Safety and Efficacy of Tranexamic Acid in Spinal Surgery: A Systematic Review and Meta-Analysis.

Background: Tranexamic acid (TXA) has gained popularity in spinal surgery because of its potential to reduce blood loss. However, concerns regarding its safety and efficacy remain. This systematic review and meta-analysis aimed to evaluate the efficacy of TXA in reducing blood loss and its safety profile in spinal surgeries. Methods: A comprehensive search was conducted in electronic databases for randomized controlled trials and prospective studies evaluating the use of TXA in spinal surgery. The primary outcomes were intraoperative and total estimated blood loss (EBL), and the secondary outcomes included the incidence and types of complications associated with TXA use. Meta-analyses were performed using random-effects models. Results: Thirteen studies involving 1,213 participants were included in the meta-analysis. The use of TXA was associated with significant reductions in both intraoperative (mean difference: -46.56 mL [-73.85, -19.26], p<0.01]) and total EBL (mean difference: -210.17 mL [-284.93, -135.40], p<0.01) while also decreasing the need for blood transfusions (risk ratio: 0.68 [0.51, 0.90], p<0.01). No significant difference was found in the incidence and types of thrombotic complications when TXA was used in spinal surgery. Subgroup analysis showed consistent results in instrumentation and fusion surgery and different doses of TXA. Conclusions: TXA is effective in reducing intraoperative and overall blood loss in spinal surgery without increasing the risk of complications. These findings support the use of TXA to improve patient outcomes. However, caution should be exercised because of the heterogeneity among the included studies. Further research is needed to confirm these findings and explore potential long-term complications.

Satisfaction following correction of spinal deformity: Cultural and regional effects on outcome.

Corrective spine surgery for spinal deformities, such as adolescent idiopathic scoliosis (AIS) and adult spinal deformity (ASD), aims to enhance the quality of life by addressing physical impairments. However, the extent of patient satisfaction after surgery, which includes pain management, functional recovery, and psychological contentment, exhibits considerable variation across different cultural and geographical landscapes. This review describes the influence of cultural and regional disparities on postoperative satisfaction in AIS and ASD surgery with a particular emphasis on the disparities between the US and Japan. This review underscores the intricate relationship between surgical outcomes and patient-reported satisfaction metrics. The investigation reveals significant contrasts in patient satisfaction and clinical results between these 2 countries, attributed to divergent cultural expectations, lifestyle adaptations, and perceptions of bodily image. These distinctions are crucial for healthcare professionals to recognize, as they necessitate a culturally nuanced approach to patient care. This comparative review not only enhances the understanding of patient experiences across cultures but also provides valuable guidance for physicians in customizing their strategies to align with the varied expectations of their patients, thereby improving postoperative satisfaction and overall quality of life. This review emphasizes the necessity of a tailored and culturally sensitive approach to managing spinal deformities, underscoring the need to factor in cultural and regional elements to enhance patient satisfaction and surgical outcomes.

Proximal Junctional Failure in Adult Spinal Deformity Surgery: An In-depth Review.

Adult spinal deformity (ASD) surgery aims to correct abnormal spinal curvature in adults, leading to improved functionality and reduced pain. However, this surgery is associated with various complications, one of which is proximal junctional failure (PJF). PJF can have a significant impact on a patient's quality of life, necessitating a comprehensive understanding of its causes and the development of effective management strategies. This review aims to provide an in-depth understanding of PJF in ASD surgery. PJF is a complex complication resulting from a multitude of factors including patient characteristics, surgical techniques, and postoperative management. Age, osteoporosis, overcorrection of sagittal alignment, and poor bone quality are identified as significant risk factors. The clinical implications of PJF are substantial, often requiring revision surgery and causing a considerable decrease in patients' quality of life. Prevention strategies include careful preoperative planning, appropriate patient selection, and optimization of surgical techniques. Treatment often necessitates a multifaceted approach, including surgical intervention and the management of underlying risk factors. Predictive modeling is an emerging field that may offer a promising avenue for the risk stratification of patients and individualized preventive strategies. A thorough understanding of PJF's pathogenesis, risk factors, and clinical implications is essential for surgeons involved in ASD surgery. Current preventive measures and treatment strategies aim to mitigate the risk and manage the complications of PJF, but the complication cannot be entirely prevented. Future research should focus on the development of more effective preventive and treatment strategies, and predictive models could be valuable in this pursuit.

Clinical Results after Release of Sternocleidomastoid Muscle Surgery for Neglected Congenital Muscular Torticollis-Unipolar vs. Bipolar Release Surgery.

