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PURPOSE: We defined sagittal S-line tilt (SSLT) as the tilt of the line connecting the upper instrumented vertebra and the lower instrumented vertebra. This study aimed to: (1) examine the correlation between SSLT and proximal junctional angle (PJA) change values, and (2) determine the cut-off value of SSLT with respect to proximal junctional kyphosis (PJK) occurrence. METHODS: Eighty-six consecutive patients (81 female and 5 male; mean age: 15.8 years) with Lenke 5C AIS who underwent posterior selective spinal fusion. Pearson's correlation coefficients were used to examine the relationship between preoperative SSLT and changes in PJA from preoperative to 2 years postoperative. The impact of SSLT on PJK at 2 years after surgery was assessed using a receiver operating characteristic (ROC) curve. RESULTS: We observed a moderate positive correlation between preoperative SSLT and change in PJA (R = 0.541, P < 0.001). We identified 18 patients (21%) with PJK at 2 years postoperative. Mean preoperative SSLT in the PJK group and the non-PJK group differed significantly at 23.3 ± 4.1° and 16.1 ± 5.0°, respectively (P < 0.001). The cut-off value of preoperative SSLT for PJK at 2 years postoperative was 18° in ROC curve analysis, with a sensitivity of 94%, specificity of 68%, and area under the ROC curve of 0.868. CONCLUSION: In selective lumbar fusion for AIS Lenke type 5C curves, preoperative SSLT was significantly correlated with PJA change from preoperative to 2 years postoperative. SSLT was a predictor of PJK occurrence, with a cut-off value of 18°.

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PURPOSE: Determine the effect of using the modified S-line vertebra (MSLV) as the upper instrumented vertebra (UIV) on postoperative trunk balance, L4 tilt, and clinical outcomes in selective thoracic fusion (STF) for adolescent idiopathic scoliosis (AIS) Lenke type 1C curve. METHODS: Twenty-eight consecutive patients (all female; mean age: 15.4±2.0 years) with AIS Lenke type 1C curve were retrospectively enrolled. Primary outcome measures were coronal balance (absolute distance between C7 and the center of the sacral vertical line), L4 tilt, and Scoliosis Research Society (SRS)-22r scores at 2 years postoperatively. The group with the MSLV at the UIV was designated as the MSLV group (18 patients), and the group with the MSLV proximal (12 patients) or distal (4 patients) to the UIV was defined as the non-MSLV group. RESULTS: We observed no significant differences between the groups regarding age, LIV and stable vertebra positioning, or preoperative X-ray parameters. Postoperative coronal balance was significantly better in the MSLV group (0.39±0.08 vs. 1.34±0.22 cm; P.

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BACKGROUND: We sought to determine which aspect of the upper instrumented vertebrae (UIV)-tilt angle or screw angle-was more strongly associated with: (1) proximal junctional kyphosis/failure (PJK/F), (2) other mechanical complications and reoperations, and (3) patient-reported outcome measures (PROMs). METHODS: A single-institution, retrospective cohort study was undertaken for patients undergoing adult spinal deformity (ASD) surgery from 2011 to 2017. Only patients with UIV at T7 or below were included. The primary exposure variables were UIV tilt angle (the angle of the UIV inferior endplate and the horizontal) and UIV screw angle (the angle of the UIV screws and superior endplate). Multivariable logistic regression included age, body mass index, osteopenia/osteoporosis, postoperative sagittal vertical axis, postoperative pelvic-incidence lumbar lordosis mismatch, UIV tilt angle, and UIV screw angle. RESULTS: One hundred and seventeen patients underwent adult spinal deformity surgery with a minimum of 2-year follow-up. A total of 41 patients (35.0%) had PJK and 26 (22.2%) had PJF. (1) UIV tilt angle: 96 (82.1%) had lordotic UIV tilt angles, 6 (5.1%) were neutral, and 15 (12.8%) were kyphotic. (2) UIV screw angle: 38 (32.5%) had cranially directed screws, 4 (3.4%) were neutral, and 75 (64.1%) were caudally directed. Both lordotic-angled UIV endplate (OR = 1.06, 95% CI = 1.01-1.12, and P = 0.020) and cranially directed screws (OR = 1.19, 95% CI = 1.07-1.33, and P < 0.001) were associated with higher odds of PJK, with a more pronounced effect of UIV screw angle compared with UIV tilt angle (Wald test, 9.40 vs 4.42). Similar results were found for PJF. Neither parameter was associated with other mechanical complications, reoperations, or patient-reported outcome measures. CONCLUSIONS: UIV screw angle was more strongly associated with development of PJK/F compared with tilt angle. Overall, these modifiable parameters are directly under the surgeon's control and can mitigate the development of PJK/F. CLINICAL RELEVANCE: Surgeons may consider selecting a UIV with a neutral or kyphotically directed UIV tilt angle when performing ASD surgery with a UIV in the lower thoracic or lumbar region, as well as use UIV screw angles that are caudally directed, for the purprose of decreasing the risk of developing PJK/F.

