A new proximal femoral nail antirotation design: Is it effective in preventing varus collapse and cut-out?

Abstract

Objectives This study aims to compare the mechanical features of the existing proximal femoral nail antirotation (PFNA) system and the new PFNA system that we designed using three-dimensional (3D) finite element analysis. Materials and methods This experimental study was conducted between 2019 and 2020. We constructed two femur models with Arbeitsgemeinschaft für Osteosynthesefragen (AO) type A1 fractures using 3D computed tomography scans. The new and standard PFNA designs were inserted into the femur models and subsequently transferred to the program. We investigated the distribution of stress on the tip of the lag screw, the calcar region, lag screw-nail junction, and the additional screw inserted through the greater trochanter (only present in the new PFNA design) using 3D finite element analysis. Results When the von Mises stress distributions in our models were examined, the maximum stress at the lag screw-nail junction was 18 mpa in the new design PFNA, while it was 20 mpa in the classic PFNA model. The maximum stress at the junction of the additional screw that had greater trochanter inlet with the nail was found as 42.5 mpa. The maximum stress on the calcar region was found to be 10 mpa at the new design PFNA, while it was 13 mpa with 30% increase in the classic PFNA. The stress on the tip of the lag screw was found to be 49 mpa in the classic PFNA design, while in the new design PFNA it was found as 28 mpa with a decrease of more than 40%. Conclusion As per our findings, the new PFNA design leads to reduced stress on the lag screw-nail junction, the calcar region, and the tip of the lag screw.

Treatment of Coronal Plane Femoral Intertrochanteric Fractures with a Microexternal Fixator Combined with Proximal Femoral Nail Antirotation

“…PFNA is a modification of proximal femoral intramedullary nail and has the following advantages when applied to manage femoral intertrochanteric fractures: (a) the original two lag screws changed to one spiral blade, and the percussion method is adopted during the surgery. is not only reduces intraoperative bone loss but also compresses the cancellous bone in the femoral head and increases the anchoring force [16][17][18]. (b) e spiral blade can be locked by itself with strong holding force, which can play the role of antirotation [19].…”

Comparison of Helical Blade Systems for Osteoporotic Intertrochanteric Fractures Using Biomechanical Analysis and Clinical Assessments

“…Both the TFNA and PFNA systems are provided by the same manufacturer with a similar design concept of providing better fixation stability in osteoporotic fractures by impacting the bone on the helical blade. The TFNA was developed to improve its precursor, the trochanteric fixation nail (TFN) system (Depuy Synthes, West Chester, PA, USA), by introducing a lateral relief cut to reduce impingement on the lateral cortex and a bump cut on the mid-portion of the proximal aperture to improve fatigue strength [2,[16][17][18]. Despite its proposed advantages, a recent study by Lambers et al reported 16 cases of TFNA implant breakage, raising concerns about its safety [19].…”

Ideal plate screw configuration in femoral shaft fractures: 3D finite element analysis

“…In this study, 3-dimensional (3D) plates of different sizes, thicknesses and holes were created in Space Claim to be used in analysis. The femur model was obtained from 3D computed tomography scans used in previous studies in the literature [16,17]. In the 3D femur model, a fracture was created by removing the segment in the transverse plan from the femur diaphysis area.…”