Adult Spinal Deformity Correction Research Articles

Upper instrumented vertebra pedicle screw loosening following adult spinal deformity surgery: incidence and outcome analysis.

Surgical correction of adult spinal deformity (ASD) is associated with a high rate of hardware complication that can be challenging to predict. Hardware integrity and alignment after surgery are typically followed with standing radiography, where pedicle screw loosening may be incidentally identified but the clinical significance of which is often unclear. This study aimed to identify the incidence and implications of pedicle screw loosening at the upper instrumented vertebra (UIV) after surgical correction of ASD. A single-institution retrospective analysis was performed on a cohort of 217 patients who underwent long-segment fusion with pelvic fixation for correction of ASD between September 2013 and November 2021. Cases with a minimum 1-year follow-up were included. UIV pedicle screws were graded on radiographs for evidence of loosening with a 0- to 3-point scale: 0, no loosening; 1, lucency within screw threads; 2, lucency around screw threads; and 3, screw dislodgment/backout. Need for hardware revision surgery was assessed as the primary outcome. Patient-reported outcome measures (PROMIS and Oswestry Disability Index scores) were assessed as secondary outcomes among the patients with available scores. Low-grade UIV screw loosening (grade 1) was identified in 37 patients (17.1%), and high-grade UIV loosening (grade 2 or 3) was identified in 23 patients (10.6%). Low-grade UIV loosening was not associated with eventual need for hardware revision (OR 0.52, 95% CI 0.17-1.61, p = 0.258); however, high-grade loosening was associated with increased odds of hardware revision (OR 5.17, 95% CI 1.74-15.36, p = 0.003), including specifically surgery for correction of proximal junctional kyphosis (OR 5.73, 95% CI 1.27-25.95, p = 0.024). Among patients with PROMIS T-scores, those requiring hardware revision reported worse Pain Interference (65.0 ± 5.1 vs 59.6 ± 7.7, p = 0.001) and Physical Function (33.3 ± 5.6 vs 37.4 ± 7.4; p = 0.011). Patients with high-grade UIV loosening reported higher Oswestry Disability Index scores than those without high-grade loosening (grade 0 or 1), although this failed to reach statistical significance (44.0 ± 8.5 vs 33.7 ± 18.5, p = 0.101). Grade 1 UIV pedicle screw loosening may represent a benign incidental finding, whereas high-grade loosening is associated with significantly increased odds of hardware revision surgery. High-grade loosening may also be associated with worse patient-reported disability. The authors' findings suggest that while low-grade UIV loosening may often be managed expectantly, identification of high-grade UIV pedicle screw loosening on follow-up imaging warrants increased attention and continued surveillance.

Glycemic Laboratory Values Are Associated With Increased Length of Stay and 90-Day Revision Risk Following Surgical Management of Adult Spinal Deformity

