Computed tomography-based morphometric analysis of cervical pedicles in Indian population
Authors: Patwardhan AR , Nemade PS , Bhosale SK , Srivastava SK 
Published: February 2014

Background:
Cervical transpedicular screw fixation is safe and is probably going to be the gold standard for cervical spine fixation. However, cervical transpedicular screw use in the Asian population can be limited as the transverse diameter in this group of patients may not be adequate to accommodate the 3.5-mm pedicular screw thus injuring the vital structures located in the close proximity of the pedicles. Thus lateral mass fixation remains the mainstay of treatment. The present study evaluated the transverse cervical pedicle diameter of C2-C7 vertebrae in a pilot study in 27 Indian subjects using computed tomography (CT) imaging and evaluated the feasibility of transpedicular screw fixation in them.

Aims:
To evaluate the feasibility of transpedicular screw fixation in the Indian population.

Settings and Design:
The cervical pedicle diameter size differs between the Asian and non-Asian population. The authors studied the transverse pedicle diameter of the C2-C7 of the cervical spine in the Indian population using CT measurements. This cross-sectional study was carried out at a tertiary care centre for a period of four months from October 2010 to December 2010.

Material and Methods:
Measurements of cervical pedicles in the subjects were performed on the CT workstation from the CT images taken at 2.5-mm interval. The transverse pedicle diameter was defined as the outermost diameter of the pedicle, taken perpendicular to the axis of the pedicle at the narrowest point and measured in millimeters±0.1 mm.

Statistical Analysis:
Descriptive statistics was used to represent percentage of transverse diameter of cervical pedicles less than 5 mm in male and female subjects at C2-C7 levels. Since there is no previous study done in India, we initiated the study with sample size of 27 as a pilot study. The statistical analysis was performed using SPSS software.

Results:
The mean transverse diameters of the cervical pedicles of C2, C3, C4, C5, C6 and C7 in males were 5.3, 5.3, 5.3, 5.6, 5.6 and 6.1 mm respectively and ranged between 5.3 to 6.1 mm. The mean transverse diameters of the cervical pedicles of C2, C3, C4, C5, C6 and C7 in females were 5.1, 4.6, 4.7, 4.7, 5.3 and 5.6 mm respectively and ranged between 4.6 to 5.6 mm. Between 2.1% and 55.7% of pedicles in our male population and between 5.5% and 74.3% pedicles in our female population was smaller than 5.0 mm in transverse diameter and thus cannot have fixation with a 3.5 mm screw using this technique.

Conclusions:
We found that the transverse pedicle diameter of cervical pedicles in the Indian subjects is smaller compared to the Western population. Although transpedicular screw fixation has stronger pullout strength compared to lateral mass fixation, its use must be considered carefully and individually. Preoperative CT evaluation is a must before transpedicular fixation in the cervical spine, especially in the Indian female population. As an option 2.7-mm screws can be devised for the Indian population giving a wider safety margin.