Risk factors for spinal cord injury during surgery for spinal deformity

Timing of intraoperative neurophysiological monitoring (IONM) recovery and clinical recovery after termination of pediatric spinal deformity surgery due to loss of IONM signals

BACKGROUND CONTEXT

Intraoperative neurophysiological monitoring (IONM) is used to reduce the risk of spinal cord injury during pediatric spinal deformity surgery. Significant reduction and/or loss of IONM signals without immediate recovery may lead the surgeon to acutely abort the case. The timing of when monitorable signals return remains largely unknown.

PURPOSE

The goal of this study was to investigate the correlation between IONM signal loss, clinical examination, and subsequent normalization of IONM signals after aborted pediatric spinal deformity surgery to help determine when it is safe to return to the operating room.

STUDY DESIGN/SETTING

This is a multicenter, multidisciplinary, retrospective study of pediatric patients (<18 years old) undergoing spinal deformity surgery whose surgery was aborted due to a significant reduction or loss of IONM potentials.

PATIENT SAMPLE

Sixty-six patients less than 18 years old who underwent spinal deformity surgery that was aborted due to IONM signal loss were enrolled into the study.

OUTCOME MEASURES

IONM data, operative reports, and clinical examinations were investigated to determine the relationship between IONM loss, clinical examination, recovery of IONM signals, and clinical outcome.

METHODS

Information regarding patient demographics, deformity type, clinical history, neurologic and ambulation status, operative details, IONM information (eg, quality of loss [SSEPs, MEPs], laterality, any recovery of signals, etc.), intraoperative wake-up test, postoperative neurologic exam, postoperative imaging, and time to return to the operating were all collected. All factors were analyzed and compared with univariate and multivariate analysis using appropriate statistical analysis.

RESULTS

Sixty-six patients were enrolled with a median age of 13 years [IQR 11-14], and the most common sex was female (42/66, 63.6%). Most patients had idiopathic scoliosis (33/66, 50%). The most common causes of IONM loss were screw placement (27/66, 40.9%) followed by rod correction (19/66, 28.8%). All patients had either complete bilateral (39/66, 59.0%), partial bilateral (10/66, 15.2%) or unilateral (17/66, 25.8%) MEP loss leading to termination of the case. Overall, when patients were returned to the operating room 2 weeks postoperatively, nearly 75% (40/55) had monitorable IONM signals. Univariate analysis demonstrated that bilateral SSEP loss (p=.019), bilateral SSEP and MEP loss (p=.022) and delayed clinical neurologic recovery (p=.008) were significantly associated with having unmonitorable IONM signals at repeat surgery. Multivariate regression analysis demonstrated that delayed clinical neurologic recovery (> 72 hours) was significantly associated with unmonitorable IONM signals when returned to the operating room (p=.006). All patients ultimately made a full neurologic recovery.

CONCLUSIONS

In children whose spinal deformity surgery was aborted due to intraoperative IONM loss, there was a strong correlation between combined intraoperative SSEP/MEP loss, the magnitude of IONM loss, the timing of clinical recovery, and the time of electrophysiological IONM recovery. The highest likelihood of having a prolonged postoperative neurological deficit and undetectable IONM signals upon return to the OR occurs with bilateral complete loss of SSEPs and MEPs.

Facilitation of motor evoked potentials after tetanic peripheral nerve stimulation

OBJECTIVE

Tetanic stimulation of a peripheral nerve prior to transcranial electrical stimulation (TES) may enhance motor evoked potential (MEP) amplitudes. The purpose of this study was to investigate the post-tetanic MEP (p-MEP) technique in improving MEP amplitudes.

METHODS

Conventional TES MEPs (c-MEP) and p-MEPs with left upper limb stimulation (p-MEPUL) or left lower limb stimulation (p-MEPLL) were performed in 26 patients. Bilateral hand and foot MEP amplitudes obtained with each protocol were compared. Subgroup comparisons were performed for myelopathy and peripheral neuropathy patients. Within-subject amplitude differences between c-MEP and each p-MEP technique were compared using a Wilcoxon test.

RESULTS

The mean age of the patients was 52.7 years (range, 12-79 years). Overall, p-MEPUL resulted in MEP improvement in 25 of 26 (96%) patients, and p-MEPLL improved MEPs in 19 of 26 (73%) patients. The increase in MEP amplitudes were statistically significant in all muscle groups except left foot. Similar improvements were seen in the myelopathy group; in the neuropathy group, p-MEPUL produced similar results, but p-MEPLL did not.

CONCLUSIONS

The p-MEP technique can improve MEP amplitudes, including in patients with myelopathy. In patients with peripheral neuropathy, the results were mixed.

SIGNIFICANCE

Tetanic stimulation can enhance intraoperative MEP amplitudes.

Intraoperative Neurophysiological Monitoring in Neurosurgery

Intraoperative neurophysiological monitoring (IONM) is a crucial advancement in neurosurgery, enhancing procedural safety and precision. This technique involves continuous real-time assessment of neurophysiological signals, aiding surgeons in timely interventions to protect neural structures. In addition to inherent limitations, IONM necessitates a detailed anesthetic plan for accurate signal recording. Given the growing importance of IONM in neurosurgery, we conducted a narrative review including the most relevant studies about the modalities and their application in different fields of neurosurgery. In particular, this review provides insights for all physicians and healthcare professionals unfamiliar with IONM, elucidating commonly used techniques in neurosurgery. In particular, it discusses the roles of IONM in various neurosurgical settings such as tumoral brain resection, neurovascular surgery, epilepsy surgery, spinal surgery, and peripheral nerve surgery. Furthermore, it offers an overview of the anesthesiologic strategies and limitations of techniques essential for the effective implementation of IONM.

Aborted AIS spinal fusion due to persistent loss of IONM: which patients are at greatest risk?

PURPOSE

Determine peri-operative risk factors predictive for prematurely stopping surgery prior to completion of deformity correction due to intra-operative neuromonitoring changes.

METHODS

A single institution retrospective review of adolescent idiopathic scoliosis (AIS) patients that underwent spinal fusion for curves greater than 70°. Cases aborted due to persistent loss of IONM were compared to completed cases. Demographic, radiographic, neurologic, and surgical information was reviewed.

RESULTS

There were 453 total cases. Nine (9/453: (2%)) cases were aborted due to persistent loss of IONM, and 4 (4/453; (0.88%)) awoke with a neurologic deficit. Comparing to the 444 completed cases, pre-operative risk factors associated with case abortion were older age (15.3 vs. 13.8 years; p = 0.02), sex (male) (66.7% vs. 20.3%, p = 0.004), and larger cobb angles (87.6° vs. 79.2°; p = 0.01). Being male increased the risk of case abortion: 7.9X. Intraoperative risk factors associated with case abortion were combined anterior/posterior approach (ASF/PSF) (44.4% vs. 7.2%; p = 0.003) and increased index procedure EBL (1127 vs. 769 mL; p = 0.043). ASF/PSF increased the risk: 10.3X. Four (4/9;44%) of the aborted cases awoke with neurologic deficit. Motor strength returned at 2.3 days (0-18). Aborted cases returned to the OR after 12.6 ± 7.0 days (1-23) which was related to time to regain motor strength.

CONCLUSION

Pre-operative risk factors for AIS case abortion due to persistent loss of IOMN are older age, males, with larger Cobb angles. Intraoperative risk factors are combined ASF/PSF and increased index procedure EBL. Independent risk factors were sex (male) and ASF/PSF which increased the risk 7.9X and 10.3X, respectively.

Prospective Validation of the Spinal Cord Shape Classification System in the Prediction of Intraoperative Neuromonitoring Data Loss: Assessing the Risk of Spinal Cord Data Loss During Spinal Deformity Correction

BACKGROUND

The Spinal Cord Shape Classification System (SCSCS) class has been associated with spinal cord monitoring data loss during spinal deformity surgery. The objective of the current study was to prospectively validate the SCSCS as a predictor of spinal cord monitoring data loss during spinal deformity surgery.

METHODS

A prospective cohort study of consecutive patients who were undergoing primary deformity surgery at a single institution from 2018 to 2023 and whose major curve was in the spinal cord region was undertaken. Spinal cord morphology at the apex of the major curve on preoperative axial T2-weighted magnetic resonance imaging was used to categorize patients into 3 spinal cord shape types based on the SCSCS. The primary outcome was intraoperative neuromonitoring (IONM) data loss related to spinal cord dysfunction. Demographics and surgical and radiographic variables were compared between patients with IONM data loss and those without loss. Predictors of IONM loss were determined using bivariate and multivariable logistic regression analyses.

RESULTS

A total of 256 patients (168 adult, 88 pediatric) were included and were separated into 3 SCSCS types: 110 (43.0%) with Type I, 105 (41.0%) with Type II, and 41 (16.0%) with Type III. IONM loss was observed in 30 (11.7%) of the 256 patients, including 7 (6.4%) of 110 with SCSCS Type I, 7 (6.7%) of 105 with Type II, and 16 (39.0%) of 41 with Type III. IONM loss was associated with SCSCS Type III, the preoperative deformity angular ratio, performance of 3-column osteotomies, greater operative time, greater transfusion volume, and greater postoperative sagittal corrections. SCSCS type was the strongest independent predictor of IONM data loss. SCSCS Type III had the greatest odds of IONM loss (odds ratio [OR] = 6.68, 95% confidence interval [CI] = 2.45 to 18.23 compared with Types I and II combined). The overall predictive performance with respect to IONM loss (area under the receiver operating characteristic curve = 0.827) was considered excellent.

