Echo-intensity, fatty infiltration, and morphology ultrasound imaging assessment in healthy and whiplash associated disorders populations: an observational study.

BACKGROUND: Although changes in muscle morphology and quality in deep neck flexors seem to be clear in patients with whiplash-associated disorders (WAD), evidence for deep neck extensors is heterogeneous. In addition, most studies have used magnetic resonance imaging or computer tomography, which is not available for regular practice.
OBJECTIVES: To assess differences in deep neck extensors morphology and quality between patients with WAD and controls with ultrasound imaging (US) and to assess the association of imaging findings with clinical features.
METHODS: One hundred and sixty brightness-mode images at C4/C5 level were acquired in 41 patients with WAD and 39 pain-free controls. Muscle morphology and quality characteristics of the cervical multifidus (CM) and short rotators (SR), clinical pain features and pressure pain thresholds (PPT) were assessed in a blinded design.
RESULTS: Between-groups differences in both CM and SR were observed for fatty infiltration percentage (mean: 4.9%; P < 0.001; mean: 3.5%; P < 0.05, respectively) and mean EI (mean: 4.1; P < 0.001; mean: 3.2; P < 0.05, respectively): patients exhibited higher fatty infiltration than controls. The intensity of neck pain was negatively associated with multifidus CSA and perimeter (P < 0.001); symptoms duration was negatively associated with CM morphology (P < 0.001), CM mean EI (P < 0.05) and SR morphology (P < 0.05); pain-related disability was associated with CM morphology (P < 0.001) and SR mean EI (P < 0.05); and PPTs was associated with CM mean EI (P < 0.01) and FI (p < 0.05) and SR morphology (P < 0.001). No significant effect of gender was found in any analysis.
CONCLUSION: US assessment of deep cervical extensors revealed greater fatty infiltration, but no differences in muscle morphology, between WAD patients and pain-free controls.