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Electromyography of shoulder muscles
$42
106
107
J. ShoulderElbow Surg. March/April 1996
Abstracts
ANALYSIS OF THE SHOULDER FUNCTION WITH ORIGINATED X-RAY EXAMINATION S. Hokari MD, R. Yamamoto MD, H. Tsutsui MD, K. Mihara MD, Dept of Orthopaedic Surg. Showa Univ. Fujigaoka Hospital, Yokohama, JAPAN Purpose: The evaluations of the stability in the shoulder motion was investigated by the cineradiegraphy, the X-rays and electromyographical examination. Materials and Methods: Fifteen healthy volunteers and 60 unstable shoulders were examined. Each function of the rotator cuff muscle and the scapulothracic joint were examined using the original roentogenograph named Scapula-45 and EMG. Then, cineradiographical analysis was performed on each shoulder in elevation and depression Results: Unstable shoulders had the cuff dysfunction and/or the abnormal movement of the scapulothoracJc joint and demonstrated the abnormal micromovement of the humeral head on glenoid during the elevation and the depression named "skid slip" under the cineradiographical examination Furthermore, cases with a dysfunction of the scapulothoracic joint had variable abnormal reactions of the scapula, which the skid slip also demonstrated. Conclusion: Unstable shoulders were demonstrated the skid slip. And they had the dysfunction of the rotator cuff muscle and/or the scapulothoracic joint
108
ELECTROMYOGRAPHY OF THE SUBSCAPULAR1S MUSCLE Meskers CGM, Arwert HJ & Rozing PM. Orthopaedic laboratoD", University Hospital Leiden, The Netherlands. Several investigations I already focussed on the possible existence of functional subunits in the subseapularis muscle. In order to get a better understanding of the function of the subscapularis muscle, the tbllowmg experiment was performed The EMG of the subseapularis muscle of six healthy subjects was recorded using wire electrodes. In each subject three electrodes were inserted, dividing the subscapularis muscle in three parts. The wires were inserted using semicircular needles along the medial bolder of the scapula. Proper placement was tested using reference contractions and plain X-rays. An isometric force task was used. Four positions were tested: 90~ and 60 ~ scapular abduction with the humerus in 90~ and 0~ elevation respectively. The lower pan showed the least interindividual variability and appeared to be the least influenced by position Its highest activity was during abduction in the scapular plane. The activation of the other two parts was less consistent and strongly influenced by position. Highest activity ranged from adduction in the scapular plane to addact~ou in the horizontal plane. The results underline the conclusions reached by other authors that the subseapularis muscle should be regarded as having at least two functional suburdts. The functional complexity of the subscapularis muscle is stressed.
109
lKadaba MP, Cole A, Wootten ME, McCamt P, Reid M, Mulford G, April E, Bigliani L. Intramuscular wire electromyography of the subscapularis. J. Orthop Res 1992 10:3
ELECTROMYOGIL&PHY OF SHOULDER MUSCLES Meskers CGM l, Arwert llJ 1, De Groot JH2, Rozendaal LA2& Rozing PM I. lOrthopaedic Laboratory, University Hospital Leiden, The Netherlands. 2Dept. of Mechanical Engineering and Marine Technology, Delft University of Technology, The Netherlands. Electromyography is still a tool of great value in biomechanical and orthopaedic research. The problem is however, that EMG data are poorly quantificable making interpretation difficult. We therefore developed a standardized method for quantification of EMG data in shoulder research. In an isometric force task, subjects exert forces with the upper arm in twelve directions around the longitudinal axis of the humerus. The force is kept constant. In each force direction, mean EMG activity is calculated. When the mean EMG activity is plotted against force direction typical muscle activity patterns arc obtained with a distinct silent part and a distinct active part Using a least squares algorithm the patterns are optimized. From the optimized patterns four parameters are extracted: l. height of the active part; 2 height of the silent part (= baseline activity); 3. width of the active part (= range of activation) and 4. the position of greatest EMG activty. The latter parameter is also called the principal action of a muscle and can be regarded as an estimation of its working line. A useful method for studying shonlder muscle activib, in vivo is developed. Additionally, the paranaeters obtained can be compared with predicted muscle activity patterns from a 3D dynamic model of the shoulder girdle1, which offers additional insight in the complex muscle activity patterns around the shoulder. IVan der Helm FTC. The Shoulder Mechanism: A Dynamic Approach. PhD Thesis. Delft University of Technology 1991.
