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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A B S T R A C T Sliding contact of a rigid rough surface with a semi-infinite medium including a horizontal subsurface crack was investigated by using linear elastic fracture mechanics and finite element method (FEM). The fractal geometry was used to characterize the rigid rough surface. The propagation of crack was studied with the shear and tensile stress intensity factors. The effect of surface roughness, crack length to depth ratio and friction at the contact and crack interfaces was investigated by using the FEM. It was shown that increasing friction coefficient at the contact interface increases both K II and K I .stress intensity factors x = Asperity distance from the crack center (r,θ ), (x, y) = Cylindrical polar and cartesian coordinates at the crack tip μ = Coefficient of friction at contact interface μ c = Coefficient of friction at the crack interface P = Compressive force d = Crack depth from the surface L s = Cut-off length V = Cylindrical polar coordinates and sliding direction of rough surface γ = A parameter controlling density of frequencies in the surface profile E = Elasticity modulus D = Fractal dimension G = Fractal roughness n = Frequency index c = Half-crack length δ = Interference K I = Opening mode stress intensity factor L = Sample length K II = Shear mode stress intensity factor z(x) = Surface height function I N T R O D U C T I O NAs two rough surfaces touch each other, the contact occurs at multiple asperities of arbitrary shapes, varying sizes and heights. This is commonly referred as asperity contacts. When relative motion between two sur-faces is occurred, the adhesion of these asperities, stresses developed at the interface and in the subsurface and other sources of surface interactions contribute to friction force. Subsequent surface interactions result in the formation of wear particles and eventual failure. Therefore, studies on contact modelling of two rough surfaces have particular importance in the area of friction and wear. 816

The aim of this study was to investigate the stresses on the plate and the clavicle in the standard clavicular hook plate model and the clavicular hook plate models with a coracoclavicular (CC) screw by finite element analysis (FEA). Materials and methods:The FEA models were created with the combination of acromion, clavicle, coracoid process, 8-hole clavicular hook plate and screw components. Model 1 was created as a standard clavicular hook plate model and plates were implanted to the clavicle and the acromion by six locking screws. Model 2 was created by a cortical screw placed in the coracoid process through the third hole of the plate (CC screw) and fixation of hook plate by five locking screws. The upward-pull force was applied to clavicle at the insertion of sternocleidomastoid muscle with three axes. The stress exerted by acromion on the hook of the plate, stresses on the plate, clavicle, and CC screw were analyzed.Results: When the screw holes were compared, in Model 1, the highest stress was found in the last hole of the plate. In Model 2, the highest stress was detected on the CC screw. The stress on the clavicle was found to be 0.14 Mpa in Model 1 and 0.21 Mpa in Model 2. In Model 1 and Model 2, the stress exerted by acromion on the subacromial part of the plate was found to be 2.05 KPa and 1.66¥10-6 KPa, respectively. Conclusion:The results of this study show that addition of CC screw to the standard clavicular hook plate shares the loading and reduces the stress on the hook of the plate.

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Objectives This study aimed to evaluate the performance of four different fixation techniques for Pauwels type III femoral neck fractures considering the fracture morphology in the sagittal plane. Materials and methods We constructed three different fracture morphologies in the sagittal plane in Pauwels type III femoral neck fractures: posteriorly angled at 20°, neutral, and anteriorly angled at 20°. We set up four fixation devices, including three cannulated screws (3CS), a dynamic hip screw with an antirotational screw (DHS+CS), a proximal femoral locking plate (PFLP), and three cannulated screws with a medial buttress plate (3CS+MBP). The twelve models were created and analyzed using the finite element analysis. Results The finite element analysis revealed that 3CS+MBP yields better results in total vertical and rotational displacements, regardless of the fracture angle in the sagittal plane. For the anterior and posterior angled fractures in the sagittal plane, the PFLP was superior to the DHS+CS. However, the DHS+CS exhibited less displacement than the PFLP in the neutral fracture line in the sagittal plane. The 3CS group demonstrated poor mechanical stability for Pauwels type III fractures. Conclusion Regardless of the fracture line in the sagittal plane, the 3CS+MBP showed better biomechanical behaviors than the 3CS, DHS+CS, and PFLP. In addition, in contrast to the DHS+CS, the PFLP displayed less vertical and rotational displacement in the anterior and posterior fracture lines in the sagittal plane.

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This article is not a study with human participants. There are no experiments on animals. There is no identifying information of participants. Etik Kurul Onayı: Bu makale, insan katılımcılarla yapılan bir çalışma değildir. Hayvanlar üzerinde deney yoktur. Katılımcıların tanımlayıcı bilgisi yoktur.