Study of a near-cortical over-drilling technique on plate constructs with a conical locking system in a rabbit femoral fracture using a finite element model

This study aimed to evaluate the near-cortical over-drilling technique on the mechanical behaviour of bone-plate constructs in a rabbit transverse femoral fracture. In vitro biomechanical testing and finite element (FE) models were used for analyses. Rabbits' bones (n = 14) were divided into two groups: G1 - without near-cortical over-drilling, and G2 - with near-cortical over-drilling. Locking stainless-steel plates composed of five holes with titanium bushings were used. A compression test was carried out with load applied eccentrically to the femoral head at a rate of 5 mm/min with load cell capacity of 500 kgf. FE model was created to evaluate differences in stress distributions between G1 and G2. In the vitro tests, the maximum load supported by G2 was statistically higher than G1 (p-value = 0.01 < 0.05), whilst there was no significant difference between the groups in bending stiffness (p-value = 0.12 > 0.05). FE models demonstrated similar behaviour to experimental data in terms of stiffness and biomechanical behaviour for either G1 or G2 (p-value = 0.09 > 0.05). Stress levels were higher for G1, and stress concentration areas were at the experimentally fractured sites. No evident pattern of fracture or stress distribution was observed in the bone for G2. In conclusion, over-drilling increased the maximum load-bearing capacity with a slight decrease in overall stiffness, which could potentially improve bone healing.