BACKGROUND: Although the surgical release of the sternocleidomastoid muscle (SCM) is required for residual congenital muscular torticollis (CMT), the surgical outcomes between bipolar and unipolar SCM release remained unclear. The purpose of the present study was to assess surgical outcomes after bipolar and unipolar release of SCM in adolescent/adult patients with neglected CMT. METHODS: Twenty-one consecutive adolescent/adult patients with neglected CMT who underwent surgical treatment were enrolled. Clinical and radiographic outcomes were evaluated at preoperative and final follow-up. RESULTS: The bipolar release of SCM was performed in 3 patients (B group; males, n = 1, females, n = 2) and the unipolar release of SCM in 18 patients (U group; males, n = 6, females, n = 12). The mean age at surgery was 40.0 ± 17.0 years in Group B, and that was 32.3 ± 13.1 years in Group U (p = 0.47). The mean follow-up period was 16.0 ± 5.7 months in Group B and 10.4 ± 7.6 months in Group U (p = 0.22). Cervicomandibular angle correction rates were comparable at 75.4 ± 2.4% for the B group and 73.1 ± 11.7% for the U group (p = 0.62). There was no significant difference in clinical outcome according to the modified Cheng and Tang score between the two groups (p = 0.89). No major complications arose, although one patient exhibited a transient neurological deficit of the greater auricular nerve, and one patient developed a hematoma in the B group. CONCLUSIONS: The unipolar SCM release appeared to be a non-inferiority and less invasive procedure, minimizing surgical scars and avoiding potential auricular nerve damage in adolescent/adult patients with neglected CMT.

Translucent Zone Between Autograft and Endplate Two Months Postoperatively Is an Independent Predictor of Delayed Osseous Union in Elderly Patients With Posterior Lumbar Interbody Fusion Surgery.

Background Delayed union or pseudoarthrosis after posterior lumbar interbody fusion (PLIF) is associated with poor outcomes in health-related quality of life. Therefore, it is important to achieve earlier solid fusion for a successful clinical outcome after PLIF. A few authors reported that biomechanical factors may influence spinal fusion rates. The purpose of our retrospective study was to evaluate the independent predictors of delayed osseous union related to intraoperative procedures of PLIF, and to find ways to reduce delayed osseous union. Methods This was a retrospective study of a completed trial. We reviewed 66 elderly patients with osteoporosis after PLIF (all female, mean age 71 years, follow-up period over 6 months). Lumbar computed tomography scans at 2 months postoperatively were examined for the presence of a translucent zone between autograft and endplate (more than 50% of vertebral diameter), and autograft position with bone bridging (anterior, central, or posterior). Osseous union was assessed by using computed tomography 6 months postoperatively. Results Thirty-three patients (50%) showed complete osseous union, while 33 did not. A translucent zone between autograft and endplate two months postoperatively was observed in nine patients (27%) in the union group and in 23 (70%) in the nonunion group (p<0.01). Autograft position with bone bridging two months postoperatively was anterior, central, and posterior in 17 (52%), 30 (91%), and 20 patients (61%) in the union group, and in 12 (36%), 20 (61%), and seven patients (21%) in the nonunion group (p=0.22, p<0.01, and p<0.01), respectively. Multivariate logistic regression analysis showed that the presence of a translucent zone between autograft and endplate (odds ratio, 0.101; 95% confidence interval: 0.026-0.398; p<0.01) and teriparatide administration (odds ratio, 8.810; 95% confidence interval: 2.222-34.936; p<0.01) were independently associated with osseous union after PLIF. Conclusions A translucent zone between autograft and endplate at two months postoperatively independently predicted delayed osseous union within six months after PLIF. Complete osseous union rates were higher in patients with posterior bone bridging two months postoperatively than in those without. These findings apart from preoperative predictors of osseous union might serve as indicators of how intraoperative techniques affects osseous union enhancement.

Comparative Study of S2-Alar-Iliac Screw Trajectories between Males and Females Using Three-Dimensional Computed Tomography Analysis: The True Lateral Angulation of the S2-Alar-Iliac Screw in the Axial Plane.

The S2 alar-iliac screw (S2AIS) is commonly used for long spinal fusion as a rigid distal foundation in spinal deformity surgeries, and it is also used in percutaneous sacropelvic fixation for providing an in-line connection to the proximal spinal constructs without using offset connectors. Although the pelvic shape is different between males and females, reports on S2AIS trajectories according to gender have been scarce in the literature. In this paper, S2AIS trajectories are compared between males and females using pelvic three-dimensional computed tomography (3D-CT) in a normal Japanese population. After resetting the caudal angulation in CT-imaging plane manipulation, the angulation of S2AIS was more lateral in the axial plane and more horizontal in the coronal plane in females. Mean distances from the midline to starting points of S2AIS tended to be shorter in females, whereas mean distances from the midline to the posterior superior iliac spine was significantly longer in females. We also found that there were positive correlations between the patients' height and the maximal lengths of S2AISs, and the patients' height and minimal areas of S2AIS pathways. Our results are useful not only for conventional open spinal surgery, but also for minimally invasive spine surgery.

