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Background: C5 palsy is a frequent complication following cervical spine surgery, particularly after posterior approaches. Although several risk factors have been proposed, the incidence of C5 palsy after anterior cervical discectomy and fusion (ACDF) remains less well understood. This study aims to elucidate the risk factors and neurological recovery associated with C5 palsy following ACDF., Methods: A total of 330 patients who underwent one or two-level ACDF between January 2018 and December 2022 across three institutions within the neurosurgical training program were retrospectively included and analyzed. Demographic, surgical, and radiological data were collected., Results: Sixteen (4.8 %) patients developed postoperative C5 palsy, with a significantly high incidence observed in patients exhibiting preoperative symptoms (radiculopathy or radiculomyelopathy) and undergoing two-level ACDF (p-values 0.008 and 0.018, respectively). No other demographic or radiological factors were associated with C5 palsy. Eleven of 16 (68.8 %) patients experienced C5 palsy within 1 day post-surgery (early-onset group), whereas the remaining five developed symptoms between 4 to 15 days post-surgery (late-onset group). At one year post-surgery, the late-onset group demonstrated superior recovery from C5 palsy compared to the recovery noted in the early-onset group (100 % vs 44.4 %)., Conclusions: Surgeons should be cognizant of the potential for C5 palsy following one- or two-level ACDF, despite generally favorable neurological outcomes. The timing of C5 palsy onset post-ACDF, potentially influenced by mechanisms such as direct injury and ischemia-reperfusion injury, could impact the recovery prognosis. Careful surgical procedure might be the key to success., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objective: An increasing number of studies have shown that a robotic guidance system (RGS) can provide accurate cervical pedicle screw (CPS) placement. The accuracy of CPS placement with an RGS has mostly been evaluated according to the magnitude of pedicular cortical violation. However, an RGS assists in pedicle screw (PS) placement by directly indicating the preplanned trajectory in the operative field. Therefore, investigating how accurately the planned trajectory is executed is essential to determine the accuracy of CPS placement using an RGS, in addition to evaluating the clinical accuracy. Hence, this study aimed to evaluate the accuracy of CPS placement using an RGS by comparing the executed trajectory with the planned trajectory., Methods: This prospective study analyzed 174 CPSs placed between C2 and C6 in 39 consecutive patients who underwent cervical fusion surgery using an RGS. The deviation of the executed CPS trajectory from the planned trajectory was measured at the entry point and at a depth of 20 mm in both the axial and sagittal planes on CT images. Additionally, its direction was noted (lateral or medial in the axial plane and cephalad or caudal in the sagittal plane). These measurements were analyzed according to spinal levels (C2 and C3-C6), laterality (right and left sides), and registration material (preoperative and intraoperative CT images). Furthermore, clinical accuracy was assessed using the Neo classification (grades 0-3)., Results: Overall, the mean (± SD) deviations from the planned trajectory at the entry point and at a depth of 20 mm were 0.79 ± 0.65 mm and 0.86 ± 0.69 mm in the axial plane and 0.88 ± 0.81 mm and 0.82 ± 0.79 mm in the sagittal plane, respectively. When separately examining the deviations according to spinal level, laterality, and registration material, the mean deviations were < 1 mm at any point. Analysis of the deviation direction showed that the CPSs were placed divergently from the planned trajectory in the axial plane. In the sagittal plane, the CPSs were likely to be inserted parallel to the planned trajectory. However, at C2 the CPSs were placed in the caudal direction relative to the planned trajectory. Regarding clinical accuracy, the acceptable rates (grades 0 and 1) were 97.7% and 97.1% in the axial and sagittal planes, respectively, without any CPS-related complications., Conclusions: This study suggests that an RGS can reliably execute planned trajectories, aiding accurate CPS placement in clinical settings.

