Introduction: Atlantoaxial region shows variable anatomy and there are vital neurovascular structures in its proximity. Knowledge of
this variability is important for neurosurgeons, orthopaedicians, etc, who in everyday practice are in contact with disorders of the spine
and their consequences. Keeping this in mind a morphometric study was carried out on atlas and axis vertebrae.
Methods: Hundred dried human atlas and axis vertebrae (50 each) available in the Department of Anatomy, DMCH Ludhiana, were
Results: Atlas vertebra: The mean of maximum anteroposterior diameter (max.APD) and maximum transverse diameter (max.TD) of
superior articular facet (SAF) was measured bilaterally, as 21.52mm+2.36 and 11.21mm±1.47 on right side, 21.51mm± 2.07and
11.32mm±1.53 on left side. On right side, the mean of max.APD and max.TD of inferior articular facet(IAF) was measured as
17.54mm±1.50 and 14.99mm±1.65 and on left side as 17.70mm±1.60 and14.94mm±1.51,respectively.
Axis vertebra: The mean of max.APD and max.TD of SAF was measured as 17.42mm±1.73 and 15.31mm±1.44 on right side,
17.64mm±1.51 and 15.17mm±1.48 on left side. On right side the mean of max.APD and max.TD of IAF was measured as
11.54mm±1.66 and 9.23mm±1.70, and on left side as 12.14mm±1.58 and 9.41mm±1.61, respectively.
Conclusion: Transarticular screw fixation has become one of the primary treatment options for C1-C2 instability. The trajectory and
angulation while screw placements is crucial because of the surrounding neurovascular structures. The knowledge of these dimensions
can provide useful information for safe planning of osseous fixation