Preliminary Clinical Outcome of One-level Mobi-C Total Disc Replacement in Japanese Population.

INTRODUCTION: In 2018, the first Mobi-CⓇ total disk replacement (TDR) case was performed in Japan. In this study, we examined the preliminary clinical outcome of Mobi-CⓇ for degenerative cervical spine disease. METHODS: We examined 24 consecutive patients who underwent 1-level TDR after 2018 and followed up for more than 6 months after surgery. The evaluation criteria included age, gender, diagnosis, follow-up period, surgical level, implant size, surgery time, intraoperative bleeding volume, complications, revision surgery, imaging findings, JOA score, and various questionnaires. RESULTS: The mean age was 52.7 years, 13 males and 11 females. There were 15 cases of cervical disk herniation and 9 cases of cervical spondylosis. The mean follow-up period was 17.4 months. Surgical levels were C3/4 in 4 cases, C4/5 in 2 cases, C5/6 in 16 cases, and C6/7 in 2 cases. The mean operation time was 138.5 minutes, the amount of intraoperative bleeding was 32.1 ml, and there were no serious intraoperative complications. The range of motion of the affected level increased significantly, from 6.6 degrees preoperatively to 12.2 degrees at final follow-up. No patients required revision surgery at final follow-up, and there were no cases of heterotopic ossification or adjacent segment disease. One patient exhibited radiculopathy due to mild subsidence 1 year after surgery, and 1 had asymptomatic contact of device plates. Preoperative and final JOA scores improved from 11.7 to 15.8 points, and NRS improved from 4.3 to 1.3 points for neck pain and 4.3 to 1.7 points for arm pain. Preoperative and final NDI improved from 39.7% to 14.0%, and EQ-5D improved from 0.602 to 0.801. CONCLUSIONS: The short-term treatment outcomes of Mobi-CⓇ TDR were generally favorable. Spine surgeons should comply with guidelines when introducing this procedure and strive to adopt this new technology in Japan.

Utility of a Computer-assisted Rod Bending System to Avoid Pull-out and Loosening of Percutaneous Pedicle Screws.

STUDY DESIGN: This was a retrospective observational study of a cohort of consecutive patients. OBJECTIVE: To compare the influence of (1) manual and (2) computer-assisted (CA) rod bending techniques on pedicle screw pull-out resulting in loosening during rod reduction and final tightening. SUMMARY OF BACKGROUND DATA: Our recent study showed screw pull-out during rod reduction might be a risk factor for loosening of percutaneous pedicle screws (PPSs) postoperatively, resulting in worse postoperative back pain. We retrospectively analyzed data from 53 consecutive patients who underwent minimally invasive lumbar or thoracic spinal stabilization using intraoperative computed tomography image (CT)-guided navigation with conventional manual rod bending or CA rod bending and were followed up for 1 year. METHOD: Screw pull-out length was measured on axial CT images obtained immediately after screw insertion and postoperatively. Loosening of screws and clinical outcome were evaluated radiographically, clinically, and by CT 1 year after surgery. The frequencies of screw pull-out and screw loosening between the 2 rod bending techniques were compared. Lumbar pain-related factors for both groups of patients were determined preoperatively and 1 year after surgery. RESULTS: Overall, 360 pedicle screws were placed in the manual group and 124 pedicle screws were placed in the CA group. There was no significant difference in the mean age, sex, bone mineral density, mean stabilized length, or smoking habits of patients between the groups. The diameters, lengths, and trajectory angle (axial and sagittal) of the screws placed were not significantly different between the groups. Screw pull-out rate/length and loosening in the CA group was significantly lower than that in the manual group. Postoperative low back pain improved significantly in the CA group compared with that in the manual group. CONCLUSION: CA bending is useful to avoid PPS pull-out during rod reduction and screw loosening postoperatively. CA bending is useful to avoid PPS pull-out during rod reduction and screw loosening postoperatively. This result might have been a factor leading to reduced postoperative back pain in the CA group, however, that future studies are need to investigate this association.

Impact of sufficient contact between the autograft and endplate soon after surgery to prevent nonunion at 12 months following posterior lumbar interbody fusion.

