An experimental modal analysis of clavicle bending modes

Clavicle fractures are common medical emergencies; their prevention through design of protection systems depends upon understanding injury mechanisms. This work analyzes the bending natural frequencies and mode shapes of the human cadaver clavicles in situ. The method applied includes experimental modal analysis (EMA) techniques on cadaver clavicles and correlates results with previous analyses. The clavicle response to shock depends on mechanical energy transmission between load and bone and requires an understanding of modal characteristics of the clavicle as well as the frequency range of the shock. The loads acting upon the clavicle may be represented by hard impacts (i.e. sport-related hits) or loads with short durations which can excite a wide frequency spectrum. Modal analyses of clavicles have been reported in literature, but those studies were performed on the clavicles isolated from the body. As a result, those analyses found mode shapes dependent upon different boundary conditions than those found in nature. In our study, EMA employed triaxial accelerometers and a force hammer, a testing procedure was developed, and data was analyzed. The EMA was performed with the clavicle supported in situ, and results include the coronal and axial plane first bending modes. Modal parameters obtained serve to design shock mitigation systems.