A Biomechanics-Aware Robot-Assisted Steerable Drilling Framework for Minimally Invasive Spinal Fixation Procedures.

In this paper, we propose a novel biomechanics-aware robot-assisted steerable drilling framework with the goal of addressing common complications of spinal fixation procedures occurring due to the rigidity of drilling instruments and implants. This framework is composed of two main unique modules to design a robotic system including (i) a Patient-Specific Biomechanics-aware Trajectory Selection Module used to analyze the stress and strain distribution along an implanted pedicle screw in a generic drilling trajectory (linear and/or curved) and obtain an optimal trajectory; and (ii) a complementary semi-autonomous robotic drilling module that consists of a novel Concentric Tube Steerable Drilling Robot (CT-SDR) integrated with a seven degree-of-freedom robotic manipulator. This semi-autonomous robot-assisted steerable drilling system follows a multi-step drilling procedure to accurately and reliably execute the optimal hybrid drilling trajectory (HDT) obtained by the Trajectory Selection Module. Performance of the proposed framework has been thoroughly analyzed on simulated bone materials by drilling various trajectories obtained from the finite element-based Selection Module using Quantitative Computed Tomography (QCT) scans of a real patient's vertebra.

A Concentric Tube Steerable Drilling Robot for Minimally Invasive Spinal Fixation of Osteoporotic Vertebrae.

Spinal fixation with rigid pedicle screws have shown to be an effective treatment for many patients. However, this surgical option has been proved to be insufficient and will eventually fail for patients experiencing osteoporosis. This failure is mainly attributed to the lack of dexterity in the existing rigid drilling instruments and the complex anatomy of vertebrae, forcing surgeons to implant rigid pedicle screws within the osteoporotic regions of anatomy. To address this problem, in this article, we present the design, fabrication, and evaluation of a unique flexible yet structurally strong concentric tube steerable drilling robot (CT-SDR). The CT-SDR is capable of drilling smooth and accurate curved trajectories through hard tissues without experiencing buckling and failure; thus enabling the use of novel flexible pedicle screws for the next generation of spinal fixation procedures. Particularly, by decoupling the control of bending and insertion degrees of freedom (DoF) of the CT-SDR, we present a robotic system that (i) is intuitive to steer as it does not require an on-the-fly control algorithm for the bending DoF, and (ii) is able to address the contradictory requirements of structural stiffness and dexterity of a flexible robot interacting with the hard tissue. The robust and repeatable performance of the proposed CT-SDR have been experimentally evaluated by conducting various drilling procedures on simulated bone materials and animal bone samples. Experimental results indicate drilling times as low as 35 seconds for curved trajectories with 41 mm length and remarkable steering accuracy with a maximum 2% deviation error.

Does preoperative magnetic resonance imaging alter the surgical plan in patients with acute traumatic cervical spinal cord injury?

BACKGROUND: Whether magnetic resonance imaging (MRI) adds value to surgical planning for patients with acute traumatic cervical spinal cord injury (ATCSCI) remains controversial. In this study, we compared surgeons' operative planning decisions with and without preoperative MRI. We had two hypotheses: (1) the surgical plan for ATCSCI would not change substantially after the MRI and (2) intersurgeon agreement on the surgical plan would also not change substantially after the MRI. METHODS: We performed a vignette-based survey study that included a retrospective review of all adult trauma patients who presented to our American College of Surgeons-verified level 1 trauma center from 2010 to 2019 with signs of acute quadriplegia and underwent computed tomography (CT), MRI, and subsequent cervical spine surgery within 48 hours of admission. We abstracted patient demographics, admission physiology, and injury details. Patient clinical scenarios were presented to three spine surgeons, first with only the CT and then, a minimum of 2 weeks later, with both the CT and MRI. At each presentation, the surgeons identified their surgical plan, which included timing (none, <8, <24, >24 hours), approach (anterior, posterior, circumferential), and targeted vertebral levels. The outcomes were change in surgical plan and intersurgeon agreement. We used Fleiss' kappa (κ) to measure intersurgeon agreement. RESULTS: Twenty-nine patients met the criteria and were included. Ninety-three percent of the surgical plans were changed after the MRI. Intersurgeon agreement was "slight" to "fair" both before the MRI (timing, κ = 0.22; approach, κ = 0.35; levels, κ = 0.13) and after the MRI (timing, κ = 0.06; approach, κ = 0.27; levels, κ = 0.10). CONCLUSION: Surgical plans for ATCSCI changed substantially when the MRI was presented in addition to the CT; however, intersurgeon agreement regarding the surgical plan was low and not improved by the addition of the MRI. LEVEL OF EVIDENCE: Diagnostic, level II.

The Monro-Kellie Doctrine in Action: Posterior Reversible Leukoencephalopathy Syndrome Caused by Intracranial Hypotension from Lumboperitoneal Shunt Placement.

