Ten-Step Minimally Invasive Spine Lumbar Decompression and Dural Repair Through Tubular Retractors

BACKGROUND: Minimally invasive spine (MIS) surgery utilizing tubular retractors has become an increasingly popular approach for decompression in the lumbar spine. However, a better understanding of appropriate indications, efficacious surgical techniques, limitations, and complication management is required to effectively teach the procedure and to facilitate the learning curve.

OBJECTIVE: To describe our experience and recommendations regarding tubular surgery for lumbar disc herniations, foraminal compression with unilateral radiculopathy, lumbar spinal stenosis, synovial cysts, and dural repair.

METHODS: We reviewed our experience between 2008 and 2014 to develop a step-by-step description of the surgical techniques and complication management, including dural repair through tubes, for the 4 lumbar pathologies of highest frequency. We provide additional supplementary videos for dural tear repair, laminotomy for bilateral decompression, and synovial cyst resection.

RESULTS: Our overview and complementary materials document the key technical details to maximize the success of the 4 MIS surgical techniques. The review of our experience in 331 patients reveals technical feasibility as well as satisfying clinical results, with no postoperative complications associated with cerebrospinal fluid leaks, 1 infection, and 17 instances (5.1%) of delayed fusion.

CONCLUSION: MIS surgery through tubular retractors is a safe and effective alternative to traditional open or microsurgical techniques for the treatment of lumbar degenerative disease. Adherence to strict microsurgical techniques will allow the surgeon to effectively address bilateral pathology while preserving stability and minimizing complications.

Pediatric Stroke: A Review of Common Etiologies and Management Strategies

Pediatric stroke is an important cause of mortality and morbidity in children. There is a paucity of clinical trials pertaining to pediatric stroke management, and solidified universal guidelines are not established for children the way they are for the adult population. Diagnosis of pediatric stroke can be challenging, and it is often delayed or mischaracterized, which can result in worse outcomes. Understanding risks and appropriate therapy is paramount to improving care.

Outcome and prognostication after cardiac arrest

The outcome after out-of-hospital cardiac arrest has historically been grim at best. The current overall survival rate of patients admitted to a hospital is approximately 10%, making cardiac arrest one of the leading causes of death in the United States. The situation is improving with the incorporation of therapeutic temperature modulation, aggressive prevention of secondary brain injury, and improved access to advanced cardiovascular support, all of which have decreased mortality and allowed for better outcomes. Mortality after cardiac arrest is often the direct result of active withdrawal of life-sustaining therapy based on the perception that neurological recovery is not possible. This reality highlights the importance of providing accurate estimates of neurological prognosis to decision makers when discussing goals of care. The current standard of care for assessing neurological status in patients with hypoxic-ischemic encephalopathy emphasizes a multimodal approach that includes five elements: (1) neurological examination off sedation, (2) continuous electroencephalography, (3) serum neuron-specific enolase levels, (4) magnetic resonance brain imaging, and (5) somatosensory-evoked potential testing. Sophisticated decision support systems that can integrate these clinical, imaging, and biomarker and neurophysiologic data and translate it into meaningful projections of neurological outcome are urgently needed.

Novel MIS 3D NAV Single Step Pedicle Screw System (SSPSS): Workflow, Accuracy and Initial Clinical Experience

STUDY DESIGN

Prospective case series.

OBJECTIVE

SSPSS (single step pedicle screw system) was developed for minimally invasive spine surgery. We performed this study to report on safety, workflow, and our initial clinical experience with this novel technique.

METHODS

The prospective study was conducted on patients who underwent pedicle screw fixation between October 2017 and April 2018 using a novel single step 3D navigated pedicle screw system for MIS. Outcome measurements were obtained from intraoperative computerized tomography. The images were evaluated to determine pedicle wall penetration. We used a grading system to assess the severity of the pedicle wall penetration. Breaches were classified as grade 1 (<2 mm), grade 2 (2-4 mm), or grade 3 (<4 mm),¹ and as cranial, caudal, medial, and lateral.

RESULTS

Our study includes 135 screws in 24 patients. SSPSS eliminated K-wires and multiple steps traditionally necessary for MIS pedicle screw insertion. The median time per screw was 2.45 minutes. 3 screws were corrected intraoperatively. Pedicle wall penetration occurred in 14 screws (10%). Grade 1 breaches occurred in 4 screws (3%) and grade 2 breaches occurred in 10 screws (7%). Lateral breaches were observed more often than medial breaches. The accuracy rate in our study was 90% (Grade 0 breach). No revision surgeries were needed and no complications occurred.

