This is a prospective, multicenter, randomized, controlled, non-inferiority clinical trial designed to evaluate the safety and effectiveness of the magnesium-titanium hybrid intramedullary nail system compared with the marketed metal locked intramedullary nail in the treatment of long bone fractures of the extremities.

Intramedullary nailing, a common surgical procedure to fix broken long bones, has a long history. As early as the 16th century, anthropologist Bernardino documented that local physicians in Mexico used wooden rods inserted into the bone marrow cavity to treat patients with unhealed long bone fractures. Modern metallic intramedullary nails were widely adopted after 1939, when Dr. KÜNTSCHER successfully treated femoral shaft fractures with V-shaped stainless steel nails. This technique was introduced to China in the early 1950s, and has since become the first-line treatment for fractures of the arm and leg bones, especially with the advancement of minimally invasive and biological fixation principles.

Traditional intramedullary nails rely on tight contact with the bone marrow cavity for stability. The later development of interlocking screws further improved stability, expanded clinical applications, and reduced complications. Compared with other fixation methods, intramedullary nails offer multiple advantages: they are inserted through small incisions to protect surrounding soft tissues, reduce infection risk, distribute stress evenly to avoid bone weakening, and allow early postoperative movement and weight-bearing, which speeds up recovery.

Currently, biodegradable magnesium and magnesium-based materials are a major global focus in orthopedic implant research. Magnesium is a naturally occurring metal that the body can absorb safely. It has excellent biocompatibility and mechanical properties very similar to human bone, making it an ideal revolutionary implant material. Growing evidence shows that magnesium ions released during the gradual degradation of magnesium implants can actively promote new bone growth and blood vessel formation, which is highly beneficial for fracture healing.

HuaMg Perfection Med Tech (Suzhou) Co., Ltd. has developed high-purity magnesium for orthopedic fixation implants. In preclinical animal studies conducted by qualified third-party institutions, a goat tibial fracture model experiment compared the company's magnesium-titanium hybrid intramedullary nail (experimental group) with conventional titanium alloy intramedullary nails (control group). The results demonstrated that the magnesium-titanium hybrid nail significantly promoted faster and more effective fracture healing than traditional titanium alloy nails.

Based on these promising preclinical findings, this prospective, multicenter, randomized controlled clinical trial is designed to evaluate the safety and effectiveness of the magnesium-titanium hybrid intramedullary nail system for treating long bone fractures of the extremities, compared with the commercially available locked metallic intramedullary nail.

Inclusion Criteria:

1. Aged ≥ 18 years and ≤ 80 years (inclusive), with skeletal maturity, regardless of gender;
2. Diagnosed with long bone fractures of the extremities (including femur, tibia, humerus) requiring surgical fixation with intramedullary nail;
3. Good treatment compliance, willing and able to complete follow-up and observation as required;
4. Voluntarily participate in this trial and sign the written informed consent form.

Exclusion Criteria:

1. Pregnant or lactating women, or individuals with family planning during the study period;
2. Pathological fractures (e.g., bone tumor, bone metastasis, osteomalacia), or patients with too narrow or occluded medullary cavity;
3. Patients complicated with osteomyelitis, osteofascial compartment syndrome, systemic infection or local infection at the surgical site;
4. Patients with severe bone defects requiring artificial bone or autologous bone grafting;
5. Patients with severe soft tissue or vascular injury, or previous surgical treatment at the fracture site, where intramedullary nailing may not provide stable fixation;
6. Patients without sufficient soft tissue coverage at the proposed surgical site;
7. Patients diagnosed with severe osteoporosis by the investigator based on medical history and X-ray films of the fracture site;
8. Patients requiring simultaneous use of both intramedullary nail and screw-plate system at the planned surgical site;
9. Patients with hypermagnesemia (serum magnesium > 1.25 mmol/L (3.0 mg/dL));
10. Patients with uncontrolled diabetes mellitus (glycated hemoglobin HbA1c ≥ 8.0%);
11. Patients with severe cardiovascular, hepatic, renal, pulmonary, hematological diseases or metabolic disorders who cannot tolerate surgery;
12. Patients with previous or concurrent malignant tumors (excluding those cured and disease-free survival for more than 5 years, such as basal cell carcinoma of the skin, cervical carcinoma in situ, and papillary thyroid carcinoma);
13. Patients who have received radiotherapy, chemotherapy, growth factors, immunosuppressants, systemic corticosteroids, long-term (continuous use for more than 3 months) sedative-hypnotics, non-steroidal anti-inflammatory drugs, or bisphosphonates within 6 months prior to screening;
14. Patients with constitutions allergic to the implanted materials or known allergies;
15. Patients who have participated or are participating in any drug clinical trials within 3 months, or other medical device clinical trials within 30 days;
16. Other conditions where the investigator determines the patient is unsuitable for inclusion (e.g., metabolic bone disease, poliomyelitis sequelae, etc.).