The relationship between knee flexion excursion and mechanical stress during gait in medial knee osteoarthritis.

BACKGROUND: A decrease in knee flexion excursion during the loading response may affect not only quadriceps muscle weakness, pain, and inflammatory symptoms, but also lead to physical function decline and activity limitation. The aim of this investigation was to clarify the relationship between knee flexion excursion during the loading response and mechanical stress on the knee joint, muscle strength, pain, and physical function in patients with knee osteoarthritis. METHODS: Twenty patients diagnosed with medial knee osteoarthritis. The participants walked along a 10 m corridor in the laboratory at a comfortable pace. The kinematic and kinetic data were collected using a 3D motion analysis system. We employed to control for gait speed and age while examining the relationship between knee flexion excursion during the loading response and mechanical stress on the knee joint, muscle strength, pain, and physical function. FINDINGS: Knee flexion excursion showed a significant positive correlation with the peak and angular impulse of knee flexion moment. In the partial correlation coefficients controlling for age and gait speed, significant negative correlations were found between knee flexion excursion and knee adduction moment angular impulse. INTERPRETATION: It can be inferred that gait with reduced knee flexion movement during the loading response in patients with knee osteoarthritis may result in increased mechanical stress on the knee joint in the frontal plane. Exercise interventions aimed at increasing knee flexion excursion may result in a reduction in disease progression.

Impact of secondary electron emission noise in SEM.

In semiconductor-device inspection using scanning electron microscopes (SEMs), the irradiation dose of the electron beam becomes lower because of increasing needs for higher throughput and lower damage to the samples. Therefore, it is necessary to form images using fewer primary electrons, making noise reduction of SEM images one of the main challenges. We have modeled the imaging process of SEMs, which consists of the generation of primary, secondary and tertiary electrons (PEs, SEs and TEs, respectively), and detection. Furthermore, a method to accurately evaluate the fluctuation in the number of SEs and TEs are proposed. We found that SEM-image noise can be minimized by directly detecting SEs generated in the sample, in which case the fluctuation in the number of SEs determines the image quality. The variance number of SEs emitted from a 500-eV PE irradiation onto a Si wafer is 1.9 times as large as the value derived assuming a Poisson process. A Monte-Carlo simulation result was used to explain the experimental results and predict that PE energy less than 1 keV suppresses the fluctuation in the number of SEs, and consequently, the SEM-image noise level. These findings provide a method for determining imaging conditions that improve the throughput of SEMs.

Relationships Between Trunk Movement Patterns During Lifting Tasks Compared With Unloaded Extension From a Flexed Posture.

OBJECTIVES: The purpose of this study was to investigate between movement patterns of trunk extension from full unloaded flexion and lifting techniques, which could provide valuable information to physical therapists, doctors of chiropractic, and other manual therapists. METHODS: A within-participant study design was used. Whole-body kinematic and kinetic data during lifting and full trunk flexion were collected from 16 healthy male participants using a 3-dimensional motion analysis system (Vicon Motion Systems). To evaluate the relationships of joint movement between lifting and full trunk flexion, Pearson correlation coefficients were calculated. RESULTS: There was no significant correlation between the amount of change in the lumbar extension angle during the first half of the lifting trials and lumbar movement during unloaded trunk flexion and extension. However, the amount of change in the lumbar extension angle during lifting was significantly negatively correlated with hip movement during unloaded trunk flexion and extension (P < .05). CONCLUSIONS: The findings that the maximum hip flexion angle during full trunk flexion had a greater influence on kinematics of lumbar-hip complex during lifting provides new insight into human movement during lifting. All study participants were healthy men; thus, findings are limited to this group.

Biomechanical mechanism of lateral trunk lean gait for knee osteoarthritis patients.