Background Context: During the radiographic examination, the cranium orientation varies not only individually but also within the same subject, in different imaging sessions. Knowing how changes in the orientation of the cranium influences cervical sagittal alignment during the radiographic examination of the cervical spine can aid clinicians in the accurate evaluation for cervical sagittal alignment in clinical practice., Purpose: To radiographically examine the influence of cranium orientation on cervical sagittal alignment during radiographic examination in an asymptomatic cohort., Study Design: A prospective radiographic study., Patient Sample: Eighty asymptomatic volunteers (mean age, 40.4 years; 50.0% male) were enrolled., Outcome Measures: Cervical sagittal parameters including the regional slope (C1 slope, C2 slope, C5 slope, C7 slope, and T1 slope), Cobb angle (O-C1 angle, C1-C2 angle, C2-C5 angle, C5-C7 angle, and C7-T1 angle), and cranial/cervical offset (sella turcica tilt [ST tilt] and C2 tilt)., Methods: In all participants, standing lateral radiographs of the cervical spine were taken in 3 forward-gazing positions: anteverted-cranium (AC) position; neutral-cranium (NC) position; and retroverted-cranium (RC) position. Cervical sagittal parameters, including the regional slope, Cobb angle, and cranial/cervical offset, in these 3 positions were statistically compared., Results: The C1 and C2 slopes were anteverted and retroverted in the AC and RC positions, respectively, compared to those in the NC position. The C5 slope, C7 slope, and T1 slope were constant among the 3 positions. In O-C2 and C2-C5, statistically significant differences in the regional Cobb angles were identified among the 3 positions; however, there were no significant differences in the C5-C7 or C7-T1 segments. Cranial and cervical offsets of ST tilt and C2 tilt increased and decreased when the cranium was anteverted and retroverted, respectively., Conclusions: The current study suggests that the adjustment of the cranium orientation when taking cervical spine radiographs is mainly controlled at the upper cervical spine of the O-C2 segment in an asymptomatic cohort. On radiograph, alignment in the upper cervical segment of O-C2 changes; accordingly, the middle cervical segment of C2-C5 can change during the adjustment of cranium orientation. However, alignment in the lower cervical segment of C5-C7 and the cervicothoracic junction of C7-T1 remains constant. Further, cranial/cervical offset increases and decreases when the cranium is anteverted and retroverted, respectively. Our results can help the accurate evaluation of cervical sagittal alignment on plain radiographs in clinical practice., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Study Design: A retrospective study., Objective: To compare the accuracy of cervical pedicle screw (CPS) placement using a robotic guidance system (RGS) with that of using an image guidance system (IGS; navigation system) through propensity score matching., Background: The RGS may provide accurate CPS placement, which may outperform IGS. However, no study has directly compared the accuracy of CPS placement with the RGS to that with the IGS., Patients and Methods: We retrospectively reviewed the data of patients who had undergone cervical fusion surgery using CPS with the RGS or IGS. To adjust for potential confounders (patient demographic characteristics, disease etiology, and registration material), propensity score matching was performed, creating robotic guidance (RG) and matched image guidance (IG) groups. The accuracy of CPS placement from C2 to C6, where the vertebral artery runs, was evaluated on postoperative computed tomography images according to the Neo classification (grade 0 to grade 3). Furthermore, the intraoperative CPS revisions and related complications were examined., Results: Using propensity score matching, 22 patients were included in the RG and matched groups each, and a total of 95 and 105 CPSs, respectively, were included in the analysis. In both the axial and sagittal planes, the clinically acceptable rate (grades 0 + 1) of CPS placement did not differ between the RG and matched IG groups (97.9% vs 94.3% and 95.8% vs 96.2%, respectively). The incidence of CPS revision was similar between the groups (2.1% vs 2.9%), and no CPS-related complications were documented. Meanwhile, the incidence of lateral breach (grades 1 + 2 + 3) was significantly lower in the RG group than in the matched IG group (1.1% vs 7.7%, P = 0.037)., Conclusion: The RGS and IGS can equally aid in accurate and safe CPS placement in clinical settings. Nonetheless, RGS can further reduce the lateral breach, compared with IGS., Competing Interests: M.N. has received royalties from Johnson & Johnson DePuy Synthes. The remaining authors declare no conflict of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Kyphotic deformity following the loss of cervical lordosis can lead to unfavourable neurological recovery after cervical laminoplasty (CLP); therefore, it is essential to identify its risk factors. Recent studies have demonstrated that the dynamic parameters of the cervical spine, based on baseline flexion/extension radiographs, are highly useful to estimate the loss of cervical lordosis after