Biomechanical evaluation of cerclage wiring in plated tibia fractures using human and synthetic specimens

Supplemental cerclage wiring at the distal tibia has shown to improve the mechanical stabilization of the fracture. However, its clinical use remains controversial partly because of concerns about implant loosening as well as frictional or constrictive interference between the cerclage and cortical surface. The aim of this study was to investigate in a distal tibia fracture model possible loosening of the cerclage and interference with the bone surface. Fourteen distal tibia oblique fractures (AO/OTA 42-A2) in seven human and synthetic bone samples, respectively were treated by plate osteosynthesis with supplemental cerclage wiring. The samples were subjected to 50,000 load cycles under combined axial and torsional loads. Angular and axial displacement were continuously monitored to identify possible cerclage loosening cerclage. Potential incision of the cerclage was inspected visually and on CT scans. Angular displacement was significantly influenced by the bone material (p ≤ 0.001) and type of osteosynthesis (p ≤ 0.001), while axial displacement was only influenced by the type of osteosynthesis (p ≤ 0.001). Lowest displacements were found in samples with plate and cable cerclage. Cerclage stability was maintained throughout the entire test period of 50,000 load cycles for human and synthetic samples. CT images revealed notches from the cerclage clamping mechanism but no incisions of the cable itself. In an oblique distal tibia fracture model, loosening of the cable cerclage was not detected. Full weight-bearing cyclic loads resulted in slight imprints of the cerclage crimp in both, human and synthetic samples. Following the surgical guidelines for careful cerclage installation, a supplemental cable cerclage has the potential to significantly increase the construct stability.