Clinically significant radiographic parameter for thoracic myelopathy caused by ossification of the ligamentum flavum.

PURPOSE: To investigate radiographic parameters to improve the accuracy of radiologic diagnosis for ossification of ligamentum flavum (OLF)-induced thoracic myelopathy and thereby establish a useful diagnostic method for identifying the responsible segment. METHODS: We classified 101 patients who underwent surgical treatment for OLF-induced thoracic myelopathy as the myelopathy group and 102 patients who had incidental OLF and were hospitalized with compression fracture as the non-myelopathy group between January 2009 and December 2016. We measured the thickness of OLF (TOLF), cross-sectional area of OLF (AOLF), anteroposterior canal diameter, and the ratio of each of these parameters. RESULTS: Most OLF cases with lateral-type axial morphology were in the non-myelopathy group and most with fused and tuberous type in the myelopathy group. Most grade-I and grade-II cases were also in the non-myelopathy group, whereas grade-IV cases were mostly observed in the myelopathy group. The AOLF ratio was found to be the best radiologic parameter. The optimal cutoff point of the AOLF ratio was 33.00%, with 87.1% sensitivity and 87.3% specificity. The AOLF ratio was significantly correlated with preoperative neurological status. CONCLUSIONS: An AOLF ratio greater than 33% is the most accurate diagnostic indicator of OLF-induced thoracic myelopathy. In cases of multiple-segment OLF, confirmation of cord signal change on MRI and an AOLF measurement will help determine the responsible segment. AOLF measurement will also improve the accuracy of diagnosis of OLF-induced thoracic myelopathy in cases of grade III or extended-type axial morphology. These slides can be retrieved under Electronic Supplementary Material.

Importance of the preoperative cross-sectional area of the semispinalis cervicis as a risk factor for loss of lordosis after laminoplasty in patients with cervical spondylotic myelopathy.

PURPOSE: To investigate the effect of the preoperative cross-sectional area (CSA) of the semispinalis cervicis on postoperative loss of cervical lordosis (LCL) after laminoplasty. METHODS: A total of 144 patients who met the inclusion criteria between January 1999 and December 2015 were enrolled. Radiographic assessments were performed to evaluate the T1 slope, C2-7 sagittal vertical axis (SVA), cephalad vertebral level undergoing laminoplasty (CVLL), preoperative C2-7 Cobb angle, and preoperative CSA of the semispinalis cervicis. RESULTS: The T1 slope and the summation of the CSAs (SCSA) at each level of the semispinalis cervicis correlated with LCL, whereas the C2-7 SVA, CVLL, and preoperative C2-7 Cobb angle did not. Multiple regression analysis demonstrated that a high T1 slope and a low SCSA of the semispinalis cervicis were associated with LCL after laminoplasty in patients with cervical spondylotic myelopathy (CSM). The CSA of the semispinalis cervicis at the C6 level had the greatest association with LCL, which suddenly decreased with a LCL of 10°. The best cutoff point of the CSA of the semispinalis cervicis at the C6 level, which predicts LCL > 10°, was 154.5 mm2 (sensitivity 74.3%; specificity 71.6%; area under the curve 0.828; 95% confidence interval 0.761-0.895). CONCLUSION: Preoperative SCSA of the semispinalis cervicis was a risk factor for LCL after laminoplasty. Spine surgeons should evaluate semispinalis cervicis muscularity at the C6 level when planning laminoplasty for patients with CSM. These slides can be retrieved under Electronic Supplementary Material.

Analysis of the Risk Factors Associated with Prolonged Intubation or Reintubation after Anterior Cervical Spine Surgery.

