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. 2020;31(3):426-431.
doi: 10.5606/ehc.2020.75113.

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

Kerim Öner  1 , Serhat Durusoy, Alaettin Özer
Affiliations

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

Kerim Öner et al. Jt Dis Relat Surg. 2020.

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.

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Conflict of interest statement

Conflict of Interest: The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Figures

Figure 1
Figure 1. (a) Insertion of additional screw through greater trochanter, nail, and lag screw. (b) New proximal femoral nail antirotation design.
Figure 2
Figure 2. Demonstration of forces applied to models (2460 newtons to femoral head, 1700 newtons to greater trochanter, 771 newtons to lesser trochanter).
Figure 3
Figure 3. (a, b) Demonstration of stress on calcar region. (c) Demonstration of stress on screw inserted through greater trochanter.
Figure 4
Figure 4. (a) Distribution of stress on tip of lag screw in classical PFNA. (b) Distribution of stress on tip of lag screw in new PFNA design. PFNA: Proximal femoral nail antirotation.
Figure 5
Figure 5. Comparison of new and classical proximal femoral nail antirotation designs in terms of stress on tip of lag screw, lag screw-nail junction, and calcar region. PFNA: Proximal femoral nail antirotation.
See this image and copyright information in PMC

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