Complete removal of all tumor tissue with a wide surgical margin is essential for the treatment of osteosarcoma (OS). However, it's difficult, sometimes impossible, to achieve due to the invisible small satellite lesions and blurry tumor boundaries. Besides, intraoperative frozen-section analysis of resection margins of OS is often restricted by the hard tissues around OS, which makes it impossible to know whether a negative margin is achieved. Herein, based on the high expression of B7-H3 in OS, a targeted probe B7H3-IRDye800CW is synthesized by conjugating anti-B7H3 antibody and IRDye800CW. This trial is aimed to investigate R0-resection rate and 2-y local recurrence rate after using this probe in Musculoskeletal tumor surgery for osteosarcoma as well as the safety parameters of this probe in human.

Inclusion Criteria:

• 1. Patients with histologically confirmed osteosarcoma of the limbs.
• 2. the patients has not undergone tumor resection.
• 3. Age between 18 and 60 years old.
• 4. No prior systemic treatment for osteosarcoma.
• 5. Measurable disease as assessed by imaging studies (e.g., MRI, CT).
• 6. Adequate bone marrow, liver, and renal function.
• 7. Written informed consent obtained from the patient.

Exclusion Criteria:

• 1. History of other malignancies within the past 5 years.
• 2. Pregnancy or lactation.
• 3. Known hypersensitivity to any component of the B7H3-based NIR imaging agent.
• 4. Uncontrolled intercurrent illness that would preclude safe study participation.
• 5. Prior radiation therapy to the target lesion.
• 6. Any medical condition that would compromise the patient's ability to undergo surgery or comply with study procedures.
• 7.Patients not able to sign the Informed Consent.