Anatomical feasibility of C-2 pedicle screw fixation: the effect of variable angle interpolation of axial CT scans

Clinical article

Restricted access


Anatomical variability of the C-2 pedicle poses a challenge for C-2 fixation. The use of multidimensional CT scanning is not widely used but might be an asset to preoperative planning. Careful preoperative planning is imperative for instrumentation at C-2. Fine-cut, noncontrast CT scanning is a useful tool for delineating anatomy; however, the axis of the images is not always along the anatomical axis of the vertebra in question. The authors evaluated the suitability of C-2 pedicles for screw placement by using OsiriX (Pixmeo) software to change the gantry angle of CT angiograms to measure the anatomical dimensions of the C-2 pedicle.


The authors conducted a retrospective review of CT angiograms of the head and neck from 47 trauma patients seen consecutively at George Washington University Hospital. For each patient, 3 independent observers determined length and width of each C-2 pedicle (94 samples) by using OsiriX. OsiriX is a DICOM viewer that enables navigation and visualization in multidimensional imaging, such as 3D imaging, which was used for this study. Sex-specific measurements were also determined. Vertebral anatomy was studied to determine whether aberrant anatomy would preclude pedicle fixation. Statistical analyses were performed.


Of the 47 patients, 27 were male. Overall mean C-2 pedicle widths and lengths were 8.272 ± 1.364 mm and 27.052 ± 3.471 mm, respectively. The average widths and lengths of the pedicle in female patients were 8.040 ± 1.262 mm and 27.241 ± 2.731 mm, respectively, and those in male patients were 8.444 ± 1.414 mm and 26.913 ± 3.933 mm, respectively. The sex difference was statistically significant for width (p = 0.012) but not for length (p = 0.41). On the basis of width, the percentages of pedicles that could tolerate a 3.5-mm and 4.0-mm screw were 98% and 97%, respectively. Vertebral anatomy precluded screw length greater than 14 mm for only 3 patients.


Using multidimensional CT or 3D imaging, the authors found that C-2 pedicles in over 90% of patients could tolerate 3.5-mm and 4.0-mm pedicle screws. Vertebral anatomy precluded use of screw lengths greater than 14 mm for only 3 (6%) of 47 patients. Therefore, the C-2 pedicle might be more tolerant of fixation than previously reported.

Article Information

Address correspondence to: Joseph O'Brien, M.D., M.P.H., Department of Orthopaedic Surgery, George Washington University, 2150 Pennsylvania Avenue NW, Washington, DC 20037. email:

Please include this information when citing this paper: published online March 29, 2013; DOI: 10.3171/2013.2.SPINE12798.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Measurements of pedicle length and width of a C-2 pedicle obtained by using OsiriX software on a CT axial cut to change the gantry angle to match the axis of the pedicle.

  • View in gallery

    Measurements of pedicle length and width obtained directly from a CT axial cut obtained in the same patient featured in Fig. 1.

  • View in gallery

    Axial (upper) and coronal (lower) views of a vertebral segment, showing the difference between pedicle (A) and pars screw (B) placement and trajectory. The starting point for a pedicle screw is more cephalad and aims more caudally. Reproduced with permission from Helgeson et al.: Accuracy of the freehand technique for 3 fixation methods in the C-2 vertebrae. Neurosurg Focus 31(4):E11, 2011.



Alosh HParker SLMcGirt MJGokaslan ZLWitham TFBydon A: Preoperative radiographic factors and surgeon experience are associated with cortical breach of C2 pedicle screws. J Spinal Disord Tech 23:9142010


Benke MTO'Brien JRTurner AWYu WD: Biomechanical comparison of transpedicular versus intralaminar C2 fixation in C2-C6 subaxial constructs. Spine (Phila Pa 1976) 36:E33E372011


Bhatnagar RYu WDBergin PFMatteini LEO'Brien JR: The anatomic suitability of the C2 vertebra for intralaminar and pedicular fixation: a computed tomography study. Spine J 10:8968992010


Dickman CASonntag VK: Posterior C1–C2 transarticular screw fixation for atlantoaxial arthrodesis. Neurosurgery 43:2752811998


Dmitriev AELehman RA JrHelgeson MDSasso RCKuhns CRiew DK: Acute and long-term stability of atlantoaxial fixation methods: a biomechanical comparison of pars, pedicle, and intralaminar fixation in an intact and odontoid fracture model. Spine (Phila Pa 1976) 34:3653702009


Harms JMelcher RP: Posterior C1–C2 fusion with polyaxial screw and rod fixation. Spine (Phila Pa 1976) 26:246724712001


Helgeson MDLehman RA JrDmitriev AEKang DGSasso RCTannoury C: Accuracy of the freehand technique for 3 fixation methods in the C-2 vertebrae. Neurosurg Focus 31:4E112011


Igarashi TKikuchi SSato KKayama SOtani K: Anatomic study of the axis for surgical planning of transarticular screw fixation. Clin Orthop Relat Res 408:1621662003


Jeanneret BMagerl F: Primary posterior fusion C1/2 in odontoid fractures: indications, technique, and results of transarticular screw fixation. J Spinal Disord 5:4644751992


Mandel IMKambach BJPetersilge CAJohnstone BYoo JU: Morphologic considerations of C2 isthmus dimensions for the placement of transarticular screws. Spine (Phila Pa 1976) 25:154215472000


Mummaneni PVLu DCDhall SSMummaneni VPChou D: C1 lateral mass fixation: a comparison of constructs. Neurosurgery 66:3 Suppl1531602010


Naderi SArman CGüvençer MKorman ESenoğlu MTetik S: An anatomical study of the C-2 pedicle. J Neurosurg Spine 1:3063102004


Onibokun AKhoo LTBistazzoni SChen NFSassi M: Anatomical considerations for cervical pedicle screw insertion: the use of multiplanar computerized tomography measurements in 122 consecutive clinical cases. Spine J 9:7297342009


Parker SLMcGirt MJGarcés-Ambrossi GLMehta VASciubba DMWitham TF: Translaminar versus pedicle screw fixation of C2: comparison of surgical morbidity and accuracy of 313 consecutive screws. Neurosurgery 64:5 Suppl 23433492009


Smith ZABistazzoni SOnibokun AChen NFSassi MKhoo LT: Anatomical considerations for subaxial (C2) pedicle screw placement: a radiographic study with computed tomography in 93 patients. J Spinal Disord Tech 23:1761792010


Wang MY: C2 crossing laminar screws: cadaveric morphometric analysis. Neurosurgery 59:1 Suppl 1ONS84ONS882006


Wang SWang CWood KBYan MZhou H: Radiographic evaluation of the technique for C1 lateral mass and C2 pedicle screw fixation in three hundred nineteen cases. Spine (Phila Pa 1976) 36:382011


Wright NM: Translaminar rigid screw fixation of the axis. Technical note. J Neurosurg Spine 3:4094142005




All Time Past Year Past 30 Days
Abstract Views 80 80 32
Full Text Views 79 79 17
PDF Downloads 167 167 10
EPUB Downloads 0 0 0


Google Scholar