[Biomechanics of thoracic wall instability].

Traumatic injuries of the thorax can entail thoracic wall instability (flail chest), which can affect both the shape of the thorax and the mechanics of respiration; however, so far little is known about the biomechanics of the unstable thoracic wall and the optimal surgical fixation. This review article summarizes the current state of research regarding experimental models and previous findings. The thoracic wall is primarily burdened by complex muscle and compression forces during respiration and the mechanical coupling to spinal movement. Previous experimental models focused on the burden caused by respiration, but are mostly not validated, barely established, and severely limited with respect to the simulation of physiologically occurring forces. Nevertheless, previous results suggested that osteosynthesis of an unstable thoracic wall is essential from a biomechanical point of view to restore the native respiratory mechanics, thoracic shape and spinal stability. Moreover, in vitro studies also showed better stabilizing properties of plate osteosynthesis compared to intramedullary splints, wires or screws. The optimum number and selection of ribs to be fixated for the different types of thoracic wall instability is still unknown from a biomechanical perspective. Future biomechanical investigations should simulate respiratory and spinal movement by means of validated models.