Faculty Bibliography

BACKGROUND:Hip osteoarthritis (OA) is common in patients with adult spinal deformity (ASD). Limited data exist on the prevalence of hip OA in patients with ASD, or on its impact on baseline and postoperative alignment and patient-reported outcome measures (PROMs). Therefore, this paper will assess the prevalence and impact of hip OA on alignment and PROMs. METHODS:Patients with ASD who underwent L1-pelvis or longer fusions were included. Two independent reviewers graded hip OA with the Kellgren-Lawrence (KL) classification and stratified it by severity into non-severe (KL grade 1 or 2) and severe (KL grade 3 or 4). Radiographic parameters and PROMs were compared among 3 patient groups: Hip-Spine (hip KL grade 3 or 4 bilaterally), Unilateral (UL)-Hip (hip KL grade 3 or 4 unilaterally), or Spine (hip KL grade 1 or 2 bilaterally). RESULTS:Of 520 patients with ASD who met inclusion criteria for an OA prevalence analysis, 34% (177 of 520) had severe bilateral hip OA and unilateral or bilateral hip arthroplasty had been performed in 8.7% (45 of 520). A subset of 165 patients had all data components and were examined: 68 Hip-Spine, 32 UL-Hip, and 65 Spine. Hip-Spine patients were older (67.9 ± 9.5 years, versus 59.6 ± 10.1 years for Spine and 65.8 ± 7.5 years for UL-Hip; p < 0.001) and had a higher frailty index (4.3 ± 2.6, versus 2.7 ± 2.0 for UL-Hip and 2.9 ± 2.0 for Spine; p < 0.001). At 1 year, the groups had similar lumbar lordosis, yet the Hip-Spine patients had a worse sagittal vertebral axis (SVA) measurement (45.9 ± 45.5 mm, versus 25.1 ± 37.1 mm for UL-Hip and 19.0 ± 39.3 mm for Spine; p = 0.001). Hip-Spine patients also had worse Veterans RAND-12 Physical Component Summary scores at baseline (25.7 ± 9.3, versus 28.7 ± 9.8 for UL-Hip and 31.3 ± 10.5 for Spine; p = 0.005) and 1 year postoperatively (34.5 ± 11.4, versus 40.3 ± 10.4 for UL-Hip and 40.1 ± 10.9 for Spine; p = 0.006). CONCLUSIONS:This study of operatively treated ASD revealed that 1 in 3 patients had severe hip OA bilaterally. Such patients with severe bilateral hip OA had worse baseline SVA and PROMs that persisted 1 year following ASD surgery, despite correction of lordosis. LEVEL OF EVIDENCE/METHODS:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

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.

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.

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:Recombinant human bone morphogenetic protein 2 (rhBMP-2, or BMP for short) is a popular biological product used in spine surgeries to promote fusion and avoid the morbidity associated with iliac crest autograft. BMP's effect on pseudarthrosis in transforaminal lumbar interbody fusion (TLIF) remains unknown. OBJECTIVE:To assess the rates of pseudarthrosis in single-level TLIF with and without concurrent use of BMP. METHODS:analyses, and perioperative characteristics were analyzed by multiple logistic regression. RESULTS:= 0.002) increased the risk of reoperation for pseudarthrosis. CONCLUSIONS:BMP use did not reduce the rate of pseudarthrosis or the number of reoperations for pseudarthrosis in single-level TLIFs. Diabetes with end-organ damage was a significant risk factor for pseudarthrosis. CLINICAL RELEVANCE/CONCLUSIONS:BMP is frequently used "off-label" in transforaminal lumbar interbody fusion; however, little data exists to demonstrate its safety and efficacy in this procedure.

STUDY DESIGN/METHODS:Retrospective review of an adult deformity database. OBJECTIVE:To identify Pelvic Incidence (PI) and age-appropriate physical function alignment targets using a component angle of T1- Pelvic Angle (TPA) within the fusion to define correction and their relationship to proximal junctional kyphosis (PJK) and clinical outcomes. SUMMARY OF BACKGROUND DATA/BACKGROUND:In preoperative planning, a patient's PI is often utilized to determine alignment target. In a trend toward more patient specific planning, age-specific alignment has been shown to reduce the risk of mechanical failures. PI and age have not been analyzed with respect to defining a functional alignment. METHODS:A database of patients with operative adult spinal deformity (ASD) was analyzed. Patients fused to the pelvis and upper-instrumented vertebrae (UIV) above T11 were included. Alignment within the fusion correlated with clinical outcomes and PI. Short form 36-physical Component score (SF36-PCS) normative data and PI were used to compute functional alignment for each patient. Over-, under-, and functionally corrected groups were determined using T10-pelvic angle (T10PA). RESULTS:1052 patients met inclusion criteria. T10PA correlated with SF36-PCS and PI (R=0.601). At 6 weeks, 40.7% were functionally corrected, 39.4% were overcorrected, and 20.9% were under-corrected. The PJK incidence rate was 13.6%. Overcorrected patients had the highest PJK rate (18.1%) compared with functionally (11.3%) and under-corrected (9.5%) patients (P<0.05). Overcorrected patients had a trend toward more PJK revisions. All groups improved in HRQL; however, under-corrected patients had the worst 1-year SF36-PCS offset relative to normative patients of equivalent age (-8.1) vs. functional (-6.1) and overcorrected (-4.5), P<0.05. CONCLUSIONS:T10PA was used to determine functional alignment, an alignment based on PI and age-appropriate physical function. Correcting patients to functional alignment produced improvements in clinical outcomes, with the lowest rates of PJK. This patient specific approach to spinal alignment provides ASD correction targets that can be used intraoperatively.

