Choongsoo Shin
Sogang University, Mechanical Engineering, Faculty Member
- Engineering, Health Sciences, Biomechanics, Sport Biomechanics, Biomechanical Engineering, Gait Biomechanics, and 14 moreKnee Biomechanics, Injury Prevention, Human Biomechanic Modelling, Sport, Physical Education, Exercise Science, Mechanical Engineering, Ergonomics, Visual perception, Kinesiology, Strength and Conditioning, Anterior Cruciate Ligament, Acl Injuries in Football Players, and Neuro muscular Fatigueedit
- Post-Doc. Radiology & Biomedical Imaging, USCF
Ph.D. Mechanical Engineering, Stanford Universityedit
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DISCUSSION Results of this study show that TF contact area calculated using 3D-SPGR and FSE sequence are strongly correlated, though measured contact area using FSE images underestimated values by 28% compared to that using 3D-SPGR. These... more
DISCUSSION Results of this study show that TF contact area calculated using 3D-SPGR and FSE sequence are strongly correlated, though measured contact area using FSE images underestimated values by 28% compared to that using 3D-SPGR. These results suggest that both imaging sequences could be used to measure cartilage-to-cartilage contact area but the direct comparison of cartilage contact from different sequences should consider the fact that FSE images lead to underestimation of cartilage-to- cartilage contact compared to 3D-SPGR images. This study has shown that acute loading on the tibiofemoral joint resulted in significant increase of TF contact area both at the medial and lateral compartments. It is also interesting to note that the contact area in the medial compartment was twice as large as that in the lateral compartment under loaded condition. These results suggest that the in vivo articular contact environment in the medial compartment changes dramatically under acute loadi...
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The purpose of this study was to investigate the relationship between muscular parameters of quadriceps/hamstrings and knee joint kinetics in gait. Muscle architecture (thickness, pennation angle, and fascicle length), and quality (echo... more
The purpose of this study was to investigate the relationship between muscular parameters of quadriceps/hamstrings and knee joint kinetics in gait. Muscle architecture (thickness, pennation angle, and fascicle length), and quality (echo intensity) of individual quadriceps and hamstrings of 30 healthy participants (16 males and 14 females) was measured using ultrasound. Peak knee flexion moment (KFM), KFM impulse, peak knee adduction moment (KAM), and KAM impulse during walking were obtained at preferred speed. Pearson’s correlation coefficient and multiple regression analyses were performed at significance level of 0.05, and Cohen’s f2 values were calculated to examine the effect sizes of multiple regression. The hamstring-to-quadriceps muscle thickness ratio (r = 0.373) and semitendinosus echo intensity (r = − 0.371) were predictors of first peak KFM (R2 = 0.294, P = 0.009, f2 = 0.42), whereas only vastus medialis (VM) echo intensity was a significant predictor of second peak KFM ...
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The movement pattern during stair descent differs by gender, and this difference may be associated with gender differences in muscle strength or activation. The purpose of this study was to determine whether a gender difference in muscle... more
The movement pattern during stair descent differs by gender, and this difference may be associated with gender differences in muscle strength or activation. The purpose of this study was to determine whether a gender difference in muscle activation exists by comparing the muscle activation amplitude and co-activation of lower extremity muscles during the stair-to-ground descent transition. Fifteen men and thirteen women descended stairs and the muscle activation was measured. Women showed a significantly lower peak normalized electromyography amplitude of the vastus lateralis (women: 171.7% peak EMG activation amplitude for level walking (PEALW), men: 297.0%PEALW, p < 0.05). Additionally, women showed significantly elevated co-activation of the vastus lateralis and biceps femoris compared to men (p < 0.05). The lower amplitude of the vastus lateralis in women indicates lower recruitment of knee extensor. In conclusion, the significantly higher co-activation of the vastus later...
