Characteristic Movement of the Ribs, Thoracic Vertebrae while Elevating the Upper Limbs - Influences of Age and Gender on Movements

Abstract

Background: The rib cage, such as the thoracic spine and ribs, influences glenohumeral mobility and the development of shoulder disorders. Objective: To evaluate movements of the ribs, thoracic vertebrae during bilateral arm elevation and to clarify the characteristic influences of age and gender. Methods: Subjects comprised 33 healthy individuals divided into a young group (10 males, 7 females; mean age, 25 years) and a middle-aged group (8 males, 8 females; mean age, 52 years). Chest CT was performed with two arm positions: arms hanging downwards; and arms elevated at 160°. Images were three-dimensionally reconstructed to evaluate rib movement, extension angle of thoracic vertebrae. Results: Maximal movement was observed at the fifth rib, and rib movement decreased with increasing distance from the fifth rib in both the groups. In males, movement of the second to fourth ribs was smaller in the middle-aged group than in the young group (p < 0.05). Movement of the first to ninth ribs was smaller in females than in males (p < 0.05). No significant difference in the extension angle of the thoracic vertebrae was found. Conclusion: Fifth rib movement is the largest among all ribs during bilateral arm elevation. Reduction of upper rib movement initially arises as an age-related degradation in males. Women exhibit less rib movement during bilateral arm elevation.