Oligomerization of protein arginine methyltransferase 1 and its effect on methyltransferase activity and substrate specificity.

Proper protein arginine methylation by protein arginine methyltransferase 1 (PRMT1) is critical for maintaining cellular health, while dysregulation is often associated with disease. How the activity of PRMT1 is regulated is therefore paramount, but is not clearly understood. Several studies have observed higher order oligomeric species of PRMT1, but it is unclear if these exist at physiological concentrations and there is confusion in the literature about how oligomerization affects activity. We therefore sought to determine which oligomeric species of PRMT1 are physiologically relevant, and quantitatively correlate activity with specific oligomer forms. Through quantitative western blotting, we determined that concentrations of PRMT1 available in a variety of human cell lines are in the sub-micromolar to low micromolar range. Isothermal spectral shift binding data were modeled to a monomer/dimer/tetramer equilibrium with an EC50 for tetramer dissociation of ~20 nM. A combination of sedimentation velocity and Native polyacrylamide gel electrophoresis experiments directly confirmed that the major oligomeric species of PRMT1 at physiological concentrations would be dimers and tetramers. Surprisingly, the methyltransferase activity of a dimeric PRMT1 variant is similar to wild type, tetrameric PRMT1 with some purified substrates, but dimer and tetramer forms of PRMT1 show differences in catalytic efficiencies and substrate specificity for other substrates. Our results define an oligomerization paradigm for PRMT1, show that the biophysical characteristics of PRMT1 are poised to support a monomer/dimer/tetramer equilibrium in vivo, and suggest that the oligomeric state of PRMT1 could be used to regulate substrate specificity.

Posterior Transdural Repair of a Spontaneous Ventral Thoracic Cerebrospinal Fluid Leak: 2-Dimensional Operative Video.

Spontaneous intracranial hypotension is a rare but serious condition characterized by orthostatic headaches and a variety of neurological symptoms. 1,2 Spontaneous intracranial hypotension should be considered in all patients with new onset, daily, persistent headaches, and orthostatic symptoms. It is typically caused by spontaneous spinal cerebrospinal fluid (CSF) leaks. 1,2 Traditional first-line treatments include hydration, bedrest, epidural blood patches, and fibrin glue injections. However, refractory cases often require surgical intervention, especially those caused by a small ventral osteophyte, which is classified as a type 1 leak. 3-5 The small osteophyte causes a tear in the dura of the ventral canal, usually near the cervicothoracic junction. Diagnosis of these leaks is challenging because these small osteophytes can also occur asymptomatically, or patients may have several of them at multiple levels. Typically, dynamic myelography is needed for accurate localization due to the inadequacy of standard imaging. 6 This video details a young patient with refractory spontaneous intracranial hypotension from a type 1 spontaneous CSF leak, treated successfully using a posterior transdural surgical approach with spinal cord mobilization. Our video presentation outlines the surgical technique and provides an overview of this underdiagnosed condition. Our described approach offers direct visualization, suturing of the leak site, and a multilayer repair without the need for spinal fusion. It also avoids the morbidity to the neck, chest, and mediastinal structures that is at risk with lateral or anterior approaches. A combined intradural and extradural repair may enhance the durability of repair for ventral CSF leaks. The patient consented to the procedure. This operative video did not require Institutional Review Board approval as all patient information has been anonymized, ensuring no identifiable information is disclosed. The video is a single case that does not involve interventions or pose risks beyond standard care, adhering to ethical guidelines and institutional policies.

Does type of bone graft matter? A retrospective review of the use of biological bone grafts in patients undergoing elective 1-3 level spinal interbody fusion.

