Expressive power of ReLU and step networks under floating-point operations.

The study of the expressive power of neural networks has investigated the fundamental limits of neural networks. Most existing results assume real-valued inputs and parameters as well as exact operations during the evaluation of neural networks. However, neural networks are typically executed on computers that can only represent a tiny subset of the reals and apply inexact operations, i.e., most existing results do not apply to neural networks used in practice. In this work, we analyze the expressive power of neural networks under a more realistic setup: when we use floating-point numbers and operations as in practice. Our first set of results assumes floating-point operations where the significand of a float is represented by finite bits but its exponent can take any integer value. Under this setup, we show that neural networks using a binary threshold unit or ReLU can memorize any finite input/output pairs and can approximate any continuous function within an arbitrary error. In particular, the number of parameters in our constructions for universal approximation and memorization coincides with that in classical results assuming exact mathematical operations. We also show similar results on memorization and universal approximation when floating-point operations use finite bits for both significand and exponent; these results are applicable to many popular floating-point formats such as those defined in the IEEE 754 standard (e.g., 32-bit single-precision format) and bfloat16.

The positive impact of smoking cessation on fracture risk in a nationwide cohort study.

Many studies sought to demonstrate the association between smoking and fracture risk. However, the correlation between smoking and fractures remains controversial. This study aimed to examine the impact of smoking and smoking cessation on the occurrence of fractures using prospective nationwide cohort data. We enrolled those who underwent a National Health Insurance Service (NHIS) health checkup in 2009-2010 who had a previous health checkup 4-year prior (2005-2006). The study population of 4,028,559 subjects was classified into three groups (non-smoker, smoking cessation, current smoker). The study population was also analyzed according to fracture type (all fractures, vertebral fracture, hip fracture). Lastly, the smoking cessation group and current smoker group were divided into four subgroups based on a lifetime smoking amount cut-off of 20 pack-years (PY). Multivariate-adjusted hazard ratios (HRs) of fracture were examined through a Cox proportional hazards model. After multivariable adjustment, non-smokers showed the lowest risk of fracture (HR = 0.818, CI 0.807-0.828, p < 0.0001) and smoking cessation significantly lowered the risk of fracture (HR 0.938, 95% CI 0.917-0.959, p < 0.0001) compared to current smokers. Regardless of 20PY, all smoking cessation subgroups showed significantly less risk of fractures than current smokers with ≥ 20PYs. Smoking increases the risk of fracture, and smoking cessation lowers the risk of fracture.

Risk factors of adjacent-segment disease after short-segment fusion in patients with de novo degenerative lumbar scoliosis.

OBJECTIVE: Short-segment fusion (SSF) is an effective surgical option for appropriately selected patients with de novo degenerative lumbar scoliosis (DNDLS). Considering that DNDLS is frequently accompanied by multisegment degeneration and potential instability across the entire lumbar segments, it is inevitable that unhealthy segments remain after SSF, thereby increasing the potential risk of adjacent-segment disease (ASD) occurrence. Therefore, the authors aimed to identify the risk factors for ASD in patients with DNDLS who underwent SSF. METHODS: This retrospective study included 80 patients with DNDLS (Cobb angle > 10°) who underwent SSF (1 or 2 levels) between December 2010 and July 2018 with a minimum follow-up duration of 5 years. The participants were divided into two groups: ASD and non-ASD. ASD was defined as clinical ASD rather than radiographic ASD. Various patient and operative variables were compared between the groups. Global and regional radiographic parameters (preoperatively and postoperatively) were also compared between the two groups using plain radiography and MRI. Consequently, univariate and multivariate analyses were conducted to identify the risk factors for ASD occurrence. The receiver operating characteristic (ROC) curve was used to calculate the cutoff values. RESULTS: The mean ± SD age was 67.7 ± 7.2 years at the time of SSF, and there were 62 women (77.5%) enrolled in the study. Thirty patients (37.5%) were in the ASD group and 50 patients (62.5%) were in the non-ASD group. The mean time from the surgery to ASD diagnosis was 34.9 ± 28.2 months in ASD group. Thirteen patients required revision surgery at a mean time of 8.8 ± 7.0 months after ASD occurrence. Multivariate logistic regression analysis demonstrated that preoperative disc wedging angle (OR 1.806, 95% CI 1.255-2.598, p = 0.001), presence of facet tropism (defined as ≥ 10° difference between the facet joint angles of the right and left sides) (OR 5.534, 95% CI 1.528-20.040, p = 0.009), and foraminal stenosis ≥ grade 2 (OR 5.935, 95% CI 1.253-28.117, p = 0.025) were significant risk factors for ASD development. The cutoff value of the preoperative disc wedging angle was calculated to be 2.5° using the ROC curve. CONCLUSIONS: Preoperative disc wedging angle ≥ 2.5°, presence of facet tropism, and foraminal stenosis ≥ grade 2 were identified as significant risk factors for ASD development after SSF in patients with DNDLS.

