This is a randomized clinical trial that will be carried out to examine the use of bioactive glass granules (S53P4) as bone graft substitute in filling small and large bone defects as compared with autogenous and allogeneic bone grafting, respectively.

This a single center randomized trial. The hypothesis of the study is that the selected synthetic bone graft (bioactive glass granules, S53P4, Vivoxid Ltd, Turku, Finland) is as good as traditional autogenous or allogeneic bone grating in filling of non-traumatic bone defects. A total of 48 patients (stratified into two groups) will be included. The underlying bone disease will include common bening and semi-malign bone tumors (such as enchondroma and giant cell tumors) as well as tumor-like conditions (such as fibrous dysplasia, fibrous cortical defect, solitary bone cysts, aneurysmatic bone cyst).

Group I (n=24) will include patients with small benign bone lesions amenable to evacuation and autogenous bone grafting as standard of care. The patients will be randomized to autogenous bone grafting or bioactive glass granule filling. The follow-up examinations up to 52 weeks will include plain X-rays at 4, 26, and 52 weeks as well as MRI ad 4 and 52 weeks.

Group II (n=24) will include patients with a large bone defect. As the selection criteria, large defects have been defined to be defects which need allogeneic bone grafting. The patients will be randomized to allogeneic bone grafting or bioactive glass granule filling. The patients will be followed up to 52 weeks. The follow-up examinations will include X-rays at 4, 26 and 52 weeks as well as PET/CT imaging and MRI at 4 weeks and 52 weeks.

Inclusion Criteria:

• benign bone tumor or tumor-like condition
• age 18 years or more
• signed informed consent

Exclusion Criteria:

• a history of malignancy
• a medication affecting bone metabolism
• any device (such as pace maker) as contraindication for MRI imaging
• gravidity