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The imbalance of the lateral shoulder is reflected by the clavicle angle (CA) in radiology. It remains unclear how to achieve postoperative lateral shoulder balance (LSB) after spinal deformity correction surgery. A retrospective analysis was conducted on AIS patients who underwent surgery by the same spine surgeon at our hospital from 2016 to 2020. A total of 110 patients with spinal deformity were included in the study to verify the correlation between the T1-T5 tilt angle and CA before and after surgery, as well as the relation-ship between the change in T1-T5 tilt angle before and after surgery and the change in CA before and after surgery. By comparing the correlation coefficients, it was found that there may not be a direct relationship between the pre- and postoperative tilt angles of T1-5 and CA, but their changes were closely related to the changes in CA. The change in T1 tilt angle after orthopaedic surgery was significantly correlated with the change in CA, with a correlation coefficient of 0.976, indicating a close relationship between T1 and the clavicle. As the vertebrae moved down, the correlation gradually decreased. In summary, this study suggests that there is a close relationship between T1-T5 and the clavicle and that the change in T1 tilt angle after spinal scoliosis correction surgery is significantly correlated with CA, which decreases as the vertebra moves down.

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OBJECTIVE: The aim of this study was to investigate the impact of upper instrumented vertebra (UIV) screw angles on proximal junctional complications in patients with de novo degenerative lumbar scoliosis (DNDLS). METHODS: A total of 120 patients with DNDLS who underwent posterior long-segment instrumentation and fusion were included. Patients were divided into a proximal junctional kyphosis/failure (PJK/PJF) group and a non-PJK/PJF group. Radiographic parameters were measured, including UIV screw angle, UIV slope, UIV screw slope, fixed segmental angle (FSA), and spinopelvic parameters. Clinical and radiographic data were compared between the two groups. Multivariate logistic regression was used to analyze the independent risk factors of PJK/PJF. Receiver operating characteristic (ROC) curve analysis was used to determine the threshold value to predict PJK/PJF. RESULTS: Thirty-six patients (30.0%) developed PJK or PJF during follow-up. Patients in the PJK/PJF group had a larger postoperative UIV screw angle, a larger postoperative UIV screw slope, and a larger postoperative PJA. A significant increase was observed in UIV screw angle from immediately postoperative assessment to the final follow-up in two groups (p < 0.001). Multivariate logistic analysis indicated that a larger positive postoperative UIV screw angle was an independent risk factor for PJK/PJF (OR 1.546, 95% CI 1.274-1.877). ROC curve analysis indicated that a UIV screw angle ≥ 1° is more likely to develop PJK/PJF. Compared with group A patients (UIV screw angle < 1°), group B patients (UIV screw angle ≥ 1°) had a higher incidence of PJK, PJF, UIV screw loosening, and worse functional scores at the final follow-up. CONCLUSIONS: Avoiding insertion of cranially directed UIV pedicle screws may help prevent the development of PJK and PJF in patients with DNDLS.

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PURPOSE OF REVIEW: Posterior spinal fusion (PSF) is the preferred treatment for adolescent idiopathic scoliosis (AIS) patients with surgical range curves. Selection of the proper upper and lower instrumented vertebrae (UIV and LIV) is essential in curve correction and achieving a successful outcome, while preventing short and long-term complications. RECENT FINDINGS: The literature lacks high-level evidence, especially on outcomes of modern surgical techniques. However, evidence seems to show that a great majority of AIS patients have excellent clinical and functional long-term outcomes after PSF. We have reviewed the evidence and provided our level selection recommendations, which should be weighed against the body of evidence on the topic when selecting fusion levels in AIS.