CONCLUSIONS

Our study suggests that SSPSS could be a safe, accurate, and efficient tool. Our accuracy rate is comparable to that found in the literature.

The Effect of Frailty and Patient Comorbidities on Outcomes After Acute Subdural Hemorrhage: A Preliminary Analysis

BACKGROUND

Frailty is associated with worse outcomes across a variety of neurosurgical diseases. However, its effect on acute subdural hemorrhage (aSDH) outcomes is unclear. The goal of this study is to compare 3 measures of frailty with the gold standard (i.e., initial Glasgow Coma Scale [iGCS] score) for predicting outcomes after aSDH.

METHODS

Patients who presented between January 2016 and June 2018 were retrospectively identified based on International Classification of Diseases codes for aSDH. Patients' modified Frailty Index (mFI), temporalis muscle thickness (TMT), and age-adjusted Charlson Comorbidity Index (CCI) were calculated. Primary end points were death and discharge home.

RESULTS

Of 167 patients included, the mean age was 63.4 ± 1.9 years, the average CCI was 3.4 ± 0.2, mFI was 1.4 ± 0.1, TMT was 7.1 ± 0.2 mm, and iGCS score was 11.9 ± 0.3. Sixty-nine patients (41.3%) were discharged home and 32 (19.2%) died during hospitalization. In multivariate analysis, decreasing iGCS score (odds ratio [OR], 0.84; 95% confidence interval [CI], 0.74-0.96; P = 0.0112) and midline shift (OR, 1.27; 95% CI, 1.08-1.50; P = 0.0048), but not age or frailty, predicted mortality. In addition to iGCS score (OR, 1.26; 95% CI, 1.10-1.44; P = 0.0011), lower CCI (OR, 0.32; 95% CI, 0.14-0.74; P = 0.0071) and larger TMT (OR, 2.63; 95% CI, 1.16-5.99; P = 0.0210) independently predicted increased rates of discharge home. mFI was not independently associated with either primary end point in multivariate analysis.

CONCLUSIONS

iGCS score predicts both mortality and discharge location after aSDH better than do age or frailty. However, CCI and TMT, but not mFI, are useful prognostic indicators of discharge to home after aSDH. The iGCS score should continue to be the primary prediction tool for patients with aSDH; however, frailty may be useful for resource allocation, especially when nearing discharge.

The Effect of Frailty versus Initial Glasgow Coma Score in Predicting Outcomes Following Chronic Subdural Hemorrhage: A Preliminary Analysis

Background Initial Glasgow Coma Score (iGCS) is a well-known predictor of adverse outcomes following chronic subdural hemorrhage (cSDH). Frailty, i.e. a reduced physiologic reserve, is associated with poorer outcomes across the surgical literature, however, there is no consensus on the best measure of frailty. To date, no study has compared frailty's ability to predict cSDH outcomes versus iGCS. The goal of this study was to, therefore, examine the prognostic value of the 5- (mFI-5) and 11-factor (mFI-11) modified frailty index, and Charlson Comorbidity Index (CCI) versus iGCS following cSDH. Methods Between January, 2016 and June, 2018, patients who presented to the emergency department with cSDH were retrospectively identified using the International Classification of Diseases (ICD) codes. mFI-5, mFI-11, and CCI scores were calculated using patient baseline characteristics. Primary endpoints were death and discharge home and subgroup analyses were performed among operative cSDH. Univariate and multivariate logistic regressions were used to determine predictors of primary endpoints. Results Of the 109 patients identified, the average age was 72.6±1.6 years and the majority (69/109, 63.3%) were male. The average CCI, mFI-5, and mFI-11 were 4.5 ±0.2, 1.5 ±0.1, and 2.2 ±0.1, respectively. Fifty (45.9%) patients required surgical intervention, 11 (10.1%) died, and 48 (43.4%) were discharged home. In the overall cohort, while the only multivariate predictor of mortality was iGCS (OR=0.58; 95%CI:0.44-0.77; p=0.0001), the CCI (OR=0.73; 95%CI:0.58-0.92; p=0.0082) was a superior predictor of discharge home compared to iGCS (OR=1.46; 95%CI:1.13-1.90; p=0.0041). Conversely, among those who received an operative intervention, the CCI, but not iGCS, independently predicted both mortality (OR=4.24; 95%CI:1.01-17.86; p=0.0491) and discharge home (OR=0.55; 95%CI:0.33-0.90; p=0.0170). Neither mFI nor age predicted primary outcomes in multivariate analysis. Conclusion While frailty is associated with worse surgical outcomes, the clinical utility of the mFI-5, mFI-11, and CCI in cSDH is unclear. We show that the iGCS is an overall superior predictor of mortality following cSDH but is outperformed by the CCI after operative intervention. Similarly, the CCI is the superior predictor of discharge home in cSDH patients overall and following an operative intervention. These results indicate that while the iGCS best predicts mortality overall, the CCI may be considered when prognosticating post-operative course and hospital disposition.

