Muscle trigger points, pressure pain threshold, and cervical range of motion in patients with high level of disability related to acute whiplash injury.

STUDY DESIGN: Cross sectional cohort study.

OBJECTIVE: To analyze the differences in the prevalence of trigger points (TrPs) between patients with acute whiplash-associated disorders (WADs) and healthy controls, and to determine if widespread pressure hypersensitivity and reduced cervical range of motion are related to the presence of TrPs in patients with acute WADs.

BACKGROUND: The relationship between active TrPs and central sensitization is not well understood in patients with acute WADs.

METHODS: Twenty individuals with a high level of disability related to acute WAD and 20 age- and sex-matched controls participated in the study. TrPs in the temporalis, masseter, upper trapezius, levator scapulae, sternocleidomastoid, suboccipital, and scalene muscles were examined. TrPs are defined as hypersensitive spots in a palpable taut band, producing a local twitch response and referred pain when palpated. Pressure pain threshold (PPT) was assessed bilaterally over the C5-6 zygapophyseal joints, second metacarpal, and tibialis anterior muscle. Active cervical range of motion, neck pain, and self-rated disability using the Neck Disability Index were also assessed.

RESULTS: The mean ± SD number of TrPs for the patients with acute WAD was 7.3 ± 2.8 (3.4 ± 2.7 were latent TrPs; 3.9 ± 2.5 were active TrPs). In comparison, healthy controls had 1.7 ± 2.2 latent and no active TrPs (P<0.01). In patients with acute WAD, the most prevalent sites for active TrPs were the levator scapulae and upper trapezius muscles. The number of active TrPs increased with higher neck pain intensity (P<0.001) and a higher number of days since the accident (P=.003). Patients had significantly lower PPTs in all tested locations and less active cervical range of motion than controls (P<.001). In the patient group, there were significant negative correlations between the number of active TrPs and PPT over the C5-C6 joints and cervical range of motion in flexion, extension, and rotation in both directions: the greater the number of active TrPs, the lower the bilateral PPT over the neck and the greater the cervical range of motion limitation.

CONCLUSIONS: The local and referred pain elicited from active TrPs reproduced neck and shoulder pain patterns in individuals with acute WADs with higher levels of disability. Patients with acute WADs exhibited widespread pressure hypersensitivity and reduced cervical mobility. The number of active TrPs was related to higher neck pain intensity, the number of days since the accident, higher pressure pain hypersensitivity over the cervical spine, and reduced active cervical range of motion.