Original article
Three-dimensional rotation of the scapula during functional movements: An in vivo study in healthy volunteers

https://doi.org/10.1016/j.jse.2006.06.011Get rights and content

The goal of this study was to measure 3-dimensional shoulder motion by use of a direct invasive technique during 4 different arm movements in healthy volunteers. Eight subjects with healthy shoulders were recruited. Optoelectronic marker carriers (ie, infrared light-emitting diodes) were mounted on bone pins, which were inserted into the lateral scapular spine. Subjects performed 4 different arm movements while the motion was being recorded by a precision optoelectronic camera. Joint angles were calculated in 3 dimensions. Intraclass correlation coefficients and root-mean-square differences were calculated as measures of reliability. During abduction, the scapula tipped posteriorly (44° ± 11°), rotated upward (49° ± 7°), and rotated externally (27° ± 11°). For reaching, the scapula consistently rotated upward (17° ± 3°) and rotated internally (18° ± 6°) whereas tipping was generally less than 10° (5° ± 2°). Overall, the range of scapular movement for the hand behind the back was small and variable, with most rotations not exceeding 15°. For horizontal adduction, the scapula tipped anteriorly (8° ± 3°), rotated upward (5° ± 2°), and rotated internally (27° ± 6°). These scapular rotations provide normative data that will be useful for diagnosing scapular dysfunction.

Section snippets

Subjects

The inclusion criteria were that the subjects should be aged between 18 and 60 years and have normal skin integrity around the shoulder. Subjects were excluded if they were pregnant, had osteoporosis, or had current shoulder pathology. Eight healthy subjects were recruited. All chose their nondominant left shoulder to be tested. Data from 1 subject were rejected because of pin loosening (as described in the “Results” section). The mean age of the remaining subjects was 30 ± 5 years, and their

Results

The data for 1 subject were rejected. When removing the pins, the surgeon noted that the pins were loose. Data and video footage of the experiment were reviewed but could not identify a point in time when the pins failed. There appeared to be differences in the resulting movement patterns from those observed in other subjects. Although these differences could be a result of individual variation, we decided to reject the data because we could not be sure that the loosened pins moved directly

Discussion

This study described scapular motion for 4 different arm movements. It is unique in that a direct technique was used (ie, bone pins) during functional arm movements. Furthermore, the reliability of this method was assessed. During abduction, the scapula tipped posteriorly, rotated upward, and rotated externally. During reaching, the scapula rotated upward and rotated internally with a variable but small amount of scapular tipping. HBB was a small and variable movement usually consisting of

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Supported by the Natural Sciences and Engineering Research Council of Canada.

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