Diabetes mellitus (DM) is a common comorbidity among patients undergoing spinal fusion for adult spinal deformity (ASD) surgery. An elevated Hemoglobin A1c (HbA1c) and elevated postoperative glucose have been shown to increase the risk of complications following spine and other orthopaedic surgeries; however, data is limited for ASD. To investigate glycemic control and ASD surgery to inform surgical decision making, medical optimization, and patient education. Retrospective cohort. Total of 106 adult patients undergoing surgical correction for ASD with an HbA1c drawn within six months preoperatively or two weeks postoperatively and valid plasma glucose levels throughout postoperative hospital stay. Length of stay, 90-day wound complication, 90-day readmission, 90-day revision. All patients undergoing spinal fusion of seven or more levels between 2021 and 2023 at two large academic medical centers were identified using institutional data acquisition software. Medical charts were then manually reviewed to obtain and confirm demographic, laboratory, and surgical characteristics and outcomes. Laboratory characteristics included preoperative HbA1c, mean postoperative glucose (PG), and maximum PG. Surgical characteristics and outcomes included procedure time, estimated blood loss (EBL), length of inpatient stay (LOS), transfusion requirement, 90-day complications, 90-day revision, and 90-day readmission. Bivariate analysis was performed followed by simple and multiple regression analysis. Odds ratios were established relative to the laboratory threshold values informed by receiver operating characteristics. Of 872 original procedures identified, 106 patients (12.2%) were adults with preoperative HbA1c and postoperative plasma glucose measurements who underwent surgery for a diagnosis of ASD. Median patient age was 67 years (IQR 59-72 years), 59 (55.7%) were female, and 96 (90.6%) were of Caucasian race. Median LOS was 7 days (IQR 5-10 years) and median HbA1c was 5.9% (IQR 5.3%-6.5%). Higher preoperative HbA1c was correlated with increased LOS (R=0.22, P=0.023). The odds ratio for patients requiring extended LOS was 2.49 (95% CI 1.06-5.86, P=0.034) for those with HbA1c ≥6.3%. Multiple regression analysis of LOS identified HbA1c [B= 1.51 (95% CI 0.32-2.70), P=0.013] as a positive predictor of LOS and mean PG [B= -0.05 (95% CI -0.10-(-0.01), P=0.019] as a weakly negative predictor of LOS. Upon simple logistic regression, the odds ratio for 90-day revision was 1.81 (95% CI 1.02-3.19, P=0.042) for every unit increase in HbA1c. Patients with mean PG ≥165 mg/dL [OR=5.76 (95% CI 1.28-26.01), P=0.024] were at increased risk for 90-day revision. Glycemic laboratory values do not seem to predict 90-day wound complications or 90-day readmission following surgery for ASD. Elevated preoperative HbA1c is associated with increased LOS and risk for revision within 90 days of ASD surgery. Postoperative hyperglycemia is also associated with increased 90-day revision risk. To our knowledge, this study is the first to evaluate HbA1c and outcomes following ASD surgery. These findings can be leveraged to inform preoperative medical optimization and highlight the importance of glycemic control in ASD patients undergoing corrective surgical intervention.

Proximal lumbar anterior column realignment for iatrogenic sagittal plane adult spinal deformity correction: a retrospective case series

Anterior column realignment (ACR) is a powerful minimally invasive surgery (MIS) technique to restore sagittal alignment in adult spinal deformity (ASD). This can accomplish similar segmental lordosis restoration as 3-column osteotomy with less blood loss and comparable complication rates. ACR can be performed at adjacent disease segments in the proximal lumbar spine in revision cases. However, two-thirds of physiologic lordosis occurs between L4-S1, and concerns remain about altered lumbar morphology. We evaluated patients who underwent proximal lumbar ACR for iatrogenic flatback deformity. A total of 19 consecutive patients who underwent L1-2 or L2-3 ACR were retrospectively analyzed. All patients were treated with lateral MIS interbody technique, followed by posterior reconstruction with Smith-Peterson osteotomy (SPO). Pre- and post-operative radiographic and clinical outcomes were obtained. Mean follow-up was 19-months. All but one patient had a history of prior lumbar or lumbo-sacral fusion. SVA and PI-LL decreased from 11.9 cm to 6.1 cm (p<0.0001) and 34.2° to 12.8° (p<0.0001). Segmental lordosis increased from -2.7° to 21.9° (p<0.0001). Proximal lumbar lordosis (PLL) increased from -0.4° to 22.6° (p<0.0001), and lordosis distribution index (LDI) decreased from 79.5% to 48.9% (p<0.0001). Mean ODI and NPRS back pain decreased from 58.0 to 36.2 (p=0.0041) and 7.9 to 3.4 (p<0.0001). PROMIS-10 Physical and Mental Health T-scores increased from 34.1 to 43.3 (p=0.0049) and 40.4 to 45.0 (p=0.0993). Major complication rate was 15.8%. One patient required revision for mechanical failure. There were no permanent neurological or vascular injuries. Proximal lumbar ACR plus SPO can achieve sagittal correction with low major complication rates in patients with ASD and prior distal fusion. Differentially increasing PLL and lowering LDI did not have deleterious effects on radiographic or clinical outcomes. Further work is needed to understand the effect of proximal ACR in the surgical management of ASD.

Determining the utility of three-column osteotomies in revision surgery compared with primary surgeries in the thoracolumbar spine: a retrospective cohort study in the United States.