ASSESSMENT OF S U P R A S P I N A T U S I N S U F F I C I E N C Y R. Hertel, MD, F.T. B a l l m e r , MD, S.M. L a m b e r t , MD, C. G e r b e r ; M D , D e p a r t m e n t of O r t h o p a e d i c S u r g e r y , Inselspital, U n i v e r s i t y of Berne, S w i t z e r l a n d . A c o n c e p t f o r a s s e s s m e n t of s u p r a s p i n a t u s f u n c t i o n w a s v a l i d a t e d in a s t u d y o n 50 i s o l a t e d lesions. Clinical d i a g n o s i s is b a s e d o n p a i n , w e a k n e s s a n d loss of a c t i v e m o t i o n . W h e n p a i n is t h e m a i n p r e s e n t i n g s y m p t o m e v a l u a t i o n of p o w e r a n d a c t i v e r a n g e of m o t i o n b e c o m e s u n c e r t a i n . P a i n is g e n e r a l l y e n h a n c e d b y e l e v a t i o n of the e x t r e m i t y , t h u s this is n o t a n ideal p o s i t i o n for t e s t i n g p o w e r . I n d e p e n d e n t l y , p o w e r e s t i m a t i o n is g r e a t l y i n f l u e n c e d b y the p o s i t i o n in w h i c h it is assessed. N e a r the e x t r e m e s of r a n g e (i.e. n e a r full external rotation for the supraspinatus) power d i s c r e p a n c i e s w e r e h i g h e s t . Loss of a c t i v e r a n g e of m o t i o n g e n e r a l l y b e g i n s at the e x t r e m e s of a m p l i t u d e a n d s h o u l d t h e r e f o r e b e t e s t e d in this critical position. F o r t h e s u p r a s p i n a t u s t h e critical p o s i t i o n is e x t e r n a l r o t a t i o n in slight e l e v a t i o n (20~ Loss of p a s s i v e r a n g e of m o t i o n is f r e q u e n t l y s u p e r i m p o s e d a n d s h o u l d be taken into a c c o u n t b e c a u s e it d o e s c l e r a r l y i n t e r f e r e w i t h the i n t e r p r e t a t i o n . Conclusion: A precise d i a g n o s i s b a s e d o n the p h y s i c a l e x a m i n a t i o n a l o n e is possible. T h e external r o t a t i o n l a g a n d the e x t e r n a l r o t a t i o n p o w e r m e a s u r e d close to full e x t e r n a l r o t a t i o n w e r e t h e m o s t u s e f u l p a r a m e t e r s to assess s u p r a s p i n a t u s insufficiency.
106
107
J. ShoulderElbow Surg. March/April 1996
Abstracts
ANALYSIS OF THE SHOULDER FUNCTION WITH ORIGINATED X-RAY EXAMINATION S. Hokari MD, R. Yamamoto MD, H. Tsutsui MD, K. Mihara MD, Dept of Orthopaedic Surg. Showa Univ. Fujigaoka Hospital, Yokohama, JAPAN Purpose: The evaluations of the stability in the shoulder motion was investigated by the cineradiegraphy, the X-rays and electromyographical examination. Materials and Methods: Fifteen healthy volunteers and 60 unstable shoulders were examined. Each function of the rotator cuff muscle and the scapulothracic joint were examined using the original roentogenograph named Scapula-45 and EMG. Then, cineradiographical analysis was performed on each shoulder in elevation and depression Results: Unstable shoulders had the cuff dysfunction and/or the abnormal movement of the scapulothoracJc joint and demonstrated the abnormal micromovement of the humeral head on glenoid during the elevation and the depression named "skid slip" under the cineradiographical examination Furthermore, cases with a dysfunction of the scapulothoracic joint had variable abnormal reactions of the scapula, which the skid slip also demonstrated. Conclusion: Unstable shoulders were demonstrated the skid slip. And they had the dysfunction of the rotator cuff muscle and/or the scapulothoracic joint
108
ELECTROMYOGRAPHY OF THE SUBSCAPULAR1S MUSCLE Meskers CGM, Arwert HJ & Rozing PM. Orthopaedic laboratoD", University Hospital Leiden, The Netherlands. Several investigations I already focussed on the possible existence of functional subunits in the subseapularis muscle. In order to get a better understanding of the function of the subscapularis muscle, the tbllowmg experiment was performed The EMG of the subseapularis muscle of six healthy subjects was recorded using wire electrodes. In each subject three electrodes were inserted, dividing the subscapularis muscle in three parts. The wires were inserted using semicircular needles along the medial bolder of the scapula. Proper placement was tested using reference contractions and plain X-rays. An isometric force task was used. Four positions were tested: 90~ and 60 ~ scapular abduction with the humerus in 90~ and 0~ elevation respectively. The lower pan showed the least interindividual variability and appeared to be the least influenced by position Its highest activity was during abduction in the scapular plane. The activation of the other two parts was less consistent and strongly influenced by position. Highest activity ranged from adduction in the scapular plane to addact~ou in the horizontal plane. The results underline the conclusions reached by other authors that the subseapularis muscle should be regarded as having at least two functional suburdts. The functional complexity of the subscapularis muscle is stressed.
