Understanding cervical spine instability: a finite element study on atypical hangman's fractures.

Recent reports have highlighted a notable prevalence of atypical hangman's fractures, yet their biomechanical aspects remain underexplored. Using a validated finite element model, this study assesses changes in rotation-moment characteristics of the upper cervical spine due to fractures involving the superior and inferior articular process, pars interarticularis, and lamina. The results revealed that fractures affecting the superior articular process and pars interarticularis led to significant instability, particularly in axial rotation and extension. However, atypical hangman's fractures did not necessarily produce greater instability than Levine-Edwards type II hangman's fractures.