The biomechanical mechanism of lateral trunk lean gait employed to reduce external knee adduction moment (KAM) for knee osteoarthritis (OA) patients is not well known. This mechanism may relate to the center of mass (COM) motion. Moreover, lateral trunk lean gait may affect motor control of the COM displacement. Uncontrolled manifold (UCM) analysis is an evaluation index used to understand motor control and variability of the motor task. Here we aimed to clarify the biomechanical mechanism to reduce KAM during lateral trunk lean gait and how motor variability controls the COM displacement. Twenty knee OA patients walked under two conditions: normal and lateral trunk lean gait conditions. UCM analysis was performed with respect to the COM displacement in the frontal plane. We also determined how the variability is structured with regards to the COM displacement as a performance variable. The peak KAM under lateral trunk lean gait was lower than that under normal gait. The reduced peak KAM observed was accompanied by medially shifted knee joint center, shortened distance of the center of pressure to knee joint center, and shortened distance of the knee-ground reaction force lever arm during the stance phase. Knee OA patients with lateral trunk lean gait could maintain kinematic synergy by utilizing greater segmental configuration variance to the performance variable. However, the COM displacement variability of lateral trunk lean gait was larger than that of normal gait. Our findings may provide clinical insights to effectively evaluate and prescribe gait modification training for knee OA patients.

Trunk lean gait decreases multi-segmental coordination in the vertical direction.

[Purpose] The strategy of trunk lean gait to reduce external knee adduction moment (KAM) may affect multi-segmental synergy control of center of mass (COM) displacement. Uncontrolled manifold (UCM) analysis is an evaluation index to understand motor variability. The purpose of this study was to investigate how motor variability is affected by using UCM analysis on adjustment of the trunk lean angle. [Subjects and Methods] Fifteen healthy young adults walked at their preferred speed under two conditions: normal and trunk lean gait. UCM analysis was performed with respect to the COM displacement during the stance phase. The KAM data were analyzed at the points of the first KAM peak during the stance phase. [Results] The KAM during trunk lean gait was smaller than during normal gait. Despite a greater segmental configuration variance with respect to mediolateral COM displacement during trunk lean gait, the synergy index was not significantly different between the two conditions. The synergy index with respect to vertical COM displacement during trunk lean gait was smaller than that during normal gait. [Conclusion] These results suggest that trunk lean gait is effective in reducing KAM; however, it may decrease multi-segmental movement coordination of COM control in the vertical direction.

Lower limb kinematics during the swing phase in patients with knee osteoarthritis measured using an inertial sensor.

BACKGROUND: During gait, the swing limb requires flexible control to adapt to ever changing environmental circumstances. However, few studies have focused on the mechanics of swing limb control in patients with knee osteoarthritis (OA). Investigating the variability of swing limb kinematics, which can be represented by variables such as the peak shank angular velocity during the swing phase obtained from an inertial sensor, provides insights into the adaptability of swing limb control. The purpose of this study was to investigate how patients with knee OA control the swing limb and whether the degree of impairment and disability due to knee OA affects swing limb control. METHODS: Twelve subjects diagnosed with knee OA and 11 healthy control subjects participated in this study. Subjects walked on a treadmill for 10min. The mean, coefficient of variation, and fractal scaling exponent α of the peak shank angular velocity during the swing phase were calculated. FINDINGS: There were no significant differences between the groups for any of the kinematic parameters. The Knee Injury and Osteoarthritis Outcome Score (KOOS) activities of daily living (ADL) subsection correlated with the coefficient of variation (r=-0.677, p=0.016) and the scaling exponent α (r=0.604, p=0.037) of the peak shank angular velocity. INTERPRETATION: Control of the swing limb was associated with the degree of impairment and disability. Larger and more random variability of peak shank angular velocity may indicate decreased ADL ability in patients with knee OA.

Rear foot kinematics when wearing lateral wedge insoles and foot alignment influence the effect of knee adduction moment for medial knee osteoarthritis.