BACKGROUND: Standardized postoperative airway management is essential for patients undergoing anterior cervical spine surgery (ACSS). The paucity of clinical series evaluating these airway complications after ACSS has been resulted in a significant limitation in statistical analyses. METHODS: A retrospective cohort study was performed regarding airway distress (intubation for more than 24 hours or unplanned reintubation within 7 days of operation) developed after ACSS. If prevertebral soft tissue swelling was evident after the operation, patients were managed with prolonged intubation (longer than 24 hours). Preoperative and intraoperative patient data, and postoperative outcome (time to extubation and reintubation) were analyzed. RESULTS: Between 2008 and 2016, a total of 400 ACSS were performed. Of them, 389 patients (97.25%) extubated within 24 hours of surgery without airway complication, but 11 patients (2.75%) showed postoperative airway compromise; 7 patients (1.75%) needed prolonged intubation, while 4 patients (1.00%) required unplanned reintubation. The mean time for extubation were 2.75 hours (range: 0-23 hours) and 50.55 hours (range: 0-250 hours), respectively. Age (P = 0.015), diabetes mellitus (P = 0.003), operative time longer than 5 hours (P = 0.048), and estimated blood loss (EBL) greater than 300 mL (P = 0.042) were associated with prolonged intubation or reintubation. In prolonged intubation group, all patients showed no airway distress after extubation. CONCLUSION: In ACSS, postoperative airway compromise is related to both patients and operative factors. We recommend a prolonged intubation for patients who are exposed to these risk factors to perform a safe and effective extubation.

Clinical analysis of C5 palsy after cervical decompression surgery: relationship between recovery duration and clinical and radiological factors.

BACKGROUND: Postoperative C5 palsy is a widely known complication of cervical decompression surgery. Many studies have focused on its etiology and factors affecting it. However, no study to date has evaluated the association between the clinical outcome and recovery duration of post-operative C5 palsy. We evaluated this in our current report. METHODS: A retrospective analysis was conducted for 710 consecutive degenerative cervical spine decompression surgeries performed in a single institution. We included all patients who underwent any type of surgical procedure for cervical spinal stenosis, ossification of posterior longitudinal ligament (OPLL), or cervical spondylotic myelopathy (CSM). Demographic, radiologic, clinical information was recorded. Finally, correlation analysis was conducted to identify demographic, radiologic, or clinical factors related with recovery duration (within or after 6 months). RESULTS: The incident rate of postoperative C5 palsy was 5.1 % (36/710 cases). Analysis of recovery duration revealed that 18 patients had recovered within 6 months and 33 (91.7 %) within 2 years, whilst 3 individuals (8.3 %) had not fully recovered within the follow-up period. Factors related to longer recovery (>6 months) included motor grade ≤2 (p < 0.001), presence of multi-segment paresis involving more than the C5 root (p = 0.002), loss of somatic sensation with pain (p = 0.008), and the degree of posterior spinal cord shifting (p = 0.040). Furthermore, multivariate analysis revealed that motor grade ≤2 (p = 0.010) had a significant effect on a recovery duration beyond 6 months. CONCLUSIONS: A motor grade ≤2, the presence of multi-segment paresis involving more than the C5 root, the loss of somatic sensation with pain, and the degree of posterior spinal cord shifting significantly influence whether the duration of recovery from postoperative C5 palsy will take longer than 6 months.

Prognostic factor analysis after surgical decompression and stabilization for cervical spinal-cord injury.

INTRODUCTION: Several studies have demonstrated the role of decompression surgery in preventing secondary injury and improving the neurological outcome after spinal cord injury (SCI). We retrospectively analyzed the prognostic factors affecting the outcomes of decompression surgery in patients with SCI. METHODS: We performed one-level decompression and fusion surgery on 73 patients with cervical SCI. We classified all patients based on their interval to decompression, sex, age, surgical level, presence of high signal intensity, American Spinal Injury Association Impairment scale (AIS) before surgery, blood pressure at admission, the amount of cord compression, surgical time, estimated blood loss during surgery, and steroid use. We considered an improvement to have occurred if the patient showed an AIS improvement of ≥1 grade. RESULTS: Among the 73 patients with SCI we analyzed, 27 and 35 showed ≥1 grade of AIS improvement immediately and 3 months after surgery, respectively. Using multivariate analysis, the mean arterial blood pressure (MAP) was a significant prognostic factor affecting recovery in the SCI patients during the immediate post-operative period. In the late recovery period at 3 months after surgery, the AIS before surgery and the MAP were significant prognostic factors affecting recovery. CONCLUSIONS: Prognostic factors for AIS improvement include the initial neurological status before surgery and hemodynamic MAP at admission. The interval between decompression surgery and trauma does not affect the neurological outcome.

