This study set out to offer a three-dimensional description of scapular kinematics and scapulohumeral rhythm (SHR) of healthy subjects during arm elevation and lowering, as well as to compare and analyse the differences between active and passive motion of the shoulder.Methods
The study examined the shoulders of ten healthy males (mean age: 23.5 years). The shoulders of the ten healthy participants were elevated and lowered while fluoroscopic images were taken, and three-dimensional bone models were created from 2D to 3D using model registration techniques. The Euler angle sequences of the models' scapular kinematics and SHR were compared during active and passive shoulder motion.Results
The scapula presented three-way movements of upward rotation, posterior tilting, and external rotation during arm elevation and lowering. During arm elevation, upward rotation showed a statistically significant difference between active and passive shoulder movements (p<0.05). Upward rotation between 45° and 90° showed a statistically significant difference (p<0.05). The scapular posterior tilting from the active motion resulted in more tilting in the high-degree range of motions. Additionally, statistically significant differences were found between active and passive motion (p<0.05). There was no statistically significant difference between the two groups during external rotation. However, during arm lowering, the scapular upward rotation showed a statistically significant difference between active and passive motion (both p<0.05).Conclusions
In healthy subjects, scapular kinematics showed a statistically significant difference between active and passive motion during elevation in the higher range of motion, but not during lowering. In terms of upward rotation, active shoulders rotated more upward during arm elevation. There was more upward rotation in active shoulders during arm elevation. With regard to passive motion, there was more posterior tilting during arm elevation. The scapular kinematics of upward rotation and posterior tilting showed a linear rotation during arm lowering.