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Kinematics and statics of the human shoulder
804
Abstracts-International Society of Biomechanics XIV Congress 1993
NON INVASIVE MEASUREMENT OF SCAPULA POSITION AND ITS USE TO !3TUDY THE =ING POSITION IN NORMAL AND PAINFUL SHOULDERS G R Johnson and P R Stuart, Centre for Rehabilitation and Engineering Studies, University of Newcastle upon Tyne, UK In this study the authors have used a palpation fixture in conjunction with an Isotrak sensor to study scapula movements during abduction. The spatial orientation of the scapula has been calculated: (a) in the scapular frame so that the initial position is defined as zero; (b) in the trunk frame and relative to its axes. In addition, the coordinates of the Root of the Scapula spine were measured relative to an origin at the sternum. 5 sequential measurementsof scapular position were made by two independentobservers15 on normal subjects. Subsequently,8 patientswith
glenohumeralpathologywere measuredat 10 deg. intervalsof abduction. The reliability of the system was found to be good if rotations are defined in the scapular plane and referred to the initial position. However, when the starting position is taken into account, the angle of elevation is reduced in the patient group i.e. the shoulderis “dropped”so that the glenohumeraljoint is slightly abductedin the resting position. Secondly, the horizontal coordinate of the root of the scapula spine is reduced suggesting some retraction of the scapula.
KINEMATICS AND STATICS OF THE HUMAN SHOULDER Stefanie Kirsch, Hans N;igerl, and Dietmar Kubein-Meesenburg Departments of Physics and orthodontics, University of GEttingen, Germany. In general, the art. humeri is assumed to be a pure ball-socket joint (BSJ)with three degrees of freedom, whose humerus exclusively rotates around its center. However, in vivo measurements by X-ray series show that the momentary rotational center of the humerus is shifted towards the scapula in ab-adduction movements and in ex-internal rotations, respectively. These facts are morphologically based on the inconcruity of the curvatures of the opposed articular surfaces. The radii of the glenoid are a little bit greater than the humeral ones. Presented morphological measurements yield average differences R = 2,6mm (s = 1,7mm) and R = 2,8mm (s = 2,5mm) in the frontal and horizontal plane, resp.. The art. humeri can be modelled by an overlapping dimeric ball-socket-joint with five degrees of freedom. In functional movements the humerus rotates not only around its center but also simultaneously around the center of the glenoid in opposite direction. The ratio of the corresponding angular velocities determines the position ot the momentary rotational center. The presented theory predicts kinematical features of humeral movements from morphological data.
CONTACT AREAS IN THE WRIST JOINT J.G.M. Kooloos Dept. Anatomy/Embryology, University of Nijmegen POBox 9101, 6500 HB Nijmegen, The Netherlands Contact areas in the wrist joint were calculated from computerized anatomical models. These models simulate the various discrete carpal bone positions that were documented during in vitro cadaver experiments using roentgenstereophotogrammetry. For every position the distances between relevant opposite surfaces were assessed.Based upon compressions of articular cartilage of 2.5 - 40 % and an average cartilage thickness of 0.65 m m in the wrist joint, distances not exceeding -0.5 m m represent normal cartilage contact. The results show the distributions of the distances of a moving bone relative to a fixed bone. Contact areas of the lunate relative to the radius stay in position during deviation but become larger during ulnar deviation and somewhat smaller during radial deviation. There are no scapholunate contact areas and the distance between these bones become larger during ulnar deviation. It is an improvement to be able to calculate contact areas in the highly complex wrist joint without implementing experimental devices at the contact surfaces that disturb normal carpal kinematics. Also, the used method enables the study of small intercarpal contact areas besides the larger radiocarpal and midcapal areas.
Abstracts-International Society of Biomechanics XIV Congress 1993
NON INVASIVE MEASUREMENT OF SCAPULA POSITION AND ITS USE TO !3TUDY THE =ING POSITION IN NORMAL AND PAINFUL SHOULDERS G R Johnson and P R Stuart, Centre for Rehabilitation and Engineering Studies, University of Newcastle upon Tyne, UK In this study the authors have used a palpation fixture in conjunction with an Isotrak sensor to study scapula movements during abduction. The spatial orientation of the scapula has been calculated: (a) in the scapular frame so that the initial position is defined as zero; (b) in the trunk frame and relative to its axes. In addition, the coordinates of the Root of the Scapula spine were measured relative to an origin at the sternum. 5 sequential measurementsof scapular position were made by two independentobservers15 on normal subjects. Subsequently,8 patientswith
glenohumeralpathologywere measuredat 10 deg. intervalsof abduction. The reliability of the system was found to be good if rotations are defined in the scapular plane and referred to the initial position. However, when the starting position is taken into account, the angle of elevation is reduced in the patient group i.e. the shoulderis “dropped”so that the glenohumeraljoint is slightly abductedin the resting position. Secondly, the horizontal coordinate of the root of the scapula spine is reduced suggesting some retraction of the scapula.
KINEMATICS AND STATICS OF THE HUMAN SHOULDER Stefanie Kirsch, Hans N;igerl, and Dietmar Kubein-Meesenburg Departments of Physics and orthodontics, University of GEttingen, Germany. In general, the art. humeri is assumed to be a pure ball-socket joint (BSJ)with three degrees of freedom, whose humerus exclusively rotates around its center. However, in vivo measurements by X-ray series show that the momentary rotational center of the humerus is shifted towards the scapula in ab-adduction movements and in ex-internal rotations, respectively. These facts are morphologically based on the inconcruity of the curvatures of the opposed articular surfaces. The radii of the glenoid are a little bit greater than the humeral ones. Presented morphological measurements yield average differences R = 2,6mm (s = 1,7mm) and R = 2,8mm (s = 2,5mm) in the frontal and horizontal plane, resp.. The art. humeri can be modelled by an overlapping dimeric ball-socket-joint with five degrees of freedom. In functional movements the humerus rotates not only around its center but also simultaneously around the center of the glenoid in opposite direction. The ratio of the corresponding angular velocities determines the position ot the momentary rotational center. The presented theory predicts kinematical features of humeral movements from morphological data.
CONTACT AREAS IN THE WRIST JOINT J.G.M. Kooloos Dept. Anatomy/Embryology, University of Nijmegen POBox 9101, 6500 HB Nijmegen, The Netherlands Contact areas in the wrist joint were calculated from computerized anatomical models. These models simulate the various discrete carpal bone positions that were documented during in vitro cadaver experiments using roentgenstereophotogrammetry. For every position the distances between relevant opposite surfaces were assessed.Based upon compressions of articular cartilage of 2.5 - 40 % and an average cartilage thickness of 0.65 m m in the wrist joint, distances not exceeding -0.5 m m represent normal cartilage contact. The results show the distributions of the distances of a moving bone relative to a fixed bone. Contact areas of the lunate relative to the radius stay in position during deviation but become larger during ulnar deviation and somewhat smaller during radial deviation. There are no scapholunate contact areas and the distance between these bones become larger during ulnar deviation. It is an improvement to be able to calculate contact areas in the highly complex wrist joint without implementing experimental devices at the contact surfaces that disturb normal carpal kinematics. Also, the used method enables the study of small intercarpal contact areas besides the larger radiocarpal and midcapal areas.