State observer-based Physics-Informed Machine Learning for leader-following tracking control of mobile robot.

In this paper, the novel leader-following tracking control method is proposed for mobile robots, which consists estimation technique of the speed of the leader robot (LR), and a parameter-dependent controller for the follower robot (FR). To estimate the speed of LR, a novel Physics Informed Machine Learning (PIML) is proposed to learn the dynamics of the state observer via the error state model. The dynamics of the state observer in PIML play a significant role for stable learning and state estimation of uncertain models. The gain of the parameter-dependent controller is determined by the convex combination of the robust control technique via the polytopic model. Finally, the tracking performance of the proposed method is verified through the simulation and experiment.

Latissimus dorsi myocutaneous free flap for post-sacrectomy reconstruction: Outcomes compared with gluteal muscle flap.

BACKGROUND: Excision of sacral tumor results in extensive defects and vital organ exposure, requiring soft tissue reconstruction for dead space obliteration. Diverse reconstruction options, mainly regional flaps, have been utilized but are limited by high postoperative morbidity. A reliable reconstructive method with low morbidity and facilitated recovery has yet been sought for. In this study, we aimed to evaluate the use of free latissimus dorsi (LD) flap for post-sacrectomy defect reconstruction by comparing its outcomes with local gluteus maximus (GM) flap. METHODS: A retrospective review was conducted of all patients with sacral malignancy who underwent partial or total sacrectomy and immediate reconstruction with LD or GM flap between 2013 and 2022. Nineteen patients were analyzed, including 10 GM flaps and nine LD flaps. Postoperative outcomes were compared between the two groups. RESULTS: The average size of LD flaps was 173.8 cm2 . Seven patients developed complication in the GM group and two patients in the LD group. Complication rate at sacrectomy site was lower in the LD group (p = .003) showing complication-free sacrectomy site and two donor site seromas. The LD group resulted in shorter hospital stay (p = .033) and earlier ambulation than the GM group (p = .001). Mean follow-up period was 63 months for GM group and 17 months for LD group. Three patients in the GM group underwent re-operation, while no delayed complication was observed in the LD group. CONCLUSION: Free LD flaps may provide reliable outcomes with early recovery and may be considered an effective option for sacrectomy defect reconstruction.

Predictor of Postoperative Ambulatory Recovery in Metastatic Spinal Cord Compression with Delayed Surgical Timing and Progressive Paraplegia.

