Early and Late Reoperation Rates With Various MIS Techniques for Adult Spinal Deformity Correction.

Study designA multicenter retrospective review of an adult spinal deformity database.ObjectiveWe aimed to characterize reoperation rates and etiologies of adult spinal deformity surgery with circumferential minimally invasive surgery (cMIS) and hybrid (HYB) techniques.MethodsInclusion criteria were age ≥18 years, and one of the following: coronal Cobb >20°, sagittal vertical axis >5 cm, pelvic tilt >20°, and pelvic incidence-lumbar lordosis >10°. Patients with either cMIS or HYB surgery, ≥3 spinal levels treated with 2-year minimum follow-up were included.ResultsA total of 133 patients met inclusion for this study (65 HYB and 68 cMIS). Junctional failure (13.8%) was the most common reason for reoperation in the HYB group, while fixation failure was the most common reason in the cMIS group (14.7%). There was a higher incidence of proximal junctional failure (PJF) than distal junctional failure (DJF) within HYB (12.3% vs 3.1%), but no significant differences in PJF or DJF rates when compared to cMIS. Early (<30 days) reoperations were less common (cMIS = 1.5%; HYB = 6.1%) than late (>30 days) reoperations (cMIS = 26.5%; HYB = 27.7%), but early reoperations were more common in the HYB group after propensity matching, largely due to infection rates (10.8% vs 0%, P = .04).ConclusionsAdult spinal deformity correction with cMIS and HYB techniques result in overall reoperation rates of 27.9% and 33.8%, respectively, at minimum 2-year follow-up. Junctional failures are more common after HYB approaches, while pseudarthrosis/fixation failures happen more often with cMIS techniques. Early reoperations were less common than later returns to the operating room in both groups, but cMIS demonstrated less risk of infection and early reoperation when compared with the HYB group

Magnons and magnetic fluctuations in atomically thin MnBi2Te4

MnBi2Te4, referred to as MBT, is a van der Waals material combining topological electron bands with magnetic order. Here, Lujan et al study collective spin excitations in MBT, and show that magnetic fluctuations increase as samples reduce in thickness, implying less robust magnetic order. Electron band topology is combined with intrinsic magnetic orders in MnBi2Te4, leading to novel quantum phases. Here we investigate collective spin excitations (i.e. magnons) and spin fluctuations in atomically thin MnBi2Te4 flakes using Raman spectroscopy. In a two-septuple layer with non-trivial topology, magnon characteristics evolve as an external magnetic field tunes the ground state through three ordered phases: antiferromagnet, canted antiferromagnet, and ferromagnet. The Raman selection rules are determined by both the crystal symmetry and magnetic order while the magnon energy is determined by different interaction terms. Using non-interacting spin-wave theory, we extract the spin-wave gap at zero magnetic field, an anisotropy energy, and interlayer exchange in bilayers. We also find magnetic fluctuations increase with reduced thickness, which may contribute to a less robust magnetic order in single layers.We thank Chao Lei, B. Wieder, A. Ernst, and M. G. Vergniory for helpful discussions. This research was primarily supported by the National Science Foundation through the Center for Dynamics and Control of Materials: an NSF MRSEC under Cooperative Agreement No. DMR-1720595, which also supported the facility used in sample preparation. Additional support from NSF DMR-1949701 and DMR-2114825 is gratefully acknowledged by G.A.F. This work was performed in part at the Aspen Center for Physics, which is supported by the National Science Foundation grant PHY-1607611. A.L. acknowledges support from the funding grant: PID2019-105488GB-I00. Z.Y. and R.H. acknowledge support by the NSF CAREER Grant No. DMR-1760668 and NSF Grant No. DMR-2104036. X.L. gratefully acknowledges the Welch Foundation grant F-1662 for support in sample preparation. Work at ORNL was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. M. R-V. was supported by LANL LDRD Program and by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, Condensed Matter Theory Program. L.-J.C. and S.-F.L. were primarily funded by the Ministry of Science and Technology 105-2112-M-001-031-MY3 in Taiwan, and the collaboration with UT-Austin is facilitated by the Air Force Office of Scientific Research under award number FA2386-21-1-4067. Partial funding for L.-J.C. while visiting UT-Austin was provided by a Portugal-UT collaboration grant