OBJECTIVE: There is a lack of strong evidence for use of expensive bone substitutes. This study compares perioperative data and patient reported quality-of-life outcomes across the varied types of bone graft extenders. The study analyzes the existing Quality and Outcomes Database and evaluates patient reported outcomes for 1-3 level lumbar fusion procedures comparing across different types of biologics bone graft. METHODS: We retrospectively analyzed a prospectively collected data registry. Bone graft implant data were collected and grouped into the following categories: (1) Autograft with basic allograft (2) Enhanced, synthetic, or cellular allograft (3) Use of BMP. Preoperative and 1 year patient reported outcomes and perioperative data from the prospective collected registry were analyzed. RESULTS: There were 384 patients included in this study. There were 168 (43.8%) patients in group 1, 133 (34.6%) patients in group 2, and 83 (21.6%) in group 3. There were no group differences in baseline or 1 year back pain, leg pain, ODI, or EQ-5D. The GLM Repeated Measures results indicate a significant difference within each of the three groups between the preoperative and postoperative measures for back pain, leg pain, ODI, and EQ-5D. The change over time was not significantly different between the groups. CONCLUSIONS: Bone graft extenders are a significant contributor to the cost of lumbar fusion. This study demonstrates no difference in preoperative, and 1 year patient reported outcomes between the three groups. There was no significant difference in rate of reoperations across the three groups.

Impact of atmospheric deposition on the dynamics of ultraphytoplanktonic populations in the Gulf of Gabès during an intense dust event (MERITE-HIPPOCAMPE campaign).

The ultraphytoplankton composition and dynamics were assessed during a Saharan dust event occurring off the southern Tunisian coasts during the MERITE-HIPPOCAMPE Trans-Mediterranean oceanographic cruise. The composition of atmospheric dust was characterized in terms of nutriments and trace metals. Data-assimilative hydrodynamic model revealed no differences in the hydrological features along the sampling track and almost no water transport occurred during the period of atmospheric deposition. Dust deposition increased the growth rates and the productivity of the major phytoplanktonic cytometric groups, resulting in the highest surface biomass along the Mediterranean transect. One group, distinguished by low fluorescence and nanoplanktonic size, reacted to dust deposition within hours, exhibiting the highest growth rate and net productivity. The dust composition showed a substantial enrichment with organic phosphorous representing (56 % of Total phosphorus) and trace metals mainly Fe, Mn and V.

Transport patterns and hydrodynamic context of the MERITE-HIPPOCAMPE cruise: Implications for contaminants distribution and origin.

This study aims at characterizing the hydrodynamic context and transport patterns that prevailed during the MERITE-HIPPOCAMPE cruise to assist in the interpretation of in-situ observations. The main physical attributes and structures (mesoscale eddies as well as fine-scale fronts and filaments) are analyzed based on various physical diagnostics. They were computed from satellite data and data-assimilative model outputs to describe ocean dynamics. The Northern and Algerian Currents were prominent features during the cruise while the western basin is divided by the vertically-tilted Balearic front. Temperature and salinity were used to distinguish different water masses at both surface and sub-surface. Sea-level anomalies, relative vorticity, and Okubo-Weiss parameter distributions have shown the presence of marked eddies around stations St10 and St11. Furthermore, Finite-Size Lyaponuv Exponents revealed that the former was rather located on a fine-scale filament near the edge of a cyclonic eddy while the latter was closer to the core of an anticyclone. Nearshore thermal fronts were detected with the Belkin and O'Reilly Algorithm (BOA), especially around stations St17 and St19. The potential coastal sources of contaminants were tested using Lagrangian Origin Maps (LOM), suggesting that stations St1, St2, St4, St11, and St15 were most likely influenced by coastal waters. Additionally, an atmospheric reanalysis combined with a Lagrangian dispersal model allowed for estimating wet deposition events of contaminants while tracking the fate of water masses where rainfall took place. Finally, we provide a set of explanatory quantitative and qualitative variables for future statistical analyses that aim at explaining the distribution of both chemical and biological samples collected during the cruise.

An ocean front dataset for the Mediterranean sea and southwest Indian ocean.

