We present a rare case of fracture of the modular femoral component in a varus-valgus constrained total knee arthroplasty (TKA) prosthesis which occurred 2 years after implantation. Both femoral and tibial components underwent a second revision using a constrained hinged TKA. Laboratory analysis revealed insufficient metaphyseal bone stock in association with inadequate cement mantle incorporation which made implant fixation solely reliant on the intramedullary stem construct. It was therefore hypothesized that high repetitive stresses over the junction of the modular component led to the fracture.
Level of evidence: Case report, Level IV.