EFFECT OF CHANGES IN THE LENGTH OF THE COMPONENTS OF THE MUSCULOTENDINOUS ELEMENT OF THE ELBOW FLEXOR MUSCLES ON THE ISOMETRIC FORCE AND JOINT TORQUE

Abstract

Immobilization of the joint leads to the formation of immobilization contracture, which is accompanied by a decrease in the elasticity of tendons and muscles, i.e. loss of full contraction and stretching. The torque in human joints is one of the key indicators in assessing rehabilitation. Objective. To study the effect of changes in the strength, length of muscles and tendons of the elbow joint on the torque in flexion. Methods. The basic OpenSim model arm26 was used for modeling. To determine the change in the length of the components of the muscle-tendon element (MTE), their length was determined at a 90° angle of elbow flexion. The decrease in muscle strength was considered a loss per day for elbow flexors — 1.2 %, extensors — 1.1 %. The decrease in strength was calculated for a period of immobilization of 45 days. Three models were created: Normal — a model without changes in muscle parameters; Contracture — a change in the length of muscles and tendons; Contracture + muscle (CM) — an additional decrease in muscle strength. Results. The obtained data of torques when changing the length of the MTE components showed their increase in conditions of unchanged isometric muscle strength. But this option is not possible after immobilization of the limb. Therefore, it is closer to the real model of СM, in which the torque is significantly reduced by the amount of decrease in muscle strength. These models show a tendency that the change in the components of the MTE due to immobilization increases the joint torque and, when trying to apply excessive force during joint development, can lead to traumatic consequences. During immobilization, the flexor muscles shorten, which prevents the patient from fully extending the elbow joint. Conclusions. This work on predicting the elbow joint torque generated by the muscles can be useful in studying specific clinical situations with elbow joint contractures, but cannot be fully transferred to practice due to the significant conventionality of the model parameters. However, the modeling method can show trends in changes in muscle function parameters when their geometry changes.