3-D Modeling And Biomechanics Analysis Of The Human Acromioclavicular Joint

Shoulder is one of the most complex and maximum activity structure joints of thehuman body, the acromioclavicular joint (AC joint) as an important part of the shoulderplays an essential role. In recent years, many scholars at home and abroad are using thefinite element method combined with the bio-medical approach to the study of humanvertebral body and lower extremity, less research applied to the AC joint. At present, as Iknown, the study based on establishment of three-dimensional finite element model andstresses distribution of the AC joint in domestic is seldom．Therefore, this paper aims torebuild the three-dimensional model of the AC joint and its mechanical analysis.In this study, we have successfully built up a three-dimensional solid model of thescapula and clavicle using software of Mimics, this model has not only clear images,smooth outer surface,realistic shape,relative accurate spatial location,any angle andany profile observed, but also itself can be used as electronic version model in learningregional anatomy. And according to the size of the AC joint ligaments and its attachmentpositions we have establish its model.In addition, we have built up the three-dimensional finite element model of the ACjoint by software of Ansys. Through three-dimensional finite element analysis found that:during humeral glenoid fossa external rotation of 30°,60°,90°and 120°,the VonMises stress of AC joint reaches the maximum at 90°, the maximum stress is in theclavicle, the minimum stress is in the ligaments. Clavicle stress concentration is inthe1/3,this matches with the clinical phenomena. Scapular stress concentration is inmargo lateralis,collum scapulae and spina scapulae , so in the upper arm externalrotation ,the margo lateralis,collum scapulae and spina scapulae play a role of"beam"supporting when the stress transfers , while the fossa supraspinata,fossainfraspinata and fossa subscapular can't afford a major role; and in the four ligaments,stress is maximum in the AC ligament, very small in the coracoacromial ligament(italmost does not work), so in repair surgery of the AC joint,the AC ligament should beconsidered firstly. Finally, using the digital cameras close-range photogrammetry method we measurethe displacements of a few key points in the AC joint under different loadings. Thismethod is low cost, work less, simple, and can simultaneously measure multipleobservation points,in a certain range of accuracy it has a wider application value.