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OBJECTIVE: Selecting C2 versus C3 or C4 (i.e., C3/C4) as the rostral anchoring level in long-segment cervical fusions is a common clinical conundrum. The data regarding proximal failure in long constructs of the cervical spine is scarce. The objective of this study was to systematically review the published literature and perform a meta-analysis of the incidence for proximal adjacent-segment disease (ASD) in the context of long cervical fusions and cervicothoracic fusions ending in C2 versus those ending in the subaxial spine (C3 or C4). METHODS: Using the PRISMA guidelines, the authors performed a search of the PubMed/MEDLINE, Embase/Ovid, and Cochrane Central databases to identify all full-text articles in the English-language literature with the following inclusion criteria: 1) studies including patients with the upper instrumented vertebra (UIV) at C2 versus C3/C4; 2) patients undergoing ≥ 3-level posterior cervical fusion; and 3) indication for surgery of degenerative disc disease, cervical spondylotic myelopathy, or cervical deformity. Studies that were not published in the English language, case reports, review articles, letters to the editor, and meeting abstracts were excluded. A meta-analysis was conducted using a fixed-effects model when I2 values were below 70%. Conversely, when I2 values were equal to or greater than 70%, a random-effects model was used. A funnel plot was used to assess the presence of publication bias. RESULTS: Seven studies consisting of 1215 patients were included in the meta-analysis. There were 403 (32.8%) patients in the C2 UIV group and 812 (67.2%) patients in the C3/C4 UIV group. When the 7 studies were analyzed, the overall rate of reoperation was comparable between the C2 (9.2%) and C3/C4 (9.4%) UIV groups (p = 0.93) but the rate of surgical ASD due to proximal pathology was 1.2% and 3%, respectively (OR 0.36, 95% CI 0.15-0.86; p = 0.02). When comparing between groups, no statistical difference was found regarding the rate of reoperation due to distal pathology or surgical infection. CONCLUSIONS: Long-segment cervical or cervicothoracic constructs that anchor into C2 may have similar complication rates but lower revision rates for proximal ASD than constructs that anchor into the subaxial spine.

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BACKGROUND: Selection of the upper instrumented vertebra (UIV) is crucial for surgical treatment of degenerative lumbar scoliosis (DLS), given the relevance of UIV in postoperative proximal adjacent segment degeneration (pASD). Our previous research found that selection of UIV not lower than (≤) the first coronal reverse vertebra (FCRV), which marks the turning point of Hounsfield unit (HU) asymmetry, could significantly reduce pASD. However, the degree of HU asymmetry can vary among patients, suggesting a demand for more individualized UIV selection criteria, which we aimed to develop using quantitative HU measurement in the current study. METHODS: We included 153 consecutive patients with DLS. Quantitative measurement of HU of both sides of the vertebrae of these patients was performed on three planes of CT reconstruction for average values and determination of FCRV. Pre- and postoperative X-ray plain films were examined for radiological measurements and determination of pASD. Further, 35 patients with lumbar disc herniation and without significant scoliosis were also included as the reference group, and their bilateral HU was measured. RESULTS: In all 153 patients, those with UIV ≤ FCRV had a significantly lower rate of pASD (9.4% vs. 24.6%, P = 0.011). The difference between HU of the left and right sides of the FCRV (dF) could range from close to 0-59.4. The difference between HU of the left and right sides of the vertebrae in the reference group had an average value of 5.21. In 101 dF ≥ 5 DLS patients, those with UIV ≤ FCRV had a significantly lower rate of pASD (7.6% vs. 28.6%, P = 0.005), while this rate was insignificant in the other 52 dF < 5 patients (13.3% vs. 18.2%, P = 0.708). No other general, radiological, or operative parameter was found to have significant influence on the occurrence of pASD. CONCLUSIONS: Selection of UIV ≤ FCRV can significantly reduce the risk of pASD for patients with DLS with dF ≥ 5. Trial Registration Not applicable, since this is an observational study.

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Adult Spinal Deformity (ASD) is a complex pathologic condition with significant impact on quality of life, including pain, loss of function, and fatigue. Achieving realignment goals is crucial for long-term results. Reliable preoperative planning strategies, including nomograms, measurement tools, and level selection, are key to maximizing the likelihood of achieving a good outcome following ASD corrective surgery. This review covers recent literature on such strategies, including review of the different targets for realignment and their association with outcomes (both patients-reported outcomes and complications), selection of upper and lower instrumented vertebrae, and the latest innovation in preoperative planning for deformity surgery.

