle was 20 degrees (IQR 15-25) and 5 degrees (IQR 0-20) at the time of final follow up, representing a statistically significant difference (P<0.05). No differences were observed with regards to age, gender, and surgical history between effective group and ineffective group (P>0.05). The median of pre-operative ankle varus angles of the navigation and fluoroscopy groups were both 20 degrees (P>0.05). The median correction angle of the navigation and fluoroscopy groups was 10 and 15 degrees, respectively (P>0.05). Our results indicate that physeal bar resection and hemiepiphysiodesis are effective treatments for correcting ankle varus deformity due to traumatic medial physeal arrest of the distal tibia. We observe no difference in outcome between fluoroscopy group and three-dimensional navigation group during the procedures.

Motion Preserving Surgery Using O-Arm for Unstable Hangman Fracture

Abstract Aim To evaluate clinical outcomes, radiological findings (displacement and angulation), and bony fusion in cases of unstable hangman’s fracture. Introduction Hangman fracture, also known as traumatic spondylolisthesis of axis vertebra, is classically defined as bilateral pars interarticularis fracture of axis vertebra. Opinions vary regarding optimal treatment of unstable hangman’s fractures. Some authors have recommended use of rigid orthosis, whereas others have recommended internal fixation. The peculiar anatomy of the upper cervical spine is highly variable, and presence of surrounding neurovascular structures makes axis pedicle screw fixation even more technically challenging. The advent of intraoperative three-dimensional navigation systems facilitates safe and accurate instrumentation. Materials and Methods This article analyzes patients operated for type II and IIa hangman’s fractures during the period from September 2011 to August 2018 by two neurosurgeons. The patients’ age, sex, mechanism of injury, associated injuries, and neurologic status were noted. The authors retrospectively assessed the clinical outcome, radiological findings (displacement and angulation), and bony fusion. Result Eighteen patients with age ranging from 17 to 81 years, were operated using computed tomography-based (O-arm) navigation. Accuracy of screw insertion, preoperative and postoperative displacement, and angulation of C2 over C3 were evaluated. Bony fusion was assessed in all patients. A total of 92 screws were inserted: 36 screws in C2 pedicle, 34 in C3 lateral mass, 20 in C4 lateral mass, and 2 in C5 lateral mass. Of these 92 screws, 36 C2 pedicle screws were inserted under O-arm guidance. The mean preoperative C2–C3 displacement was 4.5 ± 2.1 mm, and the mean postoperative displacement was 1.8 ± 1.1 mm with a mean reduction of 2.7 ± 1.4 mm. The mean preoperative C2–C3 angulation was 10.2 ± 7.6 degrees and the postoperative angulation was 2.52 ± 4.62 degrees with a mean reduction of 8.2 ± 11.6 degrees. Screw malplacement was seen in two C2 pedicle screws (2/36, 5.5%). All C2 pedicle screw breaches were of grade 2. Excellent anatomical reduction in all cases could be achieved as established by the improvement in morphological parameters of fracture. Conclusion This series using O-arm in unstable hangman fracture demonstrates that intraoperative O-arm-based navigation is a safe, accurate, and effective tool for screw placement in patients with unstable hangman fracture.

Accuracy of pedicle screw placement in the thoracic and lumbosacral spines using O-arm-based navigation versus conventional freehand technique

BackgroundThe accuracy and safety of pedicle screw insertion was markedly improved with the introduction of intraoperative three-dimensional navigation system during the last decade. This study aimed to evaluate the accuracy of pedicle screw placement using O-arm-based navigation system versus conventional freehand technique.MethodsWe reviewed the accuracy of 341 thoracic (n = 173) and lumbosacral (n = 168) pedicle screws placed in 60 consecutive patients using either O-arm-based navigation or freehand technique in the Department of Neurosurgery of Beijing Tsinghua Changgung Hospital between January 2015 and June 2018. Patient-specific characteristics, treatment-related characteristics, and screw-specific accuracy were analyzed. The accuracy of pedicle screw placement was measured by Gertzbein-Robbins scale and screw grades A and B were clinically acceptable.ResultsOne hundred ninety-one screws were inserted in the O-arm-based navigation group and 150 in the freehand group. One hundred eighty-three (95.81%) clinically acceptable screws were placed in the navigation group and 135 (90.00%) in the freehand group (p = 0.034). Twenty-three (6.74%) screw revisions were performed in the two groups (8 screws in the navigation group and 15 screws in the freehand group) and significant difference was observed in thoracic spine (p = 0.018), while no statistical significance was presented in lumbosacral spine (p > 0.05). Twenty-four (12.57%) screws in the navigation group and 24 (16.00%) in the freehand group violated the cortex (p > 0.05). Medial screw deviation was the most common problem in the two groups.ConclusionThe O-arm-based navigation exhibits higher accuracy for pedicle screw insertion than the freehand insertion technique.