BACKGROUND: Posterior reversible leukoencephalopathy syndrome (PRES) is linked to various etiologies, including most importantly systemic hypertension. Its association with intracranial hypotension (IH), a potential sequela of various neurosurgical procedures, is underrecognized. We report a case of lumboperitoneal shunt-induced IH resulting in PRES with the goal to increase awareness and elaborate on the potential biologic mechanism, based on the Monro-Kellie hypothesis. CASE DESCRIPTION: A 26-year-old woman with acquired immunodeficiency syndrome and epilepsy was admitted for recurrent cryptococcal meningitis and breakthrough seizures. There was radiologic evidence of ventricular enlargement, and opening pressure on serial lumbar punctures was constantly elevated. Owing to persistently elevated, symptomatic intracranial pressure and transient relief with serial lumbar punctures, a lumboperitoneal shunt was placed. The patient subsequently had a breakthrough seizure and became encephalopathic. Repeat head imaging showed reduced ventricular size, engorged venous sinuses, and tonsillar herniation in keeping with IH, coupled with extensive white matter abnormalities in bilateral parieto-occipital lobes indicative of PRES. The patient had an emergent programmable valve placed in the lumboperitoneal shunt to prevent excessive cerebrospinal fluid drainage, leading to clinical and radiologic improvement. Subsequent cerebrospinal fluid leak resulted in recurrent presentation. CONCLUSIONS: IH appears to be a distinct cause of PRES not previously reported in the neurosurgical literature. It occurs in susceptible patients, on average 1-5 days after the IH trigger, and seems clinically and radiologically similar to more common hypertensive cases in terms of initial presentation and prognosis. Increased vigilance is required for prompt recognition and management.

The role of neurosurgery journals in evidence-based neurosurgical care.

Neurosurgery journals have played an active role in improving the quality of the neurosurgical literature. This role has expanded to improve the quality of care by incorporating an evidence-based view of neurosurgery practice. Neurosurgery journals have facilitated the organization of knowledge into clinically useful forms via the publication of meta-analyses and dissemination of clinical practice guidelines. Peer review continues to be a core feature of neurosurgery publishing, with attendant ethical and procedural safeguards. Finally, neurosurgery journals have spearheaded innovative responses to cultural and technological changes, including initiatives to deliver high-quality research in electronic formats and support the education of future neurosurgery investigators.

Robotics and the spine: a review of current and ongoing applications.

OBJECT: Robotics in the operating room has shown great use and versatility in multiple surgical fields. Robot-assisted spine surgery has gained significant favor over its relatively short existence, due to its intuitive promise of higher surgical accuracy and better outcomes with fewer complications. Here, the authors analyze the existing literature on this growing technology in the era of minimally invasive spine surgery. METHODS: In an attempt to provide the most recent, up-to-date review of the current literature on robotic spine surgery, a search of the existing literature was conducted to obtain all relevant studies on robotics as it relates to its application in spine surgery and other interventions. RESULTS: In all, 45 articles were included in the analysis. The authors discuss the current status of this technology and its potential in multiple arenas of spinal interventions, mainly spine surgery and spine biomechanics testing. CONCLUSIONS: There are numerous potential advantages and limitations to robotic spine surgery, as suggested in published case reports and in retrospective and prospective studies. Randomized controlled trials are few in number and show conflicting results regarding accuracy. The present limitations may be surmountable with future technological improvements, greater surgeon experience, reduced cost, improved operating room dynamics, and more training of surgical team members. Given the promise of robotics for improvements in spine surgery and spine biomechanics testing, more studies are needed to further explore the applicability of this technology in the spinal operating room. Due to the significant cost of the robotic equipment, studies are needed to substantiate that the increased equipment costs will result in significant benefits that will justify the expense.

Atypical pituitary adenomas: incidence, clinical characteristics, and implications.

OBJECT: The 2004 WHO classification of pituitary adenomas now includes an "atypical" variant, defined as follows: MIB-1 proliferative index greater than 3%, excessive p53 immunoreactivity, and increased mitotic activity. The authors review the incidence of this atypical histopathological subtype and its correlation with tumor subtype, invasion, and surgical features. METHODS: The records of 121 consecutive patients who underwent transsphenoidal surgery for pituitary adenomas during an 18-month period were retrospectively reviewed for evidence of atypical adenomas. RESULTS: Eighteen adenomas (15%) met the criteria for atypical lesions; 17 (94%) of the 18 were macroadenomas. On imaging, 15 (83%) demonstrated imaging evidence of surrounding invasion, compared with 45% of typical adenomas (p = 0.004). Atypical tumors occurred in 12 female (67%) and 6 male (33%) patients. Patient age ranged from 16 to 70 years (mean 48 years). Nine patients (50%) had hormonally active tumors, and 9 had nonfunctional lesions. Four (22%) of the 18 patients presented to us with recurrent tumors. Immunohistochemical analysis demonstrated the following tumor subtypes: GH-secreting adenoma with plurihormonal staining (5 patients [28%]); null-cell adenoma (5 patients [28%]); silent ACTH tumor (3 patients [17%]), ACTH-staining tumor with Cushing's disease (2 patients [11%]), prolactinoma (2 patients [11%]), and silent FSH-staining tumor (1 patient [6%]). The MIB-1 labeling index ranged from 3% to 20% (mean 7%). CONCLUSIONS: Atypical tumors were identified in 15% of resected pituitary adenomas, and they tended to be aggressive, invasive macroadenomas. More longitudinal follow-up is required to determine whether surgical outcomes, potential for recurrence, or metastasis of atypical adenomas vary significantly from their typical counterparts.

Brain evolution and uniqueness in the human genome.

Despite an ever-expanding database of sequenced mammalian genomes to be mined for clues, the emergence of the unique human brain remains an evolutionary enigma. In their new study, trawl the human genome and those of other mammals in search of short conserved DNA elements that show extremely rapid evolution only in humans. As they report in a recent issue of Nature, their scan yielded a gene for a novel noncoding RNA that adopts a human-specific structure and may regulate neurodevelopment.