Aims: The purpose of this in-vitro study is to understand the mechanical behaviour of a fracture plate incorporating biodegradable inserts. Methods: A new, innovative fracture plate design incorporating biodegradable inserts was tested. These plates allow for micromotion during the union phase, which allows for increased healing. Resorption of the inserts over time works to decrease stress shielding during the remodelling phase. Two separate bone models were used to simulate a fracture during both the union phase of healing and the remodelling phase. This plate, termed an axially compressible plate (ACP) was mounted to the bone models in four different conþgurations. On the model simulating the union phase, stiffness and micromotion were measured using an LVDT for bending and an extensometer for compression. With the model simulating the remodelling phase, strain was measured on the bone model using a strain gage mounted directly below the plate midpoint.

Conclusions: The results show that during the union phase, the ACP should allow for micromotion, which increases with successive loss of inserts. Results also show that during the remodelling phase, the loss of inserts increases the amount of strain in bone and thus decreases stress shielding.