Bicortical screw placement and microdamage in medial buttress plates in the management of Pauwels type III femoral neck fractures: A scanning electron microscopy-based analysis.

OBJECTIVES

This study aims to investigate the microstructural effects of distal bicortical screw placement in medial buttress plate (MBP) constructs using scanning electron microscopy (SEM).

MATERIALS AND

METHODS

Ten synthetic femur models with standardized Pauwels type III fractures were divided into two groups. All specimens received fixation with three cannulated screws in an inverted triangle configuration. Group A received a MBP fixed with four unicortical screws. Group B received the same construct, except for the most distal screw was inserted bicortically. All specimens underwent combined axial and torsional cyclic loading, followed by load-to-failure testing. Plates were, then, analyzed under SEM to assess deformation and microdamage. A semi-quantitative scoring system was used to compare the severity of microstructural changes between groups.

RESULTS

The SEM analysis revealed significantly more microdamage in Group B compared to Group A (median deformation scores: 4 vs. 2; p=0.0181). Plates with bicortical screw placement showed localized plastic deformation, microcracks, and in some cases, complete fractures, particularly at the bent midsection of the plate. In contrast, unicortical plates showed only mild surface irregularities without structural failure.

CONCLUSION

Although distal bicortical screw placement may enhance initial mechanical stability, it also increases the risk of microstructural damage in MBPs, potentially compromising long-term durability. These findings underscore the importance of optimizing screw configuration to balance stability with implant longevity in the treatment of vertically unstable femoral neck fractures.