Which patients do we need to consider augmentation of muscle active potentials regarding transcranial electrical stimulation motor-evoked potentials monitoring before spine surgery?

BACKGROUND CONTEXT: Transcranial electrical stimulation motor-evoked potentials (Tc-MEPs) are the current trend and are important in preventing intraoperative neurological deficits. Post-tetanic Tc-MEPs (p-MEP) can augment the amplitudes of compound muscle active potentials (CMAPs), especially in the case of insufficient conventional Tc-MEPs (c-MEP). PURPOSE: To retrospectively investigate pre- and intraoperative factors necessitating p-MEP monitoring and to examine changes in the success rates of baseline Tc-MEP monitoring before and after tetanic stimulation in patients with such factors. STUDY DESIGN: Retrospective observational study. PATIENT SAMPLE: Patients (n=184) who underwent spinal surgery with Tc-MEP monitoring in our department between August 2020 and July 2022. OUTCOME MEASURES: Manual muscle testing (MMT) scores were calculated to identify patients with preoperative motor deficits. c-MEP and p-MEP amplitudes were recorded from the defined muscles. METHODS: We compared preoperative and intraoperative factors between the c-MEP and p-MEP groups (study 1). In cases where the factors were identified, we investigated the success rate of the baseline MEP measurement of each muscle before and after tetanic stimulation (study 2). RESULTS: One hundred fifty-seven patients were included. Of those, 87 showed sufficient CMAPs with c-MEP. Meanwhile, 70 needed p-MEP because of insufficient CMAPs. In univariate analysis, cervical/thoracic surgery (p<.001), preoperative MMT 3 or below (p=.009), shorter duration of illness (p=.037), previous cerebrovascular disease (p=.014), and dialysis (p=.031) were significantly associated with p-MEP group. Preoperative MMT 3 or below was the only factor requiring p-MEP (odds ratio, 3.34; 95% confidence interval, 1.28-8.73, p=.014) in multivariate analysis. In the p-MEP group, 24 patients had preoperative motor deficits; 16 patients with complete data were included in the analysis (study 2). The success rates of MEP monitoring before and after tetanic stimulation of the entire lower-extremity muscles were 42.7 and 57.3%, respectively (p<.001). The success rates for each muscle before and after tetanic stimulation were abductor pollicis brevis: 81.3% and 96.9%, tibialis anterior: 34.4% and 50.0%, gastrocnemius: 25% and 40.6%, and abductor hallucis: 68.8% and 81.3%, respectively. No significant differences were observed in success rates for any of the muscles. CONCLUSIONS: Patients with preoperative MMT 3 or below highly needed p-MEP. The success rate of baseline MEP monitoring increased with tetanic stimulation, even in patients with preoperative motor deficits. We believe that p-MEP monitoring can result in reliable CMAP recording, especially in cases of preoperative motor deficits with MMT scores of 3 or below.

Anterior Placement of Cages in Posterior Lumbar Interbody Fusion for Obtaining Good Lumbar Lordosis Formation.

Introduction: Posterior lumbar interbody fusion (PLIF) is a common treatment for nerve root disease associated with lumbar foraminal stenosis or lumbar spondylolisthesis. At our institution, PLIF is usually performed with high-angle cages and posterior column osteotomy (PLIF with HAP). However, not all patients achieve sufficient segmental lumbar lordosis (SLL). This study determined whether the location of PLIF cages affect local lumbar lordosis formation. Methods: A total of 59 patients who underwent L4/5 PLIF with HAP at our hospital, using the same titanium control cage model, were enrolled in this cohort study. The mean ratio of the distance from the posterior edge of the cage to the posterior wall of the vertebral body/vertebral length (RDCV) immediately after surgery was 16.5%. The patients were divided into two groups according to RDCV <16.5% (group P) and ≥16.5% (group G). The preoperative and 6-month postoperative slip rate (%slip), SLL, local disk angle (LDA), ratio of disk height/vertebral height (RDV), 6-month postoperative RDCV, ratio of cage length/vertebral length (RCVL), and ratio of posterior disk height/anterior disk height at the fixed level (RPA) were evaluated via simple lumbar spine X-ray. The preoperative and 6-month postoperative Japanese Orthopedic Association (JOA) and low back pain visual analog scale (VAS) scores were also evaluated. Results: Groups G and P included 31 and 28 patients, respectively. The preoperative %slip, SLL, LDA, RDV, JOA score, and low back pain VAS score were not significantly different between the groups. In groups G and P, 6-month postoperative %slip, SLL, LDA, RDV, RDCV, RCVL, and RPA were 3.3% and 7.9%, 18.6° and 15.4°, 9.7° and 8.0°, 36.6% and 40.3%, 21.1% and 10.1%, 71.4% and 77.0%, and 56.1% and 67.7%, respectively. The 6-month postoperative SLL, LDA, RDV, RDCV, RCVL, and RPA significantly differed (p=0.03, 0.02, 0.02, <0.001, <0.001, and <0.001, respectively). Conclusions: Anterior PLIF cage placement relative to the vertebral body is necessary for good SLL in PLIF.

