Background: Our understanding of the relationship between sagittal alignment and mechanical complications is evolving. In normal spines, the L1-pelvic angle (L1PA) accounts for the magnitude and distribution of lordosis and is strongly associated with pelvic incidence (PI), and the T4-pelvic angle (T4PA) is within 4° of the L1PA. We aimed to examine the clinical implications of realignment to a normal L1PA and T4-L1PA mismatch. Methods: A prospective multicenter adult spinal deformity registry was queried for patients who underwent fixation from the T1-T5 region to the sacrum and had 2-year radiographic follow-up. Normal sagittal alignment was defined as previously described for normal spines: L1PA = PI × 0.5 − 21°, and T4-L1PA mismatch = 0°. Mechanical failure was defined as severe proximal junctional kyphosis (PJK), displaced rod fracture, or reoperation for junctional failure, pseudarthrosis, or rod fracture within 2 years. Multivariable nonlinear logistic regression was used to define target ranges for L1PA and T4-L1PA mismatch that minimized the risk of mechanical failure. The relationship between changes in T4PA and changes in global sagittal alignment according to the C2-pelvic angle (C2PA) was determined using linear regression. Lastly, multivariable regression was used to assess associations between initial postoperative C2PA and patient-reported outcomes at 1 year, adjusting for preoperative scores and age. Results: The median age of the 247 included patients was 64 years (interquartile range, 57 to 69 years), and 202 (82%) were female. Deviation from a normal L1PA or T4-L1PA mismatch in either direction was associated with a significantly higher risk of mechanical failure, independent of age. Risk was minimized with an L1PA of PI × 0.5 − (19° ± 2°) and T4-L1PA mismatch between −3° and +1°. Changes in T4PA and in C2PA at the time of final follow-up were strongly associated (r² = 0.96). Higher postoperative C2PA was independently associated with more disability, more pain, and worse self-image at 1 year. Conclusions: We defined sagittal alignment targets using L1PA (relative to PI) and the T4-L1PA mismatch, which are both directly modifiable during surgery. In patients undergoing long fusion to the sacrum, realignment based on these targets may lead to fewer mechanical failures. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Study Design.: A retrospective review of prospective multicenter database. Objective.: The aim of this study was to identify factors influencing readmission, reoperation, and the impact on health-related quality of life outcomes (HRQoLs) in adult spinal deformity (ASD) surgery. Summary of Background Data.: Many ASD patients experience complications requiring readmission. It is important to identify baseline/operative factors leading to rehospitalizations and reoperation, which may impact outcomes. Methods.: Inclusion criteria: ASD surgical patients (age >18 yrs, major coronal Cobb ≥20°, sagittal vertical axis ≥5 cm, pelvic tilt ≥25°, and/or thoracic kyphosis >60°) with complete baseline, 1-, and 2-year follow-up. Patients were grouped on the basis of readmission occurrence (yes/no) and type [medical (no reoperation) vs. surgical (revision surgery)]. Readmissions caused by infections requiring surgical treatment (e.g., deep infections) were considered reoperations. Univariate and multivariate analyses determined readmission and reoperation predictors. Repeated measures mixed models evaluated readmission impact on HRQoLs at 1 and 2 years. Results.: Three hundred thirty-four patients were included: 76 (22.8%) readmissions, involving 65 (85.5% of 76) reoperations (surgical readmission) and 11 (14.5% of 76) medical readmissions. The most common surgical readmission indication (n = 65) was implant complications (36.9%; rod breakage n = 13); the most common medical readmission indication was infection (36.4%, n = 4), treated with antibiotics. Noninfectious medical readmission (n = 7) included pleural effusion, deep vein thrombosis (DVT), intraoperative blood loss, neurologic, and unspecified. Readmission predictors: increased number of major peri-operative complications [odds ratio (OR) 5.13, P = 0.014], infection presence (OR 25.02, P = 0.001), implant complications (OR 6.12, P < 0.001), and radiographic complications (DJK, proximal junctional kyphosis, pseudoarthrosis, sagittal/coronal imbalance) (OR 16.94, P < 0.001). HRQoL analysis revealed overall improvement of the full cohort (P < 0.01), though the 76 readmitted improved less overall and at each time point P < 0.001) except in 6-week MCS (P = 0.14). Conclusion.: Major peri-operative, implant, radiographic, and infection complications during index were associated with increased readmission odds. Implant complications most frequently caused surgical readmissions. Readmitted patients improved in outcome scores, although less compared with the nonreadmitted cohort, yet displayed reduced 6-week SF-36 Mental Component Summary. Level of Evidence: 3

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: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.