Positive medial cortical support versus anatomical reduction for trochanteric hip fractures: Finite element analysis and biomechanical testing.

BACKGROUND AND OBJECTIVES

The anatomical reduction (AR) is usually considered the best option for fractures. Nevertheless, in unstable trochanteric hip fractures (UTHF), previous clinical reports found that the positive medial cortical support (PMCS, an over-reduction technique) attained higher mechanical stability, but this challenging clinical finding still needs experimental validation.

METHODS

This study constructed in-silico and biomechanical PMCS and AR models, with the use of the most clinically-representative geometry design of fracture models, the multi-directional design in FE analysis, and the subject-specific (osteoporotic) bone material properties, to make the models better mimic the actual condition in clinical settings. Then multiple performance variables (von-Mises stress, strain, integral axial stiffness, displacement, structural changes, etc.) were assessed to uncover details of integral and regional stability.

RESULTS

Among in-silico comparison, PMCS models showed significantly lower maximum displacement than AR models, and the maximum von Mises stress of implants (MVMS-I) was significantly lower in PMCS models than in AR models (highest MVMS-I in -30°-A3-AR of 1055.80 ± 93.37 MPa). Besides, PMCS models had significantly lower maximum von Mises stress along fracture surfaces (MVMS-F) (highest MVMS-F in 30°-A2-AR of 416.40 ± 38.01 MPa). Among biomechanical testing comparison, PMCS models showed significantly lower axial displacement. Significantly lower change of neck-shaft angle (CNSA) was observed in A2-PMCS models. A fair amount of AR models converted into the obvious negative medial cortical support (NMCS) condition, whereas all PMCS models kept the PMCS condition. The results were also validated through comparison to previous clinical data.

CONCLUSIONS

The PMCS is superior to the AR in the UTHF surgery. The current study opens up the second thought of the role of over-reduction technique in bone surgery.