Evaluating the Effective Frequency of Neuromuscular Electrical Stimulation to Prevent Joint Contractures in a Rat Model

Introduction Non-weight-bearing hind limb joint fixation causes severe joint contracture, and neuromuscular electrical stimulation (NMES) can prevent this. However, the effective frequency of NMES for preventing joint contractures caused by joint fixation with non-weight-bearing hind limbs is unclear. Thus, we aimed to examine the effective frequency of NMES for joint contracture. Methods Right ankle joint fixation and hind limb suspension were performed on 60 rats for one week. The rats were divided into four groups: no NMES (NS group), NMES with a stimulation frequency of 1-50 Hz (1 Hz electrical stimulation (ES) group, 10 Hz ES group (artificial twitch muscle contraction), and 50 Hz ES group (artificial tetanic muscle contraction)). We measured the ankle dorsiflexion angle, the extensibility, and the amount of type I and III collagen of the soleus muscle. Results The decreases in the ankle dorsiflexion angle and extensibility of the soleus muscle of the 1-50 Hz ES groups on the last day of the experiment were lower than those in the NS group. The decreases in the ankle dorsiflexion angle and extensibility of the soleus muscle of the 1 Hz and 10 Hz ES groups on the last day of the experiment were lower than those of the 50 Hz ES group. There was no significant difference in the amount of type I and III collagen between the groups. Conclusion Artificial twitch muscle contractions induced by NMES were more effective than artificial tetanic muscle contractions caused by NMES in preventing joint contracture.