CONCLUSIONS

This prospective cohort study of patients undergoing spinal deformity correction confirmed that patients with a Type-III spinal cord shape had greater odds of IONM loss. Inclusion of the SCSCS in preoperative risk stratification and intraoperative management of spinal deformity corrective surgery is recommended.

LEVEL OF EVIDENCE

Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

"Real-Time Neuromonitoring" Increases the Safety and Non-Invasiveness and Shortens the Duration of Idiopathic Scoliosis Surgery

Introduction: A practical solution to the incidental unreliability of intraoperative neuromonitoring (IONM) may be the simultaneous neurophysiological recording and control of the surgical field through a camera (the concept of "Real-time" IONM). During "Real-time" IONM, the surgeon is immediately warned about the possibility of damage to the neural structures during, but not after, standard idiopathic scoliosis (IS) corrective surgery procedures (the concept of "Surgeon-neurophysiologist" interactive, verbal IONM). This study aimed to compare the advantages, utilities, reliabilities, and time consumption of the two IONM scenarios. Methods: Studies were performed in two similar groups of patients undergoing surgery primarily due to Lenke 2 idiopathic scoliosis (N = 120), when both IONM approaches were applied. Neurophysiological evaluations of the spinal transmission were performed pre- (T0), intra- (before (T1) and after (T2) surgery), and postoperatively (T3), as well as once in healthy volunteers (control, N = 60). Non-invasive and innovative recordings of the motor evoked potentials (MEPs) bilaterally from the peroneal (PER) nerve and tibialis anterior (TA) muscle were performed with surface electrodes as a result of transcranial magnetic stimulation (TMS) or electrical stimulation (TES) at T0-T3. Results: In both groups, the MEP amplitudes and latencies recorded from the PER nerve were approximately 67% lower and 3.1 ms shorter than those recorded from the TA muscle. The MEP recording parameters differed similarly at T0-T3 compared to the control group. In all patients, the MEP parameters induced by TMS (T0) and TES (T1) did not differ. The MEP amplitude parameters recorded from the TA and PER at T1 and T2 indicated a bilateral improvement in the neural spinal conduction due to the surgical intervention. The TMS-induced MEP amplitude at T3 further increased bilaterally. In both IONM groups, an average 51.8 BIS level of anesthesia did not affect the variability in the MEP amplitude, especially in the PER recordings when the applied TES strength was 98.2 mA. The number of fluctuations in the MEP parameters was closely related to the number of warnings from the neurophysiologist during the transpedicular screw implantation, corrective rod implantation, and distraction, derotation, and compression procedures, and it was higher in the "Surgeon-neurophysiologist" IONM group. The average duration of surgery was shorter by approximately one hour in the "Real-time" IONM group. The number of two-way communications between the surgeon and the neurophysiologist and vice versa in the "Real-time" IONM group decreased by approximately half. Conclusions: This study proves the superiority of using "Real-time" IONM over the standard "Surgeon-neurophysiologist" IONM procedure in increasing the safety and non-invasiveness, shortening the time, and lowering the costs of the surgical treatment of IS patients. The modifications of the MEP nerve-conduction-recording technology with surface electrodes from nerves enable precise and reliable information on the pediatric patient's neurological condition at every stage of the applied surgical procedures, even under conditions of slight fluctuations in anesthesia.

The Management of Intraoperative Spinal Cord Injury - A Scoping Review

STUDY DESIGN

Scoping Review.

OBJECTIVE

To review the literature and summarize information on checklists and algorithms for responding to intraoperative neuromonitoring (IONM) alerts and management of intraoperative spinal cord injuries (ISCIs).

METHODS

MEDLINE® was searched from inception through January 26, 2022 as were sources of grey literature. We attempted to obtain guidelines and/or consensus statements from the following sources: American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM), American Academy of Neurology (AAN), American Clinical Neurophysiology Society, NASS (North American Spine Society), and other spine surgery organizations.

RESULTS

Of 16 studies reporting on management strategies for ISCIs, two were publications of consensus meetings which were conducted according to the Delphi method and eight were retrospective cohort studies. The remaining six studies were narrative reviews that proposed intraoperative checklists and management strategies for IONM alerts. Of note, 56% of included studies focused only on patients undergoing spinal deformity surgery. Intraoperative considerations and measures taken in the event of an ISCI are divided and reported in three categories of i) Anesthesiologic, ii) Neurophysiological/Technical, and iii) Surgical management strategies.

CONCLUSION

There is a paucity of literature on comparative effectiveness and harms of management strategies in response to an IONM alert and possible ISCI. There is a pressing need to develop a standardized checklist and care pathway to avoid and minimize the risk of postoperative neurologic sequelae.

Definition, Frequency and Risk Factors for Intra-Operative Spinal Cord Injury: A Knowledge Synthesis

STUDY DESIGN

Mixed-methods approach.

OBJECTIVES

Intra-operative spinal cord injury (ISCI) is a devastating complication of spinal surgery. Presently, a uniform definition for ISCI does not exist. Consequently, the reported frequency of ISCI and important risk factors vary in the existing literature. To address these gaps in knowledge, a mixed-methods knowledge synthesis was undertaken.

METHODS

A scoping review was conducted to review the definitions used for ISCI and to ascertain the frequency of ISCI. The definition of ISCI underwent formal review, revision and voting by the Guidelines Development Group (GDG). A systematic review of the literature was conducted to determine the risk factors for ISCI. Based on this systematic review and GDG input, a table was created to summarize the factors deemed to increase the risk for ISCI. All reviews were done according to PRISMA standards and were registered on PROSPERO.

RESULTS

The frequency of ISCI ranged from 0 to 61%. Older age, male sex, cardiovascular disease including hypertension, severe myelopathy, blood loss, requirement for osteotomy, coronal deformity angular ratio, and curve magnitude were associated with an increased risk of ISCI. Better pre-operative neurological status and use of intra-operative neuromonitoring (IONM) were associated with a decreased risk of ISCI. The risk factors for ISCI included a rigid thoracic curve with high deformity angular ratio, revision congenital deformity with significant cord compression and myelopathy, extrinsic intradural or extradural lesions with cord compression and myelopathy, intramedullary spinal cord tumor, unstable spine fractures (bilateral facet dislocation and disc herniation), extension distraction injury with ankylosing spondylitis, ossification of posterior longitudinal ligament (OPLL) with severe cord compression, and moderate to severe myelopathy.

CONCLUSIONS

ISCI has been defined as "a new or worsening neurological deficit attributable to spinal cord dysfunction during spine surgery that is diagnosed intra-operatively via neurophysiologic monitoring or by an intraoperative wake-up test, or immediately post-operatively based on clinical assessment". This paper defines clinical and imaging factors which increase the risk for ISCI and that could assist clinicians in decision making.

A Clinical Practice Guideline on the Timing of Surgical Decompression and Hemodynamic Management of Acute Spinal Cord Injury and the Prevention, Diagnosis, and Management of Intraoperative Spinal Cord Injury: Introduction, Rationale, and Scope

STUDY DESIGN

Protocol for the development of clinical practice guidelines following the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) standards.

OBJECTIVES

Acute SCI or intraoperative SCI (ISCI) can have devastating physical and psychological consequences for patients and their families. The treatment of SCI has dramatically evolved over the last century as a result of preclinical and clinical research that has addressed important knowledge gaps, including injury mechanisms, disease pathophysiology, medical management, and the role of surgery. In an acute setting, clinicians are faced with critical decisions on how to optimize neurological recovery in patients with SCI that include the role and timing of surgical decompression and the best strategies for hemodynamic management. The lack of consensus surrounding these treatments has prevented standardization of care across centers and has created uncertainty with respect to how to best manage patients with SCI. ISCI is a feared complication that can occur in the best of hands. Unfortunately, there are no systematic reviews or clinical practice guidelines to assist spine surgeons in the assessment and management of ISCI in adult patients undergoing spinal surgery. Given these limitations, it is the objective of this initiative to develop evidence-based recommendations that will inform the management of both SCI and ISCI. This protocol describes the rationale for developing clinical practice guidelines on (i) the timing of surgical decompression in acute SCI; (ii) the hemodynamic management of acute SCI; and (iii) the prevention, identification, and management of ISCI in patients undergoing surgery for spine-related pathology.

METHODS

Systematic reviews were conducted according to PRISMA standards in order to summarize the current body of evidence and inform the guideline development process. The guideline development process followed the approach proposed by the GRADE working group. Separate multidisciplinary, international groups were created to perform the systematic reviews and formulate the guidelines. All potential conflicts of interest were vetted in advance. The sponsors exerted no influence over the editorial process or the development of the guidelines.

RESULTS

This process resulted in both systematic reviews and clinical practice guidelines/care pathways related to the role and timing of surgery in acute SCI; the optimal hemodynamic management of acute SCI; and the prevention, diagnosis and management of ISCI.

CONCLUSIONS

The ultimate goal of this clinical practice guideline initiative was to develop evidence-based recommendations for important areas of controversy in SCI and ISCI in hopes of improving neurological outcomes, reducing morbidity, and standardizing care across settings. Throughout this process, critical knowledge gaps and future directions were also defined.

