Effect of three cannulated compression screws combined with an obstructing screw on the biomechanical performance of pauwels type III femoral neck fractures: a finite element analysis.

Background: Obstructing screws (OS) are an effective surgical method for treating Pauwels type III femoral neck fractures. This study compared the mechanical properties of various surgical techniques for treating such fractures using finite element analysis.

Methods: An ideal finite element model of the femur was established based on computed tomography scans of healthy individuals. Four internal fixation methods were designed: the three cannulated compression screws (3CCS) group, 3CCS + horizontal screw (3CCS + HS) group, 3CCS + OS (3CCS + OS) group, and 3CCS + medial buttress locking plate (3CCS + BL) group. The same pressure direction and magnitude were applied to observe the stress distribution in the femur under different surgical techniques.

Results: The stress distribution, fracture displacement, and femoral stiffness varied across the internal fixation groups. The 3CCS + OS group exhibited the most balanced femoral stress distribution (126.49 MPa), effectively dispersing stress on the CCS. Its overall femoral stiffness (510.95 N/mm) and fracture displacement (4.11 mm) were second only to the 3CCS + BL group (554.09 N/mm, 3.79 mm) and significantly better than the 3CCS (441.18 N/mm, 4.76 mm) and 3CCS + HS (449.68 N/mm, 4.67 mm) groups.

Conclusions: The combination of CCS and antishear OS demonstrated significant mechanical advantages and lower biological interference in the treatment of Pauwels type III femoral neck fractures. This method not only provides excellent mechanical stability but also ensures biological safety, offering benefits such as simplicity of operation, minimal invasiveness, and a low risk of complications. It holds great potential for widespread clinical application.