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We investigated 3D kinematic and kinetic changes of knee and ankle during downhill walking as the slope angle increased and evaluated biomechanical injury risk factors related to non-contact ACL injury. Fifteen male subjects performed... more
We investigated 3D kinematic and kinetic changes of knee and ankle during downhill walking as the slope angle increased and evaluated biomechanical injury risk factors related to non-contact ACL injury. Fifteen male subjects performed level walking and 15° and 25° downhill walking. For the kinetic and kinematic parameters, one-way ANOVA and post-hoc tests were performed at a significance level of 0.05. This study revealed significant differences in 3D knee and ankle kinematics and kinetics among 0°, 15° and 25° downhill walking. The peak posterior ground reaction force, the peak knee anterior force and the knee valgus moment (0° vs. 15°: p < 0.05; 0° vs. 25°: p < 0.05) in the early stance phase increased as the slope angle increased. The peak knee internal tibial rotation moments in the late stance also increased (0° vs. 15°: p < 0.05; 0° vs. 25°: p < 0.05; 15° and 25°: p < 0.05) as the slope angle increased. These results showed the risk for ACL injuries may be increased during downhill walking with a greater slope angle.
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Background: Muscle thickness can influence the joint kinematics and/or kinetics during dynamic activities. The relationship between the muscle thickness of individual quadriceps and hamstrings or medial-to-lateral thigh muscle thickness... more
Background: Muscle thickness can influence the joint kinematics and/or kinetics during dynamic activities. The relationship between the muscle thickness of individual quadriceps and hamstrings or medial-to-lateral thigh muscle thickness ratio and the knee kinematics/kinetics with respect to anterior cruciate ligament (ACL) injury risk remains unclear. Hypothesis: Higher medial-to-lateral thigh muscle thickness ratio would be associated with lower knee valgus angle/moment and lower tibial internal rotation angle/moment during single-leg landing. Study Design: Cross-sectional. Level of Evidence: Level 4. Methods: Muscle thickness of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) of 30 healthy participants (16 males and 14 females) were measured using ultrasound. Knee joint kinematics and kinetics during single-leg landing were obtained. Stepwise multiple regression analysis, a follow-up Fisher’s r to z test to examine the sex as a moderat...
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The purpose of this study was to examine whether there is a sex difference in the effect of ankle plantar flexion at the contact angle, ankle range of motion (ROM), and ankle plantar flexion moment on knee valgus loading during single-leg... more
The purpose of this study was to examine whether there is a sex difference in the effect of ankle plantar flexion at the contact angle, ankle range of motion (ROM), and ankle plantar flexion moment on knee valgus loading during single-leg landing. Twenty-five females and twenty-four males performed a single-leg landing. Joint kinematics and kinetics of the lower extremities were measured. Correlation coefficients were used to assess the relationship between ankle biomechanics in the sagittal plane (ankle plantar flexion angle at contact, ROM, and peak ankle plantar flexion moment) and peak knee valgus moment. In males, the larger ankle plantarflexion angle at contact and ROM were significantly associated with lower peak knee valgus moment (r = − 0.46, p < 0.05; and r = − 0.42, p < 0.05). In addition, in males only, a greater peak ankle plantar flexion moment was significantly associated with a lower peak knee valgus moment (r = − 0.83, p < 0.001) and greater peak ankle inve...
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The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculoskeletal model, which enables the adjustment of ligament length and implant alignment; validate the model; and evaluate the effects of... more
The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculoskeletal model, which enables the adjustment of ligament length and implant alignment; validate the model; and evaluate the effects of varus/valgus alignment adjustment and unbalanced medial/lateral ligament laxity during gait. A cruciate-retaining total knee arthroplasty musculoskeletal model was constructed and validated against the in vivo contact forces. This model was transformed to 2° varus/valgus alignment of femoral or tibial replacement models and 2° medial/lateral laxity models. The contact forces and ligament tensions of the adjusted models were calculated. The contact forces in the model showed good agreement with the in vivo contact forces. Valgus replacement alignment with balanced ligament models showed a lower contact force at the medial compartment than at the neutral alignment model, whereas the varus replacement alignment with balanced ligament models showed a greater co...