Retrospective cohort study. To determine the incidence and success of three-column osteotomies (3COs) performed in primary and revision adult spine deformity (ASD) corrective surgeries. 3COs are often required to correct severe, rigid ASD presentations. However, controversy remains on the utility of 3COs, particularly in primary surgery. Patients ASD having 2-year data were included and divided into 3CO and non-3CO (remaining ASD cohort) groups. For the subanalysis, patients were stratified based on whether they were undergoing primary (P3CO) or revision (R3CO) surgery. Multivariate analysis controlling for age, Charlson comorbidity index, body mass index, baseline pelvic incidence-lumbar lordosis, and fused levels evaluated the complication rates and radiographic and patient-reported outcomes between the 3CO and non-3CO groups. Of the 436 patients included, 20% had 3COs. 3COs were performed in 16% of P3COs and 51% of R3COs. Both 3CO groups had greater severity in deformity and disability at baseline; however, only R3COs improved more than non-3COs. Despite greater segmental correction, 3COs had much lower rates of aligning in the lumbar distribution index (LDI), higher mechanical complications, and more reoperations when performed below L3. When comparing P3COs and R3COs, baseline lumbopelvic and global alignments, as well as disability, were different. The R3CO group had greater clinical improvements and global correction (both p<0.04), although the P3CO group achieved alignment in LDI more often (odds ratio, 3.9; 95% confidence interval, 1.3-6.2; p=0.006). The P3CO group had more neurological complications (30% vs. 13%, p=0.042), whereas the R3CO tended to have higher mechanical complication rates (25% vs. 15%, p=0.2). 3COs showed greater improvements in realignment while failing to demonstrate the same clinical improvement as primaries without a 3CO. Overall, when suitably indicated, a 3CO offers superior utility for achieving optimal realignment across primary and revision surgeries for ASD correction.

Prevalence and Clinical Impact of Coronal Malalignment Following Circumferential Minimally Invasive Surgery (CMIS) for Adult Spinal Deformity Correction.

Retrospective study. To determine prevalence and clinical importance of patients who had postoperative CM after CMIS for ASD correction. We reviewed patients who underwent CMIS technique. Inclusion criteria were patients who were diagnosed with ASD, which is defined as having at least one of the following: coronal Cobb angle >20, SVA >50mm, PI-LL >10, PT >20. They underwent >4 spinal levels fusion with CMIS technique and had at least 1-year follow-up. Preoperative and 1-year postoperative radiographs and clinical outcome measures (VAS, ODI, and SRS-22 scores) were used to make the comparisons. 120 patients were included. Radiographic outcomes, including CVA, coronal Cobb angle, LSF curve, SVA, LL, and PI-LL, and clinical outcomes, were significantly improved postoperatively in each of the 3 preoperative subgroups (Bao type A, B, and C). At 1-year post-operation, 10 patients (12.4 %) of type A turned out to be CM, 4 patients (21.1%) of type B, and 8 patients (40%) of type C remained CM. Comparing coronally aligned (CA) to coronally mal-aligned patients at 1-year follow-up in each coronal subtype revealed that clinical and radiographic outcomes were comparable. CMIS technique significantly improves radiographic and clinical outcomes for ASD patients. Incidence rates of postoperative CM were similar to open surgery. Type C patients were at risk of postoperative CM than types A and B. However, most 1-year outcomes were not significantly different between postoperative CA and CM patients regardless of the preoperative coronal alignment characteristics except ODI scores in type A.

T1 Pelvic and Lumbar Pelvic Angles Normative Values: A Prospective Cohort Study of 472 Asymptomatic Volunteers.

Cross-sectional analysis of a prospectively enrolled cohort. Determine the normative values of the T1 Pelvic Angle (TPA) and Lumbar Pelvic Angle (LPA) in an asymptomatic cohort of volunteers. The TPA and LPA have been introduced as sagittal spino-pelvic parameters to guide correction of adult spinal deformity. Suggested values for these parameters were derived from linear regressions based on Oswestry Disability Index scores from adult spinal deformity patients. While a few studies have evaluated the normative value of TPA, none have evaluated the LPA in asymptomatic individuals. TPA and LPA were measured on radiographs of 472 asymptomatic volunteers between 20 and 40 years old. TPA and LPA were calculated as originally described from the centroid of T1 and L1 respectively, to the center of the femoral head to the midpoint of the sacral endplate. TPA and LPA were also evaluated using the midpoint of the superior endpoint as a surrogate to the centroid of the vertebra to compare these two measurement techniques. TPA and LPA normative values were respectively 7.3 [6.8-7.8] and 6.3o [5.9-6.7]. There was no statistically significant difference between using the centroid of T1 or L1 versus using the midpoint of the superior endplate with respective results of 7.5o [7.0-8.0] (P=0.55) and 6.1o [5.6-6.5] (P=0.43). TPA was significantly different between Roussouly types 1-2-3 versus type 4 with respective results of of 6.7o, 7.2o, 6.5o and 9.2o (P<0.001). The same difference was observed for the LPA with normative results of 3.8o, 5.1o, 5.8o and 9.3o (P<0.001), respectively, for Roussouly types 1,2,3 and 4. TPA and LPA normative values are 7o and 6o, respectively, and vary between Roussouly morphotypes 1,2 and 3 versus type 4. Using the midpoint of the superior endplate of T1 and L1 versus the centroid yielded similar results and therefore could be easier to use intraoperatively.

