Faculty Bibliography

PURPOSE/OBJECTIVE:Adult spinal deformity (ASD) encompasses heterogeneous conditions associated with abnormal spinal alignment, pain, and disability, presenting substantial classification and management challenges. This review examines how cluster analysis identifies distinct ASD phenotypes and whether these classifications support cohort stratification and assessment of outcomes, surgical treatment, and complications. METHODS:This narrative review describes applications of k-means, hierarchical, and two-step clustering in ASD. It examines the use of shared clinical, radiographic, and demographic features to characterize patient subgroups and explores associations between these subgroups and patient-reported outcomes, surgical treatment, and complications. RESULT/RESULTS:Cluster analysis provides a framework for identifying ASD phenotypes that reflect the heterogeneity of clinical presentation and spinal alignment. Reported applications support cohort description, comparisons of surgical treatment and outcomes, and investigation of complication patterns. However, data quality and interpretive complexity remain important limitations. Current evidence primarily supports cohort stratification and hypothesis generation; cluster assignments have not been validated for individual treatment decisions. CONCLUSION/CONCLUSIONS:Cluster analysis is a promising approach for characterizing ASD heterogeneity and informing stratification research. Further validation is needed to establish the clinical utility of cluster-derived phenotypes before their incorporation into individualized treatment planning.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Postoperative thoracolumbar (TL) realignment in patients with adult spinal deformity (ASD) may induce cervical spine (CS) decompensation. This study identifies predictors of CS decompensation after TL surgery and defines a baseline CS-alignment threshold based on C2-pelvic angle (C2-PA) for CS inclusion in the TL construct. METHODS:Patients with ASD undergoing TL fusion to the sacrum with an upper instrumented vertebrae at T2 or below and available baseline radiographs and patient-reported outcome measures (PROMs) were included. CS decompensation was defined as CS surgery or >2 SD above the mean in C2-PA, cervical sagittal vertical axis (cSVA), or T1-slope cervical lordosis (TS-CL) at the studied postoperative time point. RESULTS:One thousand one hundred ninety patients were included; 166 (13.9%) had CS decompensation after TL surgery, including 24 (2.0%) requiring CS extension. CS decompensation was identified in 81 patients (6.8%) at 6 weeks (4 (0.3%) extensions), 13 (1.2%) at 6 months (2 (0.2%)), 43 (3.9%) at 1 year (7 (0.6%)), and 29 (2.8%) at 2 years (11 (0.9%)). Patients with CS decompensation at 6 months showed worse global and CS alignment at 6 weeks (lumbar lordosis: 53.6 vs 46.3; cSVA: 30.5 vs 38.5; P < .05). CS decompensation at 1 year was associated with worse PROMs (physical component score: 39.0 vs 35.4; Scoliosis research society score: 3.6 vs 3.3; P < .05). CS decompensation at 2 years was associated with worse CS alignment at 1 year (TS-CL: 20.8 vs 28.6; cSVA: 31.1 vs 37.8) and worse PROMs at 2 years. Higher baseline C2-PA was associated with shorter time to CS decompensation. Cox modeling identified baseline C2-PA (hazard ratio [HR] 1.05, 95% CI, 1.03-1.06), TS-CL (HR 1.05, 95% CI, 1.03-1.06), surgical invasiveness (HR 0.99, 95% CI, 0.98-0.99), and upper thoracic instrumentation (HR 2.9, 95% CI, 1.8-4.7) as predictors of CS decompensation, with a C2-PA threshold of 26.2°. CONCLUSION/CONCLUSIONS:Two years after TL ASD surgery, 13.9% had CS decompensation, with 14% requiring CS extension. Baseline CS alignment independently predicted CS decompensation. Patients with preoperative C2-PA >26.2° may benefit from CS inclusion in the TL construct after external validation of this threshold by future research.

