Richard Hostin

BACKGROUND AND OBJECTIVES: 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: 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.

Study Design.: Retrospective analysis of a prospective multicenter operative cervical deformity (CD) database. Objective.: To determine whether T1 slope (T1S) and C2 slope (C2S) together identify distinct CD phenotypes: cervical-only versus global sagittal deformity, and to compare surgical invasiveness, radiographic correction, and patient-reported outcomes. Summary of Background Data.: T1S and C2S mark cervical malalignment, and elevated T1S has been linked to global sagittal malalignment. Combining them may distinguish CD-only from global deformity on cervical imaging alone. Methods.: Operative CD patients with ≥2 years follow-up and preoperative C2S >30° were stratified by T1S into low T1S–high C2S (LTHC; ≤30°) and high T1S–high C2S (HTHC; >30°). Multivariable regression assessed group effect on 2-year NDI change, adjusted for age, sex, baseline NDI, and posterior levels fused. NDI MCID was set a priori at ≥7 points per the ISSG threshold. Results.: Ninety-two patients met criteria (31 LTHC, 61 HTHC). HTHC patients were older (64.7 vs. 60.0 years; P =0.035) with higher Charlson index ( P =0.022). Preoperatively, HTHC had greater thoracic kyphosis, TPA, cSVA, PI–LL mismatch, and C7 SVA (all P ≤0.010). HTHC underwent more extensive surgery: more posterior levels fused (10.3 vs. 6.7), more circumferential fusions (66.7% vs. 38.7%), and more caudal LIV (T7 vs. T3) (all P P =0.906), but 2-year NDI improvement was smaller in HTHC (−6.2 vs. −14.6 points; P =0.013), and fewer achieved MCID (45.9% vs. 71.0%; P =0.022). HTHC remained an independent predictor of smaller improvement (β=+7.4; P =0.020). Reoperation, DJK, and complication rates did not differ. Conclusions.: Among CD patients with elevated C2S, additional elevated T1S identifies a global-deformity phenotype requiring more invasive correction and showing smaller 2-year patient-reported improvement despite comparable complications. T1S and C2S, measurable on cervical imaging alone, screen for which CD patients warrant full-spine imaging. Level of Evidence.: III (retrospective analysis of prospectively collected multicenter data).

Introduction Predicting post-operative changes in thoracic kyphosis (TK) remains challenging in adult spinal deformity (ASD) surgery. This study aimed to quantify both iatrogenic and reciprocal changes in TK following lumbar correction and assess their maintenance at 2-year follow-up. Methods A retrospective analysis was performed on 356 ASD patients treated with posterior instrumentation from T9–11 to the pelvis, with a minimum 2-year follow-up. TK values were compared with normative data. Multivariate analysis identified thoracolumbar parameters associated with reciprocal thoracic changes and proximal failure. Results Pre-op TK (median 34°) was normal for 59.8% and hypokyphotic for 39.0% of patients. At 6 weeks, 79.1% of initially hypokyphotic patients normalized, while 11.3% of normokyphotic patients deteriorated. Postoperative TK increase correlated with lumbar lordosis gain (p15°, and 9.6% required proximal extension for junctional issues—defined collectively as “thoracic failures” (17.4%). Independent predictors of failure included advanced age (OR 3.6), more proximal lumbar correction (OR 1.9), and pronounced early mid-thoracic kyphosis (OR 2.3). Conclusion In ASD surgery with Upper Instrumented Vertebra (UIV) between T9 and T11, changes in TK were largely proportional to lumbar correction, leading to normalization in most cases. However, age, the location of lumbar correction, and early post-operative thoracic shape independently predicted thoracic failure, highlighting the need for tailored alignment strategies.

Study Design.: Retrospective analysis of a multicenter complex adult spinal deformity (ASD) cohort. Objectives.: Develop a simplified, weighted, and modifiable ASD Frailty Index (o-ASD-FI) that incorporates modifiable health components. Background.: Though newer frailty indices have emerged, none specifically addresses complex ASD while incorporating modifiable health factors. Methods.: Miller’s ASD-FI variables were evaluated via Pearson bivariate correlation and multiple stepwise regression. Ten frailty and three modifiable health factors (depression, diabetes, and osteoporosis) were identified and regressed against mortality, extended length of stay (LOS > 8 d), revisions, and major complications. Coefficients were weighted using Johnson’s method to create the o-ASD-FI (range: 0 – 18). Frailty categories were defined as: not frail (P P P P <0.01. Conclusions.: The newly developed simplified, weighted, and optimizable ASD Frailty Index (o-ASD-FI) incorporates modifiable health components, providing a robust assessment of physiological status and potentially superior risk stratification compared with existing tools for both primary and revision complex spinal deformity surgery. Level of Evidence: III