Optical Topographic Imaging for Spinal Intraoperative Three-Dimensional Navigation in Mini-Open Approaches: A Prospective Cohort Study of Initial Preclinical and Clinical Feasibility

Computer-assisted three-dimensional navigation often guides spinal instrumentation. Optical topographic imaging (OTI) offers comparable accuracy and significantly faster registration relative to current navigation systems in open posterior thoracolumbar exposures. We validate the usefulness and accuracy of OTI in minimally invasive spinal approaches. Mini-open midline posterior exposures were performed in 4 human cadavers. Square exposures of 25, 30, 35, and 40 mm were registered to preoperative computed tomography imaging. Screw tracts were fashioned using a tracked awl and probe with instrumentation placed. Navigation data were compared with screw positions on postoperative computed tomography imaging, and absolute translational and angular deviations were computed. Invivo validation was performed in 8 patients, with mini-open thoracolumbar exposures and percutaneous placement of navigated instrumentation. Navigated instrumentation was performed in the previously described manner. For 37 cadaveric screws, absolute translational errors were (1.79 ± 1.43 mm) and (1.81 ± 1.51 mm) in the axial and sagittal planes, respectively. Absolute angular deviations were (3.81 ± 2.91°) and (3.45 ± 2.82°), respectively (mean ± standard deviation). The number of surface points registered by the navigation system, but not exposure size, correlated positively with the likelihood of successful registration (odds ratio, 1.02; 95% confidence interval, 1.009-1.024; P < 0.001). Fifty-five invivo thoracolumbar pedicle screws were analyzed. Overall (mean ± standard deviation) axial and sagittal translational errors were (1.79 ± 1.41 mm) and (2.68 ± 2.26 mm), respectively. Axial and sagittal angular errors were (3.63° ± 2.92°) and (4.65° ± 3.36°), respectively. There were no radiographic breaches >2 mm or any neurovascular complications. OTI is a novel navigation technique previously validated for open posterior exposures and in this study has comparable accuracy for mini-open minimally invasive surgery exposures. The likelihood of successful registration is affected more by the geometry of the exposure than by its size.

Utilization of Spinal Intra-operative Three-dimensional Navigation by Canadian Surgeons and Trainees: A Population-based Time Trend Study.

Computer-assisted navigation (CAN) improves the accuracy of spinal instrumentation in vertebral fractures and degenerative spine disease; however, it is not widely adopted because of lack of training, high capital costs, workflow hindrances, and accuracy concerns. We characterize shifts in the use of spinal CAN over time and across disciplines in a single-payer health system, and assess the impact of intra-operative CAN on trainee proficiency across Canada. A prospectively maintained Ontario database of patients undergoing spinal instrumentation from 2005 to 2014 was reviewed retrospectively. Data were collected on treated pathology, spine region, surgical approach, institution type, and surgeon specialty. Trainee proficiency with CAN was assessed using an electronic questionnaire distributed across 15 Canadian orthopedic surgical and neurosurgical programs. In our provincial cohort, 16.8% of instrumented fusions were CAN-guided. Navigation was used more frequently in academic institutions (15.9% vs. 12.3%, p&lt;0.001) and by neurosurgeons than orthopedic surgeons (21.0% vs. 12.4%, p&lt;0.001). Of residents and fellows 34.1% were fully comfortable using spinal CAN, greater for neurosurgical than orthopedic surgical trainees (48.1% vs. 11.8%, p=0.008). The use of CAN increased self-reported proficiency in thoracic instrumentation for all trainees by 11.0% (p=0.036), and in atlantoaxial instrumentation for orthopedic trainees by 18.0% (p=0.014). Spinal CAN is used most frequently by neurosurgeons and in academic centers. Most spine surgical trainees are not fully comfortable with the use of CAN, but report an increase in technical comfort with CAN guidance particularly for thoracic instrumentation. Increased education in spinal CAN for trainees, particularly at the fellowship stage and, specifically, for orthopedic surgery, may improve adoption.

