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Marcus D. Mazur, Aaron Cutler, William T. Couldwell and Philipp Taussky

Meningiomas that invade the transverse or sigmoid sinuses are uncommon tumors that are challenging to treat surgically. Although the risk of recurrence is associated with the extent of resection, complete removal of meningiomas in these locations must be balanced with avoidance of venous outflow obstruction, which could cause venous infarction and significant neurological consequences. When a meningioma occludes a venous sinus completely, gross-total resection of the intravascular portion is commonly performed. When the tumor invades but does not completely obliterate a major venous sinus, however, opinions differ on whether to accept a subtotal resection or to open the sinus, perform a complete resection, and reconstruct the venous outflow tract. In this paper, the authors review the different strategies used to treat these lesions and provide illustrative case examples.

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Marcus D. Mazur, Vijay M. Ravindra and Douglas L. Brockmeyer

OBJECT

Patients with occipitocervical (OC) instability from congenital vertebral anomalies (CVAs) of the craniocervical junction (CCJ) often have bony abnormalities that make instrumentation placement difficult. Within this patient population, some bilateral instrumentation constructs either fail or are not feasible, and a unilateral construct must be used. The authors describe the surgical management and outcomes of this disorder in patients in whom unilateral fixation constructs were used to treat OC instability.

METHODS

From a database of OC fusion procedures, the authors identified patients who underwent unilateral fixation for the management of OC instability. Patient characteristics, surgical details, and radiographic outcomes were reviewed. In each patient, CT scans were performed at least 4 months after surgery to evaluate for fusion.

RESULTS

Eight patients with CVAs of the CCJ underwent unilateral fixation for the treatment of OC instability. For 4 patients, the procedure occurred after a bilateral OC construct failed or infection forced hardware removal. For the remainder, it was the primary procedure. Two patients required reoperation for hardware revision and 1 developed nonunion requiring revision of the bone graft. Ultimately, 7 patients demonstrated osseous fusion on CT scans and 1 had a stable fibrous union.

CONCLUSIONS

These findings demonstrate that a unilateral OC fixation is effective for the treatment of OC instability in children with CVAs of the CCJ in whom bilateral screw placement fails or is not feasible.

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Marcus D. Mazur, Michael L. Mumert, Erica F. Bisson and Meic H. Schmidt

Anterior screw fixation of Type II odontoid fractures provides immediate stabilization of the cervical spine while preserving C1–2 motion. This technique has a high fusion rate, but can be technically challenging. The authors identify key points that should be taken into account to maximize the chance for a favorable outcome. Keys to success include proper patient and fracture selection, identification of suitable screw entry point and correct screw trajectory, achieving bicortical purchase, and placing 2 screws when feasible and applicable. The authors review the operative technique and present guidance on appropriate patient selection and common pitfalls in anterior screw fixation, with strategies for avoiding complications.

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Rinchen Phuntsok, Marcus D. Mazur, Benjamin J. Ellis, Vijay M. Ravindra and Douglas L. Brockmeyer

OBJECT

There is a significant deficiency in understanding the biomechanics of the pediatric craniocervical junction (CCJ) (occiput–C2), primarily because of a lack of human pediatric cadaveric tissue and the relatively small number of treated patients. To overcome this deficiency, a finite element model (FEM) of the pediatric CCJ was created using pediatric geometry and parameterized adult material properties. The model was evaluated under the physiological range of motion (ROM) for flexion-extension, axial rotation, and lateral bending and under tensile loading.

METHODS

This research utilizes the FEM method, which is a numerical solution technique for discretizing and analyzing systems. The FEM method has been widely used in the field of biomechanics. A CT scan of a 13-month-old female patient was used to create the 3D geometry and surfaces of the FEM model, and an open-source FEM software suite was used to apply the material properties and boundary and loading conditions and analyze the model. The published adult ligament properties were reduced to 50%, 25%, and 10% of the original stiffness in various iterations of the model, and the resulting ROMs for flexion-extension, axial rotation, and lateral bending were compared. The flexion-extension ROMs and tensile stiffness that were predicted by the model were evaluated using previously published experimental measurements from pediatric cadaveric tissues.

