Anterior-posterior Direction Research Articles

Investigation of direction- and age-dependent prestretch in mouse cranial dura mater.

Cranial dura mater is a dense interwoven vascularized connective tissue that helps regulate neurocranial remodeling by responding to strains from the growing brain. Previous ex vivo experimentation has failed to account for the role of prestretch in the mechanical behavior of the dura. Here we aim to estimate the prestretch in mouse cranial dura mater and determine its dependency on direction and age. We performed transverse and longitudinal incisions in parietal dura excised from newborn (day 4) and mature (12weeks) mice and calculated the ex vivo normalized incision opening (measured width over length). Then, similar incisions were simulated under isotropic stretching within Abaqus/Standard. Finally, prestretch was estimated by comparing the ex vivo and in silico normalized openings. There were no significant differences between the neonatal and adult mice when comparing cuts in the same direction, but adult mice were found to have significantly greater stretch in the anterior-posterior direction than in the medial-lateral direction, while neonatal dura was essentially isotropic. Additionally, our simulations show that increasing curvature impacts the incision opening, indicating that flat in silico models may overestimate prestretch.

The sex effect on balance control while standing on vestibular-demanding tasks with/without vestibular simulations: implication for sensorimotor training for future space missions.

Background: Anatomical differences between sexes in the vestibular system have been reported. It has also been demonstrated that there is a sex difference in balance control while standing on vestibular-demanding tasks. In 2024, NASA expects to send the first female to the Moon. Therefore, to extend the current knowledge, this study attempted to examine whether different sexes respond differently to vestibular-disrupted and vestibular-demanding environments. Method: A total of fifteen males and fifteen females participated in this study. The vestibular function was quantified through different SOT conditions (SOT1: baseline; SOT5: vestibular demanding by standing with blindfolded and sway reference surface). The vestibular stimulation (VS) was applied either unilaterally or bilaterally to vestibular system to induce the sensory-conflicted and challenging tasks. Thus, a total of 6 conditions (2 SOT conditions X 3 VSs: no-VS, unilateral VS, and bilateral VS) were randomly given to these participants. Three approaches can be quantified the balance control: 1) the performance ratio (PR) of center of gravity trajectories (CoG), 2) the sample entropy measure (SampEn) of CoG, and 3) the total traveling distance of CoG. A mixed three-way repeated ANOVA measure was used to determine the interaction among the sex effect, the effect of SOT, and the effect of VS on balance control. Results: A significant sex effect on balance control was found in the PR of CoG in the anterior-posterior (AP) direction (p = 0.026) and in the SampEn of CoG in both AP and medial-lateral (ML) directions (p = 0.025, p < 0.001, respectively). Also, a significant interaction among the sex effect, the effect of SOT, and the effect of VS on balance control was observed in PR of CoG in the ML direction (p < 0.001), SampEn of CoG in the AP and ML directions (p = 0.002, p < 0.001, respectively), and a traveling distance in AP direction (p = 0.041). Conclusion: The findings in the present study clearly revealed the necessity to take sex effect into consideration while standing in vestibular-perturbed or/and vestibular demanding tasks. Also, the results in the present study could be a fundamental reference for future sensorimotor training.

