Faculty Bibliography

BACKGROUND CONTEXT/BACKGROUND:Severe sagittal plane deformity with loss of L4-S1 lordosis is disabling and can be improved through various surgical techniques. However, data is limited on the differing ability of anterior lumbar interbody fusion (ALIF), pedicle subtraction osteotomy (PSO), and transforaminal lumbar interbody fusion (TLIF) to achieve alignment goals in severely malaligned patients. PURPOSE/OBJECTIVE:To examine surgical techniques aimed at restoring L4-S1 lordosis in severe adult spinal deformity (ASD). DESIGN/METHODS:Retrospective review of prospectively collected data. PATIENT SAMPLE/METHODS:A total of 96 patients who underwent ALIF, PSO, and TLIF were included in this study. OUTCOME MEASURES/METHODS:The following data were observed for all cases: patient demographics, spinopelvic parameters, complications, and PROMs. METHODS:Severe ASD patients with preoperative PI-LL >20°, L4-S1 lordosis <30°, and full body radiographs and patient-reported outcome measures (PROMs) at baseline and six-week postoperative visit were included. Patients were grouped into ALIF (1-2 level ALIF at L4-S1), PSO (L4/L5 PSO), and TLIF (1-2 level TLIF at L4-S1). Comparative analyses were performed on demographics, radiographic spinopelvic parameters, complications, and PROMs. RESULTS:Among the 96 included patients, 40 underwent ALIF, 27 underwent PSO, and 29 underwent TLIF. At baseline, cohorts had comparable age, sex, race, Edmonton frailty scores and radiographic spinopelvic parameters (p>0.05). However, PSO was performed more often in revision cases (p<0.001). Following surgery, L4-S1 lordosis correction (p=0.001) was comparable among ALIF and PSO patients and caudal lordotic apex migration (p=0.044) was highest among ALIF patients. PSO patients had higher intraoperative estimated blood loss (p<0.001) and motor deficits (p=0.049), and in-hospital ICU admission (p=0.022) and blood products given (p=0.004) but were otherwise comparable in terms of length of stay, blood transfusion given, and postoperative admission to rehab. Likewise, 90-day postoperative complication profiles and six-week PROMs were comparable as well. CONCLUSIONS:ALIF can restore L4-S1 sagittal alignment as powerfully as PSO, with fewer intra-operative and in-hospital complications. When feasible, ALIF is a suitable alternative to PSO and likely superior to TLIF for correcting L4-S1 lordosis among patients with severe sagittal malalignment.

OBJECTIVE:Recent debate has arisen between whether to use a three-column osteotomy (3CO) or multilevel low-grade (MLG) techniques to treat severe sagittal malalignment in adult spinal deformity (ASD) surgery. The goal of this study was to compare the outcomes of 3CO and MLG techniques performed in corrective surgeries for ASD. METHODS:ASD patients who had a baseline PI-LL > 30° and 2-year follow-up data were included. Patients underwent either 3CO or MLG (thoracolumbar posterior column osteotomies at ≥ 3 levels or anterior lumbar interbody fusion at ≥ 3 levels with no 3CO). The segmental utility ratio was used to assess relative segmental correction (segmental correction divided by overall correction in lordosis divided by the number of thoracolumbar interventions [interbody fusion, thoracolumbar posterior column osteotomies, and 3CO]). The paired t-test was used to assess lordotic distribution by differences in lordosis between adjacent lumbar disc spaces (e.g., L1-2 to L2-3). Multivariate analysis, controlling for age, sex, BMI, osteoporosis, baseline pelvic incidence, and T1 pelvic angle, was used to evaluate the complication rates and radiographic and patient-reported outcomes between the groups. RESULTS:A total of 93 patients were included, 53% of whom underwent MLG and 47% of whom underwent 3CO. The MLG group had a lower BMI (p < 0.05). MLG patients received fewer previous fusions than 3CO patients (31% vs 80%, p < 0.001). MLG patients had 24% less blood loss but a 22% longer operative time (565 vs 419 minutes, p = 0.008). Using adjusted analysis, the 3CO group had greater segmental and relative correction at each level (segmental utility ratio mean 69% for 3CO vs 23% for MLG, p < 0.001). However, the 3CO group had lordotic differences between two adjacent lumbar disc pairs (range -0.5° to 9.0°, p = 0.009), while MLG was more harmonious (range 2.2°-6.5°, p > 0.4). MLG patients were more likely to undergo realignment to age-adjusted standards (OR 5.6, 95% CI 1.2-46.4; p = 0.033). MLG patients were less likely to develop neurological complications or undergo reoperation (OR 0.4, 95% CI 0.1-0.9; p = 0.041). Adjusted analysis revealed that MLG patients more often met a substantial clinical benefit in the Oswestry Disability Index score (OR 5.3, 95% CI 1.1-26.8; p = 0.043). CONCLUSIONS:MLG techniques showed better utility in lumbar distribution and age-adjusted global correction while minimizing neurological complications and reoperation rates by 2 years postoperatively. In selected instances, these techniques may offer the spine deformity surgeon a safer alternative when correcting severe adult spinal deformity.

