Intraoperative Neuromonitoring Auxiliary Significance of DNEP for MEP-positive Event During Severe Spinal Deformity Surgery.

STUDY DESIGN: This was a retrospective analysis. OBJECTIVE: The objective of this study was to assess the intraoperative neuromonitoring auxiliary significance of descending neurogenic-evoked potential (DNEP) for motor-evoked potential (MEP) during severe spinal deformity surgery when MEP-positive event occurs. SUMMARY OF BACKGROUND DATA: MEP detection is the most widely applied neurological monitoring technique in spinal deformity surgery. MEP is quite vulnerable to anesthesia, blood pressure, and other intraoperative factors, leading to a high false-positive rate of MEP (3.2%-45.0%), which has greatly interfered with the surgical process. At present, the widely used "presence-or-absence" alarm criteria of MEP is not enough to solve the problem of false positive of MEP. METHODS: A total of 205 cases undergoing severe spinal deformity correction were retrospectively studied. Overall, 74 MEP-positive cases were classified as 2 subgroups: DNEP (+) and DNEP (-) groups. The MEP recovery, wake-up test, and Frankle grade were used to assess the neurological functions. The perioperative and long-term neurological outcomes were assessed. RESULTS: There were significant differences in preoperative scoliosis angle and kyphosis angle between DNEP (-) and DNEP (+) groups. Patients in DNEP (-) group showed more MEP improvement (81.5%), compared with the DNEP (+) group (53.2%). The Wake-up test showed 59.3% motor function deficit cases in DNEP (-) group, which was lower than the 87.2% in DNEP (+) group. More patients in DNEP (-) group had normal nerve function (Frankel level E) than those in DNEP (+) group immediately after surgery, as well as at follow-up. CONCLUSIONS: MEP-positive cases with intraoperative DNEP (-) showed superior prognosis after severe spinal deformity surgery. Intraoperative DNEP could be regarded as an important quantitative tool to assist MEP to monitor neurological injury and can serve as a temporary substitution monitoring technique after MEP is lost.

The radiographic, pulmonary, and clinical outcomes of patients with severe rigid spinal deformities treated via halo-pelvic traction.

BACKGROUND: The severe rigid deformity patients with pulmonary dysfunction could not tolerate complicated corrective surgery. Preoperative traction are used to reduce the curve magnitude and improve the pulmonary function before surgery, including halo-gravity traction (HGT) and halo-pelvic traction (HPT). The present study aimed to retrospectively compare the radiographic, pulmonary and clinical outcomes of preoperative HGT and HPT in severe rigid spinal deformity with respiratory dysfunction. METHODS: 81 cases of severe rigid kyphoscoliosis treated with preoperative traction prior to corrective surgery for spinal deformity between 2016 and 2019 were retrospectively reviewed. Two patient groups were compared, HPT group (N = 30) and HGT group (N = 51). Patient demographics, coronal and sagittal Cobb angles and correction rates, pulmonary function, traction time, osteotomy grade, and postoperative neurological complications were recorded for all cases. RESULTS: The coronal Cobb angle was corrected from 140.67 ± 2.63 to a mean of 120.17 ± 2.93° in the HGT group, and from 132.32 ± 4.96 to 87.59 ± 3.01° in the HPT group (mean corrections 15.33 ± 1.53 vs. 34.86 ± 3.11 %) (P = 0.001). The mean major sagittal curve decreased from 134.28 ± 3.77 to 113.03 ± 4.57° in the HGT group and from 129.60 ± 8.45 to 65.61 ± 7.86° in the HPT group (P < 0.001); the mean percentage corrections were 16.50 ± 2.13 and 44.09 ± 9.78 % (P < 0.001). A significant difference in the pulmonary function test results was apparent between the two groups; the mean improvements in the FVC% of the HGT and HPT groups were 6.76 ± 1.85 and 15.6 ± 3.47 % (P = 0.024). The HPT group tended to exhibit more FEV% improvement than the HGT group, but the difference was not significant (5.15 ± 2.27 vs. 11.76 ± 2.22 %, P = 0.91). CONCLUSIONS: Patients with severe rigid kyphoscoliosis who underwent preoperative HPT exhibited better radiographic correction of the deformity, and pulmonary function, and required fewer osteotomies compared to the HGT group. Thus, HPT may be useful for severe rigid spinal deformity patients with pulmonary dysfunction.

Risk factors for neurological complications in severe and rigid spinal deformity correction of 177 cases.