Influence of Perturbation’s Type and Location on Treadmill Gait Regularity

Background: This study aimed to investigate how —external perturbations caused by a treadmill belt’s acceleration (Acc) and deceleration (Dec) during the Initial-Contact (Initial), Mid-Stance (Mid), and Pre-Swing (ToeOff) phases affect gait regularity in young adults. Methods: Twenty-one healthy young females walked on a treadmill in a virtual environment (Motek GRAIL), in which four unexpected perturbations were applied to the left belt at the Initial, Mid, and ToeOff stages. Sample entropy (SampEn) was calculated for the center of mass (CoM) displacements for six perturbation scenarios in three directions—anterior–posterior (AP), medial–lateral (ML), and vertical (vert)—with SampEn vector lengths (m) ranging from 2 to 10. Results: The CoM displacement exhibited its highest regularity (low SampEn values) in the AP and vert directions during Dec–ToeOff, across all m values. Similarly, this pattern was observed in the ML direction, but exclusively for m = 2 and 4. The least-regular CoM trajectories (high SampEn values) were for Dec–Mid in the AP direction, across all m values. This trend persisted in the ML direction only for m = 2 and 4. However, the most irregular CoM displacements in the ML direction occurred during Dec–ToeOff for the remaining m values. Vertical CoM displacements exhibited the highest irregularities during Dec–Initial for m ≥ 4. Conclusions: Evaluating the regularity of CoM displacements using SampEn can be a useful tool for assessing how gait perturbations are handled.

Reconstruction of recurrent shoulder dislocation with glenoid bone defect with 3D-printed titanium alloy pad: outcomes at 2-year minimum follow-up

BackgroundTo evaluate the outcome of shoulder arthroscopy-assisted implantation of three-dimensional (3D)-printed titanium pads for recurrent shoulder dislocation with glenoid bone defects.MethodsFrom June 2019 to May 2020, the clinical efficacy of 3D printed titanium pad implantation assisted by shoulder arthroscopy, for the treatment of recurrent shoulder dislocations with shoulder glenoid defects was retrospectively analyzed. The American Shoulder and Elbow Surgeons (ASES) shoulder, Rowe, and Constant scores were recorded before surgery and at 3 months, 6 months, 1 year, and 2 years after surgery. 3D computed tomography (CT) and magnetic resonance imaging were used to evaluate the location of the glenoid pad, bone ingrowth, joint degeneration, and osteochondral damage.ResultsThe mean age of the 12 patients was 21.4 (19–24) years and the mean follow-up time was 27.6 (24–35) months. The Visual Analog Scale score significantly improved from 5.67 ± 1.98 preoperatively to 0.83 ± 0.58 postoperatively (p = 0.012). The postoperative ASES score was significantly increased to 87.91 ± 3.47 compared with preoperative ASES score (46.79 ± 6.45) (p < 0.01). Rowe and Constant scores also improved from 22.5 ± 12.34 and 56.58 ± 7.59 preoperatively to 90.83 ± 4.69 and 90.17 ± 1.89 at 2 years postoperatively, respectively. CT performed 2 years after surgery showed that the pad perfectly replenished the bone-defective part of the shoulder glenoid and restored the articular surface curvature of the shoulder glenoid in the anterior-posterior direction, and the bone around the central riser of the pad was tightly united. Magnetic resonance imaging 2 years after surgery showed that the humeral head osteochondral bone was intact, and there was no obvious osteochondral damage.Conclusions3D printed titanium pads are a reliable, safe, and effective surgical procedure for treating recurrent shoulder dislocations with glenoid bone defects.

Effects of arousal and valence on center of pressure and ankle muscle activity during quiet standing.

Emotion affects postural control during quiet standing. Emotional states can be defined as two-dimensional models comprising valence (pleasant/unpleasant) and arousal (aroused/calm). Most previous studies have investigated the effects of valence on postural control without considering arousal. In addition, studies have focused on the center of pressure (COP) trajectory to examine emotional effects on the quiet standing control; however, the relationship between neuromuscular mechanisms and the emotionally affected quiet standing control is largely unknown. This study aimed to investigate the effects of arousal and valence on the COP trajectory and ankle muscle activity during quiet standing. Twenty-two participants were instructed to stand on a force platform and look at affective pictures for 72 seconds. The tasks were repeated six times, according to the picture conditions composed of arousal (High and Low) and valence (Pleasant, Neutral, and Unpleasant). During the task, the COP, electromyogram (EMG) of the tibialis anterior and soleus muscles, and electrocardiogram (ECG) were recorded. The heart rate calculated from the ECG was significantly affected by valence; the value was lower in Unpleasant than that in Neutral and Pleasant. The 95% confidence ellipse area and standard deviation of COP in the anterior-posterior direction were lower, and the mean power frequency of COP in the anterior-posterior direction was higher in Unpleasant than in Pleasant. Although the mean velocity of the COP in the medio-lateral direction was significantly lower in Unpleasant than in Pleasant, the effect was observed only when arousal was low. Although the EMG variables were not significantly affected by emotional conditions, some EMG variables were significantly correlated with the COP variables that were affected by emotional conditions. Therefore, ankle muscle activity may be partially associated with postural changes triggered by emotional intervention. In conclusion, both valence and arousal affect the COP variables, and ankle muscle activity may be partially associated with these COP changes.