OBJECTIVE: To analyze preoperative predictors of ambulatory recovery after surgical treatment in metastatic spinal cord compression (MSCC) patients with delayed surgical timing and progressive paraplegia. METHODS: We reviewed patients with a preoperative lower-extremity motor grade of ≤3 and surgical timing ≥48 hours after the nonambulatory status. The recovery group (group R) and nonrecovery group (group NR) were classified according to ambulation assessment during follow-up. The data on patient demographics, origin of the primary tumor, pre and postoperative chemotherapy and radiation therapy, surgical procedures, Tokuhashi score, Karnofsky score, preoperative lower-extremity motor grade, and surgical timing were collected for analyzing predictors of postoperative ambulatory recovery. RESULTS: Of the 55 patients, 24 (43.6%) were group R and 31 patients were group NR. The preoperative motor grade of the lower extremities was the only predictive factor (P < 0.05). The mean hip flexor and knee extensor motor grades in group R were 2.0 ± 1.0 and 2.4 ± 1.1 respectively, while in group NR, they were 1.2 ± 1.0 and 1.3 ± 1.0. The odds ratios for failing to regain ambulatory ability were 12.6 in the knee extensor and 4.8 in the hip flexor when the motor grades 0-2 and 3 groups were compared. The rescue ratio of the preoperative hip flexor and knee extensor motor grade 0-2 group were 34.1% and 21.2%, grades 3 group were 71.4% and 77.3%, respectively. CONCLUSIONS: The significant predictive factor for ambulatory recovery was the preoperative lower-extremity motor grade. The preoperative knee extensor motor grade was identified as a more important factor than hip flexor motor grade in predicting ambulatory recovery.

Clinical Significance of Lordosis Orientation on Proximal Junctional Kyphosis Development in Long-Segment Fusion Surgery for Adult Spinal Deformity.

OBJECTIVE: We sought to evaluate the clinical impact of lordosis orientation (LO) on proximal junctional kyphosis (PJK) development in adult spinal deformity surgery. METHODS: This study included 152 patients who underwent low thoracic (T9-T12) to pelvis fusion and were followed up for ≥2 years. In the literature, 6 radiographic parameters representing LO were introduced, such as uppermost instrumented vertebra (UIV) slope, UIV inclination, UIV-femoral angle (UIVFA), thoracolumbar tilt, thoracolumbar slope, and lordosis tilt. Various clinical and radiographic factors including 6 LO parameters were investigated using logistic regression analysis to identify risk factors for PJK. RESULTS: The mean age was 69.4 years, and 136 patients were females (89.5%). PJK developed in 65 patients (42.8%). Multivariate logistic regression analysis revealed that only small postoperative pelvic incidence (PI)-lumbar lordosis (LL) (odds ratio [OR] = 0.962, 95% confidence interval: 0.929-0.996, P = 0.030) and large UIVFA (OR = 1.089, 95% confidence interval: 1.028-1.154, P = 0.004) were significant for PJK development. UIVFA showed significantly positive correlation with pelvic tilt (CC = 0.509), thoracic kyphosis (CC = 0.384), and lordosis distribution index (CC = 0.223). UIVFA was also negatively correlated with sagittal vertical axis (CC = -0.371). However, UIVFA did not correlate with LL, PI-LL, or T1 pelvic angle. CONCLUSIONS: LO significantly increases the risk of PJK development in ASD surgery. Multivariate analysis revealed that smaller postoperative PI-LL and greater UIVFA were significant risk factors for PJK. Surgeons should avoid undercorrection and overcorrection to prevent PJK development.

Proximal Junctional Failure after Corrective Surgery: Focusing on Elderly Patients with Severe Sagittal Imbalance.

Background: Previous reports with proximal junctional failure (PJF) included relatively young patients or deformity without sagittal imbalance. The present study focused on the two well-known risk factors for PJF, old age and severe sagittal imbalance. With these high-risk patients, the present study aimed to identify a strategy that could prevent PJF and to investigate whether the degree of correction would really affect the PJF occurrence. Methods: Patients who were ≥ 60 years of age and underwent long fusion (≥ 4) to the sacrum for severe sagittal imbalance (defined as pelvic incidence minus lumbar lordosis [PI-LL] ≥ 30°) were included. PJF was defined as a vertebral fracture at the uppermost instrumented vertebra (UIV) or UIV+1, failure of UIV fixation, myelopathy, or any need for proximal extension of fusion. Presumed risk factors were compared between the patients with and without PJF. Results: Total 146 patients (mean age, 68.4 years) with preoperative mean PI-LL of 46.8° were included. PJF developed in 39 patients (26.7%) at a mean of 18.1 months after surgery. Multivariate analysis showed that osteoporosis (odds ratio [OR], 2.812; p = 0.019) and UIV located below T10 (OR, 3.773; p = 0.010) were significant risk factors for developing PJF. However, the degree of correction did not affect PJF occurrence. Conclusions: The present study indicates that osteoporosis should be well corrected preoperatively and extending the fusion above T10 should be considered for severe imbalance in old patients. However, the amount of correction was not associated with PJF development.