BACKGROUND: Difficult procedures of severe rigid spinal deformity increase the risk of intraoperative neurological injury. Here, we aimed to investigate the preoperative and intraoperative risk factors for postoperative neurological complications when treating severe rigid spinal deformity. METHODS: One hundred seventy-seven consecutive patients who underwent severe rigid spinal deformity correction were assigned into 2 groups: the neurological complication (NC, 22 cases) group or non-NC group (155 cases). The baseline demographics, preoperative spinal cord functional classification, radiographic parameters (curve type, curve magnitude, and coronal/sagittal/total deformity angular ratio [C/S/T-DAR]), and surgical variables (correction rate, osteotomy type, location, shortening distance of the osteotomy gap, and anterior column support) were analyzed to determine the risk factors for postoperative neurological complications. RESULTS: Fifty-eight patients (32.8%) had intraoperative evoked potentials (EP) events. Twenty-two cases (12.4%) developed postoperative neurological complications. Age and etiology were closely related to postoperative neurological complications. The spinal cord functional classification analysis showed a lower proportion of type A, and a higher proportion of type C in the NC group. The NC group had a larger preoperative scoliosis angle, kyphosis angle, S-DAR, T-DAR, and kyphosis correction rate than the non-NC group. The results showed that the NC group tended to undergo high-grade osteotomy. No significant differences were observed in shortening distance or anterior column support of the osteotomy area between the two groups. CONCLUSIONS: Postoperative neurological complications were closely related to preoperative age, etiology, severity of deformity, angulation rate, spinal cord function classification, intraoperative osteotomy site, osteotomy type, and kyphosis correction rate. Identification of these risk factors and relative development of surgical techniques will help to minimize neural injuries and manage postoperative neurological complications.

A Retrospective Study of Surgical Correction for Spinal Deformity with and without Osteotomy to Compare Outcome Using Intraoperative Neurophysiological Monitoring with Evoked Potentials.

BACKGROUND This study aimed to evaluate the effects of different combined evoked potentials monitoring modes for non-osteotomy and osteotomy surgery of spinal deformity, and to select individualized modes for various surgeries. MATERIAL AND METHODS We retrospectively reviewed a total of 188 consecutive cases undergoing spinal deformity correction. All patients were classified into 2 cohorts: non-osteotomy (Group A) and osteotomy (Group B). According to intraoperative evoked potential monitoring mode, Group A was divided into 2 sub-groups: A1 [spinal somatosensory evoked potential (SSEP)/motor evoked potential (MEP), n=67)] and A2 [SSEP/MEP/descending neurogenic evoked potential (DNEP), n=52]. Group B was classified as B1 (SSEP/MEP, n=27) and B2 (SSEP/MEP/DNEP, n=42). The demographics, surgical parameters, and evoked potential events of different combined monitoring modes were analyzed within each group. RESULTS The baselines of SSEP/MEP/DNEP in all cases were elicited successfully. Three cases with evoked potential (EP) events (2 with MEP changes and 1 with SSEP/MEP change) were noted in Group A1 and 1 with SSEP change in Group A2, with no neurological complications. Thirteen cases in Group B1 were positive for MEP intraoperatively, including 16 EP events (13 with MEP change and 3 with both SSEP+MEP changes), with no neural complications. In Group B2, 15 cases had 21 EP events, including 12 with MEP change and 2 with SSEP+MEP changes, with no complications. Postoperative neurological complications were observed in 5 of the 7 cases with SS4EP/DNEP changes. CONCLUSIONS Intraoperative simultaneous SSEP/MEP can effectively reflect neurological function in non-osteotomy spinal surgery patients. Simultaneous SSEP/MEP/DNEP can effectively avoid the unnecessary interference by false-positive results of MEP during osteotomy.

Multimodality Intraoperative Neuromonitoring in Severe Thoracic Deformity Posterior Vertebral Column Resection Correction.

BACKGROUND: Multimodal intraoperative neuromonitoring (IONM) has been proposed as an effective way to reduce permanent neurologic injury during spinal deformity surgery. However, few studies have reported evoked potential changes at different surgical stages of thoracic posterior vertebral column resection (PVCR). METHODS: A total of 82 cases with severe thoracic deformity (Yang's A type) treated by PVCR in a single institution between January 2010 and March 2015 were reviewed. Multimodal IONM including somatosensory evoked potential, motor evoked potential, and descending neurogenic evoked potential was performed for real-time assessment of spinal cord function during surgery. The risk factors of neuromonitoring events at different surgical stages were documented and analyzed. RESULTS: Multimodal IONM was successfully performed in all 82 cases. Thirty-nine neuromonitoring events presented in 27 (32.9%) cases. Neurologic monitoring events were more likely to occur in patients with larger scoliosis and kyphosis, longer osteotomy closure distance, more Halo gravity traction, more screw insertion, and higher PVCR segments. The reasons for monitoring changes included 6 events during screw insertion, 20 during osteotomy, 9 during osteotomy gap closure, and 4 during deformity correction. New postoperative neurologic deficits were observed in 11 (13.4%) cases including 1 incomplete paraplegia, 8 transient cord deficits, and 2 nerve root injuries. CONCLUSIONS: Multimodal IONM can effectively identify neurologic deficits throughout surgery. Osteotomy and osteotomy gap closure are the surgical stages with the highest neurologic risks during PVCR procedures. It is imperative to improve dexterity since the majority of neuromonitoring events are caused by surgical techniques.