Effects of Stroboscopic Goggles on Standing Balance in the Spatiotemporal and Frequency Domains: An Exploratory Study.

Balance training paradigms have been shown to effectively reduce fall risk. Visual feedback is an important sensory mechanism for regulating postural control, promoting visual perturbations for balance training paradigms. Stroboscopic goggles, which oscillate from transparent to opaque, are a form of visual perturbation, but their effect on standing balance has not been assessed. In this study, 29 participants stood in bilateral and tandem stances as the center of pressure was recorded for 6 consecutive minutes wherein there were no stroboscopic perturbations in the first and last minutes. Spatial-temporal, frequency domain, and nonlinear standing balance parameters were calculated for each period. More differences in spatial-temporal parameters due to the strobe were found in the medial-lateral direction than the anterior-posterior direction. More differences in frequency domain parameters were observed in the anterior-posterior direction than the medial-lateral direction, but this did not occur for each variable. The nonlinear parameters were strongly affected by the strobe. Stroboscopic perturbations did not affect the bilateral and tandem stances equally. Spatial-temporal parameters for the tandem stance were greater in magnitude during the strobe period than the no strobe periods. This effect was not seen with the bilateral stance. This indicates that the efficacy of stroboscopic perturbations for challenging standing balance depends on task difficulty. Balance training paradigms that utilize stroboscopic perturbations will need to harmonize these perturbations with task difficulty.

Comparing the Effects of 8-week Exercise Programs in the Sagittal and Frontal Planes on the Postural Sway of Elderly Men

Background and Aims Exercises are mostly used to control balance and reduce the risk of falling in the elderly. However, the effect of exercise in the frontal plane has been less studied. Therefore, this study aims to compare the effect of 8 week exercises in the sagittal and frontal planes on the postural sway of elderly men. Methods In this quasi-experimental study, 24 elderly males (Mean age: 67.21±1.56 years) were divided into two intervention groups of sagittal-plane and frontal-plane exercises. The exercises were performed for 8 weeks. The center of pressure (CoP) parameters in two groups before and after the intervention were evaluated using a foot scanner system. Finally, the ANCOVA was used for data analysis. P≤0.05 was considered statistically significant. Results The results showed a significant decrease in CoP perturbations in the Y-axis at the medial-lateral, anterior-posterior, and lateral-medial directions in the frontal plane group compared to the sagittal group (P&lt;0.05). Moreover, there was a significant decrease in the CoP area after perturbations at the medial-lateral, anterior-posterior, and lateral-medial directions in the frontal group compared to the sagittal group (P&lt;0.05). Conclusion It seems that exercises in the frontal plane can reduce postural sway in elderly men compared to sagittal-plane exercises. Therefore, it is recommended to emphasize the exercises of the hip abductor and adductor muscles in the frontal plane in designing exercise protocols for elderly men.

Assessing the Impact of a 1.5 T Transverse Magnetic Field in Radiotherapy for Esophageal Cancer Patients.