OBJECTIVE:The T4-L1 pelvic angle (T4-L1PA) has been proposed as a novel alignment target associated with mechanical complications in long-segment adult spinal deformity (ASD) surgery. However, its relationship to proximal junctional failure (PJF) and its relevance in shorter thoracolumbar constructs remain unclear. The aim of this study was to evaluate whether T4-L1PA and L1 pelvic angle (L1PA) guidelines predict PJF in ASD surgery and to examine how early proximal reciprocal changes influence this relationship. METHODS:A prospective ASD database was reviewed for patients who underwent fusion from the ilium to the thoracic spine with a minimum follow-up of 2 years. Postoperative PJF was defined as 1) revision surgery requiring proximal extension or 2) severe radiographic proximal junctional kyphosis (PJK) (proximal junctional angle [PJA] > 28° and ΔPJA > 22°). Patients were categorized based on adherence to L1PA (0.5 × PI -19 ± 2°) and T4-L1PA (from -3° to 1°) guidelines, stratified by upper instrumented vertebra position (upper thoracic [UT], T2-4; lower thoracic, T9-11). Simulated postoperative alignment was used to assess the effect of the PJA on guideline adherence and failure risk. RESULTS:Among 661 patients (78% female, mean age 65 ± 9 years, mean BMI 28.3 ± 5.7), 17.9% experienced PJF at 2 years (8.3% with revision, 10.4% with severe PJK). Patients with UT UIVs had higher failure rates when L1PA was overcorrected (25.6%) versus matching (12.9%) or undercorrected (11.1%, p = 0.029). In contrast, failure rates across T4-L1PA groups were not different (p = 0.094). The lowest failure rate was identified for either L1PA undercorrected and T4 aligned or L1PA aligned but T4 ventral to L1. For short fusion, no significant differences were found across L1PA guidelines (p = 0.132), and the significant difference in T4-L1PA was not maintained after adjusting for PJA influence on early postoperative alignment (p = 0.148). Similarly, no significant differences were found across the 9 combinations after controlling for PJA influence. CONCLUSIONS:The T4-L1PA concept demonstrated some association with PJF alone in the setting of long fusions, although adjusting L1PA thresholds toward less correction might further improve outcomes. Unfortunately, current targets seem inappropriate for short fusions, and a different framework might be required.

Study DesignRetrospective cohort study.ObjectivesTo characterize longitudinal durability of cervical deformity (CD) correction, identify predictors of alignment failure, and define failure mechanism timing across the first postoperative year.Methodsof 155 operative CD patients in a prospectively maintained multicenter database, 89 had complete four-timepoint radiographic follow-up. Well-alignment was defined as cSVA <4 cm. Patients were grouped as A (maintained), B (corrected then deteriorated), or C (never aligned). Analyses included Cox regression (n=47, 17 events), Kaplan-Meier with restricted mean survival time (RMST), and mixed-effects logistic regression across four timepoints (n=356; ICC=0.36). Concurrent thoracolumbar deformity was excluded.ResultsWell-aligned proportion fell from 48.3% at 3 months to 33.7% at 1 year (A=34%, B=19%, C=47%). DJK was most strongly associated with alignment loss (HR 5.21, 95% CI 1.94-13.98; OR 0.09), with alignment maintained 4.1 versus 9.8 months (RMST difference 5.7, p=0.001). Lower postoperative cSVA paradoxically increased failure hazard (HR 0.58/10 mm, p=0.002). Older patients deteriorated faster (Time×Age OR 0.88, p=0.022). Failure mechanisms shifted from DJK at 3 months (50%) to PJK at 6 months (75%) to global compensation loss at 1 year (71%). No surgical parameters differed between groups.ConclusionsFewer than one-third of patients maintain alignment at 1 year. DJK, advanced age, and lower postoperative cSVA were most strongly associated with failure (17 events; limited precision). Mechanisms appeared to shift from junctional failure early to global decompensation late. Alignment loss was not accompanied by significant 1-year NDI or EQ-5D differences, framing radiographic deterioration as an early surveillance marker rather than clinical failure. Individualized risk stratification and surveillance are supported.

STUDY DESIGN/UNASSIGNED:Retrospective cohort study. OBJECTIVES/UNASSIGNED:Given its high and increasing prevalence in the United States, rheumatoid arthritis (RA) has been a growing area of focus for spine surgeons. The literature regarding the long-term outcomes of RA patients undergoing adult spinal deformity (ASD) surgery is limited. Thus, the purpose of this study was to compare the postoperative complications and revisions through 2 years postoperatively between patients with and without RA undergoing ASD surgery. METHODS/UNASSIGNED:A retrospective analysis of the New York Statewide Planning and Research Cooperative System database was performed. Patients undergoing spinal fusion for ASD were selected for and divided into two cohorts based on RA status. Univariate analysis compared demographics, complications, length of stay, and revisions between cohorts. Multivariate logistic regression models, adjusted for age, gender, number of levels fused, and Deyo score. RESULTS/UNASSIGNED:= 0.03). CONCLUSION/UNASSIGNED:This study found RA to be an independent risk factor for increased complications and subsequent revision surgery after fusion surgery for ASD. Surgeons can use this data when counselling patients with RA regarding their operative risk.

