Finite Element Analysis of the Biomechanical Effects of 3 Posterolateral Corner Reconstruction Techniques for the Knee Joint.

PURPOSE: To compare the forces exerted on the cruciate ligaments and the contact stresses on the tibiofemoral (TF) and patellofemoral (PF) joints with respect to 3 different tibial- and fibular-based posterolateral corner (PLC) reconstructions under dynamic loading conditions. METHODS: A subject-specific finite element knee model was developed by using 3-dimensional anatomic data from motion captures in gait and squat activities, including in vivo knee joint kinematics and muscle forces for the single subject. Cruciate ligament forces and contact stresses on the TF and PF joints under 3 PLC reconstruction techniques (tibial-based, TBR; modified fibular-based, mFBR; conventional fibular-based, cFBR) and PLC-deficient models were compared with those of the intact model in gait and squat loading conditions. RESULTS: The cruciate ligament forces in the 3 surgical models differed from those in the intact model. The greatest differences in ligament forces from the intact model were found in the cFBR model, whereas there were no remarkable differences between the TBR and mFBR models in both gait and squat loading conditions. Contact stresses on the lateral TF and PF joints of the 3 surgical models were greater than those of the intact model under the squat loading condition. CONCLUSIONS: The biomechanical effects achieved using the anatomic reconstruction technique were found to be improved compared with those using nonanatomic reconstruction techniques. However, the ligament forces and contact stresses under normal conditions could not be restored through any of the 3 techniques. CLINICAL RELEVANCE: Anatomic TBR and FBR for grade III PLC injuries could restore better biomechanics in the knee joint compared with nonanatomic reconstruction. However, discrepancy with the normal condition requires further modification of surgical techniques.

A 3D Human-Machine Integrated Design and Analysis Framework for Squat Exercises with a Smith Machine.

In this paper, we propose a three-dimensional design and evaluation framework and process based on a probabilistic-based motion synthesis algorithm and biomechanical analysis system for the design of the Smith machine and squat training programs. Moreover, we implemented a prototype system to validate the proposed framework. The framework consists of an integrated human-machine-environment model as well as a squat motion synthesis system and biomechanical analysis system. In the design and evaluation process, we created an integrated model in which interactions between a human body and machine or the ground are modeled as joints with constraints at contact points. Next, we generated Smith squat motion using the motion synthesis program based on a Gaussian process regression algorithm with a set of given values for independent variables. Then, using the biomechanical analysis system, we simulated joint moments and muscle activities from the input of the integrated model and squat motion. We validated the model and algorithm through physical experiments measuring the electromyography (EMG) signals, ground forces, and squat motions as well as through a biomechanical simulation of muscle forces. The proposed approach enables the incorporation of biomechanics in the design process and reduces the need for physical experiments and prototypes in the development of training programs and new Smith machines.

Multimorbidity in atrial fibrillation for clinical implications using the Charlson Comorbidity Index.

BACKGROUND: Predicting survival in atrial fibrillation (AF) patients with comorbidities is challenging. This study aimed to assess multimorbidity in AF patients using the Charlson Comorbidity Index (CCI) and its clinical implications. METHODS: We analyzed 451,368 participants from the Korea National Health Insurance Service-Health Screening cohort (2002-2013) without prior AF diagnoses. Patients were categorized into new-onset AF and non-AF groups, with a high CCI defined as ≥4 points. Antithrombotic treatment and outcomes (all-cause death, stroke, major bleeding, and heart failure [HF] hospitalization) were evaluated over 9 years. RESULTS: In total, 9.5% of the enrolled patients had high CCI. During follow-up, 12,241 patients developed new-onset AF. Among AF patients, antiplatelet drug use increased significantly in those with high CCI (adjusted odds ratio [OR] 1.05, 95%confidence interval [CI] 1.02-1.08, P < .001). However, anticoagulants were significantly less prescribed in patients with high CCI (OR 0.97, 95%CI 0.95-0.99, P = .012). Incidence of adverse events (all-cause death, stroke, major bleeding, HF hospitalization) progressively increased in this order: low CCI without AF, high CCI without AF, low CCI with AF, and high CCI with AF (all P < .001). Furthermore, high CCI with AF had a significantly higher risk compared to low CCI without AF (all-cause death, adjusted hazard ratio [aHR] 2.52, 95% CI 2.37-2.68, P < .001; stroke, aHR 1.43, 95% CI 1.29-1.58, P < .001; major bleeding, aHR 1.14, 95% CI 1.04-1.26, P = .007; HF hospitalization, aHR 4.75, 95% CI 4.03-5.59, P < .001). CONCLUSIONS: High CCI predicted increased antiplatelet use and reduced oral anticoagulant prescription. AF was associated with higher risks of all-cause death, stroke, major bleeding, and HF hospitalization compared to high CCI.