Occipital artery-to-PICA bypass: how I do it

BACKGROUND

Posterior inferior cerebellar artery (PICA) aneurysms are uncommon, and their management is challenging because of the complex angioarchitecture of the PICA and the frequently nonsaccular aneurysm presentation. Endovascular therapy may not be feasible.

METHODS

We describe our technique of clip trapping with occipital artery (OA)-to-PICA bypass to treat a PICA aneurysm. Because the aneurysm affected the ipsilateral, dominant PICA, an OA-PICA bypass was chosen to ensure adequate flow and reduce risk to the contralateral PICA supply.

CONCLUSION

The OA-PICA anastomosis is a safe and effective method to successfully achieve flow preservation with bypass reconstruction and aneurysm trapping.

Frontotemporal Approach for Spheno-Orbital Meningioma and Orbital Compartment Resection: Technical Case Instruction: 2-Dimensional Operative Video

BACKGROUND AND IMPORTANCE

Spheno-orbital meningiomas (SOMs) pose a challenge to the skull base neurosurgeon because of their variable presentation and involvement of critical structures within the orbit. There is no consensus on optimal management of these patients and how to achieve maximal safe resection. The authors share an illustrative case with an accompanying video to demonstrate their aggressive approach to resect SOMs and their intraorbital components.

CLINICAL PRESENTATION

A 75-year-old-woman presented with progressive vision loss and proptosis. Magnetic resonance imaging was consistent with a large, left-sided sphenoid wing meningioma with extension to the orbital wall and compression of the optic nerve medially. The patient elected to undergo surgical excision and optic nerve decompression. She did well postoperatively with resolution of proptosis and good resection margins on follow-up imaging.

CONCLUSION

Aggressive resection of SOMs is possible with an understanding of the underlying anatomy. Familiarity with the orbit can facilitate a maximal safe resection with optic nerve decompression.

Update on Management of Dural Arteriovenous Fistulas

Abstract: Dural Arteriovenous Fistulas (AVF) represent about 10% of all intracranial vascular lesions. Although they seem benign in nature, the presence of retrograde venous makes them aggressive, with a high risk of complications. Patients may be clinically asymptomatic or experience symptoms ranging from mild to severe hemorrhage, depending on their location. Different treatments are available, but recently, the development of catheter intervention allows most patients to be cured with transcatheter embolization. Stereotactic radiosurgery achieves excellent rates of obliteration for low-grade lesions. In this review, we try to highlight the recent advances in the management of dural AVF.

History, Current Techniques, and Future Prospects of Surgery to the Sellar and Parasellar Region

The sellar and parasellar region can be affected by diverse pathologies. The deep-seated location and surrounding critical neurovascular structures make treatment challenging; there is no singular, optimal approach for management. The history and development of transcranial and transsphenoidal approaches by pioneers in skull base surgery were largely aimed at treating pituitary adenomas, which are the most common lesions of the sella. This review explores the history of sellar surgery, the most commonly used approaches today, and future considerations for surgery of the sellar/parasellar region.

Cardiac arrest in spontaneous subarachnoid hemorrhage and associated outcomes

OBJECTIVE

The authors sought to analyze a large, publicly available, nationwide hospital database to further elucidate the impact of cardiopulmonary arrest (CA) in association with subarachnoid hemorrhage (SAH) on short-term outcomes of mortality and discharge disposition.

