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STUDY DESIGN: Cross-sectional, international survey. OBJECTIVES: To evaluate the knowledge of spine surgeons regarding the use of electromyography (EMG) and nerve conduction studies (NCS) for degenerative cervical spine conditions (DCC). METHODS: All members of AO Spine International were emailed an anonymous survey to evaluate their clinical knowledge about the use of EMG and nerve conduction studies for DCC. Descriptive statistics were used to analyze the results, as well as to compare the answers among different groups of surgeons and assess demographic characteristics. RESULTS: A total of 402 participants answered the survey, 91.79% were men from the 5 continents. There were 221 orthopedic surgeons (55.39%) and 171 neurosurgeons (42.86%), more than a half of them with a complete spinal fellowship (56.44%). The most common reasons that surgeons obtain the test is to differentiate a radiculopathy from a peripheral nerve compression (88.06%). As a group, the responding surgeons' knowledge regarding EMG-NCS was poor. Only 53.46% of surgeons correctly answered that EMG-NCS is unable to differentiate a C5 from a C6 radiculopathy. Only 23.47% of the surgeons knew that EMG-NCS are not able to diagnose a pre vs a post-fixed brachial plexus. Only 25% of the surgeons correctly answered a question regarding the test's ability to diagnose other neurological diseases. CONCLUSIONS: We found that our respondents' knowledge regarding EMG-NCS for DCC was poor. Identifying the weak points of knowledge about EMG-NCS may help to educate surgeons on the indications for the test and the proper way to interpret the results.

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OBJECTIVE: To perform a systematic literature review on revision surgeries at the index level after cervical disc arthroplasty (CDA) failure. METHODS: A systematic literature review was performed according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Prospective studies on patients who required a secondary surgery after CDA failure were included for analysis. The minimum follow-up for these studies was 5 years. RESULTS: Out of 864 studies in the original search group, a total of 20 studies were included. From a total of 4,087 patients, 161 patients required a reoperation at the index level. A total of 170 surgeries were performed, as some patients required multiple surgeries. The most common secondary procedures were anterior cervical discectomy and fusion (ACDF) (68%, N = 61) and posterior cervical fusion (15.5%, N = 14), followed by other reoperation (13.3%, N = 12). The associated outcomes for those who required a revision surgery were rarely mentioned in the included literature. CONCLUSION: The long-term revision rate at the index level of failed CDA surgery was 3.9%, with a minimum 5-year follow-up. ACDF was the most commonly performed procedure to salvage a failed CDA. Some patients who required a new surgery after CDA failure may require a more extensive salvage procedure and even subsequent surgeries.

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Generally, a combined anterior and posterior cervical approach is associated with significant morbidity since it requires an extended operative time, greater intraoperative blood loss, and both anterior- and posterior-related surgical complications. However, there are some instances where a circumferential cervical fusion can be advantageous. Our objective is to discuss the indications for circumferential cervical spine procedures. A narrative review of the literature was performed. We include the indications for circumferential cervical approaches of the senior author (KDR). Indications for circumferential approaches include: (1) high-risk patients for pseudoarthrosis, (2) cervical deformity (e.g. , degenerative, posttraumatic, cervicothoracic kyphosis), (3) cervical spine metastases (especially those with multilevel involvement), (4) cervical spine infection, (5) unstable cervical trauma, (6) movement disorders and cerebral palsy, (7) Multiply operated patient (especially postlaminectomy kyphosis and patients with massive ossification of the posterior longitudinal ligament), and when (8) early fusion is desirable. Circumferential procedures may be useful in many different cervical spine conditions requiring surgery. Despite its advantages, particularly with reducing the risk for pseudarthrosis, the benefits of a combined approach must be weighed against the risks associated with a dual approach. With appropriate preoperative planning, intraoperative decision-making, and surgical techniques, excellent clinical outcomes can be achieved.

