Active-Passive Mechanotherapy (APM) of the Ankle Joint (AJ) in Post-Traumatic Rehabilitation

Introduction

Among injuries of lower extremities, the most widespread are those of the distal part of the lower leg and ankle, which, according to literature data, make up from 12,0 to 20,0% of all fractures of locomotor apparatus. In 12-39,8% of cases, unsatisfactory results of treatment are observed, and the long-term disability lasts from 4 to 8 months. One of the most common injuries humans sustain is the damage to the ankle joint in sports, domestic and industrial exercises, and as a result of car accidents. Falling from heights with a landing on the feet, including parachuting, also often injures the ankle joint (AJ). Statistically, more than half of all lower limb injuries and about 40% of joint injuries are ankle injuries. We also know that 54% of ankle fractures and dislocations occur at a young age when the ability to work is essential. After an injury, there is a long process of treatment and rehabilitation; after surgery, rehabilitation can be complicated by prolonged joint stiffness. In many countries, work is underway to develop devices and devices that allow for the post-traumatic rehabilitation of the individual using passive mechanotherapy devices. This approach makes it possible to perform foot movements according to an individual rehabilitation program (IRP) set by the doctor. The FLEX-02, A3 Ankle CPM, Kinetec Breva ankle, and ARTROMOT SP3 are widespread (Jatsun et al., n.d.; Jatsun et al., 2016; Jatsun et al., 2018).

At the same time, due to the influence of indefinitely variable parameters of the ankle joint muscular system, it is difficult to ensure the required accuracy of the patient's foot movement along the trajectory set by the doctor, which reduces the effectiveness of the rehabilitation process.

Therefore, creating such devices requires an in-depth study of the theory of human-device interaction, the creation of man-machine interfaces, mathematical models, and control algorithms that provide the specified quality indicators. Thus, the issues of developing and creating robotic devices for post-traumatic ankle rehabilitation that provides a given foot movement under unpredictable changes in physiological parameters are relevant (Jatsun et al., 2022; Knyazev et al., 2022; Knyazev et al., 2023).

This study aims to improve the effectiveness of the rehabilitation process with an active-passive mechanotherapy and rehabilitation device that provides a given precision through adaptive control of foot movement, taking into account the individual characteristics of the patient's ankle joint.

When creating an Active-Passive Mechanotherapy of the Ankle Joint (APMAJ) device, it is necessary to take into account spasticity and tendon-muscle contracture, as well as other physiological features of the ankle joint that can significantly affect the nature of the movement of the controlled mobile platform (CMP), changing the initially selected trajectory parameters and distorting the planned rehabilitation exercises.

Due to the fact that a priori information about the actual dynamic properties of the human is significantly limited, the motion control system of the CMP of the device for mechanotherapy should compensate for changes in the physiological parameters of the human during rehabilitation and ensure the trajectory of movement with a given accuracy, being, in fact, an adaptive control system. Fundamental research of adaptive control systems in recent years has become increasingly widespread in the works of Andrievsky B.R., Bukov V.N., Krasovsky A.A., Fradkov A.L., Yakubovich V.A., and others. In the works devoted to robust control, it is shown that in practice, knowledge of the laws of statistical distributions of indeterminate quantities is often a complex condition. Hence, it is easier to set only the upper and lower bounds of their distributions and move on to considering the concept of interval uncertainty.