Preoperative Versus Postoperative Start With Thromboprophylaxis in THA (Total Hip Arthroplasty)

Inclusion Criteria: -patients 50 years or older undergoing cemented total hip arthroplasty for primary osteoarthritis Exclusion Criteria: * allergy to Low-Molecular-Weight -Heparin * bleeding disorders * renal failure * hepatic disease * active treatment for malignancy * history of deep venous thrombosis or pulmonary embolism * major operations,trauma,stroke or cardiac infarction the last 3 months before surgery.