Prevention, Diagnosis, and Management of Intraoperative Spinal Cord Injury in the Setting of Spine Surgery: A Proposed Care Pathway

STUDY DESIGN

This study is a mixed methods approach.

OBJECTIVES

Intraoperative spinal cord injury (ISCI) is a challenging complication in spine surgery. Intra-operative neuromonitoring (IONM) has been developed to detect changes in neural function. We report on the first multidisciplinary, international effort through AO Spine and the Praxis Spinal Cord Institute to develop a comprehensive guideline and care pathway for the prevention, diagnosis, and management of ISCI.

METHODS

Three literature reviews were registered on PROSPERO (CRD 42022298841) and performed according to PRISMA guidelines: (1) Definitions, frequency, and risk factors for ISCI, (2) Meta-analysis of the accuracy of IONM for diagnosis of ISCI, (3) Reported management approaches for ISCI and related events. The results were presented in a consensus session to decide the definition of IONM and recommendation of its use in high-risk cases. Based on a literature review of management strategies for ISCI, an intra-operative checklist and overall care pathway was developed by the study team.

RESULTS

An operational definition and high-risk patient categories for ISCI were established. The reported incidence of deficits was documented to be higher in intramedullary tumour spine surgery. Multimodality IONM has a high sensitivity and specificity. A guideline recommendation of IONM to be employed for high-risk spine cases was made. The different sections of the intraoperative checklist include surgery, anaesthetic and neurophysiology. The care pathway includes steps (1) initial clinical assessment, (2) pre-operative planning, (3) surgical/anaesthetic planning, (4) intra-operative management, and (5) post-operative management.

CONCLUSIONS

This is the first evidence based comprehensive guideline and care pathway for ISCI using the GRADE methodology. This will facilitate a reduction in the incidence of ISCI and improved outcomes from this complication. We welcome the wide implementation and validation of these guidelines and care pathways in prospective, multicentre studies.

Accuracy of Intraoperative Neuromonitoring in the Diagnosis of Intraoperative Neurological Decline in the Setting of Spinal Surgery-A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

In an effort to prevent intraoperative neurological injury during spine surgery, the use of intraoperative neurophysiological monitoring (IONM) has increased significantly in recent years. Using IONM, spinal cord function can be evaluated intraoperatively by recording signals from specific nerve roots, motor tracts, and sensory tracts. We performed a systematic review and meta-analysis of diagnostic test accuracy (DTA) studies to evaluate the efficacy of IONM among patients undergoing spine surgery for any indication.

METHODS

The current systematic review and meta-analysis was performed using the Preferred Reporting Items for a Systematic Review and Meta-analysis statement for Diagnostic Test Accuracy Studies (PRISMA-DTA) and was registered on PROSPERO. A comprehensive search was performed using MEDLINE, EMBASE and SCOPUS for all studies assessing the diagnostic accuracy of neuromonitoring, including somatosensory evoked potential (SSEP), motor evoked potential (MEP) and electromyography (EMG), either on their own or in combination (multimodal). Studies were included if they reported raw numbers for True Positives (TP), False Negatives (FN), False Positives (FP) and True Negative (TN) either in a 2 × 2 contingency table or in text, and if they used postoperative neurologic exam as a reference standard. Pooled sensitivity and specificity were calculated to evaluate the overall efficacy of each modality type using a bivariate model adapted by Reitsma et al, for all spine surgeries and for individual disease groups and regions of spine. The risk of bias (ROB) of included studies was assessed using the quality assessment tool for diagnostic accuracy studies (QUADAS-2).

RESULTS

A total of 163 studies were included; 52 of these studies with 16,310 patients reported data for SSEP, 68 studies with 71,144 patients reported data for MEP, 16 studies with 7888 patients reported data for EMG and 69 studies with 17,968 patients reported data for multimodal monitoring. The overall sensitivity, specificity, DOR and AUC for SSEP were 71.4% (95% CI 54.8-83.7), 97.1% (95% CI 95.3-98.3), 41.9 (95% CI 24.1-73.1) and .899, respectively; for MEP, these were 90.2% (95% CI 86.2-93.1), 96% (95% CI 94.3-97.2), 103.25 (95% CI 69.98-152.34) and .927; for EMG, these were 48.3% (95% CI 31.4-65.6), 92.9% (95% CI 84.4-96.9), 11.2 (95% CI 4.84-25.97) and .773; for multimodal, these were found to be 83.5% (95% CI 81-85.7), 93.8% (95% CI 90.6-95.9), 60 (95% CI 35.6-101.3) and .895, respectively. Using the QUADAS-2 ROB analysis, of the 52 studies reporting on SSEP, 13 (25%) were high-risk, 10 (19.2%) had some concerns and 29 (55.8%) were low-risk; for MEP, 8 (11.7%) were high-risk, 21 had some concerns and 39 (57.3%) were low-risk; for EMG, 4 (25%) were high-risk, 3 (18.75%) had some concerns and 9 (56.25%) were low-risk; for multimodal, 14 (20.3%) were high-risk, 13 (18.8%) had some concerns and 42 (60.7%) were low-risk.

CONCLUSIONS

These results indicate that all neuromonitoring modalities have diagnostic utility in successfully detecting impending or incident intraoperative neurologic injuries among patients undergoing spine surgery for any condition, although it is clear that the accuracy of each modality differs.PROSPERO Registration Number: CRD42023384158.

Intraoperative Monitoring of Scoliosis Surgery in Young Patients

SUMMARY

Intraoperative neurophysiologic monitoring has added substantially to the safety of spinal deformity surgery correction since its introduction over four decades ago. Monitoring routinely includes both somatosensory evoked potentials and motor evoked potentials. Either modality alone will detect almost all instances of spinal cord injury during deformity correction. The combined use of the two modalities provides complementary information, can permit more rapidly identification of problems, and enhances safety though parallel redundancy should one modality fail. Both techniques are well established and continue to be refined. Although there is room for provider preference, proper monitoring requires attention to technical detail, understanding of the underlying physiology, and familiarity with effects of commonly used anesthetic agents.

Analysis of Intraoperative Motor Evoked Potential Changes and Surgical Interventions in 513 Pediatric Spine Surgeries

PURPOSE

(1) To determine probabilities of immediate postoperative new motor deficits after no, reversible, and irreversible motor evoked potentials (MEP) deteriorations and (2) to calculate the same outcome considering whether MEP deteriorations were followed by surgical interventions in the absence of confounding factors.

METHODS

We analyzed MEPs from 513 surgeries. Four-limb MEPs were evoked by transcranial electrical stimulation. Baseline recordings were obtained before skin incision and updated before instrumentation. Motor evoked potentials deteriorations were considered significant whenever they showed a persistent, reversible, or irreversible amplitude decrease of >80% of the baseline values.

RESULTS

Nine patients showed postoperative new motor deficits. Probabilities of postoperative new motor deficits were null, 2.8%, and 36.8% with no, reversible, and irreversible MEP deteriorations, respectively. The risk of immediate postoperative new motor deficits was significantly lower ( P = 0.0002) in reversible MEP compared with irreversible MEP deteriorations. In patients showing reversible/irreversible MEP deteriorations in the absence of confounding factors, surgical interventions compared with nonsurgical interventions significantly decreased the risk of immediate postoperative new motor deficits ( P = 0.0216).

CONCLUSIONS

This study shows that probabilities of immediate postoperative new motor deficits increase with the severity of intraoperative MEP changes. In addition, our results support the value of surgical interventions triggered by MEP deteriorations to reduce postoperative adverse motor outcomes.

Neuromonitoring Changes in Spinal Deformity Surgery

Spinal cord injury is one of the most feared complications in spinal deformity surgery. The surgeon must be vigilant of direct and indirect sources of injury at all points during surgery. The incidence of complications has greatly decreased with the ability to monitor the motor and sensory pathways. Changes in signaling of these pathways provide context for what the insult is, and how to correct it before it becomes irreversible. There are well-established protocols that provide an algorithmic response to changes that can help all in the room determine the source of injury, and the appropriate reaction.

Paediatric Spinal Deformity Surgery: Complications and Their Management

Surgical correction of paediatric spinal deformity is associated with risks, adverse events, and complications that must be preoperatively discussed with patients and their families to inform treatment decisions, expectations, and long-term outcomes. The incidence of complications varies in relation to the underlying aetiology of spinal deformity and surgical procedure. Intraoperative complications include bleeding, neurological injury, and those related to positioning. Postoperative complications include persistent pain, surgical site infection, venous thromboembolism, pulmonary complications, superior mesenteric artery syndrome, and also pseudarthrosis and implant failure, proximal junctional kyphosis, crankshaft phenomenon, and adding-on deformity, which may necessitate revision surgery. Interventions included in enhanced recovery after surgery protocols may reduce the incidence of complications. Complications must be diagnosed, investigated and managed expeditiously to prevent further deterioration and to ensure optimal outcomes. This review summarises the complications associated with paediatric spinal deformity surgery and their management.

