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Ian G. Dorward and Lawrence G. Lenke

In addressing adult spinal deformities through a posterior approach, the surgeon now may choose from among a variety of osteotomy techniques. The Ponte or Smith-Petersen osteotomy provides the least correction, but it can be used at multiple levels with minimal blood loss and a lower operative risk. Pedicle subtraction osteotomies provide nearly 3 times the per-level correction of Ponte/Smith-Petersen osteotomies but carry increased technical demands, longer operative time, and greater blood loss and associated morbidity. Vertebral column resections serve as the most powerful method, providing the most correction in the coronal and sagittal planes, but posing both the greatest technical challenge and the greatest risk to the patient in terms of possible neurological injury, operative time, and potential morbidity. The authors reviewed the literature relating to these osteotomy methods. They also provided case illustrations and suggestions for their proper application.

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Kavelin Rumalla, Chester K. Yarbrough, Andrew J. Pugely, Linda Koester, and Ian G. Dorward

OBJECTIVE

The objective of this study was to determine if the recent changes in technology, surgical techniques, and surgical literature have influenced practice trends in spinal fusion surgery for pediatric neuromuscular scoliosis (NMS). In this study the authors analyzed recent trends in the surgical management of NMS and investigated the effect of various patient and surgical factors on in-hospital complications, outcomes, and costs, using the Nationwide Inpatient Sample (NIS) database.

METHODS

The NIS was queried from 2002 to 2011 using International Classification of Diseases, Ninth Edition, Clinical Modification codes to identify pediatric cases (age < 18 years) of spinal fusion for NMS. Several patient, surgical, and short-term outcome factors were included in the analyses. Trend analyses of these factors were conducted. Both univariate and multivariable analyses were used to determine the effect of the various patient and surgical factors on short-term outcomes.

RESULTS

Between 2002 and 2011, a total of 2154 NMS fusion cases were identified, and the volume of spinal fusion procedures increased 93% from 148 in 2002 to 286 in 2011 (p < 0.0001). The mean patient age was 12.8 ± 3.10 years, and 45.6% of the study population was female. The overall complication rate was 40.1% and the respiratory complication rate was 28.2%. From 2002 to 2011, upward trends (p < 0.0001) were demonstrated in Medicaid insurance status (36.5% to 52.8%), presence of ≥ 1 comorbidity (40.2% to 52.1%), and blood transfusions (25.2% to 57.3%). Utilization of posterior-only fusions (PSFs) increased from 66.2% to 90.2% (p < 0.0001) while combined anterior release/fusions and PSF (AR/PSF) decreased from 33.8% to 9.8% (< 0.0001). Intraoperative neurophysiological monitoring (IONM) underwent increasing utilization from 2009 to 2011 (15.5% to 20.3%, p < 0.0001). The use/harvest of autograft underwent a significant upward trend between 2002 and 2011 (31.3% to 59.8%, p < 0.0001). In univariate analysis, IONM use was associated with decreased complications (40.7% to 33.1%, p = 0.049) and length of stay (LOS; 9.21 to 6.70 days, p <0.0001). Inflation-adjusted mean hospital costs increased nearly 75% from 2002 to 2011 ($36,805 to $65,244, p < 0.0001). In the multivariable analysis, nonwhite race, highest quartile of median household income, greater preexisting comorbidity, long-segment fusions, and use of blood transfusions were found to increase the likelihood of complication occurrence (all p < 0.05). In further multivariable analysis, independent predictors of prolonged LOS included older age, increased preexisting comorbidity, the AR/PSF approach, and long-segment fusions (all p < 0.05). Lastly, the likelihood of increased hospital costs (at or above the 90th percentile for LOS, 14 days) was increased by older age, female sex, Medicaid insurance status, highest quartile of median household income, AR/PSF approach, long-segment fusion, and blood transfusion (all p < 0.05). In multivariable analysis, the use of autograft was associated with a lower likelihood of complication occurrence and prolonged LOS (both p < 0.05).

CONCLUSIONS

Increasing use of IONM and posterior-only approaches may combat the high complication rates in NMS. The trends of increasing comorbidities, blood transfusions, and total costs in spinal fusion surgery for pediatric NMS may indicate an increasingly aggressive approach to these cases.

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David N. Loy, Keith M. Rich, Joseph Simpson, Ian Dorward, Lakshmi Santanam, and Colin P. Derdeyn

This report demonstrates that time-of-flight (TOF) MR angiography is a useful adjunct for planning stereotactic radiosurgery (SRS) of large arteriovenous malformations (AVMs) after staged embolization with Onyx.

