Relationship between cervical lordotic angle and cervical segmental motion during craniocervical flexion test: A cross-sectional study

The craniocervical flexion test (CCFT) is commonly used for assessing the performance and function of the deep cervical flexor muscles; however, objective measurements of cervical segmental motion during craniocervical flexion (CCF) are lacking. Therefore, the purpose of this study aimed to investigate cervical segmental motions during CCFT and determine the relationship between changes of cervical segmental motions and the cervical lordotic angle. A cross-sectional study of prospectively collected data. Twenty healthy participants without neck pain underwent standing cervical radiography (lateral view) to measure the cervical lordotic angle, followed by radiography in supine position during the CCFT. The occipito-atlantal (OA) joint angle, atlantoaxial (AA) joint angle, and cervical spinous process posterior displacement (CSPPD) of the C1-C6 vertebrae were measured using lateral cervical radiographs taken during the initial (20 mm Hg) and low-stage (24 mm Hg) CCFT conditions. The CCF motion during the low-stage CCFT was characterized by a significantly increased OA joint angle, decreased AA joint angle, and increased C1-C6 CSPPD compared with the initial stage (P < .05). The change in the value of C1-C6 CSPPD at low-stage CCFT showed a significant positive correlation with the cervical lordotic angle. These results indicate that the cervical lordotic angle is important in minimizing CSPPD and performing appropriately-isolated CCF motion during CCFT.