Long Term Mechanical Failure In Well Aligned Adult Spinal Deformity Patients.

BACKGROUND CONTEXT: Mechanical complications (MC) are frequently linked to suboptimal postoperative alignment and represent a primary driver of revision surgery in the context of Adult Spinal Deformity (ASD). However, it's worth noting that even among those deemed "well aligned," the risk of experiencing MCs persists, hinting at the potential influence of factors beyond alignment. PURPOSE: The aim was to assess the incidence of MCs among well-aligned patients and delving into the relevant risk factors and surgical outcomes that come into play within this specific subgroup. STUDY DESIGN/SETTING: A retrospective analysis was conducted using data from a prospective multicenter database dedicated to ASD. PATIENT SAMPLE: The study focused on patients aged 55 years or older, who had a minimum follow-up period of two years, and exhibited a Global Alignment and Proportion (GAP) score of two points or less (excluding age) within six weeks of their index surgery. OUTCOME MEASURES: Mechanical complications such as rod fractures, pseudarthrosis, or junctional kyphosis or failure, METHODS: Patients who developed mechanical complications were identified. Comparative analyses were performed, encompassing both continuous and categorical variables. Furthermore, binary logistic regression tests were employed to pinpoint risk factors, and ROC curves were used to determine the optimal threshold values for these variables. RESULTS: A total of 83 patients met the inclusion criteria for this study, with a mean age of 66 years. On average, they had 10 instrumented levels, and 77% of them had fusion extending to the pelvis. Additionally, 27% of the patients had undergone three-column osteotomies (3-CO). Among them, 33 patients (40%) experienced at least one MC during an average follow-up period of 4 years, which included 14 cases of proximal junctional kyphosis (PJK) and 20 cases of nonunion or rod breakage. 15 patients (18%) required revision surgery specifically for MC. In univariable analyses, patients who developed MC were characterized by higher body weight, poorer baseline general health (as indicated by worse SF-36 scores), and less favorable preoperative coronal and sagittal alignment. They also had longer hospital stays, a greater number of instrumented levels, and achieved less favorable postoperative coronal and sagittal alignment. Interestingly, factors such as three-column osteotomies, postoperative bracing, and the addition of an anterior approach did not significantly alter the risk of MC in well-aligned adult spinal deformity (ASD) patients. Binary regression models revealed that independent risk factors for MC included the residual coronal lumbosacral curve, the number of instrumented levels, and Relative Spinopelvic Alignment (RSA). ROC curves identified an optimal threshold of a residual lumbosacral curve of ≤4° and RSA of ≤3°. Moreover, the rate of MCs showed a stepwise increase within the GAP-Proportioned group, with rates of 31% for GAP=0, 54% for GAP=1, and 75% for GAP=2, with RSA emerging as the most influential parameter. Lastly, patients with MC exhibited poorer functional and radiological outcomes at their last follow-up assessment. CONCLUSIONS: The rate of MCs remains elevated in sagittally "well-aligned" ASD patients that can be attributed to suboptimal residual sagittal and coronal malalignment, which in turn leads to poorer functional outcomes. This study reaffirms the multifaceted nature of MCs and underscores the significance of achieving impeccable postoperative alignment, particularly in the presence of additional risk factors such as extensive surgical correction, a high lever arm (involving instrumented vertebrae), excessive body weight, and frailty (as indicated by SF-36 scores).

Long-Term Loss of Alignment Following ASD Surgery in the Absence of Mechanical Complications: Aging Spine?

