Excessive valgus alignment leading to asymmetric wear of tibia bearing polyethylene and bush in a rotating hinge knee prosthesis for proximal tibial tumor resection

Abstract

A 37-year-old woman with giant cell tumor with secondary aneurysmal bone cystic change treating with proximal tibia rotating hinge knee prosthesis presented an asymmetric wearing at femoral bushes and tibia hinge bush nine years after surgery. The fixed 7° anatomical design of this prosthesis produces excessive valgus stress leading to contributed asymmetric loading over the interface which resulted in wears of not only the tibia bearing polyethylene but also the tibia hinge polyethylene and femoral bushes. Reconstruct the native mechanical axis remains a main goal to extend the longevity of the implants instead of following the build-in angle of the prosthesis.