An Investigation of Fat Infiltration of the Multifidus Muscle in Patients With Severe Neck Symptoms Associated With Chronic Whiplash-Associated Disorder.

Anette Karlsson, Olof Dahlqvist Leinhard, Ulrika Åslund, Janne West, Thobias Romu, Örjan Smedby, Peter Zsigmond, Anneli Peolsson

Study Design Cross-sectional study. Background Findings of fat infiltration in cervical spine multifidus, as a sign of degenerative morphometric changes due to the whiplash injury, need to be verified. Objectives To develop a method using water/fat magnetic resonance imaging (MRI) to investigate fat infiltration and cross-sectional area of multifidus muscle in individuals with whiplash-associated disorders (WAD) compared to healthy controls. Methods Fat infiltration and cross-sectional area in the multifidus muscles spanning the C4 and C7 segmental levels were investigated by manual segmentation using water/fat separated MRI in 31 participants with WAD and 31 controls, matched for age and sex. Results Based on average values for data spanning C4 to C7, participants with severe disability related to WAD had 38% greater muscular fat infiltration compared to healthy controls (P=.03) and 45% greater fat infiltration compared to those with mild/moderate disability related to WAD (P=.02). There were no significant differences between those with mild/moderate disability and healthy controls. No significant differences between groups were found for multifidus cross-sectional area. Significant differences were observed for both cross-sectional area and fat infiltration between segmental levels. Conclusions Participants with severe disability after a whiplash injury had higher fat infiltration in the multifidus compared to controls and to those with mild/moderate disability secondary to WAD. Earlier reported findings using T1-weighted MRI were reproduced using refined imaging technology. The results of the study also indicate a risk when segmenting single cross-sectional slices as both cross-sectional area and fat infiltration differ between cervical levels. J Orthop Sports Phys Ther, Epub 2 Sep 2016. doi:10.2519/jospt.2016.6553.