Knee disarticulation following oncologic total knee arthroplasty: A 5-year follow-up case report.

BACKGROUND: The present case report describes the 5-year follow-up results of an atypical knee disarticulation of a man previously treated with an oncologic total knee arthroplasty due to an Ewing sarcoma. METHODS: The patient presented an aseptic loosened tibial component of a tumor prosthesis system and requested final amputation, as he had previously suffered from five revision surgeries. To encourage the most functional outcome regarding an exoskeletal prosthesis, we decided to disarticulate the knee joint while retaining the currently fixed femoral component to create a full end-bearing stump. FINDINGS: The patient could be mobilized as a functional knee disarticulated amputee. Seven months after amputation, he showed a slightly less symmetrical gait compared to the preoperative status (preoperative mean Symmetry Index: 0.984 for kinematics and 0.940 for kinetics, 7-month postoperative Symmetry Index: 0.858 and 0.915). At the 5-year follow-up, the femoral component is still stably fixated and shows no loosening signs. In addition, the Symmetry Index increased to 0.908 and 0.949. INTERPRETATION: Even after 5 years, the presented amputation appears to be consistent with "conventional" knee disarticulation. The femoral component still withstands the altered loads and the patient shows a further improved gait pattern.