Differentiation Between Invasive Adenocarcinoma and Focal Interstitial Fibrosis among Persistent Pulmonary Part-solid Nodules: With Emphasis on the CT Morphologic Analysis.

PURPOSE: Focal interstitial fibrosis (FIF) manifesting as a persistent part-solid nodule (PSN) has been mistakenly treated surgically due to similar imaging features to invasive adenocarcinoma (ADC). The purpose of this study was to observe predictive imaging features correlated with FIF through CT morphologic analysis. MATERIALS AND METHODS: From January 2009 to December 2020, 44 patients with surgically proven FIF in a single institution were enrolled and compared with 88 ADC patients through propensity score matching. Patient characteristics and CT morphologic analysis of persistent PSNs were used to identify predictive imaging features of FIF. Receiver operating characteristic (ROC) curve analysis was used to quantify the performance of imaging features. RESULTS: A total of 132 patients with 132 PSNs (44 FIF, 88 ADC; mean age, 67.7±7.58; 75 females) were involved in our analysis. Multivariable analysis demonstrated that preserved peritumoral vascular margin (preserved vascular margin), preserved secondary pulmonary lobule margin (preserved lobular margin), and lower coronal to axial ratio (C/A ratio; cutoff: 1.005) were significant independent predictors of FIF (P<0.05). ROC curve analysis to evaluate the predictive value of the logistic model based on the imaging features of FIF, and the AUC value was 0.881. CONCLUSION: CT imaging features of preserved vascular margin, preserved lobular margin, and lower C/A ratio (cutoff, <1.005) might be helpful imaging features in discriminating FIF over ADC among persistent PSN in clinical practice.

Net clinical benefit of oral anticoagulants in Korean atrial fibrillation patients with low to intermediate stroke risk: A report from the Clinical Survey on Stroke Prevention in patients with Atrial Fibrillation (CS-SPAF).

Background: The balance of stroke risk reduction and potential bleeding risk associated with antithrombotic treatment (ATT) remains unclear in atrial fibrillation (AF) at non-gender CHA2DS2-VASc scores 0-1. A net clinical benefit (NCB) analysis of ATT may guide stroke prevention strategies in AF with non-gender CHA2DS2-VASc scores 0-1. Methods: This multi-center cohort study evaluated the clinical outcomes of treatment with a single antiplatelet (SAPT), vitamin K antagonist (VKA), and non-VKA oral anticoagulant (NOAC) in non-gender CHA2DS2-VASc score 0-1 and further stratified by biomarker-based ABCD score (Age [≥60 years], B-type natriuretic peptide [BNP] or N-terminal pro-BNP [≥300 pg/mL], creatinine clearance [<50 mL/min], and dimension of the left atrium [≥45 mm]). The primary outcome was the NCB of ATT, including composite thrombotic events (ischemic stroke, systemic embolism, and myocardial infarction) and major bleeding events. Results: We included 2465 patients (age 56.2 ± 9.5 years; female 27.0%) followed-up for 4.0 ± 2.8 years, of whom 661 (26.8%) were treated with SAPT; 423 (17.2%) with VKA; and 1040 (42.2%) with NOAC. With detailed risk stratification using the ABCD score, NOAC showed a significant positive NCB compared with the other ATTs (SAPT vs. NOAC, NCB 2.01, 95% confidence interval [CI] 0.37-4.66; VKA vs. NOAC, NCB 2.38, 95% CI 0.56-5.40) in ABCD score ≥1. ATT failed to show a positive NCB in patients with truly low stroke risk (ABCD score = 0). Conclusions: In the Korean AF cohort at non-gender CHA2DS2-VASc scores 0-1, NOAC showed significant NCB advantages over VKA or SAPT with ABCD score ≥1.

