Abstract:The goal of this study was to determine stress distribution in ankle joint by correlating with the strain distribution and its trend around tibia adjacent to the joint. Using an in-house device, an ankle from a cadaver was kept stable and loaded in various positions: neutral, dorsiflexion, plantar flexion, inversion and eversion. A total of six strain gauges were mounted around the shaft of the tibia, near the tibiotalar joint. This arrangement allowed us to measure deformations in the shaft of tibia. Patient-specific ankle joint geometry was generated from computed tomography data. The finite element model (FEM) of the ankle was validated using the experimental data logged by the strain gauges, and used for obtaining stress on the joint surface. A strong correlation was observed between the FEM and experimentally measured strains in magnitude (R = 0.94, P = 0.008), consequently stress distribution over the joint surface was obtained.
46A. Chitsazan et al.
Total ankle replacement (TAR) and subtalar joint (STJ) fusion, are popular treatments for ankle osteoarthritis (OA). Short endurance limits the former, and movement disability comes with the latter. It is hypothesized here that fusion of the STJ can improve the longevity of the TAR prosthesis. In this study, a fresh human cadaver's ankle joint underwent TAR surgery, and strain patterns in the vicinity of prosthesis were recorded after the application of axial compressive load on tibia, resembling stance phase of the gait. Then, STJ of the same sample fused (FTAR), and a similar test procedure was pursued. The obtained strains in the FTAR were smaller than those of the TAR (p < .01). Finite element models of the tested samples were also made, and validated by experimental strains. The validated FE models were then employed to find stress distribution on the tibial plateau and prosthesis compartments. FTAR demonstrated more regular stress profiles in bone‐prosthesis interface. Also, maximum von Mises stress in the talar component of the FTAR is approximately half of that in the TAR (8 and 15 MPa, respectively). Based on the results of this study, having a more symmetric load distribution on the prosthesis after STJ fusion, longevity of the TAR may likely increase.
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