STUDY DESIGN: Retrospective analysis of a prospective multicenter Adult Spinal Deformity (ASD) registry. OBJECTIVE: Assess whether spinal alignment deteriorates post-surgery in absence of mechanical complications and evaluate the long-term outcomes of ASD surgery over a five-year period. SUMMARY OF BACKGROUND DATA: ASD is prevalent among older adults, leading to significant pain and disability. Surgical intervention, although increasingly popular, is associated with complications, high costs, and uncertain long-term outcomes beyond two years. Mechanical failure and alignment loss often necessitate revision surgeries, but the natural progression of spinal alignment post-surgery without complications remains unclear. METHODS: Clinical and radiological data were analyzed from surgical patients in a multicenter ASD registry who maintained alignment within the instrumented region and completed a 5-year follow-up. The study evaluated patient demographics, surgical details, radiological parameters, and quality of life (QoL) outcomes. Sub-analyses were conducted to compare patients with different initial postoperative alignments and fixation levels. RESULTS: The study included 79 patients (83.5% women, average age 61.9 years) with a mean of 10.7 fused levels. Of these, 29.1% underwent three-column osteotomies (3CO), and 88.6% had a posterior-only approach. While 65% showed favorable alignment at 6 weeks post-surgery, there was a progressive deterioration in global sagittal alignment (Global Tilt/RSA) and thoracic kyphosis over five years (P<0.05), along with increased pelvic compensation (PT SS/RPV). These changes did not correlate with worsening Health-Related Quality of Life outcomes (P>0.05). Older age was linked to greater progression in T2-T12 kyphosis, and osteoporosis was associated with increased SVA and RPV. Optimal immediate postoperative sagittal alignment did not prevent this "aging effect." CONCLUSIONS: ASD surgery and achieving ideal postoperative alignment do not prevent the ongoing "aging" of the non-instrumented spine. Both thoracic and global sagittal alignments deteriorate over time. Although no functional decline has been observed, the implications of these changes for surgical planning remain uncertain.

Associations of overweight status with spinal curve correction and complications in patients undergoing vertebral body tethering: a multicenter retrospective review.

PURPOSE: Our purpose was to determine associations between body mass index (BMI) category and outcomes of vertebral body tethering (VBT), a non-fusion treatment for adolescent idiopathic scoliosis (AIS) and juvenile idiopathic scoliosis (JIS). METHODS: Using a multicenter database, we identified patients with AIS or JIS who underwent VBT from 2012 to 2018 and had minimum 2-year follow-up (median, 3.0 [interquartile range 2.2, 3.8]). BMI percentiles were used to classify patients as overweight (≥ 85th percentile) or non-overweight (< 85th percentile). Univariate and multivariate regressions assessed associations between complication rates and curve correction between groups, controlling for sex, triradiate cartilage closure, and preoperative curve magnitude. RESULTS: Of 271 patients, 48 (18%) were overweight. Complication rates did not differ between groups. Factors associated with less correction from preoperative to first postoperative-erect imaging were overweight (ß = - 10, p < 0.001), male sex (ß = - 8.8 p < 0.01), closed triradiate cartilage (ß = 6.0, p = 0.01), and smaller preoperative curve (ß = 0.3, p < 0.01). Factors associated with a larger curve at latest follow-up were overweight (ß = 4.0, p = 0.02) and larger preoperative curve (ß = 0.5, p < 0.001), but tether breakage did not differ between groups (p = 0.31). CONCLUSION: In patients who were overweight, VBT was associated with less curve correction at first erect imaging and larger final curve. However, complications and curve correction during the modulation phase were not different from those of non-overweight patients. These findings suggest that surgeons should expect less correction with VBT in patients who are overweight but similar correction over time. LEVEL OF EVIDENCE: Prognostic, Level III.

Opioid Use Prior to Adult Spine Deformity Correction Surgery is Associated With Worse Pre- and Postoperative Back Pain and Prolonged Opioid Demands.