Utility of desflurane as an anesthetic in motor-evoked potentials in spine surgery and the facilitating effect in tetanic stimulation of bilateral median nerves.

Although desflurane is a safe and controllable inhalation anesthetic used in spinal surgery, to our knowledge, there have been no reports of successful motor-evoked potential (MEP) recordings under general anesthesia with desflurane alone. A high desflurane concentration may reduce the risk of intraoperative awareness but can also reduce the success of MEP recording. Therefore, we aimed to evaluate the reliability of MEP monitoring and investigate whether tetanic stimulation can augment MEP amplitude under general anesthesia with high-concentration desflurane during spinal surgery. We prospectively evaluated 46 patients who were scheduled to undergo lumbar surgery at a single center between 2018 and 2020. Anesthesia was maintained with an end-tidal concentration of 4% desflurane and remifentanil. Compound muscle action potentials were recorded bilaterally from the abductor pollicis brevis, abductor hallucis, tibialis anterior, gastrocnemius, and quadriceps. For post-tetanic MEPs (p-MEPs), tetanic stimulation was applied to the median nerves (p-MEPm) and tibial nerves (p-MEPt) separately before transcranial stimulation. The average success rates for conventional MEP (c-MEP), p-MEPm, and p-MEPt were 77.9%, 80%, and 79.3%, respectively. The p-MEPm amplitudes were significantly higher than the c-MEP amplitudes in all muscles (P < 0.05), whereas the p-MEPt amplitudes were not significantly different from the c-MEP amplitudes. The MEP recording success rates for the gastrocnemius and quadriceps were inadequate. However, bilateral median nerve tetanic stimulation can effectively augment MEPs safely under general anesthesia with high-concentration desflurane in patients who undergo spinal surgery.

Ultrasound-guided disc pain induction test for diagnosis of discogenic lumbar pain: a cross-sectional study.

BACKGROUND: Several methods can be used to diagnose discogenic pain, but only discoblock can diagnose discogenic pain definitively. This study aimed to examine the usefulness of an ultrasound-guided disc pain induction test for a simple and accurate diagnosis of the culprit lesion. METHODS: We included 41 patients with lumbar pain in whom pain was induced by an ultrasound-guided disc pain induction test. All patients had confirmed pain at L1/2 to L5/S1 based on an ultrasound-guided disc pain induction test and underwent X-ray photography and magnetic resonance imaging. Seventeen patients who required injection due to severe pain underwent discoblock procedures for discs with the most intense pain, and visual analogue scale (VAS) scores were obtained before and after the procedure for these patients. We analysed the association between painful discs and radiological findings. RESULTS: Pain induction was noted in a total of 65 discs, and the pain was induced in 23 patients in only one disc. All patients had disc degeneration of Pfirrmann classification grade 1 or higher, with more significant disc degeneration in painful discs than in painless discs. There was no significant relationship between the presence or absence of pain and Modic type. The average VAS measurements improved significantly from 9.5 (pre-procedure) to 2.5 (post-procedure). These results suggest that the most painful discs were the causes of discogenic lumbar pain. CONCLUSIONS: Our ultrasound-guided disc pain induction test may help diagnose disc degeneration and identify culprit lesions, even when multiple discs exhibit findings of degeneration.

