Complex Adult Spinal Deformity Research Articles

Comparison of clinical and radiological outcomes of three-column lumbar osteotomies with and without interbody cages for adult spinal deformity.

Correcting sagittal malalignment in adult spinal deformity (ASD) is a challenging task, often requiring complex surgical interventions like pedicle subtraction osteotomies (PSOs). Different types of three-column osteotomies (3COs), including Schwab 3, Schwab 4, Schwab 4 with interbody cages, and the "sandwich" technique, aim to optimize alignment and fusion outcomes. The role of interbody cages in enhancing fusion and segmental correction remains unclear. This study aimed to compare outcomes among these 4 3CO techniques, evaluating the impact of cage use at the osteotomy site on postoperative radiographic imaging and clinical outcomes. This is a multicenter retrospective study utilizing data from a prospective multicenter database of patients undergoing complex ASD surgery. Ninety-seven patients who underwent 1 of 4 3CO techniques for thoracolumbar ASD correction with at least 2 years of follow-up were included. The sample consisted of 29 patients who underwent Schwab 3 osteotomy, 20 Schwab 4, 28 Schwab 4 with interbody cages, and 20 who underwent "sandwich" osteotomy. The Scoliosis Research Society-22 revised (SRS22r) questionnaire evaluating pain, activity, appearance, mental health, and satisfaction was used to evaluate patient reported outcomes and radiographic measures including segmental lordosis and fusion rates determined by 3 blinded reviewers were used to evaluate physiologic outcomes. This study analyzed demographic data, radiographic outcomes, patient-reported outcomes, complications, and fusion rates over a 2-year follow-up period. Fusion status was determined via serial radiographs and evaluated independently by 3 blinded reviewers. Univariate and multivariate statistical analyses were performed to assess differences among the groups and the impact of interbody cage use on outcomes. Patients undergoing "sandwich" osteotomy exhibited worse preoperative leg pain scores and lower SRS22r activity (p=.015), appearance (p=.007), and mental health domain scores (p=.0015). No differences in complications were found among groups (p>.05). Patients who underwent osteotomy with a cage were more likely to have had previous spine fusion (91.7% vs. 71.4%, p=.010). Additionally, these patients had lower preoperative SRS22r mental domain (2.9±1 vs. 3.5±1, p=.009), satisfaction (2.3±1 vs. 2.7±1.2, p=.034), and SRS22r total scores (2.3±0.6 vs. 2.6±0.6, p=.0026) but demonstrated the greatest improvement in the mental health domain (0.9±0.7 vs. 0.3±0.9, p=.002). Cage use was associated with a larger mean change in segmental lordosis at the osteotomy site (32.9±9.6 vs. 28.7±9.5, p=.038). Fusion rates were significantly higher in the cage group (79.2% vs. 55.1%, p=.0012). Regression analysis identified cage use as an independent predictor for fusion (odds ratio, 3.338; 95% confidence interval, 1.108-10.054, p=.032). Interbody cage use at the osteotomy site during 3COs for ASD correction was associated with improved fusion rates and greater segmental lordosis without increasing complication rates. Incorporating cages may provide enhanced alignment and fusion outcomes in complex ASD surgeries.

Redefining Clinically Significant Blood Loss in Complex Adult Spine Deformity Surgery.

Retrospective analysis of prospectively-collected data. This study aims to define clinically relevant blood loss in adult spinal deformity (ASD) surgery. Current definitions of excessive blood loss following spine surgery are highly variable and may be suboptimal in predicting adverse events (AE). Adults undergoing complex ASD surgery were included. Estimated blood loss (EBL) was extracted for investigation, and estimated blood volume loss (EBVL) was calculated by dividing EBL by the preoperative blood volume utilizing Nadler's formula. LASSO regression was performed to identify five variables from demographic and peri-operative parameters. Logistic regression was subsequently performed to generate a receiver operating characteristics (ROC) curve and estimate an optimal threshold for EBL and EBVL. Finally, the proportion of patients with AE plotted against EBL and EBVL to confirm the identified thresholds. In total 552 patients were included with a mean age of 60.7±15.1 years, 68% females, mean CCI was 1.0±1.6, and 22% experienced AEs. LASSO regression identified ASA score, baseline hypertension, preoperative albumin, and use of intra-operative crystalloids as the top predictors of an AE, in addition to EBL/EBVL. Logistic regression resulted in ROC curve which was used to identify a cut-off of 2.3 liters of EBL and 42% for EBVL. Patients exceeding these thresholds had AE rates of 36% (odds-ratio: 2.1, 95% CI [1.2-3.6]) and 31% (odds-ratio: 1.7, 95% CI [1.1-2.8]), compared to 21% for those below the thresholds of EBL and EBVL, respectively. In complex ASD surgery, intraoperative EBL of 2.3 liters and an EBVL of 42% are associated with clinically-significant AEs. These thresholds may be useful in guiding preoperative-patient-counseling, healthcare system quality initiatives, and clinical perioperative bloodloss management strategies in patients undergoing complex spine surgery. Additionally, similar methodology could be performed in other specialties to establish procedure-specific clinically-relevant bloodloss thresholds.

Impact of Knee Osteoarthritis and Arthroplasty on Full Body Sagittal Alignment in Adult Spinal Deformity Patients.