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PURPOSE: Cervical disc arthroplasty (CDA) has become an increasingly popular treatment for cervical degenerative disc disease. One potential complication is osteolysis. However, current literature on this topic appears limited. The purpose of this study is to elucidate the incidence, aetiology, consequence, and subsequent treatment of this complication. METHODS: A systematic literature review was performed according to the PRISMA guidelines. Studies discussing the causes, incidence and management of osteolysis after a CA were included. RESULTS: A total of nine studies were included. We divided these studies into two groups: (1) large case series in which an active radiological evaluation for osteolysis was performed (total = six studies), (2) case report studies, which discussed symptomatic cases of osteolysis (total = three). The incidence of asymptomatic osteolysis ranged from 8 to 64%; however, only one study reported an incidence of < 10% and when this case was excluded the incidence ranged from 44 to 64%. Severe asymptomatic bone loss (exposure of the implant) was found in less than 4% of patients. Bone loss from osteolysis appeared to occur early (< 1 year) after surgery and late (> 1 year) as well. Symptomatic patients with osteolysis often required revision surgery. These patients required removal of implant and conversion to fusion in the majority of the cases. CONCLUSIONS: Osteolysis after CDA is common; however, the majority of cases have only mild or asymptomatic presentations that do not require revision surgery. The timing of osteolysis varies significantly. This may be due to differences in the aetiology of osteolysis.

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STUDY DESIGN: Narrative literature review. OBJECTIVE: To review and present details on the occipitocervical fixation (OCF) technique as well as considerations for planning the procedure. METHODS: We present the surgical technique of OCF in a step-by-step didactic and practical manner with surgical tips and tricks, including C1 and C2 screw fixation techniques. Additionally, we discuss complications, the extension of fusion, types of OCF, and how to avoid common side effects associated with OCF. RESULTS: The complex and mobile anatomy of the craniocervical junction, when requiring fixation and fusion, warrants rigid instrumentation that can be achieve using a modern screw-plate-rod construct. Indications for OCF are craniocervical instability, and atlantoaxial instability when selective atlantoaxial fusion is not feasible. OCF generally involves occiput-C2 fusion. C1 fixation is generally unnecessary, since it increases the surgical time and is associated with the risk of vascular complications. Selective occiput-C2 fusion is recommended when there is no need for including the cervical subaxial region (eg, when stenosis or fractures coexist in the subaxial spine), and good fixation is achieved at C2. Most instrumentation systems now have occipital plates that are not pre-integrated to rods, making fixation much simpler. Surgical steps, from position to wound closure, are presented in detail, with pearls for practice and discussion of cervical alignment. CONCLUSIONS: OCF is a challenging procedure, with potential risk of severe adverse effects. Understanding the surgical indications, as well as the nuances of the surgical technique, is required to improve patient outcomes and avoid complications.

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STUDY DESIGN: An analysis of employment status data up to 10 years following the Federal Drug Administration (FDA) Investigational Device Exemption (IDE) randomized trial and extension as post-approval study comparing BRYAN cervical disc (Medtronic, Minneapolis, MN) arthroplasty (CDA) versus single-level anterior cervical discectomy and fusion (ACDF) was performed. OBJECTIVE: Ten-year experience with the BRYAN disc arthroplasty trial provides opportunity to report patient employment data. SUMMARY OF BACKGROUND DATA: The long-term consequences of arthroplasty remain incomplete, including the occurrence of occupational compromise. METHODS: Patients' employment status were measured at regular intervals in both groups up to 10 years. RESULTS: The preoperative employment status proportion was comparable between investigational (BRYAN CDA) and control (ACDF) groups. In the investigational group, 49.2% returned to work at 6 weeks compared with 39.4% of the control group (P = 0.046). At 6 months and 2 years postoperatively, there was a similar likelihood of active employment in both groups. After 2 years at all time points, 10% drop-off seen in control group employment, but not in investigational group. At 10 years, 76.2% CDA patients were employed to 64.1% ACDF patients (P = 0.057). Preoperative variables influencing work status at 10 years following CDA included: preoperative work status, age, and SF-36 Mental Component Score (SF-36 MCS); whereas, no significant preoperative factor identified with ACDF. Time to return to work was influenced in both groups by preoperative work status; and in the ACDF group: reaching age 65 at 10-year visit, preoperative arm pain and NDI score had significant influences. CONCLUSION: More patients returned to work at 6 weeks after CDA compared with ACDF, although there was no difference by 6 months. After 2 years, a nonsignificant trend toward higher employment rates in the arthroplasty group was evident, but this difference could not be validated due to the very high rate of loss of patients to the follow-up. LEVEL OF EVIDENCE: 2.

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Posterior cervical spine fixation is a key component in achieving spinal arthrodesis for treating various cervical spine pathologies including neoplastic, inflammatory, traumatic and degenerative diseases. Historically, various wiring techniques had played major roles in posterior cervical spine fixation. Today, posterior cervical screw fixation is utilized by most spine surgeons instead of wiring for its superior biomechanical strength. A review of lateral mass, pedicle, intralaminar and transfacet screw fixation techniques in the subaxial cervical spine is presented in a detailed fashion. A comparison among different posterior cervical subaxial fixation techniques is also included. Although the safety of freehand techniques was demonstrated in the majority of the existing studies, real-time navigation is becoming increasingly utilized for cervical screw insertion, especially for cervical pedicle screws, where the freehand technique is technically demanding and may carry a higher risk of neurovascular injury. Several different posterior screw fixation techniques exist for the subaxial cervical spine with generally low complication rate. Spine surgeons should be familiar with these techniques and choose the optimal technique based on each patient's individual anatomy and surgical needs.

