Finite element analysis of six distinct fixation devices for vertically oriented femoral neck fractures

Vertically oriented femoral neck fractures are a challenge for orthopedic surgeons, and the complication rates are also high. Recently, several innovative devices have been proposed, such as the proximal femoral bionic nail, InterTAN, and medial buttress plate combined with cannulated screws, to increase the stability of fixation. However, the differences among these innovative devices need to be addressed.

This study aimed to compare the stability of the proximal femoral bionic nail, InterTAN, and medial buttress plate combined with cannulated screws for vertically oriented femoral neck fractures. Additionally, traditional fixation devices-including three parallel cannulated screws, a compression hip screw system, and a proximal femoral nail-were included for comparison, resulting in a total of six distinct devices evaluated in this study.

A finite element model of a femoral neck fracture fixed with the six internal fixation devices was created. Furthermore, two different fracture conditions-with and without a 1-mm fracture gap-were considered. The maximum loading during level walking was applied to the model for comparison.

The results indicated that the InterTAN has the best ability to maintain the gap and prevent collapse. Under the fracture gap condition, the peak displacement of the femoral head was smaller in the innovative devices compared to the traditional ones. Specifically, the peak displacements were 1.98 mm for the medial buttress plate combined with cannulated screws, 2.12 mm for the proximal femoral bionic nail, and 1.16 mm for the InterTAN system. The von Mises stress in the medial buttress plate was also the highest among the devices, with values of 1000 MPa with the gap and 1477 MPa without the gap.

Based on the present results, the medial buttress plate combined with cannulated screws, proximal femoral bionic nail, and InterTAN are recommended for cases without a fracture gap, while the InterTAN is recommended for cases with a fracture gap to prevent bone shortening.