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Ethan Cottrill, Zach Pennington, A. Karim Ahmed, Daniel Lubelski, Matthew L. Goodwin, Alexander Perdomo-Pantoja, Erick M. Westbroek, Nicholas Theodore, Timothy Witham and Daniel Sciubba

OBJECTIVE

Nonunion is a common complication of spinal fusion surgeries. Electrical stimulation technologies (ESTs)—namely, direct current stimulation (DCS), capacitive coupling stimulation (CCS), and inductive coupling stimulation (ICS)—have been suggested to improve fusion rates. However, the evidence to support their use is based solely on small trials. Here, the authors report the results of meta-analyses of the preclinical and clinical data from the literature to provide estimates of the overall effect of these therapies at large and in subgroups.

METHODS

A systematic review of the English-language literature was performed using PubMed, Embase, and Web of Science databases. The query of these databases was designed to include all preclinical and clinical studies examining ESTs for spinal fusion. The primary endpoint was the fusion rate at the last follow-up. Meta-analyses were performed using a Freeman-Tukey double arcsine transformation followed by random-effects modeling.

RESULTS

A total of 33 articles (17 preclinical, 16 clinical) were identified, of which 11 preclinical studies (257 animals) and 13 clinical studies (2144 patients) were included in the meta-analysis. Among preclinical studies, the mean fusion rates were higher among EST-treated animals (OR 4.79, p < 0.001). Clinical studies similarly showed ESTs to increase fusion rates (OR 2.26, p < 0.001). Of EST modalities, only DCS improved fusion rates in both preclinical (OR 5.64, p < 0.001) and clinical (OR 2.13, p = 0.03) populations; ICS improved fusion in clinical studies only (OR 2.45, p = 0.014). CCS was not effective at increasing fusion, although only one clinical study was identified. A subanalysis of the clinical studies found that ESTs increased fusion rates in the following populations: patients with difficult-to-fuse spines, those who smoke, and those who underwent multilevel fusions.

CONCLUSIONS

The authors found that electrical stimulation devices may produce clinically significant increases in arthrodesis rates among patients undergoing spinal fusion. They also found that the pro-arthrodesis effects seen in preclinical studies are also found in clinical populations, suggesting that findings in animal studies are translatable. Additional research is needed to analyze the cost-effectiveness of these devices.

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Surgical management of giant presacral schwannoma: systematic review of published cases and meta-analysis

Presented at the 2019 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Zach Pennington, Erick M. Westbroek, A. Karim Ahmed, Ethan Cottrill, Daniel Lubelski, Matthew L. Goodwin and Daniel M. Sciubba

OBJECTIVE

Giant presacral schwannomas are rare sacral tumors found in less than 1 of every 40,000 hospitalizations. Current management of these tumors is based solely upon case reports and small case series. In this paper the authors report the results of a systematic review of the available English literature on presacral schwannoma, focused on identifying the influence of tumor size, tumor morphology, surgical approach, and extent of resection (EOR) on recurrence-free survival and postoperative complications.

METHODS

The medical literature (PubMed and EMBASE) was queried for reports of surgically managed sacral schwannoma, either involving 2 or more contiguous vertebral levels or with a diameter ≥ 5 cm. Tumor size and morphology, surgical approach, EOR, intraoperative and postoperative complications, and survival data were recorded.

RESULTS

Seventy-six articles were included, covering 123 unique patients (mean age 44.1 ± 1.4 years, 50.4% male). The most common presenting symptoms were leg pain (28.7%), lower back pain (21.3%), and constipation (15.7%). Most surgeries used an open anterior-only (40.0%) or posterior-only (30%) approach. Postoperative complications occurred in 25.6% of patients and local recurrence was noted in 5.4%. En bloc resection significantly improved progression-free survival relative to subtotal resection (p = 0.03). No difference existed between en bloc and gross-total resection (GTR; p = 0.25) or among the surgical approaches (p = 0.66). Postoperative complications were more common following anterior versus posterior approaches (p = 0.04). Surgical blood loss was significantly correlated with operative duration and tumor volume on multiple linear regression (both p < 0.001).

CONCLUSIONS

Presacral schwannoma can reasonably be treated with either en bloc or piecemeal GTR. The approach should be dictated by lesion morphology, and recurrence is infrequent. Anterior approaches may increase the risk of postoperative complications.

