The influence of low-frequency vibration on the restoration of the range of knee motion in laboratory animals after immobilization (experimental study)

Background. The term “joint contractures” is used to describe the loss of passive range of motion of diarthrosis joints, the most common and mobile type of a joint. Measuring passive or active range of motion in a joint with contracture is key to assessing the severity of joint contractures. The purpose of the study: to determine the impact of immobilization on the development of movement limitation in the knee joint of laboratory animals (rats) and to evaluate the possibility of restoring mobility in case of using low-frequency vibration during and after immobilization. Materials and methods. The experimental study was conducted on 30 non-linear white male rats aged 6 months. Immobilization of the pelvic limb was performed at an angle of 140° in the knee joint. The animals were randomly divided into 3 groups: I — immobilization and free restraint after immobilization, II — immobilization and vibration development of the joint after immobilization, III — immobilization and vibration development of the joint during and after immobilization. Vibration development of the immobilized knee joint was performed daily in the mode of 20 Hz with an amplitude of 1.5 mm and a duration of 10 minutes. The range of motion and real contracture were determined as the difference between the measured range of motion and the range of motion before the start of the experiment for each animal individually. Results. It was found that a rapid increase in movement limitation occurs starting from the 2nd week of immobilization. A decrease in the range of motion in rats of the groups I and II under conditions of immobilization occurred the same way. After the end of immobilization, a slow increase in the range of motion was observed in the group I; in the group II, the growth was almost linear and after 4 weeks, the indicator was close to the norm. In the group III, the limitation of the range of motion after immobilization was significantly less; therefore, accordingly, recovery took place already 2 weeks after the removal of the immobilization bandage. Immobilization of the knee joint in rats of groups I and II caused a contracture of 60°, while in the group III, the restrictions did not exceed 25°. And, accordingly, the recovery in the groups with vibration development was rapid; in the group III, a full recovery was achieved, in the group II — a recovery of up to 5° of the residual contracture. In the group I, we observe a residual contracture of almost 35°, which is more than the formed immobilization contracture in the group III. Conclusions. Low-frequency vibration allows reducing the impact of immobilization and significantly accelerate the recovery of mobi-lity (range of motion) of the joint after its completion. If it is impossible to carry out vibrotherapy during the period of immobilization, it should be started as early as possible after immobilization. To date, there are few studies considering the effect of low-frequency vibration on the development of immobilization contractures and their treatment. The obtained data require further research with longer periods of immobilization and those examining immobilization options and modes of vibration impact on the joints.