• Journal of the Korean Arthroscopy Society
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• v.17 no.1
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• pp.31-37
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• 2013

Purpose: This study performed to compare degree of joint stiffness and clinical results between early and delayed reconstruction of acute posterior cruciate ligament (PCL) injuries. Materials and Methods: Thirty-two Patients who underwent PCL reconstruction between March 2008 and October 2011 enrolled this study. We performed transtibial single bundle reconstruction using the allo-achilles tendon in all cases. We divided the patient into two groups, early reconstruction group underwent surgery before a week, delayed reconstruction group underwent surgery after 3 weeks, before 6 weeks. All the patients underwent aggressive joint motion exercise till surgery and enrolled post operative rehabilitation program. We checked posterior drawer stress radiography, range of motion, the Lysholm score, the International Knee Documentation Committee (IKDC) score and the Tegner score to evaluate the results. Results: At the final follow up the Lysholm score was 92.1 in the early group and 93.8 in the delayed group. All the cases were rated above B (near normal) on IKDC score (p=0.808, p=0.722). The Tegner score was 6.6 in the early reconstruction group and 6.2 in the delayed group (p=0.480), The average of maximum flexion and extension angle was $133.9^{\circ}$, $1.4^{\circ}$ in the early group and $133.6^{\circ}$, $1.1^{\circ}$ in the delayed group (p=0.560, p=0.581), no complication such as deep vein thrombosis or infection, no difference in posterior drawer stress radiography (p=0.750). Conclusion: We could obtain satisfactory clinical results in both the early and delayed reconstruction groups of acute PCL injuries. Therefore, the early reconstruction of PCL performed before a week could be one of the treatment options for acute PCL injury.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.157-165
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• 2015

Object : The goals of this research were to make Performance Enhanced Model(PE) taken the largest performance index (PI) through artificial variation of principle components calculated by principle component analysis for trial data, and to verify the effect through comparing kinematic factors between trial data (Raw) and PE. Method : Ten subjects (5 men, 5 women) were recruited and 80% of their maximal record was considered. The PI is a regression equation. In order to develop PE, we extracted Principle components from trial position data (by Principle Components Analysis (PCA)). Before PCA, we made 17 position data to 3 row matrix according to components. We calculated 3 eigen value (principle components) through PCA. And except Y (medial-lateral direction) component (because motion of Y component is small), principle components of X (anterior-posterior direction) and Z (vertical direction) components were changed as following. Changed principle components = principle components + principle components ${\times}$ k. After changing the each principle component, we reconstructed position data using the changed principle components and calculated performance index (PI). A Paired t-test was used to compare Raw data and Performance Enhanced Model data. The level of statistical significance was set at $p{\leq}0.05$. Result : The PI was significantly increased about 12.9kg at PE ($101.92{\pm}6.25$) when compared to the Raw data ($91.29{\pm}7.10$). It means that performance can be increased by optimizing 3D positions. The difference of kinematic factors as follows : the movement distance of the bar from start to lock out was significantly larger (about 1cm) for PE, the width of anterior-posterior bar position in full phase was significantly wider (about 1.3cm) for PE and the horizontal displacement toward the weightlifter after beginning of descent from maximal height was significantly greater (about 0.4cm) for PE. Additionally, the minimum knee angle in the 2-pull phase was significantly smaller (approximately 2.7cm) for the PE compared to that of the Raw. PE was decided at proximal position from the Raw (origin point (0,0)) of PC variation). Conclusion : PI was decided at proximal position from the Raw (origin point (0,0)) of PC variation). This means that Performance Enhanced Model was decided by similar motion to the Raw without a great change. Therefore, weightlifters could be accept Performance Enhanced Model easily, comfortably and without large stress. The Performance Enhance Model can provide training direction for athletes to improve their weightlifting records.