OBJECTIVE: Nonunion after posterior lumbar interbody fusion (PLIF) is associated with poor long-term outcomes in terms of health-related quality of life. Biomechanical factors in the fusion segment may influence spinal fusion rates. There are no reports on the relationship between intervertebral union and the absorption of autografts or vertebral endplates. Therefore, the purpose of this retrospective study was to evaluate the risk factors of nonunion after PLIF and identify preventive measures. METHODS: The authors analyzed 138 patients who underwent 1-level PLIF between 2016 and 2018 (75 males, 63 females; mean age 67 years; minimum follow-up period 12 months). Lumbar CT images obtained soon after the surgery and at 6 and 12 months of follow-up were examined for the mean total occupancy rate of the autograft, presence of a translucent zone between the autograft and endplate (more than 50% of vertebral diameter), cage subsidence, and screw loosening. Complete intervertebral union was defined as the presence of both upper and lower complete fusion in the center cage regions on coronal and sagittal CT slices at 12 months postoperatively. Patients were classified into either union or nonunion groups. RESULTS: Complete union after PLIF was observed in 62 patients (45%), while nonunion was observed in 76 patients (55%). The mean total occupancy rate of the autograft immediately after the surgery was higher in the union group than in the nonunion group (59% vs 53%; p = 0.046). At 12 months postoperatively, the total occupancy rate of the autograft had decreased by 5.4% in the union group and by 11.9% in the nonunion group (p = 0.020). A translucent zone between the autograft and endplate immediately after the surgery was observed in 14 and 38 patients (23% and 50%) in the union and nonunion groups, respectively (p = 0.001). The nonunion group had a significantly higher proportion of cases with cage subsidence and screw loosening at 12 months postoperatively in comparison to the union group (p = 0.010 and p = 0.009, respectively). CONCLUSIONS: A lower occupancy rate of the autograft and the presence of a translucent zone between the autograft and endplate immediately after the surgery were associated with nonunion at 12 months after PLIF. It may be important to achieve sufficient contact between the autograft and endplate intraoperatively for osseous union enhancement and to avoid excessive absorption of the autograft. The achievement of complete intervertebral union may decrease the incidence of cage subsidence or screw loosening.

Key Radiographic Parameters That Influence the Improvement of Postoperative Gastroesophageal Reflux Disease in Patients Treated Surgically for Adult Spinal Deformity With a Minimum 2-Year Follow-up.

STUDY DESIGN: Retrospective observational study. OBJECTIVE: The study objectives were to: (1) determine radiographically which spinal malalignment parameters predominantly influence the risk of gastroesophageal reflux disease (GERD); (2) evaluate the outcome of GERD 2 years after surgery for adult spinal deformity (ASD); and (3) clarify key factors that influence the improvement of postoperative GERD in ASD. SUMMARY OF BACKGROUND DATA: Spinal deformity is reported to be involved in the pathology of GERD. Our previous study found that approximately 50% of patients treated surgically for ASD had GERD symptoms. However, the postoperative progress of GERD and the key factors that influence the improvement of postoperative GERD are largely unknown. METHODS: Ninety-two patients with ASD treated with thoracolumbar corrective surgery and followed up for a minimum of 2 years were enrolled. All patients were asked to complete the Frequency Scale for Symptoms of GERD (FSSG) questionnaire preoperatively and at 1 and 2 years after surgery. GERD was diagnosed by FSSG score more than 8 points. Before, and at 1 and 2 years after surgery, full-length lateral radiographs were taken and radiographic parameters were obtained. RESULTS: Patients were classified into two groups based on GERD symptoms, with 47 (51.1%) in the GERD+ group. Among parameters assessed, only thoracolumbar kyphosis (TLK) was significantly greater in the GERD+ group than in the GERD- group. The FSSG score improved significantly 1 year after surgery, but no significant difference was found between groups at 2 years. A significant correction loss of TLK was observed 2 years after surgery. There was a significant highly positive correlation between the FSSG score and TLK at 2 years after surgery. CONCLUSION: GERD improved with correction of the spinal deformity but significant correction loss of the TLK even within the fusion presumably due to subsidence or proximal junctional kyphosis resulted in a cessation of that improvement over time. LEVEL OF EVIDENCE: 3.

Indications and limitations of minimally invasive lateral lumbar interbody fusion without osteotomy for adult spinal deformity.

PURPOSE: The global alignment and proportion (GAP) score was recently developed to consider proportional analysis of spinopelvic alignment and has been indicated for setting surgical goals to decrease the prevalence of mechanical complications. The goal of this study was to clarify the limitations and problems with spinal corrective surgery with minimally invasive lateral lumbar interbody fusion (LLIF) without osteotomy using GAP score, and to establish a preoperative radiographical evaluation to understand the necessity for three-column osteotomy. METHODS: We included data from 57 consecutive patients treated with spinal corrective surgery with LLIF and without Schwab grade 3-6 osteotomy for ASD. To evaluate flexibility of the pelvis and lumbar spine, we examined full-length lateral radiographs with patients standing and prone. Correlations between pre- and postoperative radiographic parameters and GAP score were determined. RESULTS: Most patients achieved a sufficiently ideal lumbar lordosis (87.7%), but ideal sacral slope (SS) was achieved in only 50.8% of patients. Preoperative prone SS showed a significant positive correlation with postoperative SS and a significant negative correlation with GAP score. Patients whose preoperative prone SS was larger than pelvic incidence × 0.59-7.5 tended to achieve proportioned spinopelvic alignment by using LLIF. CONCLUSIONS: The cause of poor outcome of GAP score for ASD corrective surgery with LLIF without osteotomy is a postoperative small SS. Preoperative prone SS is useful for predicting postoperative SS. When preoperative SS in prone patients is relatively small to ideal as calculated using PI, osteotomy or other correctors should be considered to achieve satisfactory spinopelvic parameters. LEVEL OF EVIDENCE: III. These slides can be retrieved under Electronic Supplementary Material.

