Head position and impact direction in whiplash injuries: associations with MRI-verified lesions of ligaments and membranes in the upper cervical spine.

In the present study, we compared magnetic resonance imaging (MRI) findings of soft tissue structures in the upper cervical spine between whiplash-associated disorder (WAD) patients and population-based control persons, and examined whether MRI-verified abnormalities in WAD patients were related to accident-related factors hypothesized to be of importance for severity of injury. A total of 92 whiplash patients and 30 control persons, randomly drawn, were included. Information on the accident-related factors (i.e., head position and impact direction) was obtained by a questionnaire that was answered within 1 week after the accident. The MRI examination was performed 2-9 (mean 6) years after the accident. Focus was on MRI abnormalities of the alar and the transverse ligaments, and the tectorial and posterior atlanto-occipital membranes, graded 0-3. For all neck structures, the whiplash patients had more high-grade lesions (grade 2 or 3) than the control persons (Chi-square test, p < 0.055). An abnormal alar ligament was most common (66.3% graded 2 or 3). Whiplash patients who had been sitting with their head/neck turned to one side at the moment of collision more often had high-grade lesions of the alar and transverse ligaments (p < 0.001, p = 0.040, respectively). Severe injuries to the transverse ligament and the posterior atlanto-occipital membrane were more common in front than in rear end collisions (p < 0.001, p = 0.001, respectively). In conclusion, the difference in MRI-verified lesions between WAD patients and control persons, and in particular the association with head position and impact direction at time of accident, indicate that these lesions are caused by the whiplash trauma.