The answer behind the PFNA 'cut through' phenomenon

• Main Author: Tan, Li Jin
• Other Authors: Chou Siaw Meng
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/157618
• Institution: Nanyang Technological University

Cut-through failure is a perplexing phenomenon that is becoming more common in the treatment of intertrochanteric hip fractures with the PFNA implant. The goal of this study is to conduct a biomechanical investigation into the role of bi-directional cyclic loading on the cut-through phenomenon. Sawbones’ low density polyurethane foam proximal femur models, Synthes PFNA implants, and a customised fixation equipment set were used to create the bone-implant construct for testing. The fixture for the bi-directional cyclic load, as well as the base fixture for securing the construct to the Shimadzu Universal Testing Machine 10kN were created specifically for this investigation. In each synthetic bone, a stable intertrochanteric fracture (AO31-A1) was simulated. Bi-directional Cyclic loading of 720 N compression and 120 N tension were utilized to mimic the gait cycle of a human femur. A break on the femoral head indicated that the helical blade had cut axially through the femoral head and reached the cortical bone, indicating a cut-through failure. Four femur bones were used. The number of cycles it takes for each bone to fail was recorded. All bones showed consistent reproduction of the medial migration. An analysis of how the bone failed were recorded and discussed in report. The objective of this research is to perform a controlled biomechanical investigation to determine why and how ‘cut throughs' occur in the PFNA implant.