Weekly Teriparatide Versus Bisphosphonate for Bone Union During 6 Months After Multi-Level Lumbar Interbody Fusion for Osteoporotic Patients: A Multicenter, Prospective, Randomized Study.

STUDY DESIGN: Multicenter, prospective randomized study. OBJECTIVE: Evaluate the impact of weekly teriparatide (WT) and bone contact (BC) status of grafted bone in patients recovering from multilevel lumbar interbody fusion (M-LIF). SUMMARY OF BACKGROUND DATA: WT has been reported to significantly improve bone fusion following posterior or transforaminal interbody fusion in osteoporosis patients. METHODS: Patients older than 50 years and osteoporotic were recruited. We defined the fusion of two or more consecutive intervertebral levels as M-LIF. All patients were instrumented with pedicle, iliac, or S-2 alar iliac screws after transplanting cages and autogenous bone between vertebral bodies. After surgical indication for M-LIF, the subjects were randomly allocated to receive either subcutaneous WT from 1 week to 6 months postoperatively (WT arm, N = 50) or a bisphosphonate (BP; BP arm, N = 54). Blinded radiological evaluations were performed using computed tomography (CT). Evaluation of bone fusion was performed at the intervertebral disc located at the bottom of the fixed range. The degree of bone fusion was calculated as a score from 2 to 6 points, with 2 defined as complete fusion. Bone fusion rate was also compared at 6 months postoperatively based on BC status of the grafted bone on CT immediately after surgery. RESULTS: Mean bone fusion score at 6 months postoperatively was 3.9 points in the WT group and 4.2 points in the BP group. The bone fusion rate at 6 months postoperatively tended to be higher in the WT group (46.8% vs. 32.7% in the BP group). The 6-month postoperative fusion rate of immediately postoperative of BC+ patients was significantly higher than that of BC- patients (47.4% vs. 9.5%). CONCLUSION: In M-LIF, there were no significant differences in bone fusion score between WT- and BP-treated patients. In contrast, BC status immediately postoperatively had a major impact on 6-month bone fusion. LEVEL OF EVIDENCE: 1.

Risk Factors and Assessment Using an Endoscopic Scoring System for Early and Persistent Dysphagia After Anterior Cervical Decompression and Fusion Surgery.

STUDY DESIGN: Prospective study. OBJECTIVES: Preoperative and postoperative dysphagia was evaluated by an otolaryngology doctor and a speech-language-hearing therapist using the eating assessment tool (EAT-10) and Hyodo-Komagane scores. The objective was to achieve a more precise evaluation of the incidence and risk factors of early and persistent dysphagia after anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Although numerous reports have explored the risk factors for dysphagia after ACDF, these factors remain controversial. The main reason for this situation is that the methods for evaluating dysphagia are not adequate or uniform. MATERIALS AND METHODS: This study involved a retrospective 47 consecutive patients who had undergone ACDF and been followed up for at least 1 year. Sagittal alignment of the cervical spine was evaluated by a preoperative x-ray. Univariate and multivariate logistic regression analyses were performed to determine risk factors for transient or persistent dysphagia. RESULTS: The study showed that 34% of patients developed dysphagia in the early postoperative period and that 25.5% of patients still had persistent dysphagia 1 year postoperatively. 8.5% of patients had already developed dysphagia preoperatively, with a significant positive correlation observed between preoperative and postoperative dysphagia.Aging and smoking were significant risk factors for transient dysphagia. A preoperative cervical kyphotic angle at the C3/C4, C4/C5 disk-level and change in the kyphotic angle at C4/C5 during surgery were significant risk factors of persistent dysphagia 1 year after surgery. CONCLUSIONS: This is the first study to show dysphagia after anterior cervical spine surgery using the EAT-10 score and Hyodo-Komagane score with endoscopic evaluation. Aging and smoking were significant risk factors for transient dysphagia, while preoperative local kyphosis angles of C3-C4 and C4-C5 and change in the kyphotic angle at C4/C5 during surgery may be a key alignment of risk factors for postoperative persistent dysphagia. LEVEL OF EVIDENCE: Level: III.