Does a Positive Response to Transforaminal Epidural Steroid Injection Identify Patients Who Can Avoid Surgery for Two Years?

Background: Transforaminal epidural steroid injection (TFESI) is widely used to manage lumbar radiculopathy. In clinical settings, patients often undergo repeated transforaminal epidural injections with or without steroid administration. Objectives: To examine whether a positive response to TFESI at the first month, can in clinical settings, identify patients with radiculopathy who can avoid surgery for two years. Study Design/Setting. This prospective observational study was conducted at an academic medical center. Methods: Individuals aged ≥20 years who had been referred to our pain center by spine surgeons were enrolled. All patients were assessed using the Numerical Rating Scale (NRS) at baseline and 1 month after the first TFESI. Patients were divided into two groups according to the NRS decrement: the positive response (PR) group achieved a ≥2.0 decrease on the NRS 1 month after the first TFESI compared to baseline and the no response (NR) group achieved a <2.0 decrease on the NRS. The incidence rates of surgery over two years were compared between the two groups. In addition, we calculated the hazard ratio of the PR group to the NR group regarding the incidence of surgery over two years using the Cox proportional hazard model, adjusting for baseline NRS. Results: Seventy-six patients completed the two-year follow-up. In total, 8 and 68 patients had bilateral and unilateral radiculopathy, respectively. The PR and NR groups included 35 and 41 patients, respectively. The rate of surgery avoidance was 85.7% and 73.2% in the PR and NR groups, respectively. This difference was not statistically significant (p=0.26). After adjusting for baseline NRS, the hazard ratio of the PR group to the NR group regarding the incidence of surgery within two years was 0.35 (95% confidence interval: 0.11-1.11, p=0.08). Conclusion: A positive response to TFESI may not identify patients who can avoid surgery for two years.

Impact of Preoperative Motor Status for the Positive Predictive Value of Transcranial Motor-Evoked Potentials Alerts in Thoracic Spine Surgery: A Prospective Multicenter Study by the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: To investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in thoracic spine surgery and evaluate the impact of specific factors associated with positive predictive value (PPV). METHODS: One thousand hundred and fifty-six cases of thoracic spine surgeries were examined by comparing patient backgrounds, disease type, preoperative motor status, and Tc-MEP alert timing. Tc-MEP alerts were defined as an amplitude decrease of more than 70% from the baseline waveform. Factors were compared according to preoperative motor status and the result of Tc-MEP alerts. Factors that showed significant differences were identified by univariate and multivariate analysis. RESULTS: Overall sensitivity was 91.9% and specificity was 88.4%. The PPV was significantly higher in the preoperative motor deficits group than in the preoperative no-motor deficits group for both high-risk (60.3% vs 38.3%) and non-high-risk surgery groups (35.1% vs 12.8%). In multivariate logistic analysis, the significant factors associated with true positive were surgical maneuvers related to ossification of the posterior longitudinal ligament (odds ratio = 11.88; 95% CI: 3.17-44.55), resection of intradural intramedullary spinal cord tumor (odds ratio = 8.83; 95% CI: 2.89-27), preoperative motor deficit (odds ratio = 3.46; 95% CI: 1.64-7.3) and resection of intradural extramedullary spinal cord tumor (odds ratio = 3.0; 95% CI: 1.16-7.8). The significant factor associated with false positive was non-attributable alerts (odds ratio = .28; 95% CI: .09-.85). CONCLUSION: Surgeons are strongly encouraged to use Tc-MEP in patients with preoperative motor deficits, regardless of whether they are undergoing high-risk spine surgery or not. Knowledge of PPV characteristics will greatly assist in effective Tc-MEP enforcement and minimize neurological complications with appropriate interventions.