METHODS

This retrospective cohort study was conducted by analyzing de-identified data from the National (Nationwide) Inpatient Sample (NIS). The publicly available NIS database represents a 20% stratified sample of all discharges and is powered to estimate 95% of all inpatient care delivered across hospitals in the US. A total of 170,869 patients were identified as having been hospitalized due to nontraumatic SAH from 2008 to 2014.

RESULTS

A total of 5415 patients (3.2%) were hospitalized with an admission diagnosis of CA in association with SAH. Independent risk factors for CA included a higher Charlson Comorbidity Index score, hospitalization in a small or nonteaching hospital, and a Medicaid or self-pay payor status. Compared with patients with SAH and not CA, patients with CA-SAH had a higher mean NIS Subarachnoid Severity Score (SSS) ± SD (1.67 ± 0.03 vs 1.13 ± 0.01, p < 0.0001) and a vastly higher mortality rate (82.1% vs 18.4%, p < 0.0001). In a multivariable model, age, NIS-SSS, and CA all remained significant independent predictors of mortality. Approximately 18% of patients with CA-SAH survived and were discharged to a rehabilitation facility or home with health services, outcomes that were most predicted by chronic disease processes and large teaching hospital status.

CONCLUSIONS

In the largest study of its kind, CA at onset was found to complicate roughly 3% of spontaneous SAH cases and was associated with extremely high mortality. Despite this, survival can still be expected in approximately 18% of patients.

Hypophysitis: Defining Histopathologic Variants and a Review of Emerging Clinical Causative Entities

Inflammatory disease of the pituitary gland is known as hypophysitis. There are multiple histological subtypes, the most common being lymphocytic, and the pathogenesis is variable and diverse. Hypophysitis can be primary and idiopathic or autoimmune related, or secondary to local lesions, systemic disease, medications, and more. Although hypophysitis was previously accepted as an exceedingly rare diagnosis, a greater understanding of the disease process and new insights into possible etiologic sources have contributed to an increased frequency of recognition. This review provides an overview of hypophysitis, its causes, and detection strategies and management.

In-out-in technique for petrosal sinus dural arteriovenous fistula obliteration: How I Do It

BACKGROUND

Dural arteriovenous fistulas (dAVFs) at the superior petrosal sinus are a rare but important subtype that pose a high risk of mortality and morbidity. Treatment for these lesions can be challenging with stand-alone endovascular methods.

METHODS

We describe our "in-out-in" technique for disconnecting dAVFs at the superior petrosal sinus, which includes definitive sacrifice of the superior petrosal sinus and the transverse sigmoid sinus, if involved. This method achieves complete fistula obliteration and minimizes recurrence risk with new arterial feeders.

CONCLUSIONS

The in-out-in technique is a safe and effective approach for the treatment of dAVFs involving the superior petrosal sinus.

Extended Transsphenoidal Approach for Gross Total Resection of Hypothalamic Tumor

Tumors of the optic pathway and/or hypothalamus are uncommon, and the majority occur in patients with neurofibromatosis type 1.1,2 These lesions can be managed with a "watch-and-wait" approach; however, when treatment is indicated, the optimal strategy is wholly case dependent. We present a 22-year-old female patient with neurofibromatosis type 1 who had a partially cystic mass within the right mamillary body (Video 1). The mass was present on prior imaging but had increased in size and was newly enhancing with evidence of mass effect on the right optic tract. Given her history and the lesion's progression, treatment was recommended. The patient elected for surgery over radiation. Preoperatively, there were no visual field deficits or signs of hypopituitarism. We undertook a unilateral, extended transsphenoidal approach. Additional bony removal of the tuberculum sellae and planum sphenoidale enabled greater exposure of the anterior cranial fossa. The circular sinus was cauterized and divided for visualization of the pituitary stalk and clear identification of the hypothalamus. This provided an operative corridor superior to the pituitary gland and just beneath the optic nerves. The procedure proceeded without complication, and gross total resection was achieved. Postoperative imaging demonstrated gross total resection with a normal-appearing pituitary gland. Of note, the patient did experience mildly elevated postoperative sodium and was treated with desmopressin for transient diabetes insipidus. Twelve- and 24-month follow-up imaging showed no recurrence. The extended transsphenoidal approach used here offers a safe and suitable working corridor to achieve total resection of hypothalamic lesions without injury to the pituitary gland.