The metatarsophalangeal (MTP) joint is not considered in most current walking assistive devices even though it plays an important role during walking. The purpose of this study was to develop a new MTP assistive device and investigate its... more
The metatarsophalangeal (MTP) joint is not considered in most current walking assistive devices even though it plays an important role during walking. The purpose of this study was to develop a new MTP assistive device and investigate its effectiveness on the muscle activities of the lower extremities during walking while wearing the device. The MTP assistive device is designed to support MTP flexion by transmitting force through a cable that runs parallel with the plantar fascia. Eight participants were instructed to walk at a constant speed on a treadmill while wearing the device. The muscle activities of their lower extremities and MTP joint kinematics were obtained during walking under both actuated and non-actuated conditions. Paired t-tests were performed to compare the differences in each dependent variable between the two conditions. The muscle activity of the MTP flexor was significantly reduced during walking under actuated conditions (p = 0.013), whereas no differences we...
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The purpose of this study was to investigate the effect of load carriage on the kinematics and kinetics of the ankle and knee joints during uphill walking, including joint work, range of motion (ROM), and stance time. Fourteen males... more
The purpose of this study was to investigate the effect of load carriage on the kinematics and kinetics of the ankle and knee joints during uphill walking, including joint work, range of motion (ROM), and stance time. Fourteen males walked at a self-selected speed on an uphill (15°) slope wearing military boots and carrying a rifle in hand without a backpack (control condition) and with a backpack. The results showed that the stance time significantly decreased with backpack carriage (p<.05). The mediolateral impulse significantly increased with backpack carriage (p<.05). In the ankle joints, the inversion-eversion, and dorsi-plantar flexion ROM in the ankle joints increased with backpack carriage (p<.05). The greater dorsi-plantar flexion ROM with backpack carriage suggested one strategy for obtaining high plantar flexor power during uphill walking. The result of the increased mediolateral impulse and inversion-eversion ROM in the ankle joints indicated an increase in body...
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Upslope-walking is more challenging and therefore has a greater fall risk than level-walking. The current study aimed to investigate the difference in control strategy for stability between level and upslope walking using the center of... more
Upslope-walking is more challenging and therefore has a greater fall risk than level-walking. The current study aimed to investigate the difference in control strategy for stability between level and upslope walking using the center of pressure (COP) and the ratio of three sub-phases in stance phase (loading-response, mid-stance and push-off). Two hypotheses were tested: the excursion, range, and speed of the COP increases in the mediolateral and anteroposterior directions with slope grade; and the duration of the midstance phase increases with slope grade. Eleven male subjects walked on a level (0°) surface and upslope at 15° and 25°. The duration of the mid-stance phase was significantly greater in the 25° upslope-walking condition than that in the level and 15° upslope-walking conditions (both p<0.05). This result implies that the subjects adopted a different control strategy when walking upslope at 25° than when walking level and upslope at 15°. The range and speed of the mediolateral COP were larger in the 25° upslope-walking condition than those in the level and 15° upslope-walking conditions (p<0.05). This result indicates that a change in control strategy during upslope-walking at 25° can improve mediolateral stability. These findings imply that a transition grade exists between 15° and 25° where one can alter their control strategy to improve stability during upslope-walking.
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During continuous uphill walking (UW) or downhill walking, human locomotion is modified to counteract the gravitational force, aiding or impeding the body's forward momentum, respectively. This study aimed at investigating the center... more
During continuous uphill walking (UW) or downhill walking, human locomotion is modified to counteract the gravitational force, aiding or impeding the body's forward momentum, respectively. This study aimed at investigating the center of mass (COM) and center of pressure (COP) velocities and their relative distance during the transition from uphill to downhill walking (UDW) to determine whether locomotor adjustments differ between UDW and UW. Fourteen participants walked on a triangular slope and a continuous upslope of 15°. The kinematics and COPs were obtained using a force plate and a motion capture system. The vertical velocity of the COM in the propulsion phase, the horizontal distance between the COM and COP at initial contact, and the duration of the subphases significantly differed between UDW and UW (all < 0.05). Compared with the results of UW, longer durations and the deeper downward moving COM in the propulsion phase were observed during UDW (all < 0.05). Additi...