OBJECTIVE:Adult spinal deformity (ASD) surgery patients maintain upright posture by using numerous compensatory mechanisms. The distribution of this compensation throughout the skeleton has not been fully investigated. METHODS:Patients with lumbar deformity curves undergoing fusion from T10 to the pelvis were included. Groups were stratified by Scoliosis Research Society (SRS)-Schwab sagittal deformity severity (mild, moderate, and severe). Compensation was determined based on the published values of asymptomatic individuals by Bao et al. (2018), with patients outside 1 standard deviation of the mean values deemed to be compensating. Adequate deformity correction was determined based on matching published sagittal age-adjusted score (SAAS) criteria. Means comparisons tests assessed differences between cohorts at each time point. RESULTS:In total, 379 ASD patients were included (mean age 66.7 ± 10.2 years, body mass index 28.4 ± 5.4 kg/m2, Charlson Comorbidity Index 1.20 ± 1.73). In total, 23.8% of patients had mild deformity, 19.2% moderate, and 57% severe. The severe deformity cohort generally demonstrated the highest rates of compensation across all regions at different time points. At baseline, the severe and moderate cohorts demonstrated predominantly lower limb-dominant compensation, with the highest frequencies of compensation seen at the knee and pelvis. In the mild cohort, knee compensation was relieved by 1 year when adequate correction was achieved. For the moderate cohort, hip and pelvic compensation were relieved first, with knee compensatory relief occurring by 2 years. For the severe cohort, pelvic compensation was relieved first, with global lower limb and thoracic compensation subsequently occurring. CONCLUSIONS:There is notable variation in how ASD patients compensate as the severity of their deformity progresses. There is also variation in how these patterns are altered postoperatively.

STUDY DESIGN/METHODS:Retrospective review of multicenter, prospective cervical deformity database. OBJECTIVE:To compare outcomes of extension of fusion to the cervical spine versus the upper thoracic (UT) spine. SUMMARY OF BACKGROUND DATA/BACKGROUND:Proximal junctional kyphosis (PJK) management after thoracolumbar fusion requires extension of fusion to the proximal spinal segments. Unlike extensions to the less mobile thoracic segments, crossing the cervicothoracic junction (CTJ) involves more mobile cervical segments and creates different biomechanical influences and clinical outcomes. No study has compared the outcomes of extending fusion to the cervical versus the UT spine. METHODS:Patients with thoracic PJK who underwent revision with extension of fusion to either the cervical or UT (T1 or T2) spine were identified in a multicenter, prospective cervical deformity database. Patients with cervical upper instrumented vertebra (UIV) were subdivided into lower cervical (LC; C4-7) and upper cervical (UC; and occiput-C3) groups. Baseline demographics, surgical variables, radiographic outcomes, 2-year health-related quality-of-life scores, complications, and revision rates were analyzed. RESULTS:Fifty-one patients (mean age: 60.4±12.9 y; 91% female) with at least 2 years of follow-up were included. Twelve had extension to the UT, 20 to the LC, and 19 to the UC spine. Demographic data, Charlson Comorbidity Index, follow-up duration, surgical parameters, radiographic measurements, recurrent PJK and reoperation rates, and 2-year patient-reported outcome scores were similar across groups. The instrumentation failure rate was higher in the LC (25%) than in the UT (0%) and UC (8%) groups (P=0.03). CONCLUSIONS:Stopping fusion at T1 or T2 did not result in greater complication or reoperation rates than extending to the cervical spine. The instrumentation-related complication rate was higher for extension to the LC than to the UC or UT spine. Crossing the CTJ should be individualized, but may not prevent additional proximal junctional-level problems in the management of thoracolumbar fusion PJK. LEVEL OF EVIDENCE/METHODS:Level IV.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Circumferential minimally invasive surgery (cMIS) techniques in adult spinal deformity (ASD) surgery may reduce physiological burden compared with open technique, but their utility in octogenarians has not been previously assessed. METHODS:Operative ASD patients aged 80 years or older with complete baseline (BL) and 2-year postoperative radiographic and health-related quality of life data were assessed and compared by surgical technique: open vs cMIS. Propensity score matching aligned groups by BL Charlson Comorbidity Index (CCI), C7-S1 sagittal vertical axis, pelvic incidence minus lumbar lordosis mismatch, and C7 plumb line. BL and peri/postoperative factors were assessed using analysis of variance and Bonferroni-adjusted analysis of covariance while controlling for BL CCI and posterior fusion length. RESULTS:Thirty-four octogenarian ASD patients met inclusion criteria, of whom 29.4% underwent cMIS and 70.6% underwent open correction. cMIS patients were less likely to require surgical intensive care unit (10% vs 75%, P < .001) and had shorter hospital stays (4.6 vs 10.1 days, P = .013). Open patients reported higher Scoliosis Research Society-22 Appearance and Mental domain scores (both P < .005) and more frequently reached minimal clinically important difference in both domains by 2 years (P = .025, .024). cMIS patients more often required reoperation for radiographic sagittal imbalance by 2 years when controlling for CCI and levels fused (20.0% vs 8.3%, P < .001). No deaths occurred in either group by 2 years. CONCLUSION/CONCLUSIONS:In octogenarians undergoing ASD surgery, cMIS reduced physiological burden but had higher reoperation rates, whereas open surgery showed greater durability.