Symptomatic adjacent segment degeneration at the L3-4 level after fusion surgery at the L4-5 level: evaluation of the risk factors and 10-year incidence.

PURPOSE: There have been few studies on revision surgery for clinically symptomatic adjacent segment degeneration (CASD). We aimed to find the incidence of revision surgery due to CASD and to analyze the factors that affected CASD at the L3-4 level after L4-5 or L4-5-S1 level fusion surgery over a long-term follow-up period. METHODS: Between January 2001 and October 2009, fusion surgeries were performed on 401 patients with spondylolisthesis at the L4-5 or L4-5-S1 level; 378 patients were followed up for a minimum of 2 years. We assessed CASD-free survival using Kaplan-Meier survival analysis. We also analyzed factors affecting the development of CASD, including sex, age, pelvic incidence, overall lordosis, segmental lordosis, lamina inclination angle, facet tropism, and the extent of disc and facet degeneration. Isthmic spondylolisthesis treated using total laminectomy or degenerative spondylolisthesis treated using subtotal laminectomy and interbody fusion (IBF) or posterolateral fusion (PLF) were also included in the risk factor analysis. The difference in disc height before and after initial surgery was also analyzed, as was inclusion of the sacrum in the fusion level. RESULTS: Fusion extension surgery was performed on 33 of these patients due to CASD at the L3-4 level during the follow-up period. Kaplan-Meier survival analysis indicated 3-, 5-, and 10-year disease-free survival rates of 99.20, 96.71, and 76.93 %. Statistically significant factors affecting CASD included old age, low overall lordosis, low segmental lordosis, progression of facet degeneration, total laminectomy-treated isthmic spondylolisthesis, and PLF-alone rather than IBF alone or IBF + PLF. CONCLUSION: We determined six significant factors affecting CASD development. Among these risk factors, facet degeneration, isthmic-type spondylolisthesis, and the type of fusion show higher hazard ratios and seem to be clinically more relevant than the other three factors (age, overall lordosis, and segmental lordosis).

Surgical strategies for removal of intra- and extraforaminal dumbbell-shaped schwannomas in the subaxial cervical spine.

PURPOSE: Spinal dumbbell-shaped schwannoma is common neoplasm, usually occurring in the cervical spine. Posterior or anterolateral approaches are frequently used to remove this benign tumor. We analyzed how much amount of tumor could be possible to be totally removed with posterior approach. METHOD: Surgery was performed on 41 cases of cervical, dumbbell-shaped subaxial schwannomas with both intra- and extraforaminal involvement. The same surgeon performed all the procedures. Mean follow-up was 42.5 months (24-108 months). A combined anterolateral and posterior approach was used if the extraforaminal tumor was larger than 10 mm. A posterior approach and unilateral facet removal were used if it was smaller than 10 mm. We performed MRI and serial dynamic X-rays for postoperative 2 years. RESULTS: We used the posterior approach with facetectomy in 35 cases and the combined approach in six. Complete removal was achieved with the combined approach in all six, and with the posterior approach in 28 of 35 cases. With the posterior approach, the extraforaminal dimension of totally resected tumors ranged from 3 to 5.4 mm. Subtotal resection was limited to extraforaminal tumors larger than 5.7 mm. On follow-up, instability on dynamic X-ray was not observed before 24 months in any patient after unilateral facetectomy. CONCLUSION: Total removal of intra- and extraforaminal cervical subaxial schwannomas could be possible using a posterior approach with facet removal if the size of extraforaminal tumor was less than 5.4 mm.

Progression of lumbar spinal stenosis is influenced by polymorphism of thrombospondin 2 gene in the Korean population.