Onyx (ethylene vinyl copolymer), a recently approved liquid embolic agent, has been increasingly used to exclude portions of large AVMs from the parent circulation prior to SRS. Limiting SRS to regions of persistent arteriovenous shunting and excluding regions eliminated by embolization may reduce unnecessary radiation doses to eloquent brain structures. However, SRS dosimetry planning presents unique challenges after Onyx embolization because it creates extensive artifacts on CT scans, and it cannot be delineated from untreated nidus on standard MR sequences.

During the radiosurgery procedure, MR images were obtained using a GE Signa 1.5-T unit. Standard axial T2 fast spin echo high-resolution images (TR 3000 msec, TE 108 msec, slice thickness 2.5 mm) were generated for optimal visualization of brain tissue and AVM flow voids. The 3D TOF MR angiography images of the circle of Willis and vertebral arteries were subsequently obtained to visualize AVM regions embolized with Onyx (TR 37 msec, TE 6.9 msec, flip angle 20°).

Adjunct TOF MR angiography images demonstrated excellent contrast between nidus embolized with Onyx and regions of persistent arteriovenous shunting within a large AVM prior to SRS. Additional information derived from these sequences resulted in substantial adjustments to the treatment plan and an overall reduction in the treated tissue volume.

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Christopher F. Dibble, Justin K. Zhang, Jacob K. Greenberg, Saad Javeed, Jawad M. Khalifeh, Deeptee Jain, Ian Dorward, Paul Santiago, Camilo Molina, Brenton Pennicooke, and Wilson Z. Ray

OBJECTIVE

Local and regional radiographic outcomes following minimally invasive (MI) transforaminal lumbar interbody fusion (TLIF) versus open TLIF remain unclear. The purpose of this study was to provide a comprehensive assessment of local and regional radiographic parameters following MI-TLIF and open TLIF. The authors hypothesized that open TLIF provides greater segmental and global lordosis correction than MI-TLIF.

METHODS

A single-center retrospective cohort study of consecutive patients undergoing MI- or open TLIF for grade I degenerative spondylolisthesis was performed. One-to-one nearest-neighbor propensity score matching (PSM) was used to match patients who underwent open TLIF to those who underwent MI-TLIF. Sagittal segmental radiographic measures included segmental lordosis (SL), anterior disc height (ADH), posterior disc height (PDH), foraminal height (FH), percent spondylolisthesis, and cage position. Lumbopelvic radiographic parameters included overall lumbar lordosis (LL), pelvic incidence (PI)–lumbar lordosis (PI-LL) mismatch, sacral slope (SS), and pelvic tilt (PT). Change in segmental or overall lordosis after surgery was considered "lordosing" if the change was > 0° and "kyphosing" if it was ≤ 0°. Student t-tests or Wilcoxon rank-sum tests were used to compare outcomes between MI-TLIF and open-TLIF groups.

RESULTS

A total of 267 patients were included in the study, 114 (43%) who underwent MI-TLIF and 153 (57%) who underwent open TLIF, with an average follow-up of 56.6 weeks (SD 23.5 weeks). After PSM, there were 75 patients in each group. At the latest follow-up both MI- and open-TLIF patients experienced significant improvements in assessment scores obtained with the Oswestry Disability Index (ODI) and the numeric rating scale for low-back pain (NRS-BP), without significant differences between groups (p > 0.05). Both MI- and open-TLIF patients experienced significant improvements in SL, ADH, and percent corrected spondylolisthesis compared to baseline (p < 0.001). However, the MI-TLIF group experienced significantly larger magnitudes of correction with respect to these metrics (ΔSL 4.14° ± 4.35° vs 1.15° ± 3.88°, p < 0.001; ΔADH 4.25 ± 3.68 vs 1.41 ± 3.77 mm, p < 0.001; percent corrected spondylolisthesis: −10.82% ± 6.47% vs −5.87% ± 8.32%, p < 0.001). In the MI-TLIF group, LL improved in 44% (0.3° ± 8.5°) of the cases, compared to 48% (0.9° ± 6.4°) of the cases in the open-TLIF group (p > 0.05). Stratification by operative technique (unilateral vs bilateral facetectomy) and by interbody device (static vs expandable) did not yield statistically significant differences (p > 0.05).