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Due to the highly mobile nature of the cervical spine, and the fact that most magnetic resonance imagings (MRIs) and computed tomography scans are obtained only in one single position, dynamic cord compression can be an elusive diagnosis that is often missed and not well-understood. In this context, dynamic MRI (dMRI) has been utilized to improve the diagnostic accuracy of cervical stenosis. We performed a literature review on dynamic cord compression in the context of cervical spondylotic myelopathy (CSM), with particular emphasis on the role of dMRI. Cadaveric studies report that the spinal cord lengthens in flexion and the spinal canal dimension increases, whereas the spinal cord relaxes and shortens in extension and the spinal canal decreases. These changes may lead to biomechanical stress in the spinal cord with movement, especially in patients with critical cervical stenosis. The majority of the studies using dMRI in CSM reported that this imaging modality is more sensitive at detecting cervical cord compression compared to routine MRIs done in a neutral position, especially with the neck in extension. Dynamic MRI was also useful to diagnose dynamic cervical cord compression after laminectomies in patients with clinical deterioration without evident cord compression on neutral static MRI. Finally, dMRI is more sensitive in detecting stenosis in patients with CSM than in those with ossification of the posterior longitudinal ligament (OPLL), likely because OPLL patients often have a more limited range of motion than CSM patients. Thus, dMRI is a promising new tool that can help spine surgeons in diagnosing and treating CSM.

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C1 stenosis is often an easily missed cause for cervical myelopathy. The vast majority of cervical myelopathy occurs in the subaxial cervical spine. The cervical canal is generally largest at C1/2, explaining the relatively rare incidence of neurological deficits in patients with odontoid fractures. However, some subjects have anatomical anomalies of the atlas, which may cause stenosis and result in clinical symptoms similar to subaxial cord compression. Isolated pure atlas hypoplasia leading to stenosis is quite rare and may be associated with other anomalies, such as atlas clefts or transverse ligament calcification. It may also be more commonly associated with syndromic conditions such as Down or Turner syndrome. Although the diagnosis can be easily made with a cervical magnetic resonance imaging, the C3/2 spinolaminar test using a lateral cervical plain radiograph is a useful and sensitive tool for screening. Surgical treatment with a C1 laminectomy is generally necessary and any atlantoaxial or occipito-atlanto instability must be treated with spinal stabilization and fusion.

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The diagnosis of cervical spondylotic myelopathy (CSM) is made based on clinical signs and symptoms, and then confirmed with magnetic resonance imaging (MRI) or CT myelogram. Due to the highly mobile nature of the cervical spine, and the fact that most MRIs and CTs are obtained only in one single position, dynamic cord compression can be an elusive diagnosis that is often missed and not well-understood. In this context, dynamic MRI (dMRI) has been utilized to improve the diagnostic accuracy of cervical stenosis in cases where static MRI does not provide enough information to establish a diagnosis or to provide additional information. We performed a literature review on dynamic cord compression in the context of CSM, with particular emphasis on the role of dynamic MRI (dMRI). Cadaveric studies report that the spinal cord lengthens in flexion and the spinal canal dimension increases, whereas the spinal cord relaxes and shortens in extension and the spinal canal decreases. These changes may lead to biomechanical stress in the spinal cord with movement, especially in patients with critical cervical stenosis. The majority of the studies using dMRI in CSM reported that this imaging modality is more sensitive at detecting cervical cord compression compared to routine MRIs done in a neutral position, especially with the neck in extension. Occult anterior compression has also been reported by some authors in flexion, but occurs less frequently. DMRI was also useful to diagnose dynamic cervical cord compression after laminectomies in patients with clinical deterioration without evident cord compression on neutral static MRI. Finally, dMRI are more sensitive in detecting stenosis in patients with CSM than in those with OPLL, likely because OPLL patients often have a more limited ROM than CSM patients. Thus, dMRI is a promising new tool that can help spine surgeons in diagnosing and treating CSM. However, further studies are needed to establish the utilization criteria and the clinical value of dMRI.

