Chul-Seung Kim

Sex differences in the postural sway characteristics of young and elderly subjects during quiet natural standing

Aim:  It has been reported that the fall incidence in women is much higher than men and that fallers have worse postural balance performance than non‐fallers. However, it is controversial whether any sex difference in postural balance performance exists. The purpose of this study was to investigate the effects of sex and age and their interactions in balance performance during quiet standing with natural stance width.

Stimulation Pattern-Free Control of FES Cycling: Simulation Study

The aim of this paper is to investigate control strategies for functional electrical simulation (FES) cycling, with particular focus on the generation of stimulation intensities for multiple muscles, without any predetermined stimulation pattern. The control system is developed by imitating the biological neuronal control system. Specifically, the control signal on the level of joint torque (quasi-joint torque) is generated from the feedback information of lower extremities. The quasi-joint torque is then distributed to each muscle and the muscle delay is compensated, and finally, the stimulation intensity is determined. Parameters of the control system are optimized by the genetic algorithm with cost function of energy consumption and cadence error. The proposed control system is evaluated by computer simulation. The controller generates efficient stimulation even during the muscle fatigue process and successfully continues cycling without any predetermined stimulation pattern. Moreover, the controller is robust to the parameter error in the muscle delay compensator and also to the disturbances. It is expected that the proposed method would improve the FES cycling performance and relieve patients by eliminating the experimental determination of the stimulation patterns.

Comparison between Nipple-Areola Saving Subcutaneous Mastectomy and Conventional Subcutaneous Mastectomy in Local Relapse and Prognosis: 5 Year Follow-Up Results.

Backgrounds : Skin-sparing mastectomy (SSM) and the even more conservative nipple-areola-skin sparing mastectomy (NASSM) are surgical options for selected patients with indication for mastectomy. But long term result of NASSM is rare and there is no report in Korea. So, we report here 5-year follow-up results of NASSM. Materials and Methods : 202 patients who underwent SSM (N=67) or NASSM (N=135) for breast cancer at our institution between 1996 and 2006 were included in analysis. All patients were followed-up completely. For making a decision of preserving the nipple-areola complex (NAC) during operation, frozen section analysis of the retroareolar glandular tissue with precise localization was done after meticulous dissection of parenchyme under the areola. In the case of positive result in the frozen section or final histology in the NAC, NAC was sacrificed. Intra- or postoperative radiotherapy was not performed. Local relapse (LR) rate and disease free survival (DFS) was analyzed and compared the result between NASSM and SSM. Results : The mean age at diagnosis was 40.2 years old (range 24-65) and mean follow-up months of NASSM was 70.9 months and 60.5 months in SSM. 60 NACs (29.7%) of the all objective NACs were involved by cancer cell at the final histology. The cancer cell involvement to the NAC were more common in invasive carcinoma with extensive intraductal component ( p or ductal carcinoma in situ component (p=0.048). But tumor size, vascular invasion and nodal status did not affect to involvement of the cancer cell in the NAC. Local recurrences occurred in 8.9% (NASSM) and 6.0% (SSM) of all patients, but there was no significant correlation between the two procedures (p>0.05). Local recurrences occurred at NAC (8 cases), skin flap (3 cases) and chest wall (1 cases) in NASSM procedure group, and 4 skin flaps in SSM group. All NAC recurrences were treated by wide excision of NAC. After treatment of local recurrence, only one case of SSM group preceded to distant metastasis. 5 year Disease-free survival rate was 88.2% in NASSM and 88.4% in SSM group (p>0.05). Conclusion : Our long term follow-up study shows that Nipple-areola-skin sparing mastectomy is oncologically safe procedure for breast cancer in patients who are candidates for mastectomy. Even if relapse is occurred in the NAC, this recurrence cannot affect to the progression of relapse after adequate local treatment. Thus, NASSM is alternative method for SSM with oncological safety and better cosmetic outcome. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3105.

The Clinicopathologic Characteristics and Clinical Outcomes of Estrogen Receptor-Negative and Progesterone Receptor-Positive Breast Cancer.

Backgrounds : Invasive breast cancer patients with estrogen receptor positive (ER+) or progesterone receptor positive (PR+) tumors are treated by similar treatment strategies. Yet the prognosis of ER-PR+ tumor is currently controversial. The aims of this study were to evaluate the clinicopathologic characteristics and the prognosis of patients with ER-PR+ breast cancer. Materials and Methods : 1570 patients who underwent an operation for stage I-III breast cancer from January 1995 to December 2005 were included in this study. The patients were stratified according to the ER/PR phenotype and our study focused on the ER-PR+ phenotype. The clinicopathologic characteristics and the prognosis of patients with the ER-PR+ phenotype were compared with those of the patients with ER+ (ER+PR- or ER+PR+) breast cancer. Results : The mean age at diagnosis was 47.1 years (age range: 20-88) and the mean follow-up was 65.2 months. The hormone receptor phenotype was “ER-PR+” in 75 cases (4.8%) and “ER+ (ER+PR+ or ER+PR-) in 917 cases (58.4%). A patient age Conclusion : ER-PR+ tumors have more aggressive clinicopathologic features than ER+ tumors for the patient age, the tumor grade and the presence of C-erbB2 overexpression. Furthermore, ER-PR+ tumors showed a worse prognosis than did the ER+ tumors. Consequently, the treatment modality and the prognosis of the patients with ER-PR+ tumors probably need to be altered from those of the patients with ER+ tumors. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4054.

Stretch reflex system model for spasticity evaluation

The quantitative and objective evaluation of spasticity has been desired in rehabilitation and orthopaedics where subjective evaluations such as modified Ashworth scale (MAS) were mostly used. The objective of this work is to develop the knee joint model for representing various pendulum trajectories and for quantifying the spasticity. Knee joint model included the extension and flexion muscles. The joint moment consisted of both the active moment from the stretch reflex and the passive moment from the viscoelastic joint properties. The stretch reflex was modeled as nonlinear feedback of muscle length and the muscle lengthening velocity, which is physiologically-feasible. Moreover, we modeled the spastic reflex as having dynamic threshold to account for the various pendulum trajectories of spastic patients. We determined the model parameters of three patients through minimization of error between experimental and simulated trajectories. The simulated joint trajectories closely matched with the experimental ones, which show the proposed model can predict pendulum motions of patients with different spastic severities. The predicted muscle force from spastic reflex appeared more frequently in the severe spastic patient, which indicates the dynamic threshold relaxes slowly in this patient as is manifested by the variation coefficient of dynamic threshold. The proposed method provides prediction of muscle force and intuitive and objective measure of spasticity and it is expected to be useful in quantitative assessment of spasticity.

Development of Portable Gait-Event Detection System for FES Locomotion of Hemiplegic Patient

The purpose of this study is to develop a portable gait-event detection system which is necessary for the cycle-to-cycle FES(functional electrical stimulation) control of locomotion. Proposed gait-event detection system consists of a signal measurement part and gait event detection part. To make the system portable, we made following modifications from the previous wired system. That is, 1) to make the system wireless using Bluetooth communication, 2) to make the system small-sized and battery-powered by using low power consumption microprocessor. We also used a video camera system to get the reference gait events. The gait-events were detected offline at the main computer using ANN(Artificial Neural Network) of Machine learning technique. The proposed system showed no mis-detection of the gait-events of normal subject and hemiplegia subjects. The performance of the system was better than the previous wired-system, probably due to the reduction of unnatural movement during gait signal measurement. It is expected that the result of this study will be useful in the design of cycle-to-cycle FES controller.