CONCLUSIONS

Both MI- and open-TLIF patients experienced significant improvements in patient-reported outcome (PRO) measures and local radiographic parameters, with neutral effects on regional alignment. Surprisingly, in our cohort, change in SL was significantly greater in MI-TLIF patients, perhaps reflecting the effect of operative techniques, technological innovations, and the preservation of the posterior tension band. Taking these results together, no significant overall differences in LL between groups were demonstrated, which suggests that MI-TLIF is comparable to open approaches in providing radiographic correction after surgery. These findings suggest that alignment targets can be achieved by either MI- or open-TLIF approaches, highlighting the importance of surgeon attention to these variables.

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Ian G. Dorward, Jeffrey B. Titus, David D. Limbrick, James M. Johnston, Mary E. Bertrand, and Matthew D. Smyth

Object

Patients undergoing epilepsy surgery without evidence of a lesion on MR imaging and without a temporal source for seizure onset generally have less favorable outcomes than patients with structural lesions or temporal onset. However, many of these patients are viable candidates for invasive monitoring and subsequent resection or multiple subpial transections (MSTs). The purpose of this study was to evaluate the surgical treatment of pediatric patients with extratemporal, nonlesional epilepsy in order to better understand the clinical and neuropsychological outcomes expected in this patient group.

Methods

Forty-three pediatric patients with negative results on MR imaging and lateralized, extratemporal findings on electroencephalography underwent invasive monitoring with grid and/or strip electrodes. Thirty-three subsequently had resection of an epileptogenic focus and/or MSTs.

Results

Outcome was classified as Engel class I or II in 54.5% of the patients who underwent resection/MSTs and Engel class III or IV in 45.5%. Use of MSTs was associated with poor outcome. Neuropsychological evaluation showed significant improvement in immediate auditory attention following surgery and revealed several significant results on subgroup analysis. Complications occurred in 14% of patients (a 7% rate per procedure). Ten patients (23%) underwent invasive monitoring without proceeding to therapeutic surgery because no epileptogenic region was amenable to resection. Neuropsychological outcomes were generally stable.

Conclusions

Patients with extratemporal, nonlesional seizures are viable candidates for invasive monitoring with grid/strip electrodes, and good outcomes can be obtained with resective surgery. The use of MSTs may correlate with worse outcome. This study also provides additional data to assist in counseling patients on the risks of negative invasive monitoring, deficits resulting from resection/MSTs, and possible operative complications.

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Ian G. Dorward, Jingqin Luo, Arie Perry, David H. Gutmann, David B. Mansur, Joshua B. Rubin, and Jeffrey R. Leonard

Object

Currently there is no consensus regarding the frequency of neuroimaging following gross-total resection (GTR) of pilocytic astrocytoma (PA) in children. Whereas several reports recommend no postoperative imaging, one study proposed surveillance MR imaging studies to detect delayed recurrences.

Methods

The records of 40 consecutive pediatric patients who underwent GTR of infratentorial PAs were examined. All had follow-up duration of ≥ 2 years. Patients underwent early (< 48 hours) postoperative MR imaging, followed by surveillance imaging at 3–6 months, 1 year, and variably thereafter. The classification of GTR was based on a lack of nodular enhancement on early postoperative MR imaging. Demographic, clinical, and pathological variables were analyzed with respect to recurrence status. Univariate and multivariate analyses were performed to evaluate the association between pathological variables and recurrence-free survival (RFS).

Results

Of 13 patients demonstrating new nodular enhancement on MR imaging at 3–6 months, the disease progressed in 10, with a median time to recurrence of 6.4 months (range 2–48.2 months). At last follow-up, 29 patients had no recurrence, whereas in 1 additional patient the tumor recurred at 48 months, despite the absence of a new contrast-enhancing nodule at 3–6 months (for a total of 11 patients with recurrence). No demographic variable was associated with recurrence. Nodular enhancement on MR imaging at 3–6 months was significantly associated with recurrence in both univariate (p < 0.0001) and multivariate (p = 0.0015) analyses. Among the pathological variables, a high Ki 67 labeling index (LI) was similarly significantly associated with RFS in both univariate (p = 0.0016) and multivariate (p = 0.034) analyses. Multivariate models that significantly predicted RFS included a risk score incorporating Ki 67 LI and CD68 positivity (p = 0.0022), and a similar risk score combining high Ki 67 LI with the presence of nodular enhancement on initial surveillance MR imaging (p < 0.0001).

Conclusions

Surveillance MR imaging at 3–6 months after resection predicts tumor recurrence following GTR. One patient suffered delayed recurrence, arguing against a “no imaging” philosophy. The data also highlight the pathological variables that can help categorize patients into groups with high or low risk for recurrence. Larger series are needed to confirm these associations.