OBJECTIVE:Sagittal alignment measured on standing radiography remains a fundamental component of surgical planning for adult spinal deformity (ASD). However, the relationship between classic sagittal alignment parameters and objective metrics, such as walking time (WT) and grip strength (GS), remains unknown. The objective of this work was to determine if ASD patients with worse baseline sagittal malalignment have worse objective physical metrics and if those metrics have a stronger relationship to patient-reported outcome metrics (PROMs) than standing alignment. METHODS:The authors conducted a retrospective review of a multicenter ASD cohort. ASD patients underwent baseline testing with the timed up-and-go 6-m walk test (seconds) and for GS (pounds). Baseline PROMs were surveyed, including Oswestry Disability Index (ODI), Patient-Reported Outcomes Measurement Information System (PROMIS), Scoliosis Research Society (SRS)-22r, and Veterans RAND 12 (VR-12) scores. Standard spinopelvic measurements were obtained (sagittal vertical axis [SVA], pelvic tilt [PT], and mismatch between pelvic incidence and lumbar lordosis [PI-LL], and SRS-Schwab ASD classification). Univariate and multivariable linear regression modeling was performed to interrogate associations between objective physical metrics, sagittal parameters, and PROMs. RESULTS:In total, 494 patients were included, with mean ± SD age 61 ± 14 years, and 68% were female. Average WT was 11.2 ± 6.1 seconds and average GS was 56.6 ± 24.9 lbs. With increasing PT, PI-LL, and SVA quartiles, WT significantly increased (p < 0.05). SRS-Schwab type N patients demonstrated a significantly longer average WT (12.5 ± 6.2 seconds), and type T patients had a significantly shorter WT time (7.9 ± 2.7 seconds, p = 0.03). With increasing PT quartiles, GS significantly decreased (p < 0.05). SRS-Schwab type T patients had a significantly higher average GS (68.8 ± 27.8 lbs), and type L patients had a significantly lower average GS (51.6 ± 20.4 lbs, p = 0.03). In the frailty-adjusted multivariable linear regression analyses, WT was more strongly associated with PROMs than sagittal parameters. GS was more strongly associated with ODI and PROMIS Physical Function scores. CONCLUSIONS:The authors observed that increasing baseline sagittal malalignment is associated with slower WT, and possibly weaker GS, in ASD patients. WT has a stronger relationship to PROMs than standing alignment parameters. Objective physical metrics likely offer added value to standard spinopelvic measurements in ASD evaluation and surgical planning.

OBJECTIVE:Complex spinal deformity surgeries may involve significant blood loss. The use of antifibrinolytic agents such as tranexamic acid (TXA) has been proven to reduce perioperative blood loss. However, for patients with a history of thromboembolic events, there is concern of increased risk when TXA is used during these surgeries. This study aimed to assess whether TXA use in patients undergoing complex spinal deformity correction surgeries increases the risk of thromboembolic complications based on preexisting thromboembolic risk factors. METHODS:Data were analyzed for adult patients who received TXA during surgical correction for spinal deformity at 21 North American centers between August 2018 and October 2022. Patients with preexisting thromboembolic events and other risk factors (history of deep venous thrombosis [DVT], pulmonary embolism [PE], myocardial infarction [MI], stroke, peripheral vascular disease, or cancer) were identified. Thromboembolic complication rates were assessed during the postoperative 90 days. Univariate and multivariate analyses were performed to assess thromboembolic outcomes in high-risk and low-risk patients who received intravenous TXA. RESULTS:Among 411 consecutive patients who underwent complex spinal deformity surgery and received TXA intraoperatively, 130 (31.6%) were considered high-risk patients. There was no significant difference in thromboembolic complications between patients with and those without preexisting thromboembolic risk factors in univariate analysis (high-risk group vs low-risk group: 8.5% vs 2.8%, p = 0.45). Specifically, there were no significant differences between groups regarding the 90-day postoperative rates of DVT (high-risk group vs low-risk group: 1.5% vs 1.4%, p = 0.98), PE (2.3% vs 1.8%, p = 0.71), acute MI (1.5% vs 0%, p = 0.19), or stroke (0.8% vs 1.1%, p > 0.99). On multivariate analysis, high-risk status was not a significant independent predictor for any of the thromboembolic complications. CONCLUSIONS:Administration of intravenous TXA during the correction procedure did not change rates of thromboembolic events, acute MI, or stroke in this cohort of adult spinal deformity surgery patients.