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Classification of terrain is a vital component in giving suitable control to a walking assistive device for the various walking conditions. Although surface electromyography (sEMG) signals have been combined with inputs from other sensors... more
Classification of terrain is a vital component in giving suitable control to a walking assistive device for the various walking conditions. Although surface electromyography (sEMG) signals have been combined with inputs from other sensors to detect walking intention, no study has yet classified walking environments using sEMG only. Therefore, the purpose of this study is to classify the current walking environment based on the entire sEMG profile gathered from selected muscles in the lower extremities. The muscle activations of selected muscles in the lower extremities were measured in 27 participants while they walked over flat-ground, upstairs, downstairs, uphill, and downhill. An artificial neural network (ANN) was employed to classify these walking environments using the entire sEMG profile recorded for all muscles during the stance phase. The result shows that the ANN was able to classify the current walking environment with high accuracy of 96.3% when using activation from all...
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Background: Core stability is influential in the incidence of lower extremity injuries, including anterior cruciate ligament (ACL) injuries, but the effects of core strength training on the risk for ACL injury remain unclear. Hypothesis:... more
Background: Core stability is influential in the incidence of lower extremity injuries, including anterior cruciate ligament (ACL) injuries, but the effects of core strength training on the risk for ACL injury remain unclear. Hypothesis: Core muscle strength training increases the knee flexion angle, hamstring to quadriceps (H:Q) coactivation ratio, and vastus medialis to vastus lateralis (VM:VL) muscle activation ratio, as well as decreases the hip adduction, knee valgus, and tibial internal rotation angles. Study Design: Controlled laboratory study. Methods: A total of 48 male participants were recruited and randomly assigned to either the intervention group (n = 32) or the control group (n = 16). Three-dimensional trunk, hip, knee, and ankle kinematic data and muscle activations of selected trunk and lower extremity muscles were obtained while the participants performed side-step cutting. The core endurance scores were measured before and after training. Two-way analyses of varia...
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During landing, the ankle angle at initial contact (IC) exhibits relatively wide individual variation compared to the knee and hip angles. However, little is known about the effect of different IC ankle angles on energy dissipation. The... more
During landing, the ankle angle at initial contact (IC) exhibits relatively wide individual variation compared to the knee and hip angles. However, little is known about the effect of different IC ankle angles on energy dissipation. The purpose of this study was to investigate the relationship between individual ankle angles at IC and energy dissipation in the lower extremity joints. Twenty-seven adults performed single-leg landings from a 0.3-m height. Kinetics and kinematics of the lower extremity joints were measured. The relationship between ankle angles at IC and negative work, range of motion, the time to peak ground reaction force, and peak loading rate were analyzed. The ankle angle at IC was positively correlated with ankle negative work (r = 0.80, R = 0.64, p < 0.001) and the contribution of the ankle to total (ankle, knee and hip joint) negative work (r = 0.84, R = 0.70, p < 0.001), but the ankle angle was negatively correlated with hip negative work (r = -0.46, R =...
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Falls on stairs often result in severe injury and occur twice as frequently in women. However, gender differences in kinetics and kinematics during stair descent are unknown. Thus, this study aimed to determine whether gender differences... more
Falls on stairs often result in severe injury and occur twice as frequently in women. However, gender differences in kinetics and kinematics during stair descent are unknown. Thus, this study aimed to determine whether gender differences of knee and ankle biomechanics exist in the sagittal plane during the stair-to-ground descending transition. It was hypothesized that 1) women would reveal higher ground-toe-trochanter angle and lower ground-toe length during stair-to-ground descent transition than men; and 2) women would reveal lower peak knee extension moment during stair-to-ground descent transition than men. Fifteen men and fifteen women were recruited and performed a stair descent activity. Kinetic and kinematic data were obtained using a force plate and motion capture system. The women performed the stair descent with a lower peak knee extension moment and a peak knee power at the early weight acceptance phase. The women also revealed a higher ground-toe-trochanter angle and a...