Usefulness of the BIG Score in Predicting Massive Transfusion and In-Hospital Death in Adult Trauma Patients.

The base deficit (B), international normalized ratio (I), and Glasgow coma scale (GCS) (BIG) score is useful in predicting mortality in pediatric trauma patients; however, studies on the use of BIG score in adult patients with trauma are sparse. In addition, studies on the correlation between the BIG score and massive transfusion (MT) have not yet been conducted. This study aimed to evaluate the predictive value of BIG score for mortality and the need for MT in adult trauma patients. This retrospective study used data collected between 2016 and 2020 at our hospital's trauma center and registry. The predictive value of BIG score was compared with that of the Injury Severity Score (ISS) and Revised Trauma Score (RTS). Logistic regression analysis was carried out to assess whether BIG score was an independent risk factor. Receiver operating characteristic (ROC) curve analysis was performed, and predictive values were evaluated by measuring the area under the ROC curve (AUROC). In total, 5,605 patients were included in this study. In logistic regression analysis, BIG score was independently associated with in-hospital mortality (odds ratio (OR): 1.1859; 95% confidence interval (CI): 1.1636-1.2086) and MT (OR: 1.0802; 95% CI: 1.0609-1.0999). The AUROCs of BIG score for in-hospital mortality and MT were 0.852 (0.842-0.861) and 0.848 (0.838-0.857), respectively. Contrastingly, the AUROCs of ISS and RTS for in-hospital mortality were 0.795 (0.784-0.805) and 0.859 (0.850-0.868), respectively. Moreover, AUROCs of ISS and RTS for MT were 0.812 (0.802-0.822) and 0.838 (0.828-0.848), respectively. The predictive value of BIG score for mortality and MT was significantly higher than that of the ISS. The BIG score also showed a better AUROC for predicting in-hospital mortality compared with RTS. In conclusion, the BIG score is a useful indicator for predicting mortality and the need for MT in adult trauma patients.

Diagnosing Polypoidal Choroidal Vasculopathy Using Color Fundus Photography, Optical Coherence Tomography, and Optical Coherence Tomography Angiography.

PURPOSE: To compare the diagnostic accuracy of differentiating polypoidal choroidal vasculopathy (PCV) from exudative age-related macular degeneration (AMD), using color fundus photography (CFP), optical coherence tomography (OCT), and swept-source OCT angiography (SS-OCTA) without using indocyanine green angiography (ICGA). METHODS: Treatment-naive eyes with exudative AMD that underwent CFP, OCT, SS-OCTA, and ICGA imaging before treatment were identified. Images of each patient were categorized into two sets (set A, CFP + OCT; set B, CFP + SS-OCTA). In set B, both the en face and cross-sectional B scans were analyzed. Each set was reviewed by two graders, and it was determined whether the presumed diagnosis was PCV. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) for the diagnosis of PCV were assessed for each set by comparing diagnoses that included ICGA. The number of polypoidal lesions in each set was calculated and compared to ICGA. RESULTS: A total of 94 eyes from 94 patients with AMD were included in the study, of which 66.0% were male, and the mean age was 71.8 ± 9.0 years. The PCV diagnosis rate using ICGA was 45.7%. The sensitivity was 0.88 for set A and 0.93 for set B, while the specificity was 0.94 for set A and 0.96 for set B. The AUC was 0.90 (95% confidence interval [CI], 0.83-0.97) for set A and 0.96 (95% CI, 0.90-1.00) for set B. Set A detected 1.28 ± 0.91 polypoidal lesions, while set B detected 1.47 ± 1.01; ICGA showed 1.51 ± 0.86. CONCLUSIONS: This study highlights that, without using ICGA, both CFP combined with OCT and CFP combined with SS-OCTA demonstrate high sensitivity, specificity, and AUC in diagnosing PCV. It is evident that SS-OCTA contributes to enhancing sensitivity, specificity, and AUC for PCV diagnosis.