Predictors and Clinical Importance of Postoperative Coronal Malalignment After Surgery to Correct Adult Spinal Deformity.

STUDY DESIGN: A retrospective observational study of a cohort of consecutive patients. OBJECTIVE: The objective of this study was to determine the correlations between clinical outcomes of spinal surgery to correct adult spinal deformity (ASD) including mechanical complications and coronal malalignment and clarify the risk factors for postoperative coronal malalignment. SUMMARY OF BACKGROUND DATA: Despite the coronal malalignment seen regularly in adult patients who have undergone spinal surgery to correct spinal deformity, the associations between coronal malalignment, and clinical outcomes including mechanical complications after the surgery have remained unclear until now. To understand the associations between coronal malalignment and outcomes of surgery to correct ASD, and risk factors for postoperative coronal malalignment has substantial clinical importance. MATERIALS AND METHODS: We included data from 121 consecutive patients who had undergone spinal surgery to correct ASD and were followed up for a minimum of 2 years. Iliac screws were used for pelvic fixation in all cases. The coronal balance was defined as the horizontal distance between the midpoint of C7 and the center of the sacrum on the coronal plane, and coronal malalignment was defined as when the absolute coronal balance was >20 mm. Preoperative radiographic parameters, surgical features, and clinical outcomes including mechanical complications were compared between groups of patients with coronal balance and those with malalignment. Univariate and multivariate regression analysis were used to clarify risk factors for postoperative coronal malalignment. RESULTS: Postoperative coronal malalignment had no significant association with the clinical outcome as evaluated by a Roland-Morris Disability Questionnaire and Oswestry Disability Index but had a significant association with the frequency of rod fracture. A large preoperative coronal imbalance (malalignment), L5 coronal tilt angle, and use of lateral lumbar interbody fusion were found as risk factors for postoperative coronal malalignment. CONCLUSION: Postoperative coronal malalignment had no significant association with the clinical outcome as evaluated by the Oswestry Disability Index and Roland-Morris Disability Questionnaire but was significantly associated with the frequency of rod fracture. LEVEL OF EVIDENCE: Level III.

Potential Role of Paraspinal Musculature in the Maintenance of Spinopelvic Alignment in Patients With Adult Spinal Deformities.

STUDY DESIGN: A retrospective observational study. OBJECTIVES: To (1) compare skeletal muscle mass index (SMI) and the composition of paraspinal muscles between patients with lumbar spinal stenosis (LSS) and adult spinal deformity (ASD) who underwent spinal surgery, (2) determine whether paraspinal muscles influence low back pain in ASD, and (3) ascertain which radiographic spinal parameters of ASD are predominantly influenced by paraspinal muscles. SUMMARY OF BACKGROUND DATA: Relative muscle cross-sectional area (rmCSA; total CSA minus intramuscular fat CSA) determined using magnetic resonance imaging (MRI) is useful when evaluating not only muscle volume but also muscle quality. Currently, no study has examined paraspinal muscles using rmCSAs to determine which radiographic spinopelvic parameters identified in patients with severe spinal deformities make them candidates for thoracolumbar corrective surgery. MATERIALS AND METHODS: Paraspinal muscle rmCSAs were calculated using preoperative T2-weighted MRIs at the L3/4 axial level. Whole-body bone mineral density and lean, soft tissue mass were measured using dual-energy x-ray absorptiometry. SMI was calculated as appendicular (upper and lower limbs) lean, soft tissue mass (kg/m). Correlations between low back pain according to the Roland-Morris Disability Questionnaire, Oswestry Disability Index, spinopelvic parameters, and rmCSA were evaluated for 110 consecutive patients with ASD and 50 consecutive patients with LSS who underwent spinal surgery. RESULTS: There was no significant difference in the total SMI and morbidity rate of sarcopenia between patients with ASD and LSS. A significant negative correlation between Oswestry Disability Index and the rmCSA of the multifidus muscles and the rmCSA of the erector muscles were observed. There was a significant positive correlation between pelvic tilt/sacral slope and multifidus/erector muscles. CONCLUSIONS: Paraspinal muscles evaluated with MRI were more significantly associated with the pathology of ASD compared with appendicular skeletal muscle evaluations with dual-energy x-ray absorptiometry. The present study indicates that multifidus and erector muscles significantly influenced the maintenance of the pelvic alignment. LEVEL OF EVIDENCE: Level III.

Utility and validity of neurite orientation dispersion and density imaging with diffusion tensor imaging to quantify the severity of cervical spondylotic myelopathy and assess postoperative neurological recovery.