CLP. However, it remains unclear whether such dynamic parameters can predict kyphotic deformity development after CLP. Hence, the present study aimed to investigate whether the dynamic parameters could predict kyphotic deformity in patients with cervical spondylotic myelopathy (CSM) after CLP. This retrospective study included 165 patients, consisting of 10 and 155 patients with and without cervical kyphosis of C2-C7 angle ≤ -10° at the final follow-up period, respectively. Among the static and dynamic parameters of the cervical spine, greater cervical kyphosis during flexion (fC2-C7 angle) demonstrated the best discrimination between these two cohorts, with an optimal cutoff value of -27.5°. Meanwhile, greater gap range of motion (gROM = flexion ROM - extension ROM ) had the highest ability to predict a loss of ≥ 10° in C2-C7 angle after CLP, with an optimal cutoff value of 28.5°. This study suggests that in patients with CSM, fC2-C7 angle ≤ -25° on baseline radiographs is a potential risk for kyphotic deformity after CLP. In clinical practice, the patients with this criterion (fC2-C7 angle ≤ -25°) along with gROM ≥ 30° are at high risk of developing significant kyphotic deformity after CLP., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Study Design: A retrospective study., Objective: To verify the pathophysiology of dysphagia during the acute postoperative phase of anterior cervical surgery and to identify its predictive features, using ultrasonographic (US) examination for upper esophageal sphincter (UES)., Summary of Background Data: There are no clinical studies investigating dysphagia after anterior cervical surgery, using US examination for UES., Materials and Methods: We enrolled patients who underwent anterior cervical spine surgery between August 2018 and March 2022. Dysphagia was evaluated using the Eating Assessment Tool-10 (EAT-10) questionnaires. The US examination was performed preoperatively and 2 weeks postoperatively. Three US parameters for morphologic measurements (outer diameter, inner diameter, and muscle thickness) and 4 for functional measurements (displacement, time to relax, passing duration, and time to contract) were assessed. To verify the pathophysiology of postoperative dysphagia, we examined the change in the ratios of US parameters (=US parameter 2 weeks postoperatively /US parameter at baseline ) and the existence of significant correlations with change in the EAT-10 score (=EAT-10 2 weeks postoperatively -EAT-10 at baseline ). To identify the predictive features, the baseline US parameters were compared between dysphagia (+) and dysphagia (-) groups., Results: A total of 46 patients (mean age, 61.3 y; 78.3% male) were included for analysis. A greater increase of the EAT-10 score after surgery was positively correlated with change ratios of the muscle thickness and time to contract and negatively with change ratio of the inner diameter. The dysphagia (+) group exhibited significantly greater inner diameter and smaller muscle thickness at baseline than the dysphagia (-) group., Conclusion: Dysphagia during the acute postoperative phase of anterior cervical surgery is caused by the physical narrowing of the inner lumen due to muscle thickening of the UES and sphincter contractile dysfunction. In addition, a baseline UES morphology characterized by a greater inner diameter and a thinner muscle layer is predictive of postoperative dysphagia., Competing Interests: The authors declare no conflict of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Airway complications that occur after anterior cervical spine surgery pose a life-threatening risk, which encompasses complications including prolonged intubation, unplanned reintubation, and/or necessity of tracheostomy. The present study aimed to identify the surgical risks associated with postoperative airway complications in neurosurgical training institutes. A retrospective, multicenter, observational review of data from 365 patients, who underwent anterior cervical spine surgery between 2018 and 2022, at three such institutes was carried out. Postoperative airway complication was defined as either the need for prolonged intubation on the day of surgery or the need for unplanned reintubation. The perioperative medical information was obtained from their medical records. The average age of the cohort was over 60 years, with males comprising approximately 70%. Almost all surgeries predominantly involved anterior cervical discectomy and fusion or anterior cervical corpectomy and fusion, with most surgeries occurring at the level of C5/6. In total, 363 of 365 patients (99.5%) were extubated immediately after surgery, and the remaining two patients were kept under intubation because of the risk of airway complications. Of the 363 patients who underwent extubation immediately after surgery, two (0.55%) required reintubation because of postoperative airway complications. Patients who experienced airway complications were notably older and exhibited a significantly lower body mass index. The results of this study suggested that older and frailer individuals are at an elevated risk for postoperative airway complications, with immediate postoperative extubation generally being safe but requiring careful judgment in specific cases.