52. Limiting blood loss and estimating cell salvage volume for return in adult spinal deformity correction

52. Limiting blood loss and estimating cell salvage volume for return in adult spinal deformity correction

116. Machine learning clustering of preoperative fitness and its prognostic value following adult spinal deformity correction

116. Machine learning clustering of preoperative fitness and its prognostic value following adult spinal deformity correction

P123. Determinants of cost-effectiveness in minimally invasive surgery for adult spinal deformity correction

P123. Determinants of cost-effectiveness in minimally invasive surgery for adult spinal deformity correction

Return to sporting activities following long fusions to the pelvis in adult spinal deformity

Returning to recreational sporting activities after adult spinal deformity (ASD) correction may significantly impact the patient's perceived quality of life. This study sought to characterize participation in sporting activities before and after ASD surgery, and to identify factors associated with impaired return to sports. Cross-sectional survey and retrospective review of prospectively collected data. Patients who underwent posterior-only thoracolumbar ASD surgery between 2016 and 2021 with ≥1 year follow-up and ≥3 levels of fusion to the pelvis were included. Preoperative and postoperative participation in sports, timing of return to these activities, and reasons for limited sports participation postoperatively were assessed. A survey was used to evaluate outcome measures. Differences in demographic, surgical, and perioperative variables between patients who reported improved, unchanged, or worsened activity tolerance were evaluated. Ninety-five patients were included (mean age: 64.3±10.1 years; BMI: 27.3±6.1 kg/m2; median levels fused: 7). The survey was completed at an average of 43.5±15.9 months after surgery. Sixty-eight (72%) patients participated in sports preoperatively. The most common sports were swimming (n=33, 34.7%), yoga (n=23, 24.2%), weightlifting (n=20, 21.1%), elliptical (n=19, 20.0%), and golf (n=11, 11.6%). Fifty-seven (83.8%) returned to at least one sport postoperatively, most commonly 6-12 months after surgery (45%). Elliptical had the highest rate of equal or improved participation (53%). Patients generally returned below their preoperative level to all other sports. Reasons for reduced sporting activities included physical limitation (51.4%), fear (20.0%), pain (17.1%), and surgeon advice (8.6%). There were no differences in the demographic, surgical, or perioperative characteristics between those who returned to sports at the same or better level compared with those who returned at a lower level. About 84% of patients successfully resumed sporting activities after undergoing fusion to the sacrum/pelvis for ASD. However, this return is typically at a lower level of participation than their preoperative participation, particularly in higher demand sports. Understanding trends in sporting activity may be valuable for counseling patients and setting expectations.

Correlation between Acetabular Anteversion with a False-Profile View and Spinopelvic Parameters in Adult Spinal Deformity after Long-Segment Corrective Spinal Surgery.

