Retrospective, multicenter, non-profit observational study. The study will include consecutive patients who underwent lower-limb megaprosthesis implantation at the participating Centers between January 1, 2020, and June 30, 2023.

Megaprostheses are large orthopedic prostheses used to replace extensive portions of bone and joints, typically after the removal of bone tumors or in other conditions involving major bone loss (severe trauma, revisions). In the 1990s, they became the standard for reconstruction following resection of primary malignant bone tumors. Over time, the indications for the use of megaprostheses have expanded to include benign but locally aggressive bone tumors, bone metastases, and malignant soft tissue tumors. Currently, the number of megaprosthesis procedures for non-oncologic conditions is also increasing.

The anatomical sites where a megaprosthesis can be implanted include the femur (proximal, distal, or total), the proximal tibia, and the proximal humerus. Megaprostheses are modular metal structures (titanium, chrome-cobalt) that may include an artificial bone segment, a joint component (hip, knee, shoulder), and potentially an antibacterial coating (such as silver).

While a megaprosthesis represents an important therapeutic option for limb salvage, it also involves complex surgery with significant complication and failure rates. Periprosthetic infection, with incidence rates ranging from 3% to 30%, is certainly one of the most feared complications, as it is associated with increased morbidity and mortality, longer patient recovery times, and higher healthcare costs. Revising a megaprosthesis often presents additional technical challenges for orthopedic surgeons (for example, the impossibility of replacing the implant due to the lack of remaining tissues). Moreover, the rate of infectious complications in megaprostheses is higher than that of periprosthetic infections in standard joint replacements. Possible explanations include longer surgical times, greater soft tissue trauma, or patient-related factors (such as immunocompromised status in oncologic patients).

The use of megaprostheses to treat different types of lower-limb conditions is increasing, and these prostheses carry a higher risk of infection compared to standard implants.

There is a shortage of studies in the literature that specifically and thoroughly analyze risk factors for megaprosthesis infections, and existing studies often involve small patient cohorts.

It is therefore highly rational to identify specific infection risk factors for patients receiving a lower-limb megaprosthesis, if present, to highlight those that may be modifiable and ultimately reduce the infection risk for individual patients. The primary objective of the study is to identify risk factors for the development of infection in lower-limb joint megaprostheses within 2 years of implantation.

Inclusion Criteria:

• Age ≥ 14 years
• Implantation of a lower-limb megaprosthesis at one of the participating centers between January 1, 2020, and June 30, 2023
• At least 2 years of follow-up after megaprosthesis implantation
• Signed informed consent

Exclusion Criteria:

• None

All patients aged 14 years or older who underwent implantation of a lower-limb megaprosthesis at the participating Centers between January 1, 2020, and June 30, 2023, will be included.