Retrospective analysis of prospectively collected data. This study evaluates the impact of knee osteoarthritis (OA) and knee arthroplasty on alignments and patient-reported outcomes measures (PROMS) of patients undergoing adult spinal deformity (ASD) corrective surgery. The relationship between knee OA and spinal alignment in patients with ASD is incompletely understood. It is also unknown how patients with knee arthroplasty and ASD compare to ASD patients with native knees. Baseline full-body radiographs were used, and hip and knee OA were graded by two independent reviewers using the KL classification. Spinopelvic parameters and PROMs were compared across the different knee OA groups and compared between patients with knee replacement and native knees. 199 patients with bilateral non severe OA (G1), 31 patients with unilateral severe knee OA (G2), and 60 patients with bilateral severe knee OA (G3). Patients with severe knee OA presented with worse spinopelvic parameters. However, after multivariable regression analysis controlling for age, frailty, PI, T1PA, knee OA was an independent predictor of knee flexion (G1:-0.02±7.3, G2: 7.8±9.4, G3: 4.5±8.7, P<0.001), and ankle dorsiflexion (G1: 2.3±4.0, G2: 6.6±4.5, G3: 5.1±4.1, P<0.001). There was no difference in PROMs (P>0.05). Secondary analysis included 96 patients: 48 patients (50%) with non-severe knee OA, and 48 patients (50%) with knee replacement. There was no difference in radiographic parameters or PROMs between the groups. In this study of complex ASD patients, patients with worse spinal deformity were more likely to have concomitant knee OA. Knee OA was shown to be a predictor of knee flexion and ankle dorsiflexion angles, but was not associated with worse PROMs in this study population. Patients with knee arthroplasty, however, had comparable spinal alignment and PROMs relative to those with mild OA.

When is staging complex adult spinal deformity advantageous? Identifying subsets of patients who benefit from staged interventions.

The objective of this study was to identify baseline patient and surgical factors predictive of optimal outcomes in staged versus same-day combined-approach surgery. Adult spinal deformity (ASD) patients with baseline and perioperative (by 6 weeks) data were stratified based on single-stage (same-day) or multistage (staged) surgery, excluding planned multiple hospitalizations. Means comparison analyses were used to assess baseline demographic, radiographic, and surgical differences between cohorts. Backstep logistic regression and conditional inference tree analysis were used to identify variable thresholds associated with study-specific definitions of an optimal outcome in each cohort, defined as no intraoperative or surgery-related in-hospital adverse event. There were 439 patients with complex ASD in the dataset (mean age 64.0 ± 9.3 years, 68% female, mean BMI 28.7 ± 5.5 kg/m2). Overall, 58.8% of patients were in the same-day group, while 41.2% were in the staged group. Demographically, cohorts were not significantly different (p > 0.05), but staged patients were more frail per total Edmonton Frail Scale score (p = 0.043). Staged patients also reported greater numeric rating scale scores for back pain than same-day patients (p = 0.002). Cohorts were comparable in magnitude of planned correction of C7-S1 sagittal vertical axis, pelvic incidence-lumbar lordosis (PI-LL) mismatch, and T4-12 kyphosis (all p > 0.05). Controlling for baseline age, frailty, and number of levels fused, staged patients reported significantly higher PROMIS Discretionary Social Activities scores by 6 weeks (p = 0.029). Radiographic outcomes by 6 weeks were comparable between cohorts, in terms of both magnitude of change from baseline and overall result (all p > 0.05). Same-day patients were significantly more likely to experience in-hospital complications (p = 0.013). When considering frailty thresholds for staging, only a Charlson Comorbidity Index ≤ 1.0 was associated with optimal outcome in same-day patients, while Edmonton Frail Scale score ≥ 7 (p = 0.036), ≥ 9 levels fused (p = 0.016), and baseline PI-LL mismatch ≥ 15.3° (p = 0.028) were associated with optimal outcome for staged patients. Yet, staging alone was not significantly associated with an optimal outcome perioperatively (p = 0.056). While staged and same-day combined-approach surgeries yield comparable radiographic and patient-reported outcomes, certain subsets of complex ASD patients may benefit from staged surgery despite the invariably increased hospital length of stay. Individuals with increased frailty, moderate to severe PI-LL mismatch, and increased anticipated number of levels fused may experience a lower risk of perioperative adverse events if they undergo a staged procedure. Clinical trial registration no.: NCT04194138 (ClinicalTrials.gov).

High-Dose TXA Is Associated with Less Blood Loss Than Low-Dose TXA without Increased Complications in Patients with Complex Adult Spinal Deformity.

Tranexamic acid (TXA) is commonly utilized to reduce blood loss in adult spinal deformity (ASD) surgery. Despite its widespread use, there is a lack of consensus regarding the optimal dosing regimen. The aim of this study was to assess differences in blood loss and complications between high, medium, and low-dose TXA regimens among patients undergoing surgery for complex ASD. A multicenter database was retrospectively analyzed to identify 265 patients with complex ASD. Patients were separated into 3 groups by TXA regimen: (1) low dose (<20-mg/kg loading dose with ≤2-mg/kg/hr maintenance dose), (2) medium dose (20 to 50-mg/kg loading dose with 2 to 5-mg/kg/hr maintenance dose), and (3) high dose (>50-mg/kg loading dose with ≥5-mg/kg/hr maintenance dose). The measured outcomes included blood loss, complications, and red blood cell (RBC) units transfused intraoperatively and perioperatively. The multivariable analysis controlled for TXA dosing regimen, levels fused, operating room time, preoperative hemoglobin, 3-column osteotomy, and posterior interbody fusion. The cohort was predominantly White (91.3%) and female (69.1%) and had a mean age of 61.6 years. Of the 265 patients, 54 (20.4%) received low-dose, 131 (49.4%) received medium-dose, and 80 (30.2%) received high-dose TXA. The median blood loss was 1,200 mL (interquartile range [IQR], 750 to 2,000). The median RBC units transfused intraoperatively was 1.0 (IQR, 0.0 to 2.0), and the median RBC units transfused perioperatively was 2.0 (IQR, 1.0 to 4.0). Compared with the high-dose group, the low-dose group had increased blood loss (by 513.0 mL; p = 0.022) as well as increased RBC units transfused intraoperatively (by 0.6 units; p < 0.001) and perioperatively (by 0.3 units; p = 0.024). The medium-dose group had increased blood loss (by 491.8 mL; p = 0.006) as well as increased RBC units transfused intraoperatively (by 0.7 units; p < 0.001) and perioperatively (by 0.5 units; p < 0.001) compared with the high-dose group. Patients with ASD who received high-dose intraoperative TXA had fewer RBC transfusions intraoperatively, fewer RBC transfusions perioperatively, and less blood loss than those who received low or medium-dose TXA, with no differences in the rates of seizure or thromboembolic complications. Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Spinal cord injury in high-risk complex adult spinal deformity surgery: review of incidence and outcomes from the Scoli-RISK-1 study