STUDY DESIGN: Prospective multicenter database post-hoc analysis. OBJECTIVES: Opioids are frequently prescribed for painful spinal conditions to provide pain relief and to allow for functional improvement, both before and after spine surgery. Amidst a current opioid epidemic, it is important for providers to understand the impact of opioid use and its relationship with patient-reported outcomes. The purpose of this study was to evaluate pre-/postoperative opioid consumption surrounding ASD and assess patient-reported pain outcomes in older patients undergoing surgery for spinal deformity. METHODS: Patients ≥60 years of age from 12 international centers undergoing spinal fusion of at least 5 levels and a minimum 2-year follow-up were included. Patient-reported outcome scores were collected using the Numeric Rating Scale for back and leg pain (NRS-B; NRS-L) at baseline and at 2 years following surgery. Opioid use, defined based on a specific question on case report forms and question 11 from the SRS-22r questionnaire, was assessed at baseline and at 2-year follow-up. RESULT: Of the 219 patients who met inclusion criteria, 179 (81.7%) had 2-year data on opioid use. The percentages of patients reporting opioid use at baseline (n = 75, 34.2%) and 2 years after surgery (n = 55, 30.7%) were similar (P = .23). However, at last follow-up 39% of baseline opioid users (Opi) were no longer taking opioids, while 14% of initial non-users (No-Opi) reported opioid use. Regional pre- and postoperative opioid use was 5.8% and 7.7% in the Asian population, 58.3% and 53.1% in the European, and 50.5% and 40.2% in North American patients, respectively. Baseline opioid users reported more preoperative back pain than the No-Opi group (7.0 vs 5.7, P = .001), while NRS-Leg pain scores were comparable (4.8 vs 4, P = .159). Similarly, at last follow-up, patients in the Opi group had greater NRS-B scores than Non-Opi patients (3.2 vs 2.3, P = .012), but no differences in NRS-Leg pain scores (2.2 vs 2.4, P = .632) were observed. CONCLUSIONS: In this study, almost one-third of surgical ASD patients were consuming opioids both pre- and postoperatively world-wide. There were marked international variations, with patients from Asia having a much lower usage rate, suggesting a cultural influence. Despite both opioid users and nonusers benefitting from surgery, preoperative opioid use was strongly associated with significantly more back pain at baseline that persisted at 2-year follow up, as well as persistent postoperative opioid needs.

Proximal junctional kyphosis after adult spinal deformity operated patients with long fusion to the pelvis. Does the type of proximal anchor matter?

PURPOSE: To assess, in a large population of Adult Spinal Deformity (ASD) patients, the true interest of varying the upper anchors as a protective measure against Proximal Junctional Kyphosis (PJK), by analyzing and comparing 2 groups of patients defined according to their proximal construct. Another objective of the study is to look for any other factors, radiological or clinical, that would affect the occurrence of the proximal failure. METHODS: Retrospective review of a prospective ASD database collected from 5 centers. Inclusion criteria were age of at least 18 years, presence of a spinal deformity with instrumentation from T12 or above to the pelvis, with minimum 2 years of follow-up. Demographic data, spinopelvic parameters, functional outcomes and complications were collected. Multiple logistic regression analysis was performed to identify the risk factors that would affect the occurrence of PJK. RESULTS: 254 patients were included. 166 in the group "screws proximally" (SP) and 88 in the group "hooks proximally" (HP). There was no difference between both groups for PJK (p = 0.967). The occurrence of PJK was rather associated with greater age and BMI, higher preoperative kyphosis, worst preoperative SRS22 and SF36 scores, greater postoperative Sagittal Vertical Axis (SVA), coronal malalignment and kyphosis. CONCLUSION: The use of proximal hooks was not effective to prevent PJK after ASD surgery, when compared to proximal screws. Worse preoperative functional outcomes and worse postoperative sagittal and also coronal malalignment were the main drivers for the occurrence of PJK regardless the type of proximal implant.

Calculation of the minimal clinically important difference in operated patients with adult spine deformity: advantages of the ROC method and significance of prevalence in threshold selection.

PURPOSE: The Minimal Clinically Important Difference (MCID) is crucial to evaluate management outcomes, but different thresholds have been obtained in different works. Part of this variability is due to measurement error and influence of the database, both essential for calculating the MCID. The aim of this study was to introduce the association of the ROC method in the anchor-based MCID calculation for ODI, SRS-22r, and SF-36, to objectively set the threshold for the anchor-based MCID in an adult spine deformity (ASD) population. METHODS: Multicentric study based on a prospective database of consecutively operated ASD patients. An anchor question was used to assess patients' quality of life after surgery. Different approaches were used to calculate the MCID and then compared: SEM (Standard Error of Measurement), MDC (Minimal Detectable Change), and anchor-based MCID with ROC method. RESULTS: 516 patients were included. Those who responded with 6 and 7 to the anchor question were considered improved. The MCID ranges obtained with the ROC method exhibited the lowest variability. Prediction error rates ranged from 31% (SRS-22r) to 41% (SF-36 MCS). The MCID ranges spanned between 12 and 15 for ODI, 0.6 and 0.73 for SRS-22r, 6.62 and 7.41 for SF-36 PCS, and between 2.69 and 5.63 for SF-36 MCS. CONCLUSION: The ROC method proposes an MCID range with error rate, and can objectively determine the threshold for distinguishing improved and non-improved patients. As the MCID correlates with the utilized database and error of measurement, each study should compute its own MCID for each PROM to allow comparison among different publications. LEVEL OF EVIDENCE: II.

