Quantitative posturography in altered sensory conditions: a way to assess balance instability in patients with chronic whiplash injury.

OBJECTIVES

To quantify neck mobility and posture with and without various postural perturbations.

DESIGN

A multivariable 2-group study with repeated measures and treatments.

SETTING

A human performance laboratory.

PARTICIPANTS

Eleven patients with chronic whiplash injury (mean age, 33.3+/-6.7 y; weight, 73.4+/-11.4 kg; height, 173.3+/-7.2 cm) with a sex- and age-matched control group (mean age, 33.1+/-6.8 y; weight, 68+/-12.5 kg; height, 171.5+/-6.3 cm).

INTERVENTIONS: Neck mobility and the effects of postural perturbations affecting the visual, vestibular, cutaneous, proprioceptive, and nociceptive systems were measured.

MAIN OUTCOME MEASURES: Active range of motion, neck position sense, and postural activity.

RESULTS

We found significantly reduced neck mobility and increased postural activity in the patient group compared with the control group. In patients, there was significantly greater postural activity with eyes closed, eyes open and speaking, and eyes closed with Achilles' tendons vibrations compared with eyes open with no vibrations. In the controls, there was no significant effect of experimental muscle pain on postural activity.

CONCLUSIONS

Patients with chronic whiplash injury had a protective response to neck movement and different tuning, sequencing, and execution of the postural synergies probably because of excessive reliance on visual input despite a possible deficit and altered vestibular and/or proprioceptive activity. In healthy volunteers, the pain induced by a single bolus injection of hypertonic saline was probably too limited in intensity and spreading to decrease postural stability.