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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., Competing Interests: Disclosure: The International Spine Study Group (ISSG) is funded through research grants from NuVasive, SI-Bone, DePuy Synthes Spine, K2M, Stryker, Biomet, AlloSource, and Orthofix, and individual donations. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/I191)., (Copyright © 2024 by The Journal of Bone and Joint Surgery, Incorporated.)

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., Competing Interests: Disclosure: Funding for this study was received from DePuy Synthes Spine, NuVasive, and K2/Stryker. In addition, the International Spine Study Group reports grants to the foundation from Medtronic, Globus, Stryker, SI Bone, and Carlsmed. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/H962)., (Copyright © 2024 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: Height gain following a surgical procedure for patients with adult spinal deformity (ASD) is incompletely understood, and it is unknown if height gain correlates with patient-reported outcome measures (PROMs)., Methods: This was a retrospective cohort study of patients undergoing ASD surgery. Patients with baseline, 6-week, and subanalysis of 1-year postoperative full-body radiographic and PROM data were examined. Correlation analysis examined relationships between vertical height differences and PROMs. Regression analysis was utilized to preoperatively estimate T1-S1 and S1-ankle height changes., Results: This study included 198 patients (mean age, 57 years; 69% female); 147 patients (74%) gained height. Patients with height loss, compared with those who gained height, experienced greater increases in thoracolumbar kyphosis (2.81° compared with -7.37°; p < 0.001) and thoracic kyphosis (12.96° compared with 4.42°; p = 0.003). For patients with height gain, sagittal and coronal alignment improved from baseline to postoperatively: 25° to 21° for pelvic tilt (PT), 14° to 3° for pelvic incidence - lumbar lordosis (PI-LL), and 60 mm to 17 mm for sagittal vertical axis (SVA) (all p < 0.001). The full-body mean height gain was 7.6 cm, distributed as follows: sella turcica-C2, 2.9 mm; C2-T1, 2.8 mm; T1-S1 (trunk gain), 3.8 cm; and S1-ankle (lower-extremity gain), 3.3 cm (p < 0.001). T1-S1 height gain correlated with the thoracic Cobb angle correction and the maximum Cobb angle correction (p = 0.002). S1-ankle height gain correlated with the corrections in PT, PI-LL, and SVA (p < 0.001). T1-ankle height gain correlated with the corrections in PT (p < 0.001) and SVA (p = 0.03). Trunk height gain correlated with improved Scoliosis Research Society (SRS-22r) Appearance scores (r = 0.20; p = 0.02). Patient-Reported Outcomes Measurement Information System (PROMIS) Depression scores correlated with S1-ankle height gain (r = -0.19; p = 0.03) and C2-T1 height gain (r = -0.18; p = 0.04). A 1° correction in a thoracic scoliosis Cobb angle corresponded to a 0.2-mm height gain, and a 1° correction in a thoracolumbar scoliosis Cobb angle resulted in a 0.25-mm height gain. A 1° improvement in PI-LL resulted in a 0.2-mm height gain., Conclusions: Most patients undergoing ASD surgery experienced height gain following deformity correction, with a mean full-body height gain of 7.6 cm. Height gain can be estimated preoperatively with predictive ratios, and height gain was correlated with improvements in reported SRS-22r appearance and PROMIS scores., Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article ( http://links.lww.com/JBJS/H620 )., (Copyright © 2023 The Authors. Published by The Journal of Bone and Joint Surgery, Incorporated. All rights reserved.)

