Biomechanical testing of a novel, minimally invasive rib fracture plating system

A novel rib fracture repair plating system was developed to provide durable fixation with a shorter length than standard systems and thus facilitate minimally invasive repair. We hypothesized that U-plate fixation would be at least equivalent in durability to standard anterior fixation.

Twenty fresh frozen ribs (10 pairs) from two human cadavers were first tested for intact stiffness (force or deformation). A gap of 5 mm was then created in the middle of each rib with a saw. Each rib was reconstructed with either the U-plate (4.6 cm length, Acute Innovations, LLC, Hillsboro, OR) with four screws or a 2.4-mm anterior locking plate (9.5 cm length, Synthes, Paoli, PA) with six screws. The U-plates were placed on one rib and the anterior plates on the contralateral rib of the paired levels. The reconstructed ribs were cycled 50,000 times with a load of +/-2N at 1 Hz in a simulation of the repetitive loading of deep breathing. The stiffness of the construct was measured throughout the test.

Stiffness decreased from the intact rib to the transected/plated rib for both types of fixation; however, a significant decrease in stiffness was observed only with the anterior repair (p = 0.03). After 50,000 cycles, the U-plated ribs lost 0.12 +/- 0.03 N/mm (1.9%) stiffness, whereas the anterior-plated ribs lost 0.72 +/- 0.13 N/mm (9.9%) stiffness (p = 0.001).

In this simulation of an unstable rib fracture with a small bony gap, U-plate fixation was more durable than standard anterior fixation. The greatly diminished size of the U-plate compared with the standard may facilitate minimally invasive rib fracture repair.