Current Trends in Intraoperative Spinal Cord Monitoring: A Survey Analysis among Japanese Expert Spine Surgeons

Introduction

Although intraoperative spinal neuromonitoring (IONM) is recommended for spine surgeries, there are no guidelines regarding its use in Japan, and its usage is mainly based on the surgeon's preferences. Therefore, this study aimed to provide an overview of the current trends in IONM usage in Japan.

Methods

In this web-based survey, expert spine surgeons belonging to the Japanese Society for Spine Surgery and Related Research were asked to respond to a questionnaire regarding IONM management. The questionnaire covered various aspects of IONM usage, including the preferred modality, operation of IONM, details regarding muscle-evoked potential after electrical stimulation of the brain (Br(E)-MsEP), and need for consistent use of IONM in major spine surgeries.

Results

Responses were received from 134 of 186 expert spine surgeons (response rate, 72%). Of these, 124 respondents used IONM routinely. Medical staff rarely performed IONM without a medical doctor. Br(E)-MsEP was predominantly used for IONM. One-third of the respondents reported complications, such as bite injuries caused by Br(E)-MsEP. Interestingly, two-thirds of the respondents did not plan responses to alarm points. Intramedullary spinal cord tumor, scoliosis (idiopathic, congenital, or neuromuscular in pediatric), and thoracic ossification of the posterior longitudinal ligament were representative diseases that require IONM.

Conclusions

IONM has become an essential tool in Japan, and Br(E)-MsEP is a predominant modality for IONM at present. Although we investigated spine surgeries for which consistent use of IONM is supported, a cost-benefit analysis may be required.

Comprehensive Perioperative Approach to Complex Spine Deformity Management

OBJECTIVE

Study perioperative strategies for optimizing neuroprotection in complex spine deformity correction surgery.

METHODS

We report the case of a patient with severe lumbar dextroscoliosis, thoracolumbar junction hyperkyphosis with a 40-degree Cobb angle levoconvex scoliosis who underwent spinal deformity correction with loss of neuromonitoring during surgery. We performed a literature review on perioperative management of complex spine deformity.

RESULTS

A 50-year-old man presented with lumbar pain and right L4 radiculopathy. Surgical intervention for deformity correction and decompression was indicated with T4-L4 posterior instrumentation L2/L3 and L3/L4 transforaminal lumbar interbody fusion. Surgery was aborted due to the loss of neuromonitoring. Postsurgery, the patient had left sensory deficit and the neurocritical care team clinically suspected and deduced the anatomic location of the spinal cord compression. Magnetic resonance imaging confirmed a T10-T11 hyperintensity suggestive of cord ischemia due to osteophyte compressing the spinal cord. The patient underwent a second corrective surgery with no intraoperative events and has no long-term neurological sequela.

CONCLUSIONS

This case illustrates that a comprehensive perioperative approach and individualized risk factor assessment is useful in complex spine deformity surgery. Further research is needed to determine how this individualized comprehensive approach can lead to intraoperative and postoperative countermeasures that improved spine surgery outcomes.

LEVEL OF EVIDENCE

Level V.

Establishing consensus: determinants of high-risk and preventative strategies for neurological events in complex spinal deformity surgery

PURPOSE

To establish expert consensus on various parameters that constitute elevated risk during spinal deformity surgery and potential preventative strategies that may minimize the risk of intraoperative neuromonitoring (IONM) events and postoperative neurological deficits.

METHODS

Through a series of surveys and a final virtual consensus meeting, the Delphi method was utilized to establish consensus among a group of expert spinal deformity surgeons. During iterative rounds of voting, participants were asked to express their agreement (strongly agree, agree, disagree, strongly disagree) to include items in a final set of guidelines. Consensus was defined as ≥ 80% agreement among participants. Near-consensus was ≥ 60% but < 80% agreement, equipoise was ≥ 20% but < 60%, and consensus to exclude was < 20%.

RESULTS

Fifteen of the 15 (100%) invited expert spinal deformity surgeons agreed to participate. There was consensus to include 22 determinants of high-risk (8 patient factors, 8 curve and spinal cord factors, and 6 surgical factors) and 21 preventative strategies (4 preoperative, 14 intraoperative, and 3 postoperative) in the final set of best practice guidelines.

CONCLUSION

A resource highlighting several salient clinical factors found in high-risk spinal deformity patients as well as strategies to prevent neurological events was successfully created through expert consensus. This is intended to serve as a reference for surgeons and other clinicians involved in the care of spinal deformity patients.

LEVEL OF EVIDENCE

Level V.

Monitoring scoliosis and other spinal deformity surgeries

Surgery to correct a spinal deformity incurs a risk of injury to the spinal cord and roots. Injuries include postoperative paraplegia. Surgery for cervical myelopathy also incurs risk for postoperative motor deficits, as well as nerve injury most commonly at the C5 root. Risks can be mitigated by monitoring the nervous system during surgery. Ideally, monitoring detects an impending injury in time to intervene and correct the impairment before it becomes permanent. Monitoring includes several modalities of testing. Somatosensory evoked potentials measure axonal conduction in the spinal cord posterior columns. This can be checked almost continuously during surgery. Motor evoked potentials measure conduction along the lateral corticospinal tracts. Because motor pathway stimulation often produces a patient movement on the table, these often are tested periodically rather than continuously. Electromyography observes for spontaneous discharges accompanying injuries, and is useful to assess misplacement of pedicle screws. Literature demonstrates the usefulness of these techniques, their association with reducing motor adverse outcomes, and the relative value of the techniques. Neurophysiologic monitoring for scoliosis, kyphosis, and cervical myelopathy surgery are addressed, along with background information about those conditions.

Comparison of Intraoperative Neuromonitoring Outcome in Treating Thoracic Ossification of the Ligamentum Flavum Through En Bloc Versus Piecemeal Laminectomy

STUDY DESIGN

A retrospective cohort analysis.

OBJECTIVE

The aim of this study was to investigate the impact of piecemeal versus en bloc laminectomies on spinal cord in thoracic ossification of ligamentum flavum (TOLF) through intraoperative changes of motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SEPs).

SUMMARY OF BACKGROUND DATA

Surgical treatment is indicated for symptomatic TOLF, and both piecemeal and en bloc laminectomies are commonly used methods. However, few studies compared both intraoperative interference and prognostic impact of these two laminectomies on spinal cord in TOLF patients.

METHODS

MEPs were recorded from abductor hallucis (AH) and tibialis anterior, and SEPs were performed on tibial nerve in 55 TOLF patients (piecemeal vs. en bloc: 23 vs. 32). Patients were categorized based on MEP/SEP improvement, deterioration, and no change, and MEP/SEP improvement rates were measured in the improvement group. Additionally, all patients were assessed by American Spinal Injury Association (ASIA) scores, Ashworth scores, and modified Japanese Orthopedic association (mJOA) scores before and after operation.

RESULTS

The incidences of both MEP/SEP improvement and deterioration were similar between the two laminectomy groups (P > 0.05), and no significant difference is noted in both MEP and SEP amplitudes between the baseline and different critical manipulations in both laminectomy groups (P > 0.05). In the improvement group, patients receiving en bloc laminectomy exhibited increased improvement rates of both MEPs in bilateral AH and left-side SEPs compared to piecemeal laminectomy (P < 0.05). Clinically, all functional scales clearly improved in both laminectomy groups after operation (P < 0.05), and postoperative 1-year mJOA improvement rates were highly correlated with MEP improvement rates (P < 0.05).

CONCLUSION

Intraoperative changes of MEPs and SEPs potentially provide a valid method for quantitatively evaluating the safety of different intraoperative manipulations and their prognostic impacts on spinal cord. Both laminectomies are safe and effective methods to treat TOLF, and en bloc laminectomy may cause relatively better spinal cord functional recovery.Level of Evidence: 3.

Understanding the effect of non-surgical factors in a transcranial motor-evoked potential alert: A retrospective cohort study

BACKGROUND

Intraoperative neuromonitoring (IONM) is important for detecting neurological dysfunction, allowing for intervention and reversal of neurological deficits before they become permanent. Of the several IONM modalities, transcranial electrical stimulation of motor-evoked potential (TES-MEP) can help monitor the activity in the pyramidal tract. Surgery- and non-surgery-related factors could result in a TES-MEP alert during surgery. Once the alert occurs, the surgeon should immediately intervene to prevent a neurological complication. However, TES-MEP monitoring does not provide sufficient data to identify the non-surgery-related factors. Therefore, this study aimed to identify and describe these factors among TES-MEP alert cases.

METHODS

In this multicenter study, data from 1934 patients who underwent various spinal surgeries for spinal deformities, spinal cord tumors, and ossification of the posterior longitudinal ligament of the spine from 2017 to 2019 were collected. A 70% amplitude reduction was set as the TES-MEP alarm threshold. All surgeries with alerts were categorized into true-positive (TP) and false-positive (FP) cases according to the assessment of immediate postoperative neurological deficits.

RESULTS

In total, TES-MEP alerts were observed in 251 cases during surgery: 62 TP and 189 FP IONM cases. Overall, 158 cases were related to non-surgery-related factors. We observed 22 (35.5%) TP cases and 136 (72%) FP cases, which indicated cases associated with non-surgery-related factors. A significant difference was observed between the two groups regarding factors associated with TES-MEP alerts (p < 0.01). The ratio of TP and FP cases (related to non-surgery-related factors) associated with TES-MEP alerts was 13.9% (22/158 cases) and 86.1% (136/158 cases), respectively.