Lateral wedge insoles (LWIs) are prescribed for patients with medial knee osteoarthritis to reduce the external knee adduction moment (KAM). However, the biomechanical effects of LWIs are limited in some patients. The purpose of this study was to investigate whether the biomechanical effects of LWIs depend on individual foot alignment and to examine the relationship between change in KAM and changes in foot and ankle biomechanics when wearing LWIs. Twenty-one patients participated in this study. They were categorized into normal or abnormal foot groups based on the foot posture index (FPI). All patients were requested to perform a normal gait under barefoot and LWI conditions. A three-dimensional motion analysis system was used to record 1st and 2nd KAM, knee adduction angular impulse (KAAI), center of pressure displacement, and knee-ground reaction force lever arm. Furthermore, the foot and ankle frontal plane kinematic parameters were evaluated. The 1st KAM was significantly reduced under the LWI condition compared to that under the barefoot condition in the normal foot group. In contrast, there was no significant difference in 1st KAM between both conditions in the abnormal foot group. Decreased rear foot eversion strongly correlated with reduction in the 1st KAM in the normal foot group. These findings suggested that it is helpful to assess individual foot alignment to ensure adequate insole treatment for patients with medial knee osteoarthritis and that decreased rear foot eversion during the early stance phase is significantly involved in the reduction of 1st KAM when wearing LWIs with normal feet.

The coordination of joint movements during sit-to-stand motion in old adults: the uncontrolled manifold analysis.

OBJECTIVE: Sit-to-stand motion (STS) is a dynamic motion utilized in fundamental activities of daily living and requires extensive joint movement in the lower extremities and the trunk and coordination of multiple body segments. The present study aimed to investigate whether aging affects the motor coordination of joint movements required to stabilize the horizontal and vertical movement of center of mass using the uncontrolled manifold (UCM) analysis. METHOD: We recruited 39 older adults with no musculoskeletal and/or neuromuscular conditions that affected STS, along with 21 healthy younger adults. All subjects performed five STS trials from a chair with the seat height adjusted to the length of their lower leg at a self-selected motion speed. Kinematic data were collected using a three-dimensional motion analysis system. We performed the UCM analysis to assess the effects of joint angle variance (elemental variable) to stabilize the horizontal and vertical movement of COM (performance variable) and calculated the joint angle variance that does not affect COM (VUCM), the variance that affects COM (VORT), and the synergy index (ΔV). RESULTS: ΔV values in the horizontal direction were higher in the older adults than in the younger adults, but ΔV values in the vertical direction were lower in the older adults than in the younger adults. CONCLUSION: Older adults require increasing levels of stabilization of horizontal movement of COM after buttocks-off in the STS maneuver. As a result, variance in the joint angle of the lower extremities indicated no kinematic synergy for stabilizing the vertical movement of COM.

Foot alignments influence the effect of knee adduction moment with lateral wedge insoles during gait.

Lateral wedge insoles (LWIs) reduce the peak external knee adduction moment (KAM). However, the efficacy of LWIs is limited in certain individuals for whom they fail to decrease KAM. Possible explanations for a lack of desired LWI response are variations in foot alignments. The purpose of this study was to evaluate whether the immediate biomechanical effects of LWIs depend on individual foot alignments during gait. Fifteen healthy adults participated in this study. Their feet were categorized as normal, pronated, and supinated using the foot posture index. All subjects were subsequently requested to perform a normal gait under barefoot and LWI conditions. A three-dimensional motion analysis system was used to record the kinematic and kinetic data, included peak KAM, KAM impulse (KAAI), center of pressure displacement, and knee-ground reaction force lever arm (KLA). Furthermore, lower limb frontal plane kinematic parameters at the rear foot, ankle, knee, and hip were evaluated. Among all feet, there was no significant difference in the peak KAM and KAAI between the conditions. In contrast, the peak KAM was significantly reduced under the LWI condition relative to the barefoot condition in the normal foot group. Reductions in the peak KAM were correlated with a more lateral center of pressure and reduced KLA. In addition, a reduced KLA was correlated with decreased hip adduction. LWIs significantly reduced the peak KAM in normal feet, indicating that biomechanical effects of LWIs vary between individual foot alignments. Our findings suggest that it is helpful to assess individual foot alignment to ensure adequate insole treatment for patients with knee osteoarthritis.