PURPOSE: The aim of this study is to determine the contribution of thrombospondin 2 (THBS2) polymorphisms to the development and progression of lumbar spinal stenosis (LSS) in the Korean population. METHODS: We studied 148 symptomatic patients with radiographically proven LSS and 157 volunteers with no history of back problems from our institution. Magnetic resonance images were obtained for all the patients and controls. Quantitative image evaluation for LSS was performed to evaluate the severity of LSS. All patients and controls were genotyped for THBS2 allele variations using a polymerase chain reaction-based technique. RESULTS: We found no causal single nucleotide polymorphism (SNPs) in THBS2 that were significantly associated with LSS. Two SNPs (rs6422747, rs6422748) were over-represented in controls [P = 0.042, odds ratio [OR] = 0.55 and P = 0.042, OR = 0.55, respectively]. Haplotype analysis showed that the ''AGAGACG'' haplotype (HAP4) and ''AAGGACG'' haplotype (HAP5) were over-represented in severe LSS patients (P = 0.0147, OR = 2.02 and P = 0.0137, OR = 2.48, respectively). In addition, the ''AAAGGGG'' haplotype (HAP1) was over-represented in controls (P = 0.0068, OR = 0.30). CONCLUSIONS: Although no SNPs in THBS2 were associated with LSS, haplotypes (HAP4 and HAP5) were significantly associated with progression of LSS in the Korean population, whereas another haplotype (HAP1) may play a protective role against LSS development.

Mid-term follow-up of clinical and radiologic outcomes in cervical total disk replacement (Mobi-C): incidence of heterotopic ossification and risk factors.

INTRODUCTION: Cervical arthroplasty has been shown to have successful, short-term and long-term radiologic and clinical outcomes. The incidence of and predisposing factors for heterotopic ossification (HO) have not been determined. We retrospectively assessed the intermediate-term clinical and radiologic outcomes, especially the incidence of HO and its risk factors. METHODS: Our patient population consisted of 75 patients (85 levels) with cervical disk herniation. Mean follow-up was 40 months, with a minimum follow-up of 24 months. The numeric rating scale scores of neck and arm pain, the neck disability index, and Odom criteria were measured preoperatively and at 24 months postoperatively. Cervical overall lordosis, segmental lordosis, and range of motion at the operative level were evaluated immediately after surgery and at 1, 3, 6, 12, and 24 months postoperatively. The incidence and location of HO were evaluated at 12 and 24 months postoperatively. Univariate and multivariate logistic regression analyses were performed to determine the risk factors for HO. RESULTS: The mean numeric rating scale scores and neck disability index scores decreased significantly over 24 months. According to Odom criteria, this represented an overall success rate of 86.7%. Mean segmental lordosis and motion increased and then decreased until 24 months. HO occurred in 67 levels at 12 months postoperatively, increasing to 80 levels at 24 months. The multivariate logistic regression test showed a statistically significant difference when using a different surgical technique (P = 0.049). CONCLUSIONS: Intermediate follow-up of cervical arthroplasty showed good clinical outcomes, although there was a trend toward reduction in alignment and motion at 24 months. The overall HO occurrence was 94.1% at 24 months. In our study, the most important factor affecting HO was the different surgical techniques.

A comparison of unilateral laminectomy with bilateral decompression and fusion surgery in the treatment of grade I lumbar degenerative spondylolisthesis.

BACKGROUND: Although unilateral laminectomy and bilateral decompression (ULBD) is effective in the treatment of degenerative spondylolisthesis (DSPL), few reports have compared the outcomes of ULBD and instrumented fusion for the treatment of DSPL. We describe here the clinical and radiological outcomes of ULBD and instrumented fusion surgery for the treatment of DSPL after a minimum 3-year follow-up. METHODS: We retrospectively analyzed the outcomes of 47 DSPL patients with radicular pain who underwent ULBD or instrumented fusion between January 2005 and December 2007. Clinical outcomes were assessed using the numeric rating scale (NRS) for back and leg pain, the Oswestry Disability Index (ODI), and Short Form-36 Health Survey (SF-36). Radiological outcomes of ULBD were analyzed by determining changes in slippage, disc height translation, and angular difference on simple and dynamic X-rays. RESULTS: The mean NRS of back pain showed a significantly greater decrease in the fusion than the ULBD group, whereas the mean NRS of leg pain, mean ODI, and mean physical component summary and mental component summary of the SF-36 decreased similarly in the ULBD and fusion groups. Radiologically, the ULBD group showed a 2.1 ± 3.10% change in mean slippage, a 0.15 ± 1.58 mm change in mean translation, a -0.91 ± 4.48° change in mean angular difference, and a -1.83 ± 1.69 mm change in mean disc height. In the ULBD group, three patients had residual pain and three had recurrent pain. In comparison, no patient in the fusion group reported residual pain, whereas five patients experienced recurrent radicular pain caused by adjacent segmental disease. CONCLUSIONS: Our findings suggest that ULBD is the recommendable procedure for the treatment of patients with grade I DSPL who have mainly radicular pain. Although the two groups showed similar clinical outcomes overall, radiological degeneration was not as serious after ULBD treatment. In our analysis, foraminal stenosis is a contraindication for ULBD in the treatment of grade I DSPL.

