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Alex S. Ha, Meghan Cerpa, Justin Mathew, Paul Park, Joseph M. Lombardi, Andrew J. Luzzi, Nathan J. Lee, Marc D. Dyrszka, Zeeshan M. Sardar, Ronald A. Lehman Jr., and Lawrence G. Lenke

OBJECTIVE

Lumbosacral fractional curves in adult spinal deformity (ASD) patients often have sharp coronal curves resulting in significant pain and imbalance. Postoperative stretch neuropraxia after fractional curve correction can lead to discomfort and unsatisfactory outcomes. The goal of this study was to use radiographic measures to increase understanding of the relationship between postoperative stretch neuropraxia and fractional curve correction.

METHODS

In 62 ASD patients treated from 2015 to 2018, radiographic review was performed, including measurement of the distance between the lower lumbar neural foramen (L4 and L5) in the concavity and convexity of the lumbosacral fractional curve and the ipsilateral femoral heads (FHs; L4–FH and L5–FH) in pre- and postoperative anteroposterior spine radiographs. The largest absolute preoperative to postoperative change in distance between the lower lumbar neural foramen and the ipsilateral FH (ΔL4/L5–FH) was used for analysis. Chi-square analyses, independent and paired t-tests, and logistic regression were performed to study the relationship between L4/L5–FH and stretch neuropraxia for categorical and continuous variables, respectively.

RESULTS

Of the 62 patients, 13 (21.0%) had postoperative stretch neuropraxia. Patients without postoperative stretch neuropraxia had an average ΔL4–FH distance of 16.2 mm compared to patients with stretch neuropraxia, who had an average ΔL4–FH distance of 31.5 mm (p < 0.01). Patients without postoperative neuropraxia had an average ΔL5–FH distance of 11.1 mm compared to those with stretch neuropraxia, who had an average ΔL5–FH distance of 23.0 mm (p < 0.01). Chi-square analysis showed that patients had a 4.78-fold risk of developing stretch neuropraxia with ΔL4–FH > 20 mm (95% CI 1.3–17.3) and a 5.17-fold risk of developing stretch neuropraxia with ΔL5–FH > 15 mm (95% CI 1.4–18.7). Logistic regression analysis indicated that the odds of developing stretch neuropraxia were 15:1 with a ΔL4–FH > 20 mm (95% CI 3–78) and 21:1 with a ΔL5–FH > 15 mm (95% CI 4–113).

CONCLUSIONS

The novel ΔL4/L5–FH distances are strongly associated with postoperative stretch neuropraxia in ASD patients. A ΔL4–FH > 20 mm and ΔL5–FH > 15 mm significantly increase the odds for patients to develop postoperative stretch neuropraxia.

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Masayoshi Ishii, Atsunori Ohnishi, Akira Yamagishi, and Tetsuo Ohwada

OBJECTIVE

Cortical bone trajectory (CBT) screw insertion using a freehand technique is considered less feasible than guided techniques, due to the lack of readily identifiable visual landmarks. However, in posterior lumbar interbody fusion (PLIF), after resection of the posterior anatomy, the pedicles themselves, into which implantation is performed, are palpable from the spinal canal and neural foramen. With the help of pedicle wall probing, the authors have placed CBT screws using a freehand technique without image guidance in PLIF. This technique has advantages of no radiation exposure and no requirement for expensive devices, but the disadvantage of reduced accuracy in screw placement. To address the problem of symptomatic breaches with this freehand technique, variables related to unacceptable screw positioning and need for revisions were investigated.

METHODS

From 2014 to 2020, 182 of 426 patients with single-level PLIF were enrolled according to the combined criteria of L4–5 level, excluding cases of revision and isthmic spondylolisthesis; using screws 5.5 mm in diameter; and operated by right-handed surgeons. We studied the number of misplaced screws found and replaced during initial surgeries. Using multiplanar reconstruction CT postoperatively, 692 screw positions on images were classified using previously reported grading criteria. Details of pedicle breaches requiring revisions were studied. We conducted a statistical analysis of the relationship between unacceptable (perforations > 2 mm) misplacements and four variables: level, laterality, spinal deformity, and experiences of surgeons.

RESULTS

Three screws in L4 and another in L5 were revised during initial surgeries. The total rate of unacceptable screws on CT examinations was 3.3%. Three screws in L4 and another in L5 breached inferomedial pedicle walls in grade 3 and required revisions. The revision rate was 2.2%. The percentage of unacceptable screws was 5.2% in L4 and 1.7% in L5 (p < 0.05), whereas other variables showed no significant differences.