STUDY DESIGN/METHODS:Retrospective review of prospectively collected data. OBJECTIVE:To analyze the impact of operative room (OR) time in adult spinal deformity (ASD) surgery on patient outcomes. BACKGROUND:It is currently unknown if OR time in ASD patients matched for deformity severity and surgical invasiveness is associated with patient outcomes. MATERIALS AND METHODS/METHODS:ASD patients with baseline and two-year postoperative radiographic and patient-reported outcome measures (PROM) data, undergoing a posterior-only approach for long fusion (>L1-Ilium) were included. Patients were grouped into short OR time (<40th percentile: <359 min) and long OR time (>60th percentile: >421 min). Groups were matched by age, baseline deformity severity, and surgical invasiveness. Demographics, radiographic, PROM data, fusion rate, and complications were compared between groups at baseline and two years follow-up. RESULTS:In total, 270 patients were included for analysis: the mean OR time was 286 minutes in the short OR group versus 510 minutes in the long OR group ( P <0.001). Age, gender, percent of revision cases, surgical invasiveness, pelvic incidence minus lumbar lordosis, sagittal vertical axis, and pelvic tilt were comparable between groups ( P >0.05). Short OR had a slightly lower body mass index than the short OR group ( P <0.001) and decompression was more prevalent in the long OR time ( P =0.042). Patients in the long group had greater hospital length of stay ( P =0.02); blood loss ( P <0.001); proportion requiring intensive care unit ( P =0.003); higher minor complication rate ( P =0.001); with no significant differences for major complications or revision procedures ( P >0.5). Both groups had comparable radiographic fusion rates ( P =0.152) and achieved improvement in sagittal alignment measures, Oswestry disability index, and Short Form-36 ( P <0.001). CONCLUSION/CONCLUSIONS:Shorter OR time for ASD correction is associated with a lower minor complication rate, a lower estimated blood loss, fewer intensive care unit admissions, and a shorter hospital length of stay without sacrificing alignment correction or PROMs. Maximizing operative efficiency by minimizing OR time in ASD surgery has the potential to benefit patients, surgeons, and hospital systems.

OBJECTIVE:The present study utilized recently developed in-construct measurements in simulations of cervical deformity surgery in order to assess undercorrection and predict distal junctional kyphosis (DJK). METHODS:A retrospective review of a database of operative cervical deformity patients was analyzed for severe DJK and mild DJK. C2-lower instrumented vertebra (LIV) sagittal angle (SA) was measured postoperatively, and the correction was simulated in the preoperative radiograph in order to match the C2-LIV by using the planning software. Linear regression analysis that used C2 pelvic angle (CPA) and pelvic tilt (PT) determined the simulated PT that matched the virtual CPA. Linear regression analysis was used to determine the C2-T1 SA, C2-T4 SA, and C2-T10 SA that corresponded to DJK of 20° and cervical sagittal vertical axis (cSVA) of 40 mm. RESULTS:Sixty-nine cervical deformity patients were included. Severe and mild DJK occurred in 11 (16%) and 22 (32%) patients, respectively; 3 (4%) required DJK revision. Simulated corrections demonstrated that severe and mild DJK patients had worse alignment compared to non-DJK patients in terms of cSVA (42.5 mm vs 33.0 mm vs 23.4 mm, p < 0.001) and C2-LIV SVA (68.9 mm vs 57.3 mm vs 36.8 mm, p < 0.001). Linear regression revealed the relationships between in-construct measures (C2-T1 SA, C2-T4 SA, and C2-T10 SA), cSVA, and change in DJK (all R > 0.57, p < 0.001). A cSVA of 40 mm corresponded to C2-T4 SA of 10.4° and C2-T10 SA of 28.0°. A DJK angle change of 10° corresponded to C2-T4 SA of 5.8° and C2-T10 SA of 20.1°. CONCLUSIONS:Simulated cervical deformity corrections demonstrated that severe DJK patients have insufficient corrections compared to patients without DJK. In-construct measures assess sagittal alignment within the fusion separate from DJK and subjacent compensation. They can be useful as intraoperative tools to gauge the adequacy of cervical deformity correction.