Simulation of the mechanical interlocking capacity of a rough bone implant surface during healing

Abstract

BackgroundWhen an implant is inserted in the bone the healing process starts to osseointegrate the implant by creating new bone that interlocks with the implant. Biomechanical interlocking capacity is commonly evaluated in in vivo experiments. It would be beneficial to find a numerical method to evaluate the interlocking capacity of different surface structures with bone. In the present study, the theoretical interlocking capacity of three different surfaces after different healing times was evaluated by the means of explicit finite element analysis.MethodsThe surface topographies of the three surfaces were measured with interferometry and were used to construct a 3D bone-implant model. The implant was subjected to a displacement until failure of the bone-to-implant interface and the maximum force represents the interlocking capacity.ResultsThe simulated ratios (test/control) seem to agree with the in vivo ratios of Halldin et al. for longer healing times. However the absolute removal torque values are underestimated and do not reach the biomechanical performance found in the study by Halldin et al. which might be a result of unknown mechanical properties of the interface.ConclusionFinite element analysis is a promising method that might be used prior to an in vivo study to compare the load bearing capacity of the bone-to-implant interface of two surface topographies at longer healing times.

Implant stability and bone remodeling up to 84 days of implantation with an initial static strain. An in vivo and theoretical investigation

“…In the 3D simulation the strength of the interfacial bone was increased over time, reflecting healing bone and increased mineralization, that increased the interlocking capacity (Halldin et al. ). In the present simulation the interfacial shear strength was simulated both with constant mechanical properties of mature bone and mechanical properties representing healing bone.…”

“…Therefore, the simulation was based on the estimated mechanical properties of the interfacial bone obtained in the study by Halldin et al. (). In the present study, the parameters of the constitutive model described in Halldin et al.…”

“…The theoretical interfacial shear strength of the moderately rough surface was simulated using the finite element model described in Halldin et al. (). In brief, a representative patch of the implant surface was selected and a finite element model was developed according to Fig.…”

“…Finally, the remodeling parameter was set to result in no pressure at 30 days which represents the expected theoretical time point when the initially induced bone strainshave vanished (Halldin et al 2014b). The theoretical interfacial shear strength of the moderately rough surface was simulated using the finite element model described in Halldin et al (2015). In brief, a representative patch of the implant surface was selected and a finite element model was developed according to Fig.…”

“…A general trend in the in vivo experiments is that increased S a value results in increased interfacial shear strength (Loberg et al 2010). By use of the finite element method Halldin et al (2015) estimated the interfacial shear strength for different surface structures. It was found that a surface with a S a value of 1.51 theoretically had a 45% increased interfacial shear strength at 12 weeks of healing compared to a surface with an S a value of 0.91.…”