Study designClinical case series.ObjectiveTo describe the cause, treatment and outcome of 6 cases of perioperative spinal cord injury (SCI) in high-risk adult deformity surgery.SettingAdult spinal deformity patients were enrolled in the multi-center Scoli-RISK-1 cohort study.MethodsA total of 272 patients who underwent complex adult deformity surgery were enrolled in the prospective, multi-center Scoli-RISK-1 cohort study. Clinical follow up data were available up to a maximum of 2 years after index surgery. Cases of perioperative SCI were identified and an extensive case review was performed.ResultsSix individuals with SCI were identified from the Scoli-RISK-1 database (2.2%). Two cases occurred intraoperatively and four cases occurred postoperatively. The first case was an incomplete SCI due to a direct intraoperative insult and was treated postoperatively with Riluzole. The second SCI case was caused by a compression injury due to overcorrection of the deformity. Three cases of incomplete SCI occurred; one case of postoperative hematoma, one case of proximal junctional kyphosis (PJK) and one case of adjacent segment disc herniation. All cases of post-operative incomplete SCI were managed with revision decompression and resulted in excellent clinical recovery. One case of incomplete SCI resulted from infection and PJK. The patient’s treatment was complicated by a delay in revision and the patient suffered persistent neurological deficits up to six weeks following the onset of SCI.ConclusionDespite the low incidence in high-risk adult deformity surgeries, perioperative SCI can result in devastating consequences. Thus, appropriate postoperative care, follow up and timely management of SCI are essential.

Contemporary utilization of three-column osteotomy techniques in a prospective complex spinal deformity multicenter database: implications on full-body alignment and perioperative course.

Research has focused on the increased correction from a three-column osteotomy (3CO) during adult spinal deformity (ASD) surgery. However, an in-depth analysis on the performance of a 3CO in a cohort of complex spinal deformity cases has not been described. This is a retrospective study on a prospectively enrolled, complex ASD database. This study aimed to determine if three-column osteotomies demonstrate superior benefit in correction of complex sagittal deformity at the cost of increased perioperative complications. Surgical complex adult spinal deformity patients were included and grouped into thoracolumbar 3COs compared to those who did not have a 3CO (No 3CO) (remaining cohort). Rigid deformity was defined as ΔLL less than 33% from standing to supine. Severe deformity was defined as global (SVA > 70mm) or C7-PL > 70mm, or lumbopelvic (PI-LL > 30°). Means comparison tests assessed correction by 3CO grade/location. Multivariate analysis controlling for baseline deformity evaluated outcomes up to six weeks compared to No 3CO. 648 patients were included (Mean age 61 ± 14.6years, BMI 27.55 ± 5.8kg/m2, levels fused: 12.6 ± 3.8). 126 underwent 3CO, a 20% higher usage than historical cohorts. 3COs were older, frail, and more likely to undergo revision (OR 5.2, 95% CI [2.6-10.6]; p < .001). 3COs were more likely to present with both severe global/lumbopelvic deformity (OR 4), 62.4% being rigid. 3COs had greater use of secondary rods (OR 4st) and incurred 4 times greater risk for: massive blood loss (> 3500mL), longer LOS, SICU admission, perioperative wound and spine-related complications, and neurologic complications when performed below L3. 3COs had similar HRQL benefit, but higher perioperative opioid use. Mean segmental correction increased by grade (G3-21; G4-24; G5-27) and was 4 × greater than low-grade osteotomies, especially below L3 (OR 12). 3COs achieved 2 × greater spinopelvic correction. Higher grades properly distributed lordosis 50% of the time except L5. Pelvic compensation and non-response were relieved more often with increasing grade, with greater correction in all lower extremity parameters (p < .01). Due to the increased rate of complications, 3COs trended toward higher perioperative cost ($42,806 vs. $40,046, p = .086). Three-column osteotomy usage in contemporary complex spinal deformities is generally limited to more disabled individuals undergoing the most severe sagittal and coronal realignment procedures. While there is an increased perioperative cost and prolongation of length of stay with usage, these techniques represent the most powerful realignment techniques available with a dramatic impact on normalization at operative levels and reciprocal changes.