Evaluation of efficacy and safety of fentanyl transdermal patch (Durogesic D-TRANS) in chronic pain.

PURPOSE: Opioids are used in controlling several types of pain. This study was designed to evaluate the efficacy and safety of the fentanyl transdermal patch-type system (Durogesic® D-TRANS). METHODS: Patients who complained of chronic moderate to severe pain were enrolled. Administration dosages of fentanyl patch started from 12.5 µg/h and could be increased by 12.5 µg/h or 25 µg/h, if the average pain score of 4 or higher occurred within 72 h. The total administration period was 12 weeks. The type, location, characteristics, and duration of pain were evaluated. Also, on day 0, weeks of 4, 8, and 12, the physician's assessment of pain intensity, the patient's assessment of pain intensity, the assessment of impact of pain on functions, and the assessment of the impact of pain on sleep were assessed. In addition, side effects were evaluated during the study duration. RESULTS: A total of 65 cases were enrolled, and the final evaluated cases were 41. Before treatment, the average physician's assessment of pain intensity was 6.70 ± 1.41, and the average patient's assessment of pain intensity was 7.02 ± 1.63. In the final visit, the average physician's assessment of pain intensity was 2.58 ± 1.72, and the average patient's assessment of pain intensity was 2.86 ± 1.78. CONCLUSIONS: This prospective study shows that the fentanyl patch is effective in alleviating moderate to severe chronic noncancer pain including neuropathic pain down to mild pain. Therefore, the fentanyl patch should be considered before other invasive intervention procedures in chronic moderate to severe noncancer pain.

Intraoperative Monitoring for Cauda Equina Tumors: Surgical Outcomes and Neurophysiological Data Accrued Over 10 Years.

OBJECTIVE: Cauda equina tumors affect the peripheral nervous system, and the validities of triggered electromyogram (tEMG) and intraoperative neurophysiologic monitoring (IOM) are unclear. We sought to evaluate the accuracy and relevance of tEMG combined with IOM during cauda equina tumor resection. METHODS: Between 2008 and 2018, an experienced surgeon performed cauda equina tumor resections using tEMG at a single institution. A cauda equina tumor was defined as an intradural-extramedullary or intradural-extradural tumor at the level of L2 or lower. The clinical presentation, extent of resection, pathology, recurrence, postoperative neurological outcomes, and intraoperative tEMG mapping and IOM data were retrospectively analyzed. RESULTS: One hundred three patients who underwent intraoperative tEMG were included; 38 underwent only tEMG (tEMG-only group), and 65 underwent a combination of tEMG and multimodal IOM (MIOM group). There were no significant differences between the neurologic outcomes, extents of resection, or recurrence rates of the 2 groups. No significant therapeutic benefit was observed; however, the accuracy of intraoperative predetection improved with the combination of IOM and tEMG (accuracy: tEMG-only group, 86.8%; MIOM group, 92.3%). When the involved rootlet was resected despite the positive tEMG result, motor function worsened in 3 of 8 cases. The sensitivity and specificity of tEMG were 37.5% and 94.7%, respectively. CONCLUSION: tEMG is an essential adjunctive surgical tool for deciding on and planning for rootlet resection. If the tEMG finding is negative, complete resection, involving the rootlet, may be safe. The accuracy may be further improved by using a combination of tEMG and IOM.

Reliability of Early Ambulation after Intradural Spine Surgery : Risk Factors and a Preventive Method for Cerebrospinal Fluid Leak Related Complications.