CONCLUSIONS

Non-surgery-related factors are proportionally higher in FP than in TP cases. Although the surgeon should examine surgical procedures immediately after a TES-MEP alert, surgical intervention may not always be the best approach according to the results of this study.

Enhanced Safety of Pedicle Subtraction Osteotomy Using Intraoperative Ultrasound

BACKGROUND

Pedicle subtraction osteotomy (PSO) can improve sagittal alignment but carries risks, including iatrogenic spinal cord and nerve root injury. Critically, during the reduction phase of the technique, medullary kinking or neural element compression can lead to neurologic deficits.

METHODS

We describe 3 cases of thoracic PSO and evaluate the feasibility, findings, and utility of intraoperative ultrasound in this setting.

RESULTS

Intraoperative ultrasound can provide a visual assessment of spinal cord morphology before and after PSO reduction and influences surgical decision making with regard to the final amount of sagittal plane correction. This modality is particularly useful for confirming ventral decompression of disc-osteophyte complex before reduction and also after reduction maneuvers when there is kinking of the thecal sac but uncertainty about the underlying status of the spinal cord. Intraoperative ultrasound is a reliable modality that fits well into the technical sequence of PSO, adds a minimal amount of operative time, and has few limitations.

CONCLUSIONS

We propose that intraoperative ultrasound is a useful supplement to standard neuromonitoring modalities for ensuring safe PSO reduction and decompression of neural elements.

Severe hypotension with loss of motor evoked potentials during cervical surgery prompting immediate cardiovascular resuscitation

Background:

Intraoperative neuromonitoring (IONM) is a well-established adjunct to spinal surgery to ensure safety of the neural elements.IONM has extremely high sensitivity and specificity for impending neurologic damage. In very rare instances, hypoperfusion of the cord may lead to a loss of IONM modalities that may be reversed if blood pressure issues responsible for the drop out of potentials are immediately addressed.

Case Description:

The authors describe a case in which IONM documented hypoperfusion of the cord intraoperatively due to hypotension. Recognition of this problem and reversal of the hypotension resulted in normalization of postoperative function.

Conclusion:

The use of IONM allowed for quick recognition of an impending neurological insult during spinal deformity surgery. Prompt response to signaling changes allowed for the correction of hypotension and favorable neurologic outcome.

Sudden, Transient Intraoperative Hypotension During the Use of the Cantilever Technique for Correction of Adult Spine Deformity

Intraoperative hypotension is a common but critical complication of spinal surgery. However, it is uncommon to experience sudden transient intraoperative hypotension in patients undergoing surgery for adult spine deformity (ASD) without the presence of major vascular injury, spinal cord injury, or cardiac events. We report a patient who experienced sudden transient intraoperative hypotension during the use of the cantilever technique for correction of an ASD. A 58-year-old woman underwent two-stage surgery (anterior correction followed by posterior fusion) for an ASD that caused low back pain. During the posterior fusion procedure, she experienced sudden transient intraoperative hypotension during the use of a cantilever technique. As soon as we paused the use of this technique, her hypotension resolved. Postoperative radiography revealed excessive segmental lordosis at the L4/5 level, suggesting an accidental rupture of the anterior longitudinal ligament (ALL). We believe that the mechanism of our patient’s sudden hypotension was a decrease in venous return due to compression and stretching of the inferior vena cava at the time of rod application when the use of the cantilever technique caused ALL rupture. Sudden hypotension during posterior spinal correction surgery is possible, especially in patients with a ruptured ALL.

Surgeon-directed transcranial motor evoked potential spinal cord monitoring in spinal deformity surgery

AIMS

Spinal deformity surgery carries the risk of neurological injury. Neurophysiological monitoring allows early identification of intraoperative cord injury which enables early intervention resulting in a better prognosis. Although multimodal monitoring is the ideal, resource constraints make surgeon-directed intraoperative transcranial motor evoked potential (TcMEP) monitoring a useful compromise. Our experience using surgeon-directed TcMEP is presented in terms of viability, safety, and efficacy.

METHODS

We carried out a retrospective review of a single surgeon's prospectively maintained database of cases in which TcMEP monitoring had been used between 2010 and 2017. The upper limbs were used as the control. A true alert was recorded when there was a 50% or more loss of amplitude from the lower limbs with maintained upper limb signals. Patients with true alerts were identified and their case history analyzed.

RESULTS

Of the 299 cases reviewed, 279 (93.3%) had acceptable traces throughout and awoke with normal clinical neurological function. No patient with normal traces had a postoperative clinical neurological deficit. True alerts occurred in 20 cases (6.7%). The diagnoses of the alert group included nine cases of adolescent idiopathic scoliosis (AIS) (45%) and six of congenital scoliosis (30%). The incidence of deterioration based on diagnosis was 9/153 (6%) for AIS, 6/30 (20%) for congenital scoliosis, and 2/16 (12.5%) for spinal tuberculosis. Deterioration was much more common in congenital scoliosis than in AIS (p = 0.020). Overall, 65% of alerts occurred during rod instrumentation: 15% occurred during decompression of the internal apex in vertebral column resection surgery. Four alert cases (20%) awoke with clinically detectable neurological compromise.

CONCLUSION

Surgeon-directed TcMEP monitoring has a 100% negative predictive value and allows early identification of physiological cord distress, thereby enabling immediate intervention. In resource constrained environments, surgeon-directed TcMEP is a viable and effective method of intraoperative spinal cord monitoring. Level of evidence: III Cite this article: Bone Joint J 2021;103-B(3):547-552.

Is the axial spinal cord classification predictive of intraoperative neurologic alert for pediatric scoliosis patients? An independent retrospective validation study

PURPOSE

We sought to determine whether the axial spinal cord classification by Sielatycki et al. would be associated with increased intraoperative neuromonitoring (IONM) alerts for pediatric scoliosis patients undergoing posterior spinal fusion (PSF) surgery.

METHODS

Children less than age 19 with scoliosis undergoing PSF were retrospectively reviewed. Axial-T2 MRI of the thoracic apex was reviewed for spinal cord/CSF architecture as described by Sielatycki et al.: Type 1-circular cord with visible CSF, Type 2-circular cord but no visible CSF at apical concavity, and Type 3-cord deformed with no intervening CSF. Intraoperative neuromonitoring reports, operative records and preoperative radiographs were reviewed.

RESULTS

90 patients met the inclusion criteria. Rate of neurologic events was Type 1: 2% (1/41 patients), Type 2: 14.3% (4/28), Type 3: 57.1% (12/21) (Type 1 vs 2 p = 0.06; Type 1 vs 3 p < 0.0001; Type 2 vs 3 p = 0.0017). Three patients with a Type 3 cord awoke with significant deficits. In comparison to Type 1 cords, Type 3 and Type 2 spinal cords were associated with increased coronal and total deformity angular ratios (Type 1 vs 3 p = 0.035 and 0.0054 respectively; Type 1 vs 2 p = 0.042 and 0.03 respectively). There was no difference in gender, diagnosis category, age at surgery, Cobb angle or kyphosis between the three groups.

CONCLUSION

The axial spinal cord classification correlated with IONM alerts and greater severity of spinal deformity in pediatric scoliosis patients.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

The Current Practice of Adult Idiopathic Scoliosis Surgical Treatment Among Spine Surgeons in Saudi Arabia

Background: Scoliosis is a spinal deformity consisting of lateral curvature and rotation of the vertebrae. The goal of corrective scoliosis surgery is to restore alignment of the spine and maintain motion. However, there is no global agreement among spine surgeons on the best method of surgical intervention, and little is known about the variations in practice among spine surgeons in Saudi Arabia.

Objectives: The aim of this study is to examine the current surgical practices relating to adolescent idiopathic scoliosis and to establish the degree of variation and consensus among spine surgeons in Saudi Arabia.

Methods: This was a cross-sectional study conducted among spine surgeons in Saudi Arabia, using a self-administered questionnaire. The questionnaire addressed four areas: surgeons’ demographics, pre-operative assessment, operative assessment, and infection control practices. There were a total of 27 questions. Data was analyzed using statistical package for social sciences (SPSS) software (SPSS Inc., Chicago, IL, USA).

Results: A total of 150 surgeons were included in this study. Of these, 73 responded to the questionnaire (response rate: 48.6%), 46 (63.01%) of whom were fellows. All respondents were males, and 37 (51.39%) were aged between 30 and 40 years. Fifty five (75.34%) were orthopedic surgeons. The most commonly used pre-operative health assessment test was an echocardiogram. Sixty six (90%) surgeons requested scoliosis anteroposterior (AP) view and lateral radiograph for curvature between 40 degrees and 90 degrees, and 65 (89%) requested it for curvature greater than 90 degrees. For the posterior construct, 29 (45.31%) did not use cross-links for fewer than 10 levels, and 23 (35.94%) did not use cross-links for more than 10 levels. In addition to a local bone graft, the most commonly used transplant method was allograft 37 (50.68%). Fifty five (85.94%) respondents favored an all-screw pedicle construct over a hybrid construct.

Conclusion: A large variation in surgical practices was observed. This was especially apparent in practices including the use of cross-links, intra-operative cell salvage, and the intra-operative use of traction. Some degree of variation was observed in pre-operative imaging assessment practices. Surgical guidelines should be developed to build a consensus among surgeons. A unified surgical training curriculum may help in achieving this goal.

