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Marcus D. Mazur and Andrew T. Dailey

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Thomas J. Buell, Davis G. Taylor, Ching-Jen Chen, Lauren K. Dunn, Jeffrey P. Mullin, Marcus D. Mazur, Chun-Po Yen, Mark E. Shaffrey, Christopher I. Shaffrey, Justin S. Smith and Bhiken I. Naik

OBJECTIVE

Significant blood loss and coagulopathy are often encountered during adult spinal deformity (ASD) surgery, and the optimal intraoperative transfusion algorithm is debatable. Rotational thromboelastometry (ROTEM), a functional viscoelastometric method for real-time hemostasis testing, may allow early identification of coagulopathy and improve transfusion practices. The objective of this study was to investigate the effect of ROTEM-guided blood product management on perioperative blood loss and transfusion requirements in ASD patients undergoing correction with pedicle subtraction osteotomy (PSO).

METHODS

The authors retrospectively reviewed patients with ASD who underwent single-level lumbar PSO at the University of Virginia Health System. All patients who received ROTEM-guided blood product transfusion between 2015 and 2017 were matched in a 1:1 ratio to a historical cohort treated using conventional laboratory testing (control group). Co-primary outcomes were intraoperative estimated blood loss (EBL) and total blood product transfusion volume. Secondary outcomes were perioperative transfusion requirements and postoperative subfascial drain output.

RESULTS

The matched groups (ROTEM and control) comprised 17 patients each. Comparison of matched group baseline characteristics demonstrated differences in female sex and total intraoperative dose of intravenous tranexamic acid (TXA). Although EBL was comparable between ROTEM versus control (3200.00 ± 2106.24 ml vs 3874.12 ± 2224.22 ml, p = 0.36), there was a small to medium effect size (Cohen’s d = 0.31) on EBL reduction with ROTEM. The ROTEM group had less total blood product transfusion volume (1624.18 ± 1774.79 ml vs 2810.88 ± 1847.46 ml, p = 0.02), and the effect size was medium to large (Cohen’s d = 0.66). This difference was no longer significant after adjusting for TXA (β = −0.18, 95% confidence interval [CI] −1995.78 to 671.64, p = 0.32). More cryoprecipitate and less fresh frozen plasma (FFP) were transfused in the ROTEM group patients (cryoprecipitate units: 1.24 ± 1.20 vs 0.53 ± 1.01, p = 0.03; FFP volume: 119.76 ± 230.82 ml vs 673.06 ± 627.08 ml, p < 0.01), and this remained significant after adjusting for TXA (cryoprecipitate units: β = 0.39, 95% CI 0.05 to 1.73, p = 0.04; FFP volume: β = −0.41, 95% CI −772.55 to −76.30, p = 0.02). Drain output was lower in the ROTEM group and remained significant after adjusting for TXA.

CONCLUSIONS

For ASD patients treated using lumbar PSO, more cryoprecipitate and less FFP were transfused in the ROTEM group compared to the control group. These preliminary findings suggest ROTEM-guided therapy may allow early identification of hypofibrinogenemia, and aggressive management of this may reduce blood loss and total blood product transfusion volume. Additional prospective studies of larger cohorts are warranted to identify the appropriate subset of ASD patients who may benefit from intraoperative ROTEM analysis.

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James H. Nguyen, Thomas J. Buell, Tony R. Wang, Jeffrey P. Mullin, Marcus D. Mazur, Juanita Garces, Davis G. Taylor, Chun-Po Yen, Christopher I. Shaffrey and Justin S. Smith

OBJECTIVE

Recent literature describing complications associated with spinopelvic fixation with iliac screws in adult patients has been limited but has suggested high complication rates. The authors’ objective was to report their experience with iliac screw fixation in a large series of patients with a 2-year minimum follow-up.