Studies describing the relationship between the hip and spine have reported that corrective spinal surgery for adult spinal deformity (ASD) affects the orientation of the acetabulum. However, the extent to which spinal correction in ASD affects acetabular anteversion in the standing position is unclear, especially after total hip arthroplasty, for which dislocation is a concern. The purpose of this study was to evaluate changes in anterior acetabular coverage in the upright position due to extensive correction surgery for ASD. Thirty-six consecutive patients who had undergone spinal corrective surgery from the thoracolumbar region to the pelvis were enrolled and evaluated. The ventral-central-acetabular (VCA) angle and anterior acetabular head index (AAHI) were measured with a false-profile view to evaluate the relationship between acetabular anteversion in the standing position and spinopelvic parameters before and after surgery. The spinopelvic parameters measured included thoracic kyphosis, pelvic incidence, pelvic tilt (PT), sacral slope, lumbar lordosis (LL), sagittal vertical axis, and global tilt. The VCA angle and AAHI were significantly increased after spinal deformity correction (p<0.001). The changes in LL and PT were correlated with the VCA angle (LL: right, ρ=0.56; left, ρ=0.55, p<0.001; PT: right, ρ=-0.59; left, ρ=-0.64, p<0.001) and AAHI (LL: right, ρ=0.51; left, ρ=0.58, p<0.01; PT: right, ρ=-0.52; left, ρ=-0.59, p<0.01), respectively. Linear regression analysis revealed that a 10° increase in LL results in 1.4°-1.9° and 1.6%-2% increases in the VCA angle and AAHI, respectively. Surgical correction for ASD significantly affects sagittal spinopelvic parameters, resulting in increased acetabular anteversion. The anterior coverage of the acetabulum in the postoperative standing position could be predicted with the intraoperatively measured LL, and evaluation using a false-profile was considered useful for treating ASD, particularly in patients after total hip arthroplasty.

Staged Versus Same-Day Surgery in Circumferential Minimally Invasive Deformity Correction.

We sought to compare long-term clinical and radiographic outcomes in patients who underwent staged vs same-day circumferential minimally invasive surgery (cMIS) for adult spinal deformity (ASD). We reviewed staged and same-day cMIS ASD cases in a prospective multi-institution database to compare preoperative and 2-year clinical and radiographic parameters between cohorts. A total of 85 patients with a 2-year follow-up were identified (27 staged, 58 same-day). Staged patients had more extensive surgeries and greater hospital length of stay (all P < .001). There were no significant differences in preoperative or 2-year postoperative clinical metrics between cohorts. Patients in the staged cohort also had greater preoperative coronal deformity and thus experienced greater reduction in coronal deformity at 2 years (all P < .01). Patients undergoing staged or same-day cMIS correction had similar outcomes at 2 years postoperatively. Staged cMIS ASD correction may be more appropriate in patients with greater deformity, higher frailty, and who require longer, more extensive surgeries.

The Effect of Osteoporosis on Complications and Reoperation Rates After Surgical Management of Adult Thoracolumbar Spinal Deformity: A Systematic Review and Meta Analysis.

Systematic Review. While substantial research has explored the impact of osteoporosis on patients undergoing adult spinal deformity (ASD) correction, the literature remains inconclusive. As such, the purpose of this study is to synthesize and analyze existing studies pertaining to osteoporosis as a predictor of postoperative outcomes in ASD surgery. We performed a systematic review and meta-analysis to determine the effect that a diagnosis of osteoporosis, based on ICD-10 coding, dual-energy X-ray absorptiometry (DEXA) or computed tomography, has on the incidence of adverse outcomes following surgical correction of ASD. Statistical analysis was performed using Comprehensive Meta-Analysis (Version 2) using a random effects model to account for heterogeneity between studies. After application of inclusion and exclusion criteria, 36 and 28 articles were included in the systematic review and meta-analysis, respectively. The meta-analysis identified greater rates of screw loosening amongst osteoporotic patients (70.5% vs 31.9%, P = .009), and decreased bone mineral density in patients who developed proximal junctional kyphosis (PJK) (.69 vs .79g/cm2, P = .001). The systematic review demonstrated significantly increased risk of any complication, reoperation, and proximal junctional failure (PJF) associated with reduced bone density. No statistical difference was observed between groups regarding fusion rates, readmission rates, and patient-reported and/or functional outcome scores. This study demonstrates a higher incidence of screw loosening, PJK, and revision surgery amongst osteoporotic ASD patients. Future investigations should explore outcomes at various follow-up intervals in order to better characterize how risk changes with time and to tailor preoperative planning based on patient-specific characteristics.

287 What is the Velocity of Return-to-work After Circumferential Minimally-Invasive Surgery Versus Open Correction for Adult Spinal Deformity?

