Generating accurate simulations of the forces in the Glenohumeral joint is essential for investigation of normal and pathologic Shoulder function. It forms the basis for evaluating fracture treatment, joint replacement design and fixation. However, due to its complex anatomy and large range-of-motion, measuring the dynamic in-vivo forces and kinematics of the Glenohumeral joint remains a challenging problem in the field of biomechanics.This study shows the development and validation of a new testing medium for the Glenohumeral joint. The study uses a combined approach of in-vitro and in-silico testing and validates against previous data. This is achieved using a mechanical testing rig and finite element model which both closely represent the in-vivo Glenohumeral physiological characteristic including; geometry, muscular loading patterns, joint range-of-motion and external loadings. The mechanical model uses two instrumented implants based on current gold standard in-vivo testing. The two head types used are a Stem implant and a resurfacing head type implant. Comparison is made between the two head types as testing mediums for in-vitro testing. It is shown the resurfacing head more closely maintains the natural properties of the bone. Testing displays the significant advantages of in-vitro and in-silico testing over in-vivo testing.Validation is achieved by comparing simulated functional movements and activities of daily living to previous published data. When compared with previous data, recorded results from the mechanical testing rig shows high conformity. Comparison shows -3.95% and 4.14% error during 45° abduction with the resurfacing and stem implants respectively. Activities of daily living display similar loading patterns but lower maximum recorded force agreement. This has highlighted problems with unpredictable and complex muscular combinations when assessing complex movements. FE results show similar loading patterns and stress areas to previous data but record lower maximum forces than previous in-vivo data. Force and stress results from the FE model highlight the significant force increase external loads apply to the joint complex. Cross-validation between the mechanical testing rig and FE model shows high conformity and similar loading patterns. The developed medium is shown to be successfully validated against “gold standard” in-vivo data and other previous studies.Research experiments are used to illustrate the variety of testing possible with the developed medium and to further develop and validate the design. Research into trauma, injury and fixation is discussed and joint forces measured. This data lays a foundation for future testing using the developed test medium.The testing medium provides repeatable and reproducible results for forces within the Glenohumeral joint. This can now be used to further understand joint kinematics, injuries, fracture prorogation and fixation. It will also provide a valuable training aid for a complex joint. Better understanding, testing and training of new techniques, tools and traumas is now possible. This will aid in reducing injury prevalence, severity, healing time and ultimately improving patient quality of life.
|Date of Award||7 Mar 2014|
|Supervisor||Farhad Nabhani (Supervisor) & Simon N.B. Hodgson (Supervisor)|