The investigators apply 3D printed titanium implant to treat bone defects. Without using bone grafts and growth factors, the investigators anticipate the titanium implant alone can help bone reconstruction.

The investigators treat large segmental bone defects caused by three reasons, including trauma, infection and tumor. In this study, polyporous 3D printed titanium implant is applied to reconstruct the bone defects and the investigators will follow up patients' function and bone regeneration.

Inclusion Criteria:

• bone defects caused by trauma or infection or tumor
• the length of bone defect is more than 6cm
• more than 18 years old

Exclusion Criteria:

• malignant tumor
• patients with bad conditions failing to tolerate surgery