Static Analysis and Fatigue of DHS Implants to Treatment Femoral and Intertrochanteric Neck Fractures Using Ti6Al4V and SS316 Alloys, A Finite Element Analysis

The neck fractures and the femurs intertrochanteric are common complications that are recovered by a multicomponent implant called dynamic hip screw (DHS). In the present study, a standard four-hole DHS with Ti6Al4V (Ti6) and SS316l (SS) alloys for static mode (slow walking) and fatigue mode like normal walking (NW), descending stairs (DS), and falling (FA) by finite elements analysis (FEA) have been evaluated (ANSYS software). The results have been confirmed by similar studies in static mode and maximum Von Mises stress and strain are obtained for Ti6 about 145 MPa and 0.191%, and SS about 196 MPa and 0.121%. Most critical stress points occur in cortical screws, plate holes, compression screws, and lag screws, respectively. DHS components with Ti6 alloy have infinite life in NW and DS, also in FA, they have a finite life (10^7-10^8 cycle) with alternating Von Mises stress (σ_ a max) ~ 425 MPa, while for SS they have finite life in all activities, which NW ~10^7 cycle, DS~10^6 cycle, and even in FA cortical screw life of failure reaches to 98 cycles and σ_ a max = 486 Mpa . The critical regions are the same as the failure regions common in biomechanical and clinical studies. These regions are mainly concentration stress points that lead to DHS failure as the crack grows.