Purpose: Magnetic resonance (MR)-guided radiotherapy enables visualization of static anatomy, capturing tumor motion, and extracting quantitative image features for treatment verification and outcome monitoring. However, magnetic fields in online MR imaging (MRI) require efforts to ensure accurate dose measurements. This study aimed to assess the dosimetric impact of a 1.5 T magnetic field in esophageal cancer radiotherapy using MR-linac, exploring treatment adaptation potential and personalized medicine benefits. Methods: A prospective cohort study enrolled 100 esophageal squamous cell carcinoma patients undergoing 4DCT and 3DCT scans before radiotherapy. The heart was contoured on 3DCT, 4DCT end expiration (EE), and 4DCT end inhalation (EI) images by the same radiation oncologist. Reference RT plans were designed on 3DCT, with adjustments for different phases generating 5 plan types per patient. Variations in dose-volume parameters for organs at risk and the target area among different plans were compared using Monaco 5.40.04. Results: Slight dose distortions at air-tissue interfaces were observed in the magnetic field's presence. Dose at air-tissue interfaces (chest wall and heart wall) was slightly higher in some patients (3.0% tissue increased by 4.3 Gy on average) compared to nonmagnetic conditions. Average clinical target volume coverage V100 dropped from 99% to 95% compared to reference plans (planEI and planEE). Dose-volume histogram variation between the original plan and reference plans was within 2.3%. Superior-inferior (SI) direction displacement was significantly larger than lateral and anterior-posterior directions (P < .05). Conclusion: Significant SI direction shift in lower esophageal cancerous regions during RT indicates the magnetic field's dosimetric impact, including the electron return effect at tissue-air boundaries. Changes in OAR dose could serve as valuable indicators of organ impairment and target dose alterations, especially for cardiac tissue when using the 1.5 T linac method. Reoptimizing the plan with the magnetic field enhances the feasibility of achieving a clinically acceptable treatment plan for esophageal cancer patients.

The Neuromuscular Parameters Affecting Static and Dynamic Balance in Adolescent Male Soccer Players with Dynamic Knee Valgus

Background and Aims The anterior cruciate ligament injury in athletes is associated with disorders related to balance and postural control. Poor balance is a predictor of lower limb injury in athletes. This study aims to investigate the different neuromuscular parameters that affect the static and dynamic balance in adolescent male football players with Dynamic Knee Valgus (DKV). Methods This is a correlational study. Participants were 83 adolescent male football players with DKV (age: 12.63±0.72 years, height: 1.69±0.07 meters, weight: 23.23±7.74 58 kg, BMI: 20.32±2.38 kg /m2), who were selected using a purposive sampling method. The presence of DKV was assessed by the squat test. The strength of the trunk and hip muscles was assessed by manual muscle testing (MMT), trunk endurance by the McGill test, and range of motion (ROM) of hip and ankle joints by a goniometer. Moreover, the static and dynamic balances were evaluated by the Bass Stick test and Y balance test, respectively. The Pearson correlation test was used to examine the relationships at a significance level of 0.05. All statistical operations were performed by SPSS software, version 24. Results The results of the present study showed a significant relationship between static balance and the study parameters (P≤0.05) except for trunk flexion strength (P=0.16) and ROM (P&lt;0.05), hip flexion ROM (P=0.83), hip extension ROM (P=0.96), hip abduction ROM (P=0.77) and ankle dorsiflexion ROM (P=0.94). The dynamic balance at anterior-posterior direction had a significant relationship with trunk endurance and left-side plank (P=0.07) and strength (P=0.05), but not with plank test score (P=0.45). The dynamic Y balance at posteromedial direction had a significant relationship with all variables except for 60° flexion (P=0.40), plank (P=0.53), left-side plank (P=0.09), and trunk extension strength (P=0.23). The results of the study also showed the significant relationship of dynamic balance at posterolateral direction and the total score of Y balance test with total trunk endurance test score (P=0.03, P=0.003) and right-side plank (P=0.005, P=0.001). Moreover, trunk extension strength and hip strength variables had a significant relationship with posterolateral dynamic balance and total Y balance test score (P≤0.05). Furthermore, the ROM of ankle dorsiflexion had a significant relationship with balance at the posteromedial (P=0.03), posterolateral (P=0.02) directions and the total Y balance score (P=0.02). Conclusion Static balance of adolescent male soccer players with DKV has a significant relationship with trunk endurance, trunk strength and thigh strength. There is a significant relationship between dynamic balance and trunk endurance, trunk strength, hip strength, and ankle dorsiflexion ROM.

