Can measuring passive neck muscle stiffness in whiplash injury patients help detect false whiplash claims?

BACKGROUND: Whiplash injury of the cervical spine is the most common injury after a car accident and in 25% of patients it progresses into chronic neck pain. AIM OF THE STUDY: To investigate the difference in neck muscle stiffness using shear wave ultrasound elastography between subjects who suffered an uncomplicated whiplash injury and a control group. Possible recognition of patients who insist on physical therapy in order to support their false whiplash injury claims. METHODS: This study included 75 whiplash injury patients and 75 control subjects. Trapezius, splenius capitis and sternocleidomastoid muscles were examined by ultrasound shear wave elastography. RESULTS: Increased muscle stiffness was noticed in trapezius muscle bilaterally in the whiplash group when compared to the control group (p < 0.001; right 57.47 ± 13.82 kPa vs. 87.84 ± 23.23 kPa; left 54.4 ± 12.68 kPa vs. 87.21 ± 26.47 kPa). Muscle stiffness in splenius capitis and sternocleidomastoid muscles was not suitable for analysis because of asymmetrical data distribution. Patients with less than 76 kPa of muscle stiffness in trapezius muscle are unlikely to belong in whiplash injury group (sensitivity 90% for right and 97% for left trapezius muscle, specificity 72% and 73%, respectively). CONCLUSION: Patients measuring below 76 kPa of muscle stiffness in the trapezius muscle might have no whiplash injury. Further follow-up of the patients measuring higher than cut-off value might be beneficial for detecting patients with prolonged neck muscle spasm that can lead to chronic cervical pain syndrome.