Role of Transcranial Motor Evoked Potential Monitoring During Traumatic Spinal Injury Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: A prospective multicenter observational cohort study. OBJECTIVE: This study aimed to investigate the role of transcranial motor evoked potential (TcMEP) monitoring during traumatic spinal injury surgery, the timing of TcMEP alerts, and intervention strategies to avoid intraoperative neurological complications. SUMMARY OF BACKGROUND DATA: Intraoperative neuromonitoring, including TcMEP monitoring, is commonly used in high-risk spinal surgery to predict intraoperative spinal cord injury; however, little information is available on its use in traumatic spinal injury surgery. METHODS: The TcMEP monitoring data of 350 consecutive patients who underwent traumatic spinal injury surgery (mean age, 69.3 y) between 2017 and 2021 were prospectively reviewed. In this study, a TcMEP amplitude reduction ≥70% was established as a TcMEP alert. A rescue case was defined as a case with the recovery of TcMEP amplitudes after certain procedures and without postoperative neurological complications. RESULTS: Among the 350 patients who underwent traumatic spinal injury surgery (TcMEP derivation rate 94%), TcMEP monitoring revealed seven true-positive (TP) (2.0%), three rescues (0.9%; rescue rate 30%), 31 false-positive, one false-negative, and 287 true-negative cases, resulting in 88% sensitivity, 90% specificity, 18% positive predictive value, and 99% negative predictive value. The TP rate in patients with preoperative motor deficits was 2.9%, which was higher than that in patients without preoperative motor deficits (1.1%). The most common timing of TcMEP alerts was during decompression (40%). During decompression, suspension of surgery with intravenous steroid injection was ineffective (rescue rate, 0%), and additional decompression was effective. CONCLUSION: Given the low prevalence of neurological complications (2.3%) and the low positive predictive value (18.4%), single usage of TcMEP monitoring during traumatic spinal injury surgery is not recommended. Further efforts should be made to reduce FP alert rates through better interpretation of multimodal Intraoperative neuromonitorings and the incorporation of anesthesiology to improve the positive predictive value. LEVEL OF EVIDENCE: 3.

The clinical role of preoperative fulcrum-bending and supine side-bending radiographs on the prediction of curve correction in adolescent idiopathic scoliosis.

PURPOSE: Preoperative curve assessment is important in adolescent idiopathic scoliosis (AIS). Our objective is to clarify the role of side-bending radiographs (SBR) and fulcrum-bending radiographs (FBR) in predicting postoperative Cobb angle in nonstructural and structural curves. METHODS: Twenty-five consecutive patients with AIS who underwent correction surgery were included. The Cobb angles of structural and nonstructural curves were determined. Cobb angles were measured based on pre- and postoperative standing anteroposterior radiographs of the whole spine. The Cobb angles of SBR and FBR were measured preoperatively. The difference between the Cobb angle at each bending and the preoperative Cobb angle was defined as the predicted correction angle, whereas the difference between the preoperative Cobb angle and postoperative Cobb angle was defined as the surgical correction angle. The correction index was calculated by dividing the surgical correction angle by the predicted correction angle. The difference between the predicted correction angle and surgical correction angle was defined as the prediction error. We compared SBR and FBR for both structural and nonstructural curves in these terms. RESULTS: For both curves, the predicted correction angle of FBR was significantly higher than that of SBR, and the correction index of FBR was significantly lower than that of SBR. Patients with a correction index close to 1 and small prediction error had undergone FBR in the structural curve and SBR in the nonstructural curve. CONCLUSION: FBR is predictive of postoperative correction angle of the structural curve, whereas SBR is predictive of postoperative correction angle of the nonstructural curve.

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.