INTRODUCTION: While faster recovery is a touted benefit of minimally-invasive spinal operations, these differences have been poorly described for return-to-work after larger fusion constructs for adult spinal deformity. METHODS: Adult spinal deformity (ASD) patients =18 yr were queried from a multicenter, prospective database across the USA. To ensure equal cohorts for comparing the impact of MIS vs. open correction technique, propensity score matched gender, age, BMI, pelvic incidence-lumbar lordosis mismatch, and sagittal vertical axis. Of 190 patients with baseline surveys, 173 respondents (91.0%) had both baseline employment and 2-year follow-up. The open and cMIS cohorts were compared with a chi-squared test. The rate of return-to-work was calculated via discrete-time proportional hazards model—reporting an adjusted odds ratio (ORadj)—at three follow-up intervals: 6 weeks, 1-year, and 2-years. RESULTS: Of 173 patients, baseline employment status was nearly equal between open (n = 85) vs cMIS (n = 88) cohorts: employed (20.0% vs 21.5%), unemployed (3.5% vs 4.5%), disabled (4.7% vs 6.8%), and retired (71.7% vs 67.0%) (p = 0.888). The number of employed patients between the open vs cMIS cohort statistically significantly differed at 1-year (10.5% vs 21.5%, p = 0.049), but not at 6 weeks (14.1% vs 15.9%, p = 0.741) or 2-years (14.1% vs 19.3%, p = 0.277). The velocity of return-to-work did not differ (OR = 1.2, p = 0.549). In a sub-analysis of 36 patients who were employed at baseline, the number of employed patients between the open vs cMIS cohort statistically significantly differed at 1-year (47.0% vs 89.4%, p = 0.006), but not at 6 weeks (70.5% vs 73.6%, p = 0.636) or 2-years (58.8% vs 78.9%, p = 0.191). The velocity of return-to-work was also similar (ORadj = 1.57, p = 0.481). CONCLUSIONS: Despite an equivalent baseline employment status, more patients in the cMIS cohort were employed at 1-year; however, there was no difference at 2-years. Similar trends were appreciated in a sub-analysis of patients who were employed at baseline.

1073 Prone Transpsoas (PTP)-LLIF Approach Versus Standard LLIF in Patients Undergoing Surgical Revision Following Adult Spinal Deformity Correction Surgery

INTRODUCTION: Both the prone transpsoas (PTP) and standard LLIF have been developed to facilitate minimally invasive (MIS) indirect decompression, alignment correction, and posterior instrumentation. METHODS: A multi-center cohort of all patients was identified and all relevant data were retrospectively collected. Preoperative standing 36” scoliosis radiographs were retrospectively reviewed for pelvic incidence (PI), lumbar lordosis (LL), and PI minus LL (PI-LL mismatch). Postoperative regional sagittal alignment parameters were measured using the first postoperative standing 36” scoliosis radiographs. Finally, multivariable analysis was performed to assess the primary outcome measure: postoperative change in regional sagittal alignment (PI-LL mismatch). RESULTS: Two-hundred and two (n = 202) patients were retrospectively identified and included for formal analysis. One-hundred and fifty one (n = 151, 74.8%) of the patients underwent PTP revision while 51 (25.2%) underwent standard LLIF revision. Univariate analysis demonstrated a greater value for baseline mean pre-operative PI-LL mismatch in the PTP versus standard LLIF cohort (21.4 vs. 10.45°; p = 0.0001). Furthermore, multiple linear regression demonstrated that the PTP approach enabled significantly greater PI-LL mismatch change (p = 0.0017) and that this change was associated with the number of levels fused (p = 0.0481) as well as percutaneous (vs. open) screw placement (p = 0.0193). Finally, multiple logistic regression identified standard LLIF (p = 0.0378), female sex (p &lt; 0.0001), non-osteoporotic bone density (p &lt; 0.0001), and younger age (p &lt; 0.0001) as predictive of postoperative PI-LL mismatch &lt; 10° (the threshold under which such mismatch is no longer regarded as clinically significant deformity). CONCLUSIONS: Ultimately, PTP-LLIF was associated with greater net improvement in postoperative PI-LL mismatch, the primary outcome measure of this study. The present retrospective analysis therefore corroborated results of previous studies in suggesting that the utility of PTP-LLIF is translatable to ASD revision surgery.

Causes of Intraoperative Neuromonitoring Events in Adult Spine Deformity Surgery: A Systematic Review.

