COMPUTER-SIMULATION ANALYSIS OF FRACTURE-DISLOCATION OF THE PROXIMAL INTERPHALANGEAL JOINT USING THE FINITE-ELEMENT METHOD

Stress in a proximal interphalangeal (PIP) joint model was analyzed by the two-dimensional and three-dimensional finite element methods (FEM ) to study the onset mechanisms of the middle phalangeal base fracture . The structural shapes were obtained from sagittally sectioned specim ens of the PIP joint for making FEM models. In those models, four diff erent material properties were given corresponding to cortical bone, s ubchondral bone, cancellous bone and cartilage. Loading conditions wer e determined by estimating the amount and position of axial pressure a dded to the middle phalanx. A general finite element program (MARC) wa s used for computer simulation analysis. The results of the fracture e xperiments compared with the clinical manifestation of the fractures j ustify the applicability of the computer simulation models using FEM a nalysis. The stress distribution changed as the angle of the PIP joint changed. Concentrated stress was found on the volar side of the middl e phalangeal base in the hyperextension position, and was found on the dorsal side in the flexion position. In the neutral position, the str ess was found on both sides. Axial stress on the middle phalanx causes three different types of fractures (volar, dorsal and both) depending upon the angle of the PIP joint. These results demonstrate that the t ype of PIP joint fracture dislocation depends on the angle of the join t at the time of injury. The finite element method is one of the most useful methods for analyzing the onset mechanism of fractures.