Efficacy of Transcranial Motor Evoked Potential Monitoring During Intra- and Extramedullary Spinal Cord Tumor Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Multicenter prospective study. OBJECTIVES: Although intramedullary spinal cord tumor (IMSCT) and extramedullary SCT (EMSCT) surgeries carry high risk of intraoperative motor deficits (MDs), the benefits of transcranial motor evoked potential (TcMEP) monitoring are well-accepted; however, comparisons have not yet been conducted. This study aimed to clarify the efficacy of TcMEP monitoring during IMSCT and EMSCT resection surgeries. METHODS: We prospectively reviewed TcMEP monitoring data of 81 consecutive IMSCT and 347 EMSCT patients. We compared the efficacy of interventions based on TcMEP alerts in the IMSCT and EMSCT groups. We defined our alert point as a TcMEP amplitude reduction of ≥70% from baseline. RESULTS: In the IMSCT group, TcMEP monitoring revealed 20 true-positive (25%), 8 rescue (10%; rescue rate 29%), 10 false-positive, a false-negative, and 41 true-negative patients, resulting in a sensitivity of 95% and a specificity of 80%. In the EMSCT group, TcMEP monitoring revealed 20 true-positive (6%), 24 rescue (7%; rescue rate 55%), 29 false-positive, 2 false-negative, and 263 true-negative patients, resulting in a sensitivity of 91% and specificity of 90%. The most common TcMEP alert timing was during tumor resection (96% vs. 91%), and suspension surgeries with or without intravenous steroid administration were performed as intervention techniques. CONCLUSIONS: Postoperative MD rates in IMSCT and EMSCT surgeries using TcMEP monitoring were 25% and 6%, and rescue rates were 29% and 55%. We believe that the usage of TcMEP monitoring and appropriate intervention techniques during SCT surgeries might have predicted and prevented the occurrence of intraoperative MDs.

Development of a Retro-Odontoid pseudotumor in the absence of atlantoaxial instability or rheumatoid arthritis Post-Laminoplasty: case report.

A retro-odontoid pseudotumor (ROP) is commonly associated with atlantoaxial instability (AAI) or rheumatoid arthritis (RA). However, we describe a patient with ROP in the absence of AAI or RA. An 81-year-old man who did not have a history of trauma to the head and neck admitted with neck pain, right upper extremity numbness, lower limb weakness, and walking disturbance. He had a history of C2 dome and C3-7 laminoplasty 10 years ago. Magnetic resonance imaging revealed a retro-odontoid mass with cervical cord compression. Dynamic radiography did not show signs of AAI. He underwent C1 laminectomy without fixation for the ROP. We speculated that the load on C1 and C2 increased because of the progression of kyphosis from C2 to C7 with increases in range of motion, which in turn caused change in the biomechanics of the cervical spine, leading to recurrent partial tear and degradation of the transverse ligament that induced formation of the ROP. Spinal surgeons should keep this complication in mind and inform patients about this potential postoperative complication.

Efficacy of D-Wave Monitoring Combined With the Transcranial Motor-Evoked Potentials in High-Risk Spinal Surgery: A Retrospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Retrospective multicenter cohort study. OBJECTIVES: We aimed to clarify the efficacy of multimodal intraoperative neuromonitoring (IONM), especially in transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) with spinal cord-evoked potentials after transcranial stimulation of the brain (D-wave) in the detection of reversible spinal cord injury in high-risk spinal surgery. METHODS: We reviewed 1310 patients who underwent TES-MEPs during spinal surgery at 14 spine centers. We compared the monitoring results of TES-MEPs with D-wave vs TES-MEPs without D-wave in high-risk spinal surgery. RESULTS: There were 40 cases that used TES-MEPs with D-wave and 1270 cases that used TES-MEPs without D-wave. Before patients were matched, there were significant differences between groups in terms of sex and spinal disease category. Although there was no significant difference in the rescue rate between TES-MEPs with D-wave (2.0%) and TES-MEPs (2.5%), the false-positivity rate was significantly lower (0%) in the TES-MEPs-with-D-wave group. Using a one-to-one propensity score-matched analysis, 40 pairs of patients from the two groups were selected. Baseline characteristics did not significantly differ between the matched groups. In the score-matched analysis, one case (2.5%) in both groups was a case of rescue (P = 1), five (12.5%) cases in the TES-MEPs group were false positives, and there were no false positives in the TES-MEPs-with-D-wave group (P = .02). CONCLUSIONS: TES-MEPs with D-wave in high-risk spine surgeries did not affect rescue case rates. However, it helped reduce the false-positivity rate.

Central sensitization adversely affects quality of recovery following lumbar decompression surgery.

