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Ludwig Orozco, William Hanigan, Majid Khan, Jonathan Fratkin, and Marcus Lee

The authors describe the unique presentation of Balamuthia mandrillaris encephalitis in a kidney donor and two recipients. All three patients suffered acute clinical deterioration, with radiological or clinical evidence of intracranial hypertension. Brain autopsy in the donor and an urgent brain biopsy in a recipient established the diagnosis. Firsttier therapy, with mannitol and CSF drainage, successfully treated the intracranial hypertension in both recipients, while administration of a combination of antiamebic drugs was associated with survival in the second recipient. For both recipients, neurosurgical management played a critical role in the rapid diagnosis and treatment of Balamuthia mandrillaris encephalitis.

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Srujan Kopparapu, Daniel Lubelski, Zach Pennington, Majid Khan, Nicholas Theodore, and Daniel Sciubba

OBJECTIVE

Percutaneous vertebroplasty (PV) and balloon kyphoplasty (BK) are two minimally invasive techniques used to treat mechanical pain secondary to spinal compression fractures. A concern for both procedures is the radiation exposure incurred by both operators and patients. The authors conducted a systematic review of the available literature to examine differences in interventionalist radiation exposure between PV and BK and differences in patient radiation exposure between PV and BK.

METHODS

The authors conducted a search of the PubMed, Ovid Medline, Cochrane Reviews, Embase, and Web of Science databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Full-text articles in English describing one of the primary endpoints in ≥ 5 unique patients treated with PV or BK of the mobile spine were included. Estimates of mean operative time, radiation exposure, and fluoroscopy duration were reported as weighted averages. Additionally, annual occupational dose limits provided by the United States Nuclear Regulatory Commission (USNRC) were used to determine the number needed to harm (NNH).

RESULTS

The meta-analysis included 27 articles. For PV, the mean fluoroscopy times were 4.9 ± 3.3 minutes per level without protective measures and 5.2 ± 3.4 minutes with protective measures. The mean operator radiation exposures per level in mrem were 4.6 ± 5.4 at the eye, 7.8 ± 8.7 at the neck, 22.7 ± 62.4 at the torso, and 49.2 ± 62.2 at the hand without protective equipment and 0.3 ± 0.1 at the torso and 95.5 ± 162.5 at the hand with protection. The mean fluoroscopy times per level for BK were 6.1 ± 2.5 minutes without protective measures and 6.0 ± 3.2 minutes with such measures. The mean exposures were 31.3 ± 39.3, 19.7 ± 4.6, 31.8 ± 34.2, and 174.4 ± 117.3 mrem at the eye, neck, torso, and hand, respectively, without protection, and 1, 9.2 ± 26.2, and 187.7 ± 100.4 mrem at the neck, torso, and hand, respectively, with protective equipment. For protected procedures, radiation to the hand was the limiting factor and the NNH estimates were 524 ± 891 and 266 ± 142 for PV and BK, respectively. Patient exposure as measured by flank-mounted dosimeters, entrance skin dose, and dose area product demonstrated lower exposure with PV than BK (p < 0.01).

CONCLUSIONS

Operator radiation exposure is significantly decreased by the use of protective equipment. Radiation exposure to both the operator and patient is lower for PV than BK. NNH estimates suggest that radiation to the hand limits the number of procedures an operator can safely perform. In particular, radiation to the hand limits PV to 524 and BK to 266 procedures per year before surpassing the threshold set by the USNRC.

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A cadaveric precision and accuracy analysis of augmented reality–mediated percutaneous pedicle implant insertion

Presented at the 2020 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Camilo A. Molina, Frank M. Phillips, Matthew W. Colman, Wilson Z. Ray, Majid Khan, Emanuele Orru’, Kornelis Poelstra, and Larry Khoo

OBJECTIVE

Augmented reality–mediated spine surgery (ARMSS) is a minimally invasive novel technology that has the potential to increase the efficiency, accuracy, and safety of conventional percutaneous pedicle screw insertion methods. Visual 3D spinal anatomical and 2D navigation images are directly projected onto the operator’s retina and superimposed over the surgical field, eliminating field of vision and attention shift to a remote display. The objective of this cadaveric study was to assess the accuracy and precision of percutaneous ARMSS pedicle implant insertion.

METHODS

Instrumentation was placed in 5 cadaveric torsos via ARMSS with the xvision augmented reality head-mounted display (AR-HMD) platform at levels ranging from T5 to S1 for a total of 113 total implants (93 pedicle screws and 20 Jamshidi needles). Postprocedural CT scans were graded by two independent neuroradiologists using the Gertzbein-Robbins scale (grades A–E) for clinical accuracy. Technical precision was calculated using superimposition analysis employing the Medical Image Interaction Toolkit to yield angular trajectory (°) and linear screw tip (mm) deviation from the virtual pedicle screw position compared with the actual pedicle screw position on postprocedural CT imaging.