Fronts are ubiquitous discrete features of the global ocean often associated with enhanced vertical velocities, in turn boosting primary production. Fronts thus form dynamical and ephemeral ecosystems where numerous species meet across all trophic levels. Fronts are also targeted by fisheries. Capturing ocean fronts and studying their long-term variability in relation with climate change is thus key for marine resource management and spatial planning. The Mediterranean Sea and the Southwest Indian Ocean are natural laboratories to study front-marine life interactions due to their energetic flow at sub-to-mesoscales, high biodiversity (including endemic and endangered species) and numerous conservation initiatives. Based on remotely-sensed Sea Surface Temperature and Height, we compute thermal fronts (2003-2020) and attracting Lagrangian coherent structures (1994-2020), in both regions over several decades. We advocate for the combined use of both thermal fronts and attracting Lagrangian coherent structures to study front-marine life interactions. The resulting front dataset differs from other alternatives by its high spatio-temporal resolution, long time coverage, and relevant thresholds defined for ecological provinces.

Microendoscopic Posterior Cervical Laminoforaminotomy for C4 Radiculopathy.

OBJECTIVE: Cervical microendoscopic laminoforaminotomy (MELF) has been proven to be an effective, motion preserving procedure for the surgical treatment of cervical radiculopathy. Cervical 4 (C4) radiculopathies are often unrecognized by the initial evaluating physician and may be misdiagnosed as axial neck pain. In this study, we compare MELF to anterior cervical disk fusion (ACDF) for C4 radiculopathy in the largest series of minimally invasive foraminotomy for C4 radiculopathy to date. METHODS: This is a single-institution retrospective chart review of 42 cases for C4 radiculopathy, 21 MELF and 21 ACDF. Primary outcome measures were length of surgery, length of hospital stay, and time to return to work. Secondary outcome measures were visual analog scale (VAS) neck pain and reoperation rate. RESULTS: All patients were diagnosed with a unilateral C4 radiculopathy using magnetic resonance imaging or steroid injections. The length of surgery and length of hospital stay were significantly decreased in the MELF group compared with ACDF. VAS neck pain significantly decreased for patients in both groups, but the difference between MELF and ACDF was not statistically significant. There were no major complications. No patient underwent revision at the index level or adjacent levels in the MELF group. CONCLUSIONS: We demonstrate that C4 radiculopathy can be identified with appropriate history, physical examination, and targeted nerve root injections. When identified, these radiculopathies that fail conservative therapy can be effectively treated with cervical microendoscopic laminoforaminotomy, with comparable outcomes to ACDF. The length of surgery and length of stay are reduced when compared with ACDF.

Lumbar arthroplasty for treatment of primary or recurrent lumbar disc herniation.

PURPOSE: Microdiscectomy is the current gold standard surgical treatment for primary lumbar disc herniations that fail non-surgical measures. Herniated nucleus pulposus is the manifestation of underlying discopathy that remains unaddressed with microdiscectomy. Therefore, risk remains of recurrent disc herniation, progression of the degenerative cascade, and on-going discogenic pain. Lumbar arthroplasty allows for complete discectomy, complete direct and indirect decompression of neural elements, restoration of alignment, restoration of foraminal height, and preservation of motion. In addition, arthroplasty avoids disruption of posterior elements and musculoligamentous stabilizers. The purpose of this study is to describe the feasibility of the use of lumbar arthroplasty in the treatment of patients with primary or recurrent disc herniations. In addition, we describe the clinical and peri-operative outcomes associated with this technique. METHODS: All patients that underwent lumbar arthroplasty by a single surgeon at a single institution from 2015 to 2020 were reviewed. All patients with radiculopathy and pre-operative imaging demonstrating disc herniation that received lumbar arthroplasty were included in the study. In general, these patients were those with large disc herniations, advanced degenerative disc disease, and a clinical component of axial back pain. Patient-reported outcomes of VAS back, VAS leg, and ODI pre-operatively, at three months, one year, and at last follow-up were collected. Reoperation rate, patient satisfaction, and return to work were documented at last follow-up. RESULTS: Twenty-four patients underwent lumbar arthroplasty during the study period. Twenty-two (91.6%) patients underwent lumbar total disc replacement (LTDR) for a primary disc herniation. Two patients (8.3%) underwent LTDR for a recurrent disc herniation after prior microdiscectomy. The mean age was 40 years. The mean pre-operative VAS leg and back pain were 9.2 and 8.9, respectively. The mean pre-operative ODI was 22.3. Mean VAS back and leg pain was 1.2 and 0.5 at three months post-operative. The mean VAS back and leg pain was 1.3 and 0.6 at one year post-operative. The mean ODI was 3.0 at one year post-operative. One patient (4.2%) underwent re-operation for migrated arthroplasty device which required repositioning. At last follow-up, 92% of patients were satisfied with their outcome and would undergo the same treatment again. The mean time for return-to-work was 4.8 weeks. After returning to work, 89% of patients required no further leave of absence for recurrent back or leg pain at last follow-up. Forty-four percent of patients were pain free at last follow-up. CONCLUSION: Most patients with lumbar disc herniations can avoid surgical intervention altogether. Of those that require surgical treatment, microdiscectomy may be appropriate for certain patients with preserved disc height and extruded fragments. In a subset of patients with lumbar disc herniation that require surgical treatment, lumbar total disc replacement is an effective option by performing complete discectomy, restoring disc height, restoring alignment, and preserving motion. The restoration of physiologic alignment and motion may result in durable outcomes for these patients. Longer follow-up and comparative and prospective trials are needed to determine how the outcomes of microdiscectomy may differ from lumbar total disc replacement in the treatment of primary or recurrent disc herniation.

