Biomechanical testing of two devices for internal fixation of fractured ribs

An intramedullary screw (Portland Orthopaedics, St. Clair, MI) and Inion (Tampere, Finland) Orthopaedic Trauma Plating System (OTPS) mesh for use for internal fixation of fractured ribs have not previously undergone biomechanical testing. The aim of this study is to compare the biomechanics of intact ribs undergoing four-point bending to the biomechanics of fractured ribs fixed with each of the two devices to determine which device provides superior fixation.

Thirty fresh-frozen porcine ribs (ribs 6-8) were submitted to four-point bending to failure, at a rate of 2.5 mm/min, to determine stiffness and force at failure. The ribs were then randomized to receive fixation with either Inion OTPS mesh or an intramedullary screw. The fixated ribs were again submitted to four-point bending to failure.

Ribs fixated with OTPS mesh were significantly stiffer and failed at a significantly higher load than ribs fixated with intramedullary screws (p = 0.0001). Ribs fixated with OTPS mesh were less stiff than intact ribs but failed at a similar force to intact ribs.

The Inion OTPS mesh system provides superior fixation of fractured ribs compared with an intramedullary screw when tested with four-point bending. The OTPS mesh system also has the added advantage of being absorbable. The intramedullary screw needs to undergo modification and further testing before use in humans. Future studies should focus on more physiologic methods of loading.