Sagittal alignment of cervical flexion and extension: lateral radiographic analysis.
METHODS
An analysis of lateral radiographs in the upright, flexion-extension position.


OBJECTIVE
To document and define the differences in cervical flexion-extension kinematics as they relate to changes of alignment in upright cervical lordosis.


BACKGROUND
No previous study has reported the association between sagittal plane cervical rotation kinematics and changes of alignment in upright cervical lordosis.


METHODS
Lateral radiographs were classified into five groups (Group A, lordosis; Group B, straight; Group C, kyphosis; Group D, S-curve with lordotic upper cervical and kyphotic lower cervical spine; and Group E, S-curve with kyphotic upper cervical and lordotic lower cervical spine) by changes of alignment in upright position. Sagittal cervical rotation angles were measured by a computer-assisted method in the fully flexed and extended positions.


RESULTS
Group A revealed the largest angle of lordosis at extension and the smallest angle of kyphosis at flexion, whereas Group C revealed the smallest angle of lordosis at extension and the largest angle of kyphosis at flexion. When Group D adopted the flexion-extension position, the curvature of the upper cervical spine was the same as Group A, whereas the lower cervical spine showed the same curve as Group C. Similarly, the cervical rotation kinematics in Group E were a combination of motion of upper cervical spine in Group C and that of lower spine in Group A.


CONCLUSIONS
The results suggest that alterations in the static alignment of the cervical curvature cause alterations in the dynamic kinematics of the cervical spine during cervical flexion-extension. This information should aid in the interpretation of kinematic studies of the cervical spine.
Takeshima
Toshichika
T
Department of Orthopedic Surgery, Takanohara Central Hospital, Nara-City, Nara, Japan. t-take@naramed-u.ac.jp
Omokawa
Shohei
S
Takaoka
Takanori
T
Araki
Masafumi
M
Ueda
Yurito
Y
Takakura
Yoshinori
Y
D000328:Adult; D001696:Biomechanical Phenomena; D001827:Body Height; D001835:Body Weight; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000145:classification / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008141:Lordosis / Q000145:classification / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D009333:Neck / Q000000981:diagnostic imaging* / Q000503:physiopathology; D018583:Pliability; D011187:Posture; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012399:Rotation