Figure 1

Implant loosening due to periendoprosthetic tibial chondrosarcoma. Anterior-posterior (a) and lateral (b) radiograph prior to total knee arthroplasty (TKA) depicting medial joint space narrowing and meniscal calcification. A radiolucent lesion in the central tibial plateau is indicated by a red arrow. Lateral (c) and anterior-posterior radiograph (d) 14 month after TKA surgery showing the osteolytic lesion in the proximal tibia, extending through the epi- and metaphyses from the central region to the lateral and anterior cortical bone. Permeation of the cortical bone with discontinuing periosteal reactions, including spiculae formation, can be observed. Preoperative planning was performed to determine plains of resection at 8 cm proximally and 15 cm distally to the joint line (indicated by red lines in c and d). Local CT-scans are showing cortical bone permeation, especially in the anterior and lateral aspects of the proximal tibia at the level of the cemented tibial implant (e) and below (f). Open incision biopsy was performed and multiple soft and bone tissue samples were obtained (g) and sent for microbiological and histopathological examination.