Predictors of critical illness among young males with chest pain, abdominal pain, or headaches in the Republic of Korea Army.

Purpose: Chest pain, abdominal pain, and headache are common symptoms associated with critical illness. Here, we aimed to evaluate predictors associated with critical illness in young males of the Republic of Korea Army. Methods: We retrospectively reviewed previously healthy young males with chest pain, abdominal pain, or headaches who visited Armed Forces Seoul District Hospital between January 2019 and December 2020. Critical illness was defined as a condition that required hospitalization, a procedure or surgery, or referral to a tertiary hospital. The symptoms and signs of critical illness were evaluated. Results: Of the 762 enrolled patients, a critical illness was diagnosed in 45 patients (5.9%). Among chest pain signs, palpitation (odds ratio [OR], 22.8; 95% confidence interval [CI], 5.08-102.4; p < 0.001), exertional dyspnea (OR, 16.3; 95% CI, 3.38-78.8; p = 0.001), duration (> 5 minutes) (OR, 7.54; 95% CI, 1.93-29.49; p = 0.004), and squeezing type (OR, 5.28; 95% CI, 1.11-25.11; p = 0.037) were significantly associated with critical illness. Among abdominal pain signs, right-lower-quadrant tenderness (OR, 11.87; 95% CI, 4.671-31.87; p < 0.001) was an alarming sign. For headaches, criticality was low (1.5%), and half of patients with critical illness were diagnosed incidentally regardless of headache. Conclusion: We identified symptoms and signs significantly associated with critical illness in young male patients. This study might serve as a reference for deciding when to transfer soldiers in the field to a rear hospital, thereby contributing to the welfare and combat power of soldiers.

Validation of Biomarker-Based ABCD Score in Atrial Fibrillation Patients with a Non-Gender CHA2DS2-VASc Score 0-1: A Korean Multi-Center Cohort.

PURPOSE: Atrial fibrillation (AF) patients with low to intermediate risk, defined as non-gender CHA2DS2-VASc score of 0-1, are still at risk of stroke. This study verified the usefulness of ABCD score [age (≥60 years), B-type natriuretic peptide (BNP) or N-terminal pro-BNP (≥300 pg/mL), creatinine clearance (<50 mL/min/1.73 m²), and dimension of the left atrium (≥45 mm)] for stroke risk stratification in non-gender CHA2DS2-VASc score 0-1. MATERIALS AND METHODS: This multi-center cohort study retrospectively analyzed AF patients with non-gender CHA2DS2-VASc score 0-1. The primary endpoint was the incidence of stroke with or without antithrombotic therapy (ATT). An ABCD score was validated. RESULTS: Overall, 2694 patients [56.3±9.5 years; female, 726 (26.9%)] were followed-up for 4.0±2.8 years. The overall stroke rate was 0.84/100 person-years (P-Y), stratified as follows: 0.46/100 P-Y for an ABCD score of 0; 1.02/100 P-Y for an ABCD score ≥1. The ABCD score was superior to non-gender CHA2DS2-VASc score in the stroke risk stratification (C-index=0.618, p=0.015; net reclassification improvement=0.576, p=0.040; integrated differential improvement=0.033, p=0.066). ATT was prescribed in 2353 patients (86.5%), and the stroke rate was significantly lower in patients receiving non-vitamin K antagonist oral anticoagulant (NOAC) therapy and an ABCD score ≥1 than in those without ATT (0.44/100 P-Y vs. 1.55/100 P-Y; hazard ratio=0.26, 95% confidence interval 0.11-0.63, p=0.003). CONCLUSION: The biomarker-based ABCD score demonstrated improved stroke risk stratification in AF patients with non-gender CHA2DS2-VASc score 0-1. Furthermore, NOAC with an ABCD score ≥1 was associated with significantly lower stroke rate in AF patients with non-gender CHA2DS2-VASc score 0-1.

