ABSTRACT
Objective To systematically explore the change of fixator stiffness (0.05-7.50 kN/mm) on healing effects of seven different types of fractures (A1: simple spiral, A2: simple oblique, A3: simple transverse; B2: wedge spiral, B3: wedge fragmented; C2: complex segment, C3: complex irregular) under the OTA/AO fracture classification. Methods Taking intramedullary nail fixation of long bone fracture as research objective, based on strain-regulated tissue differentiation theory, and combined with fuzzy logic algorithm and finite element analysis, the process of fracture healing was numerically simulated. Results Moderate fixator stiffness (1.5-2.5 kN/mm) shortened the healing time while ensuring recovery of biomechanical performance of the fractured bone. However, the appropriate fixator stiffness corresponding to each fracture type was different. The sensitivity of healing effects to change of fixator stiffness was also different. For type A fracture, when fixator stiffness was 1.5 kN/mm, optimal biomechanical recovery of the fractured site could be obtained, while the change in fixator stiffness had a large impact on healing effect. For type B and C fractures, when fixator stiffness was above 1.5 kN/mm, the change in fixator stiffness had no significant effects on recovery of biomechanical performance. Conclusions Fracture healing is affected by both fixator stiffness and fracture types. For treating fractures in clinic, the selection of fixators should carefully take fracture types into account.