RESULTS

The model predicted a ROM within 1 standard deviation of the published pediatric ROM data for flexion-extension at 10% of adult ligament stiffness. The model's response in terms of axial tension also coincided well with published experimental tension characterization data. The model behaved relatively stiffer in extension than in flexion. The axial rotation and lateral bending results showed symmetric ROM, but there are currently no published pediatric experimental data available for comparison. The model predicts a relatively stiffer ROM in both axial rotation and lateral bending in comparison with flexion-extension. As expected, the flexion-extension, axial rotation, and lateral bending ROMs increased with the decrease in ligament stiffness.

CONCLUSIONS

An FEM of the pediatric CCJ was created that accurately predicts flexion-extension ROM and axial force displacement of occiput–C2 when the ligament material properties are reduced to 10% of the published adult ligament properties. This model gives a reasonable prediction of pediatric cervical spine ligament stiffness, the relationship between flexion-extension ROM, and ligament stiffness at the CCJ. The creation of this model using open-source software means that other researchers will be able to use the model as a starting point for research.

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Marcus D. Mazur, Sara McEvoy, Meic H. Schmidt and Erica F. Bisson

OBJECT

Patient satisfaction scores have become a common metric for health care quality. Because satisfaction scores are right-skewed, even small differences in mean scores can have a large impact. Little information, however, is available on the specific factors that play a role in satisfaction in patients with spinal disorders. The authors investigated whether disability severity and the surgeon's recommendation for or against surgical intervention were associated with patient satisfaction scores.

METHODS

The authors conducted a retrospective cohort study involving adult patients who were referred to a spine surgeon for an outpatient evaluation of back pain. Patients completed the Oswestry Disability Index (ODI) before their clinic appointment and a Press Ganey patient satisfaction survey after their visit. Patients were grouped by self-assessed disability severity: mild to moderate (ODI < 40%) and severe (≥ 40%). Satisfaction scores were graded from 0 (very poor) to 100 (very good). Nonparametric tests were used to evaluate the association between patient satisfaction and current disability self-assessment. The authors also investigated whether the surgeon's recommendation against surgery negatively affected patient satisfaction.

RESULTS

One hundred thirty patients completed the ODI questionnaire before and satisfaction surveys after seeing a spine surgeon for a new outpatient back pain consultation. Of these, 68 patients had severe disability, 62 had mild to moderate disability, 67 received a recommendation for surgery, and 63 received a recommendation against surgery. Composite satisfaction scores were lower among patients who had severe disability than among those with mild to moderate disability (median [interquartile range]: 91.7 [83.7–96.4] vs 95.8 [91.0–99.3], respectively; p = 0.0040). Patients who received a recommendation against surgery reported lower satisfaction scores than those who received a recommendation for surgery (91.7 [83.5–95.8] vs 95.8 [88.5–99.8]; p = 0.0059).

CONCLUSIONS

High self-assessment of disability and a surgeon's recommendation against surgical intervention are associated with lower satisfaction scores in patients with spinal disorders.

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Marcus D. Mazur, Walavan Sivakumar, Jay Riva-Cambrin, Jaes Jones and Douglas L. Brockmeyer

Object

Surgical arthrodesis for pediatric occipitocervical (OC) instability has a high rate of success in a wide variety of challenging circumstances; however, identifying potential risk factors can help to target variables that should be the focus of improvement. The aim of this paper was to examine risk factors predictive of failure in a population of patients who underwent instrumented OC arthrodesis using a uniform surgical philosophy.

Methods

The authors conducted a retrospective cohort study of pediatric patients who underwent OC fusion from 2001 to 2013 at a single institution to determine risk factors for surgical failure, defined as reoperation for revision of the arthrodesis or instrumentation. The primary study outcome was either radiographic confirmation of successful OC fusion or surgical failure requiring revision of the arthrodesis or instrumentation. The secondary outcome was the underlying cause of failure (hardware failure, graft failure, or infection). Univariate analysis was performed to assess the association between outcome and patient demographics, cause of OC instability, type of OC instrumentation, bone graft material, biological adjuncts, and complications.