Motor evoked potential recovery with surgeon interventions and neurologic outcomes: A meta-analysis and structural causal model for spine deformity surgeries

OBJECTIVE

To improve estimates of motor evoked potential (MEP) performance during spine deformity surgeries by accounting for potential confounders.

METHODS

A meta-analysis of MEPs for spine deformity surgeries determined the probability of a MEP deterioration which recovered by the end of surgery, P(RSC), and the conditional probability of no new post-operative deficit given an RSC, P(NND|RSC), stratified by category of intraoperative adverse event associated with the MEP deterioration. A structural causal model (SCM) and propensity score matching accounted for intraoperative adverse events and patient diagnosis as potential confounders.

RESULTS

MEPs changes (either reversible, RSC or irreversible, IRREV) were reported for 295 of 5055 cases (6%) in 21 studies. The probability of no new motor deficit, P(NND), plotted against the probability of a RSC, P(RSC), for studies in the meta-analysis was highly significant (r = 0.71, p < 0.001). P(RSC) was 0.76 for an alert associated with correction, less for osteotomies (0.48, p = 0.0008), and tended to be higher for hypotension (0.92, p = 0.06). P(NND|RSC) was 0.94 for correction, less for positioning (0.82), and osteotomies (0.86), and greater for hypotension (1.0). In the SCM, a RSC after an alert was a highly significant and independent predictor of no new motor deficits (odds 25.2, p < 0.001).

CONCLUSION

There are significant differences in P(RSC) for hypotension and osteotomies, and in P(NND) for osteotomies and instrumentation, compared to correction. P(RSC) is a significant and independent predictor of outcomes.

SIGNIFICANCE

When MEPs are used for spine deformity surgeries, accounting for adverse events associated with an alert and patient diagnosis as potential confounders is expected to improve RSC prediction of post-operative outcomes and estimates of RSC efficacy in improving outcomes.

Surgical treatment of adolescent idiopathic scoliosis: Complications

Despite the fact that spinal surgeries for adolescent idiopathic scoliosis (AIS) result in good outcomes for most patients, they are not without complications either medically or surgically. Neurologic injury represents the most severe complication and is, as such, the most feared. Further complications include dural tears, peripheral neuropathy, surgical-site infections, implant-related issues, thromboembolic events, visual loss, pseudarthrosis, Crankshaft phenomenon, flatback phenomenon, proximal junctional kyphosis, and mortality. It is vital that all spine surgeons to be fully conversant with the possible complications and the proper responses for each of them.

•

Surgeons should know how to manage complications of surgery for AIS.

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Patients should know about potential complications prior to surgery.

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Neurologic injury represents the most severe complication.

Risk, Recovery, and Clinical Impact of Neurological Complications in Adult Spinal Deformity Surgery

STUDY DESIGN

Multicenter retrospective case series.

OBJECTIVE

To report the risks, recovery, and clinical impact of neurological complications (NCs) in adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

Although recent studies have reported the incidence of NCs in ASD surgery, few have addressed the recovery from and clinical impacts of NC.

METHODS

We reviewed records from a multicenter database for 285 consecutive surgically treated ASD patients who had reached a 2-year follow-up. NCs were categorized as sensory only or motor deficit (MD). Recovery was noted as none, partial, or complete, during hospitalization and at every postoperation visit. Uni- and multivariate risk analyses were performed to identify risk factors for MD.

RESULTS

NC developed in 29 (10%) patients within 30 days of surgery, of which 11 were permanent deficits (seven no recovery, and four partial recovery). MD developed in 14 (5%) patients, including one spinal cord injury. Seven MD patients required physical assistance at the latest follow-up. While NC patients experienced significant improvements in health-related quality of life at the 2-year follow-up, the health-related quality of life was significantly worse for the NC versus no-NC group at this time point. Univariate analyses revealed that Schwab-SRS types N and L, pelvic tilt, modified frailty index physical function, and an inferior SRS22 function domain at baseline were risk factors for MD. Among them, modified frailty index physical function, which represented a preoperative decline in activities of daily living, was identified as an independent risk factor for MD (OR: 4.0, 95% CI: 1.2-13.5, P = 0.03).

CONCLUSIONS

NC developed in 10% of ASD surgery patients, with permanent deficits occurring in 4%. Half of the patients who developed MD required physical assistance, which contributed to the inferior clinical outcomes. Surgical intervention should be considered before severe activities of daily living decline to prevent NCs.

LEVEL OF EVIDENCE

4.

Ponte Osteotomies Increase the Risk of Neuromonitoring Alerts in Adolescent Idiopathic Scoliosis Correction Surgery

STUDY DESIGN

Observational cohort study of prospective database registry.

OBJECTIVE

To determine the incidence of neurological complications in AIS patients undergoing surgical treatment with PO.

SUMMARY OF BACKGROUND DATA

Despite the widespread use of Ponte Osteotomies (PO) in adolescent idiopathic scoliosis (AIS) correction, outcomes and complications in patients treated with this technique have not been well characterized.

METHODS

A multicenter prospective registry of patients undergoing surgical correction of AIS was queried at 2-year follow-up for patient demographics, surgical data, deformity characteristics, and peri-operative complications. A neurological complication was defined as perioperative nerve root or spinal cord injury as identified by the surgeon. Patients were divided into those who underwent peri-apical PO and those without, and further stratified by Lenke curve classification into 3 groups (I-types 1 and 2, II-types 3, 4, 6, and III-type 5). Patients with- and without neurological complications were compared with respect to baseline demographics, surgical variables, curve types, fusion construct types (screws vs. hybrid), curve magnitude (coronal and sagittal Cobb), apical vertebral translation, and coronal-deformity angular ratios (C-DAR).

RESULTS

Of 2210 patients included in the study, 1611 underwent PO. Peri-operative neurological complications occurred in 7 patients, with 6 in the PO group (0.37%) and 1 in non-PO group (0.17%) though this was not a statistically significant risk factor for peri-operative neurological injury (P = 0.45). Neuromonitoring alerts were recorded in 168 patients (7.6%: 9.3% PO group; 4.2% no-PO group (P < 0.001)). Multivariate logistic regression analysis found PO and curve magnitude to be independent risk factors for intraoperative neuromonitoring alerts (P < 0.01).

CONCLUSION

PO and curve magnitude were independent risk factors for intraoperative neuromonitoring alerts in surgical AIS correction. The effect of Ponte osteotomy on neurological complications remains unknown due to the low incidence of these complications.

LEVEL OF EVIDENCE

3.

Traumatic spinal cord injuries: A retrospective cohort study of children seen in Western Australia between 1996 and 2016

PURPOSE

To describe the medical complexity of traumatic spinal cord injury (TSCI) in paediatric patients in Western Australia (WA). Secondly, to determine if Princess Margaret Hospital (PMH) for Children (the tertiary paediatric centre in WA where all TSCI patients are managed) is meeting the requirements of the Australasian Rehabilitation Outcomes Centre (AROC) paediatric rehabilitation minimum data set gathered on each patient.

METHODS

Retrospective cohort study of patients seen at PMH between 1996-2016. The AROC minimum dataset information data were gathered on each patient. Functional status and rehabilitation outcomes were assessed using Functional Independence Measure for Children (weeFIM), Canadian Occupational Performance Measure (COPM), and Goal Attainment Scaling (GAS). Patient complexity was captured by documenting the specialty teams involved, the number of readmissions, and the International Statistical Classification of Disease and Related Health Problems Z codes.

RESULTS

Data from 19 patients (13 males, age range 6 months-15 years; 6 females, age range 4 years-13 years) were available. There were 10 cervical TSCIs with a median length of stay of 213 days and 9 thoracic TSCIs with a median length of stay of 49 days. Patients had between zero and six comorbidities prior to their TSCI.

CONCLUSIONS

Children with medical complexity are responsive to rehabilitation but have a high burden of care, requiring multiple-specialty care and hospital re-admissions. AROC has set a minimum data set recommendation for the collection and examination of patient data. PMH meets the AROC guidelines for patient data collection and descriptive analyses.

Raising Mean Arterial Pressure Alone Restores 20% of Intraoperative Neuromonitoring Losses

STUDY DESIGN

Multicenter prospective.

OBJECTIVE

To assess the effect of intraoperative interventions in restoring intraoperative neuromonitoring (IONM) signals in pediatric spine surgery.

SUMMARY OF BACKGROUND DATA

No prior studies have prospectively examined the rate of return of IONM signals by increasing blood pressure (BP) alone.

METHODS

Patients undergoing posterior spinal deformity surgery were enrolled at their preoperative appointment. Surgeons completed an intraoperative data form on patients who experienced an IONM change defined as a 50% or greater decrease in either transcranial motor evoked potentials or somatosensory evoked potentials.

