Angular stability potentially permits fewer locking screws compared with conventional locking in intramedullary nailed distal tibia fractures: a biomechanical study

• Published in: Journal of orthopaedic trauma Vol. 25; no. 6; p. 340
• Main Authors: Gueorguiev, Boyko, Ockert, Ben, Schwieger, Karsten, Wähnert, Dirk, Lawson-Smith, Matthew, Windolf, Markus, Stoffel, Karl
• Format: Journal Article
• Language: English
• Published: United States 01.06.2011
• Subjects: Aged; Bone Nails; Cadaver; Elastic Modulus; Equipment Failure Analysis; Female; Fracture Fixation, Internal - instrumentation; Humans; Male; Middle Aged; Prosthesis Design; Tensile Strength; Tibial Fractures - physiopathology; Tibial Fractures - surgery; Treatment Outcome
• DOI: 10.1097/BOT.0b013e3182163345

To compare mechanical stability of angle-stable locking construct with four screws with conventional five screw locking in intramedullary nailed distal tibia fractures under cyclic loading. Ten pairs of fresh-frozen human cadaveric tibiae were intramedullary nailed and assigned to either an angle-stable locking construct consisting of four screws or conventional five-screw locking. After simulating an unstable distal two-fragmental 42-A3.1 fracture, the specimens were mechanically tested under quasistatic and cyclic sinusoidal axial and torsional loading. Bending stiffness of the angle-stable and the conventional fixation was 644.3 N/° and 416.5 N/°, respectively (P = 0.075, power 0.434). Torsional stiffness of the angle-stable locking (1.91 Nm/°) was significantly higher compared with the conventional one (1.13 Nm/°; P = 0.001, power 0.981). Torsional play of the angle-stable fixation (0.08°) was significantly smaller compared with the conventional one (0.46°; P = 0.002, power 0.965). The angle-stable locking revealed significantly less torsional deformation in the fracture gap after one cycle (0.74°) than the conventional one (1.75°; P = 0.005, power 0.915) and also after 1000 cycles (angle-stable: 1.56°; conventional: 2.51°; P = 0.042, power 0.562). Modes of failure were fracture of the distal fragment, loosening of distal locking screws, nail breakage, and their combination, equally distributed between the groups (P = 0.325). Both the angle-stable locking technique using four screws and conventional locking consisting of five screws showed high biomechanical properties. Hence, angle-stable locking reflects a potential to maintain fixation stability while reducing the number of locking screws compared with conventional locking in intramedullary nailed unstable distal tibia fractures.