| With needs for economic and social developing of our country,social labor division is more elaborate,and because of the work with simplified working means and constant repetition,the incidence of human MusculoSkeletal Disorders(MSDs)and injury increases correspondingly.If slight disorders,it can take a vacation to recover,if severe disorders,it may need surgical intervention,and if the even more disorders,it may influence locomotor function of patients,and even makes the patients disability.The office personnels and the computer operator of office automation have become the high incidence of MSDs and varied musculoskeletal injury.It not only has caused the physical and psychological agony to individual patient,but brought the heavy financial burden to family and the society.Up to now,the accurate and scientific assessment methods of diagnosis,treatment and rehabilitaiton are lacked based on the biomechanics principle and through the movement means to diagnose and treat the MSDs,injury and rehabilitation training.In addition,with computer fast popularization and application in varied industries and occupations,the mouse,as a important input device to realize human interaction with computer,has got an extensive application day by day.But the constant and repeated mouse operations can cause some MSDs of upper limb,and the common example is Carpal Tunnel Syndrome(CTS)also called "mouse hand".At present,the prevalence and trends of MSDs in our country is very severe,but because of lacking the very convinced etiology evidences and assessment methods and basises on biomechanical factors,it is diffcult to take effective prevention and control measures to effectively reduce the incidence of MSDs,and at the sime time,to reduce the economic burden on government,enterprises,individual patients,and the family.In considering the importance of biomechanical investigation and the severity of MSDs and musculoskeletal injury related with wrist and upper limb,in this paper from the views of biomechanics and on the basis of biomechanical principles and methods,the biomechanical analysis of musculoskeletal system of upper limb was conducted,and experimental measurement of wrist contact pressure while mouse operations was carried on,and compared the results with the finite element simulation.The detailed contents include:(1)Through The experimental measurement of human motion capture,the motion data of the common movements of human upper limb and finger actions of tapping the keys during mouse operations were acquired,processed and analyzed.After the procesing and analysis,the joint angles varied curves of each joint during upper limb movements were obtained.Through employing the method of inverse dynamics,the motions of wrist joint flexion and pronation-supination of forearm were analyzed and calculated,and the force moment and reaction force of elbow joint,the main muscles force around the elbow joint,muscles activity of upper limb,and so on were obtained.The analysis shows that the value of joint torque,joint reaction force,muscle force and muscle activity in upper limb horizontal state are higher than that in vertical state.Through the obtained data,they can be helpful for better understanding the relation between upper limb movements and the exerted force,meanwhile they can provide the kinematics data for subsequent finite element analysis.(2)Using the laser scanner and the pressure measuring system of F-Scan and FSA(Force Sensing Array),the contact area and contact pressure of the mouse and wrist have been measured and data have been processed during different mouse operations.Through the scanner scanning,the regional areas of the mouse and wrist contacting with the scanner were obtained while different states during mouse operating;Through the pressure measuring experiments of F-Scan and FSA pressure,the contact pressure,contact area,contact force and the peak of contact pressure varied with time have been obtained for mouse and wrist with the desktop during the whole process of mouse clicking,and their results were compare and analyzed.These data can provide the biomechanical basis for the clinical diagnosis of MSDs and injury of wrist,and formulation and assessment of rehabilitation schemes.The result shows that,the peak value of contact pressure is appeared nearby the pisiform bone of wrist,and through putting the forearm on the desktop as much as possible,the contact pressure of the wrist can be effectively reduced,or using the appropriate mouse cushion can also get the certain effect to decrease the contact pressure of wrist,and consequently to reduce the wear of wrist with desktop and the compressing to blood vessels and nerves of wrist,and to reduce the risk of suffering from the wrist MSDs.(3)Based on the scanned data of volunteer’s CT and MRI,a 3D finite element model of human upper limb musculoskeletal system was constructed,including humerus,ulna,radius,and all hand bones,etc.,articulate cartilages of each joint and main ligaments of elbow joint,and the soft tissues of the upper limb(including skin,muscles,tendons and fascia,etc.).Through simulation and analysis,the contact pressure distribution on each joint surface have been investigated under the motions of normal elbow fexion and forearm supination,and meanwhile the stress distribution of bones,main ligaments,and soft tissues have been researched in different states of these processes.Through the related comparison and analysis,the results of finite element analysis have the almost same tendency with the analysis of inverse dynamics,and the established model was verified with the validity and reliability.On the basis of finite element model of musculoskeletal system of human upper limb,a simplified finite element model of mouse interacting with desktop was built in order to simulate and analyze the contact conditions among hand,mouse,wrist and desktop under the gravitational load and different contacting regions between forearm and desktop,and the results were compared and analyzed with the experimental measuring.The results of analysis show that only the wrist contacting with the desktop,the contact pressures of wrist with desktop,and each joint of wrist and elbow are all the maximal,and with the increasing contact region of forearm with desktop,the contact pressure of each component is reduced,while the three-quarter forearm and whole forearm contacting with desktop,the contact pressure is almost the same,so comprehensive analysis of various factors,when the mouse operation,the recommended posture is the desktop supporting three-quarters forearm as far as possible.The obtained contacting data can be biomechanical research basis of joint contact of upper limb,tissues properties of upper limb and diagnosis and treatment of musculoskeletal disorders and injury.The developed 3D finite element analysis model of human upper limb musculoskeletal system can be a biomechanical analysis platform for human upper limb,and it can be used to study the characteristics of sports biomechanics for bones of upper limb,i.e.the simulation and analysis of the daily movements and sports have important meaning to understand the effects of daily movements on the upper limb.It can also be employed to analyze the joint contact conditions of each joint of upper limb and to investigate the effects of movement on the musculoskeletal system of upper limb.It can be applied to analyze the effects of mouse operations on the wrist joints from the perspective of biomechanics.It can be used to research the man-machine engineering and human ergonomics related with upper limb,for instance,the mouse personalised designing,desktop ergonomics designing,robots designing of sports rehabilitation,and so on.It can be used to provide the certain biomechanical guidance for clinical diagnosis and treating of MSDs for upper limb in order to effectively prevent the MSDs and musculoskeletal system injury of upper limb.It can also be applied to formulate personalized rehabilitation schemes for patients.The establishment of this upper limb finite element model also has important academic meaning and application value to conduct the related investigation on MSDs and injury of upper limb including CTS. |
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