The Impact of Unplanned Reoperation Following Adult Spinal Deformity Surgery: A Prospective Longitudinal Cohort Study with 5-Year Follow-up.

BACKGROUND: The long-term impact of reoperations following adult spinal deformity (ASD) surgery is still poorly understood. Our aim was to identify the relationship between unplanned reoperation and health-related quality of life (HRQoL) gain at 2 and 5 years of follow-up. METHODS: We included patients enrolled in a prospective ASD database who underwent surgery ≥5 years prior to the start of the study and who had 2 years of follow-up data. Adverse events (AEs) leading to an unplanned reoperation, the time of reoperation occurrence, invasiveness (blood loss, surgical time, hospital stay), and AE resolution were assessed. HRQoL was measured with use of the Oswestry Disability Index, Scoliosis Research Society-22, and Short Form-36. Linear models controlling for baseline data and index surgery characteristics were utilized to assess the relationships between HRQoL gain at 2 and 5-year follow-up and the number and invasiveness of reoperations. The association between 5-year HRQoL gain and the time of occurrence of the unplanned reoperation and that between 5-year HRQoL gain and AE resolution were also investigated. RESULTS: Of 361 eligible patients, 316 (87.5%) with 2-year follow-up data met the inclusion criteria and 258 (71.5%) had 5-year follow-up data. At the 2-year follow-up, 96 patients (30.4%) had a total of 165 unplanned reoperations (1.72 per patient). At the 5-year follow-up, 73 patients (28.3%) had a total of 117 unplanned reoperations (1.60 per patient). The most common cause of reoperations was mechanical complications (64.9%), followed by surgical site infections (15.7%). At the 5-year follow-up, the AE that led to reoperation was resolved in 67 patients (91.8%). Reoperation invasiveness was not associated with 5-year HRQoL scores. The number of reoperations was associated with lesser HRQoL gain at 5 years for all HRQoL measures. The mean associated reduction in HRQoL gain per unplanned reoperation was 41% (range, 19% to 66%). Reoperations resulting in no resolution of the AE or resolution with sequelae had a greater impact on 5-year follow-up HRQoL scores than reoperations resulting in resolution of the AE. CONCLUSIONS: A postoperative, unplanned reoperation following ASD surgery was associated with lesser gain in HRQoL at 5 years of follow-up. The association did not diminish over time and was affected by the number, but not the magnitude, of reoperations. Resolution of the associated AE reduced the impact of the unplanned reoperation. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Which sagittal plane assessment method is most predictive of complications after adult spinal deformity surgery?

PURPOSE: Different methods of sagittal alignment assessment compete for predicting adverse events after adult spinal deformity (ASD) surgery. We wanted to study which method provides greater benefit. METHODS: Retrospective study of 391 patients operated for ASD, with > 6 instrumented levels, fused to the pelvis, and 2 years of follow-up. Three alignment methods were analyzed 6-week postoperatively: (1) Roussouly mismatch; (2) GAP score/GAP categories; (3) T4-L1-Hip axis. Binary logistic regression generated models that best predict the following adverse events: mechanical complications (MC): in general and isolated (PJK, PJF, rod breakage); reinterventions (in general and after MC); and readmissions. ROC/AUC analysis was also implemented. In a second regression round, we added different variables that were selected on univariate analysis-demographic, surgical, and radiographic-to complete the models. RESULTS: The best predictor parameters in most models were T4-L1PA mismatch and GAP score; we could not prove a predictive ability of the Roussouly mismatch. The T4-L1PA mismatch best predicted general MC, PJK, PJK + PJF, and readmission, while the GAP score best predicted PJF and reinterventions (for MC and for any complication). However, the variance explained by these models was limited (Nagelkerke's R2 = 0.031-0.113), with odds ratios ranging from 1.070 to 1.456. ROC curves plotted an AUC between 0.57 and 0.70. Introducing additional variables (demographic, surgical, and radiographic) improved prediction in all the models (Nagelkerke's R2 = 0.082-0.329) and allowed predicting rod breakage. CONCLUSION: The T4-L1-Hip axis and GAP score show potential in predicting adverse events, surpassing the Roussouly method. Despite partial efficacy in complication anticipation, recognizing postoperative sagittal alignment as a key modifiable risk factor, the crucial need arises to integrate diverse variables, both modifiable and non-modifiable, for enhanced predictive accuracy. LEVEL OF EVIDENCE: Level IV.

