Dynamic scapulothoracic stabilization system desing

Human shoulder joint is the most complex joint of the body, having the largest range of motion. Shoulder Joint complex consist of humerus (arm), clavicle (collarbone), scapula (shoulder blade), costa (rib) and sternum (rib cage) bones. This wide movement ability of the shoulder joint is enabled by glenohumeral (GH), acromioclavicular (AC), sternoclavicular (SC) and scapulothoracic (ST) joints. The ST joint is one of these aforementioned joints, that has a great significance in terms of shoulder kinesiology .Due to some specific pathologies the ST motion may directly or indirectly affect the GH joint functions. Scapulothoracic fusion (STF) may be an alternative and salvage procedure in the treatment of above mentioned disorders which could not be treated conservatively or using other dynamic surgical techniques. The primary indication of STF is pain relief; the secondary is improvement of function. We hypothesized that; STF may increase the loadings on GH, AC joints and ligaments by affecting the scapular motion, which is important for scapulohumeral rhythm. So new systems may be required to decrease loadings on shoulder girdle and increase the functional results. The aim of this thesis study is to research the distensions which occur in GH and AC joints after STF surgery by using the finite elements analysis method and to evaluate the feasibility of a new dynamic scapulothoracic stabilization (DSS) system with finite elements analysis method by designing a new implant which could be used instead of STF surgery. In this study, three-dimensional reference shoulder model was created by using computed tomography images consisting of healthy human shoulder junction sections with MIMICS® program. Second model was formed by rotating the scapula on this model in a straight angle compared to STF surgery and stabilizing it to the ribs, afterwards newly-designed implanted model which was suitably placed on the reference model was formed. After modelling soft tissue and cartilage structures in Cad program, all three models were analyzed by using the finite elements program. According to the results obtained from the thesis study, it was observed that STF surgery affects ligaments and cartilage structures negatively, maximum equivalent stresses obtained in case of DSS system were closer to the reference model and the durability of the newly-designed implant was sufficient in terms of usability. In conclusion, DSS system which ensures stabilization as well as more movement was evaluated as precursor implant planned to be produced with this purpose and positive results were obtained for its production.