109
lKadaba MP, Cole A, Wootten ME, McCamt P, Reid M, Mulford G, April E, Bigliani L. Intramuscular wire electromyography of the subscapularis. J. Orthop Res 1992 10:3
ELECTROMYOGIL&PHY OF SHOULDER MUSCLES Meskers CGM l, Arwert llJ 1, De Groot JH2, Rozendaal LA2& Rozing PM I. lOrthopaedic Laboratory, University Hospital Leiden, The Netherlands. 2Dept. of Mechanical Engineering and Marine Technology, Delft University of Technology, The Netherlands. Electromyography is still a tool of great value in biomechanical and orthopaedic research. The problem is however, that EMG data are poorly quantificable making interpretation difficult. We therefore developed a standardized method for quantification of EMG data in shoulder research. In an isometric force task, subjects exert forces with the upper arm in twelve directions around the longitudinal axis of the humerus. The force is kept constant. In each force direction, mean EMG activity is calculated. When the mean EMG activity is plotted against force direction typical muscle activity patterns arc obtained with a distinct silent part and a distinct active part Using a least squares algorithm the patterns are optimized. From the optimized patterns four parameters are extracted: l. height of the active part; 2 height of the silent part (= baseline activity); 3. width of the active part (= range of activation) and 4. the position of greatest EMG activty. The latter parameter is also called the principal action of a muscle and can be regarded as an estimation of its working line. A useful method for studying shonlder muscle activib, in vivo is developed. Additionally, the paranaeters obtained can be compared with predicted muscle activity patterns from a 3D dynamic model of the shoulder girdle1, which offers additional insight in the complex muscle activity patterns around the shoulder. IVan der Helm FTC. The Shoulder Mechanism: A Dynamic Approach. PhD Thesis. Delft University of Technology 1991.
ASSESSMENT OF S U P R A S P I N A T U S I N S U F F I C I E N C Y R. Hertel, MD, F.T. B a l l m e r , MD, S.M. L a m b e r t , MD, C. G e r b e r ; M D , D e p a r t m e n t of O r t h o p a e d i c S u r g e r y , Inselspital, U n i v e r s i t y of Berne, S w i t z e r l a n d . A c o n c e p t f o r a s s e s s m e n t of s u p r a s p i n a t u s f u n c t i o n w a s v a l i d a t e d in a s t u d y o n 50 i s o l a t e d lesions. Clinical d i a g n o s i s is b a s e d o n p a i n , w e a k n e s s a n d loss of a c t i v e m o t i o n . W h e n p a i n is t h e m a i n p r e s e n t i n g s y m p t o m e v a l u a t i o n of p o w e r a n d a c t i v e r a n g e of m o t i o n b e c o m e s u n c e r t a i n . P a i n is g e n e r a l l y e n h a n c e d b y e l e v a t i o n of the e x t r e m i t y , t h u s this is n o t a n ideal p o s i t i o n for t e s t i n g p o w e r . I n d e p e n d e n t l y , p o w e r e s t i m a t i o n is g r e a t l y i n f l u e n c e d b y the p o s i t i o n in w h i c h it is assessed. N e a r the e x t r e m e s of r a n g e (i.e. n e a r full external rotation for the supraspinatus) power d i s c r e p a n c i e s w e r e h i g h e s t . Loss of a c t i v e r a n g e of m o t i o n g e n e r a l l y b e g i n s at the e x t r e m e s of a m p l i t u d e a n d s h o u l d t h e r e f o r e b e t e s t e d in this critical position. F o r t h e s u p r a s p i n a t u s t h e critical p o s i t i o n is e x t e r n a l r o t a t i o n in slight e l e v a t i o n (20~ Loss of p a s s i v e r a n g e of m o t i o n is f r e q u e n t l y s u p e r i m p o s e d a n d s h o u l d be taken into a c c o u n t b e c a u s e it d o e s c l e r a r l y i n t e r f e r e w i t h the i n t e r p r e t a t i o n . Conclusion: A precise d i a g n o s i s b a s e d o n the p h y s i c a l e x a m i n a t i o n a l o n e is possible. T h e external r o t a t i o n l a g a n d the e x t e r n a l r o t a t i o n p o w e r m e a s u r e d close to full e x t e r n a l r o t a t i o n w e r e t h e m o s t u s e f u l p a r a m e t e r s to assess s u p r a s p i n a t u s insufficiency.