What factors are associated with a better restoration of pelvic version after adult spinal deformity surgery?

INTRODUCTION: Poor restoration of pelvic version after adult spinal deformity (ASD) surgery is associated with an increased risk of mechanical complications and worse quality of life. We studied the factors linked to the improvement of postoperative pelvic version. MATERIALS AND METHODS: This is a retrospective analysis of a prospective multicenter ASD database. Selection criteria were: operated patients having preoperative severe pelvic retroversion as per GAP score (Relative Pelvic Version-RPV < - 15°); panlumbar fusions to the pelvis; 2-year follow-up. Group A comprised patients with any postoperative improvement of RPV score, and group B had no improvement. Groups were compared regarding baseline characteristics, surgical factors, and postoperative sagittal parameters. Parametric and non-parametric analyses were employed. RESULTS: 177 patients were studied, median age 67 years (61; 72.5), 83.6% female. Groups were homogeneous in baseline demographics, comorbidities, and preoperative sagittal parameters (p > 0.05). The difference in RPV improvement was 11.56º. Group A (137 patients) underwent a higher percentage of ALIF procedures (OR = 6.66; p = 0.049), and posterior osteotomies (OR = 4.96; p < 0.001) especially tricolumnar (OR = 2.31; p = 0.041). It also showed a lower percentage of TLIF procedures (OR = 0.45; p = 0.028), and posterior decompression (OR = 0.44; p = 0.024). Group A displayed better postoperative L4-S1 angle and relative lumbar lordosis (RLL), leading to improved sacral slope (and RPV), and global alignment (RSA). Group A patients had longer instrumentations (11.45 vs 10; p = 0.047) and hospitalization time (13 vs 11; p = 0.045). All postoperative sagittal parameters remained significantly better in group A through follow-up. However, differences between the groups narrowed over time. CONCLUSIONS: ALIF procedures and posterior column osteotomies improved pelvic version postoperatively, and associated better L4-S1 and lumbar lordosis restoration, indirectly improving all other sagittal parameters. However, these improvements seemed to fade during the 2-year follow-up.

Reliability of a New Digital Tool for Photographic Analysis in Quantifying Body Asymmetry in Scoliosis.

Background: Advancements in non-ionizing methods for quantifying spinal deformities are crucial for assessing and monitoring scoliosis. In this study, we analyzed the observer variability of a newly developed digital tool for quantifying body asymmetry from clinical photographs. Methods: Prospective observational multicenter study. Initially, a digital tool was developed using image analysis software, calculating quantitative measures of body asymmetry. This tool was integrated into an online platform that exports data to a database. The tool calculated 10 parameters, including angles (shoulder height, axilla height, waist height, right and left waistline angles, and their difference) and surfaces of the left and right hemitrunks (shoulders, waists, pelvises, and total). Subsequently, an online training course on the tool was conducted for twelve observers not involved in its development (six research coordinators and six spine surgeons). Finally, 15 standardized back photographs of adolescent idiopathic scoliosis patients were selected from a multicenter image bank, representing various clinical scenarios (different age, gender, curve type, BMI, and pre- and postoperative images). The 12 observers measured the photographs at two different times with a three-week interval. For the second round, the images were randomly mixed. Inter- and intra-observer variabilities of the measurements were analyzed using intraclass correlation coefficients (ICCs), and reliability was measured by the standard error of measurement (SEM). Group comparisons were made using Student's t-test. Results: The mean inter-observer ICC for the ten measurements was 0.981, the mean intra-observer ICC was 0.937, and SEM was 0.3-1.3°. The parameter with the strongest inter- and intra-observer validity was the difference in waistline angles 0.994 and 0.974, respectively, while the highest variability was found with the waist height angle 0.963 and 0.845, respectively. No test-retest differences (p > 0.05) were observed between researchers (0.948 ± 0.04) and surgeons (0.925 ± 0.05). Conclusion: We developed a new digital tool integrated into an online platform demonstrating excellent reliability and inter- and intra-observer variabilities for quantifying body asymmetry in scoliosis patients from a simple clinical photograph. The method could be used for assessing and monitoring scoliosis and body asymmetry without radiation.

