Biomechanical comparison between standard and inclined screw orientation in dynamic hip screw side-plate fixation: The lift-off phenomenon

Publication date: Available online 17 November 2018Source: Journal of Orthopaedic TranslationAuthor(s): Ivan Zderic, Gaston C. Willhuber, Marc-Daniel Ahrend, Florian Gras, Jorge Barla, Carlos Sancineto, Markus Windolf, Boyko GueorguievAbstractBackgroundCommon failure modes of dynamic hip screw are cut-out and lift-off. To minimize the latter, distal screws can be inserted in different orientation. However, the effectiveness remains controversial. The aim of the study was to biomechanically investigate the influence of distal screw orientation on construct stability.MethodsThirty artificial generic long bones were assigned to three groups (n = 10) and fixed with two-hole dynamic hip screw plates, inserting cortical screws with neutral parallel distal screw orientation (A), divergent screw orientation (B) or convergent screw orientation (C). Starting at 60 N, cyclic loading was applied to the implant tip perpendicular to the lag screw axis with progressive peak load increase at a rate of 0.002 N/cycle until failure. Parameters of interest were construct stiffness and machine actuator displacement after 250, 1000 and 5000 cycles, as well as cycles to failure.ResultsDisplacement after 250, 1000 and 5000 cycles was significantly higher in Group C than in Groups A and B, p < 0.01, whereas no significance differences were observed between Groups A and B, p = 0.20. Specimens in Group C failed after 11584 [standard deviation (SD), 5924] cycles, significantly earlier than ...

Source: Journal of Orthopaedic Translation - November 18, 2018 Category: Orthopaedics Source Type: research