Comparative biomechanical evaluation of medial support plating in Pauwels type III femoral neck fractures: A finite element analysis.

OBJECTIVES

This study aims to evaluate the biomechanical contribution of medial support plating compared to isolated screws and to determine the impact of plate design (one-third tubular vs. mini-plate) and distal screw configuration (unicortical vs. bicortical) on construct stability.

MATERIALS AND

METHODS

Five finite element models were analyzed in this study: three cannulated screws (CS) alone (control), and CS augmented with either a one-third tubular plate or a 2.4-mm mini-plate. For the plated models, the distal fragment was fixed using either unicortical or bicortical screws to isolate the effect of cortical purchase. A 1,400 N axial load was applied to simulate the single-leg stance phase of gait. Fracture micromotion, femoral head displacement, and von Mises stress distribution were recorded.

RESULTS

Medial support plating substantially improved construct stability compared to screws alone, reducing femoral head displacement and fracture gap movement. Notably, no significant biomechanical differences were observed between unicortical and bicortical fixation configurations for either plate type. Both the one-third tubular plate and the 2.4-mm mini-plate provided equivalent rigidity. Although mini-plates exhibited higher internal stress concentrations, values remained below the yield strength of the material.

CONCLUSION

Bicortical fixation provided no additional mechanical advantage over unicortical fixation in improving construct stability or reducing implant stress. Therefore, the primary determinant of stability is the medial buttress effect itself; once this is established, neither the plate profile nor the screw length significantly alters the biomechanical outcome, suggesting that unicortical fixation with low-profile plates provides sufficient mechanical stability.