A Comparison of Tumor Respiratory Motion Evaluation Methods Using Dynamic Thorax Motion Phantom

We evaluated the measurement accuracy and time efficiency of the tumor respiratory motion evaluation methods using a dynamic thorax motion phantom. A total of 12 patterns of 4DCT images with different tumor displacements and artifacts were used for the measurement. Three methods were employed to measure tumor motion. The first method was the manual delineation of the tumor on each phase CT image with a treatment planning system (RTPS [Manual]). The second method was the automatic delineation of the tumor structure by deformation and copying (RTPS [Auto]). The third method was tumor motion analysis software (Simple 4D Analysis Ver.1.3.1 [Simple 4D]; Triangle Products, Chiba, Japan). For each method, the difference between the phantom motion and the measured value was determined. The differences (mean±standard deviation: SD) in the superior-inferior direction for RTPS (Manual), RTPS (Auto), and Simple 4D in the without-artifact images were -0.6 mm±0.6 mm, -5.0 mm±2.2 mm, and -1.0 mm±0.0 mm, respectively. The difference in the left-right and anterior-posterior directions was within 1 mm for all methods. Furthermore, the time required for Simple 4D was shorter than for the other methods. Simple 4D showed the comparable measurement accuracy and improvement time efficiency to RTPS (Manual) and RTPS (Auto), and was useful for tumor respiratory motion analysis.

Accelerometer-based fall risk prediction in elderly using machine learning: Effect of feature combination and balanced dataset

Frequent falls among the elderly pose a significant risk to their health and well-being. Predicting fall risks using sensor technology plays a crucial role in managing and preventing such incidents. This study employed accelerometers and machine learning models to assess fall risk in a dataset comprising high-risk and low-risk older adults. The impact of balanced and imbalanced datasets and feature data combined with demographic data was examined. Results show that the optimal model was Random Forest which attained 0.98 AUC, using the 10 best features obtained from the accelerometer combined with demographic data and without applying Principal Components Analysis (PCA) to the dataset. The results also emphasize the importance of data balancing and the vertical axis and anterior-posterior axis directions in evaluating fall risks. Our findings suggests the potential of implementing the fall prediction model to aid in the care and prevention of falls in elderly.

The impact of external perturbations on postural control

Purpose External factors can disrupt postural control, but the intricate workings of the postural control system enable an appropriate response. This study seeks to assess how external perturbations affect postural control. Methods Twenty women participated in study, which consisted four trials involved quiet standing and experiencing induced perturbations by being struck with a boxing bag from the back, right, and left sides, respectively. The center of pressure (CoP) path length was recorded for each of the mentioned trials. Sample Entropy (SampEn), Lyapunov Exponent (LyE), and Fractal Dimension (FD) were computed for the CoP time series, separately for the anterior-posterior (AP) and mediolateral (ML) directions. The nonparametric Friedman ANOVA with Dunn-Bonferroni post-hoc analysis was employed to investigate the influence of external perturbations on both linear and nonlinear parameters on postural control. Results The post-hoc analysis showed for LyE_AP_quiet (1.02 ± 0.18) significantly higher values than for LyE_AP_right (0.92 ± 0.22) and significantly higher for LyE_AP_left. Lyapunov Exponent was the parameter that differentiated the most between samples. Conclusions The greatest number of significant differences between samples were demonstrated by the Lyapunov Exponent. This nonlinear parameter should be used to evaluate various perturbations during upright position in healthy subjects.

Comparison of the Effects of Cognitive Dual-Task and Single-Task Balance Exercises on Static Balance among People with Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial.

