• Jie Wang, Jian-Xiong Ma, Bin Lu, Hao-Hao Bai, Ying Wang, and Xin-Long Ma.
• Department of Orthopaedics, Tianjin Medical University General Hospital, No. 154, Anshan Street, Heping District, 300052, Tianjin China; Institute of Orthopaedics, Tianjin Hospital, No. 406, Jiefang Nan Street, Hexi District, 300211 Tianjin, China.
• Orthop Traumatol Sur. 2020 Feb 1; 106 (1): 95-101.

BackgroundThe optimal type of fixation implant for managing subtrochanteric fractures (STFs) is debated, as uncertainty continues to surround the comparative biomechanical performance of the proximal femoral nail antirotation (PFNA), proximal femoral locking plate (PFLP), and reverse less invasive stabilisation system (LISS). No studies have used finite element analysis (FEA) to compare these three devices. The objective of this study was to use FEA to compare the PFNA, PFLP, and LISS used to treat STFs based on the following criteria: (1) stress distribution on the femur and implant, (2) peak stress and stress on the medial side of the femur near the fracture site, and (3) smallest axial displacement of the femoral head.HypothesisOf the three implants, the PFNA has the best biomechanical performance when used for STF fixation.MethodsFEA was used to assess synthetic bone responses to the three implants used to fix three STF types, namely, Seinsheimer I, III, and IV, characterised by increasing bone loss and/or comminution with subsequent instability. Loading was with 1400N axial compression force.ResultsThe LISS and PFLP exhibited similar biomechanical properties in all three fracture types. However, with the Seinsheimer IV fracture, the triangular configuration of the PFLP resulted in stress concentration at the medial and lateral sides of the implant junction. With the Seinsheimer I and III fractures, the PFNA resulted in higher peak stress (183.85MPa and 364.58MPa, respectively) compared to the PFLP (102.90MPa and 177.52MPa) and LISS (116.55MPa and 227.97MPa). With the Seinsheimer IV fracture, peak stress was highest with LISS (2310.40MPa) and was higher with PFLP (2054.90MPa) than with PFNA (1313.30MPa). With the Seinsheimer I and III fractures, the axial femoral head displacement was greater with the PFNA (0.74mm and 1.13mm, respectively) than with the PFLP (0.48mm and 1.02mm) and LISS (0.52mm and 0.92mm). With the Seinsheimer IV fracture, in contrast, the PFNA produced less axial femoral head displacement (4.1mm) compared to the PFLP (12.03mm) and LISS (16.56mm).DiscussionWith unstable (Seinsheimer IV) STFs, fixation stability was better with the PFNA compared to the PFLP and LISS. In contrast, with stable STFs (Seinsheimer I and III), the PFLP and LISS offered greater stability, with similar biomechanical effects. However, with Seinsheimer III fractures, the stress on the implant-femur interface was greater with the LISS.Level Of EvidenceIV, basic science study.Copyright © 2019 Elsevier Masson SAS. All rights reserved.

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