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Odontoidectomy is indicated for some cases of ventral compression in the upper cervical spine. In this paper, we discuss the indications, surgical steps, and nuances of transoral odondoidectomy (TO) and endoscopic endonasal (EE) odontoidectomy. We compare both approaches and discuss the advantages and disadvantages of each. A broad narrative literature review was performed. We also added tips and surgical pearls of the senior author (KDR) in performing odontoidectomies. Surgical techniques were presented. EE is performed in patients where the dens is located above the nasopalatine line. Although technically more demanding, EE has less soft tissue injury and potentially less risk of dysphonia and dysphagia. The TO approach provides a wider exposure and is not limited by the nasopalatine line. Additionally, the TO approach allows the ability for a more extensive resection of C2; these could include the C2 body and the C2­3 disc space. Ventral reconstructions with cages and plates are also feasible via the TO approach. However, there are additional risks of prolonged intubation and tracheostomy with the TO approach. Surgeons who manage upper cervical spine disease should be comfortable performing both approaches, and selecting the best approach should be determined using patient-specific characteristics.

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INTRODUCTION: Cervical disc arthroplasty (CDA) was developed to decrease the rate of symptomatic adjacent-level disease while preserving motion in the cervical spine. METHODS: The objectives of this paper are to provide criteria for proper patient selection as well as to present a comprehensive literature review of the current evidence for CDA, including randomized studies, the most recent meta-analysis findings, and long-term follow-up clinical trials as well. RESULTS: Currently, there are several prospective randomized controlled studies of level I of evidence attesting to the safety and efficacy of CDA in the management of cervical spondylotic disease (CSD) for one- or two-level degenerative diseases. These as well as recent meta-analyses suggest that CDA is potentially similar or even superior to anterior cervical discectomy and fusion (ACDF) when considering several outcomes, including dysphagia and re-operation rate over medium-term follow-up. Less robust studies have also reported satisfactory clinical and radiological outcomes of CDA for hybrid procedures (ACDF combined with CDA), non-contiguous disease, and even for multilevel disease (more than 2 levels). CONCLUSIONS: Based on this evidence we conclude that CDA is a safe and effective alternative to ACDF in properly selected patients for one- or two-level diseases. Defining superiority of specific implants and detailing optimal surgical indications will require further well-designed long-term studies.

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Although relatively rare, post-operative nerve injuries may occur after cervical spine procedures. The most common post-operative neural disorder is C5 nerve palsy. The risk factors for C5 nerve palsy are male gender, OPLL, and posterior cervical approaches. It generally presents with deltoid and/or biceps weakness, and may present immediately or several days after surgery. Treatment is generally conservative due to transient duration of symptoms, but evaluation of residual compression at C4-5 is essential. PTS (Parsonage-Turner syndrome) is an idiopathic plexopathy generally presenting with severe neuropathic pain in the shoulder, neck, and arms, followed by neurological deficits involving the upper brachial plexus. The deficits typically present in a delayed fashion after the onset of pain. Once residual nerve compression is ruled out, initial treatment is based on pain control and physical therapy. Post-operative C8-T1 nerve palsies occur with weakness of the five intrinsic muscles of the hand innervated by the medial nerve, with sensory symptoms in the territory innervated by the ulnar nerve (ulnar two digits of the hand), and also the medial forearm. The risk factors for C8-T1 nerve injuries after surgery are C7 pedicle subtraction osteotomies and posterior fixation of the cervico-thoracic junction, especially in patients with preoperative C7-T1 stenosis. A wide foraminal decompression at C7-T1 region is necessary to minimize risk of this complication. Finally, Horner's syndrome can occur post-operatively, especially after anterolateral approaches to the middle and lower levels of the cervical spine. It is characterized by ipsilateral papillary miosis, facial anhydrosis, and ptosis secondary to injury of the cervical sympathetic nerves. Avoid using the cautery on the lateral border of the longus colli muscle, where the sympathetic chain lies and place the retractors properly underneath the muscle to decrease the chance of sympathetic injuries. It can also occur from iatrogenic compression or injury to the T1 nerve root, as the sympathetic chain gets some of its fibers from that level. Understanding the most common potential nerve injuries after cervical spine procedures is helpful in prevention, early diagnosis, and appropriate management.