Study Design: Basic in vivo research., Objectives: The aim of this study was to establish an animal model that is appropriate for analyzing the mechanisms of C5 palsy (C5P) and to clarify the structural and functional alterations of cervical roots following posterior decompression., Summary of Background Data: Although C5P is one of the major complications of cervical surgery, the exact pathogenesis of C5P remains unclear partly because of the lack of an appropriate animal model. Tethering of the cervical roots due to posterior cord shift following posterior decompression is thought to be one of the possible factors that cause C5P., Methods: Twenty-eight Sprague-Dawley rats were divided into Group L (cervical laminectomy, N = 18) or Group S (sham surgery, N = 10) and examined up to postoperative day 14 (PO14). Posterior cord shift and the length of the anterior rootlets were quantified by computed tomography-myelogram images. Motor evoked potential (MEP) of the deltoid (C5, 6 innervated) and triceps brachii (C7-T1 innervated), mechanical allodynia, and grip strength of the forepaw (C7-T1 regulated) were measured., Results: All anterior rootlets were elongated as the cord gradually shifted posteriorly postoperatively. The elongation rate of the C6 anterior rootlets was the highest (142% at PO14). The MEP latency of the deltoid was significantly delayed throughout all postoperative time points. However, significant delay in the latency of the triceps brachii was observed only on postoperative day 10. The withdrawal threshold of the forepaw did not change; grip strength of the forelimb decreased at PO14., Conclusion: This model was thought to be appropriate for analyzing the pathogenesis of C5P since our findings were comparable to the clinical course of C5P subsequent to posterior cervical decompression. Although a future study for clarifying histological and molecular alterations will be needed, tethering of the anterior rootlets due to posterior cord shift was suggested to be a probable mechanism causing C5P.Level of Evidence: 5., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Many neurological disorders can present similar symptomatology to degenerative cervical myelopathy (DCM) or myeloradiculopathy (DCMR). Therefore, to avoid misdiagnosis, it is important to recognise the differential diagnosis, which has been well described in previous literature. Additionally, DCM or DCMR can also coexist with other diseases that overlap some of its clinical manifestations, which may be overlooked before cervical surgery. Nevertheless, few studies have addressed this clinical situation. In clinical practice, the diagnosis of coexisting disease with DCM or DCMR would be typically made when some symptoms persist without improvement after cervical surgery. To inform the patients of this possibility preoperatively and arrive at the early diagnosis during the postoperative period, some knowledge of the possible coexisting diseases would be necessary. In this report, we reviewed 230 patients who underwent surgery for DCM or DCMR in an academic centre to examine the prevalence and kind of underlying disease that was overlooked preoperatively. The coexisting diseases relevant to their baseline symptoms were diagnosed only after cervical surgery in three patients (1.3%) and included amyotrophic lateral sclerosis, lung cancer and polymyalgia rheumatica. The overlapping symptoms were gait difficulty, scapular pain and neck pain, respectively. Surgeons should recognise that the coexisting disease with DCM or DCMR may be overlooked before cervical surgery because of overlapping symptomatology, although its prevalence is not certainly high. Further, when the specific symptom persisted without improvement after surgery for DCM or DCMR, the patient should be comprehensively examined, considering diverse pathological conditions, not only neurological disorders., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Purpose: The first purpose of this study is to confirm whether the spinal cord and the surrounding tissues can be visualized clearly after laminoplasty using percutaneous ultrasonography. And second purpose is to evaluate the changes in the status of the spinal cord over time., Methods: Fifty patients who underwent cervical laminoplasty with suture anchors were evaluated using intraoperative ultrasonography and postoperative (1 week, 2 weeks, 3 months, 6 months, and 1 year) percutaneous ultrasonography. We classified the decompression status of the spinal cord into three grades and the pattern of the spinal cord pulsation into six categories. Clinical outcomes were evaluated using the Japanese Orthopaedic Association Score for cervical myelopathy, and the recovery rate was calculated., Results: In all cases and all periods, we could observe the status of the spinal cord using percutaneous ultrasonography after cervical laminoplasty. The decompression status of the spinal cord improved until 3 months postoperatively, and the clinical outcomes improved up to 6 months postoperatively. Although the pulsation pattern of the spinal cord varied in each individual and in each period, spinal pulsation itself was observed in all cases and all periods, except one, when an epidural hematoma caused quadriplegia and a revision surgery was needed. Decompression status and pulsation pattern of the spinal cord were not associated with clinical outcomes as far as pulsation was observed., Conclusions: Percutaneous ultrasonography was very useful method to evaluate the postoperative status of the spinal cord, particularly in the diagnosis of the postoperative epidural hematoma. These slides can be retrieved under Electronic Supplementary Material.