Precise execution of personalized surgical planning using three-dimensional printed guide template in severe and complex adult spinal deformity patients requiring three-column osteotomy: a retrospective, comparative matched-cohort study

BackgroundThe surgical treatment of severe and complex adult spinal deformity (ASD) commonly required three-column osteotomy (3-CO), which was technically demanding with high risk of neurological deficit. Personalized three dimensional (3D)-printed guide template based on preoperative planning has been gradually applied in 3-CO procedure. The purpose of this study was to compare the efficacy, safety, and precision of 3D-printed osteotomy guide template and free-hand technique in the treatment of severe and complex ASD patients requiring 3-CO.MethodsThis was a single-centre retrospective comparative cohort study of patients with severe and complex ASD (Cobb angle of scoliosis > 80° with flexibility < 25% or focal kyphosis > 90°) who underwent posterior spinal fusion and 3-CO between January 2020 to January 2023, with a minimum 12 months follow-up. Personalized computer-assisted three-dimensional osteotomy simulation was performed for all recruited patients, who were further divided into template and non-template groups based on the application of 3D-printed osteotomy guide template according to the surgical planning. Patients in the two groups were age- and gender- propensity-matched. The radiographic parameters, postoperative neurological deficit, and precision of osteotomy execution were compared between groups.ResultsA total of 40 patients (age 36.53 ± 11.98 years) were retrospectively recruited, with 20 patients in each group. The preoperative focal kyphosis (FK) was 92.72° ± 36.77° in the template group and 93.47° ± 33.91° in the non-template group, with a main curve Cobb angle of 63.35° (15.00°, 92.25°) and 64.00° (20.25°, 99.20°), respectively. Following the correction surgery, there were no significant differences in postoperative FK, postoperative main curve Cobb angle, correction rate of FK (54.20% vs. 51.94%, P = 0.738), and correction rate of main curve Cobb angle (72.41% vs. 61.33%, P = 0.101) between the groups. However, the match ratio of execution to simulation osteotomy angle was significantly greater in the template group than the non-template group (coronal: 89.90% vs. 74.50%, P < 0.001; sagittal: 90.45% vs. 80.35%, P < 0.001). The operating time (ORT) was significantly shorter (359.25 ± 57.79 min vs. 398.90 ± 59.48 min, P = 0.039) and the incidence of postoperative neurological deficit (5.0% vs. 35.0%, P = 0.018) was significantly lower in the template group than the non-template group.ConclusionPerforming 3-CO with the assistance of personalized 3D-printed guide template could increase the precision of execution, decrease the risk of postoperative neurological deficit, and shorten the ORT in the correction surgery for severe and complex ASD. The personalized osteotomy guide had the advantages of 3D insight of the case-specific anatomy, identification of osteotomy location, and translation of the surgical planning or simulation to the real surgical site.

Spine surgeon versus AI algorithm full-length radiographic measurements: a validation study of complex adult spinal deformity patients.

Spinal measurements play an integral role in surgical planning for a variety of spine procedures. Full-length imaging eliminates distortions that can occur with stitched images. However, these images take radiologists significantly longer to read than conventional radiographs. Artificial intelligence (AI) image analysis software that can make such measurements quickly and reliably would be advantageous to surgeons, radiologists, and the entire health system. Institutional Review Board approval was obtained for this study. Preoperative full-length standing anterior-posterior and lateral radiographs of patients that were previously measured by fellowship-trained spine surgeons at our institution were obtained. The measurements included lumbar lordosis (LL), greatest coronal Cobb angle (GCC), pelvic incidence (PI), coronal balance (CB), and T1-pelvic angle (T1PA). Inter-rater intra-class correlation (ICC) values were calculated based on an overlapping sample of 10 patients measured by surgeons. Full-length standing radiographs of an additional 100 patients were provided for AI software training. The AI algorithm then measured the radiographs and ICC values were calculated. ICC values for inter-rater reliability between surgeons were excellent and calculated to 0.97 for LL (95% CI 0.88-0.99), 0.78 (0.33-0.94) for GCC, 0.86 (0.55-0.96) for PI, 0.99 for CB (0.93-0.99), and 0.95 for T1PA (0.82-0.99). The algorithm computed the five selected parameters with ICC values between 0.70 and 0.94, indicating excellent reliability. Exemplary for the comparison of AI and surgeons, the ICC for LL was 0.88 (95% CI 0.83-0.92) and 0.93 for CB (0.90-0.95). GCC, PI, and T1PA could be determined with ICC values of 0.81 (0.69-0.87), 0.70 (0.60-0.78), and 0.94 (0.91-0.96) respectively. The AI algorithm presented here demonstrates excellent reliability for most of the parameters and good reliability for PI, with ICC values corresponding to measurements conducted by experienced surgeons. In future, it may facilitate the analysis of large data sets and aid physicians in diagnostics, pre-operative planning, and post-operative quality control.

Persistent Lower Extremity Compensation for Sagittal Imbalance After Surgical Correction of Complex Adult Spinal Deformity: A Radiographic Analysis of Early Impact.