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ABSTRACT Intracochlear fluid pressure and cochlear input impedance are simulated and compared with in-vivo physiological measurements. The objective of this work is to compare the calculations and measurements for the cochlear fluid... more
ABSTRACT Intracochlear fluid pressure and cochlear input impedance are simulated and compared with in-vivo physiological measurements. The objective of this work is to compare the calculations and measurements for the cochlear fluid pressure (PST) and related cochlear input impedance (ZC) with “push-pull” active cochlear model involving cochlear cytoarchitecture. Presented three-dimensional cochlear hydro-dynamic model is developed by implementing an active “push-pull” cochlear amplifier mechanism based on Y-shaped organ of Corti cytoarchitecture and using the time-averaged Lagrangian method. For the gerbil PST magnitude, the model results shows (i) the nonlinearity with 10 dB gain, (ii) the 2/3 octave shift in the active case, and (iii) the presence of peaks and valleys which are observed in gerbil in vivo measurement. Additionally, simulation results of chinchilla and cat cochlear |ZC| reflect overall trend of animal measurements, while the gerbil and human cochlear |ZC| are 10 dB lower (&gt; 2 kHz) and 7 dB lower (&lt; 2 kHz) than the measurements respectively.
ABSTRACT Long-term oxygen therapy (LTOT) has been widely used to treat patients with chronic obstructive pulmonary disease. The traditional oxygen delivery methods used for LTOT are continuous flow oxygen (CFO) and demand oxygen delivery... more
ABSTRACT Long-term oxygen therapy (LTOT) has been widely used to treat patients with chronic obstructive pulmonary disease. The traditional oxygen delivery methods used for LTOT are continuous flow oxygen (CFO) and demand oxygen delivery (DOD). CFO wastes a considerable amount of oxygen, whereas DOD often makes patients feel uncomfortable because it abruptly supplies a large amount of oxygen at the onset of inhalation. Hence, we developed an algorithm for predicting the onset of inhalation, which allowed oxygen to be supplied smoothly before inhalation. Moreover, we minimized the discomfort index (DI) to offer more comfortable oxygen delivery. By integrating the prediction algorithm and the minimization of DI, the previous synchronized demand oxygen delivery (SDOD) method was modified. We constructed a bench model to validate the modified SDOD. The results showed that the proposed algorithm accurately predicted the onset of inhalation. The difference in the real-time measured and predicted values for the beginning of inhalation was less than 0.10 s. Using the proposed minimization technique, the DI was decreased by 50% under 20 breaths per minute when compared with the DI calculated from a previous study. In conclusion, the modified SDOD could supply oxygen more comfortably while synchronizing with patient breathing patterns.
The traditional oxygen delivery methods for oxygen therapy are continuous flow oxygen (CFO) and demand oxygen delivery (DOD); however, oxygen waste is considerable in CFO, while DOD is uncomfortable for patients. Synchronized DOD (SDOD),... more
The traditional oxygen delivery methods for oxygen therapy are continuous flow oxygen (CFO) and demand oxygen delivery (DOD); however, oxygen waste is considerable in CFO, while DOD is uncomfortable for patients. Synchronized DOD (SDOD), which was designed to overcome the drawbacks of both CFO and DOD, supplies oxygen according to the patient's breathing pattern and the desired oxygen saving. This study was conducted to examine the overall performance of SDOD in terms of oxygen saturation (SpO2 ), patients' comfort, and oxygen saving ratio (SR). Study subjects were patients who required oxygen for COPD or pneumonia. Patients received oxygen through nasal prongs by CFO and SDOD for 30 min each. SpO2 was measured every 10 min by pulse oximetry, and subjects recorded their level of comfort after 30 min. The flow of discharged oxygen was recorded to calculate SR. Ten subjects (median age, 68 y; range, 56-86 y) were enrolled. The SpO2 of patients during SDOD (97 ± 2%) was similar...