• Journal of Veterinary Clinics
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• v.30 no.1
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• pp.49-52
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• 2013

A wild black-crowned night heron (Nycticorax nycticorax) with dehydration and a non-weight bearing lameness of the left leg was rescued. On physical examination, the left knee was displaced laterally at almost a $90^{\circ}$ angle with firm swelling and crepitus in the area of the coxofemoral joint. Radiographs confirmed cranio-dorsal coxofemoral luxation. A closed reduction attempt failed. The coxofemoral joint luxation was reduced surgically by placement of the femoral neck next to the pelvis with a suture. Ten days after surgery, radiographs and computed tomography showed the femoral neck and head were positioned well within the acetabulum. At 20 days, the bird was using the affected limb normally, and could hunt and forage for food in a rehabilitation housing unit with a small pond. The bird was successfully released into the wild. The placement of the femoral neck adjacent to the pelvis with a suture can be successfully performed for cases of avian coxofemoral joint luxation. Furthermore, this procedure can provide sufficient stabilization of the coxofemoral joint and acceptable limb function.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.167-174
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• 2020

The purpose of this study was to investigate the kinematic comparison between successful and failed trials of Lopez vault techniques in male gymnastics. The subject, an Olympic gold medalist, was YHS (age: 27 years, height: 1.6 m, and mass: 53 kg) and fourteen high speed motion capturing cameras were used for data collection. The 26 reflective sensors were attached on major anatomical positions and 15 segment-body model was used to calculate the kinematic variables. According to results, the contact duration of the spring-board for successful trial(ST) was longer and that of failed trial(FT) and the range of motion of knee joint for ST was greater than that of FT. The movement times during pre-flight between ST and FT were same, but the movement time of horse contact period for ST was shorter than that of FT. The ST showed a longer movement time during post-flight and the longer horizontal distance than those of FT. Conclusively, YHS needs to approach the horse with a higher position of the body and higher incidence angle, as well as make faster twist angular velocity in an attempt to achieve ST.

• Journal of the Korean Arthroscopy Society
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• v.12 no.1
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• pp.32-39
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• 2008

Purpose: To evaluate the effectiveness of MRI after ACL reconstruction with femoral tunnel at 10 o'clock position. Materials and Methods: MRI findings of 29 patients after ACL reconstruction using hamstring tendon autograft were evaluated. The mean period from operation to MRI was 18.9 months($7{\sim}40$ months). Signal intensity, morphology and continuity of graft, femoral insertion, graft angle, roof impingement, cross pin breakage and position were evaluated. Those findings were compared with KT-2000, Lysholm knee score and pivot shift test. Results: There was no significant correlation between signal intensity of graft and the duration to MRI. Most common pattern of the morphology was straight, and the continuity was well-preserved. 13 cases of femoral tunnel insertion were zone 4 and 16 were zone 3. There were no roof impingement. 10 cases showed cross pin breakages, of which 5 were found at the outside of distal femoral posterior cortex. 9 showed cross pin directed posteriorly in axial view. There was no significant correlation between clinical results and cross pin breakage. Conclusion: MRI examinations after ACL reconstructions are useful to evaluate the graft status, position of the graft and cross pins. Since the direction of the cross pin is important especially in 10 o'clock femoral position, care should be taken to avoid cross pin breakage.

• Korean Journal of Applied Biomechanics
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• v.21 no.1
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• pp.31-38
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• 2011

This study aimed to determine the effects of the blockage of visual feedback on joint dynamics of the lower extremity. Fifteen healthy male subjects(age: $24.1{\pm}2.3\;yr$, height: $178.7{\pm}5.2\;cm$, weight: $73.6{\pm}6.6\;kg$) participated in this study. Each subject performed single-legged landing from a 45 cm-platform with the eyes open or closed. During the landing performance, three-dimensional kinematics of the lower extremity and ground reaction force(GRF) were recorded using a 8 infrared camera motion analysis system (Vicon MX-F20, Oxford Metric Ltd, Oxford, UK) with a force platform(ORG-6, AMTI, Watertown, MA). The results showed that at 50 ms prior to foot contact and at the time of foot contact, ankle plantar-flexion angle was smaller(p<.05) but the knee joint valgus and the hip flexion angles were greater with the eyes closed as compared to with the eyes open(p<.05). An increase in anterior GRF was observed during single-legged landing with the eyes closed as compared to with the eyes open(p<.05). Time to peak GRF in the medial, vertical and posterior directions occurred significantly earlier when the eyes were closed as compared to when the eyes were open(p<.05). Landing with the eyes closed resulted in a higher peak vertical loading rate(p<.05). In addition, the shock-absorbing power decreased at the ankle joint(p<.05) but increased at the hip joints when landing with the eyes closed(p<.05). When the eyes were closed, landing could be characterized by a less plantarflexed ankle joint and more flexed hip joint, with a faster time to peak GRF. These results imply that subjects are able to adapt the control of landing to different feedback conditions. Therefore, we suggest that training programs be introduced to reduce these injury risk factors.