Introduction of a New Radiographic Parameter to Predict Proximal Junctional Kyphosis in Adult Spinal Deformity: UIVPTA (Uppermost Instrumented Vertebra-Pelvic Tilt Angle).

OBJECTIVE: To introduce a new sagittal parameter, uppermost instrumented vertebra-pelvic tilt angle (UIVPTA), and to determine the effects on the proximal junctional kyphosis (PJK) development in adult spinal deformity (ASD) surgery. METHODS: Patients ≥ 60 years with ASD who underwent low thoracic spine to pelvis fusion with a minimum of 2-years of follow-up were included in this study. Two groups were created according to PJK development. Various clinical and radiographic factors were compared between PJK and non-PJK groups to identify the risk factors for PJK. Cutoff value of UIVPTA for PJK development was calculated using receiver operating characteristic curve according to different pelvic incidence groups. Linear regression analysis was performed to identify factors to affect UIVPTA. RESULTS: One hundred fifity-one patients were included in this study. There were 135 female patients (89.4%). Mean age was 70.5 years. PJK developed in 65 patients (43.0%). Multivariate analysis showed that overcorrection relative to age-adjusted pelvic incidence (PI) minus lumbar lordosis (LL) (PI-LL) target and lower UIVPTA were independent risk factors for PJK. The cutoff value of UIVPTA for PJK development was calculated as 4.0° in patients with PI less than 45°, 9.5° in patients with PI between 45° and 60°, and 13.0° in patients with PI greater than 60°. Linear regression analysis showed that UIVPTA was positively affected by postoperative values of LL (coefficient = 0.505), PI-LL (coefficient = 0.674), and pelvic tilt (coefficient = 0.286). CONCLUSION: Optimal correction within the age-adjusted PI-LL combined with keeping UIVPTA within optimal range is suggested for the prevention of PJK.

Identifying the Unmet Medical Needs of HIV-Positive Subjects in Korea: Results of a Nationwide Online Survey.

An online survey was conducted in Korea to identify the unmet medical needs of people living with human immunodeficiency virus (HIV) (PLWH). Participants (n = 105) were mostly male (93.3%), aged >40 years (75.2%), and treated for ≥6 years post-diagnosis (61.9%). Most PLWH (71.4%) were very satisfied/satisfied with their HIV management. Areas of concern were quality of life (QoL) and mental health. Characteristics of a long-term therapeutic agent were 'low risk of resistance', 'high long-term viral suppression efficacy', and 'high degree of safety'. Pre-consultation QoL and mental health screening would be beneficial for the long-term success of HIV management.

Risk factors for radiographic progression of proximal junctional fracture in patients undergoing surgical treatment for adult spinal deformity.

OBJECTIVE: Proximal junctional fracture (PJFx) at the uppermost instrumented vertebra (UIV) or UIV+1 is the most common mechanism of proximal junctional failure (PJF). Few studies have assessed radiographic progression after PJFx development. Therefore, this study sought to identify the risk factors for radiographic progression of PJFx in the surgical treatment for adult spinal deformity. METHODS: In this retrospective study, among 317 patients aged > 60 years who underwent ≥ 5-level fusion from the sacrum, 76 with PJFx development were included. On the basis of the change in the proximal junctional angle (PJA), 2 groups were created: progression group (group P) (change ≥ 10°) and nonprogression group (group NP) (change < 10°). Patient, surgical, and radiographic variables were compared between the groups with univariate and multivariate analyses to demonstrate the risk factors for PJFx progression. The receiver operating characteristic (ROC) curve was used to calculate cutoff values. Clinical outcomes, such as visual analog scale (VAS) scores for back and leg pain, Oswestry Disability Index (ODI) score, the Scoliosis Research Society (SRS)-22 score, and the revision rate were compared between the 2 groups. RESULTS: The mean age at index surgery was 71.1 years, and 67 women were enrolled in the study (88.2%). There were 45 patients in group P and 31 in group NP. The mean increase in PJA was 15.6° (from 23.2° to 38.8°) in group P and 3.7° (from 17.2° to 20.9°) in group NP. Clinical outcomes were significantly better in group NP than group P, including VAS-back score, ODI score, and SRS-22 scores for all items. The revision rate was significantly greater in group P than in group NP (53.3% vs 25.8%, p = 0.001). Multivariate analysis revealed that overcorrection relative to the age-adjusted ideal pelvic incidence (PI)-lumbar lordosis (LL) target at index surgery (OR 4.484, p = 0.030), PJA at the time of PJFx identification (OR 1.097, p = 0.009), and fracture at UIV (vs UIV+1) (OR 3.410, p = 0.027) were significant risk factors for PJFx progression. The cutoff value of PJA for PJFx progression was calculated as 21° by using the ROC curve. CONCLUSIONS: The risk factors for further progression of PJFx were overcorrection relative to the age-adjusted PI-LL target at index surgery, PJA > 21° at initial presentation, and fracture at the UIV level. Close monitoring is warranted for such patients in order to not miss timely revision surgery.

