Abstract
Background
Bioresorbable materials offer the potential of developing fracture fixation plates with similar properties to bone thereby minimising the “stress shielding” associated with metal plates and obviating the need for implant removal. Phosphate glass fibre reinforced (PGF)-polylactic acid (PLA) composites are bioresorbable and have demonstrated sufficient retention of mechanical properties to enable load bearing applications.
Aim
To determine the potential in vivo “stress shielding” effects of a novel PGF reinforced PLA composite plate in an animal model.
Methods
Twenty five NZW rabbits underwent application of the composite plate to the intact right tibia. They were divided into 5 groups corresponding to the time points from surgery to sacrifice −2, 6, 12, 26 and 52 weeks. Outcomes included radiographs, NanoCT imaging, histological assessment and mechanical testing of the retrieved plated tibia and opposite control tibia.
Results
Plate integrity was retained up to 26 weeks on radiographs and scanning electron microscopy (SEM). The mechanical properties of the plated bones were equivalent or greater than the control bones at each time point although the relative improvement in mechanical properties diminished with time. Nano CT imaging and SEM revealed bone remodelling with cortical thinning beneath the composite plate which progressed as the duration of implantation increased.
Discussion
The bone-composite plate construct retained its mechanical properties compared to the control bone despite thinning of the cortex beneath the plate. More importantly, this work suggests that fracture fixation systems with equivalent mechanical properties to bone may still induce a “stress shielding” response.
