Abstract
BackgroundMore elderly patients are suffering from intertrochanteric fractures. However, the choice of internal fixation is still controversial, especially in the treatment of unstable intertrochanteric fracture; thus, previous implants continue to be improved, and new ones are being developed. The purpose of our study was to compare the biomechanical advantages between the zimmer natural nail (ZNN) and proximal femoral nail antirotation-II (PFNA-II) in the treatment of elderly reverse obliquity intertrochanteric fractures.MethodsA three-dimensional finite element was applied for reverse obliquity intertrochanteric fracture models (AO31-A3.1) fixed with the ZNN or PFNA-II. The distribution, peak value and position of the von Mises stress and the displacement were the criteria for comparison between the two groups.ResultsThe stresses of the internal fixation and femur in the ZNN model were smaller than those in the PFNA-II model, and the peak values of the two groups were 364.8 MPa and 171.8 MPa (ZNN) and 832.3 MPa and 1795.0 MPa (PFNA-II). The maximum amount of displacement of the two groups was similar, and their locations were the same, i.e., in the femoral head vertex (3.768 mm in the ZNN model and 3.713 mm in the PFNA-II model).ConclusionsThe displacement in the two models was similar, but the stresses in the implant and bone were reduced with the ZNN. Therefore, the ZNN implant may provide biomechanical advantages over PFNA-II in reverse obliquity intertrochanteric fractures, as shown through the finite element analysis. These findings from our study may provide a reference for the perioperative selection of internal fixations.
Highlights
With the increase in the elderly population, the incidence of intertrochanteric fractures caused by low-energy trauma is increasing as well [1]
The stress was concentrated at the distal locking screw of each group, and the peak von Mises stresses were 364.8 Mises peak stress of the implant (MPa) and 832.3 MPa in the zimmer natural nail (ZNN) and proximal femoral nail antirotation-II (PFNA-II), respectively (Table 3 and Fig. 3)
The stress was concentrated at the distal transfixation screw hole of each group, and the peak von Mises stresses were 171.8 MPa and 1795.0 MPa in the ZNN and Proximal femoral nail antirotation (PFNA)-II, respectively (Table 3 and Fig. 4)
Summary
With the increase in the elderly population, the incidence of intertrochanteric fractures caused by low-energy trauma is increasing as well [1]. After conducting a multi-centre prospective study, Sawaguchi et al [7] concluded that PFNA-II is safe and effective in patients with unstable femoral intertrochanteric fractures, but the short PFNA-II is a straight nail and still does not match the femur to some extent. To solve this problem, a new implant called the ZNN was developed (Zimmer, Germany). The purpose of our study was to compare the biomechanical advantages between the zimmer natural nail (ZNN) and proximal femoral nail antirotation-II (PFNA-II) in the treatment of elderly reverse obliquity intertrochanteric fractures
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