STUDY DESIGN/METHODS:Retrospective review of prospectively collected data. OBJECTIVE:To investigate the effect of lower extremity osteoarthritis on sagittal alignment and compensatory mechanisms in adult spinal deformity (ASD). BACKGROUND:Spine, hip, and knee pathologies often overlap in ASD patients. Limited data exists on how lower extremity osteoarthritis impacts sagittal alignment and compensatory mechanisms in ASD. METHODS:527 pre-operative ASD patients with full body radiographs were included. Patients were grouped by Kellgren-Lawrence grade of bilateral hips and knees and stratified by quartile of T1-Pelvic Angle (T1PA) severity into low-, mid-, high-, and severe-T1PA. Full body alignment and compensation were compared across quartiles. Regression analysis examined the incremental impact of hip and knee osteoarthritis severity on compensation. RESULTS:The mean T1PA for low-, mid-, high-, and severe-T1PA groups was 7.3°, 19.5°, 27.8°, 41.6°, respectively. Mid-T1PA patients with severe hip osteoarthritis had an increased sagittal vertical axis and global sagittal alignment (P<0.001). Increasing hip osteoarthritis severity resulted in decreased pelvic tilt (P=0.001) and sacrofemoral angle (P<0.001), but increased knee flexion (P=0.012). Regression analysis revealed with increasing T1PA, pelvic tilt correlated inversely with hip osteoarthritis and positively with knee osteoarthritis (r2=0.812). Hip osteoarthritis decreased compensation via sacrofemoral angle (β-coefficient=-0.206). Knee and hip osteoarthritis contributed to greater knee flexion (β-coefficients=0.215, 0.101; respectively). For pelvic shift, only hip osteoarthritis significantly contributed to the model (β-coefficient=0.100). CONCLUSIONS:For the same magnitude of spinal deformity, increased hip osteoarthritis severity was associated with worse truncal and full body alignment with posterior translation of the pelvis. Patients with severe hip and knee osteoarthritis exhibited decreased hip extension and pelvic tilt, but increased knee flexion. This examines sagittal alignment and compensation in ASD patients with hip and knee arthritis and may help delineate whether hip and knee flexion is due to spinal deformity compensation or lower extremity osteoarthritis.

