Anatomical determination of a safe entry point for occipital condyle screw using three-dimensional landmarks.

The occipital condyle (OC) is an important area in craniovertebral surgery, but neither its anatomical features nor the procedures concerning the OC have been detailed yet. The morphological analysis of the structures were made in totally 704 sides of the occipital bones of adult skulls by 3D-Doctor Demo version. The length and width of the OC were found to be 23.9 ± 3.4 (right), 24 ± 3.3 (left) and 11.9 ± 2.3 (right), 10.7 ± 2.3 mm (left), respectively. The mean anterior intercondylar distance and the posterior intercondylar distance were measured as 20.9 ± 3.6 and 43.1 ± 4 mm, respectively. The sagittal intercondylar angle was observed as 68.7 ± 10.6º. The sagittal condylar angle was observed to be 32.9 ± 7.6º and 38.2 ± 7.3º in the right and left, respectively. The head circumference was observed to be 65.6 ± 7.8 and 64.4 ± 7.2 mm in the right and left, respectively. The head area was measured as 231.9 ± 53.3 and 214.9 ± 45.1 mm² in the right and left, respectively. The most common type was oval-like (59.67%), whereas the most unusual one was two-portioned condyle (0.32%). In Pearson correlation analysis, it was significant that a statistically strong relation was noticed between the length and area, and the circumference and area. The findings suggest that the oval type was more successful to work with, while the triangular, circular and two-portioned types were highly risky for the fixation resonance as the surface got quite smaller. As a result, we suggest that by resecting nearly half of the OC, the border of the hypoglossal canal can be involved.