Achieving spinopelvic realignment during adult spinal deformity (ASD) surgery does not always produce ideal outcomes. Little is known whether compensation in lower extremities (LEs) plays a role in this disassociation. The objective is to analyze lower extremity compensation after complex ASD surgery, its effect on outcomes, and whether correction can alleviate these mechanisms. We included patients with complex ASD with 6-week data. LE parameters were as follows: sacrofemoral angle, knee flexion angle, and ankle flexion angle. Each parameter was ranked, and upper tertile was deemed compensation. Patients compensating and not compensating postoperatively were propensity score matched for body mass index, frailty, and T1 pelvic angle. Linear regression assessed correlation between LE parameters and baseline deformity, demographics, and surgical details. Multivariate analysis controlling for baseline deformity and history of total knee/hip arthroplasty evaluated outcomes. Two hundred and ten patients (age: 61.3 ± 14.1 years, body mass index: 27.4 ± 5.8 kg/m2, Charlson Comorbidity Index: 1.1 ± 1.6, 72% female, 22% previous total joint arthroplasty, 24% osteoporosis, levels fused: 13.1 ± 3.8) were included. At baseline, 59% were compensating in LE: 32% at hips, 39% knees, and 36% ankles. After correction, 61% were compensating at least one joint. Patients undercorrected postoperatively were less likely to relieve LE compensation (odds ratio: 0.2, P = .037). Patients compensating in LE were more often undercorrected in age-adjusted pelvic tilt, pelvic incidence, lumbar lordosis, and T1 pelvic angle and disproportioned in Global Alignment and Proportion (P < .05). Patients matched in sagittal age-adjusted score at 6 weeks but compensating in LE were more likely to develop proximal junctional kyphosis (odds ratio: 4.1, P = .009) and proximal junctional failure (8% vs 0%, P = .035) than those sagittal age-adjusted score-matched and not compensating in LE. Perioperative lower extremity compensation was a product of undercorrecting complex ASD. Even in age-adjusted realignment, compensation was associated with global undercorrection and junctional failure. Consideration of lower extremities during planning is vital to avoid adverse outcomes in perioperative course after complex ASD surgery.

Three-Column Osteotomies: Past, Present, and Future

Three-Column Osteotomies (3CO's) refer to osteotomies that involve surgical removal of parts or all of the posterior, middle and anterior columns of the spine. The indications for using a 3CO in the surgical treatment of Adult Spinal Deformity (ASD) have slowly evolved over time but remains idiosyncratic for surgeons treating complex ASD patients. This manuscript will focus on the past and present use of 3CO's to highlight the changes over time in the indications, techniques, surgical results, complications and outcomes to place these procedures in the proper context to then discuss their probable use among ASD patients in the future.

P22. Identifying tranexamic acid dosing predictive of decreased risk of intraoperative transfusion accounting for body mass index and surgical invasiveness in complex adult spinal deformity surgery

P22. Identifying tranexamic acid dosing predictive of decreased risk of intraoperative transfusion accounting for body mass index and surgical invasiveness in complex adult spinal deformity surgery

Clinical Application of Personalized Digital Surgical Planning and Precise Execution for Severe and Complex Adult Spinal Deformity Correction Utilizing 3D Printing Techniques.

(1) Background: The three-dimensional printing (3DP) technique has been reported to be of great utility in spine surgery. The purpose of this study is to report the clinical application of personalized preoperative digital planning and a 3DP guidance template in the treatment of severe and complex adult spinal deformity. (2) Methods: eight adult patients with severe rigid kyphoscoliosis were given personalized surgical simulation based on the preoperative radiological data. Guidance templates for screw insertion and osteotomy were designed and manufactured according to the planning protocol and used during the correction surgery. The perioperative, and radiological parameters and complications, including surgery duration, estimated blood loss, pre- and post-operative cobb angle, trunk balance, and precision of osteotomy operation with screw implantation were collected retrospectively and analyzed to evaluate the clinical efficacy and safety of this technique. (3) Results: Of the eight patients, the primary pathology of scoliosis included two adult idiopathic scoliosis (ADIS), four congenital scoliosis (CS), one ankylosing spondylitis (AS), and one tuberculosis (TB). Two patients had a previous history of spinal surgery. Three pedicle subtraction osteotomies (PSOs) and five vertebral column resection (VCR) osteotomies were successfully performed with the application of the guide templates. The main cobb angle was corrected from 99.33° to 34.17°, and the kyphosis was corrected from 110.00° to 42.00°. The ratio of osteotomy execution and simulation was 97.02%. In the cohort, the average screw accuracy was 93.04%. (4) Conclusions: The clinical application of personalized digital surgical planning and precise execution via 3D printing guidance templates in the treatment of severe adult rigid deformity is feasible, effective, and easily generalizable. The preoperative osteotomy simulation was executed with high precision, utilizing personalized designed guidance templates. This technique can be used to reduce the surgical risk and difficulty of screw placement and high-level osteotomy.

Can unsupervised cluster analysis identify patterns of complex adult spinal deformity with distinct perioperative outcomes?

The objective of this study was to use an unsupervised cluster approach to identify patterns of operative adult spinal deformity (ASD) and compare the perioperative outcomes of these groups. A multicenter data set included patients with complex surgical ASD, including those with severe deformities, significant surgical complexity, or advanced age who underwent a multilevel fusion. An unsupervised cluster analysis allowing for 10% outliers was used to identify different deformity patterns. The perioperative outcomes of these clusters were then compared using ANOVA, Kruskal-Wallis, and chi-square tests, with p values < 0.05 considered significant. Two hundred eighty-six patients were classified into four clusters of deformity patterns: hyper-thoracic kyphosis (hyper-TK), severe coronal, severe sagittal, and moderate sagittal. Hyper-TK patients had the lowest disability (mean Oswestry Disability Index [ODI] 32.9 ± 17.1) and pain scores (median numeric rating scale [NRS] back score 6, leg score 1). The severe coronal cluster had moderate functional impairment (mean physical component score 34.4 ± 12.3) and pain (median NRS back score 7, leg score 4) scores. The severe sagittal cluster had the highest levels of disability (mean ODI 49.3 ± 15.6) and low appearance scores (mean 2.3 ± 0.7). The moderate cluster (mean 68.8 ± 7.8 years) had the highest pain interference subscores on the Patient-Reported Outcomes Measurement Information System (mean 65.2 ± 5.8). Overall 30-day adverse events were equivalent among the four groups. Fusion to the pelvis was most common in the moderate sagittal (89.4%) and severe sagittal (97.5%) clusters. The severe coronal cluster had more osteotomies per case (median 11, IQR 6.5-14) and a higher rate of 30-day implant-related complications (5.5%). The severe sagittal and hyper-TK clusters had more three-column osteotomies (43% and 32.3%, respectively). Hyper-TK patients had shorter hospital stays. This cohort of patients with complex ASD surgeries contained four natural clusters of deformity, each with distinct perioperative outcomes.