Influences of trunk flexion on mechanical energy flow in the lower extremities during gait.

[Purpose] The time-series waveforms of mechanical energy generation, absorption, and transfer through the joints indicate how movements are produced and controlled. Previous studies have used these waveforms to evaluate and describe the efficiency of human movements. The purpose of this study was to examine the influence of trunk flexion on mechanical energy flow in the lower extremities during gait. [Subjects and Methods] The subjects were 8 healthy young males (mean age, 21.8 ± 1.3 years, mean height, 170.5 ± 6.8 cm, and mean weight, 60.2 ± 6.8 kg). Subjects walked at a self-selected gait speed under 2 conditions: normal gait (condition N), and gait with trunk flexion formed with a brace to simulate spinal curvature (condition TF). The data collected from initial contact to the mid-stance of gait was analyzed. [Results] There were no significant differences between the 2 conditions in the mechanical energy flow in the knee joint and negative mechanical work in the knee joint. However, the positive mechanical work of the knee joint under condition TF was significantly less than that under condition N. [Conclusion] Trunk flexion led to knee flexion in a standing posture. Thus, a strategy of moving of center of mass upward by knee extension using less mechanical energy was selected during gait in the trunk flexed posture.

The effects of altering attentional demands of gait control on the variability of temporal and kinematic parameters.

The purpose of this study was to investigate the effects of cognitive and visuomotor tasks on gait control in terms of the magnitude and temporal structure of the variability in stride time and lower-limb kinematics measured using inertial sensors. Fourteen healthy young subjects walked on a treadmill for 15min at a self-selected gait speed in the three conditions: normal walking without a concurrent task; walking while performing a cognitive task; and walking while performing a visuomotor task. The time series data of stride time and peak shank angular velocity were generated from acceleration and angular velocity data recorded from both shanks. The mean, coefficient of variation, and fractal scaling exponent α of the time series of these variables and the standard deviation of shank angular velocity over the entire stride cycle were calculated. The cognitive task had an effect on long-range correlations in stride time but not on lower-limb kinematics. The temporal structure of variability in stride time became more random in the cognitive task. The visuomotor task had an effect on lower-limb kinematics. Subjects controlled their swing limb with greater variability and had a more complex adaptive lower-limb movement pattern in the visuomotor task. The effects of the dual tasks on gait control were different for stride time and lower-limb kinematics. These findings suggest that the temporal structure of variability and lower-limb kinematics are useful parameters to detect a change in gait pattern and provide further insight into gait control.

Biomechanical effects of lateral and medial wedge insoles on unilateral weight bearing.

[Purpose] Lateral wedge insoles reduce the peak external knee adduction moment and are advocated for patients with knee osteoarthritis. However, some patients demonstrate adverse biomechanical effects with treatment. In this study, we examined the immediate effects of lateral and medial wedge insoles under unilateral weight bearing. [Subjects and Methods] Thirty healthy young adults participated in this study. The subjects were assessed by using the foot posture index, and were divided into three groups: normal foot, pronated foot, and supinated foot groups. The knee adduction moment and knee-ground reaction force lever arm under the studied conditions were measured by using a three-dimensional motion capture system and force plates. [Results] In the normal and pronated groups, the change in knee adduction moment significantly decreased under the lateral wedge insole condition compared with the medial wedge insole condition. In the normal group, the change in the knee-ground reaction force lever arm also significantly decreased under the lateral wedge insole condition than under the medial wedge insole condition. [Conclusion] Lateral wedge insoles significantly reduced the knee adduction moment and knee-ground reaction force lever arm during unilateral weight bearing in subjects with normal feet, and the biomechanical effects varied according to individual foot alignment.

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.