• Journal of Korean Orthopaedic Sports Medicine
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• v.3 no.1
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• pp.66-72
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• 2004

Purpose: To evaluate the compensatory mechanism in vivo and develop the treatment guide by performing the comprehensive functional tests of the posterior cruciate ligament (PCL) deficient subjects. Material and Methods: 10 PCL deficient subjects and 10 healthy control group were evaluated. Performed functional tests were range of motion, posterior drawer test, Telos, 30$^{\circ}$ flexion wt-bearing view, KT-1000 arthrometer, gait analysis, EMG test and isokinetic tests. Results: Physical, KT-1000, Telos posterior tests showed significant differences, but 300 full weight bearing lateral view, muscle strength test revealed no difference between two groups. Less knee flexion at initial contact and reduced maximum valgus moment were observed in PCL deficient group. In vertical drop landing, PCL group had increased plantar flexion angle at initial contact. Conclusion: Compensatory mechanisms such as reduced unstable components and absorbing the maximal load of the joint were occurred after PCL insufficiency, which result in good clinical and functional outcomes. Further investigations would be needed to understand the functional adaptations of PCL deficient subjects.

• Journal of the Korean Applied Science and Technology
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• v.38 no.2
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• pp.532-542
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• 2021

The purpose of this study was to investigate the body's strategy through kinematic variables of the lower extremities and ground reaction forces to maintain the club-head speed and ball accuracy despite the three stances during the golf swing. Ten male golfers who official handicap two were participate in the experiment. All subjects performed swing after maintaining the address posture according to stance conditions(square; SS, open: OS, closed: CS). Using a 3D motion analysis system and force plateform, the results were calculated with the 7-iron full swing each stance. In result, there was no difference in center of displacement, and left and right hip and knee joint angle displacement. Left ankle joint was largely plantar-flexed in OS, and right ankle joint was largely performed in CS from the address to the downswing. From address to take-back, right foot had a large left direction and the left foot had a right direction were greater in OS than in CS. Therefore, despite various stances, maintaining the same posture at impact is thought to have a positive effect on club head speed and ball direction.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.115-121
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• 2021

Human's landing strategies have been explained through lower extremity kinetics in various conditions. However, how lower extremity kinetics respond when the two conditions between a load and landing height are combined is not yet understood. To achieve the purpose of this study, a total of 20 men and women were subjected to drop landing according to a load(No load, 10%, 20%, 30% of the body weight) at various landing heights(0.3 m, 0.4 m, 0.5 m). As a result of the study, the main effect of a load was not statistically significant in all variables. But increasing of the landing heights showed more flexion angle which was statistically significant in knee joint. In addition, as the landing height increased, the medial-lateral, anterior-posterior, vertical force, and loading rate increased, while time to peak vertical force decreased which was statistically significant. Thus, humans can successfully perform the landing motion even if the load is changed at various heights. However, it reacted more sensitively to the change in landing height than that load condition. The landing height can be prepared for recognition and shock absorption through visual information, but the weight level is difficult for the body to perceive and explains why it is more difficult to apply it to the landing strategy mechanism for shock absorption.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.109-116
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• 2023

The purpose of this study was to investigate the influence of gender and load carriage difference on the lower extremity kinetics during stair descent. Ten healthy males and 10 healthy females were recruited (n=20). In the Maximum resultant velocity, it showed more velocity was decreased with difference by the change of gender (males>females) and load carriage (30%, 20%, 10%> 10%). And, resultant velocity showed interaction between gender and a load (load>gender). Main effect by gender during stair descent showed leg length was decreased in females than that of males at initial contact phase. Also, main effect by gender during stair descent showed more hip, knee flexed and plantar flexion of ankle joint in females than that of males. In the kinetics variables, main effect by gender during stair descent showed more higher reaction force of medial-lateral direction, and leg stiffness in males than that of females. We found that females successfully accommodated a load during stair descent by decreasing the range of motion of the hip joint angle and resultant velocity of movement. Males, on the other hand, require greater medial-lateral, vertical reaction force, and leg stiffness to accommodate a load, and control of momentum.