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Oxygen has been widely used for COPD patients because long-term oxygen therapy can improve survival duration of COPD patients with severe hypoxemia. The typical oxygen delivery methods used for long-term oxygen therapy are continuous flow... more
Oxygen has been widely used for COPD patients because long-term oxygen therapy can improve survival duration of COPD patients with severe hypoxemia. The typical oxygen delivery methods used for long-term oxygen therapy are continuous flow oxygen (CFO) and demand oxygen delivery (DOD). Currently, DOD is preferred to CFO in oxygen conserving devices because waste of oxygen is substantial in CFO. However, DOD causes discomfort to patients since it abruptly supplies high-flow oxygen during inhalation only. To overcome the drawbacks of CFO and DOD, we developed a novel oxygen delivery method, synchronized DOD (SDOD), which can reduce waste oxygen and patient discomfort. We used the concept of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;jerk&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; from physics, which indicates the rate of change of acceleration, and defined a discomfort index (DI) to quantitatively represent the degree of discomfort. To determine the correlation between DI and the actual human feeling of discomfort, we tested subjects&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; responses to different levels of DI. Moreover, depending on the level of oxygen saving of each method, CFO, DOD, and SDOD regions were identified in a prescription flow/supply flow plane. A bench study was conducted to experimentally compare the Fio2 between CFO and SDOD at 20 breaths/min. The results of this study illustrate that there is a region of compromise between oxygen saving and patient comfort that is filled by SDOD. DI is positively correlated with actual human discomfort (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001). In addition, the DI of SDOD was much lower than that of DOD. Fio2 of SDOD was 2-5% less than that of CFO. In conclusion, SDOD might provide more comfortable oxygen delivery by reducing DI, and conserves oxygen while offering an equivalent Fio2.
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Anterior cruciate ligament (ACL) rupture is one of the most common injuries associated with the knee. After ACL injury, knee joint stability can be altered, resulting in abnormal loading during functional activities. Since ACL-deficient... more
Anterior cruciate ligament (ACL) rupture is one of the most common injuries associated with the knee. After ACL injury, knee joint stability can be altered, resulting in abnormal loading during functional activities. Since ACL-deficient (ACLD) knees are also vulnerable to translational and rotational instability, patients need to be wary of certain motions encountered in daily life. The present study investigated the effect of walking speed and pivoting directional change during gait on knee joint kinematics of ACLD knees. We hypothesized that faster walking and crossover turning would induce severe kinematic changes. Thirty-five patients (22 males and 13 females) having a unilateral isolated subacute ACLD knee (from 1 to 3 months after injury) and contralateral intact (CLI) knee participated in this study. Spatiotemporal parameters, three-dimensional (3D) knee joint angles, and anterior-posterior (AP) translation were obtained by a 3D high-speed motion-capturing system. The CLI kne...
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The growth plate (physis) is responsible for long bone growth through endochondral ossification, a process which can be mechanically modulated. However, our understanding of the detailed mechanical behavior of physeal cartilage occurring... more
The growth plate (physis) is responsible for long bone growth through endochondral ossification, a process which can be mechanically modulated. However, our understanding of the detailed mechanical behavior of physeal cartilage occurring in vivo is limited. In this study, we aimed to quantify the time-dependent deformational behavior of physeal cartilage in intact knees under physiologically realistic dynamic loading, and compare physeal cartilage deformation with articular cartilage deformation. A 4.7 T MRI scanner continuously scanned a knee joint in the sagittal plane through the central load-bearing region of the medial compartment every 2.5 min while a realistic cyclic loading was applied. A custom auto-segmentation program was developed to delineate complex physeal cartilage boundaries. Physeal volume changes at each time step were calculated. The new auto-segmentation was found to be reproducible with COV of the volume measurements being less than 0.5%. Time-constants of physeal cartilage consolidation (1.31±0.74 min) and recovery (1.63±0.70 min) were significantly smaller than the values (5.53±1.78/17.71±13.88 min for consolidation/recovery) in articular cartilage (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05). The rapid consolidation and recovery of physeal cartilage may due to a relatively free metaphyseal fluid boundary which would allow rapid fluid exchange with the adjacent cancellous bone. This may impair the generation of hydrostatic pressure in the cartilage matrix when the physis is under chronic compressive loading, and may be related to the premature ossification of the growth plate under such conditions. Research on the growth plate fluid exchange may provide a more comprehensive understanding of mechanisms and disorders of long bone growth.