STUDY DESIGN/METHODS:Retrospective cohort study. OBJECTIVES/OBJECTIVE:This study aimed to determine whether substance abuse among adolescent idiopathic scoliosis (AIS) patients is associated with increased odds of subsequent new-onset mental health disease (MHD). SUMMARY OF BACKGROUND DATA/BACKGROUND:MHD prevalence in patients with a substance abuse history has been well-described. However, the impact of current or historical substance abuse/dependence in AIS patients on the risk of subsequent development of new-onset MHDs is unknown. METHODS:The New York SPARCS database was reviewed to identify all 10-25-year-old AIS patients and stratified by prior or concurrent substance abuse (AIS-Sub) versus no history of substance abuse (AIS-NoSub). Cohorts were 1:1 propensity score-matched, and various comparisons were made, including incidence of subsequent MHDs. Binary stepwise logistic regressions were utilized to calculate odds ratios (OR) of developing any MHDs based on baseline substance abuse. RESULTS:386 AIS patients were included (193 AIS-Sub and 193 AIS-NoSub). At baseline, there were no significant differences between patient cohorts in demographic factors. AIS-Sub patients had higher rates of new-onset subsequent overall MHDs (16.1% vs. 3.6%, P<0.001), with only depressive disorder showing a significantly higher incidence when examining individual MHDs (10.9% vs. 0.5%, P<0.001). Logistic regression analyses revealed that baseline substance abuse was independently associated with subsequent diagnosis of either any MHD (OR=6.8, 95% CI: 2.6-17.3, P=0.001), or new-onset depressive disorder (OR=47.0, 95% CI: 3.9-568.7, P=0.002); but was not associated with the development of anxiety, stress, sleep, or eating disorders. CONCLUSIONS:AIS patients with prior or current substance abuse/dependence were at increased 2-year risk of developing any new-onset MHD, specifically depressive disorders. This data may guide preoperative screening and optimization efforts for surgeons, as MHDs have been associated with poor outcomes following spine surgery. LEVEL OF EVIDENCE/METHODS:Level III-retrospective cohort study.

AIMS/UNASSIGNED:Proximal junctional kyphosis (PJK) remains a major complication after surgery for adult spinal deformity (ASD). While postoperative alignment is a recognized modifiable risk factor, objective methods for selecting the upper instrumented vertebra (UIV), a key modifiable factor, are lacking. We aimed to determine whether preoperative sagittal alignment, specifically cervicothoracic alignment, predicts the risk of PJK, and whether this risk can be mitigated by UIV selection, focusing on factors available at the time of surgical planning. METHODS/UNASSIGNED:From a multicentre, prospective ASD registry, we identified patients who had undergone fusion to the sacrum or pelvis and had an upper (T1-T5) or lower thoracic (T9-L1) UIV, with a two-year or more radiological follow-up, excluding those with a previous fusion over more than four levels. The primary outcome was PJK within two years. Multivariable logistic regression modelled the risk of PJK by UIV region, preoperative C2-T9 pelvic angle (PA), age, sex, and pelvic incidence, testing for interaction between UIV region and C2-T9 PA. Adjusted absolute risk reduction (ARR) and number needed to be exposed (NNEB) were calculated. Multivariable linear regression estimated two-year patient-reported outcome measures, adjusting for baseline scores, age, UIV, and PJK. RESULTS/UNASSIGNED:A total of 627 patients across 20 centres were included (median age 66 years (IQR 59 to 70); 483 (77%) female). The UIV was lower thoracic in 380 (61%) and upper thoracic in 247 (39%) patients. PJK occurred in 149 (39%) lower thoracic and 38 (15%) upper thoracic UIV patients. There was a significant interaction (p = 0.028) between preoperative C2-T9 PA and UIV region. At a preoperative C2-T9 PA of 14° (cohort median), an upper thoracic UIV had an adjusted ARR of 36% and NNEB was 2.8. Females had an adjusted odds ratio of 1.62 (95% CI 1.03 to 2.59; p = 0.042) for PJK. CONCLUSION/UNASSIGNED:Worse preoperative sagittal malalignment, measured by C2-T9 PA, was associated with a higher risk of PJK and depended on UIV region. An upper thoracic UIV in patients with high preoperative C2-T9 PA may reduce PJK.