OBJECTIVE: Cerebrospinal fluid leakage related complications (CLC) occasionally occur after intradural spinal surgery. We sought to investigate the effectiveness of early ambulation after intradural spinal surgery and analyze the risk factors for CLC. METHODS: For this retrospective cohort study, we enrolled 314 patients who underwent intradural spinal surgery at a single institution. The early group contained 79 patients who started ambulation after 1 day of bedrest without position restrictions, while the late group consisted of 235 patients who started ambulation after at least 3 days of bed rest and were limited to the prone position after surgery. In the early group, Prolene 6-0 was used as the dura suture material, while black silk 5-0 was used as the dura suture material in the late group. RESULTS: The overall incidence rate of CLC was 10.8%. Significant differences between the early and late groups were identified in the rate of CLC (2.5% vs. 13.6%), surgical repair required (1.3% vs. 7.7%), and length of hospital stay (2.99 vs. 9.29 days) (p<0.05). Logistic regression analysis revealed that CLC was associated with practices specific to the late group (p=0.011) and the revision surgery (p=0.022). CONCLUSION: Using Prolene 6-0 as a dura suture material for intradural spinal surgery resulted in lower CLC rates compared to black silk 5-0 sutures despite a shorter bed rest period. Our findings revealed that suture - needle ratio related to dura defect was the most critical factor for CLC. One-day ambulation after primary dura closure using Prolene 6-0 sutures appears to be a cost-effective and safe strategy for intradural spinal surgery.

Gait analysis for evaluating the relationship between increased signal intensity on t2-weighted magnetic resonance imaging and gait function in cervical spondylotic myelopathy.

OBJECTIVE: To determine relationships between increased signal intensity (ISI) on T2-weighted cervical spine magnetic resonance imaging (MRI) and parameters of gait analysis in patients with cervical spondylotic myelopathy (CSM). DESIGN: Retrospective comparative study. SETTING: Gait analysis laboratory. PARTICIPANTS: Patients (N=36) who undertook cervical laminectomy or laminoplasty because of CSM. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Subjects were evaluated by using the modified Japanese Orthopaedic Association (JOA) scale, the Nurick scale, cervical spine MRI, and gait analysis. Two radiologists classified patients into 3 groups: intense, faint, and no ISI. RESULTS: Relative to patients without ISI, those with ISI showed significantly slower gait speed, longer step time, decreased single-limb support time, increased double-limb support time, and limited range of motion of knee and ankle (P<.05). Increased intensity tended to correlate with poor gait function including slower gait speed, longer step time, decreased single-limb support time, and increased double-limb support time. The modified JOA and Nurick scale did not correlate with ISI. CONCLUSIONS: In patients with CSM who received surgical treatment, more intense ISI on T2-weighted MRI correlated preoperatively with increased difficulties in gait function. Gait analysis may be a useful tool for evaluating gait functions in cervical myelopathy.

Posterior Cervical Muscle-Preserving Interspinous Process Approach and Decompression: More Minimally Invasive and Modified Shiraishi's Selective Laminectomy.

OBJECTIVE: The cervical extensor musculature is important in cases of neck pain and loss of cervical lordosis after laminoplasty. Therefore, various surgical methods have been developed to preserve the muscle during laminoplasty. We have developed a posterior cervical muscle-preserving interspinous process (MIS) approach and decompression method. We have described the operation details and clinical outcomes of selected patients who have undergone this procedure. METHODS: The MIS approach and decompression method were performed in 20 consecutive patients who had only required central decompression for cervical stenosis. This procedure includes an approach to the interspinous space that is similar to Shiraishi's method but includes decompression without fracturing the spina bifida. RESULTS: The patients had no complications and did not require conversion to conventional laminoplasty. The mean operative time and mean blood loss was 53.0 minutes and 63.0 mL per level, respectively, and the mean hospital stay was 4.0 days. The mean preoperative and 3-month postoperative modified Japanese Orthopedic Association scores were 12.6 and 16.2, and the mean preoperative and 3-month postoperative neck disability index scores were 15.4 and 2.5, respectively. The postoperative neck visual analog scale score was 0.8. The mean preoperative and postoperative sagittal vertical axis was 1.6 and 1.8 cm, respectively. The mean loss of lordosis was 1.0°, and the mean cervical range of motion did not change from preoperatively to postoperatively. CONCLUSIONS: The MIS approach and decompression method was less invasive than both conventional laminoplasty and Shiraishi's selective laminectomy. It is a safe and effective minimally invasive technique for central stenosis caused by cervical spondylotic myelopathy.

