Investigation of load transfer process between external fixator and bone model by experimental and finite element methods

Unilateral external fixators are widely used in orthopedics to stabilize fractured bones and to treat limb deformities. One of the main problems is that it is difficult to detect healing status. In addition, whether load transfer progress between the fixator and bone model are the same under axial, torsional, and bending loads has not been studied. Therefore the main purpose of this study was to detect the load transfer process between the fixator and a bone model by measuring strains on the fixator–bone system during four healing states using experimental and finite element methods. In the experimental method, 20 strain gauges were used to measure strain on the fixator and bone model under three load conditions. Polyacetal slice models with different material properties were used to simulate the callus model during four growth states. The results indicate that strain on the bone model increased and strain on the fixator parts decreased with maturation of the callus under axial, bending, and torsional loads. Although all curves showed a similar changing trend, they were slightly different under the three loads. This study provides a useful method to monitor the fracture healing process, and identifies the healing endpoint, detects healing status, and provides useful information for the orthopedist