BACKGROUND: Central sensitization (CS) is defined as increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold afferent input. The CS phenomenon is caused by continuous, intense nociceptor inputs triggering a prolonged but reversible increase in the excitability and synaptic efficacy of neurons in the central nociceptive pathway. Most patients undergoing surgery for lumbar spinal stenosis (LSS) experience symptoms for more than three months; therefore, it is possible that CS is associated with postoperative symptoms of LSS. The aim of this study was to clarify the influence of CS in patients who underwent surgery for LSS. METHODS: We used the Central Sensitization Inventory (CSI) to evaluate CS preoperatively. Clinical and neurological symptoms were assessed before surgery and three months after surgery using the Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOA-BPEQ) and the Oswestry Disability Index (ODI). To evaluate the correlation between the preoperative CSI score and each parameter of the JOA-BPEQ before and three months after surgery, a Pearson correlation coefficient was used. We also evaluated the correlation between preoperative CSI and improvement scores for each parameter of the JOA-BPEQ for surgery. Similarly, the ODI was assessed. RESULTS: This study included 118 patients. After surgery, the parameters of lumbar function disorder, social life function disorder, and mental health disorder revealed a statistically significant relationship (r = -0.289, -0.0354, and -0.493, respectively). There was no significant correlation between CSI and improvement scores of the JOA-BPEQ. The ODI assessment after surgery revealed a statistically significant relationship (r = 0.344). There was no significant correlation between the CSI and ODI improvement scores. CONCLUSION: This study showed that the severity of the CSI influenced the postoperative outcomes, and that surgical treatment improved the symptoms of LSS regardless of the occurrence of CS preoperatively.

Accuracy of Lateral Mass Screw Insertion during Cervical Spine Surgery without Fluoroscopic Guidance and Comparison of Postoperative Screw Loosening Rate among Unicortical and Bicortical Screws Using Computed Tomography.

Introduction: Pedicle screws (PSs) or lateral mass screws (LMSs) are used in posterior cervical spine fixation. The former are more firmly fixed but are associated with the risk of neurovascular injury and should be inserted using intraoperative imaging or navigation, which may prolong the surgical duration and is not feasible in all hospitals. This prospective clinical study aimed to evaluate the outcomes of LMS insertions without fluoroscopic guidance and screw loosening rates at 6 months postoperatively using computed tomography (CT). Methods: We examined 38 patients who underwent posterior cervical spine fusion using 206 LMSs in the C3-C6 range between January 2018 and July 2021. The direction of screw insertion followed the Magerl method, and we inserted screws as bicortically as possible without intraoperative imaging. The screw position was examined using CT at 1 week postoperatively. Screw insertion angles, bicortical insertion rate, facet violation, and neurovascular injury were evaluated. Screw loosening with unicortical and bicortical screws (US and BS, respectively) was investigated using CT at 6 months postoperatively. Results: The average LMS length was 14.1 mm. The average axial and sagittal angles were 33.9° and 29.2°, respectively. Among the 206 LMSs inserted, 167 were BS; of these, 94.6% had screw length protrusion of 0-2 mm. Facet violation was observed in 3.4% of all screws but without neurovascular injury. Six months postoperatively, loosening of 25 screws (12.1%) occurred, including 17 (18.3%) USs and 8 (8.39%) BSs. The screw loosening rate was significantly higher in US than for BS (43.6% [17/39] vs. 4.8% [8/167], P<0.01). Conclusions: Over 80% of LMSs were inserted bicortically without intraoperative imaging. By devising the screw length selection process, we inserted for screw loosening was more common in US and more likely at the fixed end.

Radiological Evaluation of Pelvic Morphology for S2 Alar-Iliac Screw Insertion in the Japanese Samples: A Retrospective Cohort Study.

