Mauricio J. Avila

Freehand Thoracic Pedicle Screw Placement: Review of Existing Strategies and a Step-by-Step Guide Using Uniform Landmarks for All Levels

Pedicle screw fixation in the thoracic spine presents certain challenges due to the critical regional neurovascular anatomy as well as the narrow pedicular corridor that typically exists. With increased awareness of the dangers of intraoperative radiation, the ability to place pedicle screws with anatomic landmarks alone is paramount. In this study, we reviewed the literature from 1990 to 2015 for studies that included freehand pedicle screw placement in the thoracic spine with special emphasis on entry points and the trajectories of the screws. We excluded studies that used fluoroscopy guidance, navigation techniques, cadaveric and biomechanical articles, case reports, and experimental studies on animals. The search retrieved 40 articles, and after careful selection, seven articles were analyzed. Over 8,000 screws were placed in the different studies. The mean accuracy for placement of the thoracic screws was 93.3%. However, there is little consensus between studies in entry points, sagittal, and axial trajectories of the screws. We complete this review by presenting our step-by-step technique for the placement of freehand pedicle screws in the thoracic spine.

Posterior atlantoaxial fixation: A cadaveric and fluoroscopic step-by-step technical guide.

Background: Atlantoaxial surgical fixation is widely employed treatment strategy for a myriad of pathologies affecting the stability of the atlantoaxial joint. The most common technique used in adults, and in certain cases in children, involves a posterior construct with C1 lateral mass screws, and C2 pars or pedicle screws. This technical note aims to provide a step-by-step guide to this procedure using cadaveric and fluoroscopic images. Methods: An embalmed, human, cadaveric, specimen was used for this study. The subject did not have obvious occipital-cervical pathology. Dissections and techniques were performed to mimic actual surgical technique. Photographs were taken during each step, and the critical aspects of each step were highlighted. Fluoroscopic images from a real patient undergoing C1/C2 fixation were also utilized to further highlight the anatomic-radiographic relationships. This study was performed without external or industry funding. Results: Photographic and radiographic pictures and drawings are presented to illustrate the pertinent anatomy and technical aspects of this technique. The nuances of each step, including complication avoidance strategies are also highlighted. Conclusions: Given the widespread utilization of this technique, described step-by-step guide is timely for surgeons and trainees alike.

Posterior longitudinal ligament resection or preservation in anterior cervical decompression surgery

We reviewed the literature to determine differences in clinical outcomes for the removal or preservation of the posterior longitudinal ligament (PLL) in anterior cervical discectomy and fusion (ACDF). The outcomes are surgeon and case-dependent for both practices. A literature review was performed in PubMed from the years 1960 to 2014 to identify studies describing surgeries where the PLL was removed or preserved during ACDF. Searches were performed using Medical Subject Headings (MeSH) and references included in the reviewed articles were also considered. Additionally we searched recent articles that cited those from the original search. The search yielded 79 articles and 115 pertinent citations. These 194 articles were reviewed for specific discussions of PLL resection or preservation. Four articles containing 122 patients were included in the final analysis. In 69 patients the PLL was removed and in 53 the PLL was preserved. Both groups improved in clinical scores during follow up. One patient in the PLL removal group had a cerebrospinal fluid leak. MRI and correlative outcome data suggest that a non-ossified PLL itself does not contribute to significant cord compression. Postoperative MRI of patients with the PLL removed showed a larger spinal cord diameter. Resection of the PLL is safe and common in ACDF surgery but there does not appear to be a demonstrable clinical difference in patients where it is resected. The ultimate decision is likely surgeon and case-dependent. Randomized trials could further determine the importance of PLL removal in ACDF treated patients.