The anterior cruciate ligament (ACL) reconstruction surgery improves mechanical stability; however, functional stability remains impaired. Balance exercises can help improve functional stability. The effect of cognitive dual-task balance exercises has not been studied in people with ACL reconstruction surgery; therefore, this study aimed to compare the effect of cognitive dual-task and single-task balance exercises on the static balance indices in these individuals. This study was a randomized clinical trial. After a period of conventional physiotherapy and applying inclusion criteria, 28 patients with ACL reconstruction surgery were randomly divided into two groups of cognitive dual-task and single-task balance exercises. Each group received the relevant exercises for four weeks, three times a week, with each session lasting 20 min. Center of pressure variables, including mean displacement in anterior-posterior and medial-lateral directions, total path length, mean velocity of displacement, root mean square of displacement and velocity, and the elliptical area, were measured using the FDM pressure platform before and after the interventions as the primary outcomes. Knee Injury and Osteoarthritis Outcome Score (KOOS) scale was completed by the participants before and after the interventions. The measured static balance variables and KOOS subscales had significant differences before and after intervention in both groups (P<0.05); however, no statistically significant difference was observed in these variables between the two groups. There was no significant correlation between KOOS subscales and measured static balance variables. Both cognitive dual-task and single-task balance exercises improved the indicators related to static balance and the level of functional disability of the knee. However, cognitive dual-task balance exercises had no superiority over single-task balance exercises in ACL-reconstructed individuals.

Medial Meniscus Posterior Root Tears Lead to Changes in Joint Contact Mechanics at Low Flexion Angles During Simulated Gait

Background: Previous biomechanical studies evaluating medial meniscus posterior root tears (MMPRTs) are limited to low loads applied at specified loading angles, which cannot capture the effects of MMPRTs during the multidirectional forces and moments placed across the knee during physiological activities. Purpose: To quantify the effects of MMPRTs on knee joint contact mechanics during simulated gait. Study Design: Controlled laboratory study. Methods: Six human cadaveric knees were mounted on a robotic simulator programmed to apply dynamic forces, moments, and flexion angles to mimic level walking. Twelve cycles of multidirectional and dynamic standard gait input waveforms, normalized to specimen-specific body weight, were applied to the following conditions: (1) native, intact meniscus and (2) MMPRT. Peak contact stress, contact area, and the position of the weighted center of contact across the medial tibial plateau throughout the stance phase of gait were quantified using an electronic sensor placed across the medial tibial plateau. The difference between the intact state and MMPRT condition was calculated for each metric, and then the means and 95% CIs were computed. Results: Despite heterogeneity in knee contact forces, MMPRTs significantly increased peak contact stress by a mean of 2 MPa across 20% to 37% of the simulated gait cycle and significantly decreased the contact area by a mean of 200 mm2 across 16% to 60% of the simulated gait cycle in comparison with the native state. There was no significant difference in the position of the weighted center of contact, in either the anterior-posterior or medial-lateral directions, after MMPRT. Conclusion: MMPRTs led to both a significant increase in peak contact stress and decreased contact areas for a portion of the simulated gait cycle ranging from 20% to 37% of gait, during which time the femur was flexed <15°. Clinical Relevance: Contact mechanics are significantly affected after MMPRTs during early to midstance and at knee flexion angles lower than demonstrated previously. These data provide further biomechanical justification for treating MMPRTs.

Impact of Injury Prevention Video Feedback on Biomechanical Variables of the Knee Joint during Cutting Maneuver

