Limb-preserving surgery for bone tumors is now largely mature, for example, after surgery for osteosarcoma, chondrosarcoma, giant cell tumor of bone, Ewing’s tumor, metastatic bone tumor, etc. How to clarify whether there is local recurrence at an early stage? Do you do CT, do MR, do bone scan, do PET-CT, or do you draw blood for laboratory test? After bone tumor limb removal and prosthesis replacement, CT and MR around the prosthesis are prone to artifacts, thus making local recurrence of tumor harder to be detected in early stage. At present, CT technology for artifact removal is basically mature, but bone tumor recurrence is often soft tissue type tumor, the sensitivity of CT is difficult to detect when this type of tumor is small, which is not conducive to early detection and early re-excision. Recurrence. Blood tests for local recurrence are unlikely. Bone scans face a similar dilemma as PET-CT. Can de-artifacted MR be currently used for early detection of recurrence or not around the tumor prosthesis? At present, the Department of Orthopedics of Shanghai Ruijin Hospital is equipped with such a de-artifacted MR technique for early detection of recurrence around bone tumor prosthesis. From the clinical practice, de-artifact MR not only can make the demarcation between the prosthesis and the surrounding tissues clear, but also can detect the tumor recurrence at an earlier stage. After early detection, the tumor can be resected again. Therefore, after bone tumor prosthesis surgery, it is better to need to do de-artifactive MR examination.