Introduction: S2 alar-iliac screw (S2AIS) insertion for lumbosacral fixation is becoming a common procedure for deformity surgeries. However, studies that have reported the anatomy and morphometric features of the pelvis for S2AIS insertion in the Japanese samples are scarce. This study aimed to elucidate the morphometric features of the pelvis regarding S2AIS insertion in the Japanese samples. Methods: We used 60 computed tomography scans of the pelvis (30 men and 30 women). The entry point for the S2AIS was determined as 1-mm lateral and 1-mm distal to the S1 dorsal sacral foramen. We resliced the plane in which the pelvis was sectioned obliquely from this entry point to the anterior inferior iliac spine in the sagittal plane. We bilaterally placed the shortest and longest virtual S2AISs in this plane using a 4-mm margin. We analyzed the length, angle, and safety of the determined trajectory and compared these measurements according to sex and age. Results: The median longest and shortest screw lengths were 108.1 and 103.3 mm, respectively. The median longest and shortest distances from the entry point to the sacroiliac joint were 31.2 and 28.2 mm, respectively. The median smallest and largest lateral angulations were 40.7° and 47.3°, respectively. The median angle range was 4.2°. The median caudal angulation was -2.8°. The median shortest and longest distances from the S2AISs to the acetabular roof were 23.5 and 27.4 mm, respectively. The median distance from the S2AISs to the sciatic notch was 23.1 mm. Assuming the insertion of screw with a diameter of 8 mm, S2AIS insertion was difficult in 32 of 120 (27%) screws because the dorsal cortex of the sacrum was damaged. Conclusions: Screw length and lateral angulation were similar to those in previous studies. Insertion difficulty occurred in 27% of screws.

Retrospective observational study of the effects of residual neuromuscular blockade and sugammadex on motor-evoked potential monitoring during spine surgery in Japan.

Given neuromuscular blockade (NMB) can affect the amplitude and detection success rate of motor-evoked potentials (MEP), sugammadex may be administered intraoperatively. We evaluated the factors affecting the degree of residual NMB (i.e., the train-of-four [TOF] ratio) and the relationship between TOF ratio and MEP detection success rate in Japanese patients undergoing spine surgery. This single-center retrospective observational study included adults who underwent spine surgery under propofol/remifentanil anesthesia, received rocuronium for intubation, and underwent myogenic MEP monitoring after transcranial stimulation. TOF ratios were assessed using electromyography. Sugammadex was administered after finishing the MEP setting and the TOF ratio was ≤0.7. To identify factors affecting the TOF ratio, TOF ratio and MEP detection success rate were simultaneously measured after finishing the MEP setting; to compare the time from intubation to the start of MEP monitoring after NMB recovery between sugammadex and spontaneous recovery groups, multivariable analyses were performed. Of 373 cases analyzed, sugammadex was administered to 221 (59.2%) cases. Age, blood pressure, hepatic impairment, and rocuronium dose were the main factors affecting the TOF ratio. Patients with higher TOF ratios (≥0.75) had higher MEP detection success rates. The time from intubation to the start of MEP monitoring after NMB recovery was significantly shorter in patients administered sugammadex versus patients without sugammadex (P < .0001). The MEP detection success rate was higher in patients with a TOF ratio of ≥0.75. Sugammadex shortened the time from intubation to the start of MEP monitoring after NMB recovery.

The Utility of Transcranial Stimulated Motor-Evoked Potential Alerts in Cervical Spine Surgery Varies Based on Preoperative Motor Status.

STUDY DESIGN: A prospective multicenter observational study. OBJECTIVE: The aim was to investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in cervical spine surgery and identify factors associated with positive predictive value when Tc-MEP alerts are occurred. SUMMARY OF BACKGROUND DATA: The sensitivity and specificity of Tc-MEP for detecting motor paralysis are high; however, false-positives sometimes occur. MATERIALS AND METHODS: The authors examined Tc-MEP in 2476 cases of cervical spine surgeries and compared patient backgrounds, type of spinal disorders, preoperative motor status, surgical factors, and the types of Tc-MEP alerts. Tc-MEP alerts were defined as an amplitude reduction of more than 70% from the control waveform. Tc-MEP results were classified into two groups: false-positive and true-positive, and items that showed significant differences were extracted by univariate analysis and detected by multivariate analysis. RESULTS: Overall sensitivity was 66% (segmental paralysis: 33% and lower limb paralysis: 95.8%) and specificity was 91.5%. Tc-MEP outcomes were 33 true-positives and 233 false-positives. Positive predictive value of general spine surgery was significantly higher in cases with a severe motor status than in a nonsevere motor status (19.5% vs . 6.7%, P =0.02), but not different in high-risk spine surgery (20.8% vs . 19.4%). However, rescue rates did not significantly differ regardless of motor status (48% vs . 50%). In a multivariate logistic analysis, a preoperative severe motor status [ P =0.041, odds ratio (OR): 2.46, 95% confidence interval (95% CI): 1.03-5.86] and Tc-MEP alerts during intradural tumor resection ( P <0.001, OR: 7.44, 95% CI: 2.64-20.96) associated with true-positives, while Tc-MEP alerts that could not be identified with surgical maneuvers ( P =0.011, OR: 0.23, 95% CI: 0.073-0.71) were associated with false-positives. CONCLUSION: The utility of Tc-MEP in patients with a preoperative severe motor status was enhanced, even in those without high-risk spine surgery. Regardless of the motor status, appropriate interventions following Tc-MEP alerts may prevent postoperative paralysis.

