This clinical study aims to evaluate the efficacy and safety of the anticoagulant Dimolegin® compared to low molecular weight heparin (Clexane®) for the prevention of venous thromboembolic events (VTE) in patients undergoing major joint (hip or knee) replacement surgery. The study will assess the incidence of VTE, VTE-related mortality, and all-cause mortality during different follow-up periods in both treatment groups. Additionally, the study will evaluate the frequency of bleeding events and the incidence, number, and characteristics of all adverse events associated with Dimolegin® and Clexane® therapy.

Inclusion Criteria:

• Men and women between the ages of 18 and 80.
• Patients scheduled for unilateral elective total hip or knee arthroplasty.
• The patient's voluntary informed consent.
• Negative pregnancy test result (for female patients with preserved reproductive potential).
• Patients with reproductive potential should agree to use methods of contraception according to the protocol.

Exclusion Criteria:

• Surgery for an acute fracture (<4 weeks).
• Revision or extraction arthroplasty.
• Septic arthritis.
• The only lower limb.
• Increased risk of thrombosis.
• Active bleeding or increased risk of bleeding.
• Current coagulopathy (patient's or his relative's) or congenital thrombophilia.
• Collection of at least one volume unit of donated blood (≥ 450 ml) or blood transfusion during the previous 12 weeks.
• Surgery or injury during the last 90 days.
• Diseases of the digestive system that may disrupt the absorption of the study drug.
• Significant cardiovascular diseases currently or within 6 months prior to screening.
• Active liver or biliary tract diseases.
• Creatinine clearance, calculated according to the Cockcroft-Gault formula, less than 30 ml/min.
• Positive test result for HIV, syphilis, hepatitis B and C markers.
• The development of trophic disorders of the lower extremities that are not amenable to drug treatment.
• Any condition in which, in the opinion of the researcher, surgical intervention or the use of anticoagulants is contraindicated.
• Body mass index is less than 18.5 or more than 40 kg/m2.
• Body weight for women is less than 45 kg, for men less than 57 kg and above 130 kg for both.
• Systolic blood pressure > 180 mmHg and/or diastolic blood pressure >110 mmHg.
• Hemoglobin < 105 g/l in women or < 115 g/l in men.
• Abnormal results aboratory parameters of the coagulation system (platelets, APTT, prothrombin time, INR) beyond the limits of normal values.
• An increase in ALT or ACT ≥ 2 times from the upper limit of normal (ULN) or total bilirubin ≥ 1.5 times from ULN.
• Hypersensitivity or contraindications to the administration of Dimolegin®, enoxaparin sodium, unfractionated heparin or warfarin.
• The need for constant use of parenteral or oral anticoagulants.
• The need for continuous use of antiplatelet drugs, which cannot be discontinued at least 4 days before the start of the investigational therapy.
• Systemic therapy with drugs with strong inducers and inhibitors of CYP3A4 and P-glycoprotein, which cannot be discontinued at least 7 days before the start of the investigational therapy.
• Pregnant or breast-feeding women.
• Participation in another clinical trial currently or within 90 days prior to screening.
• Affiliation to a research center, Sponsor, or contractual research organization.
• Inability to read or write; unwillingness to understand and follow the procedures of the study protocol; non-compliance with the study therapy or procedures.