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.