Combined motor and somatosensory evoked potential monitoring for intramedullary spinal cord tumor surgery: correlation of clinical and neurophysiological data in 17 consecutive procedures.

The primary objective of neurophysiologic monitoring during surgery is to prevent permanent neurological sequelae. We prospectively evaluated whether the combined use of somatosensory- and motor-evoked potential (SEP/MEP) for intramedullary spinal cord tumor (IMSCT) surgery may be beneficial. Combined SEP/MEP monitoring was attempted in 20 consecutive procedures for IMSCT operations. Trains of transcranial electric stimulation over the motor cortex were used to elicit MEPs from limb target muscles. The tibial and median nerves were stimulated to record SEP. The operation was paused or the surgical strategy was modified in every case of significant SEP/MEP changes. Combined SEP/MEP recording was successfully achieved in 17 of 20 (85%) operations. In 3 of 17 operations, SEP and MEP were stable, and all patients remained neurologically intact after surgery. Significant MEP changes were recorded in 12 operations (70%). In 7 of these 12 operations, MEP recovered to some extent after surgical intervention, and these patients showed no neurological changes. In the remaining 5 operations, MEP did not recover and the patients had a transient (n = 2) or a permanent (n = 1) motor deficit. Significant SEP changes with stable MEP were related to a transient hypesthesia. Combined SEP/MEP monitoring provided higher sensitivity, and higher positive and negative predictive value than single-modality techniques. Detection of MEP changes and adjustment of surgical strategy may prevent irreversible pyramidal tract damage.

The Learning Curve of Subaxial Cervical Pedicle Screw Placement: How Can We Avoid Neurovascular Complications in the Initial Period?

BACKGROUND: Despite the biomechanical benefits of subaxial cervical pedicle screw (CPS) placement, possible neurovascular complications, including vertebral artery and nerve root injury, are of great concern. We have demonstrated many times the safety and efficacy of CPS deployments, even when using freehand technology. OBJECTIVE: To analyze the learning curve of CPS placement to determine the number of cases necessary for assuring safe CPS placement and to identify a reasonable accuracy rate. METHODS: From March 2012 to August 2018, a single surgeon performed posterior cervical fusion surgery using CPS placement on 162 consecutive patients. We classified whole surgical periods, 6 years, into 4 periods. We analyzed the screw breach rate, lateral mass screw conversion (LMSC) rate, and reposition rate. We also compared the CPS placement accuracy in the initial 15, 20, and 30 patients with the other 147, 142, and 132 patients, respectively, to assess the number of procedures necessary to reach the learning curve plateau and to identify a reasonable accuracy rate. RESULT: The total number of planned CPS placements was 979. Our learning curve showed that the breach rate plateaus at 3% to 4%. The necessary numbers for safe and accurate CPS placement during learning curve were 30 patients and 170 screws. None of the patients undergoing CPS developed a neurologic or vascular complication. CONCLUSION: By following our 5 safety steps, the steady state for safety and accuracy can be reached without neurovascular complications even in the initial period of the learning curve.

Surgical Treatment of Lumbar Spinal Discal Cyst: Is It Enough to Remove the Cyst Only without Following Discectomy?