PURPOSE This study aims to analyze the effects of injury prevention video feedback on kinetic variables of the knee joint during the cutting maneuver.METHODS Twenty-eight healthy men participated and motion and force data were collected using infrared cameras, a force plate, and a Witty timing system. Paired t-tests were employed for data evaluation using the SPSS 26.0 program.RESULTS Results showed increased abduction and lateral rotation angles of the knee joint at the lower height of the center of mass (COM) (p&lt;. 05). The lateral rotation of the knee joint decreased at initial ground contact (p&lt;.05). Flexion angular velocity increased at initial ground contact after video feedback (p&lt;.05) and decreased at the lower height of COM (p&lt;.05). Abduction angular velocity decreased at the lower height of COM (p&lt;.05), and internal rotation angular velocity was increased on the initial ground contact (p&lt;.05). Maximum ground reaction force for anterior-posterior and medial-lateral directions increased after video feedback (p&lt;.05). Flexion and internal rotation moments increased, and adduction moment also increased (p&lt;.05).CONCLUSIONS In conclusion , video feedback effectively reduced knee load during the cutting maneuver, contributing to injury prevention for the knee joint.

Evaluation of Resultant Ground Reaction Force and Its Velocity Using the Elapsed Time and Peak Reaction Force at 3-Dimensional Direction During Landing Task

The purpose of this study was to analyze the effects of bilateral landing leg and sex on resultant ground reaction force (GRF) and its velocity, using peak vertical GRF and elapsed time during drop landing tasks. A repeated-measures two-way analysis of variance explored the impact of landing legs and sex on the resultant vector, three-dimensional GRF, elapsed time, and velocity in 40 participants (20 males and 20 females). Participants performed drop landings from a 35-cm box. Effects of sex and landing leg were analyzed using a repeated-measures model (two sexes × two legs) on GRF magnitude and velocity. Females displayed shorter elapsed times to peak GRF compared to males in the anterior-posterior and vertical directions. Significant differences emerged between sexes in both magnitude and velocity of resultant and peak vertical GRF, with females exhibiting higher values. This suggests the adoption of distinct landing strategies between sexes. Notably, no significant differences were found in GRF magnitude or velocity between bilateral leg landings. These results indicate that healthy individuals of both sexes utilize different landing strategies during drop landings. This knowledge has potential applications in clinical settings for evaluating impulse force and stress transfer to the musculoskeletal system during landing tasks.

Postural control of prolonged standing in people with Parkinson's disease

People with Parkinson's disease (pwPD) have reduced adaptability to postural control during prolonged standing compared to neurologically healthy individuals (control). Objective. The study aimed to characterize postural changes during prolonged standing and their effect on postural control in pwPD compared to control. We recorded the body sway of the second lumbar vertebra of 23 pwPD and 23 control while they performed prolonged standing (15 min). The number and amplitude of the body sway patterns (shifts, fidgets, and drifts), the root mean square, velocity, and frequency of the body sway were analyzed. The number of shifts in the anterior-posterior (AP) and medial-lateral (ML) directions was greater for the pwPD than the control. In addition, the amplitudes of shifts in the AP direction and fidgets in the AP and ML directions were greater for the pwPD than the control. Our results show that: (1) A larger number of shifts of body sway suggest references positions are frequently changing; (2) Fidgets is a pumping mechanism and can be sensory-demand action to restore mechanoreceptors activity on the foot sole; and (3) No drift changes may suggest there is no slow migration of reference position. We conclude that pwPD exhibits different behavior than healthy ones during prolonged standing, suggesting that prolonged standing could distinguish individuals with Parkinson's disease.

A Comparison of Dynamic Gait Stability between the Young and Elderly Female Populations Using the Zero-Moment Point Method

A compromised stability in the elderly population is considered a major factor for fall risk assessment. The dynamic stability of human gait with various mathematical metrics has been extensively studied to find a prediction index and fall prevention strategies that can be embedded in a wearable monitoring sensor. In this study, the zero-moment point method (ZMP) was utilized for analyzing the gait stability of young and elderly female populations. Participants in the young and elderly female groups with no musculoskeletal disorders and fall experience were asked to walk at a habitual speed on 10 m flat ground. Dynamic instability is defined by the percentage of the ZMP values that fall outside the base of support during one gait cycle. The ZMP trajectory between the left and right leg swing was not symmetrical considering flat-ground walking. Also, there was no statistical difference in the dynamic stability in the anterior–posterior direction (71.3 ± 7.9% for the young group and 73.6 ± 7.6% for the elderly group), but walking in the medial–lateral direction was more stable in the elderly group (53.9 ± 8.6%) than in the young group (44.1 ± 11.2%) because the habitual walking speed decreased in the elderly group.

