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Unilateral fixation for treatment of occipitocervical instability in children with congenital vertebral anomalies of the craniocervical junction

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.

In Neurosurgical Focus Volume 38 (2015): Issue 4 (Apr 2015): Craniovertebral Junction Abnormalities

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Stereotactic navigation with the O-arm for placement of S-2 alar iliac screws in pelvic lumbar fixation

Technical note

Wilson Z. Ray, Vijay M. Ravindra, Meic H. Schmidt, and Andrew T. Dailey

Object

Pelvic fixation is a crucial adjunct to many lumbar fusions to avoid L5–S1 pseudarthrosis. It is useful for treatment of kyphoscoliosis, high-grade spondylolisthesis, L5–S1 pseudarthrosis, sacral tumors, lumbosacral dislocations, and osteomyelitis. The most popular method, iliac fixation, has drawbacks including hardware prominence, extensive muscle dissection, and the need for connection devices. S-2 alar iliac fixation provides a useful primary or salvage alternative. The authors describe their techniques for using stereotactic navigation for screw placement.

Methods

The O-arm Surgical Imaging System allowed for CT-quality multiplanar reconstructions of the pelvis, and registration to a StealthStation Treon provided intraoperative guidance. The authors describe their technique for performing computer-assisted S-2 alar iliac fixation for various indications in 18 patients during an 18-month period.

Results

All patients underwent successful bilateral placement of screws 80–100 mm in length. All placements were confirmed with a second multiplanar reconstruction. One screw was moved because of apparent anterior breach of the ilium. There were no immediate neurological or vascular complications due to screw placement. The screw length required additional instruments including a longer pedicle finder and tap.

Conclusions

Stereotactic guidance to navigate the placement of distal pelvic fixation with bilateral S-2 alar iliac fixation can be safely performed in patients with a variety of pathological conditions. Crossing the sacroiliac joint, choosing trajectory, and ensuring adequate screw length can all be enhanced with 3D image guidance. Long-term outcome studies are underway, specifically evaluating the sacroiliac joint.

In Journal of Neurosurgery: Spine Volume 18 (2013): Issue 5 (May 2013)

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Rigid versus flexible neuroendoscopy: a systematic review and meta-analysis of endoscopic third ventriculostomy for the management of pediatric hydrocephalus

Daphne Li, Vijay M. Ravindra, and Sandi K. Lam

OBJECTIVE

Endoscopic third ventriculostomy (ETV), with or without choroid plexus cauterization (±CPC), is a technique used for the treatment of pediatric hydrocephalus. Rigid or flexible neuroendoscopy can be used, but few studies directly compare the two techniques. Here, the authors sought to compare these methods in treating pediatric hydrocephalus.

METHODS

A systematic MEDLINE search was conducted using combinations of keywords: “flexible,” “rigid,” “endoscope/endoscopic,” “ETV,” and “hydrocephalus.” Inclusion criteria were as follows: English-language studies with patients 2 years of age and younger who had undergone ETV±CPC using rigid or flexible endoscopy for hydrocephalus. The primary outcome was ETV success (i.e., without the need for further CSF diversion procedures). Secondary outcomes included ETV-related and other complications. Statistical significance was determined via independent t-tests and Mood’s median tests.

RESULTS

Forty-eight articles met the study inclusion criteria: 37 involving rigid endoscopy, 10 involving flexible endoscopy, and 1 propensity scored–matched comparison. A cumulative 560 patients had undergone 578 rigid ETV±CPC, and 661 patients had undergone 672 flexible ETV±CPC. The flexible endoscopy cohort had a significantly lower average age at the time of the procedure (0.33 vs 0.53 years, p = 0.001) and a lower preoperatively predicted ETV success score (median 40, IQR 32.5–57.5 vs 62.5, IQR 50–70; p = 0.033). Average ETV success rates in the rigid versus flexible groups were 54.98% and 59.65% (p = 0.63), respectively. ETV-related complication rates did not differ significantly at 0.63% for flexible endoscopy and 3.46% for rigid endoscopy (p = 0.30). There was no significant difference in ETV success or complication rate in comparing ETV, ETV+CPC, and ETV with other concurrent procedures.

CONCLUSIONS

Despite the lower expected ETV success scores for patients treated with flexible endoscopy, the authors found similar ETV success and complication rates for ETV±CPC with flexible versus rigid endoscopy, as reported in the literature. Further direct comparison between the techniques is necessary.

