Our patient was a 46-year-old male who initially presented to our orthopedic oncological department at 16 years of age with pain in the lower left limb associated with a growing mass and swelling of the knee. Radiological examination revealed a permeative, mixed lytic, and osteoid-forming lesion arising from the metaphysis of the left distal femur. Initial suspicions were bone primary sarcoma or osteomyelitis.

The biopsy confirmed the diagnosis of conventional intramedullary high-grade osteosarcoma of the left distal femur. Staging investigations ruled out systemic metastatic disease and skip metastases with a resectable bone tumor.

We decided to perform a wide resection of the distal femur and a reconstruction with an osteochondral femoral allograft. One year later, he developed a peri-implant infection requiring 2-stage revision, initially placing an antibiotic spacer with an intramedullary nail for ten months. Then, we performed a reconstruction with another distal femoral osteochondral allograft. Twelve years after the initial procedure, he underwent conversion to knee oncological endoprosthesis due to a distal metadiaphyseal fracture of the femoral allograft. He developed a late periprosthetic infection eighteen years after endoprosthesis implantation. He was initially treated with several surgical debridements and suppressive antibiotics with the intention of implant retention (Figure 1 ).

The x-rays and computational tomography (CT) analysis revealed severe bone loss in the middle femur and septic loosening in the tibial component.

After extensive discussions with the patient, ablative surgery was indicated and opted for due to continuous drainage, non-healing sinus tracts, significant limb length discrepancy, severe joint stiffness, and non-controlled pain. Van Nes rotantioplasty was not considered because of the rigid equinus deformity secondary to limb length discrepancy.

We performed tibial turn-up plasty thirty years after the initial intervention. The goal was to provide additional osseous length and optimize prosthesis fitting, avoiding extremely short transfemoral stump.