Occipitocervical neutral position. Possible surgical implications.
METHODS
The study defines the occipitocervical neutral position using cervical radiographs from 30 subjects.


OBJECTIVE
To identify reproducible radiographic measures of the occipitocervical neutral position that can be used during surgery to optimize fusion position.


BACKGROUND
When performing rigid internal fixation of the occiput to the cervical spine, the ability to determine that the occiput is in a neutral position in relation to the cervical spine is important. Currently, no objective radiographic measures for the occipitocervical neutral position exist.


METHODS
Thirty flexion, extension, and neutral lateral cervical spine radiographs radiographs interpreted as normal by an experienced radiologist were studied. The occipitocervical angle and occipitocervical distance were defined and calculated. Two investigators, an orthopedic resident and an experienced orthopedic spine surgeon, measured the occipitocervical angle and occipitocervical distance independently on all radiographs in a blinded manner. Correlation coefficients were obtained to determine interobserver reliability.


RESULTS
The mean occipitocervical angles were 24.2 degrees, 44.0 degrees, and 57.2 degrees in flexion, neutral, and extension, respectively. The mean occipitocervical distances were 21.5 mm in neutral, 28.0 mm in flexion, and 14.8 mm in extension. The differences in the occipitocervical angle and occipitocervical distance in neutral, flexion, and extension were statistically significant (P < 0.05 and < 0.001, respectively). There were no significant interobserver differences in any of the measurements.


CONCLUSIONS
The radiographic measures of the occipitocervical neutral position reported in this study are reliable, repeatable, and simple to determine on routine lateral radiographs. These measurements should be a valuable intra-operative tool for achieving occipitocervical fusion in appropriate alignment.
Phillips
F M
FM
Department of Surgery, University of Chicago Hospitals, Illinois, USA. fphillip@midway.uchicago.edu
Phillips
C S
CS
Wetzel
F T
FT
Gelinas
C
C
D000328:Adult; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000502:physiology / Q000601:surgery; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000601:surgery; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009777:Occipital Bone / Q000000981:diagnostic imaging* / Q000502:physiology; D011187:Posture; D011859:Radiography; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D013123:Spinal Fusion / Q000379:methods