P101. Can AI identify patterns of complex adult spinal deformity with distinct perioperative outcomes?

<h3>BACKGROUND CONTEXT</h3> Adult spinal deformity (ASD) refers to multiple types of spinal deformity. This study used a prospective multicenter database of patients with "complex" surgical ASD to derive a data-driven classification of different deformity patterns, and assessed if such patterns have distinct clinical outcomes. <h3>PURPOSE</h3> Use an AI-based unsupervised approach to identify patterns of ASD. <h3>STUDY DESIGN/SETTING</h3> Retrospective analysis of a multi-center prospective database. <h3>PATIENT SAMPLE</h3> A total of 286 patients with complex ASD who underwent surgical correction. <h3>OUTCOME MEASURES</h3> Operative decision-making and 30-day adverse events. <h3>METHODS</h3> Complex surgical ASD included severe deformity, surgical complexity or advanced age with a multilevel fusion. An unsupervised cluster analysis that allowed for 10% outliers was used to identify different patterns of deformity. Perioperative outcomes of these clusters were then compared using ANOVA, Kustal-Wallis, and Chi-Squared analyses as indicated, with p-value < 0.05 considered significant. <h3>RESULTS</h3> The Hyper-Kyphosis (Hyper TK, n = 31) group had a mean thoracic kyphosis of 82.6±17.6°, lumbar hyperextension (PI-LL: -20.4±14.7°) and relatively straight coronal curvatures. Hyper-Kyphosis patients were the youngest (mean age 48±20 years) and had the lowest disability (mean ODI 32.9±17.1) and pain scores (median NRS back 6 IQR 3 to 8, median NRS leg 1 IQR 0 to 4). The Severe Coronal (Coronal, n = 91) group had a mean thoracic Cobb of 44.7±17.8° and a mean thoraco-lumbar Cobb of 57.9±16.5° with preserved global sagittal alignment. Coronal patients had moderate disability (mean ODI 33.5±18.8), functional impairment (PCD: 34.4±12.3) and pain scores (median NRS back 7 IQR 5 to 8, median NRS leg 4 IQR 0 to 7). The Severe Sagittal (Sev. Sag. n=79) group had a severe spino-pelvic mismatch (42.9±12.9°) and global sagittal deformity (24.3±7.9°). Sev Sag had higher BMIs (28.9±5.9), high levels of disability (mean ODI 49.3±15.6) and low appearance scores (2.3±0.7). Finally, the Moderate Sagittal (Mod. Sag. n=85) group had moderate deformities without distinctive radiographic characteristics, a mean age of 68.8±7.8°, the highest PROMIS pain interference sub-scores (65.2±5.8), high levels of disability (mean ODI 47.6±15.3) and back pain (NRS back 7 IQR 6 to 9), and poor overall quality of life (mean SRS total 2.8±0.6). Thirty-day adverse events were equivalent. Hyper TK and Coronal patients had the longest constructs, but fusion to the pelvis was most common in Mod Sag (89.4%) and Sev Sag (97.5%) deformities. Coronal patients had more osteotomies per case (median 11 IQR 6.5 to 14), longer OR times, and more 30-day implant-related complications (5.5%). Sev Sag and Hyper TK patients were more likely to require a 3-column osteotomy (43% and 32.3%, respectively). Sev Sag deformities were more likely to require interbody implants (29.1%) and operative wound debridement (7.6%). Hyper TK patients had shorter hospital stays. <h3>CONCLUSIONS</h3> AI methodologies identified 4 distinct patient clusters within a large population of surgically treated ASD patients. Each ASD cluster presented with 1) a unique spinal deformity pattern, 2) reported distinct pathognomonic health deficits, 3) received consistent surgical treatment across 11 centers, and 4) had characteristic perioperative complications and hospital stays. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

