Importance of the C1 anterior tubercle depth and lateral mass geometry when placing C1 lateral mass screws.
OBJECTIVE
We measured the variability in the size of the anterior tubercle of C1 and the optimal depth and angle of placement of C1 lateral mass screws using axial and sagittal reconstructed computed tomographic scans to determine the utility of these parameters for preoperative planning and intraoperative guidance.


METHODS
One hundred consecutive cervical spine computed tomographic scans were reviewed (mean patient age, 44.6 years; age range, 7-96 years). The size of the anterior tubercle of C1, bilateral depths of optimal screw placement in the axial and sagittal planes, and optimal angles of placement in the axial and sagittal planes were measured in a standardized manner using the measuring tool included in our radiology server software. These measurements were correlated with age and sex.


RESULTS
The mean depth of the C1 tubercle was 6.9 mm (range, 2.7-11.2 mm; standard deviation, 1.7 mm). The depth of the C1 tubercle tended to increase with age, but the relationship was not significant. The optimal screw depth in the sagittal plane was significantly greater than in the axial plane (right 2.09 versus 1.93 cm; left 2.07 versus 1.91 cm). The depth of the right lateral mass increased significantly with age. No other relationships reached significance.


CONCLUSIONS
The depth of the anterior tubercle of C1 varies considerably and should be studied carefully before using lateral fluoroscopy of this structure to guide depth of C1 lateral mass screw placement. Optimal angles and depths of placement of C1 lateral mass screws vary widely and should be examined preoperatively to plan appropriate depth and trajectory.
Wait
Scott D
SD
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, USA.
Ponce
Francisco A
FA
Colle
Kyle O
KO
Parry
Phillip V
PV
Sonntag
Volker K H
VK
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D001863:Bone Screws; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012727:Sex Characteristics; D013123:Spinal Fusion / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed; D055815:Young Adult