Anatomic considerations of the anterior upper cervical spine during decompression and instrumentation: A cadaveric based study

We evaluated the anatomical considerations specific to the high anterior retropharyngeal approach to the cervical spine. Surgical exposure of the anterior upper cervical spine can sometimes be challenging due to the surrounding neurovascular structures. Using three adult cadavers, we performed high anterior retropharyngeal cervical dissection of the left and right side for a total of six approaches (six sides). During the dissection, all important neurovascular elements were noted and photographed, and anatomical relationships to the spinal vertebral bodies and disc spaces were analyzed. There are certain anatomic considerations that are unique to the high anterior cervical spine. The unique structures include the hypoglossal nerve and the superior thyroid artery/nerve. Only the superior thyroid artery in this region has numerous anatomical variations. Awareness of other structures, including the carotid artery, recurrent laryngeal nerve, and esophagus also remains important. Awareness of the anatomical structures in the anterior upper cervical spine is essential for performing safe anterior upper cervical spinal surgery, avoiding serious complications.

Combined posterior hemiosteotomies and stabilization with lateral thoracotomy for en bloc resection of thoracic paraspinal primary bone tumors: technical note

Primary bone tumors of the spine are rare entities with a poor prognosis if left untreated. En bloc excision is the preferred surgical approach to minimize the rate of recurrence. Paraspinal primary bone tumors are even less common. In this technical note the authors present an approach to the en bloc resection of primary bone tumors of the paraspinal thoracic region with posterior vertebral body hemiosteotomies and lateral thoracotomy. They also describe 2 illustrative cases.

Letter: Rerupture of a Blister Aneurysm After Treatment With a Single Flow-Diverting Stent

To the Editor: We read the recent article by Mazur et al1 with great interest; in this article, the authors described the case of a 29-year-old male who presented with a ruptured internal carotid artery blisterlike aneurysm treated with a single Pipeline Flex (Medtronic, Dublin, Ireland), complicated by aneurysm rupture postoperatively. This report perfectly exemplifies the challenges faced by vascular neurosurgeons in the treatment of blister aneurysms. Despite tremendous advances in microsurgical and endovascular techniques, blister aneurysms still lack a failsafe treatment option.

Instability in Thoracolumbar Trauma: Is a New Definition Warranted?

Study Design: Review of the articles. Objective: The objective of this study was to review all articles related to spinal instability to determine a consensus statement for a contemporary, practical definition applicable to thoracolumbar injuries. Summary of Background Data: Traumatic fractures of the thoracolumbar spine are common. These injuries can result in neurological deficits, disability, deformity, pain, and represent a great economic burden to society. The determination of spinal instability is an important task for spine surgeons, as treatment strategies rely heavily on this assessment. However, a clinically applicable definition of spinal stability remains elusive. Materials and Methods: A review of the Medline database between 1930 and 2014 was performed limited to papers in English. Spinal instability, thoracolumbar, and spinal stability were used as search terms. Case reports were excluded. We reviewed listed references from pertinent search results and located relevant manuscripts from these lists as well. Results: The search produced a total of 694 published articles. Twenty-five articles were eligible after abstract screening and underwent full review. A definition for spinal instability was described in only 4 of them. Definitions were primarily based on biomechanical and classification studies. No definitive parameters were outlined to define stability. Conclusions: Thirty-six years after White and Panjabi’s original definition of instability, and many classification schemes later, there remains no practical and meaningful definition for spinal instability in thoracolumbar trauma. Surgeon expertise and experience remains an important factor in stability determination. We propose that, at an initial assessment, a distinction should be made between immediate and delayed instability. This designation should better guide surgeons in decision making and patient counseling.

Peribrachiocephalic approaches to the anterior cervicothoracic spine

This cadaveric study aims to reexamine the corridors to the anterior cervicothoracic junction, relative to the left brachiocephalic vein, and to present these working corridors as either supra- or infra-brachiocephalic. The anterior cervicothoracic junction incorporates the seventh cervical vertebrae through the fourth thoracic vertebrae (C7-T4) and involves critical anatomical structures. Operative approaches to this area are well described in the literature, with the predominant implementation of three surgical corridors. We used three embalmed, human, cadaveric specimens for this study. No pathology involving the cervicothoracic junction was noted. While dissecting, we tried to imitate the actual surgery. For each surgical step, photographs were taken, drawing attention to the critical structures and highlighting the different corridors to the spine relative to the left brachiocephalic vein. It is possible to access the cervicothoracic junction relative to the brachiocephalic vein from the left. The supra-brachiocephalic approach gives access to the C7-T4 vertebrae, whereas if T4-T5 is the goal, the infra-brachiocephalic approach may be utilized. In the supra-brachiocephalic approach, the brachiocephalic artery can be either medialized or lateralized as needed. A re-examination of the anterior cervicothoracic junction anatomy has allowed us to classify approaches relative to the left brachiocephalic vein. Identifying and understanding the approaches relative to this structure will assist in safe and effective spinal surgery in this area.