Systematic review. Intraoperative neuromonitoring (IOMN) has become a standard practice in the detection and prevention of nerve damage and postoperative deficit. While multicenter studies have addressed this inquiry, there have been no systematic reviews to date. This systematic review identifies the leading causes of IONM alerts during adult spinal deformity (ASD) surgeries. Following PRISMA guidelines, a literature search was performed in PubMed and Embase. IONM alert causes were grouped by equivalent terms used across different studies and binned into larger categories, including surgical maneuver, Changes in blood pressure/temperature, Oxygenation, Anesthesia, Patient position, and Unknown. Inclusion criteria were studies on adult patients receiving ASD correction surgery using IONM with documented alert causes. 1544 references were included in abstract review, 128 in full text review, and 16 studies qualified for data extraction. From those studies, there was a total of 3945 adult patients with 299 IONM alerts. Surgical maneuver led the alert causes (258 alerts/86.3%), with signal loss most commonly occurring at correction or osteotomy (101/33.8% and 95/31.8% respectively). Pedicle screw placement caused 35 alerts (11.7%). Changes in temperature and blood pressure were the third largest category (34/11.4%). The most frequent causes of IONM alerts in ASD surgery were surgical maneuvers such as correction, osteotomy, and pedicle screw placement. This information provides spine surgeons with a quantitative perspective on the causes of IONM changes and show that most occur at predictable times during ASD surgery.

A guide to selecting upper thoracic versus lower thoracic uppermost instrumented vertebra in adult spinal deformity correction.

Operative treatment of adult spinal deformity (ASD) has been shown to improve patient health-related quality of life (HRQOL). Selection of the uppermost instrumented vertebra (UIV) in either the upper thoracic (UT) or lower thoracic (LT) spine is a pivotal decision with effects on operative and postoperative outcomes. This review overviews the multifaceted decision-making process for UIV selection in ASD correction. PubMed was queried for articles using the keywords "uppermost instrumented vertebra", "upper thoracic", "lower thoracic", and "adult spinal deformity". Optimization of UIV selection may lead to superior deformity correction, better patient-reported outcomes, and lower risk of proximal junctional kyphosis (PJK) and failure (PJF). Patient alignment characteristics, including preoperative thoracic kyphosis, coronal deformity, and the magnitude of sagittal correction influence surgical decision-making when selecting a UIV, while comorbidities such as poorbody mass index, osteoporosis, and neuromuscular pathology should also be taken in to account. Additionally, surgeon experience and resources available to the hospital may also play a role in this decision. Currently, it is incompletely understood whether postoperative HRQOLs, functional and radiographic outcomes, and complications after surgery differ between selection of the UIV in either the UT or LT spine. The correct selection of the UIV in surgical planning is a challenging task, which requires attention to preoperative alignment, patient comorbidities, clinical characteristics, available resources, andsurgeon-specific factors such as experience.

Preoperative Robotics Planning Facilitates Complex Construct Design in Robot-Assisted Minimally Invasive Adult Spinal Deformity Surgery-A Preliminary Experience.

(1) Background: The correction of adult spinal deformity (ASD) can require long, complex constructs with multiple rods which traverse important biomechanical levels to achieve multi-pelvic fixation. Minimally invasive (MIS) placement of these constructs has historically been difficult. Advanced technologies such as spinal robotics platforms can facilitate the design and placement of these constructs and further enable these surgical approaches in MIS deformity surgery. (2) Methods: A retrospective study was performed on a series of ASD patients undergoing MIS deformity correction with ≥eight fusion levels to the lower thoracic spine with preoperative robotic construct planning and robot-assisted pedicle screw placement. (3) Results: There were 12 patients (10 female, mean age 68.6 years) with a diagnosis of either degenerative scoliosis (8 patients) or sagittal imbalance (4 patients). All underwent preoperative robotic planning to assist in MIS robot-assisted percutaneous or transfascial placement of pedicle and iliac screws with multiple-rod constructs. Mean operative values per patient were 9.9 levels instrumented (range 8-11), 3.9 interbody cages (range 2-6), 3.3 iliac fixation points (range 2-4), 3.3 rods (range 2-4), 18.7 screws (range 13-24), estimated blood loss 254 cc (range 150-350 cc), and operative time 347 min (range 242-442 min). All patients showed improvement in radiographic sagittal, and, if applicable, coronal parameters. Mean length of stay was 5.8 days with no ICU admissions. Ten patients ambulated on POD 1 or 2. Of 224 screws placed minimally invasively, four breaches were identified on intraoperative CT and repositioned (three lateral, one medial) for a robot-assisted screw accuracy of 98.2%. (4) Conclusions: Minimally invasive long-segment fixation for adult spinal deformity surgery has historically been considered laborious and technically intensive. Preoperative robotics planning facilitates the design and placement of even complex multi-rod multi-pelvic fixation for MIS deformity surgery.

