Bone tissue loads around titanium femoral implant and coated with porous layer

Abstract

Purpose: Difference in the mechanical properties of bone and stiffer femoral implant causes bone tissue resorption, which may result in implant loosening and periprosthetic fractures. The introduction of porous material reduces the stiffness of the implant. The aim of the study was to analyse the influence of porous shell of femoral revision implant on bone tissue loading distribution with use the finite element method. Design/methodology/approach: Load transfer in the femur has been investigated using the finite element method (Ansys). Cementless implant models were placed in the anatomical femur model. Femur model included sponge bone and cortical bone. The solid implant was compared with the implant containing porous material in 70% in outer layer with a thickness of 2 mm. Load of 1500 N during gait was simulated. In addition, the forces of the ilio-tibial band and the abductor muscles were implemented, as well as the torque acting on the implant. Findings: Increase of stress for the porous model was found. The underload zones in bone have been reduced. Loading distribution was slightly more favourable, albeit rather in cortical bone. Stress value in cancellous bone around cementless implant margin has increased to a level that is dangerous for bone loss. Stress in the implant was not dangerous for damage. The stress distribution was different in the implant neck zone where the porous shell borne a little less load and high stress was shifted to the stiffer core. Research limitations/implications: Variable conditions for fitting the stem to the bone as well as the friction conditions were not investigated. Practical implications: Stress values in the spongy bone around the insertion edge of the cementless implant are consistent with long-term clinical results of the bone atrophy in 1 and 2 Gruen`s zones around the fully porous implants. Originality/value: The advantage of fully porous coated implant was the decrease of risk of trabecular bone tissue resorption around the implant tip and the increase of risk of trabecular bone tissue resorption around insertion edge of the implant.