Cervical muscles weakness in chronic whiplash patients

BACKGROUND: Isometric cervical strength has been used for assessing the severity of cervical spine pathologies. However there is a conspicuous dearth of information relating to cervical strength data in patients suffering from chronic whiplash. Therefore the objective of this study was to compare absolute and ratio-based isometric cervical strength scores in chronic whiplash patients with reported corresponding scores in healthy subjects. METHODS: Isometric cervical strength was measured in the directions of flexion, extension, right and left lateral flexion in 97 patients, 51 women and 46 men, using a wall-mounted dynamometer. FINDINGS: Compared to published values of normal subjects, whiplash patients suffered sharp reductions of about 90% in both genders and in all directions. The consistency of the isometric cervical strength scores as indicated by the mean coefficient of variation was relatively low, 17% and 20% in men and women respectively. The flexion/extension strength ratio ranged 0.8--0.9, slightly higher than the reported range for normal subjects. This ratio was highly correlated (r=0.91, P=0.01) with the mean coefficient of variation in a subgroup of 9 patients. INTERPRETATION: In the absence of an obvious reason such as sever atrophy or grossly dysfunctional neurological control the indicated weakness of the cervical muscles may be associated with learned pain avoidance behavior which is typical among this group of patients.