CONCLUSIONS

A freehand technique can be feasible for CBT screw insertion in PLIF, balancing the risks of 3.3% unacceptable misplacements and 2.2% revisions with the benefits of no radiation exposure and no need for expensive devices. Pedicle palpation in L4 is the key to safety, even though it requires deeper and more difficult probing. In the initial surgeries and revisions, 75% of revised screws were observed in L4, and unacceptable screw positions were more likely to be found in L4 than in L5.

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Yifan Zhang, Xiongfei Wang, Chongyang Tang, Yuguang Guan, Fan Chen, Qing Gao, Jing Wang, Jian Zhou, Feng Zhai, Detlev Boison, Guoming Luan, and Tianfu Li

OBJECTIVE

Vagus nerve stimulation (VNS) is an alternative treatment option for individuals with refractory epilepsy, with nearly 40% of patients showing no benefit after VNS and only 6%–8% achieving seizure freedom. It is presently unclear why some patients respond to treatment and others do not. Therefore, identification of biomarkers to predict efficacy of VNS is of utmost importance. The objective of this study was to explore whether genetic variations in genes involved in adenosine kinase (ADK), ecto-5′-nucleotidase (NT5E), and adenosine A1 receptor (A1R) are linked to outcome of VNS in patients with refractory epilepsy.

METHODS

Thirty single-nucleotide polymorphisms (SNPs), including 9 in genes encoding ADK, 3 in genes encoding NT5E, and 18 in genes encoding A1R, were genotyped in 194 refractory epilepsy patients who underwent VNS. The chi-square test and binary logistic regression were used to determine associations between genetic differences and VNS efficacy.

RESULTS

A significant association between ADK SNPs rs11001109, rs7899674, and rs946185 and seizure reduction with VNS was found. Regardless of sex, age, seizure frequency and type, antiseizure drug use, etiology, and prior surgical history, all patients (10/10 patients [100%]) with minor allele homozygosity at rs11001109 (genotype AA) or rs946185 (AA) achieved > 50% seizure reduction and 4 patients (4/10 [40%]) achieved seizure freedom. VNS therapy demonstrated higher efficacy among carriers of minor allele rs7899674 (CG + GG) (68.3% vs 48.8% for patients with major allele homozygosity).

CONCLUSIONS

Homozygous ADK SNPs rs11001109 (AA) and rs946185 (AA), as well as minor allele rs7899674 (CG + GG), may serve as useful biomarkers for prediction of VNS therapy outcome.

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Masanari Takami, Ryo Taiji, Shunji Tsutsui, Hiroshi Iwasaki, Motohiro Okada, Akihito Minamide, Yasutsugu Yukawa, Hiroshi Hashizume, and Hiroshi Yamada

OBJECTIVE

In corrective spinal surgery for adult spinal deformity (ASD), the focus has been on achieving optimal spinopelvic alignment. However, the correction of coronal spinal alignment is equally important. The conventional intraoperative measurement methods currently used for coronal alignment are not ideal. Here, the authors have developed a new intraoperative coronal alignment measurement technique using a navigational tool for a 3D spinal rod bending system (CAMNBS). The purpose of this study was to test the feasibility of using the CAMNBS for coronal spinal alignment and to evaluate its usefulness in corrective spinal surgery for ASD.

METHODS

In this retrospective cohort study, patients with degenerative lumbar kyphoscoliosis, a Cobb angle ≥ 20°, and lumbar lordosis ≤ 20° who had undergone corrective surgery (n = 67) were included. The pelvic teardrops on both sides, the S1 spinous process, the central point of the apex, a point on the 30-mm cranial (or caudal) side of the apex, and the central point of the upper instrumented vertebra (UIV) and C7 vertebra were registered using the CAMNBS. The positional information of all registered points was displayed as 2D figures on a monitor. Deviation of the UIV plumb line from the central sacral vertical line (UIV-CSVL) and deviation of the C7 plumb line from the CSVL (C7-CSVL) were measured using the 2D figures. Nineteen patients evaluated using the CAMNBS (BS group) were compared with 48 patients evaluated using conventional intraoperative radiography (XR group). The UIV-CSVL measured intraoperatively using the CAMNBS was compared with that measured using postoperative radiography. The prevalence of postoperative coronal malalignment (CM) and the absolute value of postoperative C7-CSVL were compared between the groups on radiographs obtained in the standing position within 4 weeks after surgery. Postoperative CM was defined as the absolute value of C7-CSVL ≥ 30 mm. Further, the measurement time and amount of radiation exposure were measured.

