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Journal of the Korean Shoulder and Elbow Society 2000;3(2):87-94.
Published online December 30, 2000.
Electromyographic Activity of the Biceps Brachii Muscle in Shoulders With Anterior Instability
Seung-Ho Kim, M.D., Kwon-Ick Ha, M.D., Hyeon-Sook Kim, M.D.*, Seon-Woo Kim, Ph.D.†, Jong Hyuk Park, M.D., and Young-Min Kim, M.D.
Department of Orthopaedic Surgery; Department of Rehabilitation*
Samsung Medical Center, Sungkyunkwan University; and Statistical Unit, Samsung Biomedical Research Center
Seoul, Korea
전방 불안정성 견관절에서 이두박근의 근전도 활동성
김승호, 하권익, 김현숙, 김선우, 박종혁, 김영민
성균관대학교 의과대학 삼성서울병원 정형외과학교실, 재활의학과학교실*
삼성생명과학연구소 통계실†
: The purpose of this study was to evaluate the activity of the biceps brachii muscle in the vulnerable abduction and external rotation position of the shoulder in patients with anterior instability. Materials and Methods : This experimental study include a prospective analysis of the electromyographic EMG) data on a group of patients with traumatic unilateral anterior instability of the shoulder. The EMG data of unstable shoulders was compared with those of opposite shoulders as control. The optimal sample size for the case-control study was calculated using an nQuery Advisor program(nQuery Adviser 3.0, Statisticl solutions Ltd., Ireland). The EMG analyses were conducted in 76 shoulders in 38 patients who had a traumatic anterior instability in one shoulder. The EMG records were obtained at different position of shoulder, which included 0°, 45°, 90°and 120°of shoulder abduction. In each angle of shoulder abduction, the arms were placed in an external rotation as tolerated by the anterior apprehension. The paired-sample T test was used to compare the difference of the root mean square(RMS) voltages between the stable and unstable shoulders in each degree of arm position. Results : The RMS voltage of the biceps muscle was significantly greater in the unstable shoulder than opposite stable shoulder in all position of the arm(p<0.001). The RMS voltage of the biceps was maximal at 90°and 120°of external rotation in the unstable shoulder(p<0.05). The RMS voltage of the supraspinatus muscle revealed no differences in any of the test conditions(p=0.904, 0.506, 0.119 and 0.781 in 0°, 45°, 90°and 120°, respectively) Conclusion : In the vulnerable abduction and external rotation position, the biceps muscle plays an active compensatory role in the unstable shoulder while not in the stable shoulder.
Key Words: Shoulder, Biceps Brachii, Electromyography, SLAP lesion, Instability
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