Anterior vertebral body tethering shows clinically comparable shoulder balance outcomes to posterior spinal fusion.

PURPOSE: Posterior spinal fusion (PSF) is the current gold standard in surgical treatment for adolescent idiopathic scoliosis. Vertebral body tethering (VBT) is a fusionless alternative. Shoulder balance is an important metric for outcomes and patient satisfaction. Here we compare shoulder balance outcomes between PSF and VBT. METHODS: In this retrospective review, the pre-operative and post-operative absolute radiographic shoulder height (|RSH|) of 45 PSF patients were compared to 46 VBT patients. Mean values were compared and then collapsed into discrete groups (|RSH| GROUP) and compared. Patients were propensity score matched. Regression models based on pretest-posttest designs were used to compare procedure type on post-operative outcomes. RESULTS: Pre-operatively there were no differences in |RSH| between PSF and VBT, however, at latest post-operative follow-up PSF maintained a larger |RSH| imbalance compared to VBT (0.91 cm vs 0.63 cm, p = 0.021). In an ANCOVA regression, PSF was associated with a larger |RSH| imbalance compared to VBT, F(1, 88) = 5.76, p = 0.019. An ordinal logistic regression found that the odds ratio of being in a worse |RSH| GROUP for PSF vs VBT is 2.788 (95% CI = 1.099 to 7.075), a statistically significant effect χ2(1) = 4.658, p = 0.031. Results were similar in subgroup analyses of Lenke 1 and Lenke 2 patients, though to less statistical significance. CONCLUSION: While PSF was found to be associated with worse |RSH| outcomes, the actual numbers (2-3 mm) are unlikely to be clinically meaningful. Thus, in this analysis, VBT can be said to show comparable shoulder balance outcomes to PSF.

Influence of smoking on patient-reported outcome measures (PROMs) in patients undergoing surgery for adult spinal deformity: a propensity score-matched analysis.

PURPOSE: The purpose of this study was to determine the isolated influence of smoking in patient-reported outcome measures (PROMs) for adult spinal deformity (ASD) surgery excluding known tobacco-related complications. METHODS: Retrospective analysis of a prospective multicenter ASD database. Patients operated on ASD with 2 year post-operative follow-up were included. Former smokers (non-active smokers) and patients developing mechanical or infectious complications were excluded. Changes of PROMs over time were analyzed using mixed models for repeated measures (MMRM). Propensity score matching (PSM) (1:1 ratio, caliper 0.10) was performed without replacement using optimum algorithm, tolerance ≤ 0.001, and estimated with 95% confidence interval (CI). PROMS in both groups were compared by paired t test or Wilcoxon signed-rank test. RESULTS: 692 out of 1246 surgical patients met our inclusion criteria. 153 smokers were matched with 153 non-smokers according to age, BMI, number of fused levels, and global tilt. After PSM both groups were homogeneous regarding baseline parameters, surgical data, and complications (mechanical complications and infection excluded). Smokers had worse baseline results for SRS-total, SRS-pain COMI-back, and ODI; smokers also showed worse 2-year outcomes for SRS-total, SRS-function, SRS-pain, SRS-self-image, and ODI. However, no differences between the two groups were found in the improvement from baseline to 2-year follow-up or in the timing of this improvement (MMRM). The proportion of patients reaching the minimal clinically important difference (MCID) after surgery was similar in the two groups, but the proportion of patients reaching patient acceptable symptom state (PASS) was significantly lower in smokers for SRS-Subtotal, SRS-function, and SRS-image. CONCLUSION: Even in the absence of smoking-related complications, smokers had worse PROMs at baseline and 2 years after surgery with less patients achieving PASS, but similar degrees on improvement compared to non-smokers. The proportion achieving MCID was also similar between the two cohorts.

Primary Pelvic Anteversion: Definition, Relevance, and History After Surgery for Adult Spine Deformity.

