Development Of Continuous Passive Motion Instrument For Infant Hip Joint

With the improvement of orthopedic medicine,people are paying more and more attention to the developmental dysplasia of the hip in infants.How to treat it had become one of the key research directions in the field of infant orthopedics.To this end,experts have reported many improved methods which basis of the traditional surgical methods or conservative methods.Among the conservative methods,the concept of treatment has gradually developed from static fixation to dynamic fixation.But the improved surgical method still brought huge trauma to infants.At the same time,although the treatment concept of dynamic fixation has developed,it also introduced a new problem of greater dependence on labor.What a focal issue is finding convenient,safe,effective,and advanced treatments with fewer complications to treat the developmental dysplasia of the hip in infants.On the other hand,the theory of continuous passive movement has received extensive attention from orthopedic physicians since it was proposed.This treatment is simple,safe and painless,and it has been proven to stimulate the development of bone tissue,and has great biological benefits.In addition,the robot technology penetrates into all fields of society due to the development of science,and it has gradually replaced humans in many fields.It greatly improving work efficiency,and providing a solid technical foundation for the realization of continuous passive motion.Existing continuous passive motion instruments can be divided by hands,upper limbs and lower limbs,while the instruments for lower limbs include all the degrees of freedom of the hip joint and it’s motion postures include sitting,standing and supine positions.The existing continuous passive motion devices cannot be used in the developmental dysplasia of the hip in infants,due to the size structure and movement posture.Facing the current shortage of conservative treatment methods for infants and young children,in view of the lack of continuous passive motion equipment suitable for infants and young children’s hip joints,combined with clinical needs and national standards for medical equipment,a continuous infant hip joint was designed and developed.Passive motion equipment,which has completed the detection of various parameters of the equipment,provides a technical basis for the study of the therapeutic effect of continuous passive motion on the developmental dysplasia of the hip in infants and young children.The specific work is as follows:(1)In terms of hardware system design,the selection of major components such as microcontrollers,solenoid valves,display screens,and air pressure sensors have been completed.Then with ATMEGA128A-AU microcontroller as the core,supplemented by level conversion circuit,air pressure sensor,resistive touch screen module and triode switch circuit,the design of the electrical system of the host is completed.Combining with the requirements of pneumatic drive,the selection of the on-off solenoid valve and the working solenoid valve completes the design of the air flow system of the main engine,and makes the air flow system accept the control of the electrical system to achieve precise control of the input air pressure.(2)In the aspect of movable stent,the frog-style fixed stent in the conservative method was used as the prototype,and the waist and leg fixing stent were separated and connected with pneumatic actuators.The pneumatic actuator will be connected to the host through the air pipe and will be controlled by the host.It can realize continuous passive motion of the hip joint driven by air pressure after the infant worn the stent.(3)In terms of software system design,a resistive touch screen control program based on the DGUS communication protocol is written.A friendly human-computer interaction interface can be displayed on the resistive touch screen,and users can use this interface to adjust motion parameters.Set up the Arduino IDE integrated software development environment,use the interrupter to time and change the time mark,thus design the polling system control instrument based on the time mark.(4)In order to check whether the instrument meets the design goals,a measurement plan is set for target parameters such as noise and exercise period.The performance parameter measurement is completed by using a decibel meter,a precision stopwatch,a medical leakage current tester and a medical withstand voltage tester.(5)Since the relative rotation angle of the acetabulum and the femoral head cannot be directly measured during exercise,the hip-leg angle is introduced to explain the definition of the hip-leg angle and derive the relationship between the relative rotation angle of the acetabulum and the femoral head and the hip-leg angle.From the derivation process,it is concluded that the angle difference between the hip and leg angle is equal to the relative rotation angle of the acetabulum and the femoral head.Since the hip and leg angle can be directly measured,the design scheme measures the hip and leg angle.(6)Since the actual movement is three-dimensional,the changes in hip and leg angles during the movement are also three-dimensional.Therefore,a three-dimensional inertial sensor-based angle measurement system was built.First,the selection of the three-dimensional inertial sensor and microcontroller was completed,and then the STM32F103ZET6 microcontroller module,power supply module,display module and other circuits were designed according to the measurement task.(7)After the angle measurement system is built,the MDK(Keil5)integrated software writing environment is built,and the measurement code is written,which can obtain the Euler angle data of the inertial sensor and save it in the SD card.Finally,the Euler angle data is derived,combined with the rotation matrix algorithm and the vector coordinate algorithm,to calculate the angle difference between the hip and leg angles during the movement,that is,the relative rotation angle between the acetabulum and the femoral head.