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STUDY DESIGN: A narrative literature review. OBJECTIVES: To review the surgical techniques of posterior screw fixation in the subaxial cervical spine. METHODS: A broad literature review on the most common screw fixation techniques including lateral mass, pedicle, intralaminar and transfacet screws was performed on PubMed. The techniques and surgical nuances are summarized. RESULTS: The following techniques were described in detail and presented with illustrative figures, including (1) lateral mass screw insertion: by Roy-Camille, Louis, Magerl, Anderson, An, Riew techniques and also a modified technique for C7 lateral mass fixation; (2) pedicle screw fixation technique as described by Abumi and also a freehand technique description; (3) intralaminar screw fixation; and finally, (4) transfacet screw fixation, as described by Takayasu, DalCanto, Klekamp, and Miyanji. CONCLUSIONS: Many different techniques of subaxial screw fixation were described and are available. To know the nuances of each one allows surgeons to choose the best option for each patient, improving the success of the fixation and decrease complications.

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STUDY DESIGN: Cross-sectional study. OBJECTIVES: To continue the line of a previous publication using steroid for acute spinal cord injury (SCI) by spine surgeons from Latin America (LA) and assess the current status of methylprednisolone (MP) prescription in Europe (EU), Asia Pacific (AP), North America (NA), and Middle East (ME) to determine targets for educational activities suitable for each region. METHODS: The English version of a previously published questionnaire was used to evaluate opinions about MP administration in acute SCI in LA, EU, AP, NA, and ME. This Internet-based survey was conducted by members of AOSpine. The questionnaire asked about demographic features, background with management of spine trauma patients, routine administration of MP in acute SCI, and reasons for MP administration. RESULTS: A total of 2659 responses were obtained for the electronic questionnaire from LA, EU, AP, NA, and ME. The number of spine surgeons that treat SCI was 2206 (83%). The steroid was used by 1198 (52.9%) surgeons. The uses of MP were based predominantly on the National Acute Spinal Cord Injury Study III study (n = 595, 50%). The answers were most frequently given by spine surgeons from AP, ME, and LA. These regions presented a statistically significant difference from North America (P < .001). The number of SCI patients treated per year inversely influenced the use of MP. The higher the number of patients treated, the lower the administration rates of MP observed. CONCLUSIONS: The study identified potential targets for educational campaigns, aiming to reduce inappropriate practices of MP administration.

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In this article, we present the techniques of axis screw fixation (laminar, pars, pedicle and transarticular screws), discussing the indications and contraindications of each one, as well as surgical tips and anatomical landmarks.

No presente artigo, apresentamos as técnicas de fixação do áxis com parafusos (lamina, parafusos de pars, pedículo e transarticular), discutindos as indicações e contraindicações das mesmas, assim como dicas cirúrgicas e parâmetros anatômicos relevantes.

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OBJECT: Lumbar discectomy is one of the most common surgical spine procedures. In order to understand the value of this surgical care, it is important to understand the costs to the health care system and patient for good results. The objective of this study was to evaluate for the first time the cost-effectiveness of spine surgery in Latin America for lumbar discectomy in terms of cost per quality-adjusted life year (QALY) gained for patients in Brazil. METHODS: The authors performed a prospective cohort study involving 143 consecutive patients who underwent open discectomy for lumbar disc herniation (LDH). Patient-reported outcomes were assessed utilizing the SF-6D, which is derived from a 12-month variation of the SF-36. Direct medical costs included medical reimbursement, costs of hospital care, and overall resource consumption. Disability losses were considered indirect costs. A 4-year horizon with 3% discounting was applied to health-utilities estimates. Sensitivity analysis was performed by varying utility gain by 20%. The costs were expressed in Reais (R$) and US dollars ($), applying an exchange rate of 2.4:1 (the rate at the time of manuscript preparation). RESULTS: The direct and indirect costs of open lumbar discectomy were estimated at an average of R$3426.72 ($1427.80) and R$2027.67 ($844.86), respectively. The mean total cost of treatment was estimated at R$5454.40 ($2272.66) (SD R$2709.17 [$1128.82]). The SF-6D utility gain was 0.044 (95% CI 0.03197-0.05923, p = 0.017) at 12 months. The 4-year discounted QALY gain was 0.176928. The estimated cost-utility ratio was R$30,828.35 ($12,845.14) per QALY gained. The sensitivity analysis showed a range of R$25,690.29 ($10,714.28) to R$38,535.44 ($16,056.43) per QALY gained. CONCLUSIONS: The use of open lumbar discectomy to treat LDH is associated with a significant improvement in patient outcomes as measured by the SF-6D. Open lumbar discectomy performed in the Brazilian supplementary health care system provides a cost-utility ratio of R$30,828.35 ($12,845.14) per QALY. The value of acceptable cost-effectiveness will vary by country and region.

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