Surgical Outcome Comparison of Posterior Vertebral Column Resection with or without Anterior Column Support in Treatment of Yang's Type A Severe Thoracic Spinal Deformity.

BACKGROUND: The use of posterior vertebral column resection (PVCR) has extended the treatment of severe spinal deformity. However, the practice guidelines for anterior column support in patients treated by PVCR remain ill defined. The objective of the present study was to compare the clinical and radiographic outcomes of severe thoracic spinal deformity treated by PVCR with and without anterior column support (ACS). METHODS: We performed a prospective study of 57 patients with severe thoracic deformity (classified as Yang's A type) treated by PVCR with or without anterior column support from January 2010 to April 2015. The patient characteristics, radiographic parameters, intraoperative data, and complications were analyzed to clarify these 2 clinical series. RESULTS: The sex, age, diagnosis, curve magnitude, and curve type were similar between the PVCR with ACS group (n = 21) and non-ACS group (n = 36) preoperatively. Evaluation of the radiographic parameters, intraoperative data, and complications found no statistically significant intergroup differences, except for the osteotomy distance (non-ACS group, 4.0 cm; ACS group, 5.3 cm; P < 0.001) and shortening distance of the osteotomy gap (non-ACS group, 4.0 cm; ACS group, 3.5 cm; P = 0.005). CONCLUSIONS: The results of the present study have shown that PVCR without ACS seems to be a safe and effective technique for Yang's A type severe thoracic spinal deformity correction compared with PVCR with ACS. PVCR without ACS requires a relatively smaller osteotomy range and could potentially decrease the risk of implant failure due to bone to bone fusion.

Predictive Value of Spinal Cord Function Classification and Sagittal Deformity Angular Ratio for Neurologic Risk Stratification in Patients with Severe and Stiff Kyphoscoliosis.

BACKGROUND: Three-column osteotomies were developed to treat severe spinal deformities but result in high neurologic complications and require further risk stratification. The present study investigated whether the combination of spinal cord function classification (SCFC) and deformity angular ratio (DAR) could further stratify the neurologic risks in the surgical correction of severe and stiff kyphoscoliosis. METHODS: The patients with kyphoscoliosis who had undergone posterior 3-column osteotomies at the spinal cord level were reviewed. Using our SCFC system, the preoperative neurologic function (type A, B, or C) was classified. The sagittal DAR (S-DAR), coronal, and total DARs were calculated. Intraoperative monitoring events and new neurologic deficits (NNDs) postoperatively were documented and analyzed using the SCFC and DAR or both combined. RESULTS: The NND rates increased significantly from type A to C (P = 0.000) and increased exponentially with an increase in S-DAR in types B and C but not type A. They also increased exponentially with aggravation of the SCFC in the medium and high but not low S-DAR group. All NNDs had recovered at 3 months for type A and most had recovered at 6 months for type B or C. CONCLUSIONS: The NNDs in type A SCFC usually experienced better recovery even with high S-DARs. Type B SCFC with an S-DAR >20° and type C SCFC with any S-DAR resulted in significantly greater intra- and postoperative neurologic risks. The combination of SCFC and S-DAR can further stratify the intra- and postoperative neurologic risks with these procedures.

The Safety and Efficiency of PVCR without Anterior Support Applied in Treatment of Yang Type A Severe Thoracic Kyphoscoliosis.