RESULTS

No significant differences in demographic, sagittal, and coronal parameters were observed between the two groups. UIV-CSVL was 2.3 ± 9.5 mm with the CAMNBS and 1.8 ± 16.6 mm with the radiographs, showing no significant difference between the two methods (p = 0.92). The prevalence of CM was 2/19 (10.5%) in the BS group and 18/48 (37.5%) in the XR group, and absolute values of C7-CSVL were 15.2 ± 13.1 mm in the BS group and 25.0 ± 18.0 mm in the XR group, showing statistically significant differences in both comparisons (p = 0.04 and 0.03, respectively). The CAMNBS method required 3.5 ± 0.9 minutes, while the conventional radiograph method required 13.3 ± 1.5 minutes; radiation exposure was 2.1 ± 1.1 mGy in the BS group and 2.9 ± 0.6 mGy in the XR group. Statistically significant differences were demonstrated in both comparisons (p = 0.0002 and 0.03, respectively).

CONCLUSIONS

From this study, it was evident that the CAMNBS did not increase postoperative CM compared with that seen using the conventional radiographic method, and hence can be used in clinical practice.

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Ron N. Alkalay, Michael W. Groff, Marc A. Stadelmann, Florian M. Buck, Sven Hoppe, Nicolas Theumann, Umesh Mektar, Roger B. Davis, and David B. Hackney

OBJECTIVE

The aim of this study was to compare the ability of 1) CT-derived bone lesion quality (classification of vertebral bone metastases [BM]) and 2) computed CT-measured volumetric bone mineral density (vBMD) for evaluating the strength and stiffness of cadaver vertebrae from donors with metastatic spinal disease.

METHODS

Forty-five thoracic and lumbar vertebrae were obtained from cadaver spines of 11 donors with breast, esophageal, kidney, lung, or prostate cancer. Each vertebra was imaged using microCT (21.4 μm), vBMD, and bone volume to total volume were computed, and compressive strength and stiffness experimentally measured. The microCT images were reconstructed at 1-mm voxel size to simulate axial and sagittal clinical CT images. Five expert clinicians blindly classified the images according to bone lesion quality (osteolytic, osteoblastic, mixed, or healthy). Fleiss’ kappa test was used to test agreement among 5 clinical raters for classifying bone lesion quality. Kruskal-Wallis ANOVA was used to test the difference in vertebral strength and stiffness based on bone lesion quality. Multivariable regression analysis was used to test the independent contribution of bone lesion quality, computed vBMD, age, gender, and race for predicting vertebral strength and stiffness.

RESULTS

A low interrater agreement was found for bone lesion quality (κ = 0.19). Although the osteoblastic vertebrae showed significantly higher strength than osteolytic vertebrae (p = 0.0148), the multivariable analysis showed that bone lesion quality explained 19% of the variability in vertebral strength and 13% in vertebral stiffness. The computed vBMD explained 75% of vertebral strength (p < 0.0001) and 48% of stiffness (p < 0.0001) variability. The type of BM affected vBMD-based estimates of vertebral strength, explaining 75% of strength variability in osteoblastic vertebrae (R2 = 0.75, p < 0.0001) but only 41% in vertebrae with mixed bone metastasis (R2 = 0.41, p = 0.0168), and 39% in osteolytic vertebrae (R2 = 0.39, p = 0.0381). For vertebral stiffness, vBMD was only associated with that of osteoblastic vertebrae (R2 = 0.44, p = 0.0024). Age and race inconsistently affected the model’s strength and stiffness predictions.

CONCLUSIONS

Pathologic vertebral fracture occurs when the metastatic lesion degrades vertebral strength, rendering it unable to carry daily loads. This study demonstrated the limitation of qualitative clinical classification of bone lesion quality for predicting pathologic vertebral strength and stiffness. Computed CT-derived vBMD more reliably estimated vertebral strength and stiffness. Replacing the qualitative clinical classification with computed vBMD estimates may improve the prediction of vertebral fracture risk.