Early and Late Reoperation Rates With Various MIS Techniques for Adult Spinal Deformity Correction

Study designA multicenter retrospective review of an adult spinal deformity database.ObjectiveWe aimed to characterize reoperation rates and etiologies of adult spinal deformity surgery with circumferential minimally invasive surgery (cMIS) and hybrid (HYB) techniques.MethodsInclusion criteria were age ≥18 years, and one of the following: coronal Cobb >20°, sagittal vertical axis >5 cm, pelvic tilt >20°, and pelvic incidence-lumbar lordosis >10°. Patients with either cMIS or HYB surgery, ≥3 spinal levels treated with 2-year minimum follow-up were included.ResultsA total of 133 patients met inclusion for this study (65 HYB and 68 cMIS). Junctional failure (13.8%) was the most common reason for reoperation in the HYB group, while fixation failure was the most common reason in the cMIS group (14.7%). There was a higher incidence of proximal junctional failure (PJF) than distal junctional failure (DJF) within HYB (12.3% vs 3.1%), but no significant differences in PJF or DJF rates when compared to cMIS. Early (<30 days) reoperations were less common (cMIS = 1.5%; HYB = 6.1%) than late (>30 days) reoperations (cMIS = 26.5%; HYB = 27.7%), but early reoperations were more common in the HYB group after propensity matching, largely due to infection rates (10.8% vs 0%, P = .04).ConclusionsAdult spinal deformity correction with cMIS and HYB techniques result in overall reoperation rates of 27.9% and 33.8%, respectively, at minimum 2-year follow-up. Junctional failures are more common after HYB approaches, while pseudarthrosis/fixation failures happen more often with cMIS techniques. Early reoperations were less common than later returns to the operating room in both groups, but cMIS demonstrated less risk of infection and early reoperation when compared with the HYB group

A Critical Analysis of Sagittal Plane Deformity Correction With Minimally Invasive Adult Spinal Deformity Surgery: A 2-Year Follow-Up Study

Sagittal plane realignment is important to achieve desirable clinical outcomes after adult spinal deformity (ASD) surgery. This study evaluates the impact of minimally invasive (MIS) techniques on sagittal plane alignment and clinical outcomes in ASD patients. A retrospective, multi-center review of ASD patients (age ≥18 years, and with one of the following: coronal Cobb ≥20°, sagittal vertical axis [SVA] >5 cm, and/or pelvic tilt >25°), MIS surgery, and four or more levels instrumented. Patients were stratified by baseline SRS-Schwab global alignment modifier (GAM) into three groups: 0 (SVA 9.5 cm). Radiographic and clinical outcomes measures were analyzed with a minimum of 2-year follow-up. A total of 96 ASD patients were identified, and 63 met the study's inclusion criteria of circumferential MIS or posterior MIS only, with four or more levels instrumented (n: Group 0 = 37, Group + = 15, and Group ++ = 11). Group 0 was younger than ++ (56.8 vs. 69.6 years), with a higher proportion of females than Group + or ++ (83.8% vs. 66.7% and 54.5%, respectively). Baseline HRQoL was similar. Postoperatively, Groups 0 and + had improved Oswestry Disability Index (ODI) and numeric rating scale (NRS) back and leg scores. Group ++ only had improvement in NRS scores. At the latest follow-up, Groups 0 and ++ had similar sagittal measurements except for PT (21.6 vs. 23.6, p = .009). The + group had improvement in PI–LL (24.2 to 17; p = .015) and LL (30.9 to 38.3; p = .013). Eight of 27 (21.6%) Group 0 patients deteriorated (4 to Group +, 4 to Group ++). Three of 15 (20.0%) Group + patients deteriorated to Group ++, and 3 improved to Group 0. Six of 11 (54.5%) Group ++ patients improved (3 to Group + and 3 to Group 0). MIS techniques successfully stabilized ASD patients with Group 0 and + deformities and improved HRQoL. This study suggests that severe sagittal imbalance is not adequately treated with MIS approaches

Impact of case type, length of stay, institution type, and comorbidities on Medicare diagnosis-related group reimbursement for adult spinal deformity surgery