Discal cysts are a rare cause of low back pain and radiculopathy with unknown pathophysiologic mechanism. Associated symptoms are difficult to distinguish from those caused by extruded discs and other spinal canal lesions. Most discal cysts are treated surgically, but it is unclear whether the corresponding intervertebral disc should be excised along with cyst. We conducted a retrospective clinical review of 27 patients who underwent discal cyst excision at our institution between 2000 and 2017. The mean follow-up period was 63.6 months. We recorded symptoms, radiographs, operative findings, postoperative complications, and short- and long-term outcomes. Structured outcome assessment was based on Numeric Rating Scale (NRS) for pain intensity, Oswestry disability index, and Macnab classification. All patients underwent partial hemilaminectomy and microscopic cyst resection without discectomy. All patients had preoperative back or leg pain. Other preoperative clinical features included motor weakness, neurogenic intermittent claudication, and cauda equina syndrome. After surgery, NRS scores of back and leg pain decreased. The other symptoms also improved. During long-term follow-up, patients reported no restrictions on daily life activities, and were satisfied with our intervention. There were no cases of cyst recurrence. We conducted a review of the literature on lumbar discal cysts published before January, 2018. Including our cases, 126 patients were described. We compared two surgical modalities-cystectomy with and without discectomy-to elucidate both effectiveness and long-term complications. We found that microsurgical cystectomy without corresponding discectomy is an effective surgical treatment for lumbar discal cysts, and is associated with a low recurrence rate.

Anterior Odontoid Screw Fixation for the Treatment of Type 2 Odontoid Fracture with a Kyphotic Angulation or an Anterior Down-slope: A Technical Note.

Anterior odontoid screw fixation (AOSF) is difficult and challenging to perform in patients with type 2 odontoid fracture with a kyphotic angulation or an anterior down-slope. To demonstrate two surgical techniques to resolve kyphotic angulation or difficult fracture direction issues. Anterior odontoid screw fixation was performed in two patients with type 2 odontoid fracture with a kyphotic angulation or an anterior down-slope. This technique can avoid sternal blocking using a percutaneous vertebroplasty puncture needle, and can reduce the kyphotic angle using a Cobb elevator in patients with type 2 odontoid fractures with a kyphotic angulation or an anterior down-sloped fracture. In both the patients, AOSF was successfully performed and a successful clinical outcome was achieved. The screws were well-maintained with reduced fracture segment and well-preserved, corrected kyphotic angles were achieved, as observed on cervical X-ray 6 months postoperatively. Our technique is a safe and effective method for the treatment of type 2 odontoid fracture with a kyphotic angulation or an anterior down-slope.

Effect of Vertebroplasty at the Upper Instrumented Vertebra and Upper Instrumented Vertebra +1 for Prevention of Proximal Junctional Failure in Adult Spinal Deformity Surgery: A Comparative Matched-Cohort Study.

BACKGROUND: This study aimed to compare radiographic outcomes of adult spinal deformity (ASD) surgery with or without 2-level prophylactic vertebroplasty (PVP) at the uppermost instrumented vertebra (UIV) and the vertebra 1 level proximal to the UIV. METHODS: This retrospective 1:2 matched-cohort comparative study enrolled 2 groups of patients undergoing ASD surgery, including 28 patients with PVP (PVP group) and 56 patients without PVP (non-PVP group), in 3 institutes between 2012 and 2015. The primary outcome measure was the incidence of proximal junctional kyphosis (PJK), proximal junctional failure (PJF), and proximal junctional fracture (PJFX). The secondary outcome measure were radiologic outcomes between PVP segments and non-PVP segments. RESULTS: Between the PVP group and non-PVP group, no significant differences were found in the incidence of PJK (13 [46.4%] vs. 26 [46.4%]; P = 1.000), PJF (11 [39.3%] vs. 18 [32.1%]; P = 0.516), and PJFX (11 [39.3%] vs. 18 [32.1%]; P = 0.516). The number of the PJFX segments was 16 and 33 in PVP segments and non-PVP segments, respectively. Until revision surgery or final follow-up, the PJFX had progressed in 24 non-PVP segments (82.7%), but not in PVP segments. The PJFX progression in all PVP segments stopped near the PVP mass at the final follow-up. Reoperation as a result of PJFX was performed in 1 patient (3.6%) and 8 patients (14.3%) in the PVP and non-PVP groups, respectively. CONCLUSIONS: PVP at UIV and vertebra 1 level proximal to the UIV cannot prevent PJK, PJF, and PJFX; however, it plays a positive role by delaying their progression. Furthermore, PVP tends to lower the reoperation rate after PJFX in ASD surgery.