Biomechanical Comparison of Locking Plate and Cancellous Screw Techniques in Medial Malleolar Fractures: A Finite Element Analysis

Abstract

As the commonly used fixation strategy of medial malleolar fractures, cancellous screws (CS) have been challenged for instability, bone destruction, and metal prominence. It is still unclear whether a locking compression plate (LCP) is a better choice in such fractures. Our purpose is to compare the mechanical efficacy of LCP with traditional 4.0-mm CS for transverse, oblique, and vertical medial malleolar fractures by using finite element analysis. In this study, 3-dimensional models of the distal tibia were reconstructed from a computed tomography scan of a young healthy male adult. Conditions included 3 fracture lines at 30°, 60°, and 90°; 2 groups of fixation (LCP and CS); and 3 adduction loads of 300, 500, and 700 N applied to the medial malleolar joint surface. The proximal part of the tibia was fixed for all degrees of freedom. The fracture displacements of the LCP were smaller than those of CS (p < .05). The stiffness of the LCP constructs was much higher than that of the CS constructs, especially in the 90° fractures (490.3 versus 163.6 N/mm). The mean stress around the CS was higher than that in LCP for 60° and 90° fractures, but there was no difference for 30°. Maximal bone stress increased (19.84 to 50.86 MPa) and concentrated on cortical bone in LCP, whereas it concentrated on cancellous bone in CS. The results showed that LCP could improve stability, preventing bone destruction in oblique and vertical medial malleolar fractures. However, in transverse fractures, CS provides sufficient stability, with no need to use LCP.