STUDY DESIGN: Retrospective analysis of prospectively collected data. OBJECTIVE: To identify the best definition of primary anteverted pelvis in the setting of adult spine deformity (ASD), and to investigate whether this is a pathologic setting that requires surgical correction. SUMMARY OF BACKGROUND DATA: While pelvic retroversion has been thoroughly investigated, pelvic anteversion (AP) is a far lesser discussed topic. Four different AP definitions have been proposed, and AP has been described as a normal or pathologic entity by different authors. MATERIALS AND METHODS: All patients consulting for ASD at the five participating sites were included. First, the four definitions of AP were compared with descriptive statistics (anatomic method-Pelvic Tilt <0°; Relative Pelvic Version method-RPV >5°; Roussouly method-Pelvic Incidence (PI)<50° and Sacral Slope (SS)>35°); low PT method-PT/PI <25th percentile). Second a subgroup analysis among operated AP patients with a two-year follow-up was performed. Complication rate, radiographic parameters, and clinical scores (ODI, SF-36) were compared in a multivariate analysis between patients who did and did not maintain an AP at the 2-year follow-up. RESULTS: A total of 1163 patients were available for the first analysis. The RPV method seemed to be the most appropriate to define AP in ASD patient. For the second analysis, data on 410 subjects were available, and most of them were young adults with idiopathic scoliosis that did not require pelvic fixation. AP patients who maintained an AP after ASD surgery presented comparable radiographic and clinical outcomes to the patients who presented a normoverted/retroverted pelvis after surgery. CONCLUSIONS: According to the results of the presented study, the RPV method is the most appropriate to define primary AP, which is not a pathologic condition and is most often observed in young adults with idiopathic scoliosis. Anteverted pelvis does not require direct surgical correction in this patient group.

Double major curvature treated with vertebral body tethering of both curves: how do outcomes compare to posterior spinal fusion?

PURPOSE: Vertebral body tethering (VBT) is a non-fusion alternative to posterior spinal fusion (PSF). There have been few reports on VBT of two curvatures. We aim to compare the radiographic outcomes between VBT and PSF in patients with double curvatures in which both curves were instrumented. METHODS: 29 AIS patients matched by Lenke, age (± 2 years), triradiate cartilage closure status, major Cobb angle (± 8°), and T5-T12 kyphosis (± 10°). Variables were compared using Wilcoxon rank-sum tests, Student's t tests, and chi-Square. Clinical success was defined as major curve < 35°. RESULTS: Group baseline demographics were similar. Major thoracic (T) curve types had significantly better major (VBT 51.5 ± 7.9° to 31.6 ± 12.0° [40%] vs. PSF 54.3 ± 7.4° to 17.4 ± 6.5° [68%]; p = 0.0002) and secondary curve correction in the PSF group. 71% of major T VBT patients were clinically successful versus 100% of PSF. Major thoracolumbar (TL) curve types experienced comparable major (VBT 52.3 ± 7.0° to 18.3 ± 11.4° (65%) vs. PSF 53.0 ± 5.2° to 23.8 ± 10.9° (56%); p = 0.2397) and secondary curve correction. 92% of major TL VBT patients were clinically successful versus 75% in the PSF group. There was no difference in T5-12 kyphosis or lumbar lordosis between groups for any curve type. There were 4 patients (13.8%) with major complications in the VBT group compared to 0 (0%) in the PSF. CONCLUSION: Patients with double major AIS who underwent VBT with major T curve types had less correction than PSF; however, those with major TL curves experienced similar radiographic outcomes regardless of procedure. Complications were greater for VBT.

Sagittal alignment of diverse mechanical complications following adult spinal deformity surgery.

PURPOSE: To compare the sagittal alignment of patients with diverse mechanical complications (MCs) following adult spinal deformity (ASD) surgery with that of patients without MCs. METHODS: A total of 371 patients who underwent ASD surgery were enrolled. The sagittal spinopelvic parameters were measured preoperatively and at the 6-month and last follow-up, and the global alignment and proportion (GAP) score was calculated. The subjects were divided into non-MC and MCs groups, and the MCs group was further divided into rod fracture (RF), screw breakage (SB), screw dislodgement (SD) and proximal junctional kyphosis (PJK) subgroups. RESULTS: Preoperatively, the RF group had greater thoracolumbar kyphosis (TLK) and relative upper lumbar lordosis (RULL); the SB group had the largest pelvic incidence (PI) and lumbar lordosis (LL); the SD group had the least global sagittal imbalance; and the PJK group had the highest thoracic kyphosis (TK), TLK and RULL. At the last follow-up, the RF and SB groups featured a large PI minus LL (PI-LL), while the PJK group featured a prominent TK; all the MCs subgroups had sagittal malalignment and a higher GAP score, and the SB group had the most severe cases. Logistic regressions showed that the relative spinopelvic alignment (RSA) score was correlated with RF, SB and SD, while the RSA and age scores were associated with PJK. CONCLUSION: Each patient with MCs had individual characteristics in the sagittal plane following ASD surgery, which may be helpful to understand the pathophysiology of poor sagittal alignment with its subsequent MCs and guide an eventual revision strategy.