Feasibility and Safety of Microendoscopic Posterior Cervical Foraminotomy in an Ambulatory Surgery Center: A Longitudinal Experience with 1000 Cases.

OBJECTIVE: Ambulatory surgery centers (ASCs) have become an increasingly attractive setting for spine surgery in recent decades. Although posterior cervical foraminotomy (PCF) is widely performed in ASCs, there are no studies supporting the safety of this practice. We aimed to demonstrate the feasibility and safety of microendoscopic (MED)-PCF in a large cohort of patients at a freestanding ASC. METHODS: Consecutive patients undergoing MED-PCF for unilateral cervical radiculopathy at a single freestanding ASC from January 2013 to December 2020 were queried. Standard demographic and perioperative data were collected. Outcomes included need for inpatient transfer, perioperative complications, 30-day readmission, 30-day reoperation, and clinical improvement according to the Odom criteria. RESULTS: A total of 1106 patients underwent MED-PCF during the study period. Mean age was 53.3 ± 10.3 years. Most patients underwent decompression at C5-6 (31.4%) or C6-7 (51.9%). Approximately 10% underwent surgery at multiple levels. Mean operative time was 40.0 ± 16.4 minutes. There were no intraoperative or immediate postoperative complications. All patients were discharged home within a few hours of surgery. The rates of 30-day readmission (0.81%) and reoperation (0.36%) were exceedingly low. Nearly 3 quarters of patients (73.7%) achieved a good or excellent clinical outcome (73.7%) according to the Odom criteria. CONCLUSIONS: MED-PCF can be performed in a freestanding ASC with exceedingly low rates of perioperative complications and short-term readmission or reoperation. Our findings support the ongoing migration of PCF from the hospital to the ambulatory setting. Future studies assessing patient-reported outcomes and long-term reoperation rates are necessary.

A Quantum Mechanical Description of Photosensitization in Photodynamic Therapy using a Two-Electron Molecule Approximation.

A fundamental, Quantum Mechanical description of photoactivation of a generic photosensitizer and the ensuing transfer of energy to endogenous oxygen as part of the Type II pathway to photodamage during photodynamic therapy (PDT) is presented. The PS and molecular oxygen are approximated as two-electron molecules. Conservation of energy and of angular momenta of the two molecule system are abided via selection rules throughout the four-stage process, including initial states, absorption of a photon by the PS, conversion of the PS to an excited spin triplet via intersystem crossing (ISC), and the transition of molecular oxygen to an excited spin singlet state via a Triplet-Triplet Exchange of electrons with the PS. The provided description of photosensitization will provide students and researchers with a fundamental introduction to PDT, while offering the broader population of Quantum Mechanics and Physical Chemistry students an advanced example of quantum systems in an applied, medical context.

