Design Improvements and Mechanical Evaluations of Orthopaedic Implants for Proximal Femoral Fractures

• Main Authors: Bing-You Lin, 林炳佑
• Other Authors: Ching-Kong Chao
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/5hweba

碩士 === 國立臺灣科技大學 === 機械工程系 === 99 === There are two main methods of the operative treatment of proximal femoral fractures, one is intramedullary, and the other one is extramedullary. Gamma nail (GN) is the standard treatment of intramedullary fixation, and the Dynamic hip screw (DHS) is the standard treatment of extramedullary fixation. These two fracture fixation devices are widely used in the treatment of proximal femoral fractures, but clinical failures of those implants are still to be found. So there were many studies to propose the improved designs to reduce the risk of implant failure for the DHS and GN. The purpose of this study is to develop three-dimensional finite element models to investigate and improve the biomechanical performances of GN and DHS. The FEM was used to evaluate the improvement of DHS and GN in the biomechanical performances under three types of the proximal femoral fractures (neck fracture, subtrochanteric fracture, and subtrochanteric fracture with gap).Improvement of the DHS is increasing length of bone plate, using the locking or non-locking bone plates, and increasing diameter of distal screw. Improvement of GN is increasing length of nail, and increasing length of nail tip. The maximum distortion energy criterion and the maximum deflection criterion were used to discuss the merits of their biomechanical implant performance. Finally, this study will also compare optimum improvement of DHS and GN with DSN. The results showed that DHS with longest length, will increase the risk of the implant failure, but the fracture fixation stability will enhance. However, maximal von Mises stress was found in the distal screw. So the diameter of the distal locking screw was increased to reduce the stress. The above improvement (ILDHS) could increase the stability of fracture fixation and reduce the risk of implant failure. The isthmus can protect the Gamma Nail as the long Gamma nail (LGN) was designed. So the risk of implant failure and the fracture fixation stability can be improved simultaneously. This study showed that the improved designs have greater biomechanical performance in the neck fracture and subtrochanteric fracture. However, in subtrochanteric fracture with gap fracture the risk of implant failure and the fixation stability of ILDHS were inferior to that of the LGN and DSN. It can be speculated that for unstable fractures intramedullary implants are superior than extramedullary implants.