METHODS

Of 327 adult patients undergoing spinopelvic fixation with iliac screws at the authors’ institution between 2010 and 2015, 260 met the study inclusion criteria (age ≥ 18 years, first-time iliac screw placement, and 2-year minimum follow-up). Patients with active spinal infection were excluded. All iliac screws were placed via a posterior midline approach using fluoroscopic guidance. Iliac screw heads were deeply recessed into the posterior superior iliac spine. Clinical and radiographic data were obtained and analyzed.

RESULTS

Twenty patients (7.7%) had iliac screw–related complication, which included fracture (12, 4.6%) and/or screw loosening (9, 3.5%). No patients had iliac screw head prominence that required revision surgery or resulted in pain, wound dehiscence, or poor cosmesis. Eleven patients (4.2%) had rod or connector fracture below S1. Overall, 23 patients (8.8%) had L5–S1 pseudarthrosis. Four patients (1.5%) had fracture of the S1 screw. Seven patients (2.7%) had wound dehiscence (unrelated to the iliac screw head) or infection. The rate of reoperation (excluding proximal junctional kyphosis) was 17.7%. On univariate analysis, an iliac screw–related complication rate was significantly associated with revision fusion (70.0% vs 41.2%, p = 0.013), a greater number of instrumented vertebrae (mean 12.6 vs 10.3, p = 0.014), and greater postoperative pelvic tilt (mean 27.7° vs 23.2°, p = 0.04). Lumbosacral junction–related complications were associated with a greater mean number of instrumented vertebrae (12.6 vs 10.3, p = 0.014). Reoperation was associated with a younger mean age at surgery (61.8 vs 65.8 years, p = 0.014), a greater mean number of instrumented vertebrae (12.2 vs 10.2, p = 0.001), and longer clinical and radiological mean follow-up duration (55.8 vs 44.5 months, p < 0.001; 55.8 vs 44.6 months, p < 0.001, respectively). On multivariate analysis, reoperation was associated with longer clinical follow-up (p < 0.001).

CONCLUSIONS

Previous studies on iliac screw fixation have reported very high rates of complications and reoperation (as high as 53.6%). In this large, single-center series of adult patients, iliac screws were an effective method of spinopelvic fixation that had high rates of lumbosacral fusion and far lower complication rates than previously reported. Collectively, these findings argue that iliac screw fixation should remain a favored technique for spinopelvic fixation.

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Thomas J. Buell, James H. Nguyen, Marcus D. Mazur, Jeffrey P. Mullin, Juanita Garces, Davis G. Taylor, Chun-Po Yen, Mark E. Shaffrey, Christopher I. Shaffrey and Justin S. Smith

OBJECTIVE

Fixed sagittal spinal malalignment is a common problem in adult spinal deformity (ASD). Various three-column osteotomy techniques, including the extended pedicle subtraction osteotomy (ePSO), may correct global and regional malalignment in this patient population. In contrast to the number of reports on traditional PSO (Schwab grade 3 osteotomy), there is limited literature on the outcomes of ePSO (Schwab grade 4 osteotomy) in ASD surgery. The objective of this retrospective study was to provide focused investigation of radiographic outcomes and complications of single-level lumbar ePSO for ASD patients with fixed sagittal malalignment.

METHODS

Consecutive ASD patients in whom sagittal malalignment had been treated with single-level lumbar ePSO at the authors’ institution between 2010 and 2015 were analyzed, and those with a minimum 2-year follow-up were included in the study. Radiographic analyses included assessments of segmental lordosis through the ePSO site (sagittal Cobb angle measured from the superior endplate of the vertebra above and inferior endplate of the vertebra below the ePSO), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence and LL mismatch, thoracic kyphosis (TK), and sagittal vertical axis (SVA) on standing long-cassette radiographs. Complications were analyzed for the entire group.

