Abstract
Thoracic osteosynthesis devices commonly used in reconstructive surgery are rib-fixation devices made of titanium or titanium alloys. Severe complications have been reported following these surgeries when implant fracture occurs. The evolution of our surgical practice requires detailed understanding of the local constraint conditions due to respiratory movements. Displacements of tags, related to the fixation area of the rib implants, were studied by stereocorrelation, first on the skin and then directly on the rib of patients in the operating room. The measures were made with six degrees of freedom: linear displacements x y z and rotations φ ψ θ. Six patients were included. The displacements of the tags, according to x, y and z are small: 0.43 mm ± 0.04, 1.36 ± 0.06 mm and 2.66 mm ± 0.13, respectively. The amplitudes of displacement are correlated with respiratory volumes. An increase of 4 mL/kg amplifies the movements by an average factor of 1.6. Numerical simulation of implants and constraints confirmed the phenomenon of fatigue failure for titanium and identified the flexion on the y axis and lateral compression as the main mechanical stresses.