Study Design.: Retrospective review of the prospectively enrolled, multicenter ASD database. Objective.: We sought to compare clinical and economic outcomes for ASD patients with poor-bone-health versus those with normal-bone-health. Summary of Background Data.: Osteoporosis is a common comorbidity in the adult spinal deformity (ASD) population, with a reported prevalence of 14-29%. Methods.: Patients were categorized into five guideline-concordant cohorts: Confirmed-Osteoporosis (COP: patients with osteopenia or osteoporosis based on DEXA values or a formal preoperative diagnosis); Fracture Osteoporosis (Fx: patients with fragility fractures); Fracture-without-confirmed-Osteoporosis (FXNO: patients with fragility fractures but no osteopenia/osteoporosis diagnosis based on DEXA/formal documentation); Confirmed/fracture-osteoporosis (COP/FX: patients with fragility fractures and/or osteopenia/osteoporosis by DEXA/diagnosis); and the Normal cohort (Nm: patients with normal bone health and no fragility fractures). Cost analyses were performed using multivariate linear regression controlling for BMI, diabetes, baseline deformity (T1PA), and levels fused. Multivariate logistic regression assessed risk of reoperation/complications between groups while controlling for BMI, diabetes, baseline deformity (T1PA), and levels fused. Results.: Overall, 205 patients were included in the Fx-cohort, 136 patients in the COP-cohort, 115 patients in the FXNO-cohort, and 71 patients Nm-cohort. Compared with the Nm-cohort, osteoporotic-cohorts demonstrated significantly worse baseline spinopelvic alignment and higher comorbidity burden. Fx and FXNO cohorts had higher rates of PJF (Fx: 11.2% vs 1.4%, aOR 7.8; FXNO: 10.4% vs 1.4%, aOR 9.0) and revision surgery (Fx: 19.5% vs 7.0%, aOR 2.8; FXNO: 22.6% vs 7.0%, aOR 3.6). Osteoporotic cohorts demonstrated significantly higher short-term QALYs at 6 weeks ( P <0.05) with no difference in the long term. Revision surgery averaged $95,117 per case, translating into an estimated $4.0 million potential-cost-savings. Conclusion.: Our findings highlight the clinical and economic burden of untreated poor bone quality in the setting of ASD surgery. Proactive medical management is crucial to mitigate complications, reduce revisions, and significantly lower healthcare costs in ASD surgery.

Objective Lower limbs can play a major compensating role for sagittal malalignment; however, little is known about the different types of compensation. This study aimed to identify different patterns of lower limb compensation and to determine which parameters may affect the recruitment of knee flexion versus hip extension. Methods This study included adult spinal deformity (ASD) patients with full-body X-rays in erect position from a multicentric prospective database. All parameters were measured at baseline: demographics, clinical scores and radiographic parameters: pelvic parameters, pelvic incidence-lumbar lordosis (PI-LL) mismatch, T1 pelvic angle (TPA), sacro-femoral angle (SFA), knee flexion angle (KA), ankle dorsi-flexion angle (AA), pelvic shift (PSh), hip and knee osteoarthritis (OA) grade. A K-means cluster analysis was conducted to identify patterns of lower limb compensation based on SFA and KA. The optimal number of clusters was determined using the silhouette score. The different parameters were then compared across clusters. Results 871 ASD patients were included, of whom 66.9% were females. Mean age was 62.3±14.6 years, mean BMI was 27.7±5.5 kg.m^-2. Four patterns of lower limb compensations were identified: “No compensators”, “Recliners” (mainly hip extension), “Squatters” (mainly knee flexion) and “Mixed compensators” (both).“Mixed” and “Squatters” had significantly larger BMI. The proportion of females was the least in the “Squatters” cluster (47.0%) while it was the highest in the “Recliners” group (79.3%) (p<0.001). The proportion of patients with severe hip OA was the lowest in the “Recliners” (38.5%) while it was the highest in the “Squatters” group (71.9%). Knee OA rate was the highest in the“Squatters” group (72.7%). “Mixed compensators” had the greatest PI-LL mismatch (30.4±20.0°) and “No compensators” the lowest (5.3±21.3°). Pelvic incidence values were the highest in “Recliners” and “Mixed compensators” (59.2±13.1° and 57.0±14.1° respectively). TPA values were the highest in the “Mixed compensators” and the lowest in the “No compensators” (33.3±11.7° versus 16.1±11.5°). The “Squatters” presented the significantly poorest values for disability, frailty, and SRS score. Conclusions Cluster analysis determined four types of lower limb compensation:“Recliners” using only hip extension, “Squatters” using only knee flexion,“Mixed compensators” and “No compensators”. Lower limb compensatory mechanisms recruitment is multifactorial and varies with age, sex, BMI, frailty, knee and hip OA, pelvic incidence, and spinal alignment.