P174 - Optical Topographic Imaging for Spinal Intraoperative Three-Dimensional Navigation in Minimally Invasive Approaches: Initial Preclinical Experience

BACKGROUND CONTEXT: Computer-assisted three-dimensional navigation may guide spinal instrumentation. The utility of intraoperative navigation is most evident in minimally-invasive (MIS) and deformity-correcting procedures, where anatomic landmarks are less readily identifiable. A novel optical topographic imaging (OTI) system for spinal navigation has been developed and described separately. While it offers comparable accuracy and significantly faster registration relative to current navigation systems, OTI to date has been applied only to open posterior exposures.

Intraoperative Three-Dimensional Navigation for Talocalcaneal Coalition Resection

Talocalcaneal tarsal coalitions are a common source of foot pain, stiffness, and deformity. These coalitions are treated symptomatically with rest and periods of immobilization. When those measures fail, surgical resection is attempted. This procedure is an anatomic challenge with the consequence of leaving residual coalition. The residual coalition primarily results from difficulty with intraoperative imaging because fluoroscopy does not provide adequate detail of this area. Some investigators have recommended intraoperative computed tomography after resection with reasonable results. We describe the combination of an intraoperative computed tomography with a navigated instrument system for resection of talocalcaneal coalitions. The use of a navigated probe and burr aids in defining the most anterior, posterior, and medial extents of the coalition. This technique reduces the morbidity, with less bone removed and preservation of intact subtalar articulations and allows for an efficient, thorough, and controlled resection.

P.088 Spinal computer-assisted intra-operative three-dimensional navigation in Canada: a population-based time trend study

Background: Spinal computer-assisted navigation (CAN) is proven to increase instrumentation accuracy. Adoption remains limited by workflow restrictions, learning curves and costs. Here, we assess spinal CAN usage among Ontario surgeons to identify gaps in application, and temporal trends of usage. Methods: A prospectively-collected database of provincial insurance billables and diagnostic codes was reviewed retrospectively, from 2002-2014. Patients undergoing instrumented spinal fusions or percutaneous vertebroplasty/kyphoplasty were identified. Fee and diagnostic codes were applied to distinguish surgical indication and approach. The use of intra-operative navigation was determined for each case. Results: We identified 4607 instrumented spinal fusions in our cohort. Most cases were performed by orthopedic surgeons (63.2%) and the remainder by neurosurgeons. Of 2239 cases with identifiable etiology, CAN was utilized in 8.8%, predominantly for trauma and degenerative pathologies rather than deformity. In univariate analyses, CAN was used more often by neurosurgeons (21.0% vs. 12.4%, p&lt;0.001), in academic institutions (15.9% vs. 12.3%, p&lt;0.001), and when performed in/after 2010 (18.9% vs. 8.9%, p&lt;0.001). Differences by specialty and year remained significant in multiple logistic regression. Conclusions: Spinal CAN has proven benefit for instrumentation accuracy, but is used preferentially by academic neurosurgeons. Significant gains must be made in cost and usability to improve access across disciplines and institutions.