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Paraspinal muscle size as an independent risk factor for proximal junctional kyphosis in patients undergoing thoracolumbar fusion

Presented at the 2019 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Zach Pennington, Ethan Cottrill, A. Karim Ahmed, Peter Passias, Themistocles Protopsaltis, Brian Neuman, Khaled M. Kebaish, Jeff Ehresman, Erick M. Westbroek, Matthew L. Goodwin and Daniel M. Sciubba

OBJECTIVE

Proximal junctional kyphosis (PJK) is a structural complication of spinal fusion in 5%–61% of patients treated for adult spinal deformity. In nearly one-third of these cases, PJK is progressive and requires costly surgical revision. Previous studies have suggested that patient body habitus may predict risk for PJK. Here, the authors sought to investigate abdominal girth and paraspinal muscle size as risk factors for PJK.

METHODS

All patients undergoing thoracolumbosacral fusion greater than 2 levels at a single institution over a 5-year period with ≥ 6 months of radiographic follow-up were considered for inclusion. PJK was defined as kyphosis ≥ 20° between the upper instrumented vertebra (UIV) and two supra-adjacent vertebrae. Operative and radiographic parameters were recorded, including pre- and postoperative sagittal vertical axis (SVA), sacral slope (SS), lumbar lordosis (LL), pelvic tilt, pelvic incidence (PI), and absolute value of the pelvic incidence–lumbar lordosis mismatch (|PI-LL|), as well as changes in LL, |PI-LL|, and SVA. The authors also considered relative abdominal girth and the size of the paraspinal muscles at the UIV.

RESULTS

One hundred sixty-nine patients met inclusion criteria. On univariate analysis, PJK was associated with a larger preoperative SVA (p < 0.001) and |PI-LL| (p = 0.01), and smaller SS (p = 0.004) and LL (p = 0.001). PJK was also associated with more positive postoperative SVA (p = 0.01), ΔSVA (p = 0.01), Δ|PI-LL| (p < 0.001), and ΔLL (p < 0.001); longer construct length (p = 0.005); larger abdominal girth–to-muscle ratio (p = 0.007); and smaller paraspinal muscles at the UIV (p < 0.001). Higher postoperative SVA (OR 1.1 per cm), smaller paraspinal muscles at the UIV (OR 2.11), and more aggressive reduction in |PI-LL| (OR 1.03) were independent predictors of radiographic PJK on multivariate logistic regression.

CONCLUSIONS

A more positive postoperative global sagittal alignment and smaller paraspinal musculature at the UIV most strongly predicted PJK following thoracolumbosacral fusion.

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Camilo A. Molina, Nicholas Theodore, A. Karim Ahmed, Erick M. Westbroek, Yigal Mirovsky, Ran Harel, Emanuele Orru’, Majid Khan, Timothy Witham and Daniel M. Sciubba

OBJECTIVE

Augmented reality (AR) is a novel technology that has the potential to increase the technical feasibility, accuracy, and safety of conventional manual and robotic computer-navigated pedicle insertion methods. Visual data are directly projected to the operator’s retina and overlaid onto the surgical field, thereby removing the requirement to shift attention to a remote display. The objective of this study was to assess the comparative accuracy of AR-assisted pedicle screw insertion in comparison to conventional pedicle screw insertion methods.

METHODS

Five cadaveric male torsos were instrumented bilaterally from T6 to L5 for a total of 120 inserted pedicle screws. Postprocedural CT scans were obtained, and screw insertion accuracy was graded by 2 independent neuroradiologists using both the Gertzbein scale (GS) and a combination of that scale and the Heary classification, referred to in this paper as the Heary-Gertzbein scale (HGS). Non-inferiority analysis was performed, comparing the accuracy to freehand, manual computer-navigated, and robotics-assisted computer-navigated insertion accuracy rates reported in the literature. User experience analysis was conducted via a user experience questionnaire filled out by operators after the procedures.

RESULTS

The overall screw placement accuracy achieved with the AR system was 96.7% based on the HGS and 94.6% based on the GS. Insertion accuracy was non-inferior to accuracy reported for manual computer-navigated pedicle insertion based on both the GS and the HGS scores. When compared to accuracy reported for robotics-assisted computer-navigated insertion, accuracy achieved with the AR system was found to be non-inferior when assessed with the GS, but superior when assessed with the HGS. Last, accuracy results achieved with the AR system were found to be superior to results obtained with freehand insertion based on both the HGS and the GS scores. Accuracy results were not found to be inferior in any comparison. User experience analysis yielded “excellent” usability classification.

CONCLUSIONS

AR-assisted pedicle screw insertion is a technically feasible and accurate insertion method.