RESULTS

Four hundred fifty two patients were enrolled with 30 (7%) having IONM change. Thirty patients met inclusion criteria (mean age, 12 yrs, range, 5-19) and had the following diagnoses: idiopathic scoliosis (43%), neuromuscular scoliosis (13%), congenital scoliosis (10%), early onset scoliosis (7%), and other (27%). 20% (6/30) had return of signals due to an increase in BP alone with no other interventions (mean arterial pressure [MAP] increased from mean of 68 [range, 58-76] to 86 mmHg [range, 75-95]). Signals returned to baseline after mean of 16 minutes (range, 2-45). In 60% of patients (18/30), MAP was raised from a mean of 72 mmHg (range, 55-84) to 86 mmHg (range, 75-100) in conjunction with other interventions and had mean return of signals in 37 minutes (range, 8-210). Six (20%) of patients had signals return to baseline after a mean of 6 minutes (range, 3-13) in which MAP did not change appreciably. All patients had return of signals at the conclusion of the procedure with one patient having postoperative neurological sequale.

CONCLUSION

In this prospective study of 452 pediatric spinal deformity surgeries, raising MAPs above 85 mmHg should be considered the first step in response to IONM signal changes, as this alone was successful in 20% of patients without sacrificing deformity correction.

LEVEL OF EVIDENCE

2.

The treatment of spinal cord injury in rats using bone marrow-derived neural-like cells induced by cerebrospinal fluid

This study aimed to evaluate the effect of bone mesenchymal stem cells (BMSCs) and BMSC neural-like cells (BMSC-Ns) on the spinal cord injury (SCI) in the rat model of SCI. BMSC-Ns were prepared from the third passage of BMSCs by induction of healthy cerebrospinal fluid (CSF) of an adult human. The SCI rat model was established through a surgical procedure, and after 7 days the rats were randomly divided into 3 (A, B and C) groups. Groups A (BMSC-Ns) and B (BMSCs) were treated with 1 × 10⁶/20 μl cells, while group C (saline) was treated with saline, all via intracerebroventricular injection. After transplantation, the BBB score of group A was significantly higher than that of group B, which in turn was significantly higher than that of group C (P < .05). The levels of Bdnf, Ngf, Ntf3 were statistically significantly higher in group A than those in groups B and C (P < .05). The levels of 5-HT, NA, Ach, DA, GABA in group A were significantly higher than those in groups B and C, whereas the level of Glu was significantly lower in group A than that in groups B and C (P < .05). The histopathological data showed remarkably less necrosis of the spinal cord in group A, compared to that in groups B and C. Transplanting BMSC-Ns or BMSCs into the lateral ventricles improved the neurological function of rats with SCI. Moreover, BMSC-Ns were significantly more effective than BMSCs, which provides a possible approach for the treatment of SCI.

The Recognition, Incidence, and Management of Spinal Cord Monitoring Alerts in Early-onset Scoliosis Surgery

BACKGROUND

The objective of the research was to study the relevance of intraoperative neuromonitoring throughout all stages of surgical management in patients with progressive early-onset scoliosis (EOS).The routine monitoring of spinal cord potentials has gradually become standard of practice among spinal surgeons. However, there is not a consensus that the added expense of this technique necessitates monitoring in all stages of surgical management.

METHODS

A retrospective review of 180 surgical cases of 30 patients with EOS from July 2003 to July 2012 was performed. All monitoring alerts as judged by the neuromonitoring team were identified. Both somatosensory-evoked potentials and transcranial electric motor-evoked potentials were studied and no limiting thresholds for reporting electrophysiological changes were deemed appropriate.

RESULTS

Of 150 monitored cases there were 18 (12%) monitoring alerts. This represented 40% of the patient cohort over the 9-year study period.

CONCLUSIONS

Index versus routine lengthening rate of alerts showed no significant difference in incidence of monitoring alerts. Conversely, several patients whose primary implantation surgeries were uneventful had monitoring alerts later in their treatment course. Intraoperative neuromonitoring is warranted throughout all stages of surgical management of EOS.

LEVEL OF EVIDENCE

Level IV. This study is a retrospective review of surgical cases of 30 patients with EOS.

The Impact of Neurophysiological Intraoperative Monitoring during Spinal Cord and Spine Surgery: A Critical Analysis of 121 Cases

Neuromonitoring has been utilized during spinal surgery to assess the function of the spinal cord in an effort to prevent intraoperative injury. Although its use is widespread, no clear benefit has been demonstrated. Our goal in this study was to interrogate the value of intraoperative neuromonitoring in decreasing the severity and rate of neurological injury during and after spinal surgery. Here we describe our experience of 121 patients who underwent spinal cord procedures with the combination of intraoperative neuromonitoring, to determine its ability to detect neurological changes and the specificity and sensitivity in this setting. The data for the 121 patients who underwent neurophysiological monitoring during various spinal procedures was collected retrospectively. The patients were classified into one of four groups according to the findings of intraoperative monitoring and the clinical outcomes on postoperative neurological exam. Intraoperative monitoring was evaluated for its specificity, sensitivity, and predictive value. In our cohort of 121 patients, the use of intraoperative neuromonitoring had a low sensitivity, which may produce an excessive number of false negatives. Based on these findings, neuromonitoring seems to have a poor positive predictive value and is thus an inappropriate test to prevent harm to patients.

Perioperative and Delayed Major Complications Following Surgical Treatment of Adolescent Idiopathic Scoliosis

BACKGROUND

Reporting accurate surgical complication rates to patients and their families is important in the management of adolescent idiopathic scoliosis (AIS). In this study, we report the rate of major complications following the surgical treatment of AIS both in the perioperative period and among patients with a minimum of 2 years of follow-up.

METHODS

We reviewed the prospectively collected data of a multicenter registry of patients who underwent surgical treatment of AIS during the period of 1995 to 2014 in order to identify all complications. A complication was defined as "major" if it resulted in reoperation or in spinal cord or nerve root injury, or was life-threatening. A total of 3,582 patients with preoperative and early postoperative data (4 to 6 weeks of follow-up) were included. A subset of 2,220 patients with a minimum of 2 years of follow-up comprised the cohort for delayed complications. Overall complication rates were calculated, as was the percentage of complications according to the year of the index surgery and type of surgical approach.

RESULTS

The mean age of the 3,582 patients at the time of surgery was 14.8 ± 2.2 years. The average major curve magnitude was 56° ± 13° for thoracic curves and 51° ± 11° for lumbar. In 365 patients, anterior spinal fusion (ASF) with instrumentation was performed, and in 3,217 patients, posterior spinal fusion (PSF) with instrumentation was performed; 142 patients in the PSF group underwent concomitant anterior release. There were 192 major complications, with 93 (2.6%) occurring perioperatively. Perioperative complications included wound-related (1.0% of the patients), neurologic (0.5%), pulmonary (0.4%), instrumentation-related (0.4%), and gastrointestinal (0.2%) complications. One patient died. The mean annual perioperative major complication rate based on the year of surgery ranged from 0% to 10.5%. The complication rate by surgical approach was 3.0% for ASF and 2.6% for PSF (2.4% for PSF only and 5.6% for PSF with anterior release). The major complication rate for the 2,220 patients with at least 2 years of follow-up was 4.1%; all but 1 had a reoperation (4.1%). The majority of these major complications were wound and instrumentation-related (1.9% and 0.8%, respectively).

CONCLUSIONS

After surgery for AIS, a 2.6% rate of perioperative major complications and a 4.1% rate of major complications at 2 or more years after surgery can be anticipated. The complication rate decreased over the period of study.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Intraoperative motor evoked potential monitoring to patients with preoperative spinal deficits: judging its feasibility and analyzing the significance of rapid signal loss

BACKGROUND CONTEXT

Transcranial motor evoked potential (MEP) monitoring has been widely adopted in spine surgery, but so far the useful monitoring data for patients with preoperative spinal deficits (PPSDs) are limited. Originally we thought that they seemed technically more difficult and less reliable in performing the MEP monitoring to PPSDs.

PURPOSE

Our objective was to study (1) the feasibility of MEP monitoring in PPSDs and the (2) the significance of rapid MEP loss.

STUDY DESIGN/SETTING

A retrospective case notes study from a prospective patient register was used as the study design.

PATIENT SAMPLE

A total of 332 PPSDs who underwent posterior spine surgery with a reliable MEP monitoring were collected between September 2010 and December 2014.

OUTCOME MEASURES

Relevant MEP loss was identified as rapid amplitude reduction (more than 80% MEP) associated with high-risk surgical maneuvers or high-risk diagnoses.

METHOD

The muscles with higher strength were used to record the optimal MEP signal. MEP monitoring of these patients was considered to be feasible if reproducible signals had been obtained; moreover, sensitivity, specificity, positive predictive value (PPV), and negative predictive value were computed. The significance of the patients with rapid MEP loss was analyzed.

RESULTS

From a total of 332 PPSDs, 27 cases showed significant MEP loss (23 true positive, 4 false positive), and 21 showed new spinal deficits. Invalid MEP baselines were found in 11 paralysis and 6 severely incomplete paraplegia patients, and success rate of reliable MEP was 95.1% in PPSDs. The congenital kyphoscoliosis, tuberculous kyphoscoliosis, and thoracic spinal stenosis are considered high-risk diagnoses to result in MEP loss. The sensitivity of intraoperative MEP monitoring was 100%, the specificity 98.7%, the positive predictive value 85.2%, and the negative predictive value 100%.

CONCLUSIONS

Intraoperative MEP monitoring is feasible for most of the PPSDs. The rapid MEP loss during high-risk diagnoses and complicated surgical procedures may indicate new spinal deficits.