Results

Of the 127 procedures included, 20 (15.7%) involved some form of surgical failure and required revision surgery. Univariate analysis revealed that patients with deep wound infections requiring debridement were more likely to require surgical revision of the hardware or graft (p = 0.002). Subgroup analysis revealed that patients with skeletal dysplasia or congenital spinal anomalies were more likely to develop hardware failure than patients with other causes of OC instability (p = 0.020). Surgical failure was not associated with the method of C-2 fixation, type of rigid OC instrumentation, bone graft material, use of bone morphogenetic protein or biological adjuncts, cause of instability, sex, age, or having previous OC fusion operations.

Conclusions

Pediatric patients in the present cohort with postoperative wound infections requiring surgical debridement had higher surgical failure rates after OC fusion. Those with skeletal dysplasia and congenital spinal anomalies were more likely to require reoperation for hardware failure. Better understanding of the mode of surgical failure may enable surgeons to develop strategies to decrease the need for reoperation in pediatric patients with OC instability.

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Marcus Mazur, Gregory F. Jost, Meic H. Schmidt and Erica F. Bisson

Object

Anterior decompression is an effective way to treat cervical myelopathy associated with ossification of the posterior longitudinal ligament (OPLL); however, this approach is associated with an increased risk of a dural tear and resultant CSF leak because fusion of the dura with the ossified PLL is common in these cases. The authors review the literature and present an algorithm for treatment of CSF leaks in these patients.

Methods

A MEDLINE review was performed to identify papers related to CSF leak after anterior decompression for OPLL, and data were summarized to identify treatment options for various situations. A treatment algorithm was identified based on these findings and the experience of the authors.

Results

Eleven studies were identified that presented data on intra- and postoperative management of a CSF leak during ventral surgery for OPLL. The incidence of cervical dural tears and CSF leaks after anterior decompression procedures for OPLL ranged from 4.3% to 32%. Techniques including preventative measures, intraoperative dural repair with various materials, and postoperative drainage or shunt placement have all been used.

Conclusions

Although direct dural repair is the preferred treatment for CSF leak, this technique is not always technically possible. In these cases, intraoperative adjuncts in combination with postoperative measures can be used to decrease the pressure gradient across the dural tear.

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Vijay M. Ravindra, Jayson A. Neil, Marcus D. Mazur, Min S. Park, William T. Couldwell and Philipp Taussky

The craniocervical junction (CCJ) functions within a complicated regional anatomy necessary to protect and support vital neurovascular structures. In select instances, vascular pathology can be attributed to this complicated interplay of motion and structure found within this narrow space. The authors report 3 cases of complex vascular pathology related to motion at the CCJ and detail the management of these cases. Two cases involved posterior circulation vascular compression syndromes, and one case involved a vascular anomaly and its relation to aneurysm formation and rupture. The patient in Case 1 was a 66-year-old man with a history of syncopal episodes resulting from the bilateral vertebral artery becoming occluded when he rotated his head. Successful microsurgical decompression at the skull base resulted in patent bilateral vertebral artery V3 segments upon head movement in all directions. The patient in Case 2 was a 53-year-old woman who underwent elective resection of a right temporal meningioma and who experienced postoperative drowsiness, dysphagia, and mild right-arm ataxia. Subsequent MRI demonstrated bilateral posterior inferior cerebel-lar artery (PICA) strokes. Cerebral angiography showed a single PICA, of extradural origin, supplying both cerebellar hemispheres. The PICA exhibited dynamic extradural compression when the patient rotated her head; the bilateral PICA strokes were due to head rotation during surgical positioning. In Case 3, a 37-year-old woman found unconscious in her home had diffuse subarachnoid hemorrhage and evidence of a right PICA aneurysm. A right far-lateral craniectomy was performed for aneurysm clipping, and she was found to have a dissecting aneurysm with an associated PICA originating extradurally. There was a shearing phenomenon of the extradural PICA along the dura of the foramen magnum, and this microtraumatic stress imposed on the vessel resulted in a dissecting aneurysm. This series of complex and unusual cases highlights the authors’ understanding of vascular pathology of the CCJ and its management.