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A. Karim Ahmed, Zachary Pennington, Camilo A. Molina, Yuanxuan Xia, C. Rory Goodwin and Daniel M. Sciubba

Effective en bloc resection of primary spinal tumors necessitates careful consideration of adjacent anatomical structures in order to achieve negative margins and reduce surgical morbidity. This can be particularly challenging in the cervical spine, where vital neurovascular and connective tissues are present in the region. Early multidisciplinary surgical planning that includes clinicians and engineers can both optimize surgical planning and enable a more feasible resection with oncological margins. The aim of the current work was to demonstrate two cases that involved multidisciplinary surgical planning for en bloc resection of primary cervical spine tumors, successfully utilizing 3D-printed patient models and neoadjuvant therapies.

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Ari M. Blitz, A. Karim Ahmed and Daniele Rigamonti

Because of his exceptional and pioneering contributions to the understanding and treatment of neurosurgical conditions, Walter Dandy is considered to be one of the founders of both neurosurgery and neuroradiology. In the field of hydrocephalus, Dandy developed revolutionary research models, imaging modalities, and operative procedures. His laboratory and clinical experiences at the Johns Hopkins Hospital, including the surgical treatment of hydrocephalus, are well illustrated in the publications he authored. Archival materials housed at the Johns Hopkins University School of Medicine provide a window into Dandy’s clinical experience and supplement the work published during his lifetime. His operative experience with hydrocephalus spanned 1915–1946 and comprised 381 surgeries. From this clinical experience, Dandy created much of the framework for modern diagnostic imaging and treatment of hydrocephalus.

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A. Karim Ahmed, Eduardo Martinez-del-Campo and Nicholas Theodore

The role of chief White House physician has traditionally been held by an individual with a background in a broad medical field, such as emergency medicine, family medicine, or internal medicine. Dr. Daniel Ruge, who served as the director of the Spinal Cord Injury Service for the Veterans Administration and was appointed during President Ronald Reagan’s first term, was the first neurosurgeon to become the chief White House physician. Aside from being the first neurosurgeon to serve in this capacity, Dr. Ruge also stands apart from others who have held this esteemed position because of how he handled Reagan’s care after an attempt was made on the then-president’s life. Instead of calling upon leading medical authorities of the time to care for the president, Dr. Ruge instead decided that Reagan should be treated as any trauma patient would be treated. Dr. Ruge’s actions after the assassination attempt on President Reagan resulted in the rapid, smooth recovery of the then-president. Daniel Ruge’s background, his high-profile roles and heavy responsibilities, and his critical decision-making are characteristics that make his role in the history of medicine and of neurosurgery unique.

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Corinna C. Zygourakis, A. Karim Ahmed, Samuel Kalb, Alex M. Zhu, Ali Bydon, Neil R. Crawford and Nicholas Theodore

The Excelsius GPS (Globus Medical, Inc.) was approved by the FDA in 2017. This novel robot allows for real-time intraoperative imaging, registration, and direct screw insertion through a rigid external arm—without the need for interspinous clamps or K-wires. The authors present one of the first operative cases utilizing the Excelsius GPS robotic system in spinal surgery. A 75-year-old man presented with severe lower back pain and left leg radiculopathy. He had previously undergone 3 decompressive surgeries from L3 to L5, with evidence of instability and loss of sagittal balance. Robotic assistance was utilized to perform a revision decompression with instrumented fusion from L3 to S1. The usage of robotic assistance in spinal surgery may be an invaluable resource in minimally invasive cases, minimizing the need for fluoroscopy, or in those with abnormal anatomical landmarks.

The video can be found here: https://youtu.be/yVI-sJWf9Iw.

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Hannah M. Carl, A. Karim Ahmed, Nancy Abu-Bonsrah, Rafael De la Garza Ramos, Eric W. Sankey, Zachary Pennington, Ali Bydon, Timothy F. Witham, Jean-Paul Wolinsky, Ziya L. Gokaslan, Justin M. Sacks, C. Rory Goodwin and Daniel M. Sciubba

OBJECTIVE

Resection of metastatic spine tumors can improve patients’ quality of life by addressing pain or neurological compromise. However, resections are often complicated by wound dehiscence, infection, instrumentation failures, and the need for reoperation. Moreover, when reoperations are needed, the most common indication is surgical site infection and wound breakdown. In turn, wound reoperations increase morbidity as well as the length and cost of hospitalization. The aim of this study was to examine perioperative risk factors associated with increased rate of wound reoperations after metastatic spine tumor resection.