46. Lower limb compensation in the setting of adult spinal deformity

<h3>BACKGROUND CONTEXT</h3> Numerous studies have reported the interplay between spinal deformity and pelvis compensatory mechanisms, but little data exist evaluating the contribution of lower extremity compensation (LE) to maintain upright posture. We hypothesis that hip, knee and ankle compensation is proportional to the severity of the spinal deformity and varies by demographics. <h3>PURPOSE</h3> Evaluate the association between spinal alignment and lower limbs compensation. <h3>STUDY DESIGN/SETTING</h3> Multicenter, prospective cohort. <h3>PATIENT SAMPLE</h3> This study included 288 patients treated for complex adult spinal deformity (ASD) with full body images available. <h3>OUTCOME MEASURES</h3> Pelvic retroversion (PT), hip extension (SFA), knee flexion (KA), ankle dorsiflexion (AA), pelvic translation (P.Shift) and patient reported outcomes (ODI, PROMIS and SRS-22). <h3>METHODS</h3> Surgical ASD patients were enrolled into a prospective study based on three criteria: deformity severity (PI-LL>25°, TPA>30°, SVA>15cm, TCobb>70° or TLCobb>50°), procedure complexity (>12 levels fused, 3CO or ACR) and/or age (>65 and >7 levels fused). Associations between lower extremity compensation (hip extension, knee flexion, and ankle dorsiflexion) and the magnitude of spinal deformity, patient demographics, patient frailty, and patient-reported outcomes (ODI, SRS, PROMIS-CAT) were assessed via regressions and partial correlations. <h3>RESULTS</h3> A total of 288/329 patients met inclusion criteria (60±15yo, 70.5% female), had moderate to severe spinal deformity (PI-LL:15±24, TPA:24±14, SVA:65±69mm, lumbar Cobb:34±24), and reported high pain (PROMIS pain interference; PI=62.7±7.8) and reduced physical function (PROMIS physical function; PF=35.6±7.6). Lower extremity compensation included pelvic retroversion (PT:24.1± 11.8), hip extension (SFA: 203±10.5), knee flexion (KA:5.5± 9.6), ankle dorsiflexion (AA: 5.3±4.5), and posterior pelvic translation (P.Shift: 30±51mm). Overall, lower extremity compensation increased with age (all p <0.001), BMI and frailty (all p <0.001, except SFA). For a similar PT, women had greater hip extension than men (SFA: 206 vs 200, p <0.001), with less KA (3.6 vs. 10.1, p <0.001), AA, and P.Shift. Lower extremity compensation increased with PI (r=0.2-0.45, p <0.001), TPA (r=0.5-0.9, p <0.001) and correlated with PROMS (ODI:0.26 - 0.37, PROMIS PF: -0.28 - -0.39, SRS Acti.: -0.20 - -0.33). When controlling for deformity severity and PI, most associations between lower limbs compensation and PROMS were lost. However, P.Shift and SFA remained weakly correlated with physical scores (ODI and PROMIS PF). <h3>CONCLUSIONS</h3> The recruitment of LE compensation is overall proportional to the severity of adult spinal deformity, with different patterns observed between men and women. Patients achieved similar PT by recruiting different patterns of LE compensation. Hip extension and posterior pelvic translation are independently associated with impairment in patient-reported outcomes. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

31. Quantifying the contribution of lower limb compensation to upright posture: what happens if ASD patients do not compensate?

<h3>BACKGROUND CONTEXT</h3> Adult spinal deformity (ASD) patients maintain upright posture by compensating through their spine, pelvis and lower extremities. Little data exist quantifying the contribution of lower extremity compensation through the hips, knees, and ankles to maintain upright posture. <h3>PURPOSE</h3> Evaluate the effect of the lower limb compensation by numerically unfolding patients. <h3>STUDY DESIGN/SETTING</h3> Multicenter, prospective cohort. <h3>PATIENT SAMPLE</h3> A total of 288 patients surgically treated for complex ASD with preoperative full body images. <h3>OUTCOME MEASURES</h3> Horizontal distance between vertebra centroid and ankle. <h3>METHODS</h3> Surgical ASD patients were enrolled into a prospective study based on three criteria deformity severity (PI-LL>25°, TPA>30°, SVA>15cm, TCobb>70° or TLCobb>50°), procedure complexity (>12 levels fused, 3CO or ACR) and/or age (>65 and >7 levels fused). Preop full-body images were evaluated and age and PI-adjusted normative values were used to model spine alignment based upon three configurations: COMP (all lower extremity compensatory mechanisms maintained), PARTIAL (removal of ankle dorsiflexion and knee flexion, maintained hip extension), UNCOMP (ankle, knee, and hip compensation eliminated by reset PT to the age and PI norms). The three configurations were compared, and COMP alignment was stratified by TPA percentiles to investigate the offsets from each vertebra to the ankle joint acting as a surrogate of the gravity line in free-standing position. <h3>RESULTS</h3> A total of 288 patients met inclusion criteria (60±15yo, 70.5% female, 27.4±5.9 BMI). COMP spine deformity magnitude included PI-LL 15±24, TPA 24±14, and SVA 65±69mm. As the model transitioned from COMP to UNCOMP alignment, the initial posterior translation of the pelvis decreased significantly to an anterior translation vs the ankle (P.Shift 30 to -7.6 mm). This was associated with a decrease in pelvic retroversion (PT 24.1 to 16.1), hip extension (SFA 203 to 200), knee flexion (KA 5.5 to -0.4), and ankle dorsiflexion (AA 5.3 to 3.7). As a result, the anterior malalignment of the trunk significantly increased SVA (65 to 120mm) and G-SVA (C7-Ankle from 36 to 127 mm), leading to a three-fold increase in bending moments sustained by the ankle joint. The stratification of the COMP position by TPA percentiles revealed that as the deformity increases, the vertebrae above T8 translate anteriorly, those below T10 move posteriorly, with the T8-T10 segment remaining ∼3cm posterior to the ankle joint independently of the deformity severity. <h3>CONCLUSIONS</h3> Removal of lower limbs' compensation revealed an unsustainable truncal malalignment with a three-fold increase of bending moments at the ankle joints. Combined, lower limb compensations permit "reducing" the SVA by two-fold and the C7-ankle SVA by three-fold. From a mechanical point of view, this compensation permits maintaining the trunk center of mass (T9) at a fixed offset of ∼3 cm from the ankle joint. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Randomized, controlled trial of two tranexamic acid dosing protocols in adult spinal deformity surgery.

