An in vitro biomechanical comparison between bone plate and interlocking nail: 3-D interfragmentary motion and bone strain analysis in ostectomized canine femurs

In 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 brood 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-corticol 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 gouges in four pairs of the specimen. The mean values of axial and transverse motion were compared using a paired Rest within each group (P <0.05). Slain 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.