Minimally Invasive Transforaminal Lumbar Interbody Fusion in the Ambulatory Setting with an Enhanced Recovery After Surgery Protocol.

OBJECTIVE: Enhanced Recovery After Surgery (ERAS) is a multidisciplinary approach to surgical care that aims to improve outcomes and reduce costs. Its application to spine surgery has been increasing in recent years, with a notable focus on lumbar fusion. This study describes the development, implementation, and outcomes of the first ERAS pathway for ambulatory spine surgery and the largest ambulatory minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) series to date. METHODS: A comprehensive protocol for ambulatory lumbar fusion is described, including patient selection criteria, a multimodal analgesia regimen, and discharge assessment. Consecutive patients undergoing 1- or 2-level MIS TLIF using the described protocol at a single ambulatory surgery center (ASC) over a five-year period were queried. RESULTS: A total of 215 patients underwent ambulatory MIS TLIF over the study period. There were no intraoperative or immediate postoperative complications. All but one patient (99.5%) were discharged home from the ASC. Almost three-quarters (71.2%) were discharged on the day of surgery. Thirty- and 90-day readmission rates were 1.4% and 2.8%, respectively. Only one readmission (0.5%) was for intractable back pain. There were no reoperations or mortalities within 90 days of surgery. CONCLUSIONS: MIS TLIF can be performed safely in a freestanding ambulatory surgery center with minimal perioperative and short-term morbidity. The addition of comprehensive ERAS protocols to the ambulatory setting can promote the transition of fusion procedures to this lower cost environment in an effort to provide higher value care.

Long-term outcomes following lumbar total disc replacement with M6-L.

Background: The motion preserving benefits of lumbar total disc replacement (LTDR) are well established. There is a paucity of long-term follow-up data on the M6-L prosthesis. The aim was to evaluate the clinical and radiographic outcomes of patients undergoing LTDR with M6-L and make comment about its effectiveness and durability. Methods: A retrospective single center chart review was performed of all patients who underwent LTDR with M6-L between January 1, 2011, and January 1, 2021, either as standalone device or combined with a caudal anterior lumbar interbody fusion (ALIF) (hybrid procedure). Preoperative, postoperative, and final follow-up patient reported outcome measures (PROMs) (VAS back, VAS leg, ODI, and SF-12) and patient satisfaction were recorded prospectively. Device range of motion (ROM), adjacent segment degeneration/disease and heterotopic ossification (HO) were obtained from flexion and extension lumbar radiographs at most recent follow-up. Results: Sixty patients underwent LTDR with the M6-L device. Mean age was 41 [16-71] years and 38 (63%) were male. Sixteen (26.7%) underwent standalone LTDR, 42 (70.0%) a hybrid procedure, and 2 (3.3%) a 3-level procedure. Twenty-three (38.3%) patients were lost to follow-up. Thirty-seven (61.7%) were followed for a mean of 4.3 [1-10] years with 36/37 reviewed at a minimum of 2-years and 13/37 followed for over 5-years. Only one patient with osteopenia needed index level revision LTDR surgery for subsidence requiring supplemental posterior instrumentation. There were no osteolysis induced device related failures. Thirty patients obtained long-term follow-up radiographic data. Six patients had adjacent segment degeneration; none required surgery for adjacent segment disease (ASD). Three patients presented with clinically significant HO (2 with McAfee class III, 1 with class IV). The average M6-L ROM was 8.6 degrees. Mean preoperative baseline PROMs demonstrated statistically significant improvements postoperatively and were sustained at last follow-up (P<0.05). Conclusions: Total disc replacement (TDR) with M6-L showed clinically significant improvement in PROMs that were sustained at long-term follow-up. There were no osteolysis induced device related failures. The device ROM was maintained and showed a downward trend over the 10-year study follow-up period. This paper demonstrated that the M6-L was an effective and durable arthroplasty device in this series.

Spatial coalescent connectivity through multi-generation dispersal modelling predicts gene flow across marine phyla.