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Research Interests: Biomedical Engineering, Tissue Engineering, Nanofibers, Nanoparticles, Nanotechnology, and 12 morePolymers, Humans, Porosity, Biomedical Materials, Medical Biotechnology, Animals, Drug Delivery Systems, Surface Properties, Bone Substitutes, Materials Testing, Biocompatible Materials, and Electric Conductivity
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Following ACL injury a reduction in the peak knee flexion moment during walking (thought to be created by a decrease of quadriceps contraction) has been described as an adaptation to reduce anterior tibial translation (ATT) relative to... more
Following ACL injury a reduction in the peak knee flexion moment during walking (thought to be created by a decrease of quadriceps contraction) has been described as an adaptation to reduce anterior tibial translation (ATT) relative to the femur. However, the amount of ATT caused by quadriceps contraction is influenced by the patellar ligament insertion angle (PLIA). The purpose of this study was to test the hypothesis that quadriceps usage during walking correlates to individual anatomical variations in the extensor mechanism as defined by PLIA. PLIA and gait were measured for ACL-deficient knees, using subjects' contralateral knees as controls. In ACL-deficient knees, PLIA was negatively correlated (R2 = 0.59) to peak knee flexion moment (balanced by net quadriceps moment), while no correlation was found in contralateral knees. Reduction in peak flexion moment in ACL-deficient knees compared to their contralateral knees was distinctive in subjects with large PLIA, possibly to avoid excessive ATT. These results suggest that subject-specific anatomic variability of knee extensor mechanism may account for the individual variability previously observed in adaptation to a quadriceps reduction strategy following ACL injury. The average (±1 SD) PLIA of ACL-deficient knees (21.1 ± 3.4°) was less than the average PLIA of contralateral knees (23.9 ± 3.1°). This altered equilibrium position of the tibiofemoral joint associated with reduced PLIA and adaptations of gait patterns following ACL injury may be associated with degenerative changes in the articular cartilage. In the future, individually tailored treatment and rehabilitation considering individuals' specific extensor anatomy may improve clinical outcomes. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1643–1650, 2007
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Reduced quadriceps contraction has been suggested as an adaptation to prevent anterior tibial translation in anterior cruciate ligament (ACL)-deficient knees. This theory has been supported by a recent study that peak knee flexion moment... more
Reduced quadriceps contraction has been suggested as an adaptation to prevent anterior tibial translation in anterior cruciate ligament (ACL)-deficient knees. This theory has been supported by a recent study that peak knee flexion moment (thought to be created by a decrease of quadriceps contraction) during walking was negatively correlated with patellar ligament insertion angle (PLIA) in ACL-deficient knees, but not in contralateral, uninjured knees. In addition, the PLIA was significantly smaller in ACL-deficient knees than in contralateral, uninjured knees. However, it is unknown whether ACL reconstruction restores the PLIA or whether the relationship between the PLIA and knee flexion moments previously observed in ACL-deficient knees disappears. This study tested the following hypotheses: (1) The PLIA of ACL-reconstructed knees is significantly smaller than the PLIA of uninjured contralateral knees; (2) Peak knee flexion moment (balanced by net quadriceps moment) during walking is negatively correlated with the PLIA in ACL-reconstructed knees. The PLIA of 24 ACL-reconstructed and contralateral knees were measured using MRI, and peak knee flexion moments during walking were measured. Results showed that the PLIA of ACL-reconstructed (22.9 ± 4.4°) knees was not significantly smaller (p = 0.09, power = 0.99) than the PLIA of contralateral (24.1 ± 4.8°) knees. Peak knee flexion moment was not correlated with the PLIA following ACL reconstruction (R2 = 0.016, power = 0.99). However, the magnitude of the knee flexion moment remained significantly lower in ACL-reconstructed knees. In summary, this study has shown that the PLIA of ACL-reconstructed knees returned to normal and that patients no longer adapt their gait in response to the PLIA, though quadriceps function did not return to normal levels. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 730–735, 2009