Clinical Characteristics and Disease Progression in Early-Stage COVID-19 Patients in South Korea.

A rapid increase in the number of patients with coronavirus disease 19 (COVID-19) may overwhelm the available medical resources. We aimed to evaluate risk factors for disease severity in the early stages of COVID-19. The cohort comprised 293 patients with COVID-19 from 5 March 2020, to 18 March 2020. The Korea Centers for Disease Control and Prevention (KCDC) classification system was used to triage patients. The clinical course was summarized, including the impact of drugs (angiotensin II receptor blockers [ARB], ibuprofen, and dipeptidyl peptidase-4 inhibitors [DPP4i]) and the therapeutic effect of lopinavir/ritonavir. After adjusting for confounding variables, prior history of drug use, including ARB, ibuprofen, and DPP4i was not a risk factor associated with disease progression. Patients treated with lopinavir/ritonavir had significantly shorter progression-free survival than those not receiving lopinavir/ritonavir. KCDC classification I clearly distinguished the improvement/stabilization group from the progression group of COVID-19 patients (AUC 0.817; 95% CI, 0.740-0.895).

Usefulness of P Wave Duration in Embolic Stroke of Undetermined Source.

The investigation of the potential association between ischemic stroke and subclinical atrial fibrillation (SCAF) is important for secondary prevention. We aimed to determine whether SCAF can be predicted by atrial substrate measurement with P wave signal-averaged electrocardiography (SAECG). We recruited 125 consecutive patients with embolic stroke of undetermined source (ESUS) and 125 patients with paroxysmal atrial fibrillation as controls. All participants underwent P wave SAECG at baseline, and patients with ESUS were followed up with Holter monitoring and electrocardiography at baseline, 3, 6, and 12 months after discharge and every 6 months thereafter. In the ESUS group, 32 (25.6%) patients were diagnosed with SCAF during follow-up. There were no significant differences between the groups regarding atrial substrate. P wave duration (PWD) was a significant predictor of SCAF. Stroke recurrence occurred in 22 patients (17.6%), and prolonged PWD (≥ 135 ms) predicted stroke recurrence more robustly than SCAF detection. In ESUS patients, PWD can be a useful biomarker to predict SCAF and to identify patients who are more likely to have a recurrent embolic stroke associated with an atrial cardiopathy. Further research is needed for supporting the utility and applicability of PWD.

Biomechanical evaluation of the influence of posterolateral corner structures on cruciate ligaments forces during simulated gait and squatting.

Posterolateral corner (PLC) structures of the knee joint comprise complex anatomical soft tissues that support static and dynamic functional movements of the knee. Most previous studies analyzed posterolateral stability in vitro under static loading conditions. This study aimed to evaluate the contributions of the lateral (fibular) collateral ligament (LCL), popliteofibular ligament (PFL), and popliteus tendon (PT) to cruciate ligament forces under simulated dynamic loading conditions by using selective individual resection. We combined medical imaging and motion capture of healthy subjects (four males and one female) to develop subject-specific knee models that simulated the 12 degrees of freedom of tibiofemoral and patellofemoral joint behaviors. These computational models were validated by comparing electromyographic (EMG) data with muscle activation data and were based on previous experimental studies. A rigid multi-body dynamics simulation using a lower extremity musculoskeletal model was performed to incorporate intact and selective resection of ligaments, based on a novel force-dependent kinematics method, during gait (walking) and squatting. Deficiency of the PLC structures resulted in increased loading on the posterior cruciate ligament and anterior cruciate ligament. Among PLC structures, the PT is the most influential on cruciate ligament forces under dynamic loading conditions.

Musculoskeletal model-based inverse dynamic analysis under ambulatory conditions using inertial motion capture.