OBJECTIVE The aim of this study was to educate medical professionals about potential financial impacts of improper diagnosis-related group (DRG) coding in adult spinal deformity (ASD) surgery. METHODS Medicare's Inpatient Prospective Payment System PC Pricer database was used to collect 2015 reimbursement data for ASD procedures from 12 hospitals. Case type, hospital type/location, number of operative levels, proper coding, length of stay, and complications/comorbidities (CCs) were analyzed for effects on reimbursement. DRGs were used to categorize cases into 3 types: 1) anterior or posterior only fusion, 2) anterior fusion with posterior percutaneous fixation with no dorsal fusion, and 3) combined anterior and posterior fixation and fusion. RESULTS Pooling institutions, cases were reimbursed the same for single-level and multilevel ASD surgery. Longer stay, from 3 to 8 days, resulted in an additional $1400 per stay. Posterior fusion was an additional$6588, while CCs increased reimbursement by approximately $13,000. Academic institutions received higher reimbursement than private institutions, i.e., approximately$14,000 (Case Types 1 and 2) and approximately $16,000 (Case Type 3). Urban institutions received higher reimbursement than suburban institutions, i.e., approximately$3000 (Case Types 1 and 2) and approximately $3500 (Case Type 3). Longer stay, from 3 to 8 days, increased reimbursement between$208 and $494 for private institutions and between$1397 and $1879 for academic institutions per stay. CONCLUSIONS Reimbursement is based on many factors not controlled by surgeons or hospitals, but proper DRG coding can significantly impact the financial health of hospitals and availability of quality patient care

167 What Is the Impact of Obesity in MIS vs OPEN Surgery for Adult Spinal Deformity?

Abstract INTRODUCTION: Obesity is a significant comorbidity that can increase the risk and technical difficulty of surgery. Previous studies comparing minimally invasive (MIS) to traditional open spinal surgery in the obese have shown similar clinical outcomes but improved perioperative benefits of decreased estimated blood loss (EBL), length of stay (LOS), and complications with MIS approaches. Similar studies have not been performed for obese patients undergoing surgery for adult spinal deformity (ASD). This study's objective was to compare the impact of obesity in the treatment of ASD with MIS compared with open approaches. METHODS: Two multicenter databases, one involving MIS surgeries and the other open surgeries, were queried. Inclusion criteria for both databases were diagnosis of ASD, minimum 2-year follow-up, and at least 1 of the following parameters: coronal cobb (CC) = 20°, SVA > 5 cm, PT > 25°, thoracic kyphosis > 60°. Patients with body mass index (BMI) = 30 were identified and then propensity matched for levels fused. Thirty-eight patients with 19 in each group were analyzed. RESULTS: Patients were well matched with mean ages of 65.4 and 64.3 years and BMI 34.7 and 34.0, respectively, for the MIS and open groups. Table 1 lists outcomes between the groups. Mean levels fused were 4.2 for MIS and 2.7 for open. Statistically significant improvement in Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) were noted within each group. Notably, there was no significant difference in radiographic parameters or ODI and VAS scores between groups. A significant decrease in EBL was noted in the MIS group; however, complications and reoperation frequency were not statistically different. CONCLUSION: Similar clinical and radiographic improvements were noted for MIS and open treatment of ASD. Although EBL was less in the MIS group, the frequency of complications and reoperations were similar, suggesting the potential benefit of MIS approaches may be mitigated by obesity. Larger comparative studies are needed to clarify the benefit of MIS in the obese undergoing ASD surgery

Role of obesity in less radiographic correction and worse health-related quality-of-life outcomes following minimally invasive deformity surgery

