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Gazanfar Rahmathulla and H. Gordon Deen

The past 2 decades have seen a considerable increase in the number of lumbar spinal fusion surgeries. To enhance spinal stabilization and fusion, make the construct resistant to or stiffer for axial stress loading, lateral bending, and torsional stresses, cross-links and connectors were designed and included in a rod-screw construct. The authors present the case of a 49-year-old woman who presented 11 years after undergoing an L4–5 decompression and fusion in which a pedicle screw-rod construct with an integrated cross-link was designed to attach onto the pedicle screws. The patient's response at the time to the initial surgery was excellent; however, at the time of presentation 11 years later, she had significant postural headaches, severe neurogenic claudication, and radiculopathy. Imaging revealed canal compression across the instrumented levels and a possible thickened adherent filum terminale. Reexploration of the level revealed a large erosive dural defect with a CSF leak, spinal canal compression, and a thickened filum at the level of the cross-link. To the author's knowledge, such complications have not been reported in literature. The authors discuss this rare complication of spinal fusion and the need to avoid dural compression when cross-links are used.

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Gazanfar Rahmathulla, Eric W. Nottmeier, Stephen M. Pirris, H. Gordon Deen and Mark A. Pichelmann

Spinal instrumentation has made significant advances in the last two decades, with transpedicular constructs now widely used in spinal fixation. Pedicle screw constructs are routinely used in thoracolumbar-instrumented fusions, and in recent years, the cervical spine as well. Three-column fixations with pedicle screws provide the most rigid form of posterior stabilization. Surgical landmarks and fluoroscopy have been used routinely for pedicle screw insertion, but a number of studies reveal inaccuracies in placement using these conventional techniques (ranging from 10% to 50%). The ability to combine 3D imaging with intraoperative navigation systems has improved the accuracy and safety of pedicle screw placement, especially in more complex spinal deformities. However, in the authors' experience with image guidance in more than 1500 cases, several potential pitfalls have been identified while using intraoperative spinal navigation that could lead to suboptimal results. This article summarizes the authors' experience with these various pitfalls using spinal navigation, and gives practical tips on their avoidance and management.

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Stephen M. Pirris, Eric W. Nottmeier, Sherri Kimes, Michael O'Brien and Gazanfar Rahmathulla

Object

Considerable biological research has been performed to aid bone healing in conjunction with lumbar fusion surgery. Iliac crest autograft is often considered the gold standard because it has the vital properties of being osteoconductive, osteoinductive, and osteogenic. However, graft site pain has been widely reported as the most common donor site morbidity. Autograft site pain has led many companies to develop an abundance of bone graft extenders, which have limited proof of efficacy. During the surgical consent process, many patients ask surgeons to avoid harvesting autograft because of the reported pain complications. The authors sought to study postoperative graft site pain by simply asking patients whether they knew which iliac crest was grafted when a single skin incision was made for the fusion operation.

Methods

Twenty-five patients underwent iliac crest autografting with allograft reconstruction during instrumented lumbar fusion surgery. In all patients the autograft was harvested through the same skin incision but with a separate fascial incision. At various points postoperatively, the patients were asked if they could tell which iliac crest had been harvested, and if so, how much pain did it cause (10-point Numeric Rating Scale).

Results

Most patients (64%) could not correctly determine which iliac crest had been harvested. Of the 9 patients who correctly identified the side of the autograft, 7 were only able to guess. The 2 patients who confidently identified the side of grafting had no pain at rest and mild pain with activity. One patient who incorrectly guessed the side of autografting did have significant sacroiliac joint degenerative pain bilaterally.

Conclusions

Results of this study indicate the inability of patients to clearly define their graft site after iliac crest autograft harvest with allograft reconstruction of the bony defect unless they have a separate skin incision. This simple, easily reproducible pilot study can be expanded into a larger, multiinstitutional investigation to provide more definitive answers regarding the ideal, safe, and cost-effective bone graft material to be used in spinal fusions.

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Mayur Sharma, Elizabeth E. Bennett, Gazanfar Rahmathulla, Samuel T. Chao, Hilary K. Koech, Stephanie N. Gregory, Todd Emch, Anthony Magnelli, Antonio Meola, John H. Suh and Lilyana Angelov

OBJECTIVE

Stereotactic radiosurgery (SRS) of the spine is a conformal method of delivering a high radiation dose to a target in a single or few (usually ≤ 5) fractions with a sharp fall-off outside the target volume. Although efforts have been focused on evaluating spinal cord tolerance when treating spinal column metastases, no study has formally evaluated toxicity to the surrounding organs at risk (OAR), such as the brachial plexus or the oropharynx, when performing SRS in the cervicothoracic region. The aim of this study was to evaluate the radiation dosimetry and the acute and delayed toxicities of SRS on OAR in such patients.

METHODS

Fifty-six consecutive patients (60 procedures) with a cervicothoracic spine tumor involving segments within C5–T1 who were treated using single-fraction SRS between February 2006 and July 2014 were included in the study. Each patient underwent CT simulation and high-definition MRI before treatment. The clinical target volume and OAR were contoured on BrainScan and iPlan software after image fusion. Radiation toxicity was evaluated using the common toxicity criteria for adverse events and correlated to the radiation doses delivered to these regions. The incidence of vertebral body compression fracture (VCF) before and after SRS was evaluated also.