Background: Hip osteoarthritis often coexists with adult spinal deformity, an abnormality in which sagittal spinopelvic malalignment is present. Debate exists whether to perform spinal realignment correction or total hip arthroplasty first. Hip extension and pelvic tilt are important compensatory mechanisms in the setting of sagittal spinopelvic malalignment and change after spinal realignment. We performed this study to evaluate the effect that the spinal realignment surgical procedure has on acetabular anteversion., Methods: This study is a retrospective review of a multicenter, prospective, consecutive database of patients with adult spinal deformity who underwent surgical spinal realignment. Only patients who already had undergone a total hip arthroplasty prior to the spinal realignment procedure were retained for analysis. Patients were excluded if they had insufficient imaging or large-head, metal-on-metal bearings or they had undergone revision total hip arthroplasty in the study period. Acetabular anteversion was calculated via the ellipse method on a standing, posterior-anterior, 90-cm radiograph with a well-centered pelvis. Anteversion was measured preoperatively and at six weeks or three months after the spinal realignment procedure. Spinopelvic parameters measured included pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, T1 pelvic angle, sagittal vertical axis, T1-spinopelvic inclination, and thoracic kyphosis., Results: Forty-one hips (thirty-three patients) were identified. Acetabular anteversion significantly reduced (p < 0.001) after spinal correction by mean change of -4.96° (range, -22.32° to +2.36°). The change in anteversion correlated with the changes in sagittal pelvic orientation (0.828 for the pelvic tilt, -0.757 for the sacral slope, and -0.691 for the lumbar lordosis) and global spinopelvic alignment (0.579 for the sagittal vertical axis and 0.585 for the T1 pelvic angle). Regression analysis revealed that anteversion decreased by 1° for each of the following spinopelvic parameter changes (p < 0.001): 1.105° for spinopelvic tilt, 1.032° for sacral slope, and 3.163° for lumbar lordosis., Conclusions: Patients with spinopelvic malalignment had a high prevalence of excessively anteverted acetabular components. Sagittal spinal correction following total hip arthroplasty resulted in reduced acetabular anteversion, which may have implications for stability. Changes in anteversion are most closely related to changes in pelvic tilt in an almost one-to-one ratio., (Copyright © 2015 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: Deep surgical site infection may change the course of growing-rod treatment of early-onset scoliosis. Our goal was to assess the effect of this complication on subsequent treatment., Methods: A multicenter international database was retrospectively reviewed; 379 patients treated with growing-rod surgery and followed for a minimum of two years were identified. Deep surgical site infection was defined as any infection requiring surgical intervention., Results: Forty-two patients (11.1%; twenty-five males and seventeen females) developed at least one deep surgical site infection. The mean age at the initial growing-rod surgery was 6.3 years (range, 0.6 to 13.2 years) and the mean duration of follow-up was 5.3 years (range, 2.2 to 14.3 years). The mean interval between the initial surgery and the first deep surgical site infection was 2.8 years (range, 0.02 to 7.9 years). Ten (2.6%) of the 379 patients developed deep surgical site infection before the first lengthening. Twenty-nine patients (7.7%) developed the infection during the course of the lengthening procedures, and three patients (0.8%) developed it after final fusion surgery. Thirty (13.6%) of 221 patients with stainless-steel implants had at least one deep surgical site infection compared with twelve (8%) of 150 patients with titanium implants (p < 0.05). (The remaining patients were treated with chromium-cobalt implants.) Twenty-two (52.4%) of the forty-two patients with deep surgical site infection underwent implant removal, which was complete in thirteen and partial in nine. Growing-rod treatment was terminated in two patients with partial removal and six patients with complete removal. An increased risk of deep surgical site infection was associated with stainless-steel implants (odds ratio [OR] = 5.7), non-ambulatory status (OR = 2.9), and the number of revisions before the development of deep surgical site infection (OR = 3.3). Neuromuscular etiology and non-ambulatory status increased the possibility of implant removal to treat infection (p < 0.05)., Conclusions: The prevalence of deep surgical site infection associated with growing-rod surgery is higher than that associated with standard pediatric spinal fusion (historical data). Non-ambulatory status, more revisions, and stainless-steel implants increased the risk of deep surgical site infection. After eight surgical procedures, the risk of deep surgical site infection increased to approximately 50%. When patients have implant removal, efforts should be made to retain one longitudinal implant to continue treatment., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence., (Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.)