Establishment and identification of a rat model of low back pain induced by simulated helicopter low-frequency vibration

Abstract

Objective To establish an acute low back pain (ALBP) model by simulating low-frequency vibration of helicopters and explore the causes of ALBP in army aviation pilots in order to provide a reliable animal model and evaluation method for its pathogenesis and protection. Methods Forty-eight male SD rats (8 weeks old, weighing 200±20 g) were selected and randomly divided into groups A, B and C, with vibration for 1, 3 and 6 h, respectively, and group D as blank control, with 12 rats in each group. The rats were fixed in sitting posture on a vibrating table (10 Hz, with 6 degree vibration) for corresponding durations during 5 consecutive days. Animal behavioral tests were performed before and on days 1, 4, 7 and 14 after modelling, including paw withdrawal threshold, open field test, rotarod fatigue test, gait analysis, and 24-hour food intake assessment. Finally, light microscopy was used to observe the morphological structure of the multifidus muscle. Results Behavioral examinations revealed that persistent low-frequency vibration resulted in decreased foot-contraction reflex thresholds (P < 0.01), amount of 24-hour food consumption (P < 0.01), count of upright standing (P < 0.05), rotarod velocity at rat falling off (P < 0.05), duty cycle (P < 0.05), footprint surface area (P < 0.05), and walking speed (P < 0.05). Histological observation for the multifidus muscle demonstrated cellular edema and myocyte disorganization accompanied by inflammatory cell infiltration and aggregation. Conclusion Continuous exposure to a low-frequency vibration leads to significant low back pain-related behaviors and histological changes in the lumbar multifidus muscle of rats.

Keywords

• low-frequency vibration
• acute low back pain
• animal model
• pain-related behaviors
• multifidus muscle