Iatrogenic Spinal Cord Injury Resulting From Cervical Spine Surgery

STUDY DESIGN

Retrospective cohort study of prospectively collected data.

OBJECTIVE

To examine the incidence of iatrogenic spinal cord injury following elective cervical spine surgery.

METHODS

A retrospective multicenter case series study involving 21 high-volume surgical centers from the AOSpine North America Clinical Research Network was conducted. Medical records for 17 625 patients who received cervical spine surgery (levels from C2 to C7) between January 1, 2005, and December 31, 2011, were reviewed to identify occurrence of iatrogenic spinal cord injury.

RESULTS

In total, 3 cases of iatrogenic spinal cord injury following cervical spine surgery were identified. Institutional incidence rates ranged from 0.0% to 0.24%. Of the 3 patients with quadriplegia, one underwent anterior-only surgery with 2-level cervical corpectomy, one underwent anterior surgery with corpectomy in addition to posterior surgery, and one underwent posterior decompression and fusion surgery alone. One patient had complete neurologic recovery, one partially recovered, and one did not recover motor function.

CONCLUSION

Iatrogenic spinal cord injury following cervical spine surgery is a rare and devastating adverse event. No standard protocol exists that can guarantee prevention of this complication, and there is a lack of consensus regarding evaluation and treatment when it does occur. Emergent imaging with magnetic resonance imaging or computed tomography myelography to evaluate for compressive etiology or malpositioned instrumentation and avoidance of hypotension should be performed in cases of intraoperative and postoperative spinal cord injury.

Prognosis of Significant Intraoperative Neurophysiologic Monitoring Events in Severe Spinal Deformity Surgery

BACKGROUND

Intraoperative neurophysiologic monitoring has become a standard tool for mitigating neurologic injury during spinal deformity surgery. Significant monitoring changes during deformity correction are relatively uncommon. This study characterizes precipitating factors for neurologic injury and relates significant events and postoperative neurologic prognosis.

METHODS

All spinal deformity surgeries at a West African hospital over a 12-month period were reviewed. Patients were included if complete operative reports, monitoring data, and postoperative neurologic examinations were available for review. Surgical and systemic triggers of monitoring events were recorded and neurologic status was followed for 6 weeks postoperatively.

RESULTS

Eighty-eight patients met inclusion criteria. The average age was 14 years (3-28). The average kyphosis was 108° (54°-176°) and average scoliosis was 100° (48°-177°). There were 44 separate neurologic events in 34 patients (39%). The most common triggers were traction or positioning (16), posterior column osteotomies/vertebral column resections (9/1), and distraction, corrective maneuvers, or implant placement (12). On surgery completion, 100% (12/12) of events from non-osteotomy-related surgical procedures, 75% (12/16) of events from traction or positioning resolved; however, 0% (0/10) of events from osteotomies resolved completely. Eight percent (7/88) had new neurologic deficits postoperatively, all with intraoperative monitoring changes. In 6 of these 7 patients, the event was attributed to an osteotomy; in 1 patient the cause was not determined. At 6-week follow-up, all patients had some preserved motor function bilaterally with the ability to walk (ASIA D/E) or recovered completely.

CONCLUSIONS

Intraoperative signal changes were most frequently from traction or positioning. However, the most common cause of persistent neurologic deterioration and the only cause of postoperative neurologic deficit was the performance of osteotomies. Unlike traction- or instrument-related correction, osteotomies produce irreversible changes, from canal intrusion or sudden localized deformity change. The incidence of postoperative neurologic deficit is very low when the inciting cause is reversed; however, osteotomy-related events are irreversible, with a high incidence of associated lasting neurologic injury.

Complications following spine fusion for adolescent idiopathic scoliosis

Complications following spine fusion for adolescent idiopathic scoliosis can be characterized as either intra-operative or post-operative. The most serious and feared complication is neurologic injury, both in the intra- and post-operative period. Other intra-operative complications include dural tears and ophthalmologic or peripheral nerve deficits, which may be related to positioning. Among the most common post-operative complications are surgical site infection, venous thromboembolism, gastrointestinal complications, and implant-related complications. Significant blood loss requiring transfusion, traditionally considered a known sequelae of spine fusion, is now being recognized as a "complication" in large national databases. Pediatric spine surgeons who care for patients with AIS must be thoroughly familiar with all potential complications and their management.

Return of motor evoked potentials after knee flexion in the setting of high-grade spondylolisthesis

PURPOSE

To present a case of loss of motor-evoked potentials (MEPs) to the left foot in the supine position after a partial reduction and instrumented fusion from L4 to pelvis which was managed successfully without revision or removal of implants.

METHODS

We report a patient with high-grade spondylolisthesis who demonstrated loss of motor-evoked potentials after posterior spinal fusion and transfer to supine position. The patient's knees were flexed to 90° and signals were immediately restored. Systemic steroids were administered and circumferential fusion was delayed 21 days. Anterior-interbody cage was placed without complication.

RESULTS

She was discharged on post-operative day 2. At 7 months, she is pain free and doing well with plans to return to gymnastics completely.

CONCLUSIONS

Knee flexion can be instituted when encountering a neuromonitoring signal change following posterior spinal fusion for spondylolisthesis as a means to alleviate acute nerve stretch injury and may in some cases prevent the need to lessen the correction.

LEVEL OF EVIDENCE

IV.

Epidemiology of persistent iatrogenic spinal cord injuries in Western Norway

OBJECTIVES

Iatrogenic spinal cord injuries (SCIs) caused by invasive procedures or surgical interventions have previously been reported as case studies. The primary objective of this study was to investigate and analyze the incidence, etiology, and prognosis of iatrogenic SCI in Western Norway.

METHODS

Medical records of all 183 patients admitted to the SCU between 01.01.2004 and 31.12.2013 were reviewed. Gender, age, diagnosis, iatrogenic medical procedure, symptoms and findings before and after injury, mechanism of injury, level of injury, and ASIA Impairment Scale (AIS) score prior iatrogenic SCI, at admittance and discharge were recorded, as were the length of the period prior to admittance and the length of stay.

RESULTS

Twenty-three (12.5%; 14 men, nine women) of 183 patients met the criteria for iatrogenic SCI. The annual incidence rate was estimated 2,3 per 1,000,000 (SD ±1.0). Mean age at iatrogenic SCI was 55.5 years (range 16-79 years). Intervention for cervical spinal stenosis was the leading cause of iatrogenic SCI, followed by operations on the aorta and spine. Iatrogenic SCIs was most frequently located on the thoracic level. The patients suffered from clinical incomplete injuries (AIS score C and D) both at admittance and discharge from the SCU. Most patients improved, but no patient recovered completely after SCI.

CONCLUSION

Although the annual incidence rate of iatrogenic SCI is low in Norway, individual consequences are serious. Increased awareness of the causes of SCI may decrease the risk of iatrogenic SCI.

Reversible Intraoperative Neurophysiologic Monitoring Alerts in Patients Undergoing Arthrodesis for Adolescent Idiopathic Scoliosis: What Are the Outcomes of Surgery?

BACKGROUND

Confidence in intraoperative neurophysiologic monitoring (IONM) data can allow scoliosis surgeons to proceed with surgery even after a monitoring alert, assuming the recovery of signals. We sought to determine the outcomes of surgical treatment of adolescent idiopathic scoliosis (AIS) after a notable IONM alert.

METHODS

We identified 676 patients who underwent arthrodesis with use of IONM for the treatment of AIS. The patients were divided into 2 cohorts: those who experienced a lower-extremity IONM alert and those who did not. An alert was defined as a notable change in IONM data, specifically, a ≥50% drop in somatosensory evoked potentials (SSEPs) and/or in transcranial motor evoked potentials (tcMEPs).

RESULTS

Of the 676 patients, 36 (5.3%) experienced IONM alerts. Those patients had a larger preoperative major Cobb angle (mean of 61° ± 13° compared with 55° ± 12° for the no-alert group; p < 0.01), a greater number of levels fused (mean of 12 ± 2 compared with 11 ± 2; p < 0.01), a longer operative duration (mean of 357 ± 157 minutes compared with 298 ± 117 minutes; p < 0.01), a higher estimated blood loss (1,857 ± 1,323 mL compared with 999 ± 796 mL; p < 0.01), and a greater volume of autologous blood transfused (mean of 527 ± 525 mL compared with 268 ± 327 mL; p < 0.01). Among patients who experienced an alert and had a completed operation (34 of 36 patients), mean postoperative radiographic measurements were similar to those of the no-alert group in terms of the percentage of correction of the major Cobb angle (alert, 66% ± 13%; no alert, 64% ± 19%; p = 0.53) and of rib prominence (alert, 49% ± 36%; no alert, 47% ± 46%; p = 0.83) and measurement of thoracic kyphosis (alert, 23° ± 10°; no alert, 22° ± 2°; p = 0.58). The Scoliosis Research Society (SRS)-22 outcome scores were also similar between the 2 cohorts.

CONCLUSIONS

Notable IONM changes occurred in 5.3% of the patients who underwent arthrodesis for AIS. Those patients had larger preoperative deformity, a longer operative duration, a greater number of levels fused, a higher estimated blood loss, and a greater volume of autologous blood transfused. Return of IONM data guided the surgeon to safely complete the procedure in 34 of 36 patients, with correction similar to that of patients who did not experience an alert.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.