Objective: This study aims to accurately measure the range of motion of the sternoclavicular (SC) joint using 3D reconstruction and image registration. The motion of the SC joint is analyzed by means of axial angle representation to identify the kinematical characteristics of this joint.
Methods: A total of 13 healthy volunteers were enrolled in the study. The limit postures of four SC joint movements were scanned by computerized tomography. The images were integrated with reconstruction and registration techniques. The range of motion of the SC joint was measured using 3D modelling. The axial angle was used to indicate the range of motion of the SC joint. The difference between the dominant side and non-dominant side was compared and the differences in axial angle of the SC joint in different postures were compared.
Results: The active axial angle of the SC joint on the dominant side was approximately 1∘ higher than that of the non-dominant side when the upper limb moved from a rest position to a posteroinferior position. In the sagittal motion of the upper limbs, the axial angle of the SC joint was greatest when moving from a horizontal position to a posterosuperior position, with an average of 23.55∘. Of the flexion and extension movements of the upper limbs from a rest position to a horizontal position, 13.66% (the smallest proportion) were completed by the SC joint.
Conclusion: The combination of 3D reconstruction and image registration is a direct and accurate method of measuring the motion of the SC joint. Axial angle representation is an intuitive method of expressing rotation in a 3D space that allows for more convenient comparison; it is also more in line with the characteristics of human anatomy and kinesiology and therefore more accurately reflects the characteristics of joint motion. It is therefore useful for guiding clinical practice. In a physical examination, the extension of the upper limb from the horizontal position to the posterosuperior position and from the rest position to the posteroinferior position can best reflect the rotation function of the SC joint in the combined motion of shoulder joints.
Keywords: Image registration; axial angle representation; rotation vector; sternoclavicular joints.