In Journal of Neurosurgery: Pediatrics Volume 28: Issue 4 (Oct 2021)

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Cost effectiveness of subaxial fusion—lateral mass screws versus transarticular facet screws

Wilson Z. Ray, Vijay M. Ravindra, Gregory F. Jost, Erica F. Bisson, and Meic H. Schmidt

As health care reform continues to evolve, demonstrating the cost effectiveness of spinal fusion procedures will be of critical value. Posterior subaxial cervical fusion with lateral mass screw and rod instrumentation is a well-established fixation technique. Subaxial transarticular facet fixation is a lesser known fusion technique that has been shown to be biomechanically equivalent to lateral mass screws for short constructs. Although there has not been a widespread adoption of transarticular facet screws, the screws potentially represent a cost-effective alternative to lateral mass rod and screw constructs. In this review, the authors describe an institutional experience with the use of lateral mass screws and provide a theoretical cost comparison with the use of transarticular facet screws.

In Neurosurgical Focus Volume 33 (2012): Issue 1 (Jul 2012)

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Primary osseous tumors of the pediatric spinal column: review of pathology and surgical decision making

Vijay M. Ravindra, Ilyas M. Eli, Meic H. Schmidt, and Douglas L. Brockmeyer

Spinal column tumors are rare in children and young adults, accounting for only 1% of all spine and spinal cord tumors combined. They often present diagnostic and therapeutic challenges. In this article, the authors review the current management of primary osseous tumors of the pediatric spinal column and highlight diagnosis, management, and surgical decision making.

In Neurosurgical Focus Volume 41 (2016): Issue 2 (Aug 2016): Tumors of the Spinal Column

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Defining a new neurosurgical complication classification: lessons learned from a monthly Morbidity and Mortality conference

Yair M. Gozal, Erinç Aktüre, Vijay M. Ravindra, Jonathan P. Scoville, Randy L. Jensen, William T. Couldwell, and Philipp Taussky

OBJECTIVE

The absence of a commonly accepted standardized classification system for complication reporting confounds the recognition, objective reporting, management, and avoidance of perioperative adverse events. In the past decade, several classification systems have been proposed for use in neurosurgery, but these generally focus on tallying specific complications and grading their effect on patient morbidity. Herein, the authors propose and prospectively validate a new neurosurgical complication classification based on understanding the underlying causes of the adverse events.

METHODS

A new complication classification system was devised based on the authors’ previous work on morbidity in endovascular surgery. Adverse events were prospectively compiled for all neurosurgical procedures performed at their tertiary care academic medical center over the course of 1 year into 5 subgroups: 1) indication errors; 2) procedural errors; 3) technical errors; 4) judgment errors; and 5) critical events. The complications were presented at the monthly institutional Morbidity and Mortality conference where, following extensive discussion, they were assigned to one of the 5 subgroups. Additional subgroup analyses by neurosurgical subspecialty were also performed.

RESULTS

A total of 115 neurosurgical complications were observed and analyzed during the study period. Of these, nearly half were critical events, while technical errors accounted for approximately one-third of all complications. Within neurosurgical subspecialties, vascular neurosurgery (36.5%) had the most complications, followed by spine & peripheral nerve (21.7%), neuro-oncology (14.8%), cranial trauma (13.9%), general neurosurgery (12.2%), and functional neurosurgery (0.9%).

CONCLUSIONS

The authors’ novel neurosurgical complication classification system was successfully implemented in a prospective manner at their high-volume tertiary medical center. By employing the well-established Morbidity and Mortality conference mechanism, this simple system may be easily applied at other neurosurgical centers and may allow for uniform analyses of perioperative morbidity and the introduction of corrective initiatives.

In Journal of Neurosurgery Volume 132: Issue 1 (Jan 2020)

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Development and initial evaluation of a finite element model of the pediatric craniocervical junction

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.

In Journal of Neurosurgery: Pediatrics Volume 17 (2016): Issue 4 (Apr 2016)

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Risk factors for traumatic blunt cerebrovascular injury diagnosed by computed tomography angiography in the pediatric population: a retrospective cohort study

Vijay M. Ravindra, Jay Riva-Cambrin, Walavan Sivakumar, Ryan R. Metzger, and Robert J. Bollo

OBJECT

Computed tomography angiography (CTA) is frequently used to examine patients for blunt cerebrovascular injury (BCVI) after cranial trauma, but the pediatric population at risk for BCVI is poorly defined. Although CTA is effective for BCVI screening in adults, the increased lifetime risk for malignant tumors associated with this screening modality warrants efforts to reduce its use in children. The authors' objective was to evaluate the incidence of BCVI diagnosed by CTA in a pediatric patient cohort and to create a prediction model to identify children at high risk for BCVI.

METHODS

Demographic, clinical, and radiographic data were collected retrospectively for pediatric patients who underwent CTA during examination for traumatic cranial injury from 2003 through 2013. The primary outcome was injury to the carotid or vertebral artery diagnosed by CTA.