Study Design.: Retrospective cohort Objective.: The ISSG-AO Spinal Deformity Complication Classification System (SDCCS) predicts Diagnosis Related Group (DRG) coding and cost. Background.: Inconsistent definitions of complications contribute to variation in reported surgical complication rates. Incorrect complication reporting can lead to over or under DRG reimbursement. The ISSG-AO SDCCS provides improved complication reporting reproducibility and may help predict complication costs. Methods.: ASD patients were grouped into: DRG without complication or comorbidity (CC) or Major CC (MCC) (DRGs 455 & 458), with CC (DRGs 454 & 457), and with MCC (DRGs 453 & 456). Complications were graded by intervention severity per ISSG-AO system: grade 0 (none), 1 (mild-e.g., med change), 2 (moderate-e.g., ICU), 3 (severe-e.g., reoperation). Cost were based on Medicare inpatient prospective payment system (IPSS, Medicare Allowable rate). A multinomial logistic model identified key predictors of DRG assignment by complication grades. Results.: Of the 675 patients, 14% were in DRGs without CC/MCC, 71% in DRGs with CC, and 15% were DRGs with MCC. Patients with complications requiring intervention mostly fell into the higher DRG categories (97%). Patients who received an intervention are approximately 6.75 (2.01-22.75, P <.0021) times more likely to be classified under DRG with CC and 15.72 (95% CI, 4.23-58.45, P <.0001) times more likely to be classified with DRG with MCC compared to those who did not receive an intervention. Each unit increase in Edmonton Frailty Score raises the odds of being in DRG with MCC by 1.24 (95% CI 1.04-1.48, P 0.017). Similar trends were seen for OR time and LOS. Reimbursement showed incremental increase from $49.5K to $56K to $70K across DRG categories. Conclusions.: Patients with elevated ISSG-AO scores are more likely to be categorized into higher DRGs, experience extended lengths of stay and generate greater healthcare expenditures. The ISSG-AO SDCCS predicts DRG thereby helping standardize complication reporting.

Objective This study aimed to assess the ability of experienced spine surgeons to predict the occurrence of proximal junctional failure (PJF) within the first 2 years following ASD surgery, based on patient, surgical, and pre-discharge radiographic evaluation. Methods This case-based survey sent to spinal deformity surgeons included ASD patients who underwent correction-fusion surgery with a minimum follow-up of one year. Twenty patients who underwent posterior fusion and required PJF revision were identified. Another 20 patients with similar characteristics but without PJF served as a control group. Detailed patient vignettes included demographics, frailty assessment, medical history, DEXA, and Health-Related Quality of Life scores. Surgical details covered instrumentation, procedures, approach, graft use, osteotomies, cage incorporation, and PJF prophylaxis. Pre-operative and post-operative radiographs were provided. A panel of 21 experts in spine deformity surgery was then tasked to review these vignettes. The experts were instructed to offer qualitative predictions regarding the risk of failure, choosing from six possibilities ranging from “Extremely likely” to “Extremely unlikely.” Metrics for prediction quality (sensitivity, specificity, precision, accuracy) were analyzed. Furthermore, they were asked to provide insights into the factors influencing their predictions. Results The median follow-up for these cases was 2 years. The median time to failure was 5.5 months (Range: 2 to 20 months). Of 782 predictions, only 136 were extreme (i.e., either “Extremely likely” or “Extremely unlikely” categories); most responses were uncertain, with 42.8% expressing predictions of being somewhat likely or unlikely to fail. Overall, prediction accuracy varied between experts (37% to 65%), precision ranged from 40% to 69%, and sensitivity ranged from 35% to 100%. Aggregating consensus instead of individual answers, the prediction accuracy was 61%, precision 67%, and sensitivity 50%. Only four experts demonstrated accuracy above the consensus results, and one exhibited better precision. Factors influencing predictions included post-operative sagittal alignment for success and various patient factors (age, BMI, frailty, bone quality) for PJF. Conclusions Experienced spinal deformity surgeons have a poor ability to predict PJK and PJF. Expert predictions varied, with consensus achieving 61% accuracy. Factors influencing predictions included post-operative sagittal alignment for success and patient-related factors for PJF. The findings highlight the complexity of predicting PJF, emphasizing the need for improved risk assessment tools in ASD surgery planning.

