The trabecular anatomy of the axis.

This article describes the internal anatomy of C2. Although some C2 specimens showed a high density of trabecular bone throughout, a feature noted in all specimens was a void or very hypodense area of bone located immediately beneath the dens. The observed nonuniform distribution of trabecular bone within the axis is considered to have an effect on internal fixation of this bone. The good cancellous bone quality consistently observed in the lateral masses and beneath the facets, as well as near the bony end plates, suggests that these areas may be reasonable sites for the insertion of internal fixation devices. The hypodense area observed in the upper portion of C2 would suggest that fixation devices inserted through this area may obtain relatively poor purchase and may be prone to cut-through failure.