90-day Readmission after Lumbar Spinal Fusion Surgery in New York State between 2005 and 2014–a 10-year Analysis of a Statewide Cohort

Study Design. Retrospective cohort study. Objective. The aim of this study was to assess 90-day readmission and evaluate risk factors associated with readmission after lumbar fusion in New York State. Summary of Background Data. Readmission is becoming an important metric for quality and efficiency of health care. Readmission and its predictors following spine surgery are overall poorly understood and limited evidence is available specifically in lumbar fusion. Methods. The New York Statewide Planning and Research Cooperative System (SPARCS) was utilized to capture patients undergoing lumbar fusion from 2005 to 2014. Temporal trend of 90-day readmission was assessed using Cochran-Armitage test. Logistic regression was used to examine predictors associated with 90-day readmission. Results. There were 86,869 patients included in this cohort study. The overall 90-day readmission rate was 24.8%. On a multivariable analysis model, age (odds ratio [OR] comparing ≥75 versus <35 years: 1.24, 95% confidence interval [CI]: 1.13–1.35), sex (OR female to male: 1.19, 95% CI: 1.15–1.23), race (OR African-American to white: 1.60, 95% CI: 1.52–1.69), insurance (OR Medicaid to Medicare: 1.42, 95% CI: 1.33–1.53), procedure (OR comparing thoracolumbar fusion, combined [International Classification of Disease, Ninth Revision, ICD-9: 81.04] to posterior lumbar interbody fusion/transforaminal lumbar spinal fusion [ICD-9: 81.08]: 2.10, 95% CI: 1.49–2.97), number of operated spinal levels (OR comparing four to eight vertebrae to two to three vertebrae: 2.39, 95% CI: 2.07–2.77), health service area ([HSA]; OR comparing Finger Lakes to New York-Pennsylvania border: 0.67, 95% CI: 0.61-0.73), and comorbidity, i.e., coronary artery disease (OR: 1.26, 95% CI: 1.19–1.33) were significantly associated with 90-day readmission. Directions of the odds ratios for these factors were consistent after stratification by procedure type. Conclusion. Age, sex, race, insurance, procedure, number of operated spinal levels, HSA, and comorbidities are major risk factors for 90-day readmission. Our study allows risk calculation to determine high-risk patients before undergoing spinal fusion surgery to prevent early readmission, improve quality of care, and reduce health care expenditures. Level of Evidence: 3

Recovery of consciousness after a brainstem cavernous malformation hemorrhage: A descriptive study of preserved reticular activating system with tractography

The aim of this study is to describe the imaging features, the relevant anatomy, and the fractional anisotropy (FA) values in diffusion tensor tractography (DTT) of the ascending reticular activating system (ARAS) fiber tracts in 2 patients who recovered from initial altered consciousness after presenting with a brainstem cavernous malformation (BSCM) hemorrhage. A DTT was performed in 2 patients with impaired consciousness after a brainstem cavernous malformation hemorrhage. A 1.5 T scanner was used to obtain the axial tensors. Post-processing was performed and the mean FA values were recorded. The FA maps were used to seed the following regions of interest: the ventromedial midbrain, the anterior thalamus bilaterally, and the hypothalamus bilaterally. The first case presented with posterior displacement of the dorsal raphè fiber tracts, with preservation of all the ascending reticular activating fiber tracts and spontaneous recovery of consciousness after 20 days. The second case presented with no destruction but also had posterior displacement of the inferior dorsal raphè fiber tracts, with recovery of consciousness 1 month after resection surgery. Described in this study are affected fibers of the ARAS, as well as the FA value abnormalities in 2 patients, with recovery of a transient disorder of consciousness after a BSCM hemorrhage.