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Proximal junctional kyphosis (PJK) is a major mechanical complication after adult spinal deformity (ASD) surgery, and is multifactorial. Osteopenia and sarcopenia are patient risk factors, but it has not yet been well-documented which of them is the more significant risk factor. We retrospectively studied patients older than 50 years who underwent ASD surgery from the lower thoracic spine to the pelvis. In addition to patient demographic data and pre- and post-operative radiographic sagittal parameters (PI: pelvic incidence; LL: lumbar lordosis; SVA: sagittal vertical axis; PT: pelvic tilt), Hounsfield unit (HU) values on preoperative computed tomography and cross sectional area (CSA) and fatty infiltration ratio (FI%) of the paraspinal musculature (PSM) on preoperative magnetic resonance image were measured from the upper-instrumented vertebra (UIV) to UIV + 2 and averaged. PJK was observed in 11 of 29 patients. There was no statistical difference between the patients with and without PJK in age at surgery, sex, body mass index, bone mineral density, preoperative PI-LL, SVA, PT, postoperative PI-LL, SVA, PT, HU, and CSA. FI% in patients with PJK (25.0) was significantly higher than that (15.3) in patients without PJK (P = 0.001). Logistic regression analysis identified FI% of PSM as a significant independent factor of PJK (odds ratio, 1.973; 95% confidence interval, 1.290-5.554; P < 0.0001). After successful elimination of possible factors related to PJK other than sarcopenia and osteopenia, sarcopenia assessed by fatty degeneration of the PSM at the UIV was shown to be a more important factor than osteopenia for PJK after long fusion for ASD.

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Background and Objectives: In this retrospective cohort study, we investigate associations between the Hounsfield units (HU) value of upper instrumented vertebra (UIV) and proximal junctional kyphosis (PJK) after adult spinal deformity (ASD) surgery. Materials and Methods: The cohort consisted of 60 patients (mean age 71.7 years) who underwent long instrumented fusion surgery (≥6 vertebrae) for ASD with at least 1 year of follow-up. The preoperative bone mineral density (BMD) measured on DXA scans, the HU values at UIV and UIV+1, and the radiographic parameters were compared between the PJK and non-PJK groups. The severity of UIV fracture was assessed using a semiquantitative (SQ) grade. Results: PJK occurred in 43% of patients. No significant differences in patient age, sex, BMD, and preoperative radiographic parameters were observed between the PJK and non-PJK groups. The HU values of the UIV (103.4 vs. 149.0, p < 0.001) and UIV+1 (102.0 vs. 145.7, p < 0.001) were significantly lower in the PJK group. The cutoff values of HU at UIV and UIV+1 were 122.8 and 114.9, respectively. Lower HU values at UIV (Grade 1: 134.2, Grade 2: 109.6, Grade 3: 81.1, p < 0.001) and UIV+1 (Grade 1: 131.5, Grade 2: 107.1, Grade 3: 82.1, p < 0.001) were associated with severe SQ grade. Conclusions: Lower HU values at UIV and UIV+1 had a negative impact on signal incidence of PJK and were correlated with the severity of UIV fractures. Preoperative treatment of osteoporosis seems necessary for preoperative UIV HU values less than 120.

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PURPOSE: Prior research has demonstrated the influence of preoperative shoulder elevation (SE), proximal thoracic curve magnitude, and upper instrumented vertebra (UIV) on shoulder balance after PSF for AIS. Our purpose was to evaluate the impact of these factors on shoulder balance in early onset idiopathic scoliosis (EOIS) patients treated with growth-friendly instrumentation. METHODS: This was a multicenter retrospective review. Children with EOIS treated with dual TGR, MCGR, or VEPTR and minimum 2-year follow-up were identified. Demographics and radiographic/surgical data were collected. RESULTS: 145 patients met inclusion criteria: 74 had right SE (RSE), 49 left SE (LSE), and 22 even shoulders (EVEN) preoperatively. Mean follow-up was 5.3 years (range, 2.0-13.1 years). The LSE group had a larger pre-index mean main thoracic curve (p = 0.021) but no difference was observed between groups at the post-index or most recent timepoints. RSE patients with UIV of T2 were more likely to have balanced shoulders post-index than patients with UIV of T3 or T4 (p = 0.011). Pre-index radiographic shoulder height (RSH) was predictive of post-index shoulder imbalance ≥ 2 cm in the LSE group (p = 0.007). A ROC curve showed a cut-off of 1.0 cm for RSH. 0/16 LSE patients with pre-index RSH < 1.0 cm had post-index shoulder imbalance ≥ 2 cm compared to 8/28 (29%) patients with pre-index RSH > 1.0 cm (p = 0.006). CONCLUSION: Preoperative LSE > 1.0 cm is predictive of shoulder imbalance ≥ 2 cm after insertion of TGR, MCGR, or VEPTR in children with EOIS. In patients with preoperative RSE, UIV of T2 resulted in a higher likelihood of balanced shoulders postoperatively.

