Modeling the Stiffness of the Interphalangeal Finger Joints on the Physical Model

A physical model of different types of contractures of the proximal interphalangeal joint was created to understand the biomechanical processes of hand functioning in conditions of stiffness of the finger joints. The purpose of the work is to determine the efforts necessary to overcome the resistance in the hinge in conditions of different types of stiffness at different angles of bending. The actions are performed on the physical model of the interphalangeal finger joints. Materials and methods. The research was carried out on the physical model of the interphalangeal finger joints. The physical model of the three-phalang hand, which was used in the study, is made of wooden billets by turning and bringing to shapes similar to real ones with the help of locksmith's refinement with observance of anatomical proportions. By twisting the screw with different force we limited the mobility of the hinge and increased the number of elastic elements on it. The database of experimental data was created and the dependency charts were constructed with the help of MSOffice Excel 2010. Results and discussion. During experimental modeling of arthrogene contracture, discrete values of internal forces were obtained at certain values of torque and bending angle . The obtained data were divided into three groups: the first – the data obtained at the angle of bending 7 °, the second – 32 °, the third – 50 °. Graphs were built for each group. The results presented on them were approximated by a square parabola. Based on the nearly approximation functions, the graphs of the internal force's dependence on the torque model, which simulates contracture, are constructed, at different angles of bending. When modeling desmogenic contracture introduced parameter k, which is the ratio of internal force to torque, built a graph of the relationship. Analyzing the graphs, the necessary efforts are made to overcome the rigidity of the hinge. Conclusions. The experiments performed on the physical model of the interphalangeal finger joints proved that: 1) when modeling arthrogenic contracture at angles of flexion from 30° to 110°, to overcome the stiffness of the hinge, it is necessary to apply an internal force of lesser magnitude (less than 2 times) than at angles up to 30; 2) when modeling desmogenic contracture at angles of flexion from 20° to 50°, an internal force of less magnitude (less than 1.5 times) must be applied to overcome stiffness, than at angles from 0° to 20° and from 50° to 90°. Prospects for further research. The obtained experimental data provide the necessary basis for the development of a mathematical model of the work of the interphalangeal finger joints, which will justify the choice of the method of treatment in terms of motion mechanics.