Characterizing cardiac contractile motion for noninvasive radioablation of ventricular tachycardia

BackgroundRespiratory motion management strategies are used to minimize the effects of breathing on the precision of stereotactic ablative radiotherapy for ventricular tachycardia, but the extent of cardiac contractile motion of the human heart has not been systematically explored. ObjectiveWe aim to assess the magnitude of cardiac contractile motion between different directions and locations in the heart. MethodsPatients with intracardiac leads or valves who underwent 4D cardiac computed tomography (4DCT) prior to a catheter ablation procedure for atrial or ventricular arrhythmias at 2 medical centers were studied retrospectively. The displacement of transvenous right atrial appendage (RA), right ventricle (RV) ICD, coronary sinus (CS) lead tips and prosthetic cardiac devices across the cardiac cycle were measured in orthogonal 3D views on a maximal-intensity projection CT reconstruction. ResultsA total of 31 pre-ablation cardiac 4DCTs were analyzed. The LV lead tip had significantly greater motion compared to the RV lead in the anterior-posterior direction (6.0±2.2mm vs 3.8±1.7mm; p=0.01) and superior-inferior direction (4.4±2.9mm vs 3.5±2.0mm; p=0.049). The prosthetic aortic valves had the least movement of all fiducials, specifically compared to the RV lead tip in the left-right direction (3.2±1.2mm vs 6.1±3.8mm, p=0.04) and the LV lead tip in the antero-posterior direction (3.8±1.7mm vs 6.0±2.2mm, p=0.03). ConclusionThe degree of cardiac contractile motion varies significantly (1mm to 15.2 mm) across different locations in the heart. The effect of contractile motion on the precision of radiotherapy should be assessed on a patient-specific basis.

Optimal planning target margin for prostate radiotherapy based on interfractional and intrafractional variability assessment during 1.5T MRI-guided radiotherapy.

We analyzed daily pre-treatment- (PRE) and real-time motion monitoring- (MM) MRI scans of patients receiving definitive prostate radiotherapy (RT) with 1.5 T MRI guidance to assess interfractional and intrafractional variability of the prostate and suggest optimal planning target volume (PTV) margin. Rigid registration between PRE-MRI and planning CT images based on the pelvic bone and prostate anatomy were performed. Interfractional setup margin (SM) and interobserver variability (IO) were assessed by comparing the centroid values of prostate contours delineated on PRE-MRIs. MM-MRIs were used for internal margin (IM) assessment, and PTV margin was calculated using the van Herk formula. We delineated 400 prostate contours on PRE-MRI images. SM was 0.57 ± 0.42, 2.45 ± 1.98, and 2.28 ± 2.08 mm in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions, respectively, after bone localization and 0.76 ± 0.57, 1.89 ± 1.60, and 2.02 ± 1.79 mm in the LR, AP, and SI directions, respectively, after prostate localization. IO was 1.06 ± 0.58, 2.32 ± 1.08, and 3.30 ± 1.85 mm in the LR, AP, and SI directions, respectively, after bone localization and 1.11 ± 0.55, 2.13 ± 1.07, and 3.53 ± 1.65 mm in the LR, AP, and SI directions, respectively, after prostate localization. Average IM was 2.12 ± 0.86, 2.24 ± 1.07, and 2.84 ± 0.88 mm in the LR, AP, and SI directions, respectively. Calculated PTV margin was 2.21, 5.16, and 5.40 mm in the LR, AP, and SI directions, respectively. Movements in the SI direction were the largest source of variability in definitive prostate RT, and interobserver variability was a non-negligible source of margin. The optimal PTV margin should also consider the internal margin.