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Lateral shoulder imbalance (LSI) is reflected radiologically by the clavicle angle (CA). How to achieve postoperative lateral shoulder balance (LSB) after scoliosis correction surgery remains unclear. In the current study, by using the preoperative upper instrumented vertebra (UIV) tilt, the CA, the flexibility between T1 and the UIV, and the ideal postoperative UIV tilt was predicted based on the following formula: ideal postoperative UIV tilt = preoperative UIV tilt-the flexibility between T1 and UIV-preoperative CA. The reliability of the formula was verified through a retrospective analysis, and 76 scoliosis patients were enrolled. The feasibility of this method was verified through a prospective analysis, and 13 scoliosis patients were enrolled. In the retrospective study, there was a significant correlation between the difference in the actual and ideal postoperative UIV tilt values and the postoperative CA, with correlation coefficients in the whole, LSI, and LSB groups of 0.981, 0.982, and 0.953, respectively (p < 0.001). In the prospective study, all patients achieved satisfactory LSB. Using the formula preoperatively to predict an ideal postoperative UIV tilt and controlling the intraoperative UIV tilt with the improved crossbar technique may be an effective digital method for achieving postoperative LSB and has important clinical significance.

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BACKGROUND: This study represents the first finite element (FE) analysis of long-instrumented spinal fusion from the thoracic vertebrae to the pelvis in the context of adult spinal deformity (ASD) with osteoporosis. We aimed to evaluate the von Mises stress in long spinal instrumentation for models that differ in terms of spinal balance, fusion length, and implant type. METHODS: In this three-dimensional FE analysis, FE models were developed based on computed tomography images from a patient with osteoporosis. The von Mises stress was compared for three different sagittal vertical axes (SVAs) (0, 50, and 100 mm), two different fusion lengths (from the pelvis to the second [T2-S2AI] or 10th thoracic vertebra [T10-S2AI]), and two different types of implants (pedicle screw or transverse hook) in the upper instrumented vertebra (UIV). We created 12 models based on combinations of these conditions. RESULTS: The overall von Mises stress was 3.1 times higher on the vertebrae and 3.9 times higher on implants for the 50-mm SVA models than that for the 0-mm SVA models. Similarly, the values were 5.0 times higher on the vertebrae and 6.9 times higher on implants for the 100-mm SVA models than that for the 0-mm SVA models. Higher SVA was associated with greater stress below the fourth lumbar vertebrae and implants. In the T2-S2AI models, the peaks of vertebral stress were observed at the UIV, at the apex of kyphosis, and below the lower lumbar spine. In the T10-S2AI models, the peaks of stress were observed at the UIV and below the lower lumbar region. The von Mises stress in the UIV was also higher for the screw models than for the hook models. CONCLUSION: Higher SVA is associated with greater von Mises stress on the vertebrae and implants. The stress on the UIV is greater for the T10-S2AI models than for the T2-S2AI models. Using transverse hooks instead of screws at the UIV may reduce stress in patients with osteoporosis.

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PURPOSE: This study sought to investigate associations between upper instrumented vertebra (UIV) location and the risk of proximal junctional kyphosis (PJK) at 2 years following posterior spinal fusion (PSF) for Scheuermann's kyphosis (SK). METHODS: In this retrospective cohort study, SK patients who underwent PSF and reached 2 years postop were identified in a multicenter international registry, excluding those with anterior release, prior spine surgery, neuromuscular comorbidity, post-traumatic kyphosis, or kyphosis apex below T11-T12. Location of UIV as well as the number of levels between UIV and preoperative kyphosis apex was determined. Additionally, the degree of kyphosis correction was evaluated. PJK was defined as a proximal junctional angle ≥ 10° that is ≥ 10° greater than the preoperative measurement. RESULTS: 90 patients (16.5 ± 1.9 yo, 65.6% male) were included. Preoperative and 2-year postoperative major kyphosis was 74.6 ± 11.6° and 45.9 ± 10.5°, respectively. Twenty-two (24.4%) patients developed PJK at 2 years. Patients with UIV below T2 had a 2.09 times increased risk of PJK when compared to those with UIV at or above T2, adjusting for distance between UIV and preoperative kyphosis apex [95% Confidence Interval (CI) 0.94; 4.63, p = 0.070]. Patients with UIV ≤ 4.5 vertebrae from the apex had a 1.57 times increased risk of PJK, adjusting for UIV relative to T2 [95% CI 0.64; 3.87, p = 0.326]. CONCLUSION: SK patients with UIV below T2 had an increased risk of developing PJK at 2 years following PSF. This association supports consideration of UIV location during preoperative planning. LEVEL OF EVIDENCE: Prognostic Level II.