Gene flow governs the contemporary spatial structure and dynamic of populations as well as their long-term evolution. For species that disperse using atmospheric or oceanic flows, biophysical models allow predicting the migratory component of gene flow, which facilitates the interpretation of broad-scale spatial structure inferred from observed allele frequencies among populations. However, frequent mismatches between dispersal estimates and observed genetic diversity prevent an operational synthesis for eco-evolutionary projections. Here we use an extensive compilation of 58 population genetic studies of 47 phylogenetically divergent marine sedentary species over the Mediterranean basin to assess how genetic differentiation is predicted by Isolation-By-Distance, single-generation dispersal and multi-generation dispersal models. Unlike previous approaches, the latter unveil explicit parents-to-offspring links (filial connectivity) and implicit links among siblings from a common ancestor (coalescent connectivity). We find that almost 70 % of observed variance in genetic differentiation is explained by coalescent connectivity over multiple generations, significantly outperforming other models. Our results offer great promises to untangle the eco-evolutionary forces that shape sedentary population structure and to anticipate climate-driven redistributions, altogether improving spatial conservation planning.

Arduino-based, low-cost imaging incubator for extended live cell imaging.

In order to image live cells for prolonged periods of time, an Arduino-based, low-cost imaging incubator was constructed. The imaging incubator keeps cells viable by controlling for temperature and CO 2 in order to maintain physiological conditions for cells during imaging. All devices and parts employed in the build were typical maker-type components in order to minimize the cost of the imaging incubator. The imaging incubator allows for real-time imaging of live cells exposed to any desired perturbation or stimulus. As a proof of the system's functionality, cells are imaged over 24 hours while remaining viable in the imaging incubator.

Negotiating for new technologies: guidelines for the procurement of assistive technologies in spinal surgery: a narrative review.

Background and Objective: This is a narrative review with the objective to discuss available assistive technologies for spinal surgery. Characteristics, costs, and compatibility of the different systems are summarized and recommendations made regarding acquiring these technologies. The availability of assistive technologies in spine surgery continues to evolve rapidly. The literature is lacking a collective summary of the available technologies and guidelines for acquisition. This is a narrative review which (I) presents an up-to-date summary of the currently available assistive technologies in spinal surgery; (II) makes comment on the utility of imaging, navigation, and robotics; (III) makes recommendations for the utility of the platform based on hospital size and (IV) discuss factors involved in negotiating for the purchase of these new technologies. Methods: We assemble the most up-to-date collection of description, characteristics and pricing of assistive technologies in spinal surgery. We compare and contrast these technologies and make recommendations regarding acquisition. Key Content and Findings: These technologies require a learning-curve for the surgeon and the operating room staff to understand how to use them efficiently. Surgeons need to be involved in the process of purchase decisions. Surgeons occupy a unique position in the health care infrastructure as their approach to care has significant ramifications on both the quality and cost of care. Surgeons should maintain conviction that their training and practice has allowed the use of these technologies to provide safer and more effective care for patients. Conclusions: Assistive technologies and prostheses for spinal fusion are evolving rapidly. This article serves as an encompassing reference to the current technologies. These technologies will play a significant role in the delivery of spinal health care in the future. All stakeholders stand to benefit from the increased value these technologies bring to patient care.

Navigated, Percutaneous Posterior Cervical Minimally Invasive Surgery Fixation: Technique and Nuances.

BACKGROUND: Cervical pedicle screw fixation provides a biomechanically superior fixation in comparison to traditional lateral mass screws. The traditional open technique has limited adoption due to technical challenges and significantly increased wound morbidity. Navigated, percutaneous pedicle screw fixation circumvents the traditional technical challenges and minimizes wound morbidity. We present here a technique description and case report of navigated, percutaneous posterior cervical minimally invasive fixation. METHODS: Small lateral skin incisions are made on the neck using intraoperative computed tomography-guided navigation. Navigated cervical pedicle screws were placed using the proficient minimally invasive system (Spine Wave, Shelton, CT). RESULTS: Minimally invasive cervical fixation options have been limited traditionally. Navigated, percutaneous cervical minimally invasive surgery (MIS) fixation provides an effective, safe option for cervical fixation. This technique is described and illustrated in a case example of a patient who suffered a burst fracture and underwent treatment. CONCLUSIONS: Navigated, percutaneous posterior cervical MIS fixation provides biomechanically superior fixation while avoiding the morbidity of traditional, open approaches to the posterior cervical spine. Percutaneous cervical pedicle screw techniques will be pivotal in the continued advancement of posterior cervical decompression and fusion techniques. CLINICAL RELEVANCE: Navigated, percutaneous cervical minimally invasive fixation is an achievable form of cervical fixation with acceptable complication rates and radiographic outcomes.

