Injury biomechanics of C2 dens fractures.

The objective of this study is to analyze the biomechanics of dens fractures of the second cervical vertebra in the adult population due to motor vehicle crashes. Case-by-case records from the Crash Injury Research and Engineering Network (CIREN) and National Automotive Sampling System (NASS) databases were used. Variables such as change in velocity, impact direction and body habitus were extracted. Results indicated that similarities exist in the two databases despite differences in sampling methods between the two sources (e.g., CIREN is not population based). Trauma is predominantly associated with the frontal mode of impact. Majority of injuries occur with change in velocities below current federal guideline thresholds. No specific bias exists with respect to variables such as age, height, weight, and gender. Because similar conclusions can be drawn with regard to vehicle model years, design changes during these years may have had little effect on this injury. To ameliorate trauma, emphasis should be placed on the frontal impact mode and entire adult population. Because of clinical implications in the fracture type (II being most critical) and lack of specific coding, CIREN data demonstrates the need to improve injury coding in the AIS and application in the NASS to enhance occupant safety and treatment in the field of automotive medicine.