Background: Normal motions of the ribs and scapula should be analyzed to identify costal and scapular dyskinesia in patients with idiopathic frozen shoulder. The purpose of this study was to investigate characteristics of their motions and compare the amount of translation or angle in 2 different aged groups.
Methods: We recruited 33 normal subjects and classified them into 2 groups: younger (Y) group aged 20 years old (10 males, 7 females) and middle (M) aged group aged from 40 to 60 years old (8 males, 8 females). We took 3D-CT of the thorax in resting and 160° elevation positions, calculating the amounts of motion in all ribs, thoracic spine, and scapula. Scapular motion was evaluated with scapulohumeral rhythm (SHR).
Results: The 5th rib remarkably translated in both groups. There was neither significant difference in the amounts of ribs, nor thoracic spine, motion between Y and M groups. SHR in Y group (3.0) was higher than that in M group (2.4). No differences were found in SHR of males between the 2 groups, however, SHR in females of Y group showed significantly higher than that of M group.
Conclusion: The 5th rib showed the greatest amount of translation during arm elevation. There was neither significant difference in the amounts of ribs, nor thoracic spine, motion between Y and M groups.