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STUDY DESIGN: Retrospective cohort study. OBJECTIVES: The primary objective was to evaluate the impact of the upper instrumented level (UIV) being at C2 vs C3 in posterior cervical construct on patient reported outcomes (PROs) up to 24 months after surgery for cervical degenerative myelopathy (DCM). Secondary objectives were to compare operative time, intra-operative blood loss (IOBL), length of stay (LOS), adverse events (AEs) and re-operation. METHODOLOGY: Patients who underwent a posterior cervical instrumented fusion (3 and + levels) with a C2 or C3 UIV, with 24 months follow-up were analyzed. PROs (NDI, EQ5D, SF-12 PCS/MCS, NRS arm/neck pain) were compared using ANCOVA. Operative duration, IOBL, AEs, and re-operation were compared. Subgroup analysis was performed on patient presenting with pre-operative malalignment (cervical sagittal vertical axis ≥40 mm and/or T1slope- cervical lordosis >15°). RESULTS: 173 patients were included, of which 41 (24%) had a C2 UIV and 132 (76%) a C3 UIV. There was no statistically significant difference between the groups for the changes in PROs up to 24 months. Subgroup analysis of patients with pre-operative malalignment showed a trend towards greater improvement in the NDI at 12 months with a C2 UIV (P = .054). Operative time, IOBL and peri-operative AEs were more in C2 group (P < .05). There was no significant difference in LOS and re-operation (P > .05). CONCLUSION: In this observational study, up to 24 months after surgery for posterior cervical fusion in DCM greater than 3 levels, PROs appear to evolve similarly.

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STUDY DESIGN: A retrospective study. OBJECTIVES: Curve flexibility in patients with adolescent idiopathic scoliosis (AIS) can be evaluated using different techniques. This study aimed to determine whether the combination of side-bending (SB) and traction (TX) radiographs influences preoperative planning for AIS than either radiograph alone. METHODS: Thirty-two spine surgeons were asked to review 30 AIS Lenke type 1 cases and select an upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV) for the posterior spinal instrumentation of each case. Each rater reviewed the cases 3 times in each round. The raters were provided with the full-length posteroanterior (PA) and lateral standing and SB radiographs for round 1; PA, lateral, and TX radiographs for round 2; and PA, lateral, SB, and TX radiographs for round 3. Intra- and inter-rater reliabilities were evaluated using Kappa statistics. RESULTS: The intra-rater reliability for UIV and LIV was 0.657 and 0.612 between rounds 1 and 2, 0.634 and 0.692 between rounds 1 and 3, and 0.659 and 0.638 between rounds 2 and 3, respectively, which indicated substantial agreement between rounds. The inter-rater kappa reliabilities for UIV and LIV selection were 0.103 and 0.412 for round 1, 0.121 and 0.380 for round 2, and 0.125 and 0.368 for round 3, indicating slight to moderate agreement between raters. CONCLUSIONS: Whether raters used either SB or TX radiography, or both in addition to PA and lateral standing radiographs, did not influence the decision making for UIV or LIV of AIS Lenke type 1 surgery.