Inverse dynamic analysis using musculoskeletal modeling is a powerful tool, which is utilized in a range of applications to estimate forces in ligaments, muscles, and joints, non-invasively. To date, the conventional input used in this analysis is derived from optical motion capture (OMC) and force plate (FP) systems, which restrict the application of musculoskeletal models to gait laboratories. To address this problem, we propose the use of inertial motion capture to perform musculoskeletal model-based inverse dynamics by utilizing a universally applicable ground reaction force and moment (GRF&M) prediction method. Validation against a conventional laboratory-based method showed excellent Pearson correlations for sagittal plane joint angles of ankle, knee, and hip (ρ=0.95, 0.99, and 0.99, respectively) and root-mean-squared-differences (RMSD) of 4.1 ±â€¯1.3°, 4.4 ±â€¯2.0°, and 5.7 ±â€¯2.1°, respectively. The GRF&M predicted using IMC input were found to have excellent correlations for three components (vertical: ρ=0.97, RMSD = 9.3 ±â€¯3.0 %BW, anteroposterior: ρ=0.91, RMSD = 5.5 ±â€¯1.2 %BW, sagittal: ρ=0.91, RMSD = 1.6 ±â€¯0.6 %BW*BH), and strong correlations for mediolateral (ρ=0.80, RMSD = 2.1 ±â€¯0.6 %BW) and transverse (ρ=0.82, RMSD = 0.2 ±â€¯0.1 %BW*BH). The proposed IMC-based method removes the complexity and space restrictions of OMC and FP systems and could enable applications of musculoskeletal models in either monitoring patients during their daily lives or in wider clinical practice.

Biomechanical influence of deficient posterolateral corner structures on knee joint kinematics: A computational study.

The posterolateral corner (PLC) structures including the popliteofibular ligament (PFL), popliteus tendon (PT) and lateral collateral ligament (LCL) are important soft tissues for posterior translational, external rotational, and varus angulation knee joint instabilities. The purpose of this study was to determine the effects of deficient PLC structures on the kinematics of the knee joint under gait and squat loading conditions. We developed subject-specific computational models with full 12-degree-of-freedom tibiofemoral and patellofemoral joints for four male subjects and one female subject. The subject-specific knee joint models were validated with computationally predicted muscle activation, electromyography data, and experimental data from previous study. According to our results, deficiency of the PFL did not significantly influence knee joint kinematics compared to an intact model under gait loading conditions. Compared with an intact model under gait and squat loading conditions, deficiency of the PT led to significant increases in external rotation and posterior translation, while LCL deficiency increased varus angulation. Deficiency of all PLC structures led to the greatest increases in external rotation, varus angulation, and posterior translation. These results suggest that the PT is an important structure for external rotation and posterior translation, while the LCL is important for varus angulation under dynamic loading conditions. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1-8, 2018.

Dynamically adjustable foot-ground contact model to estimate ground reaction force during walking and running.

Human dynamic models have been used to estimate joint kinetics during various activities. Kinetics estimation is in demand in sports and clinical applications where data on external forces, such as the ground reaction force (GRF), are not available. The purpose of this study was to estimate the GRF during gait by utilizing distance- and velocity-dependent force models between the foot and ground in an inverse-dynamics-based optimization. Ten males were tested as they walked at four different speeds on a force plate-embedded treadmill system. The full-GRF model whose foot-ground reaction elements were dynamically adjusted according to vertical displacement and anterior-posterior speed between the foot and ground was implemented in a full-body skeletal model. The model estimated the vertical and shear forces of the GRF from body kinematics. The shear-GRF model with dynamically adjustable shear reaction elements according to the input vertical force was also implemented in the foot of a full-body skeletal model. Shear forces of the GRF were estimated from body kinematics, vertical GRF, and center of pressure. The estimated full GRF had the lowest root mean square (RMS) errors at the slow walking speed (1.0m/s) with 4.2, 1.3, and 5.7% BW for anterior-posterior, medial-lateral, and vertical forces, respectively. The estimated shear forces were not significantly different between the full-GRF and shear-GRF models, but the RMS errors of the estimated knee joint kinetics were significantly lower for the shear-GRF model. Providing COP and vertical GRF with sensors, such as an insole-type pressure mat, can help estimate shear forces of the GRF and increase accuracy for estimation of joint kinetics.