Mortality risk after the first occurrence of osteoporotic vertebral compression fractures in the general population: A nationwide cohort study.

Osteoporotic vertebral compression fractures (OVCF) can cause severe pain, changes in balance, gait velocity, muscle fatigue, risk of falls, and subsequent fractures. Thus, OVCF significantly lowers the individual's health-related quality of life. Additionally, OVCF may increase patient mortality rates. However, studies on post-OVCF mortality are limited. This study aimed to evaluate mortality risk after the first occurrence of OVCF in the general population using a nationwide dataset from the Korean National Health Insurance System. We identified 291,203 newly diagnosed patients with OVCF and 873,609 patients without OVCF at a ratio of 1:3 matched by sex and age between 2010 and 2012. We investigated the latent characteristics of patients' demographic information and chronic comorbidities that could affect mortality when diagnosed with OVCF. By comparing the cohort data, the hazard ratio for subsequent mortality in patients with OVCF was calculated and adjusted based on several risk factors. Despite adjusting for demographic characteristics and chronic comorbidities, the risk of mortality was 1.22 times higher in the OVCF cohort than in the control group. Multivariate analysis showed that male sex, old age, low-income status, and high Charlson Comorbidity Index were associated with a higher risk of mortality. In addition, the presence of chronic comorbidities, including diabetes mellitus, ischemic heart disease, stroke, chronic obstructive pulmonary disease, cancer, and end-stage renal disease, was shown to increase the risk of mortality. This population-based cohort study showed that newly diagnosed OVCF significantly increased the subsequent risk of mortality. Moreover, post-OVCF mortality is influenced by demographic characteristics and chronic comorbidities.

Temperature Dependence of Nuclear Quadrupole Resonance and the Observation of Metal-Ligand Covalency in Actinide Complexes: 35Cl in Cs2UO2Cl4.

We report a study of the temperature dependence of 35Cl nuclear quadrupole resonance (NQR) transition energies and spin-lattice relaxation times (T1) for 235U-depleted dicesium uranyl tetrachloride (Cs2UO2Cl4) aimed at elucidating electronic interactions between the uranium center and atoms in the equatorial plane of the UO22+ ion. The transition frequency decreases slowly with temperature below 75 K and with a more rapid linear dependence above this temperature. The spin-lattice relaxation time becomes shorter with temperature, and as temperatures increase, the T1 decrease becomes nearly quadratic. The observed trends are reproduced by a model that assumes phonon-induced fluctuations of the electric field gradient tensor and partial electron delocalization from Cl to U. The fit of the theoretical model to experimental data allows a Debye temperature of 96 K to be estimated. The generalization of this approach to investigations of covalency in actinide-ligand bonding is examined.

Clinicopathological Features and Prognosis of Resected Pancreatic Ductal Adenocarcinoma Patients with Claudin-18 Overexpression.

