Osteosarcoma is one of the most common malignant tumours of osseous tissue, where localisation of the tumour in the proximal third part of the humerus is the third most frequent (6). Prosthesing of the teenager’s right humerus after pathological fracture was done with cervicocapital or Moore endoprosthesis. This endoprothesis developed for the treatment of femoral neck fracture and using for hip hemiarthroplasty. After 10 years the patient has suffered fracture of periprosthesis, osteosynthesis has been performed. Within 2 months after osteosynthesis the patient has regained the previous functional level without complications