GP.01 Quantification of computational geometric congruence in surface-based registration for spinal intra-operative three-dimensional navigation

Background: Computer-assisted navigation (CAN) may guide spinal instrumentation, and requires alignment of patient anatomy to imaging. Iterative-Closest-Point algorithms register anatomical and imaging datasets, which may fail in the presence of significant geometric congruence leading to inaccurate navigation. We computationally quantify geometric congruence in posterior spinal exposures, and identify predictors of potential navigation inaccuracy. Methods: Midline posterior exposures were performed from C1-S1 in four human cadavers. An optically-based CAN generated surface maps of the posterior elements at each level. Maps were reconstructed to include bilateral hemilamina, or unilateral hemilamina with/without the base of the spinous process. Maps were fitted to symmetrical geometries (cylindrical/spherical/planar) using computational modelling, and the degree of model fit quantified. Results: Increased cylindrical/spherical/planar symmetry was seen in the subaxial cervical spine relative to the high-cervical and thoracolumbar spine (p&lt;0.001). Inclusion of the base of the spinous process decreased symmetry independent of spinal level (p&lt;0.001). Registration with bilateral vs. unilateral hemilamina did not significantly reduce geometric symmetry. Conclusions: Geometric congruence is most evident at C1 and the subaxial cervical spine, warranting greater vigilance in navigation accuracy verification. At all levels, inclusion of the base of the spinous process in unilateral registration decreases the likelihood of geometric symmetry and navigation error.

Spinal intraoperative three-dimensional navigation: correlation between clinical and absolute engineering accuracy

Background ContextSpinal intraoperative computer-assisted navigation (CAN) may guide pedicle screw placement. Computer-assisted navigation techniques have been reported to reduce pedicle screw breach rates across all spinal levels. However, definitions of screw breach vary widely across studies, if reported at all. The absolute quantitative error of spinal navigation systems is theoretically a more precise and generalizable metric of navigation accuracy. It has also been computed variably and reported in less than a quarter of clinical studies of CAN-guided pedicle screw accuracy. PurposeThis study aimed to characterize the correlation between clinical pedicle screw accuracy, based on postoperative imaging, and absolute quantitative navigation accuracy. Design/SettingThis is a retrospective review of a prospectively collected cohort. Patient SampleWe recruited 30 patients undergoing first-time posterior cervical-thoracic-lumbar-sacral instrumented fusion±decompression, guided by intraoperative three-dimensional CAN. Outcome MeasuresClinical or radiographic screw accuracy (Heary and 2 mm classifications) and absolute quantitative navigation accuracy (translational and angular error in axial and sagittal planes). MethodsWe reviewed a prospectively collected series of 209 pedicle screws placed with CAN guidance. Each screw was graded clinically by multiple independent raters using the Heary and 2 mm classifications. Clinical grades were dichotomized per convention. The absolute accuracy of each screw was quantified by the translational and angular error in each of the axial and sagittal planes. ResultsAcceptable screw accuracy was achieved for significantly fewer screws based on 2 mm grade versus Heary grade (92.6% vs. 95.1%, p=.036), particularly in the lumbar spine. Inter-rater agreement was good for the Heary classification and moderate for the 2 mm grade, significantly greater among radiologists than surgeon raters. Mean absolute translational-angular accuracies were 1.75 mm-3.13° and 1.20 mm-3.64° in the axial and sagittal planes, respectively. There was no correlation between clinical and absolute navigation accuracy. ConclusionsRadiographic classifications of pedicle screw accuracy vary in sensitivity across spinal levels, as well as in inter-rater reliability. Correlation between clinical screw grade and absolute navigation accuracy is poor, as surgeons appear to compensate for navigation registration error. Future studies of navigation accuracy should report absolute translational and angular errors. Clinical screw grades based on postoperative imaging may be more reliable if performed in multiple by radiologist raters.

Necessity of intraoperative three-dimensional navigation for low lumbar spine: a randomized controlled study

To compare the accuracy of lower lumbar pedicle screw placement at different levels with or without navigation system. A prospective randomized controlled trial was conducted for patients undergoing open lumbar surgery with pedicle screws at both L4 and L5 levels from March 2011 to May 2012. The accuracy of pedicle screws at L4 and L5 level were evaluated by three-dimensional postoperative computed tomography (CT). There was no apparent violation of pedicle or < 2 mm perforation of pedicle in non-violation group while ≥ 2 mm perforation of pedicle in violation group. A total of 188 patients were recruited and assigned randomly into navigation (n = 47) and control (n = 141) groups. Two groups did not differ in estimated blood loss volume, length of hospital stay, Japanese Orthopedics Association (JOA) score or JOA recovery rate (P > 0.05). Navigation group had a longer operative duration (P < 0.05). At L4 level, 93/94 screws (98.9%) in navigation group and 273/282 screws (96.8%) in control group did not violate pedicle (P > 0.05). At L5 level, 93/94 screws (98.9%) in navigation group and 260/282 screws (92.2%) in control group did not violate pedicle. Thus navigation could achieve a higher accuracy at L5 level (P < 0.05). The profile of L5 pedicle at coronal plane is tilting oval. Screw may easily violate medioinferior part of pedicle and cause injures of nerve root. For improving the accuracy and safety of pedicle screw at L5 level, we recommend using intraoperative three-dimensional navigation for spondylolisthesis or facet hypertrophy, iliac cohesion or junior operator.

