Occipitocervical neutral position - Possible surgical implications

Study Design. The study defines the occipitocervical neutral position using cervical radiographs from 30 subjects. Objective. To identify reproducible radiographic measures of the occipitoce rvical neutral position that can be used during surgery to optimize fusion position. Summary of Background Data. 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. Curr ently, no objective radiographic measures for the occipitocervical neutral position exist. Methods. Thirty flexion, extension, and neutral lateral cervical spine radi ographs interpreted as normal by an experienced radiologist were studied. T he occipitocervical angle and occipitocervical distance were defined and ca lculated. Two investigators, an orthopedic resident and an experienced orth opedic spine surgeon, measured the occipitocervical angle and occipitocervi cal distance independently on all radiographs in a blinded manner. Correlat ion 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, an d 14.8 mm in extension. The differences in the occipitocervical angle and o ccipitocervical distance in neutral, flexion, and extension were statistica lly significant (P < 0.05 and < 0.001, respectively). There were no signifi cant interobserver differences in any of the measurements. Conclusions. The radiographic measures of the occipitocervical neutral posi tion reported in this study are reliable, repeatable, and simple to determi ne on routine lateral radiographs. These measurements should be a valuable intra-operative tool for achieving occipitocervical fusion in appropriate a lignment.