RESULTS

Metastatic lesions constituted the majority (n = 52 [93%]) of tumors treated with SRS. Each patient was treated with a median single prescription dose of 16 Gy to the target. The median percentage of tumor covered by SRS was 93% (maximum target dose 18.21 Gy). The brachial plexus received the highest mean maximum dose of 17 Gy, followed by the esophagus (13.8 Gy) and spinal cord (13 Gy). A total of 14 toxicities were encountered in 56 patients (25%) during the study period. Overall, 14% (n = 8) of the patients had Grade 1 toxicity, 9% (n = 5) had Grade 2 toxicity, 2% (n = 1) had Grade 3 toxicity, and none of the patients had Grade 4 or 5 toxicity. The most common (12%) toxicity was dysphagia/odynophagia, followed by axial spine pain flare or painful radiculopathy (9%). The maximum radiation dose to the brachial plexus showed a trend toward significance (p = 0.066) in patients with worsening post-SRS pain. De novo and progressive VCFs after SRS were noted in 3% (3 of 98) and 4% (4 of 98) of vertebral segments, respectively.

CONCLUSIONS

From the analysis, the current SRS doses used at the Cleveland Clinic seem safe and well tolerated at the cervicothoracic junction. These preliminary data provide tolerance benchmarks for OAR in this region. Because the effect of dose-escalation SRS strategies aimed at improving local tumor control needs to be balanced carefully with associated treatment-related toxicity on adjacent OAR, larger prospective studies using such approaches are needed.

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Gazanfar Rahmathulla, Pablo F. Recinos, David E. Traul, Rafi Avitsian, Marisa Yunak, Nicole T. Harper, Gene H. Barnett and Violette Renard Recinos

Technological advances have made it possible to seamlessly integrate modern neuroimaging into the neurosurgical operative environment. This integration has introduced many new applications improving surgical treatments. One major addition to the neurosurgical armamentarium is intraoperative navigation and MRI, enabling real-time use during surgery. In the 1970s, the American College of Radiology issued safety guidelines for diagnostic MRI facilities. Until now, however, no such guidelines existed for the MRI-integrated operating room, which is a high-risk zone requiring standardized protocols to ensure the safety of both the patient and the operating room staff. The forces associated with the strong 1.5- and 3.0-T magnets used for MRI are potent and hazardous, creating distinct concerns regarding safety, infection control, and image interpretation. Authors of this paper provide an overview of the intraoperative MRI operating room, safety considerations, and a series of checklists and protocols for maintaining safety in this zero tolerance environment.

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Jason P. Sheehan, Robert M. Starke, Hideyuki Kano, Gene H. Barnett, David Mathieu, Veronica Chiang, James B. Yu, Judith Hess, Heyoung L. McBride, Norissa Honea, Peter Nakaji, John Y. K. Lee, Gazanfar Rahmathulla, Wendi A. Evanoff, Michelle Alonso-Basanta and L. Dade Lunsford

OBJECT

Posterior fossa meningiomas represent a common yet challenging clinical entity. They are often associated with neurovascular structures and adjacent to the brainstem. Resection can be undertaken for posterior fossa meningiomas, but residual or recurrent tumor is frequent. Stereotactic radiosurgery (SRS) has been used to treat meningiomas, and this study evaluates the outcome of this approach for those located in the posterior fossa.

METHODS

At 7 medical centers participating in the North American Gamma Knife Consortium, 675 patients undergoing SRS for a posterior fossa meningioma were identified, and clinical and radiological data were obtained for these cases. Females outnumbered males at a ratio of 3.8 to 1, and the median patient age was 57.6 years (range 12–89 years). Prior resection was performed in 43.3% of the patient sample. The mean tumor volume was 6.5 cm3, and a median margin dose of 13.6 Gy (range 8–40 Gy) was delivered to the tumor.

RESULTS

At a mean follow-up of 60.1 months, tumor control was achieved in 91.2% of cases. Actuarial tumor control was 95%, 92%, and 81% at 3, 5, and 10 years after radiosurgery. Factors predictive of tumor progression included age greater than 65 years (hazard ratio [HR] 2.36, 95% CI 1.30–4.29, p = 0.005), prior history of radiotherapy (HR 5.19, 95% CI 1.69–15.94, p = 0.004), and increasing tumor volume (HR 1.05, 95% CI 1.01–1.08, p = 0.005). Clinical stability or improvement was achieved in 92.3% of patients. Increasing tumor volume (odds ratio [OR] 1.06, 95% CI 1.01–1.10, p = 0.009) and clival, petrous, or cerebellopontine angle location as compared with petroclival, tentorial, and foramen magnum location (OR 1.95, 95% CI 1.05–3.65, p = 0.036) were predictive of neurological decline after radiosurgery. After radiosurgery, ventriculoperitoneal shunt placement, resection, and radiation therapy were performed in 1.6%, 3.6%, and 1.5%, respectively.

CONCLUSIONS

Stereotactic radiosurgery affords a high rate of tumor control and neurological preservation for patients with posterior fossa meningiomas. Those with a smaller tumor volume and no prior radiation therapy were more likely to have a favorable response after radiosurgery. Rarely, additional procedures may be required for hydrocephalus or tumor progression.