BACKGROUND CONTEXT/BACKGROUND:Among adult spinal deformity (ASD) patients, heterogeneity in patient pathology, surgical expectations, baseline impairments, and frailty complicates comparisons in clinical outcomes and research. This study aims to qualitatively segment ASD patients using machine learning-based clustering on a large, multicenter, prospectively gathered ASD cohort. PURPOSE/OBJECTIVE:To qualitatively segment adult spinal deformity patients using machine learning-based clustering on a large, multicenter, prospectively gathered cohort. STUDY DESIGN/SETTING/METHODS:Machine learning algorithm using patients from a prospective multicenter study and a validation cohort from a retrospective single center, single surgeon cohort with complete 2-year follow up. PATIENT SAMPLE/METHODS:About 805 ASD patients; 563 patients from a prospective multicenter study and 242 from a single center to be used as a validation cohort. OUTCOME MEASURES/METHODS:To validate and extend the Ames-ISSG/ESSG classification using machine learning-based clustering analysis on a large, complex, multicenter, prospectively gathered ASD cohort. METHODS:We analyzed a training cohort of 563 ASD patients from a prospective multicenter study and a validation cohort of 242 ASD patients from a retrospective single center/surgeon cohort with complete two-year patient-reported outcomes (PROs) and clinical/radiographic follow-up. Using k-means clustering, a machine learning algorithm, we clustered patients based on baseline PROs, Edmonton frailty, age, surgical history, and overall health. Baseline differences in clusters identified using the training cohort were assessed using Chi-Squared and ANOVA with pairwise comparisons. To evaluate the classification system's ability to discern postoperative trajectories, a second machine learning algorithm assigned the single-center/surgeon patients to the same 4 clusters, and we compared the clusters' two-year PROs and clinical outcomes. RESULTS:K-means clustering revealed four distinct phenotypes from the multicenter training cohort based on age, frailty, and mental health: Old/Frail/Content (OFC, 27.7%), Old/Frail/Distressed (OFD, 33.2%), Old/Resilient/Content (ORC, 27.2%), and Young/Resilient/Content (YRC, 11.9%). OFC and OFD clusters had the highest frailty scores (OFC: 3.76, OFD: 4.72) and a higher proportion of patients with prior thoracolumbar fusion (OFC: 47.4%, OFD: 49.2%). ORC and YRC clusters exhibited lower frailty scores and fewest patients with prior thoracolumbar procedures (ORC: 2.10, 36.6%; YRC: 0.84, 19.4%). OFC had 69.9% of patients with global sagittal deformity and the highest T1PA (29.0), while YRC had 70.2% exhibiting coronal deformity, the highest mean coronal Cobb Angle (54.0), and the lowest T1PA (11.9). OFD and ORC had similar alignment phenotypes with intermediate values for Coronal Cobb Angle (OFD: 33.7; ORC: 40.0) and T1PA (OFD: 24.9; ORC: 24.6) between OFC (worst sagittal alignment) and YRC (worst coronal alignment). In the single surgeon validation cohort, the OFC cluster experienced the greatest increase in SRS Function scores (1.34 points, 95%CI 1.01-1.67) compared to OFD (0.5 points, 95%CI 0.245-0.755), ORC (0.7 points, 95%CI 0.415-0.985), and YRC (0.24 points, 95%CI -0.024-0.504) clusters. OFD cluster patients improved the least over 2 years. Multivariable Cox regression analysis demonstrated that the OFD cohort had significantly worse reoperation outcomes compared to other clusters (HR: 3.303, 95%CI: 1.085-8.390). CONCLUSION/CONCLUSIONS:Machine-learning clustering found four different ASD patient qualitative phenotypes, defined by their age, frailty, physical functioning, and mental health upon presentation, which primarily determines their ability to improve their PROs following surgery. This reaffirms that these qualitative measures must be assessed in addition to the radiographic variables when counseling ASD patients regarding their expected surgical outcomes.

BACKGROUND:The association of Hounsfield units (HU) and junctional pathologies in adult cervical deformity (ACD) surgery has not been elucidated. OBJECTIVE:Assess if the bone mineral density of the LIV, as assessed by HUs, is prognostic for the risk of complications after ACD surgery. STUDY DESIGN/SETTING/METHODS:Retrospective cohort study. METHODS:HUs were measured on preoperative CT scans. Means comparison test assessed differences in HUs based on the occurrence of complications, linear regression assessed the correlation of HUs with risk factors, and multivariable logistic regression followed by a conditional inference tree derived a threshold for HUs based on the increased likelihood of developing a complication. RESULTS:In all, 107 ACD patients were included. Thirty-one patients (29.0%) developed a complication (18.7% perioperative), with 20.6% developing DJK and 11.2% developing DJF. There was a significant correlation between lower LIVs and lower HUs (r=0.351, P=0.01), as well as age and HUs at the LIV. Age did not correlate with change in the DJK angle (P>0.2). HUs were lower at the LIV for patients who developed a complication and an LIV threshold of 190 HUs was predictive of complications (OR: 4.2, [1.2-7.6]; P=0.009). CONCLUSIONS:Low bone mineral density at the lowest instrumented vertebra, as assessed by a threshold lower than 190 Hounsfield units, may be a crucial risk factor for the development of complications after cervical deformity surgery. Preoperative CT scans should be routinely considered in at-risk patients to mitigate this modifiable risk factor during surgical planning. LEVEL OF EVIDENCE/METHODS:Level-III.