RESULTS

The overall implant insertion clinical accuracy achieved was 99.1%. Lumbosacral and thoracic clinical accuracies were 100% and 98.2%, respectively. Specifically, among all implants inserted, 112 were noted to be Gertzbein-Robbins grade A or B (99.12%), with only 1 medial Gertzbein-Robbins grade C breach (> 2-mm pedicle breach) in a thoracic pedicle at T9. Precision analysis of the inserted pedicle screws yielded a mean screw tip linear deviation of 1.98 mm (99% CI 1.74–2.22 mm) and a mean angular error of 1.29° (99% CI 1.11°–1.46°) from the projected trajectory. These data compare favorably with data from existing navigation platforms and regulatory precision requirements mandating that linear and angular deviation be less than 3 mm (p < 0.01) and 3° (p < 0.01), respectively.

CONCLUSIONS

Percutaneous ARMSS pedicle implant insertion is a technically feasible, accurate, and highly precise method.

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Jeff Ehresman, Andrew Schilling, Zach Pennington, Chengcheng Gui, Xuguang Chen, Daniel Lubelski, A. Karim Ahmed, Ethan Cottrill, Majid Khan, Kristin J. Redmond, and Daniel M. Sciubba

OBJECTIVE

Vertebral compression fractures (VCFs) in patients with spinal metastasis can lead to destabilization and often carry a high risk profile. It is therefore important to have tools that enable providers to predict the occurrence of new VCFs. The most widely used tool for bone quality assessment, dual-energy x-ray absorptiometry (DXA), is not often available at a patient’s initial presentation and has limited sensitivity. While the Spinal Instability Neoplastic Score (SINS) has been associated with VCFs, it does not take patients’ baseline bone quality into consideration. To address this, the authors sought to develop an MRI-based scoring system to estimate trabecular vertebral bone quality (VBQ) and to assess this system’s ability to predict the occurrence of new VCFs in patients with spinal metastasis.

METHODS

Cases of adult patients with a diagnosis of spinal metastasis, who had undergone stereotactic body radiation therapy (SBRT) to the spine or neurosurgical intervention at a single institution between 2012 and 2019, were retrospectively reviewed. The novel VBQ score was calculated for each patient by dividing the median signal intensity of the L1–4 vertebral bodies by the signal intensity of cerebrospinal fluid (CSF). Multivariable logistic regression analysis was used to identify associations of demographic, clinical, and radiological data with new VCFs.

RESULTS

Among the 105 patients included in this study, 56 patients received a diagnosis of a new VCF and 49 did not. On univariable analysis, the factors associated with new VCFs were smoking status, steroid use longer than 3 months, the SINS, and the novel scoring system—the VBQ score. On multivariable analysis, only the SINS and VBQ score were significant predictors of new VCFs and, when combined, had a predictive accuracy of 89%.

CONCLUSIONS

As a measure of bone quality, the novel VBQ score significantly predicted the occurrence of new VCFs in patients with spinal metastases independent of the SINS. This suggests that baseline bone quality is a crucial factor that requires assessment when evaluating these patients’ conditions and that the VBQ score is a novel and simple MRI-based measure to accomplish this.

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Camilo A. Molina, Nicholas Theodore, A. Karim Ahmed, Erick M. Westbroek, Yigal Mirovsky, Ran Harel, Emanuele Orru’, Majid Khan, Timothy Witham, and Daniel M. Sciubba

OBJECTIVE

Augmented reality (AR) is a novel technology that has the potential to increase the technical feasibility, accuracy, and safety of conventional manual and robotic computer-navigated pedicle insertion methods. Visual data are directly projected to the operator’s retina and overlaid onto the surgical field, thereby removing the requirement to shift attention to a remote display. The objective of this study was to assess the comparative accuracy of AR-assisted pedicle screw insertion in comparison to conventional pedicle screw insertion methods.

METHODS

Five cadaveric male torsos were instrumented bilaterally from T6 to L5 for a total of 120 inserted pedicle screws. Postprocedural CT scans were obtained, and screw insertion accuracy was graded by 2 independent neuroradiologists using both the Gertzbein scale (GS) and a combination of that scale and the Heary classification, referred to in this paper as the Heary-Gertzbein scale (HGS). Non-inferiority analysis was performed, comparing the accuracy to freehand, manual computer-navigated, and robotics-assisted computer-navigated insertion accuracy rates reported in the literature. User experience analysis was conducted via a user experience questionnaire filled out by operators after the procedures.

RESULTS

The overall screw placement accuracy achieved with the AR system was 96.7% based on the HGS and 94.6% based on the GS. Insertion accuracy was non-inferior to accuracy reported for manual computer-navigated pedicle insertion based on both the GS and the HGS scores. When compared to accuracy reported for robotics-assisted computer-navigated insertion, accuracy achieved with the AR system was found to be non-inferior when assessed with the GS, but superior when assessed with the HGS. Last, accuracy results achieved with the AR system were found to be superior to results obtained with freehand insertion based on both the HGS and the GS scores. Accuracy results were not found to be inferior in any comparison. User experience analysis yielded “excellent” usability classification.

CONCLUSIONS

AR-assisted pedicle screw insertion is a technically feasible and accurate insertion method.