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Yong-Chan Kim, Keun-Ho Lee, Gab-Lae Kim, Ki-Tack Kim, Kee-Yong Ha, Seung Nam Ko, Qiang Luo, Tae Won Eom, and Hyun Gon Gwak

OBJECTIVE

Recently, new patient-reported outcome measures (PROMs) of the spine were designed to overcome the limitations of previous spinal PROMs and to consider the whole spine as a single kinetic functional unit. Owing to the significance of spine-hip-knee and global body balance, the spine and lower extremities cannot be considered separately. However, no reports have evaluated lower-extremity functional outcome using PROMs after lumbar spine surgery. The authors aimed to elucidate changes in hip and knee PROMs after lumbar interbody fusion and to evaluate the sagittal spinopelvic radiographic parameters that were most strongly correlated with lower-extremity PROMs.

METHODS

In 2018, the authors consecutively evaluated patients who underwent lumbar interbody fusion surgery with at most three levels. Preoperative and 1-year postoperative clinical and radiographic data were assessed. Spinal functional outcomes were measured with the Oswestry Disability Index (ODI), visual analog scale (VAS) for pain, and Scoliosis Research Society–22r (SRS-22r) questionnaire. Lower-extremity functional outcomes were evaluated with the Harris Hip Score (HHS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Linear regression was used to evaluate the relationship between spinal and lower-extremity PROMs and spinopelvic radiographic parameters.

RESULTS

The authors enrolled 67 patients, with a mean age of 66.4 years. The average number of surgical levels was 1.7. All assessed PROMs improved significantly after surgery (p < 0.001 for ODI, p < 0.001 for VAS, p = 0.017 for SRS-22r, p = 0.042 for HHS, and p = 0.033 for WOMAC). Spinopelvic parameters, including lumbar lordosis (LL), pelvic tilt (PT), C7 sagittal vertical axis, and sagittal radiographic parameters of hip and knee, significantly improved after surgery. On linear regression analysis, HHS and WOMAC correlated with LL and PT, respectively (β = 0.554 and p = 0.043 for correlation of HHS with LL; β = 1.573 and p = 0.021 for correlation of WOMAC with PT).

CONCLUSIONS

The current study demonstrated that lumbar fusion surgery may induce postoperative improvements in lower-extremity functional and radiological outcomes. However, among radiographic parameters, changes in LL and PT were the most strongly associated with lower-extremity PROMs.

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Konstantina Svokos, Lígia Batista-Silverman, Sarah J. Graber, Brent R. O’Neill, and Michael H. Handler

OBJECTIVE

Occult spinal dysraphism (OSD) is a common pediatric neurosurgical diagnosis rife with controversy surrounding both the screening of asymptomatic infants and the threshold to offer a prophylactic detethering operation. The authors sought to clarify international practice patterns with a survey of pediatric neurosurgeons.

METHODS

A survey asked pediatric neurosurgeons whether they would perform imaging in patients with a variety of cutaneous stigmata associated with OSD and whether they would offer prophylactic detethering surgery for asymptomatic patients with a variety of imaging findings on the OSD spectrum.

RESULTS

Completed surveys were received from 141 pediatric neurosurgeons. Broad consensus was demonstrated on the need for obtaining images in sample patients with more severe stigmata ranging from large lipoma with a skin appendage to focal dysplastic skin in the lumbar midline. Ninety percent of respondents would perform MRI for these patients. In contrast, for patients with a low-sacral dimple, flat hemangioma, and symmetric (Y-shaped) splaying of the intergluteal cleft, opinion on the need for imaging varied considerably (between 57% and 89% recommended imaging). Respondents differed on the type of imaging that they would perform, with 31% to 38% recommending ultrasound screening. The responses reflected less consensus on when to offer surgery to patients with simple spinal tethering (low-lying conus medullaris and fatty filum terminale). Both a lower level of the conus and increased thickness of the filum terminale affected decision-making.

CONCLUSIONS

The results of this survey showed significant consensus on the recommendation for screening imaging in patients with more dramatic cutaneous stigmata, although these stigmata are the rarest. A significant variance in opinions was reflected in the recommendation for imaging of the most common cutaneous stigmata. Consensus was also lacking on which lesions deserve prophylactic detethering surgery. Significant equipoise exists for future study of screening imaging and of surgical decision-making in patients with asymptomatic OSD and associated cutaneous stigmata.

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Miao Hu, Aining Lai, Zheng Zhang, Jingjing Chen, Tao Lin, Jun Ma, Ce Wang, Yichen Meng, and Xuhui Zhou

OBJECTIVE

Surgical management of scoliosis curves between 70° and 100° remains controversial. The authors designed this randomized controlled trial to validate the efficacy of intraoperative halo-femoral traction (IOHFT) in patients with adolescent idiopathic scoliosis (AIS), Cobb angles between 70° and 100°, and flexibility < 35%.