Half-and-Half Approach for Multiple Aneurysms at the Superior Cerebellar and Middle Cerebral Arteries

Aneurysms at the superior cerebellar artery (SCA) are commonly treated endovascularly because of their location around the basilar artery,1,2 but they are not intimately related with thalamoperforators. Therefore in younger patients, those with wide-necked aneurysms, or those with multiple ipsilateral aneurysms, surgery remains a treatment option.3 We present a 52-year-old woman with dizziness in whom multiple, unruptured intracranial aneurysms were identified. Imaging demonstrated a 9-mm right-sided SCA aneurysm and 5-mm right and mirror 3-mm left M1 segment middle cerebral artery aneurysms. The patient gave consent to undergo surgery after counseling regarding her treatment options. A pterional and temporal craniotomy was performed to allow for half-and-half subtemporal and transsylvian approaches (Video 1). Here, we discuss the nuances of the approach related to the anatomy of SCA aneurysms. The challenges of the surgery can be mediated with techniques including division of the tentorium for enhanced exposure and early proximal control with temporary clinping or the use of adenosine (cardiac arrest). Our patient remained neurologically stable postoperatively and in 1-year follow-up. SCA aneurysms are easily visualized by the subtemporal and transsylvian approaches; they are frequently located adjacent to the posterior cerebral artery above and the SCA below. A modified transcavernous approach using the orbitozygomatic craniotomy has been described for access to basilar tip aneurysms.4 While comparable, this case demonstrates the efficient workflow to clip multiple aneurysms using a single, combined approach. In patients with multiple aneurysms presenting ipsilaterally or with comorbid conditions that complicate endovascular embolization, surgery should be considered as a definitive and safe treatment strategy. The patient consented to publication.

Critical Care of Spinal Cord Injury

PURPOSE OF REVIEW

Spinal cord injury (SCI) is a major cause of morbidity and mortality, posing a significant financial burden on patients and the healthcare system. While little can be done to reverse the primary mechanical insult, minimizing secondary injury due to ischemia and inflammation and avoiding complications that adversely affect neurologic outcome represent major goals of management. This article reviews important considerations in the acute critical care management of SCI to improve outcomes.

RECENT FINDINGS

Neuroprotective agents, such as riluzole, may allow for improved neurologic recovery but require further investigation at this time. Various forms of neuromodulation, such as transcranial magnetic stimulation, are currently under investigation. Early decompression and stabilization of SCI is recommended within 24 h of injury when indicated. Spinal cord perfusion may be optimized with a mean arterial pressure goal from a lower limit of 75-80 to an upper limit of 90-95 mmHg for 3-7 days after injury. The use of corticosteroids remains controversial; however, initiation of a 24-h infusion of methylprednisolone 5.4 mg/kg/hour within 8 h of injury has been found to improve motor scores. Attentive pulmonary and urologic care along with early mobilization can reduce in-hospital complications.

Far lateral craniotomy for disconnection of vertebral dural arteriovenous fistula: how I do it

BACKGROUND

Craniocervical junction (CCJ) vascular abnormalities can be challenging to treat because of the surrounding density of critical neurovascular anatomy. Although most dural arteriovenous fistulas (dAVFs) are now treated with endovascular surgery, dAVFs near the CCJ are often better suited for microsurgical obliteration with precise vascular control.

METHODS

We describe our microsurgical approach to treating dAVFs at the CCJ. This includes a far-lateral approach with a small incision centered over the transverse process of the atlas and circumferential skeletonization of the vertebral artery in addition to clipping the fistula to limit lesion recurrence.

CONCLUSIONS

Definitive microsurgical treatment of CCJ dAVFs can be accomplished using a minimally invasive approach.

Natural History of Degenerative Spondylolisthesis: A Systematic Review and Meta-analysis

OBJECTIVE

The optimal treatment algorithm for patients with degenerative lumbar spondylolisthesis has not been clarified. Part of the reason for this is that the natural history of degenerative spondylolisthesis (DS) has not been sufficiently studied. Comprehension of the natural history is essential for surgical decision making. We aimed to determine 1) the proportion of patients that develop de novo DS during follow-up; and 2) the proportion of patients with progression of preexistent DS by conducting a systematic review and meta-analysis of the literature.