Tranexamic acid (TXA) is an anti-fibrinolytic effective in reducing blood loss in orthopedic surgery. The appropriate dosing protocol for adult spinal deformity (ASD) surgery is not known. The purpose of this study was to evaluate two TXA protocols [low dose (L): 10mg/kg bolus, 1mg/kg/hr infusion; high dose (H): 50mg/kg, 5mg/kg/hr] in complex ASD surgery. Inclusion criteria were ASD reconstructions with minimum 10 fusion levels or planned 3-column osteotomy (3CO). Standard demographic and surgical data were collected. Intraoperative estimated blood loss (EBL) was calculated by suction canisters minus irrigation plus estimated blood lost in sponges, estimated to the nearest 50mL. Serious adverse events (SAE) were defined a priori as: venothromboembolic event (VTE), cardiac arrhythmia, myocardial infarction, renal dysfunction, and seizure. All SAE were recorded. Simple t tests compared EBL between groups. Mean EBL by total blood volume (TBV), transfusion volume, complications related to TXA were secondary outcomes. Sixty-two patients were enrolled and 52 patients completed the study; 25 were randomized to H and 27 to L. Demographic and surgical variables were not different between the two groups. EBL was not different between groups (H: 1596 ± 933cc, L: 2046 ± 1105cc, p = 0.12, 95% CI: -1022 to 122cc). EBL as a percentage of TBV was lower for the high-dose group (H: 29.5 ± 14.8%, L: 42.5 ± 26.2%, p = 0.03). Intraoperative transfusion volume (H: 961 ± 505cc, L: 1105 ± 808cc, p = 0.5) and post-operative transfusion volume (H: 513 ± 305cc, L: 524 ± 245cc, p = 0.9) were not different. SAE related to TXA were not different (p = 0.7) and occurred in 2 (8%) H and 3 (11%) L. There was one seizure (H), 2 VTE, and 2 arrhythmias. No differences in EBL, transfusion volume, nor SAE were observed between H and L dose TXA protocols. High dose was associated with decreased TBV loss (13%). Further prospective study, with pharmacologic analysis, is required to determine appropriate TXA dosage in ASD surgeries. Therapeutic Level II. The study was registered at Clinicaltrials.gov (NCT02053363) February 3, 2014.

Worse Preoperative Disability is Predictive of Improvement in Disability After Complex Adult Spinal Deformity Surgery.

Retrospective Cohort Study. Few previous studies have examined the relationship between preoperative disability and patient outcomes after complex adult spinal deformity surgery. In this study, we hypothesized that patients with worse preoperative disability would be more likely achieve a clinically significant improvement in their symptoms after surgery. Demographics, comorbidities, surgical data, and health related survey results were analyzed from a consecutive series of adults (≥18years old) who underwent spinal deformity correction, instrumentation, and fusion. Patients included had 6 or more levels fused and their surgery performed at single institution between 2015 and 2018 with minimum 2year follow up. A total of 108 patients met inclusion criteria. Bivariate analysis demonstrated the following as having a greater probability of reaching minimum clinically important difference (MCID) at 2years postoperatively: >50th percentile Oswestry Disability Index (ODI) score (ODI >36), cardiac comorbidities, and use of pelvic fixation, pedicle subtraction osteotomy, and transforaminal lumbar interbody fusion. Conversely, baseline Scoliosis research society score (SRS) >50th percentile (SRS ≥62) and use of vertebral column resection (VCR) were significant predictors of not reaching MCID at 2years. On logistic regression analysis, >50th percentile ODI score (ODI >36) was identified as the only independent predictor of achieving MCID. Patients with greater disability, independent of other preoperative or surgical factors, are more likely to have clinically significant improvement in their daily functioning after complex deformity surgery. For patients who undergo surgical intervention for severe or progressive deformity, including VCR, MCID might be an ineffective outcome measure.

The Scoli-RISK 1 results of lower extremity motor function 5 years after complex adult spinal deformity surgery.

Neurologic complications after complex adult spinal deformity (ASD) surgery are important, yet outcomes are heterogeneously reported, and long-term follow-up of actual lower extremity motor function is unknown. To prospectively evaluate lower extremity motor function scores (LEMS) before and at 5years after surgical correction of complex ASD. Retrospective analysis of a prospective, multicenter, international observational study. The Scoli-RISK-1 study enrolled 272 ASD patients undergoing surgery from 15 centers around the world. Inclusion criteria were Cobb angle of > 80°, corrective osteotomy for congenital or revision deformity and/or 3-column osteotomy. Among patients with 5-year follow-up, comparisons of LEMS to baseline and within each follow-up period were made via documented neurologic exams on each patient. Seventy-seven (28.3%) patients had 5-year follow-up. Among these 77 patients with 5-year follow-up, rates of postoperative LEMS deterioration were: 14.3% hospital discharge, 10.7% at 6 weeks, 6.5% at 6months, 9.5% at 2years and 9.3% at 5years postoperative. During the 2-5year window, while mean LEMS did not change significantly (-0.5, p = 0.442), eight (11.1%) patients deteriorated (of which 3 were ≥ 4 motor points), and six (8.3%) patients improved (of which 2 were ≥ 4 points). Of the 14 neurologic complications, four (28.6%) were surgery-related, three of which required reoperation. While mean LEMS were not impacted in patients with a major surgery-related complication, mean LEMS were significantly lower in patients with neurologic surgery-related complications at discharge (p = 0.041) and 6 months (p = 0.008) between the two groups as well as the change from baseline to 5years (p = 0.041). In 77 patients undergoing complex ASD surgery with 5-year follow-up, while mean LEMS did not change from 2 to 5years, subtle neurologic changes occurred in approximately 1 in 5 patients (11.1% deteriorated; 8.3% improved). Major surgery-related complication did not result in decreased LEMS; however, those with neurologic surgery-related complications continued to have decreased lower extremity motor function at 5years postoperative. These results underscore the importance of long-term follow-up to 5years, using individual motor scores rather than group averages, and comparing outcomes to both baseline and last follow-up.