A finite element analysis to assess tibial bone fracture in malleolar regions following total ankle replacement: Influences of implant designs and implant-bone interfacial conditions.

Background: Tibial bone fractures in the malleolar regions are a major concern during the early postoperative period of total ankle replacement (TAR), affecting patient outcomes such as stability and recovery. Design, placement, and anatomic misalignment of implant components can contribute to malleolar fractures. The aim of this study is to understand the influence of implant design features, including keel, peg, stem, and bar type design, and bone-implant interfacial conditions on malleolar fracture following TAR.

Methods: Three-dimensional finite element (FE) models were generated for the intact and implanted tibia bone using computer tomography (CT) scan data. In the present study, both bonded (fully osseointegration) and debonded (non-osseointegration) implant-bone interface conditions were considered. The proximal part of the tibia was fixed. Finite element models of the intact and implanted tibia were solved for three distinct loading situations that correspond to three ankle positions throughout the gait cycle (GC). The influences of implant design and implant-bone interface conditions on malleolar fracture were examined by evaluating stress distribution in tibia bone post-implantation.

Results: Finite element (FE) analysis revealed that for the medial region, the tibia bone stress elevated to 10 MPa for the medial keel type design, indicating a possible fracture along the medial region. The risk of a medial malleolar fracture is highest for the medial keel type implant design compared to other designs. The bars, central keel, and stem type TAR implant designs also elevate stress on both the medial and lateral regions of the tibia bone. In the case of fully osseointegrated implant-bone interface conditions, the stress is slightly higher than in the case of non-osseointegrated implant-bone interfacial conditions.

Conclusion: The study highlights the potential influence of specific implant designs on malleolar fracture. The current findings are crucial for designing new implants to mitigate tibial bone fracture risks and improve TAR outcomes.