The role of paraspinal muscle spindles in lumbosacral position sense in individuals with and without low back pain

Study Design. A two-group experimental design with repeated measures on one factor was used. Objectives. To investigate the role of paraspinal muscle spindles in lumbos acral position sense in individuals with and without low back pain. Summary of Background Data. Proprioceptive deficits have been identified in patients with low back pain. The underlying mechanisms, however, are not w ell documented. Methods. Lumbosacral position sense was determined before, during, and afte r lumbar paraspinal muscle vibration in 23 young patients with low back pai n and in 21 control subjects. Position sense was estimated by calculating t he mean absolute error, constant error, and variable error between six crit erion and reproduction sacral tilt angles. Results. Repositioning accuracy was significantly lower in the patient grou p than in healthy individuals (absolute error difference between groups = 2 .7 degrees, P < 0.0001). Multifidus muscle vibration induced a significant muscle-lengthening illusion that resulted in an undershooting of the target position in healthy individuals (constant error = -3.1 degrees, P < 0.0001 ). Conversely, the position sense scores of the patient group did not displ ay an increase in negative directional error but a significant improvement in position sense during muscle vibration (P < 0.05). No significant differ ences in absolute error were found between the first and last trial in the healthy individuals (P greater than or equal to 0.05) and in the patient gr oup (P > 0.05). Conclusions. Patients with low back pain have a less refined position sense than healthy individuals, possibly because of an altered paraspinal muscle spindle afference and central processing of this sensory input. Furthermor e, muscle vibration can be an interesting expedient for improving proprioce ption and enhancing local muscle control.