BACKGROUND CONTEXT: Predicting postoperative prognosis with preoperative diagnostic imaging has clinical importance. Recent studies have indicated the utility of diffusion tensor imaging (DTI) to quantify the severity of cervical spondylotic myelopathy (CSM) and assess the prognosis of surgical outcomes. However, how to apply DTI to evaluate CSM in a clinical setting is not fully elucidated. Neurite orientation dispersion and density imaging (NODDI) is a model-based practical diffusion-weighted magnetic resonance imaging analysis for estimating specific microstructural features related directly to neuronal morphology. In a prior study, we indicated preoperative NODDI parameters are a promising tool with which to predict neuronal recovery after decompression surgery in patients with CSM with 2 years follow-up. However, the correlation between NODDI parameters and postoperative long-term outcomes and change of parameters over time postoperatively has remained largely unknown. STUDY DESIGN: Retrospective cohort study. PURPOSE: To determine the change of parameters of NODDI and conventional DTI over time, and the relationship between parameters and neurological recovery 2 years after surgery. PATIENT SAMPLE: We included 28 consecutive patients with nontraumatic cervical lesions from CSM who underwent laminoplasty and were followed up for >2 years. Patients underwent magnetic resonance imaging before and approximately 2 weeks, 6 months, and 1 year after surgery. OUTCOME MEASURES: In addition to conventional DTI metrics, we evaluated intracellular volume fraction (ICVF) and orientation dispersion index, which are metrics derived from NODDI. The Japanese Orthopedic Association (JOA) scoring system was used before and 2 years after surgery to assess neurological outcome (JOA recovery rate). METHODS: NODDI and conventional DTI values were measured at the C2-C3 intervertebral level (control value) and the most compressed levels (C3-C7 intervertebral levels) were measured by 3 observers. The changes of these values from preoperatively, 2 weeks after surgery, 6 months after surgery, and 1 year after surgery, were determined. The correlations between preoperative neurological severity, postoperative neuronal recovery, and preoperative DTI or NODDI metrics were determined. No financial or material support was obtained for this study. There is no conflict of interest. RESULTS: The preoperative ICVF and fractional anisotropy at the most compressed level were significantly less than the preoperative values at the control C2-C3 intervertebral level and fractional anisotropy at the most compressed level was increased in the immediate postoperative period. By contrast, ICVF at the most compressed level was not increased in the immediate postoperative period and a significant increase was observed at 6 months after surgery. Preoperative ICVF was significantly correlated with JOA recovery rate at 2 years after surgery. CONCLUSIONS: NODDI is a reproducible and reliable method for evaluation of CSM. ICVF improved after surgery and recovery of physical findings accompanied this change. ICVF may be applied clinically to predict postoperative recovery.

Surgical Outcomes of Long Fusion Using Dual Iliac Screws Bilaterally for Adult Spinal Deformities: The Effect on the Loosening Rate and Sacroiliac Joint Correction.

INTRODUCTION: We recently demonstrated that pelvic incidence (PI) decreases after long fusion using iliac screws (ISs) and plays a role in good sagittal balance postoperatively. By contrast, the IS loosening rate may cause reversion, increasing the PI and causing loss of sagittal balance. The aim of this study was to determine the effect of the number of ISs inserted into the iliac bone for long fusion to correct adult spinal deformities (ASDs) on the frequency of IS loosening, postoperative PI, and surgical outcomes. METHODS: We included data from 70 consecutive patients. Cases in which two ISs were inserted bilaterally comprised the dual IS group (Group D), whereas cases in which one IS was inserted bilaterally comprised the single IS group (Group S). RESULTS: IS loosening was observed in four patients in Group D (9%) and 14 patients in Group S (61%). Both early and one-year postoperative PI were significantly smaller in Group D (P < 0.001). The sagittal vertical axis (SVA) one-year postoperatively was significantly smaller in Group D (P = 0.003). CONCLUSIONS: The loosening rate of dual ISs was as low as about one-seventh that of single ISs. Using dual ISs, postoperative PI can be kept small, possibly resulting in a smaller SVA.

Risk Factors for Clinically Relevant Loosening of Percutaneous Pedicle Screws.

INTRODUCTION: (1) To evaluate the influence of pedicle screw loosening on clinical outcomes; (2) to clarify the association between the pull-out length and screw loosening 1 year after surgery; and (3) to determine radiographically which screw parameters predominantly influence the pull-out resistance of screws. METHODS: We analyzed 32 consecutive patients who underwent minimally invasive lumbar or thoracic spinal stabilization by intraoperative three-dimensional computed tomography (CT)-guided navigation without anterior reconstruction and were followed up for 1 year. The screw pull-out length was measured on axial CT images obtained both immediately after screw insertion and postoperatively. Loosening of screws and clinical outcomes were evaluated radiographically, clinically, and by CT 1 year after surgery. RESULTS: There were no significant differences in the mean age, sex, bone mineral density, mean stabilized length, and smoking habits of patients with (+) or without (-) loosening. The Oswestry Disability Index and the lumbar visual analog scale 1 year after surgery were significantly higher in patients with loosening (+) than in those without (-). The overall pedicle screw pull-out rate was 16.2% (47/290) of screws and the overall screw loosening rate was 15.2% (44/290) of screws. Screws with loosening (+) had significantly lower (axial) trajectory angles and higher screw pull-out lengths than those without (-). Approximately 82% of loosened screws had been pulled out during rod connection. CONCLUSIONS: A lower axial trajectory and an increased screw pull-out length after rod reduction are crucial risk factors for screw loosening.