Percutaneous Posterior Cervical Pedicle Instrumentation (C1 to C7) With Navigation Guidance: Early Series of 27 Cases.

STUDY DESIGN: This is a technique paper describing minimally invasive, navigated, percutaneous pedicle screw fixation of the cervical spine. In addition, we include a retrospective feasibility analysis of our initial experience with 27 patients undergoing this procedure. OBJECTIVE: The purpose of this study is to describe the technique of MIS navigated percutaneous cervical pedicle screw instrumentation and to report our initial experience. METHODS: This is a retrospective review of 27 patients undergoing MIS navigated percutaneous posterior cervical pedicle screw fixation at 2 institutions. We describe the technique and report the radiographic outcomes and all intraoperative and postoperative complications. RESULTS: A total of 27 patients underwent MIS navigated percutaneous pedicle screw fixation. Indications included odontoid fracture, subaxial fracture dislocations and burst fracture, pathological fracture, and degenerative spondylosis. There were no nerve root or vascular injuries. There were no spinal cord injuries. Two screws required repositioning intraoperatively, and 1 patient required reoperation for symptomatic malpositioned screw. CONCLUSIONS: MIS navigated percutaneous posterior pedicle screw fixation can be performed safely. These constructs are biomechanically superior with neurovascular complication rates comparable to traditional lateral mass screw technique. While the current indications for this technique are relatively limited, the evolution of MIS cervical decompression techniques as well as navigation and robotics will provide an expanded role for percutaneous cervical pedicle screw instrumentation.

Cervical Spine Surgery: Arthroplasty Versus Fusion Versus Posterior Foraminotomy.

Three procedures dominate surgical management of degenerative cervical spine disorders: posterior cervical laminoforaminotomy (PCF), cervical total disc replacement (CTDR), and anterior cervical discectomy and fusion (ACDF). Together they provide a 360° approach to degenerative cervical spine disease that help surgeons reach the correct treatment decisions. ACDF, CTDR, and PCF are effective procedures for the treatment of a broad range of degenerative cervical disorders. Minimally invasive technique, outpatient setting, motion preservation, and adjacent segment disease should be taken into consideration in the surgical plan. All well-rounded spine surgeons should be skilled at both anterior and posterior approaches to treat radiculopathy.

Lagrangian betweenness as a measure of bottlenecks in dynamical systems with oceanographic examples.

The study of connectivity patterns in networks has brought novel insights across diverse fields ranging from neurosciences to epidemic spreading or climate. In this context, betweenness centrality has demonstrated to be a very effective measure to identify nodes that act as focus of congestion, or bottlenecks, in the network. However, there is not a way to define betweenness outside the network framework. By analytically linking dynamical systems and network theory, we provide a trajectory-based formulation of betweenness, called Lagrangian betweenness, as a function of Lyapunov exponents. This extends the concept of betweenness beyond the context of network theory relating hyperbolic points and heteroclinic connections in any dynamical system to the structural bottlenecks of the network associated with it. Using modeled and observational velocity fields, we show that such bottlenecks are present and surprisingly persistent in the oceanic circulation across different spatio-temporal scales and we illustrate the role of these areas in driving fluid transport over vast oceanic regions. Analyzing plankton abundance data from the Kuroshio region of the Pacific Ocean, we find significant spatial correlations between measures of diversity and betweenness, suggesting promise for ecological applications.