Angle stable interlocking screws improve construct stability of intramedullary nailing of distal tibia fractures: A biomechanical study

Abstract

Introduction Intramedullary nailing is the treatment of choice for most displaced tibial shaft fractures. The ability to maintain a mechanically stable fixation becomes more difficult the further the fracture extends distally or proximally or when unreamed tibial nails are used. We assumed that a new angular stable locking option would provide improved stability and reduced interfragmentary movements in a distal tibia in vitro fracture model. Materials and methods Left and right bones of 8 pairs of human cadaveric tibiae were randomly assigned to either a group with conventional locked or a group with angular stable locked intramedullary nails. Nails of 10-mm-diameter were used after reaming up to 11 mm. A transverse distal osteotomy was performed and the specimens were tested mechanically under eccentric axial load. A video optical measurement system was used to determine the angular displacement of the osteotomy gap during loading. Results Construct stiffness, maximum load of the bone–nail construct and gap angle at 0.5 kN load were measured. The group with the angular stable locking option showed significantly higher stiffness values and reduced fracture gap motion compared to the group with conventional locked nails. Discussion A new angular stable locking option of intramedullary nails provides higher stability in terms of construct stiffness and reduced interfragmentary movements in a distal tibia in vitro fracture model.