An in vitro biomechanical comparison between bone plate and interlocking nail

Abstract

SummaryIn order to compare the interfragmentary motion and bone strains in ostectomized canine femurs, stabilized with either an 8 mm interlocking nail system (IN) or a 10-hole 3.5 mm dynamic compression broad plate (DCP), ten pairs of adult canine femurs with a 25 mm mid-diaphyseal gap were used. The left femurs were implanted with a DCP and eight bi-cortical screws, and the right femurs were implanted with an IN and three screws. Eccentric axial loading and cranio-caudal bending were successively performed on every specimen. Employing an opto-electronic device, interfragmentary (axial, transverse and rotational) motion was measured during non-destructive tests. Bone strains were measured at three elective sites, with strain gauges in four pairs of the specimen. The mean values of axial and transverse motion were compared using a paired t-test within each group (P <0.05). Strain values were compared using a numerical scale and a qualitative analysis. Transverse motion was higher with DCP, whereas axial motion was higher with IN. Bone strain analysis demonstrated lower “stress protection” near the gap with IN. Those comparative results are interpretative: IN may be an interesting alternative implant for unstable diaphyseal femoral fracture repair in dogs.