The overall final range of neck flexion and extension does not represent the maximum range of rotation of the cervical intervertebral joints in healthy adults - an observational study.
This is the first study to classify joints by type of motion. Since type S constituted about half of the joints analyzed in this study, it cannot be assumed that the end range is a demonstration of the maximum motion of the joint.
Andersen, V., Wang, X., de Zee, M. etal . The overall end range of neck flexion and extension does not represent the maximum rotational range of the cervical intervertebral joint in healthy adults-an observational study. Chiropr Man Therap 29, 18 (2021). https://doi.org/10.1186/s12998-021-00376-3
Commentary
The purpose of this study was to provide a quantitative assessment of what is considered to be the maximum motion of the cervical joints as measured by clinical diagnosis and other measures at the end range of the joints, to classify the joints into types based on their motion, and to assess the ratio of these joint types.
An observational study was employed and 33 healthy subjects participated in the study. Maximal, end-range, and excess motion (the difference between maximal and end-range motion) in degrees were extracted from each cervical joint, and subjects performed a range of motion of one flexion and one extension motion under video fluoroscopy.
As a result, 48.9% of the joints in flexion and 47.2% of the joints in extension produced maximal motion before the joint's end range (type S). For flexion, 45.9% of the joints and for extension, 46.8% of the joints produced maximum movement in the end range of the joint (Type C). In flexion, 5.2% of the joints and in extension, 6.1% of the joints ended up moving in the opposite direction. (Type A)
There are some limitations to the quantification and analysis of the video fluoroscopy in this study, with the largest confounding factor being measurement error. The largest confounding factor is measurement error, and it is unclear whether this applies to different neck types, since the control group consisted of young adult males and females. Finally, the fact that the subjects were healthy was also considered a reason.
In case you are wondering, motion type refers to the classification of movement of a single joint during neck movement, and three types of motion were defined.
1) Classic type (C) Maximum motion = end position.
2) Surplus type (S) Maximum motion is greater than end position, classified using directional surplus motion.
3) Reverse direction (A), where the end position is less than the start position. In this study, the start position is upright and the end position is the end range.