METHODS

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Ovid, EMBASE, and the Cochrane Library were searched from their inception through April 2022. Demographic values of the study populations, grade of slip, rate of slippage before and after the follow-up period, and percentage of patients with slip in the populations at baseline and after follow-up were the extracted parameters.

RESULTS

Of the 1909 screened records, eventually 10 studies were included. Of these studies, 5 reported the development of de novo DS and 9 reported on the progression of preexistent DS. Proportions of patients developing de novo DS ranged from 12% to 20% over a period ranging from 4 to 25 years. The proportion of patients with progression of DS ranged from 12% to 34% over a period ranging from 4 to 25 years.

CONCLUSIONS

Systematic review and metanalysis of DS on the basis of radiologic parameters revealed both an increasing incidence over time and an increasing progression of the slip rate in up to a third of the patients older than 25 years, which is important for counseling patients and surgical decision making. Importantly, two thirds of patients did not experience slip progression.

Adult Trauma Patients With Thoracolumbar Injury Classification and Severity Score of 4: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

Evaluate characteristics of patients with thoracolumbar injury classification and severity (TLICS) score of 4 (To4) severity traumatic thoracolumbar injury.

SUMMARY OF BACKGROUND DATA

The TLICS score is used to predict the need for operative versus nonoperative management in adult patients with traumatic thoracolumbar injury. Ambiguity exists in its application and score categorization.

METHODS

A systematic review of the literature was performed. The databases of MEDLINE, Embase, Web of Science, and Cochrane Review were queried. Studies included adults with traumatic thoracolumbar injury with assigned TLICS score and description of management strategy.

RESULTS

A total of 16 studies met inclusion criteria representing 1911 adult patients with traumatic thoracolumbar injury. There were 503 (26.32%) patients with To4, of which 298 (59.24%) were operative. Studies focusing on the thoracolumbar junction and AO Type A fracture morphology had To4 patient incidences of 11.15% and 52.94%, respectively. Multiple studies describe better quality of life, pain scores, and radiographic outcomes in To4 who underwent operative treatment patients.

CONCLUSION

To4 injuries are more commonly AO Type A and located in the thoracolumbar junction in adult patients with traumatic thoracolumbar injury. Despite ambiguous recommendations regarding treatment provided by TLICS, outcomes favor operative intervention in this subset of traumatic thoracolumbar injury patients.

Superior discrimination of the Risk Analysis Index compared with the 5-item modified frailty index in 30-day outcome prediction after anterior cervical discectomy and fusion

OBJECTIVE

The objective of this paper was to compare the predictive ability of the recalibrated Risk Analysis Index (RAI-rev) with the 5-item modified frailty index-5 (mFI-5) for postoperative outcomes of anterior cervical discectomy and fusion (ACDF).

METHODS

This study was performed using data of adult (age > 18 years) ACDF patients obtained from the National Surgical Quality Improvement Program database during the years 2015-2019. Multivariate modeling and receiver operating characteristic (ROC) curve analysis, including area under the curve/C-statistic calculation with the DeLong test, were performed to evaluate the comparative discriminative ability of the RAI-rev and mFI-5 for 5 postoperative outcomes.

RESULTS

Both the RAI-rev and mFI-5 were independent predictors of increased postoperative mortality and morbidity in a cohort of 61,441 ACDF patients. In the ROC analysis for 30-day mortality prediction, C-statistics indicated a significantly better performance of the RAI-rev (C-statistic = 0.855, 95% CI 0.852-0.858) compared with the mFI-5 (C-statistic = 0.684, 95% CI 0.680-0.688) (p < 0.001, DeLong test). The results were similar for postoperative ACDF morbidity, Clavien-Dindo grade IV complications, nonhome discharge, and reoperation, demonstrating the superior discriminative ability of the RAI-rev compared with the mFI-5.

CONCLUSIONS

The RAI-rev demonstrates superior discrimination to the mFI-5 in predicting postoperative ACDF mortality and morbidity. To the authors' knowledge, this is the first study to document frailty as an independent risk factor for postoperative mortality after ACDF. The RAI-rev has conceptual fidelity to the frailty phenotype and may be more useful than the mFI-5 in preoperative ACDF risk stratification. Prospective validation of these findings is necessary, but patients with high RAI-rev scores may benefit from knowing that they might have an increased surgical risk for ACDF morbidity and mortality.