New Intramuscular Electromyographic Monitoring with a Probe in Lateral Lumbar Interbody Fusion Surgery.

INTRODUCTION: The lateral lumbar interbody fusion (LLIF) surgical approach is minimally invasive and safely accesses the target region. Therefore, it is widely used in cases of lumbar spinal stenosis and spinal deformity. Intraoperative neuromonitoring is necessary to avoid nerve injury, whereas postoperative anterior thigh symptoms are not necessarily prevented. TECHNICAL NOTE: In our institute, 85 LLIF operations have been performed. The first 30 cases were excluded from the present study to avoid surgical learning curve effects; conventional monitoring was used in 30 cases, whereas a new method with a probe to monitor intramuscular potential was used in 25 other cases. Anterior thigh symptoms and motor deficits were assessed postoperatively. The location of the electromyographic threshold decrease was at the posterior part of the disc at L2-3, but at the anterior part at L4-5. Compared with conventional monitoring, the new intramuscular monitoring significantly decreased the prevalence of motor deficits of the iliopsoas at 1 day and 30 days; anterior thigh pain at 1 day, 30, and 90 days; and anterior thigh numbness at 30 and 90 days postoperatively. CONCLUSIONS: Compared with conventional monitoring, the new intramuscular monitoring with a less invasive probe may reduce anterior thigh symptoms.

Upper instrumented vertebra to the right of the lowest instrumented vertebra as a predictor of an increase in the main thoracic curve after selective posterior fusion for the thoracolumbar/lumbar curve in Lenke type 5C adolescent idiopathic scoliosis: multicenter study on the relationship between fusion area and surgical outcome.

OBJECTIVE: Unfused main thoracic (MT) curvatures occasionally increase after selective thoracolumbar/lumbar (TL/L) fusion. This study sought to identify the predictors of an unacceptable increase in MT curve (UIMT) after selective posterior fusion (SPF) of the TL/L curve in patients with Lenke type 5C adolescent idiopathic scoliosis (AIS). METHODS: Forty-eight consecutive patients (44 females and 4 males, mean age 15.7 ± 2.5 years, range 13-24 years) with Lenke type 5C AIS who underwent SPF of the TL/L curve were analyzed. The novel "Shinshu line" (S-line) was defined as a line connecting the centers of the concave-side pedicles of the upper instrumented vertebra (UIV) and lowest instrumented vertebra (LIV) on preoperative radiographs. The authors established an S-line tilt to the right as S-line positive (S-line+, i.e., the UIV being to the right of the LIV) and compared S-line+ and S-line- groups for thoracic apical vertebral translation (T-AVT) and MT Cobb angle preoperatively, early postoperatively, and at final follow-up. The predictors for T-AVT > 20 mm at final follow-up were evaluated as well. T-AVT > 20 mm was defined as a UIMT. RESULTS: Among the 48 consecutively treated patients, 26 were S-line+ and 22 were S-line-. At preoperative, early postoperative, and final follow-up a minimum of 2 years later, the mean T-AVT was 12.8 mm (range -9.3 to 32.8 mm), 19.6 mm (range -13.0 to 41.0 mm), and 22.8 mm (range -1.9 to 68.7 mm) in the S-line+ group, and 10.8 mm (range -5.1 to 27.3 mm), 16.2 mm (range -11.7 to 42.1 mm), and 11.0 mm (range -6.3 to 26.9 mm) in the S-line- group, respectively. T-AVT in S-line+ patients was significantly larger than that in S-line- patients at the final follow-up. Multivariate analysis revealed S-line+ (odds ratio [OR] 23.8, p = 0.003) and preoperative MT Cobb angle (OR 7.9, p = 0.001) to be predictors of a UIMT. CONCLUSIONS: S-line+ was defined as the UIV being to the right of the LIV. T-AVT in the S-line+ group was significantly larger than in the S-line- group at the final follow-up. S-line+ status and larger preoperative MT Cobb angle were independent predictors of a UIMT after SPF for the TL/L curve in patients with Lenke type 5C AIS. Surgeons should consider changing the UIV and/or LIV in patients exhibiting S-line+ during preoperative planning to avoid a possible increase in MT curve and revision surgery.