BACKGROUND AND OBJECTIVES/OBJECTIVE:For patients with surgical adult spinal deformity (ASD), our understanding of alignment has evolved, especially in the last 20 years. Determination of optimal restoration of alignment and spinal shape has been increasingly studied, yet the assessment of how these alignment schematics have incrementally added benefit to outcomes remains to be evaluated. METHODS:Patients with ASD with baseline and 2-year were included, classified by 4 alignment measures: Scoliosis Research Society (SRS)-Schwab, Age-Adjusted, Roussouly, and Global Alignment and Proportion (GAP). The incremental benefits of alignment schemas were assessed in chronological order as our understanding of optimal alignment progressed. Alignment was considered improved from baseline based on SRS-Schwab 0 or decrease in severity, Age-Adjusted ideal match, Roussouly current (based on sacral slope) matching theoretical (pelvic incidence-based), and decrease in proportion. Patients separated into 4 first improving in SRS-Schwab at 2-year, second Schwab improvement and matching Age-Adjusted, third two prior with Roussouly, and fourth improvement in all four. Comparison was accomplished with means comparison tests and χ2 analyses. RESULTS:Sevenhundredthirty-two. patients met inclusion. SRS-Schwab BL: pelvic incidence-lumbar lordosis mismatch (++:32.9%), sagittal vertical axis (++: 23%), pelvic tilt (++:24.6%). 640 (87.4%) met criteria for first, 517 (70.6%) second, 176 (24%) third, and 55 (7.5%) fourth. The addition of Roussouly (third) resulted in lower rates of mechanical complications and proximal junctional kyphosis (48.3%) and higher rates of meeting minimal clinically important difference (MCID) for physical component summary and SRS-Mental (P < .05) compared with the second. Fourth compared with the third had higher rates of MCID for ODI (44.2% vs third: 28.3%, P = .011) and SRS-Appearance (70.6% vs 44.8%, P < .001). Mechanical complications and proximal junctional kyphosis were lower with the addition of Roussouly (P = .024), while the addition of GAP had higher rates of meeting MCID for SRS-22 Appearance (P = .002) and Oswestry Disability Index (P = .085). CONCLUSION/CONCLUSIONS:Our evaluation of the incremental benefit that alignment schemas have provided in ASD corrective surgery suggests that the addition of Roussouly provided the greatest reduction in mechanical complications, while the incorporation of GAP provided the most significant improvement in patient-reported outcomes.

OBJECTIVE:To assess the financial impact of Enhanced Recovery After Surgery (ERAS) protocols and cost-effectiveness in cervical deformity corrective surgery. STUDY DESIGN/METHODS:Retrospective review of prospective CD database. BACKGROUND:Enhanced Recovery After Surgery (ERAS) can help accelerate patient recovery and assist hospitals in maximizing the incentives of bundled payment models while maintaining high-quality patient care. However, the economic benefit of ERAS protocols, nor the heterogeneous components that make up such protocols, has not been established. METHODS:Operative CD patients ≥18 y with complete pre-(BL) and up to 2-year(2Y) postop radiographic/HRQL data were stratified by enrollment in Standard-of-Care ERAS beginning in 2020. Differences in demographics, clinical outcomes, radiographic alignment targets, perioperative factors, and complication rates were assessed through means comparison analysis. Costs were calculated using PearlDiver database estimates from Medicare pay scales. QALY was calculated using NDI mapped to SF6D using validated methodology with a 3% discount rate to account for a residual decline in life expectancy. RESULTS:In all, 127 patients were included (59.07±11.16 y, 54% female, 29.08±6.43 kg/m 2 ) in the analysis. Of these patients, 54 (20.0%) received the ERAS protocol. Per cost analysis, ERAS+ patients reported a lower mean total 2Y cost of 35049 USD compared with ERAS- patients at 37553 ( P <0.001). Furthermore, ERAS+ patients demonstrated lower cost of reoperation by 2Y ( P <0.001). Controlling for age, surgical invasiveness, and deformity per BL TS-CL, ERAS+ patients below 70 years old were significantly more likely to achieve a cost-effective outcome by 2Y compared with their ERAS- counterparts (OR: 1.011 [1.001-1.999, P =0.048]. CONCLUSIONS:Patients undergoing ERAS protocols experience improved cost-effectiveness and reduced total cost by 2Y post-operatively. Due to the potential economic benefit of ERAS for patients incorporation of ERAS into practice for eligible patients should be considered.