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PURPOSE: This study aimed to estimate the accuracy of pedicle screw (PS) placement in degenerative scoliosis surgery, characterize a patient population with PS misplacement, and analyze the association between misplaced PS vector and lumbar coronal curve. METHODS: In this study, 122 patients (average age 68.6 years), who underwent corrective and decompression surgery, were selected retrospectively. PS accuracy was evaluated in the thoracic to lumbar spine. We identified characteristics of misplacement in each patient. Screw positions were categorized into grade A, entirely in the pedicle; grade B, < 2 mm breach; grade C, 2-4 mm breach; and grade D, > 4 mm breach using postoperative computed tomography. RESULTS: The mean preoperative lumbar coronal curve was 32.3 ± 18.4°, and the number of fused vertebrae was 8.9 ± 2.8. A total of 2032 PS were categorized as follows: grade A, 1897 PS (93.3%); grade B, 67 (3.3%); grade C, 26 (1.3%); and grade D, 43 (2.1%). One PS (grade D), inserted at T5, needed surgery for removal due to neurological deficit. The misplacement group (grades C and D) had a significantly stronger lumbar coronal curve and apical vertebral rotation than the accuracy group (grades A and B). Misplaced PS vector (direction and degree) was significantly correlated with inserted vertebral rotation. Grade D misplacement was distributed mainly around the transitional vertebra of the lumbar curve. CONCLUSIONS: The accuracy of PS insertion in the thoracic to lumbar spine was high in DS surgery, but the need for care was highlighted in the transitional vertebra.

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Objective: To review the research progress of upper instrumented vertebra (UIV) selection strategy for long-segment fixation (LSF) in adult degenerative scoliosis (ADS). Methods: The relevant domestic and foreign literature in recent years was reviewed, and the selection strategy of sagittal and coronal UIV for LSF in ADS patients, the relationship between UIV selection and proximal junctional kyphosis (PJK) and proximal junctional failure (PJF), the impact of minimally invasive spine surgery on the selection strategy of UIV were summarized. Results: LSF can restore the biomechanical balance of the spine and reconstruct the physiological curve of the spine for ADS patients. LSF should be selected for ADS patients with severe scoliosis, vertebral rotation, and severe sagittal imbalance. For patients with poor general condition, UIV can choose the thoracic and lumbar vertebrae to reduce the operation time and intraoperative bleeding, which is conducive to early mobilization and reduce complications; for patients with good general condition, the upper thoracic vertebrae can be considered if necessary, in order to achieve satisfactory long-term effectiveness. However, the lower thoracic vertebra (T 9、10) should be selected as much as possible to reduce postoperative complications such as PJK and PJF. In recent years, a new reference marker, the first coronal reverse vertebra was proposed, to guide the selection of UIV. But a large-sample multicenter randomized controlled study is needed to further verify its reliability. Studies have shown that different races and different living habits would lead to different parameters of the spine and pelvis, which would affect the selection of UIV. Minimally invasive surgeries have achieved satisfactory results in the treatment of ADS, but the UIV selection strategy in specific applications needs to be further studied. Conclusion: The selection strategy of UIV in LSF has not yet been unified. The selection of UIV in the sagittal plane of the upper thoracic spine, the lower thoracic spine, or the thoracolumbar spine should comprehensively consider the biomechanical balance of the spine and the general condition of the patient, as well as the relationship between the upper horizontal vertebra, the upper neutral vertebra, and the upper end vertebra on the coronal plane.

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Introduction: Several targets have been proposed to achieve satisfactory alignment and favorable outcomes in adult spinal deformity surgery. Stopping the upper instrumented vertebra (UIV) at the thoracolumbar junction levels, especially between T11 and L1, is considered a high-risk factor for the development of proximal junctional kyphosis (PJK). Nevertheless, it is unknown in which patients the results of surgery are satisfactory when L1 or L2 is set as UIV with lumbosacral fixation. This study aimed to identify the risk factors for PJK in patients with lumbosacral fixation with L1 or L2 as UIV. Methods: From January 2011 to December 2019, 21 consecutive patients who underwent lumbopelvic fixation for adult spinal deformity were included. The patients were divided into two groups: the PJK group (n=7) and the nonPJK group (n=14). Patients who experienced PJK within half a year of surgery were included in the PJK group. Pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt (PT), thoracic kyphosis (TK), thoracic compensation (TK compensation), sagittal vertical axis (SVA), T10-L2 angle, and T1 pelvic angle (TPA) were measured before and after surgery. Results: No difference was found between the two groups in terms of age and sex at the time of surgery. The indices that were significantly different between the two groups were preoperative PT, PI minus LL, TK, TPA, TK compensation, and postoperative T10-L2 angle. No significant differences were found in postoperative LL, PI minus LL, PT, TK, TPA, or SVA. Conclusions: Preoperative X-ray indices, including preoperative TPA, TK compensation, TK, PT, and PI-LL, determined the risk of PJK in fusions from the sacrum to L1 or L2. Appropriate patient selection is crucial for the success of this surgery.