Bone cyst formation after ankle arthroplasty may be caused by stress shielding. A numerical simulation of the strain adaptive bone remodelling

Abstract Background The history of total ankle arthroplasty (TAA) has different evolution steps to improve the outcome. The third generation implants show an overall 8-year survival rate up to 93%. The main reported reason for early failure of TAA is aseptic loosening, cyst formation is also frequently reported. The aim of the present study is to use the finite element (FE) method to analyze the adaptive bone remodeling processes, including cyst formation after TAA. Methods Bone characteristics applied to the model corresponded to information obtained from computed tomography. Finite element models for the tibia and the talus were developed and implant components were virtually implanted. Results The calculated total bone loss is 2% in the tibia and 17% in the talus. Cysts and areas of increased bone density were detectable dependent on prosthesis design in the tibia and talus. Conclusion Our FE simulation provides a theoretical explanation for cyst formation and increasing bone density depending on implant design. However, cysts are not mono-causal, histo-chemical reactions should also be considered. Further clinical studies are necessary to evaluate the relevance of cyst formation and therapeutic strategies.