Posterior reduction and monosegmental fusion with intraoperative three-dimensional navigation system in the treatment of high-grade developmental spondylolisthesis.

Background:The treatment of high-grade developmental spondylolisthesis (HGDS) is still challenging and controversial. In this study, we investigated the efficacy of the posterior reduction and monosegmental fusion assisted by intraoperative three-dimensional (3D) navigation system in managing the HGDS.Methods:Thirteen consecutive HGDS patients were treated with posterior decompression, reduction and monosegmental fusion of L5/S1, assisted by intraoperative 3D navigation system. The clinical and radiographic outcomes were evaluated, with a minimum follow-up of 2 years. The differences between the pre- and post-operative measures were statistically analyzed using a two-tailed, paired t-test.Results:At most recent follow-up, 12 patients were pain-free. Only 1 patient had moderate pain. There were no permanent neurological complications or pseudarthrosis. The magnetic resonance imaging showed that there was no obvious disc degeneration in the adjacent segment. All radiographic parameters were improved. Mean slippage improved from 63.2% before surgery to 12.2% after surgery and 11.0% at latest follow-up. Lumbar lordosis changed from preoperative 34.9 ± 13.3° to postoperative 50.4 ± 9.9°, and 49.3 ± 7.8° at last follow-up. L5 incidence improved from 71.0 ± 11.3° to 54.0 ± 11.9° and did not change significantly at the last follow-up 53.1 ± 15.4°. While pelvic incidence remained unchanged, sacral slip significantly decreased from preoperative 32.7 ± 12.5° to postoperative 42.6 ± 9.8°and remained constant to the last follow-up 44.4 ± 6.9°. Pelvic tilt significantly decreased from 38.4 ± 12.5° to 30.9 ± 8.1° and remained unchanged at the last follow-up 28.1 ± 11.2°.Conclusions:Posterior reduction and monosegmental fusion of L5/S1 assisted by intraoperative 3D navigation are an effective technique for managing high-grade dysplastic spondylolisthesis. A complete reduction of local deformity and excellent correction of overall sagittal balance can be achieved.

Initial experience of intraoperative three-dimensional navigation for liver resection using real-time virtual sonography

Real-time virtual sonography is an innovative imaging technology that detects the spatial position of an ultrasound probe and immediately reconstructs a section of computed tomography (CT) and/or magnetic resonance in accordance with the ultrasound image, thereby allowing a real-time comparison of those modalities. A novel intraoperative navigation system for liver resection using real-time virtual sonography has been devised for the detection of tumors and navigation of the resection plane. Sixteen patients with hepatic malignancies (26 tumors in total) were involved in this study, and the system was used intraoperatively. The tumor size ranged 2 to 140 mm (23 mm in median). By the navigation system, operators could refer intraoperative ultrasound image displayed on the television monitor side-by-side with corresponding images of CT and/or magnetic resonance. In addition, the system overlaid preoperative simulation on the CT image and highlighted the extent of resection so as to navigate the resection plane. Because the system used electromagnetic power in the operation room, the feasibility and safety of the system was investigated as well as its validity. The system could be used uneventfully in each operation. All of the 26 tumors scheduled to be resected were detected by the navigation system. The weight of the resected specimen correlated with the preoperatively simulated volume (R = 0.995, P < .0001). The feasibility and safety of the navigation system were confirmed. The system should be helpful for intraoperative tumor detection and navigation of liver resection.