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Marcus D. Mazur, Vijay M. Ravindra, Meic H. Schmidt, Darrel S. Brodke, Brandon D. Lawrence, Jay Riva-Cambrin and Andrew T. Dailey

OBJECT

S-2 alar-iliac (S2AI) screws are an attractive alternative to conventional fixation with iliac bolts because they are lower profile, require less muscle dissection, and have greater pullout strength. Few studies, however, compare outcomes between these techniques.

METHODS

The authors conducted a retrospective cohort study of consecutive adult patients at a single institution from December 2009 to March 2012 who underwent lumbopelvic fixation using S2AI screws or iliac bolts. Medical records were reviewed for patients with clinical failure, defined as an unplanned reoperation because of instrumentation failure and/or wound-related complications. Univariate, multivariate, and survival analyses were used to compare patients who required reoperation with those who did not. Method of pelvic fixation was the main predictor variable of interest, and the authors adjusted for potential confounding risk factors.

RESULTS

Of the 60 patients included, 23 received S2AI screws. Seventeen patients (28%) underwent an osteotomy. The mean follow-up was 22 months. A Kaplan-Meier survival model was used to evaluate the time to reoperation from the initial placement of lumbopelvic instrumentation. The failure-free rate was 96.6% at 6 months, 87.0% at 1 year, and 73.5% at 2 years. Reoperation was more common in patients with iliac bolts than in those with S2AI screws (13 vs 2; p = 0.031). Univariate analysis identified potential risk factors for unplanned reoperation, including use of iliac bolts (p = 0.031), absence of L5–S1 interbody graft (p = 0.048), previous lumbar fusion (p = 0.034), and pathology other than degenerative disease or scoliosis (p = 0.034). After adjusting for other risk factors, multivariate analysis revealed that the use of S2AI screws (OR 8.1 [1.5–73.5]; p = 0.030) was the only independent predictor for preventing unplanned reoperation.

CONCLUSIONS

Both S2AI screws and iliac bolts were effective at improving fusion rates at the lumbosacral junction. The use of S2AI screws, however, was independently associated with fewer unplanned reoperations for wound-related complications and instrumentation failures than the use of iliac bolts.

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Julius Griauzde, Vijay M. Ravindra, Neeraj Chaudhary, Joseph J. Gemmete, Marcus D. Mazur, Christopher D. Roark, William T. Couldwell, Min S. Park, Philipp Taussky and Aditya S. Pandey

OBJECTIVE

Flow-diverting devices have been used for the treatment of complex intracranial vascular pathology with success, but the role of these devices in treating iatrogenic intracranial vascular injuries has yet to be clearly defined. Here, the authors report their bi-institutional experience with the use of the Pipeline embolization device (PED) for the treatment of iatrogenic intracranial vascular injuries.

METHODS

The authors reviewed a retrospective cohort of patients with iatrogenic injuries to the intracranial vasculature that were treated with the PED between 2012 and 2016. Data collection included demographic data, indications for treatment, number and sizes of PEDs used, and immediate and follow-up angiographic and clinical outcomes.

RESULTS

Four patients with a mean age of 47.5 years (range 18–63 years) underwent PED placement for iatrogenic vessel injuries. In 3 patients, the intracranial internal carotid artery (ICA) was injured during transnasal tumor resection. In 1 patient, a basilar apex injury occurred during endoscopic third ventriculostomy. Three patients had a pseudoaneurysm as a result of vessel injury, and 1 patient had frank ICA laceration and extravasation. All 3 pseudoaneurysms were successfully treated with PED deployment. The ICA laceration was refractory to PED placement, and the vessel was subsequently occluded endovascularly. All 4 patients had a good clinical outcome (modified Rankin Scale score of 0 or 1).

CONCLUSIONS

The use of the PED is feasible in the management of iatrogenic pseudoaneurysms of the intracranial vasculature. In cases of frank vessel perforation, an alternative strategy such as covered stent placement should be considered. Endovascular or surgical vessel occlusion remains the definitive treatment in cases of refractory hemorrhage.