OBJECTIVE: To assess the clinical and radiographic outcomes of posterior vertebral column resection (PVCR) without anterior support in treatment of Yang type A severe rigid thoracic kyphoscoliosis. METHODS: The records of 27 Yang type A severe thoracic kyphoscoliosis patients treated with PVCR without anterior support from January 2010 to September 2013 were analyzed retrospectively. Intraoperative multimodal neurophysiological monitoring was conducted in all patients. The 6 modes were somatosensory evoked potential, motor evoked potential, descending neurogenic evoked potential, spinal cord evoked potential, and electromyography (both triggered and free run). Radiographic parameters and complications were used to evaluate the clinical outcomes. RESULTS: PVCR without anterior support was conducted successfully in all 27 patients. Intraoperative monitoring events occurred in 3 patients (3/27); of these, 1 patient (1/27) showed postoperative spinal cord injury, but completely recovered within 9 months after the operation (Frankel level E). The number and osteotomy space of vertebrae resection were mean 1.33 levels and 3.7 cm, respectively. All cases achieved good coronal and sagittal curve correction. No implant related complications occurred until the latest follow-up. The average follow-up was 40.1 months (range, 24-59 months). CONCLUSIONS: In this study, we found that posterior vertebral column resection (PVCR) without any anterior support with a mean 3.7 cm shortening of the spinal column is safe, if close and unyielding contact of end plates can be obtained. A comprehensive understanding of the technique and intensive intraoperative neuromonitoring is mandatory to perform these challenging and complex spine deformity correction procedures safely.

Computed Tomography Based Three-dimensional Measurements of Spine Shortening Distance After Posterior Three-column Osteotomies for the Treatment of Severe and Stiff Scoliosis.

STUDY DESIGN: Retrospective study. OBJECTIVES: This study is to measure and analyze the changes of three-dimensional (3D) distances of spinal column and spinal canal at the three-column osteotomy sites and address their clinical and neurologic significance. SUMMARY OF BACKGROUND DATA: Three-column osteotomies were developed to treat severe and stiff spine deformities with insufficient understanding on the safe limit of spine shortening and the relationship between the shortening distance of the spinal column and that of the spinal canal. METHODS: Records of 52 continuous patients with severe and stiff scoliosis treated with three-column spine osteotomies at our institution from July 2013 to June 2015 were reviewed. The preoperative spinal cord function classification were type A in 31 cases, type B in 10 cases, and type C in 11 cases. The types of osteotomies carried out were extended pedicle subtraction osteotomy in nine patients and posterior vertebral column resection in 43 patients. Multimodality neuromonitoring strategies were adopted intraoperatively. 3D pre- and postoperative spine models were reconstructed from the computed tomography (CT) scans. The distances of convex and concave spinal column and the spinal canal shortening were measured and analyzed. RESULTS: The spinal column shortening distance (SCSD) measured on the 3D models (27.8 mm) were statistically shorter than those measured intraoperatively (32.8 mm) (P < 0.05); however, they were strongly correlated statistically (r = 0.82). The central spinal canal shortening distance (CCSD) was significantly shorter than the convex SCSD (P < 0.05). The convex SCSD and CCSD were significantly shorter in cases with anterior column strut graft than in those with bone-on-bone fusion (P < 0.05). CONCLUSION: The shortening distance of the convex spinal column cannot represent that of the central spinal canal in patients with severe scoliosis. The spinal column shortening procedure in appropriately selected patient groups with bone-on-bone fusion is a viable option with the CCSD being significantly shorter than the convex SCSD. LEVEL OF EVIDENCE: 4.

A proposed classification system for guiding surgical strategy in cases of severe spinal deformity based on spinal cord function.

PURPOSE: Spinal cord function classification systems are not useful for guiding surgery in patients with severe spinal deformities. The aim of this study is to propose a classification system for determining a surgical strategy that minimizes the risk of neurological dysfunction in patients with severe spinal deformities. METHODS: The records of 89 patients with severe spinal deformities treated with vertebral column reconstruction from 2008 to 2013 were retrospectively analyzed. Based on neurophysiological monitoring, magnetic resonance imaging, and neurological symptoms patients were categorized into three groups: group A, normal spinal cord, normal evoked potentials and no neurological symptoms; group B, spinal cord abnormalities and/or abnormal evoked potentials but no neurological symptoms; group C, neurological symptoms with or without spinal cord abnormalities/abnormal evoked potentials. Outcomes and complications were compared between the groups. RESULTS: A total of 89 patients (51 male, 38 female) were included with 47 (52.8 %), 16 (18.0 %), and 26 (29.2 %) patients in groups A, B and C, respectively, and a mean follow-up 34.5 months. There were no differences in age, gender, average preoperative scoliosis, and kyphosis among three groups, but there were differences with respect to the causes of severe spinal deformity and the corrective rate of scoliosis and kyphosis. Changes in intraoperative evoked potentials were different in these three types according to this new classification, and the recovery rates of changes in the three groups were 71.1, 50.0, and 14.1 %, respectively. Postoperative spinal cord injury was positively related to intraoperative changes of evoked potentials. CONCLUSION: The classification system may be useful for guiding surgical decisions in patients with severe spinal deformities to minimize the risk of neurological complications.