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Research Interests: Orthopedic Surgery, Magnetic Resonance Imaging, Treatment, Anterior Cruciate Ligament, Humans, and 18 moreKinematics, Female, Male, Three Dimensional Imaging, Young Adult, Clinical Sciences, In Vivo, Adult, Knee injuries, Contact area, Deficiency, Three Dimensional, Deficit, Nuclear Magnetic Resonance Imaging, Knee Joint, Case Control Studies, Biomechanical Phenomena, and Magnetic resonance image
Anterior cruciate ligament (ACL) injury commonly occurs during single limb landing or stopping from a run, yet the conditions that influence ACL strain are not well understood. The purpose of this study was to develop, test and apply a 3D... more
Anterior cruciate ligament (ACL) injury commonly occurs during single limb landing or stopping from a run, yet the conditions that influence ACL strain are not well understood. The purpose of this study was to develop, test and apply a 3D specimen-specific dynamic simulation model of the knee designed to evaluate the influence of deceleration forces during running to a stop (single-leg landing) on ACL strain. This work tested the conceptual development of the model by simulating a physical experiment that provided direct measurements of ACL strain during vertical impact loading (peak value 1294N) with the leg near full extension. The properties of the soft tissue structures were estimated by simulating previous experiments described in the literature. A key element of the model was obtaining precise anatomy from segmented MR images of the soft tissue structures and articular geometry for the tibiofemoral and patellofemoral joints of the knee used in the cadaver experiment. The model predictions were correlated (Pearson correlation coefficient 0.889) to the temporal and amplitude characteristic of the experimental strains. The simulation model was then used to test the balance between ACL strain produced by quadriceps contraction and the reductions in ACL strain associated with the posterior braking force. When posterior forces that replicated in vivo conditions were applied, the peak ACL strain was reduced. These results suggest that the typical deceleration force that occurs during running to a single limb landing can substantially reduce the strain in the ACL relative to conditions associated with an isolated single limb landing from a vertical jump.
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Recently demand oxygen delivery (DOD) system has been preferred to continuous flow oxygen (CFO) method for long term oxygen therapy in patients with chronic obstructive pulmonary disease, since DOD system supplies oxygen during only... more
Recently demand oxygen delivery (DOD) system has been preferred to continuous flow oxygen (CFO) method for long term oxygen therapy in patients with chronic obstructive pulmonary disease, since DOD system supplies oxygen during only inhalation and saves oxygen consumption. However, the oxygen saving ratio have not properly compared without considering fraction of inspired oxygen (FIO2), though FIO2 determines the efficacy of treatment. The purpose of this study was 1) to investigate the equivalence between the CFO method and a DOD system in terms of FIO2 with considering dead space under various breathing parameters, 2) to propose and calculate the new effective oxygen saving ratio of the DOD method, 3) to compare FIO2 obtained from calculation with that from experiment. The mathematical and experimental models of human respiratory system were developed. FIO2 was calculated depending upon various breathing parameters and the new effective oxygen saving ratio was calculated to accurately compare oxygen saving consumption between the DOD and CFO method. Results of this study have shown that as supplied volume of oxygen increased, FIO2 linearly increased. As beat per minute or tidal volume increased, FIO2 decreased. The obtained FIO2 between mathematical model and experiment showed errors less than 5% in CFO method and less than 11% in DOD method. Effective conserving oxygen ratios of the DOD system changed between 3.4 and 3.8, but had higher values when the volume of supplied oxygen was larger. In conclusion, CFO method had different equivalent values of FIO2 depending on breathing parameters. Therefore it is appropriate to take into account of FIO2 when considering performance of oxygen saving devices. The effective oxygen saving ratio proposed in this study may provide the new valuable index of oxygen saving of the DOD method while maintaining the same treatment effect compared with CFO method. In addition, the mathematical model developed in this study seems to predict FIO2 similarly as obtained using experiment.