Diário da Espinha

Computed Tomographic Morphometric Study of the Occipital Bone Thickness in 100 Adult, Moroccan Patients

Abstract

Said Hilmani, Ngamasata Trezor, Rim Amzil, Omar Kacimi and Abdessamad El Azhari

Background: Occipital cervical fixation (OCF) is an important and difficult technic and has certain risks due to its relation with adjacent special anatomic features. One of specific areas to perform screw fixation and to prevent technical failures is the thickness of the occipital bone which require detailed morphological anatomical knowledge. To our knowledge, no published study has provided thicknesses of occiput in African Continent.

Objective: The aim of this study was to evaluate occipital bony thickness in Moroccan population in order to determine the variability of the occipital bone thickness and to assess the feasibility and safety of hook and screw placement in these patients.

Patients and methods: We evaluated occipital bony thickness using computed tomography (CT) imaging in 100 patients (30 females and 70 males; age range, 18–70; mean, 36.2 ± 11.9 years). Axial CT cutting was made at 1.25 mm intervals.

CT measurements were performed on the bone windows at two levels starting at 1 cm under the external occipital protuberance (EOP) and 1 cm inferior to this level. Three measurements were performed both sides at 1 cm interval. We acquired 14 values.

Results: The mean thickness of occipital bones varied between 10.003 to 13.964 mm in the left and 10.747 to 13.715 mm in the right (± 2.8) and between 9.845 to 11.478 mm in the left and 9.903 to 11.371 in the right (± 2.5) at 1 cm and 2 cm above EOP respectively. The thickest point was in the midline with 17.366 mm and 12.579 mm at 1 cm and 2 cm above EOP respectively,

Intra-individual and inter-individual discrepancies are found between left and right sides (p<0.05) but not between age and sex at two levels in our adult patients.

Conclusion: Our radiological study findings suggest that there were significant differences between individuals and ethnics. The preoperative CT scans of occipital bony thickness as the pedicle size should be thoroughly analysed of patients undergoing occipital cervical fixation. These are essential for successful intraoperative fusion and to further decrease the risk of occipito-cervical fusion.