OBJECTIVE The objective of this study was to identify the risk factors of anterior bone loss (ABL) in cervical disc arthroplasty (CDA) and the subsequent effect of this phenomenon. METHODS The authors performed a retrospective radiological review of 185 patients with a minimum 5-year follow-up after CDA (using Bryan, Discocerv, Mobi-C, or Baguera C). Postoperative radiographs were examined and compared to the initial postoperative films to determine the percentage of ABL. The relationship of ABL to potential risk factors was analyzed. RESULTS Complete radiological assessment was available in 145 patients with 193 CDRs and 383 endplates (average age 45 years, range 25-65 years, 54% women). ABL was identified in 63.7% of CDRs (48.7% mild, 11.9% moderate, 3.1% severe). Age (p = 0.770), sex (p = 0.200), postoperative alignment (p = 0.330), midflexion point (p = 0.509), maximal flexion (p = 0.080), and extension (p = 0.717) did not relate to ABL. There was no significant difference in the rate of severe ABL between implants. Multilevel surgery conferred an increased risk of any and severe ABL (p = 0.013 for both). The upper endplate, defined as superior to the CDA, was more commonly involved (p = 0.008), but there was no significant difference whether the endplate was between or not between implants (p = 0.226). The development of ABL did not affect the long-term range of movement (ROM) of the CDA, but did increase the overall risk of autofusion. ABL was not associated with pain or functional deficits. No patients required a reoperation or revision of their implant during the course of this study, and there were no cases of progressive ABL beyond the first year. CONCLUSIONS ABL is common in all implant types assessed, although most is mild. Age, sex, postoperative alignment, ROM, and midflexion point do not relate to this phenomenon. However, the greater the number of levels operated, the higher the risk of developing ABL. The development of ABL has no long-term effect on the mechanical functioning of the disc or necessity for revision surgery, although it may increase the rate of autofusion.

Purpose: We aimed to investigate the clinical performance of the constructs of double-door cervical laminoplasty with suture anchors by examining bony fusion at the hinges and lamina closure., Methods: We retrospectively analysed computed tomography (CT) scans obtained preoperatively, immediately after the operation, and at follow-up of patients who underwent cervical laminoplasty using suture anchors. Hinge fracture, bony healing at the hinges, suture anchor failure, and the lamina angle (LA) were evaluated using CT. Lamina closure was defined as an LA <55° at follow-up., Results: A total of 226 laminae and hinges from 37 patients were evaluated. CT scans immediately after the operation revealed that 13 laminae (5.8 %) were fractured, one of which collapsed into the spinal canal. Bony fusion at an average of 12.7 months after the operation was noted at 222 hinges (98.2 %), which was not affected by hinge fracture. One dislodged suture anchor was identified. The mean LAs were 34.4 ± 4.2° preoperatively, 87.4 ± 12.3° immediately after the operation, and 82.5 ± 12.9° at follow-up. At follow-up, four cases of lamina closure were identified (1.8 %), and the closure rate was significantly higher at C3 than at the other levels, although it was not affected by age, sex, causative disease, cervical alignment, suture anchor use, and hinge fracture., Conclusions: The constructs of double-door cervical laminoplasty with suture anchors are stable with a high rate of fusion at the hinges. However, if the procedure is performed at C3, special modifications should be made to avoid lamina closure.