Claudin-18.2 (CLDN18.2) is specifically expressed in pancreatic precancerous lesions and pancreatic ductal adenocarcinoma (PDAC). We assessed the clinical characteristics of patients with CLDN18.2-overexpressing pancreatic cancer to identify patients who might benefit from CLDN18-targeted treatment. A total of 130 patients with surgically resected PDAC were investigated for the immunohistochemical expression of claudin-18 (CLDN18). The CLDN18 staining intensities (0-3+) and relative proportion of positive tumor cells were analyzed by two independent raters. Tumors positive for CLDN18 expression were defined as ≥80% of tumor cells with 2+ or 3+ staining intensity in a CLDN18 immunohistochemical assay. Positive CLDN18 expression was present in 41/130 (31.5%) surgically resected PDACs and the relative proportion of positive tumor cells and the staining intensity were directly correlated (p < 0.001). Positive CLDN18 expression was significantly associated with well-differentiated tumors (p < 0.001) and less regional node involvement (p = 0.045). The positive CLDN18-expressing group showed no statistical difference in median overall survival (17.4 months vs. 20.6 months, p = 0.770) compared to the negative CLDN18-expressing group. Distant nodal metastasis was more frequent in the positive CLDN18-expressing group (p = 0.011). CLDN18 is frequently expressed in PDAC, and high CLDN18-expressing PDACs showed some different clinicopathologic characteristics. High CLDN18 expression was not associated with prognosis in patients with surgically resected PDAC.

Radiographic Factors of Proximal Junctional Failure According to Age Groups in Adult Spinal Deformity.

Background: Patient age has been associated with the development of proximal junctional failure (PJF). The characteristics of adult spinal deformity (ASD) are considered different between younger and older age groups. We hypothesized that the radiographic risk factors of PJF would be different according to age groups. This study aimed to evaluate different radiographic risk factors of PJF between two age groups undergoing thoracolumbar fusion for ASD. Methods: ASD patients aged ≥ 60 years who underwent thoracolumbar fusion from the low thoracic level (T9-T12) to the sacrum were included. The minimum follow-up duration was 2 years. PJF was defined as proximal junctional angle (PJA) ≥ 20°, fixation failure, fracture, myelopathy, or necessity of revision surgery. Using various radiographic risk factors including age-adjusted ideal pelvic incidence (PI)-lumbar lordosis (LL), univariate and multivariate analyses were performed separately in two age groups: < 70 years and ≥ 70 years. Results: A total of 186 patients (90.3% women) with a mean age of 69 years were enrolled. The mean follow-up duration was 67.4 months. PJF developed in 97 patients (52.2%). There were fractures in 53 patients, PJA ≥ 20° in 26, fixation failure in 12, and myelopathy in 6. PJF developed more frequently in patients 70 years or older than in those younger than 70 years. In patients aged less than 70 years, preoperative LL, PI-LL, and a change in LL were significant risk factors in univariate analysis. Multivariate analysis showed only a change in LL was significant for PJF development (odds ratio [OR], 1.025; p = 0.021). On the other hand, in patients 70 years or older, postoperative LL, postoperative PI-LL, and overcorrection relative to the conventional PI-LL target (within ± 10°) and age-adjusted ideal PI-LL target were significant risk factors. On multivariate analysis, only overcorrection of PI-LL relative to the age-adjusted ideal target was a single significant risk factor of PJF (OR, 5.250; p = 0.024). Conclusions: In patients younger than 70 years, a greater change in LL was associated with PJF development regardless of PI-related values. However, in older patients, overcorrection of PI-LL relative to the age-adjusted PI-LL target was a significant risk factor of PJF.

A Comprehensive Review on Ensemble Solar Power Forecasting Algorithms.

With increasing demand for energy, the penetration of alternative sources such as renewable energy in power grids has increased. Solar energy is one of the most common and well-known sources of energy in existing networks. But because of its non-stationary and non-linear characteristics, it needs to predict solar irradiance to provide more reliable Photovoltaic (PV) plants and manage the power of supply and demand. Although there are various methods to predict the solar irradiance. This paper gives the overview of recent studies with focus on solar irradiance forecasting with ensemble methods which are divided into two main categories: competitive and cooperative ensemble forecasting. In addition, parameter diversity and data diversity are considered as competitive ensemble forecasting and also preprocessing and post-processing are as cooperative ensemble forecasting. All these ensemble forecasting methods are investigated in this study. In the end, the conclusion has been drawn and the recommendations for future studies have been discussed.

