This is an observational, prospective and multicenter clinical investigation that is part of the active materiovigilance plan that Orthofix Srl, in agreement with its Notified Body. The sponsor has planned to actively collect clinical data relating to the use of Chimaera Intramedullary Nail in a representative number of users and elderly patients with fractures of the proximal femur. The data obtained from this clinical investigation will be used to complete the pre-market clinical evaluation carried out on the Chimaera with post-market clinical data from the use of the device in normal clinical practice.

Orthofix Srl has developed and placed on the European market the Chimaera Intramedullary Nail after having evaluated the clinical performance and safety of the medical device based on biomechanical tests and clinical data obtained from scientific publications on equivalent products. The outcome of this pre-market assessment established that Chimaera possesses the requirements for CE marking, in particular, it possesses an acceptable risk/benefit ratio if used according to the manufacturer's directions for use.

The enrolled patients, as would happen even if they did not decide to participate in this study, will proceed by undergoing the surgery necessary for the application of the medical device under observation (Chimaera), which coincides with the start of the treatment period.

After the surgery and the hospital discharge, the patient will undergo subsequent follow-up visits. The follow-up visits carried out respectively at 1 month and 3 months after the date of surgery, conclude the treatment period which, barring complications, is expected within 8 - 12 weeks from the date of surgery with the consolidation of the fracture of the proximal femur treated. Healing will be verified by the Investigator based on an X-ray check through which he/she will make a qualitative assessment of the bone density at the fracture site and the positioning of the bone stumps. Starting from the 3-month visit and up to 1-year visit, the Investigator will compile the Bowers & Parker functional score (a measure of effectiveness) for the evaluation of the patient's functional recovery. The score obtained at the follow-up visits will be compared to the score compiled during the discharge visit representative of the pre-fracture patient's status.

For patients that undergo this treatment, the removal of the device is not planned except for serious adverse events that require a second surgery to complete the treatment of the fracture (safety measure). Once the treatment period has ended, the control period begins during which 2 visits will be made, respectively 6 months and 1 year after the date of the surgery. During these visits, clinical data will be collected to follow the evolution of the fracture consolidation and the functional recovery of the patient and the occurrence of any adverse events in the medium term.

Inclusion Criteria:

• directly or indirectly (through a respondent) will have expressed their will to participate in the study by signing and dating the informed consent;
• will have reached the age of 65 at the time of signing the informed consent;
• he/she will have been diagnosed with a fracture in the pertrochanteric, intertrochanteric or subtrochanteric region of the femur, stable or unstable, not previously treated;
• based on the investigator's judgment, he will have a regular indication for surgical treatment with an intramedullary nail;
• the fracture will be treated with the Chimaera short nail (length = 180 mm) and one or two telescopic lag screws, according to the manufacturer's instructions for use.

Exclusion Criteria:

• will undergo surgery to treat the results of a previously treated fracture;
• he/she will have been diagnosed with a pathological fracture of oncological origin (primary tumor or skeletal metastasis);
• he/she will have been diagnosed with a fracture in the diaphyseal and/or distal region of the femur;
• he/she will have been diagnosed with an open fracture (type II and III according to the classification of Gustilo and Anderson) of the proximal femur;
• he/she will have been diagnosed with multiple fractures (including bilateral proximal femur fractures);
• in the pre-or intra-operative phase it will be decided to treat the fracture with the long version of the Chimaera nail and/or with non-telescopic cephalic screws (fixed length);
• will have a medical condition that constitutes a contraindication to treatment with Chimaera according to the manufacturer's instructions for use;
• will have a suspected or certified hypersensitivity/allergy to some component of the device that comes into contact with the patient;
• will present some clinical condition that, in the Investigator's opinion, could interfere with the procedures of the Clinical Investigation or that could jeopardize the safety of the patient;
• at the same time he will be treated with an unauthorized device that cannot be removed without endangering the safety of the patient;
• will be participating in other clinical trials or had participated in other clinical trials in the 3 months before signing the informed consent.

An adult patient with a previously untreated proximal femur fracture who, based on the free judgment of the Investigator, will have a regular indication for surgical treatment with Chimaera will be considered eligible for participation in the clinical investigation. Eligible patients who meet the inclusion criteria and no exclusion criteria will be considered eligible for participation in this Clinical Investigation.