The stand for model tests of human hip joint musculoskeletal system - possibilities of research and applications

Anna Dąbrowska-Tkaczyk

Abstract

1. Introduction The test stand is used to determine the kinematic functions of the rotation movement in the hip joint and kinematic functions for muscle actuators performing this movement. It has been used for the studies a commercial models of the hip bone structures or designed model of the patient hip joint bone system, produced using rapid prototyping, based on the results of medical imaging (CT, MRI) and developed a virtual model. It is very important also to assure the exact representation of the geometry of the skeletal muscle system on the test stand. 2. The test stand and method Stand for testing models of human hip joint (Fig. 1) consists of the mechanical supporting part on which the system (3) of the pelvic bone KM and sacrum KK connected to each other is mounted. The important part of the stand is the mechanism for rotation in the hip joint (4) connecting the bone pelvic KM with the femur KU. In the supporting part also have been distinguished (fig. 1) the systems and mechanisms of attachments, such as: a double articulated mechanism (5) for positioning the angular position of the pelvic bone, setting mechanism (7) for guiding the tip of the femoral bone KU during the movement in the hip joint with the limitations of space of femur mobility to a selected planes and the system [6] mounting and running the lines representing models of particular muscle actuators. The measuring part includes a sensor system and power supply and connection box [8], through which all sensors are connected to a PC measuring card. The test stand makes possible, registration and processing of measured thirty signals simultaneously. Fig. 1. The construction of the stand [1] The stand provides the possibilities of: examination of different medical cases i. e.,: hip joints of women, men, children as well as the deformed hip joints – due to different causes, simulations of normal and pathologically changed bone systems of the hip joints (both left and right, respectively) by means of a proper positioning and mounting of the pelvic and femur bones, respectively, at different: inclination angles, neck-to-shaft angles, ways of asymmetry between the left and right hip joints against the sagittal plane. Yhe stand allows also for examination of the hip joint with an endoprosthesis, simulation of femur rotations in the hip joint within the specified angular ranges, simulation of 3D femur rotations as well as movements constrained to one of the defined planes. 1. Measurements and data processing The following test program was developed: • Measurements of changes in distances between the specified muscle attachment points, representing the changes of muscle lengths Li(t), (for 27 actuators) that occur in the course of simulated femur movements in the hip joint, • Simultaneous measurements of three angular motions of the femur: j(t) in the sagittal plane (flexion – extension), y(t) in the frontal plane (adduction – abduction), h(t) rotation about the femur long axis. • Recording and processing of the measurement data using the special software (fig.2). Fig. 2. The example of the results of measurements and data processing The following information which is useful in theoretical and numerical modeling can be extracted from the experimental results: • Experimental characteristics: Li(t), i=1,...,27, j (t), h(t), y(t), • Numerical characteristics; i.e., velocities and accelerations both linear : Vi(t) = dLi/dt, ai(t) = dvi/dt, and angular: dj(t)/dt, dh(t)/dt, dy(t)/dt, d2j(t)/dt2, d2h(t)/dt2, d2y(t)/dt2, • Directions of muscle actuators: cos ax, cos ay, cos az in assumed global coordinate system, changing in function of femur rotation angles j (t), h(t), y(t), • Conclusions about of muscle work (concentric or eccentric), • Sequence of muscular actuators activities during the considered movement. 4. Conclusions The basic assumption in designing and construction of the test stand is that the geometric structure of the functional elements of the human movement system (the geometry of the bone elements cooperating with the muscle actuators by a system of tendons and ligaments, and their cooperation during the implementation of motion) is closely linked to the optimal load transfer through the structure. Disturbances in the construction of this structure introduce disturbances in the process of load transfer. The redundancy of the number of actuators of muscle allows to compensate for the possible effects of improper movement control including those stemming from defects in the existing structure of the geometric layout. References Dąbrowska-Tkaczyk A., Mianowski K., Pędzisz R., Grygoruk R., Jastrzębski R.: Stanowisko do badania modeli stawu biodrowego człowieka, Urząd Patentowy RP, Patent nr 220303, Warszawa, 2015
Author Anna Dąbrowska-Tkaczyk IMP
Anna Dąbrowska-Tkaczyk,,
- The Institute of Mechanics and Printing
Pages2-2
Publication size in sheets0.3
Book Dąbrowska-Tkaczyk Anna (eds.): Biomechanics 2016, 2016
Keywords in Englishhip joint, experimental research, musculoskeletal system, material models
Languageen angielski
Not used for evaluationyes
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