The Development of a Newly Designed Interlocking Nail for Femoral Varus Correction Osteotomy

This study aims to develop a newly designed intramedullary interlocking nail for femoral varus osteotomy in treatment of children’s hips dysplasia. Femoral varus osteotomy is one of the most common operations in children’s hips to correct the dysplasia and deformity from neuromuscular disease, developmental dysplasia of the hip, Perthes’ disease, trauma and infection. The universal implant for varus osteotomy is angled blade plate in which the femoral neck is fixed by one smooth blade. However, the postoperative outcome indicates that blade loosening, malunion and nonunion are not uncommon. Besides, a big wound and muscle dissection are required to implant the plate. Prominence at trochanteric area by the plate is a common complain from the patients and parents. From viewpoint of biomechanics, a much shorter moment arm will be expected with use of an intramedullary interlocking nail, as compared to angle blade plate, to perform the femoral varus correction osteotomy. Consequently, a more stable and a higher compressive resistance of the postoperative femur will be achieved with use of an intramedullary interlocking nail. Therefore, this study aims to design a new intramedullary interlocking nail with the following features: 1. Superior biomechanical performance due to short moment arm; 2. More stable fixation due to bicotex purchase. 3. Without prominence at trochanteric area by the plate. 4. Easy control of the femoral anteversion . The vulnerability of blade plate fixation, technical demanding and the prominence at trochanter are unsolved problems after world-wide application of the plate for around 30 years. A new interlocking nail is specially designed for the femoral varus osteotomy. The nail offers stronger fixation by purchasing bone cortex and biomechanical advantage of intramedullary nailing. The other advantages include smaller wound, less trochanter prominence, and easy to control the anteversion of femur. In current study, commercial available femora will be used to perform in vitro biomechanical test. Twenty four (24) synthetic femora will be used and divided into two groups (blade plate and intramedullary interlocking nail). By using MTS testing machine, biomechanical experiments including: (1) Static and dynamic compressive test and (2) Static and dynamic torsional test will be performed. The biomechanical performance between a traditional blade plate and an intramedullary device for femoral varus correction osteotomy will be compared accordingly.

Project ID:PB9808-3521
External Project ID:NSC98-2622-E182-065-CC3