Cement augmentation of the proximal femoral nail antirotation for the treatment of two intertrochanteric fractures - a comparative finite element study

Abstract

Background There are concerns regarding initial stability and cutout effect in proximal femoral nail antirotation (PFNA) treating intertrochanteric fractures. No study have used finite element analysis (FEA) to investigate the biomechanics. This study aimed to compare the cutout effect, stress and displacement between stable (AO31-A1.3) and unstable (AO31-A2.2) intertrochanteric fractures treated by cement augmented PFNA. Methods Four femoral finite element models (FEMs) were constructed and tested under the maximum loading during walking. Non-augmented and augmented PFNA in two different intertrochanteric fractures were respectively simulated, assuming Tip Apex Distance (TAD) < 25 mm within each FEM. The cutout effect, stress and displacement between femur and PFNA were compared in each condition. Results Cutout effect was observed in both non-augmented femoral head and was more apparently in unstable intertrochanteric fracture model. After reinforced by bone cement, no cutout effect occurred in two models. Stress concentration were observed on medial part of intertrochanteric region and the proximal part of helical blade before augmented while were observed on femoral shaft and the conjunction between blade and nail after augmented in both FEMs. Displacement mainly appeared on femoral head and the helical blade tip before augmented while distributed moderately on intertrochanteric region and the upper part of nail after augmented in both FEMs. The maximum stress and displacement value of femur decreased both in stable and unstable model after augmented but was more significantly in the unstable one. The maximum stress and displacement value of PFNA increased both in stable and unstable model after augmented but was more significantly in the unstable one. Conclusion Our FEA study indicated that the cement augmentation of the PFNA biomechanically enhances the cutout resistance in intertrochanteric fracture, this procedure is especially efficient for the unstable intertrochanteric fracture.

Comparison of Curative Effect between PFNA and PCCP in the Treatment of Femoral Intertrochanteric Fractures

“…The PFNA surgical treatment method can complete the corresponding material design according to the specific force principle of the patient's hip joint, which is closer to the patient's negative gravity line, which promotes the patient's load force transmission, and the overall diameter of the main nail is relatively small. Therefore, the joint stability and anti-rotation resistance of the treatment are increased to a certain extent [ 12 , 13 ]. In PFNA, its force transmission is internal expansion and extrusion, so that the medial and lateral sides of the femur can bear the stress in a balanced manner.…”

In Silico Finite Element Modeling of Stress Distribution in Osteosynthesis after Pertrochanteric Fractures

“…Jiang et al’s (2017) [ 22 ] modeling has shown the presence of higher stresses at the nail border and the neck screw using different types of nails, which was confirmed during real-life orthopedic surgery by [ 23 ]. Higher stresses have been reported about the locking screw and the lower part of the nail, being greater in GNF than DHS [ 24 , 25 ]. As with the present findings, modest bone stress has been described at the implant level compared to the implant itself.…”

Two Cannulated Screws Provide Sufficient Biomechanical Strength for Prophylactic Fixation in Adult Patients With an Aggressive Benign Femoral Neck Lesion

“…According to previous studies ( Li et al, 2010 ; Khor et al, 2018 ), the femoral fracture was defined by detecting a failure strain that was initiated and propagated by element deletion as long as the strain of an element reaches the limit. The fracture analyses were performed by LS-DYNA (LSTC, Livermore, CA) software to investigate the biomechanical effect of the failure test ( Zheng et al, 2021 ). Material properties applied for fracture analysis are shown in Table 1 .…”

“…Material properties applied for fracture analysis are shown in Table 1 . The density of cortical bone, cancellous, and Ti6Al–4V titanium was obtained from previous reports ( Dhanopia and Bhargava, 2017 ; Zheng et al, 2021 ). According to the equations between bone density (ρ), Young’s modulus (E), and yield stress (σ) ( Morgan and Keaveny, 2001 ; Duchemin et al, 2008 ), cortical and cancellous bone’s yield stress was calculated respectively.…”