RESULTS

Among 71 potentially eligible patients, 55 (77%) had a minimum 2-year follow-up and were included in the study. Overall, the average postoperative increases in ePSO segmental lordosis and overall LL were 41° ± 14° (range 7°–69°, p < 0.001) and 38° ± 11° (range 9°–58°, p < 0.001), respectively. The average SVA improvement was 13 ± 7 cm (range of correction: −33.6 to 3.4 cm, p < 0.001). These measurements were maintained when comparing early postoperative to last follow-up values, respectively (mean follow-up 52 months, range 26–97 months): ePSO segmental lordosis, 34° vs 33°, p = 0.270; LL, 47.3° vs 46.7°, p = 0.339; and SVA, 4 vs 5 cm, p = 0.330. Rod fracture (RF) at the ePSO site occurred in 18.2% (10/55) of patients, and pseudarthrosis (PA) at the ePSO site was confirmed by CT imaging or during rod revision surgery in 14.5% (8/55) of patients. Accessory supplemental rods across the ePSO site, a more recently employed technique, significantly reduced the occurrence of RF or PA on univariate (p = 0.004) and multivariable (OR 0.062, 95% CI 0.007–0.553, p = 0.013) analyses; this effect approached statistical significance on Kaplan-Meier analysis (p = 0.053, log-rank test). Interbody cage placement at the ePSO site resulted in greater ePSO segmental lordosis correction (45° vs 35°, p = 0.007) without significant change in RF or PA (p = 0.304). Transient and persistent motor deficits occurred in 14.5% (8/55) and 1.8% (1/55) of patients, respectively.

CONCLUSIONS

Extended PSO is an effective technique to correct fixed sagittal malalignment for ASD. In comparison to traditional PSO techniques, ePSO may allow greater focal correction with comparable complication rates, especially with interbody cage placement at the ePSO site and the use of accessory supplemental rods.

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Al-Wala Awad, Karam Moon, Nam Yoon, Marcus D. Mazur, M. Yashar S. Kalani, Philipp Taussky, Cameron G. McDougall, Felipe C. Albuquerque and Min S. Park

OBJECTIVE

Flow diversion has proven to be an efficacious means of treating cerebral aneurysms that are refractory to other therapeutic means. Patients with tandem aneurysms treated with flow diversion have been included in larger, previously reported series; however, there are no dedicated reports on using this technique during a single session to treat this unique subset of patients. Therefore, the authors analyzed the outcomes of patients who had undergone single-session flow diversion for the treatment of tandem aneurysms.

METHODS

The authors conducted a retrospective review of flow diversion with the Pipeline embolization device (PED) for the treatment of tandem aneurysms in a single session at 2 participating medical centers: University of Utah, Salt Lake City, Utah, and Barrow Neurological Institute, Phoenix, Arizona. Patient demographic data, aneurysm characteristics, treatment strategy and results, complications, and follow-up data were collected from the medical record and analyzed.

RESULTS

Between January 2011 and December 2015, 17 patients (12 female, 5 male) with a total of 38 aneurysms (mean size 4.7 ± 2.7 mm, mean ± SD) were treated. Sixteen patients had aneurysms in the anterior circulation, and 1 patient had tandem aneurysms in the posterior circulation. Twelve patients underwent only placement of a PED, whereas 5 underwent adjunctive coil embolization of at least 1 aneurysm. One PED was used in each of 9 patients, and 2 PEDs were required in each of 8 patients. There were 2 intraprocedural complications; however, in both instances, the patients were asymptomatic at the last follow-up. The follow-up imaging studies were available for 15 patients at a mean of 7 months after treatment (216 days, range 0–540 days). The mean initial Raymond score after treatment was 2.7 ± 0.7, and the mean final score was 1.3 ± 0.7.

CONCLUSIONS

In this series, the use of flow diversion for the treatment of tandem cerebral aneurysms had an acceptable safety profile, indicating that it should be considered as an effective therapy for this complicated subset of patients. Further prospective studies must be performed before more definitive conclusions can be made.

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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.

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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, 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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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.