Abstract
Electromagnetic systems for motion analysis are claimed as a precise technique for tracking position and orientation of human body segments. To date, reliability electromagnetic tracking was described only for the dynamic assessment of the scapula motion, and no reliability studies on its resting posture or positioning were found. The aim of this study was to analyze intra- and inter-session reliabilities and absolute errors of the scapular orientation and position at habitual resting posture in healthy individuals. Twenty-two shoulder symptom-free individuals non participants in professional or recreational sports activities involving upper extremities were volunteers in this study. The equipment used was 3SPACE Liberty system (Polhemus Inc.). The same examiner collected the kinematic data from subjects in two different sessions, with an interval from seven to ten days. Intraclass Correlation Coefficient (ICC2,1 and ICC2, k) and Standard Error of Measurement (SEM) were calculated. Inter-session reliability ranged from good to excellent (ICC from 0.66 to 0.96) and intra-session reliability was excellent (ICC ≥ 0.97). SEM values found for linear distances were smaller than 0.02 cm and scapular rotations ranged from 0.72° to 5.48°. Results of this study demonstrated that electromagnetic data acquisition of scapula habitual posture is a reliable tool for defining scapular position and orientation in sedentary shoulder symptom-free individuals.
Highlights
Assessment of scapular positioning is a theme has been emphasized in scientific literature[1,2,3,4,5,6,7,8,9,10,11]
The results showed the scapular rest position with medial and upward rotation and anterior tilt
At least three sources of error can cause reduced reliability of the measures studied: equipment accuracy, examiner ability to palpate, mark and scan reference points for the construction of repeatable anatomical models and natural variation of scapular position, which may be affected by changes in muscle tension or climate, posture inattention and emotional stress
Summary
Assessment of scapular positioning is a theme has been emphasized in scientific literature[1,2,3,4,5,6,7,8,9,10,11]. Positioning and orientation of the scapula on thorax are important to centralize the humeral head and base for normal function of shoulder joint complex during daily and sport activities[5,6,7,9]. Resting scapular position may be influenced by thorax shape, muscle activity and anatomic variations of acromioclavicular joint[7,9,13]. Many muscles are inserted on scapula and its resting position influences the length-tension relationship and the efficiency of these muscles[7,12]. Electromagnetic system for tracking of human movement allows noninvasive, three-dimension, extensive and detailed analysis of the position and movement of body segments[15]
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