OBJECTIVE Minimally invasive surgery (MIS) for adult spinal deformity (ASD) can offer deformity correction with less tissue manipulation and damage. However, the impact of obesity on clinical outcomes and radiographic correction following MIS for ASD is poorly understood. The goal of this study was to determine the role, if any, that obesity has on radiographic correction and health-related quality-of-life measures in MIS for ASD. METHODS Data were collected from a multicenter database of MIS for ASD. This was a retrospective review of a prospectively collected database. Patient inclusion criteria were age ≥ 18 years and coronal Cobb angle ≥ 20°, pelvic incidence–lumbar lordosis mismatch ≥ 10°, or sagittal vertical axis (SVA) > 5 cm. A group of patients with body mass index (BMI) < 30 kg/m 2 was the control cohort; BMI ≥ 30 kg/m 2 was used to define obesity. Obesity cohorts were categorized into BMI 30–34.99 and BMI ≥ 35. All patients had at least 1 year of follow-up. Preoperative and postoperative health-related quality-of-life measures and radiographic parameters, as well as complications, were compared via statistical analysis. RESULTS A total of 106 patients were available for analysis (69 control, 17 in the BMI 30–34.99 group, and 20 in the BMI ≥ 35 group). The average BMI was 25.24 kg/m 2 for the control group versus 32.46 kg/m 2 (p < 0.001) and 39.5 kg/m 2 (p < 0.001) for the obese groups. Preoperatively, the BMI 30–34.99 group had significantly more prior spine surgery (70.6% vs 42%, p = 0.04) and worse preoperative numeric rating scale leg scores (7.71 vs 5.08, p = 0.001). Postoperatively, the BMI 30–34.99 cohort had worse Oswestry Disability Index scores (33.86 vs 23.55, p = 0.028), greater improvement in numeric rating scale leg scores (−4.88 vs −2.71, p = 0.012), and worse SVA (51.34 vs 26.98, p = 0.042) at 1 year postoperatively. Preoperatively, the BMI ≥ 35 cohort had significantly worse frailty (4.5 vs 3.27, p = 0.001), Oswestry Disability Index scores (52.9 vs 44.83, p = 0.017), and T1 pelvic angle (26.82 vs 20.71, p = 0.038). Postoperatively, after controlling for differences in frailty, the BMI ≥ 35 cohort had significantly less improvement in their Scoliosis Research Society–22 outcomes questionnaire scores (0.603 vs 1.05, p = 0.025), higher SVA (64.71 vs 25.33, p = 0.015) and T1 pelvic angle (22.76 vs 15.48, p = 0.029), and less change in maximum Cobb angle (−3.93 vs −10.71, p = 0.034) at 1 year. The BMI 30–34.99 cohort had significantly more infections (11.8% vs 0%, p = 0.004). The BMI ≥ 35 cohort had significantly more implant complications (30% vs 11.8%, p = 0.014) and revision surgery within 90 days (5% vs 1.4%, p = 0.034). CONCLUSIONS Obese patients who undergo MIS for ASD have less correction of their deformity, worse quality-of-life outcomes, more implant complications and infections, and an increased rate of revision surgery compared with their nonobese counterparts, although both groups benefit from surgery. Appropriate counseling should be provided to obese patients

Can a Minimal Clinically Important Difference Be Achieved in Elderly Patients with Adult Spinal Deformity Who Undergo Minimally Invasive Spinal Surgery?

Older age has been considered a relative contraindication to complex spinal procedures. Minimally invasive surgery (MIS) techniques to treat patients with adult spinal deformity (ASD) have emerged with the potential benefit of decreased approach-related morbidity. To determine whether a minimal clinically important difference (MCID) could be achieved in patients ages ≥65 years with ASD who underwent MIS. Multicenter database of patients who underwent MIS for ASD was queried. Outcome metrics assessed were Oswestry Disability Index (ODI) and visual analog scale (VAS) scores for back and leg pain. On the basis of published reports, MCID was defined as a positive change of 12.8 ODI, 1.2 VAS back pain, and 1.6 VAS leg pain. Forty-two patients were identified. Mean age was 70.3 years; 31 (73.8%) were women. Preoperatively, mean coronal curve, pelvic tilt, pelvic incidence to lumbar lordosis mismatch, and sagittal vertical axis were 35°, 24.6°, 14.2°, and 4.7 cm, respectively. Postoperatively, mean coronal curve, pelvic tilt, pelvic incidence to lumbar lordosis, and sagittal vertical axis were 18°, 25.4°, 11.9°, and 4.9 cm, respectively. A mean of 5.0 levels was treated posteriorly, and a mean of 4.0 interbody fusions was performed. Mean ODI improved from 47.1 to 25.1. Mean VAS back and leg pain scores improved from 6.8 and 5.9 to 2.7 and 2.7, respectively. Mean follow-up was 32.1 months. For ODI, 64.3% of patients achieved MCID. For VAS back and leg pain, 82.9% and 72.2%, respectively, reached MCID. MCID represents the threshold at which patients feel a meaningful clinical improvement has occurred. Our study results suggest that the majority of elderly patients with modest ASD can achieve MCID with MIS