METHODS

The authors prospectively recruited and randomized 29 patients with severe AIS scheduled for posterior surgery into a traction group or control (nontraction) group. The primary outcome measures were operative time, blood loss, and length of hospital stay. Secondary outcomes included degree of spine deformity correction, traction-related complications, and health-related quality of life.

RESULTS

In the traction group, the average preoperative Cobb angle was 83.2°, with an average 20.6% flexibility. The average postoperative Cobb angle was 16.1° and the major curve was 18.3° at the final follow-up. In the control group, the average preoperative major curve was 80.3° with 22.8% flexibility. The average postoperative Cobb angle was 16.1° and the major curve was 18.1° at the final follow-up. The operative duration was 325.7 minutes for the traction group and 385.4 minutes for the control group (p = 0.018). Compared with the control group, the traction group had a 29.5% reduction in intraoperative blood loss and a significantly lower rate of blood transfusion (13.3% vs 50.0%, p = 0.033). There were no neurological complications in either group. One patient in the traction group had a superficial infection at the traction site.

CONCLUSIONS

Use of IOHFT contributed to significant reductions in operative time and blood transfusion requirements, with no added morbidity. It is an effective and safe method to assist correction of AIS curves between 70° and 100° and flexibility < 35%.

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Robert N. Holdefer, Christoph N. Seubert, Stanley A. Skinner, and Andrew T. Humbert

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Silky Chotai, Jeffrey L. Nadel, Katherine G. Holste, James M. Mossner, Brandon W. Smith, Joseph R. Kapurch, Karin M. Muraszko, Hugh J. L. Garton, Cormac O. Maher, and Jennifer M. Strahle

OBJECTIVE

The objective of this study was to understand the natural history of scoliosis in patients with Chiari malformation type I (CM-I) with and without syringomyelia.

METHODS

A retrospective review of data was conducted. Patients with CM-I were identified from a cohort of 14,118 individuals age 18 years or younger who had undergone MRI over an 11-year period at the University of Michigan. Patients eligible for study inclusion had a coronal curve ≥ 10° on radiography, associated CM-I with or without syringomyelia, and at least 1 year of clinical follow-up prior to any surgery. Curve magnitude at initial diagnosis, prior to posterior fossa decompression (PFD; if applicable), and at the last follow-up (prior to any surgical correction of scoliosis) was recorded, and clinical and radiographic characteristics were noted. The change in curve magnitude by 10° was defined as curve progression (increase by 10°) or regression (decrease by 10°).

RESULTS

Forty-three patients met the study inclusion criteria and were analyzed. About one-third (35%) of the patients presented with symptoms attributed to their CM-I. The mean degree of scoliosis at presentation was 32.6° ± 17.7°. Twenty-one patients (49%) had an associated syrinx. The mean tonsil position below the level of the foramen magnum was 9.8 ± 5.8 mm. Patients with a syrinx were more likely to have a curve > 20° (86% vs 41%, p = 0.002). Curve magnitude remained stable (≤ ±10°) in 77% of patients (33/43), progressed in 16% (7/43), and regressed in 7% (3/43). Mean age was higher (14.8 ± 0.59 years) among patients with regressed curves (p = 0.026). All regressed curves initially measured ≤ 20° (mean 14° ± 5.3°), and none of the patients with regressed curves had a syrinx. The change in curve magnitude was statistically similar in patients with (7.32° ± 17.7°) and without (5.32° ± 15.8°) a syrinx (p = 0.67). After a mean follow-up of 3.13 ± 2.04 years prior to surgery, 27 patients (63%) ultimately underwent posterior fossa or scoliosis correction surgery. For those who eventually underwent PFD only, the rate of change in curve magnitude prior to surgery was 0.054° ± 0.79°. The rate of change in curve magnitude was statistically similar before (0.054° ± 0.79°) and after (0.042° ± 0.33°) surgery (p = 0.45) for patients who underwent PFD surgery only.

CONCLUSIONS

The natural history of scoliosis in the presence of CM-I is variable, though most curves remained stable. All curves that regressed were ≤ 20° at initial diagnosis, and most patients in such cases were older at scoliosis diagnosis. Patients who underwent no surgery or PFD only had similar profiles for the change in curve magnitude, which remained relatively stable overall, as compared to patients who underwent PFD and subsequent fusion, who demonstrated curve progression. Among the patients with a syrinx, no curves regressed, most remained stable, and some progressed. Understanding this variability is a first step toward building a prediction model for outcomes for these patients.