Purpose A subset of adult spinal deformity (ASD) patients undergoing corrective surgery receive a disproportionate level of medical resources and incur greater costs. We examined the characteristics of such super-utilizers of health care resources among ASD patients. Methods This prospective, multicenter study analyzed data from ASD patients with > 4 levels of spinal fusion and a minimum 2-year follow-up. Index and total episode-of-care (EOC) costs in 2022 US dollars were calculated using average itemized direct costs obtained from administrative hospital records. Patients with total 2-year EOC cost > 90th percentile were considered super-utilizers, the characteristics of which we identified through a multivariate generalized logistic model. Results Of 1299 eligible patients, mean age was 60 years, 73% were female and 92% were Caucasian. Super-utilizers were older (+2.1 years; p = 0.012), had greater depression (34.2 vs 25.7%; p = 0.03), increased frailty (p = 0.009) comorbidities (p = 0.005), higher reoperation rates (54.4 vs 15.0%; p < 0.001), hospital length of stay (+ 3 days; p < 0.0001), higher surgical invasiveness (+28.6; p < 0.001), more vertebrae fused (+ 3; p < 0.0001); interbody fusions (80 vs 55%; p < 0.0001), bone morphogenetic protein (BMP) use (87.3 vs 69.4%; p = 0.0001), operative time (+91 min; p < 0.0001), and blood loss (+620 mL; p < 0.0001) compared to other ASD patients. Index cost was 65% (p < 0.0001), and cost/quality-adjusted life-year was three times higher among super-utilizers. Conclusion ASD patients with depression who undergo more complex or revision spinal surgical procedures are more likely to be super-utilizers. Identifying likely super-utilizers within the ASD population may enable targeted interventions and preoperative planning to reduce unnecessary costs, while improving patient outcomes.

Background: Patients with proximal junctional kyphosis (PJK) or failure (PJF) may demonstrate disparate outcomes and recovery when fused to the upper (UT) versus lower (LT) thoracic spine. Few studies have distinguished the reoperation and recovery abilities of patients with PJK or PJF when fused to the upper (UT) versus lower (LT) thoracic spine. Methods: Adult spine deformity patients ≥ 18 yrs with preoperative and 5-year (5Y) data fused to the sacrum/pelvis were included. The rates of PJK, PJK revision, and radiographic PJF were compared between patients with upper instrumented vertebra (UIV) in the upper thoracic spine (UT; T1-T7) and lower thoracic spine (LT; T8-L1). Mean differences were assessed via analyses of covariance, factoring in any differences between cohorts at baseline and any use of PJF prophylaxis. Backstep logistic regressions assessed predictors of achieving Smith et al.’s Best Clinical Outcomes (BCOs) and complications, controlling for similar covariates. Results: A total of 232 ASD patients were included (64.2 ± 10.2 years, 78% female); 36.3% were UT and 63.7% were LT. Postoperatively, the rates of PJK for UT were lower than LT at 1Y (34.6 vs. 50.4%, p = 0.024), 2Y (29.5 vs. 49.6% (p = 0.003), and 5Y (48.7 vs. 62.8%, p = 0.048), with comparable rates of PJF. In total, 4.0% of UT patients underwent subsequent reoperation, compared to 13.0% of LT patients (p = 0.025). A total of 6.0% of patients had recurrent PJK, and 3.9% had recurrent PJF (both p > 0.05). After reoperation, UT patients reported higher rates of improvement in the minimum clinically important difference for ODI by 2Y (p = 0.007) and last follow-up (p < 0.001). While adjusted regression revealed that, for UT patients, the minimization of construct extension was predictive of achieving BCOs by last follow-up (model p < 0.001), no such relationship was identified in LT patients. Conclusions: Patients initially fused to the lower thoracic spine demonstrate an increased incidence of PJK and lower rates of disability improvement, but are at a lessened risk of neurologic complications if reoperation is required.