Femoral calcar double-supported screw fixation enhances biomechanical stability in Pauwels type III femoral neck fractures: a comparative biomechanical study.

Objectives: This study proposed a novel fixation method - femoral calcar double-supported screw fixation (FCDSF) - and evaluated its biomechanical performance. The fixation's mechanical properties were assessed and compared with those of inverted triangular parallel cannulated screws (3CS) and biplane double-supported screw fixation (BDSF) for Pauwels type III femoral neck fractures (FNFs).

Methods: Fifty-four synthetic femur models were allocated into three reduction groups simulating positive buttress, anatomical reduction, and negative buttress conditions. Each group was further divided into three subgroups (n = 6), fixed with FCDSF, 3CS, or BDSF. Torsional tests measured torque at the fracture site under 2° and 4° rotation. Load-to-failure tests were then conducted by applying continuous pressure until failure occurred, and the ultimate loads were recorded.

Results: Under all reduction conditions, FCDSF demonstrated significantly greater torque at both rotation angles compared with 3CS (P < 0.05), while difference with BDSF was not statistically significant (P > 0.05). FCDSF showed superior load-bearing capacity over both BDSF and 3CS across all conditions (P < 0.05). In both the FCDSF and BDSF groups, positive buttress and anatomical reductions provided significantly better resistance to torsion and shear than negative buttress configurations (both P < 0.05), with no significant difference between the two (P > 0.05). In the 3CS group, only the positive buttress configuration showed a significant improvement over the negative buttress (P < 0.05).

Conclusions: FCDSF provides enhanced anti-shear and anti-rotational stability compared with 3CS in managing Pauwels type III FNFs. Negative buttress reduction should be avoided due to its inferior biomechanical performance.