METHODS

A retrospective study of patients at a single institution who underwent metastatic spine tumor resection between 2003 and 2013 was conducted. Factors with a p value < 0.200 in a univariate analysis were included in the multivariate model.

RESULTS

A total of 159 patients were included in this study. Karnofsky Performance Scale score > 70, smoking status, hypertension, thromboembolic events, hyperlipidemia, increasing number of vertebral levels, and posterior approach were included in the multivariate analysis. Thromboembolic events (95% CI 1.19–48.5, p = 0.032) and number of levels involved were independently associated with increased wound reoperation rates in the multivariate model. For each additional spinal level involved, the risk for wound reoperations increased by 21% (95% CI 1.03–1.43, p = 0.018).

CONCLUSIONS

Although wound complications and subsequent reoperations are potential risks for all patients with metastatic spine tumor, due to adjuvant radiotherapy and other medical comorbidities, this study identified patients with thromboembolic events or those requiring a larger incision as being at the highest risk. Measures intended to decrease the occurrence of perioperative venous thromboembolism and to improve wound care, especially for long incisions, may decrease wound-related revision surgeries in this vulnerable group of patients.

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Rachel Sarabia-Estrada, Alejandro Ruiz-Valls, Sagar R. Shah, A. Karim Ahmed, Alvaro A. Ordonez, Fausto J. Rodriguez, Hugo Guerrero-Cazares, Ismael Jimenez-Estrada, Esteban Velarde, Betty Tyler, Yuxin Li, Neil A. Phillips, C. Rory Goodwin, Rory J. Petteys, Sanjay K. Jain, Gary L. Gallia, Ziya L. Gokaslan, Alfredo Quinones-Hinojosa and Daniel M. Sciubba

OBJECTIVE

Chordoma is a slow-growing, locally aggressive cancer that is minimally responsive to conventional chemotherapy and radiotherapy and has high local recurrence rates after resection. Currently, there are no rodent models of spinal chordoma. In the present study, the authors sought to develop and characterize an orthotopic model of human chordoma in an immunocompromised rat.

METHODS

Thirty-four immunocompromised rats were randomly allocated to 4 study groups; 22 of the 34 rats were engrafted in the lumbar spine with human chordoma. The groups were as follows: UCH1 tumor–engrafted (n = 11), JHC7 tumor–engrafted (n = 11), sham surgery (n = 6), and intact control (n = 6) rats. Neurological impairment of rats due to tumor growth was evaluated using open field and locomotion gait analysis; pain response was evaluated using mechanical or thermal paw stimulation. Cone beam CT (CBCT), MRI, and nanoScan PET/CT were performed to evaluate bony changes due to tumor growth. On Day 550, rats were killed and spines were processed for H & E–based histological examination and immunohistochemistry for brachyury, S100β, and cytokeratin.

RESULTS

The spine tumors displayed typical chordoma morphology, that is, physaliferous cells filled with vacuolated cytoplasm of mucoid matrix. Brachyury immunoreactivity was confirmed by immunostaining, in which samples from tumor-engrafted rats showed a strong nuclear signal. Sclerotic lesions in the vertebral body of rats in the UCH1 and JHC7 groups were observed on CBCT. Tumor growth was confirmed using contrast-enhanced MRI. In UCH1 rats, large tumors were observed growing from the vertebral body. JHC7 chordoma–engrafted rats showed smaller tumors confined to the bone periphery compared with UCH1 chordoma–engrafted rats. Locomotion analysis showed a disruption in the normal gait pattern, with an increase in the step length and duration of the gait in tumor-engrafted rats. The distance traveled and the speed of rats in the open field test was significantly reduced in the UCH1 and JHC7 tumor–engrafted rats compared with controls. Nociceptive response to a mechanical stimulus showed a significant (p < 0.001) increase in the paw withdrawal threshold (mechanical hypalgesia). In contrast, the paw withdrawal response to a thermal stimulus decreased significantly (p < 0.05) in tumor-engrafted rats.

CONCLUSIONS

The authors developed an orthotopic human chordoma model in rats. Rats were followed for 550 days using imaging techniques, including MRI, CBCT, and nanoScan PET/CT, to evaluate lesion progression and bony integrity. Nociceptive evaluations and locomotion analysis were performed during follow-up. This model reproduces cardinal signs, such as locomotor and sensory deficits, similar to those observed clinically in human patients. To the authors’ knowledge, this is the first spine rodent model of human chordoma. Its use and further study will be essential for pathophysiology research and the development of new therapeutic strategies.