Incidence of Tether Breakage in Anterior Vertebral Body Tethering.

BACKGROUND: Thoracic anterior vertebral body tethering (TAVBT) is an emerging treatment for adolescent idiopathic scoliosis. Tether breakage is a known complication of TAVBT with incompletely known incidence. We aim to define the incidence of tether breakage in patients with adolescent idiopathic scoliosis who undergo TAVBT. The incidence of tether breakage in TAVBT is hypothesized to be high and increase with time postoperatively. METHODS: All patients with right-sided, thoracic curves who underwent TAVBT with at least 2 and up to 3 years of radiographic follow-up were included. Tether breakage between 2 vertebrae was defined a priori as any increase in adjacent screw angle >5 degrees from the minimum over the follow-up period. The presence and timing of tether breakage were noted for each patient. A Kaplan-Meier survival analysis was performed to calculate expected tether breakage up to 36 months. χ 2 analysis was performed to examine the relationship between tether breakage and reoperations. Independent t test was used to compare the average final Cobb angle between cohorts. RESULTS: In total, 208 patients from 10 centers were included in our review. Radiographically identified tether breakage occurred in 75 patients (36%). The initial break occurred at or beyond 24 months in 66 patients (88%). Kaplan-Meier survival analysis estimated the cumulative rate of expected tether breakage to be 19% at 24 months, increasing to 50% at 36 months. Twenty-one patients (28%) with a radiographically identified tether breakage went on to require reoperation, with 9 patients (12%) requiring conversion to posterior spinal fusion. Patients with a radiographically identified tether breakage went on to require conversion to posterior spinal fusion more often than those patients without identified tether breakage (12% vs. 2%; P =0.004). The average major coronal curve angle at final follow-up was significantly larger for patients with radiographically identified tether breakage than for those without tether breakage (31 deg±12 deg vs. 26 deg±12 deg; P =0.002). CONCLUSIONS: The incidence of tether breakage in TAVBT is high, and it is expected to occur in 50% of patients by 36 months postoperatively. LEVEL OF EVIDENCE: Level IV.

Cost Benefit of Implementation of Risk Stratification Models for Adult Spinal Deformity Surgery.

STUDY DESIGN/SETTING: Retrospective cohort study. OBJECTIVE: Assess the extent to which defined risk factors of adverse events are drivers of cost-utility in spinal deformity (ASD) surgery. METHODS: ASD patients with 2-year (2Y) data were included. Tertiles were used to define high degrees of frailty, sagittal deformity, blood loss, and surgical time. Cost was calculated using the Pearl Diver registry and cost-utility at 2Y was compared between cohorts based on the number of risk factors present. Statistically significant differences in cost-utility by number of baseline risk factors were determined using ANOVA, followed by a generalized linear model, adjusting for clinical site and surgeon, to assess the effects of increasing risk score on overall cost-utility. RESULTS: By 2 years, 31% experienced a major complication and 23% underwent reoperation. Patients with ≤2 risk factors had significantly less major complications. Patients with 2 risk factors improved the most from baseline to 2Y in ODI. Average cost increased by $8234 per risk factor (R2 = .981). Cost-per-QALY at 2Y increased by $122,650 per risk factor (R2 = .794). Adjusted generalized linear model demonstrated a significant trend between increasing risk score and increasing cost-utility (r2 = .408, P < .001). CONCLUSIONS: The number of defined patient-specific and surgical risk factors, especially those with greater than two, were associated with increased index surgical costs and diminished cost-utility. Efforts to optimize patient physiology and minimize surgical risk would likely reduce healthcare expenditures and improve the overall cost-utility profile for ASD interventions.Level of evidence: III.