Ground reaction force estimation using an insole-type pressure mat and joint kinematics during walking.

Kinetic analysis of walking requires joint kinematics and ground reaction force (GRF) measurement, which are typically obtained from a force plate. GRF is difficult to measure in certain cases such as slope walking, stair climbing, and track running. Nevertheless, estimating GRF continues to be of great interest for simulating human walking. The purpose of the study was to develop reaction force models placed on the sole of the foot to estimate full GRF when only joint kinematics are provided (Type-I), and to estimate ground contact shear forces when both joint kinematics and foot pressure are provided (Type-II and Type-II-val). The GRF estimation models were attached to a commercial full body skeletal model using the AnyBody Modeling System, which has an inverse dynamics-based optimization solver. The anterior-posterior shear force and medial-lateral shear force could be estimated with approximate accuracies of 6% BW and 2% BW in all three methods, respectively. Vertical force could be estimated in the Type-I model with an accuracy of 13.75% BW. The accuracy of the force estimation was the highest during the mid-single-stance period with an average RMS for errors of 3.10% BW, 1.48% BW, and 7.48% BW for anterior-posterior force, medial-lateral force, and vertical force, respectively. The proposed GRF estimation models could predict full and partial GRF with high accuracy. The design of the contact elements of the proposed model should make it applicable to various activities where installation of a force measurement system is difficult, including track running and treadmill walking.

Physical activity in adolescence has a positive effect on bone mineral density in young men.

OBJECTIVES: Little is yet known about the determinants of bone mineral density (BMD) in young adults. Thus, in this study, we aimed to determine the factors that have an impact on BMD in young men. METHODS: Questionnaires were sent out to 111 male medical students. Information on age, socio-economic status, medical history, lifestyle, physical activity during adolescence, school club participation, current physical activity, and dietary intake were collected by the survey. Height, weight, percent body fat and muscle mass were estimated by bioelectrical impedance, and BMD was obtained using calcaneal quantitative ultrasound. Using the Poisson regression model, prevalence ratios (PRs) were used to estimate the degree of association between risk factors and osteopenia. RESULTS: The height and current physical activity showed a correlation to the Osteoporosis Index. Among the categorized variables, past physical activity during adolescence (p=0.002) showed a positive effect on the bone mineral content. In the multivariate model, past physical activity (≥1 time/wk) had a protective effect on osteopenia (PR, 0.37; 95% confidence interval [CI], 0.18 to 0.75) and present physical activity (1000 metabolic equivalent of task-min/wk) decreased the risk of osteopenia (PR, 0.64; 95% CI, 0.44 to 0.91). CONCLUSIONS: Past physical activity during adolescence is as important as physical activity in the present for BMD in young men.

Prevalence of Barrett's esophagus in Korea.

BACKGROUND: In contrast to Western countries, the prevalence of Barrett's esophagus (BE) is still believed to be very low in the Far East. The aim of the present paper was to assess the prevalence of BE in Korea. METHODS: Nine hundred and ninety-two consecutive patients undergoing their first diagnostic upper gastrointestinal endoscopies due to various indications were included from four university hospitals in Korea. Esophagus of each patient was examined during insertion of the endoscope with minimum air inflation. From subjects who were found, during endoscopy, to have columnar-lined esophagus, at least two biopsy samples were taken from the columnar epithelium. Patients exhibiting specialized columnar epithelium on histological examination were diagnosed as having BE. RESULTS: Among 992 patients, 108 cases (10.9%) were endoscopically diagnosed as short-segment BE, and three cases (0.3%) were endoscopically diagnosed as long-segment BE. However, only 36 patients (3.6%) met the histological criteria for BE. Among these patients, only one (0.1%) was histologically diagnosed as having long-segment BE. Reflux esophagitis, mostly in a mild degree, was found in 25.0% of the BE group, and 8.6% of the non-BE group (P = 0.0022). Hiatal hernias were more commonly found in the BE group than in the non-BE group (22.2% vs 8.9%, P = 0.0163). CONCLUSIONS: Although the prevalence of BE in Korea appears to be lower than the reported rates from Western countries, it may not be as low as was previously thought.