- Email: [email protected]
A video-based method for estimating three-dimensional scapular rotation
Poster Session 1/Upper Extremity. 14:45-15:45, Room 103 & Alley Area,
Poster 155
S635
A video-based method for estimating three-dimensional scapular rotation Shoji Konda1, Tsutomu Jinji 1, Toshimasa Yanai2Shinji Sakurai3 and Takuya Shimizu1 1 Graduate School of Health and Sport Sciences, Chukyo University 2 School of Life System Science and Technology, Chukyo University 3 School of Health and Sport Sciences, Chukyo University email: [email protected] INTRODUCTION The shoulder girdle is a complex structure, consisting of three bones and three anatomical joints. The movements of such a complex shoulder girdle have been measured by means of MRI, X-ray, ectromagnetic sensor or surgical methods. In these studies, the movements of multiple bones and joints are measured and described in detail, having demonstrated that the movement patterns of the scapulothoracic and glenohumeral joints are consistent across healthy individuals [1]. This consistent pattern of joint movements are named the scapulohumeral rhythm, which, to date, describe primarily the relation between the joint movements in one plane (scapular upward rotation and humeral elevation). The similar relations in other planes are also expected to exist. In the present study, a convenient, video-based method was developed to determine the scapulothoracic rhythm in three-dimension and to estimate the scapular rotation for given humeral rotation measured in dynamic activities.
METHODS Four male university subjects with no history of shoulder injury participated in the present study. After providing written informed consent, each subject was asked to hold the right arm at each of the 25 selected positions (5 elevation planes and 5 elevation angles). While the subject was holding the position, circular tape markers of 14 mm diameter were attached on the skin directly above the selected anatomical landmarks (acromion, inferior angle, spine of scapular) of scapular and those of humerus (medial and lateral epicondiles) and then, the three-dimensional coordinates of the skin markers were measured with a VICON MX motion capture system (Oxford Metrix, Oxford, UK). The rotations of the scapular and humerus relative to thorax were determined from the recorded coordinates and expressed as Eular angles. Multiple regression analysis was conducted to derive three equations that predict the scapular rotation for given sets of Eular angles representing the humeral rotation. EST a1 HT a2 HI a3 HM b1 estimateintenal rotation ESI
a4 HT a5 HI a6 HM b2 estimate upward rotaion
ESM a7 HT a8 HI a9 HM b3 estimate anteroposterior tilt EST ,I,M1 : estimated scapular rotations HT ,I ,M1 : humeral rotations
a
: regression coefficients
b
: constants
The above equations were used to predict the Eular angles representing the scapula rotation for any given humeral rotation. The same subjects were also asked to elevate-and-depress their arms in a continuous manner for three repetitions in each of the 5 elevation planes. The movements of the tape XXI ISB Congress, Poster Sessions, Wednesday 4 July 2007
markers were recorded with the same system. The rotation of the humerus relative to thorax was computed from the recorded data and the rotation of the scapula were estimated by the regression equation derived earlier. The validity of the present methodology for estimating scapular rotation was tested with the use of electromagnetic sensor (Fastrack, Polhemus, VT, USA). The scapular rotation measured with the electromagnetic sensor was regarded as the accurate values for the elevation angle < 120˚ as indicated in the literature [2]. RESULTS AND DISCUSSION The results of the validity test showed that the scapular rotations estimated with the present method and the corresponding values measured with the electromagnetic sensor were highly correlated for upward rotation and internal rotation (correlation coefficients=0.972 and 0.964, respectively), and the slopes were found near 1.0 for the horizontal adduction angle of > 30˚. These results indicate that the present method predicts scapular and internal rotation angles well (Fig.1-B) during humeral elevation for humeral horizontal adduction greater than 30˚. For the horizontal adduction angle of below 30˚, the systematic error was observed (Fig .1-A). 80
Horizontal adduction angle of 0˚
70 60
upward rotation systematic error
internal rotation
50 40 30
systematic error
20 10
(A)
0 80
Horizontal adduction angle of 60˚
70
upward rotation
60
internal rotation
50 40 30 20
(B)
10 0 0
20
40
60
80
100
120
140
hum erus elevation[deg] estim ated angle
actual angle
Fig.1 The scapular internal rotation and upward rotation [deg] in horizontal adduction angle of 0˚ (A) and 60˚ (B).