Transpedicular injection of rhBMP-2 with β-tricalcium phosphate to reduce the proximal junctional kyphosis after adult spinal deformity correction: preliminary study

The aim of this preliminary study was to assess the impact of injecting recombinant human bone morphogenetic protein-2 (rhBMP-2) with β-tricalcium phosphate (β-TCP) carrier into the uppermost instrumented vertebra (UIV) during surgery to prevent the development of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). The 25 patients from study group had received 0.5 mg rhBMP-2 mixed with 1.5 g β-TCP paste injection into the UIV during surgery. The control group consisted of 75 patients who underwent surgery immediately before the start of the study. The incidences of PJK and PJF were analyzed as primary outcomes. Spinopelvic parameters and patient-reported outcomes were analyzed as secondary outcomes. Hounsfield unit (HU) measurements were performed to confirm the effect of rhBMP-2 with β-TCP on bone formation at preoperative and postoperative at computed tomography. PJK and PJF was more occurred in control group than study group (p = 0.02, 0.29, respectively). The HU of the UIV significantly increased 6 months after surgery. And the increment at the UIV was also significantly greater than that at the UIV-1 6 months after surgery. Injection of rhBMP-2 with β-TCP into the UIV reduced PJK and PJF rates 6 months after surgery with new bone formation.

Knee flexion compensation in postoperative adult spinal deformity patients: implications for sagittal balance and clinical outcomes.

To determine whether maintaining good sagittal balance with significant knee flexion (KF) constitutes a suboptimal outcome after adult spinal deformity (ASD) correction. This single-center, single-surgeon retrospective study, assessed ASD patients who underwent posterior spinal fusion between 2014 and 2020. Inclusion criteria included meeting at least one of the following: PI-LL ≥ 25°, T1PA ≥ 20°, or CrSVA-H ≥ 2cm. Those with lower-extremity contractures were excluded. Patients were classified into four groups based on their 6-week postoperative cranio-hip balance and KF angle, and followed for at least 2 years: Malaligned with Knee Flexion (MKF+) (CrSVA-H > 20mm + KFA > 10), Malaligned without Knee Flexion (MKF-) (CrSVA-H > 20mm + KFA < 10), Aligned without Knee Flexion (AKF-) (CrSVA-H < 20mm + KFA < 10), and Aligned with Knee Flexion (AKF+) (CrSVA-H < 20mm + KFA > 10). The primary outcomes of this study included one and two year reoperation rates. Secondy outcomes included clinical and patient reported outcomes. 263 patients (mean age 60.0 ± 0.9 years, 74.5% female, and mean Edmonton Frailty Score 3.3 ± 0.2) were included. 60.8% (160/263 patients) exhibited good sagittal alignment at 6-week postop without KF. Significant differences were observed in 1-year (p = 0.0482) and 2-year reoperation rates (p = 0.0374) across sub-cohorts, with the lowest and highest rates in the AKF- cohort (5%, n = 8) and MKF + cohort (16.7%, n = 4), respectively. Multivariable Cox regression demonstrated the AKF- cohort exhibited significantly better reoperation outcomes compared to other groups: AKF + (HR: 5.24, p = 0.025), MKF + (HR: 31.7, p < 0.0001), and MKF- (HR: 11.8, p < 0.0001). Our findings demonstrate that patients relying on knee flexion compensation in the early postoperative period have inferior outcomes compared to those achieving sagittal balance without knee flexion. When compared to malaligned patients, those with CrSVA-H < 20mm and KFA > 10 degrees experience fewer early reoperations but similar delayed reoperation rates. This insight emphasizes the importance of considering knee compensation perioperatively when managing sagittal imbalance in clinical practice.