RESULTS

The authors identified 234 patients (mean age 8.3 years, range 0.04–17 years, 150 [64%] boys) who underwent CTA screening for BCVI. Of these, 24 (10.3%) had a focal neurological deficit, and 153 (65.4%) had intracranial hemorrhage on a head CTA. Thirty-seven BCVIs were observed in 36 patients (15.4%), and 16 patients (6.8%) died. Multivariate regression analysis identified fracture through the carotid canal, petrous temporal bone fracture, Glasgow Coma Scale (GCS) score of < 8, focal neurological deficit, and stroke on initial CT scan as independent risk factors for BCVI. A prediction model for identifying children at high risk for BCVI was created. A score of ≤ 2 yielded a 7.9% probability of BCVI and a score of ≥ 3 a risk of 39.3% for BCVI.

CONCLUSIONS

For cranial trauma in children, fracture of the petrous temporal bone or through the carotid canal, focal neurological deficit, stroke, and a GCS score of < 8 are independent risk factors for BCVI.

In Journal of Neurosurgery: Pediatrics Volume 15 (2015): Issue 6 (Jun 2015)

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Chiari-related scoliosis: a single-center experience with long-term radiographic follow-up and relationship to deformity correction

Vijay M. Ravindra, Kaine Onwuzulike, Robert S. Heller, Robert Quigley, John Smith, Andrew T. Dailey, and Douglas L. Brockmeyer

OBJECTIVE

Previous reports have addressed the short-term response of patients with Chiari-related scoliosis (CRS) to suboccipital decompression and duraplasty (SODD); however, the long-term behavior of the curve has not been well defined. The authors undertook a longitudinal study of a cohort of patients who underwent SODD for CRS to determine whether there are factors related to Chiari malformation (CM) that predict long-term scoliotic curve behavior and need for deformity correction.

METHODS

The authors retrospectively reviewed cases in which patients underwent SODD for CRS during a 14-year period at a single center. Clinical (age, sex, and associated disorders/syndromes) and radiographic (CM type, tonsillar descent, pBC2 line, clival-axial angle [CXA], syrinx length and level, and initial Cobb angle) information was evaluated to identify associations with the primary outcome: delayed thoracolumbar fusion for progressive scoliosis.

RESULTS

Twenty-eight patients were identified, but 4 were lost to follow-up and 1 underwent fusion within a year. Among the remaining 23 patients, 11 required fusion surgery at an average of 88.3 ± 15.4 months after SODD, including 7 (30%) who needed fusion more than 5 years after SODD. On univariate analysis, a lower CXA (131.5° ± 4.8° vs 146.5° ± 4.6°, p = 0.034), pBC2 > 9 mm (64% vs 25%, p = 0.06), and higher initial Cobb angle (35.1° ± 3.6° vs 22.8° ± 4.0°, p = 0.035) were associated with the need for thoracolumbar fusion. Multivariable modeling revealed that lower CXA was independently associated with a need for delayed thoracolumbar fusion (OR 1.12, p = 0.0128).

CONCLUSIONS

This investigation demonstrates the long-term outcome and natural history of CRS after SODD. The durability of the effect of SODD on CRS and curve behavior is poor, with late curve progression occurring in 30% of patients. Factors associated with CRS progression include an initial pBC2 > 9 mm, lower CXA, and higher Cobb angle. Lower CXA was an independent predictor of delayed thoracolumbar fusion. Further study is necessary on a larger cohort of patients to fully elucidate this relationship.

In Journal of Neurosurgery: Pediatrics Volume 21 (2018): Issue 2 (Feb 2018)

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Rapid de novo aneurysm formation after clipping of a ruptured middle cerebral artery aneurysm in an infant with an MYH11 mutation

Vijay M. Ravindra, Michael Karsy, Richard H. Schmidt, Philipp Taussky, Min S. Park, and Robert J. Bollo

The authors report the case of a previously healthy 6-month-old girl who presented with right arm and leg stiffening consistent with seizure activity. An initial CT scan of the head demonstrated acute subarachnoid hemorrhage in the basal cisterns extending into the left sylvian fissure. Computed tomography angiography demonstrated a 7 × 6 × 5–mm saccular aneurysm of the inferior M2 division of the left middle cerebral artery. The patient underwent left craniotomy and microsurgical clip ligation with wrapping of the aneurysm neck because the vessel appeared circumferentially dysplastic in the region of the aneurysm. Postoperative angiography demonstrated a small remnant, sluggish distal flow, but no significant cerebral vasospasm. Fifty-five days after the initial aneurysm rupture, the patient presented again with an acute intraparenchymal hemorrhage of the left anterior temporal lobe. Angiogram revealed a circumferentially dysplastic superior division of the M2 branch, with a new 5 × 4–mm saccular aneurysm distinct from the first, with 2 smaller aneurysms distal to the new ruptured aneurysm. Endovascular parent vessel occlusion with Onyx was performed. Genetic testing revealed a mutation of the MYH11. To the authors' knowledge, this is the first report of rapid de novo aneurysm formation in an infant with an MYH11 mutation. The authors review the patient's clinical presentation and management and comprehensively review the literature on this topic.

In Journal of Neurosurgery: Pediatrics Volume 18 (2016): Issue 4 (Oct 2016)