The correlation coefficients for scapular tilt were found low (0.402), indicating that the scapular anteroposterior tilt could not be estimated accurately and thus modifications of the method are necessary for the accurate measurements of the scapular rotations in all three planes. REFERENCES 1.Nobuhara, K. The shoulder: Its function and clinical aspests, Igaku-shoin Ltd.,Tokyo, 2003. 2.Karduna, A.R. Dynamic measurements of Three Dimentional Scapular Kinematics: A Validiation Study. Journal of Biomechanical Engineering, 2001,123, 184-189. Journal of Biomechanics 40(S2)
Poster 155
S635
A video-based method for estimating three-dimensional scapular rotation Shoji Konda1, Tsutomu Jinji 1, Toshimasa Yanai2Shinji Sakurai3 and Takuya Shimizu1 1 Graduate School of Health and Sport Sciences, Chukyo University 2 School of Life System Science and Technology, Chukyo University 3 School of Health and Sport Sciences, Chukyo University email: [email protected] INTRODUCTION The shoulder girdle is a complex structure, consisting of three bones and three anatomical joints. The movements of such a complex shoulder girdle have been measured by means of MRI, X-ray, ectromagnetic sensor or surgical methods. In these studies, the movements of multiple bones and joints are measured and described in detail, having demonstrated that the movement patterns of the scapulothoracic and glenohumeral joints are consistent across healthy individuals [1]. This consistent pattern of joint movements are named the scapulohumeral rhythm, which, to date, describe primarily the relation between the joint movements in one plane (scapular upward rotation and humeral elevation). The similar relations in other planes are also expected to exist. In the present study, a convenient, video-based method was developed to determine the scapulothoracic rhythm in three-dimension and to estimate the scapular rotation for given humeral rotation measured in dynamic activities.
METHODS Four male university subjects with no history of shoulder injury participated in the present study. After providing written informed consent, each subject was asked to hold the right arm at each of the 25 selected positions (5 elevation planes and 5 elevation angles). While the subject was holding the position, circular tape markers of 14 mm diameter were attached on the skin directly above the selected anatomical landmarks (acromion, inferior angle, spine of scapular) of scapular and those of humerus (medial and lateral epicondiles) and then, the three-dimensional coordinates of the skin markers were measured with a VICON MX motion capture system (Oxford Metrix, Oxford, UK). The rotations of the scapular and humerus relative to thorax were determined from the recorded coordinates and expressed as Eular angles. Multiple regression analysis was conducted to derive three equations that predict the scapular rotation for given sets of Eular angles representing the humeral rotation. EST a1 HT a2 HI a3 HM b1 estimateintenal rotation ESI
a4 HT a5 HI a6 HM b2 estimate upward rotaion
ESM a7 HT a8 HI a9 HM b3 estimate anteroposterior tilt EST ,I,M1 : estimated scapular rotations HT ,I ,M1 : humeral rotations
a
: regression coefficients
b
: constants
The above equations were used to predict the Eular angles representing the scapula rotation for any given humeral rotation. The same subjects were also asked to elevate-and-depress their arms in a continuous manner for three repetitions in each of the 5 elevation planes. The movements of the tape XXI ISB Congress, Poster Sessions, Wednesday 4 July 2007
markers were recorded with the same system. The rotation of the humerus relative to thorax was computed from the recorded data and the rotation of the scapula were estimated by the regression equation derived earlier. The validity of the present methodology for estimating scapular rotation was tested with the use of electromagnetic sensor (Fastrack, Polhemus, VT, USA). The scapular rotation measured with the electromagnetic sensor was regarded as the accurate values for the elevation angle < 120˚ as indicated in the literature [2]. RESULTS AND DISCUSSION The results of the validity test showed that the scapular rotations estimated with the present method and the corresponding values measured with the electromagnetic sensor were highly correlated for upward rotation and internal rotation (correlation coefficients=0.972 and 0.964, respectively), and the slopes were found near 1.0 for the horizontal adduction angle of > 30˚. These results indicate that the present method predicts scapular and internal rotation angles well (Fig.1-B) during humeral elevation for humeral horizontal adduction greater than 30˚. For the horizontal adduction angle of below 30˚, the systematic error was observed (Fig .1-A). 80
Horizontal adduction angle of 0˚
70 60
upward rotation systematic error
internal rotation
50 40 30
systematic error
20 10
(A)
0 80
Horizontal adduction angle of 60˚
70
upward rotation
60
internal rotation
50 40 30 20
(B)
10 0 0
20
40
60
80
100
120
140
hum erus elevation[deg] estim ated angle
actual angle
Fig.1 The scapular internal rotation and upward rotation [deg] in horizontal adduction angle of 0˚ (A) and 60˚ (B).
The correlation coefficients for scapular tilt were found low (0.402), indicating that the scapular anteroposterior tilt could not be estimated accurately and thus modifications of the method are necessary for the accurate measurements of the scapular rotations in all three planes. REFERENCES 1.Nobuhara, K. The shoulder: Its function and clinical aspests, Igaku-shoin Ltd.,Tokyo, 2003. 2.Karduna, A.R. Dynamic measurements of Three Dimentional Scapular Kinematics: A Validiation Study. Journal of Biomechanical Engineering, 2001,123, 184-189. Journal of Biomechanics 40(S2)