Temporal Evolution of White Blood Cell Count and Differential: Reliable and Early Detection Markers for Surgical Site Infection Following Spinal Posterior Decompression Surgery.

Introduction: For early detection of surgical site infection (SSI) following spinal decompression surgery, we compared temporal changes in the values of laboratory markers that are not affected by operative parameters. Methods: The study included 302 patients, which were divided into an SSI group (patients who developed deep SSI) and a non-SSI group for analysis. We reviewed data on C-reactive protein level, total white blood cell (WBC) count, and WBC differential percentage and count before spinal decompression, on postoperative day 1, and on postoperative day 4. We identified laboratory markers that are not affected by operative parameters (operating time, intraoperative blood loss, and number of operative segments). Laboratory markers with a significant difference observed between the peak or nadir value and the value in the subsequent survey day were considered as an indicator of SSI. We examined the utility of each indicator by calculating sensitivity and specificity. Furthermore, we investigated the utility of the combination of all five indicators (wherein the recognition of one marker was considered positive). Results: Temporal changes in five laboratory markers were considered indicators of SSI. The changes from postoperative day 1 to postoperative day 4 were as follows: (1) increased WBC count (42% sensitivity, 88% specificity), (2) increased neutrophil percentage (25% sensitivity, 96% specificity), (3) increased neutrophil count (25% sensitivity, 94% specificity), (4) decreased lymphocyte percentage (25% sensitivity, 95% specificity), and (5) decreased lymphocyte count (25% sensitivity, 85% specificity). The combination of these five markers showed a 50% sensitivity, 81% specificity, and 0.65 AUC. Conclusions: Five markers were found to be reliable indicators of SSI following spinal decompression surgery because they were not affected by operative parameters. The combination of all five indicators had moderate sensitivity and high specificity. Therefore, this may be reliable and useful for the early detection of SSI.

Transurethral electrical stimulation for intraoperative bulbocavernosus reflex monitoring during spine surgery in females.

OBJECTIVE: Intraoperative bulbocavernosus reflex (BCR) monitoring is more difficult in females than in males. This study was designed to compare the feasibility of transurethral electrical stimulation BCR (tu-BCR) monitoring with that of conventional BCR (c-BCR) monitoring during spine surgery in females. METHODS: Twenty-four females were included. For stimulation in c-BCR monitoring, a pair of surface electrodes was placed on the genitals (cathode/anode: clitoris/adjacent labium). For stimulation in tu-BCR monitoring, a urethral catheter attached to a pair of electrodes was inserted into the urethra. BCRs were recorded from the external anal sphincter after a single train of four stimulation pulses. RESULTS: There was no postoperative urinary tract injury associated with urethral catheter insertion for tu-BCR. Tu-BCR monitoring had a significantly higher success rate of baseline recording than c-BCR monitoring (87.5% vs 66.7%, respectively, p = 0.028). The specificities of tu-BCR and c-BCR monitoring were 100% and 87.2%, respectively. The sensitivity was not calculated because no patients had postoperative urinary or bowel dysfunction. CONCLUSIONS: Our data indicate that tu-BCR monitoring improved the success rate of baseline recording and specificity during spine surgery in females. SIGNIFICANCE: Tu-BCR monitoring was more reliable than c-BCR monitoring during spine surgery in females.