Objective: Clinical applications of Total Ankle Arthroplasty (TAA) started in the 1970s. Various TAA prostheses have been developed. Although TAA is excellent for pain relief, loosening and sinking in an early postoperative stage remain as problems since the implant is placed under considerable stress. We developed a new 3-component design TAA aiming at clinical results acquisition over a long period of time, and verified the design.
Methods: From the osteotomy surface and CT data of cadaver bone, contour extraction of the articular surface was performed. Contact stresses on the tibial articular surface were refined using finite element analyses (FEA) . An investigation was performed regarding how changes in the joint's range of motion affect the contact area.
Results: FEA showed peak von Mises stress of 13.0 MPa under a 3, 000 N load, well below the plastic limit of UHMWPE. The overall contact area of the talocrural joint became a constant 600mm2 between±10 degrees of dorsiflexion and plantar flexion. For the 2-component prosthesis under standard conditions, FEA showed peak von Mises stress of 19.5 MPa under a 3, 000 N load, with a contact area of 190mm2.
Conclusion: FINE® Total Ankle System was developed for the purpose of stress dispersion and easy self-alignment of the ankle joint. From this investigation, it was shown that TAA with this 3 component prosthesis improves stress dispersion.