Does the Amount of Correction of Sagittal Deformity Really Promote Proximal Junctional Kyphosis? Multivariate Analyses According to Uppermost Instrumented Vertebra Levels.

BACKGROUND: The present study assumed that the effects of deformity correction amounts on proximal junctional kyphosis (PJK) development after long deformity surgery would vary according to uppermost instrumented vertebrae (UIV) levels. Our study was to reveal the association between the amount of correction and PJK according to UIV levels. METHODS: Adult spinal deformity patients aged >50 years who underwent thoracolumbar fusion (≥4 levels) were included. PJK was defined by proximal junctional angles ≥15°. Presumed demographic and radiographic risk factors for PJK were evaluated including parameters regarding the correction amount such as postoperative change in lumbar lordosis and postoperative offset grouping, the value associated with age-adjusted pelvic incidence-lumbar lordosis mismatch. The patients were divided according to UIV levels of T10 or above (group A) and T11 or below (group B). Multivariate analyses were performed separately for both groups. RESULTS: The present study included 241 patients (74 for group A and 167 for group B). PJK developed in approximately half of all patients within an average of 5 years of follow-up. For group A, only body mass index (P = 0.002) was associated with PJK. No radiographic parameters were correlated. For group B, postoperative change in lumbar lordosis (P = 0.009) and offset value (P = 0.030) were significant risk factors for PJK development. CONCLUSIONS: The correction amount of sagittal deformity increased the risk of PJK only in patients with UIV at or below T11. However, it was not associated with PJK development in patients with UIV at or above T10.

Long-term Radiographic and Clinical Outcomes After Selective Thoracic Fusion for Adolescent Idiopathic Scoliosis With Lenke 1C Curve.

BACKGROUND: Despite the promising results with selective thoracic fusion (STF) in patients with adolescent idiopathic scoliosis (AIS) of the Lenke 1C curve, postoperative coronal imbalance and progression of the unfused lumbar curve have been concerns in long-term follow-up. In this study, we aimed to investigate the radiographic and clinical outcomes after STF for AIS with Lenke 1C curve with long-term follow-up. METHODS: A total of 30 patients with AIS with Lenke 1C curves who underwent STF between 2005 and 2017 were included. Minimum follow-up duration was 5 years. Time-dependent changes in radiographic parameters were investigated preoperatively, immediately postoperatively, and at the last follow-up. In addition, radiographic adverse events such as coronal decompensation (CD), lumbar decompensation (LD), distal adding-on (DA) phenomenon, and trunk shift were evaluated at the last follow-up. The Scoliosis Research Society-22 score was used for clinical outcome evaluation. RESULTS: The mean age at the time of surgery was 13.8 years. The mean follow-up duration was 6.7 ± 0.8 years. The main thoracic curve significantly improved from 57 degrees to 23 degrees (60% correction), and the thoracolumbar/lumbar curve significantly improved from 47 degrees to 28 degrees (41% correction). Coronal balance was 15 mm after surgery but significantly improved to 10 mm at the last follow-up ( P = 0.033). At the final follow-up, 11 patients (37%) sustained at least one of the radiographic adverse events: CD in 5 patients (17%), LD in 3 (10%), DA in 4 (13%), and trunk shift in 3 (10.%). However, there were no cases requiring revision surgery. In addition, there were no significant differences in any items or total Scoliosis Research Society-22 score between the patients with and without radiographic adverse events. CONCLUSION: STF in Lenke 1C curves showed an acceptable risk of adverse radiographic events such as CD, LD, DA, and trunk shift in long-term follow-up. We suggest that STF without fusion to the thoracolumbar/lumbar curve would be sufficient in treating AIS with Lenke 1C curve. LEVEL OF EVIDENCE: Level III.