Fracture fixation with two locking screws versus three non-locking screws

Abstract

Objectives We aimed to further evaluate the biomechanical characteristics of two locking screws versus three standard bicortical screws in synthetic models of normal and osteoporotic bone. Methods Synthetic tubular bone models representing normal bone density and osteoporotic bone density were used. Artificial fracture gaps of 1 cm were created in each specimen before fixation with one of two constructs: 1) two locking screws using a five-hole locking compression plate (LCP) plate; or 2) three non-locking screws with a seven-hole LCP plate across each side of the fracture gap. The stiffness, maximum displacement, mode of failure and number of cycles to failure were recorded under progressive cyclic torsional and eccentric axial loading. Results Locking plates in normal bone survived 10% fewer cycles to failure during cyclic axial loading, but there was no significant difference in maximum displacement or failure load. Locking plates in osteoporotic bone showed less displacement (p = 0.02), but no significant difference in number of cycles to failure or failure load during cyclic axial loading (p = 0.46 and p = 0.25, respectively). Locking plates in normal bone had lower stiffness and torque during torsion testing (both p = 0.03), but there was no significant difference in rotation (angular displacement) (p = 0.84). Locking plates in osteoporotic bone showed lower torque and rotation (p = 0.008), but there was no significant difference in stiffness during torsion testing (p = 0.69). Conclusions The mechanical performance of locking plate constructs, using only two screws, is comparable to three non-locking screw constructs in osteoporotic bone. Normal bone loaded with either an axial or torsional moment showed slightly better performance with the non-locking construct. Article focus  To further elucidate biomechanical standard guidelines for diaphyseal or meta-physeal fracture fixation with non-locking screws and locking screws  To investigate the clinical dilemma faced when difficulties such as limited length for fixation in juxta-articular fractures or fractures with too short a metaphyseal fragment are encountered  To specifically determine whether two locking screws, with minimal spacing, would provide a similar mechanical performance to the more traditional configuration of three non-locking bicortical screws with minimal spacing Key messages  The biomechanical capabilities of a two-screw locked construct is comparable to those of a three-screw non-locked construct in osteoporotic bone, thus providing adequate fixation of short metaphyseal segments in juxta-articular fractures Strengths and limitations  The main strength is the biomechanical comparison made between non-locking Freely available online