The primary aim of this study is to test if etoricoxib decreases the perioperative blood loss compared to diclofenac.

Secondary questions to be explored are:

• Does etoricoxib prevent Heterotopic ossification after Total Hip Arthroplasty as well as diclofenac ?
• Do diclofenac and etoricoxib both reduce pain at rest and on movements?
• Does etoricoxib compared to diclofenac reduce the amount of rescue medication (Oxycodon)?
• Does etoricoxib improve gastrointestinal tolerability compared to diclofenac?

Total Hip Arthroplasty (THA) is a common surgical procedure in orthopaedic surgery which can be associated with perioperative blood loss and severe postoperative pain. Adequate pain management is very important to achieve early mobilisation in order to avoid immobility-induced complications. Non steroidal antirheumatic agents (NSAIDs) as selective Cox-2 inhibitors are commonly used in the management of postoperative pain. There exist non-selective and selective Cox-inihibitors. Non-selective NSAIDs block the systhesis of prostagandins by the two iso-enzymes of the cyclooxygenase, Cox-1 and Cox-2. For this reason the bleeding risk after operations (e.g.tonsillectomy) is increased.

In this regard, the perioperative use of Cox-2 selective NSAIDs is advantageous for pain management after tonsillectomy. This could be shown for Rifecoxib, a selective Cox-2 inihibitor. For THAs with treatment of Etoricoxib, also a selective Cox-2 inhibitor, possible complications as the increased risk of haematoma, gastrointestinal bleeding and the need of blood transfusion could possibly be reduced. Selective Cox-2 inhibitors do not interfere with the coagulation system. Study results show that other selective Cox-2 inhibitors like meloxicam reduce perioperative blood loss. Thus, besides ensuring a good perioperative pain management, selective Cox-2 inhibitors may in addition cause less blood loss than non-selective NSAIDs.This possible reduction of blood loss during pain management with Etoricoxib (Arcoxia) will be investigated the described clinical trial.

Heterotopic ossification (HO) is a complication occurring after THA which can lead to postoperative pain and reduced function. Non-selective NSAIDs are commonly used in the prophylaxis of heterotopic ossifications after THA. The exact mechanism of prevention of bone formation is unclear. Some results indicate that the development of HO follows a Cox-2 pathway. A further aim of this clinical trial is to investigate the efficacy of Etoricoxib in the prevention of heterotropic ossification.

Inclusion Criteria:

• Indication for THA because of primary and secondary osteoarthritis of the hip.
• male or female patients of the age of 55 - 85 years
• informed consent afer having been informed in detail about the clinical trial by the investigator
• negative pregnancy test (<= 2 days before inclusion) for women with child bearing potential (pre menopausal, <2 years menopausal, not surgically sterile), use of high security contraception methods as oral contraception agents or preservatives. The use of high security conception methods is also to obligatory for male patients

Exclusion Criteria:

• Known hypersensitivity to one of the two investigational medical products or substaces of similar chemical structure or to any of the excipients
• Patients who have experienced bronchospasm, asthma, acute rhinitis, urticaria, or allergic-type reactions after taking acetylsalicylic acid or NSAIDs including COX-2 (cyclooxygenase-2) inhibitors
• unexplained dysfunction of haematopoiesis
• treatment with NSAIDs or coxiben in the past 5 days before start of study
• Active peptic ulceration or active gastro-intestinal (GI) bleeding
• Pregnancy and lactation
• Congestive heart failure (NYHA II-IV)
• Established ischaemic heart disease, peripheral arterial disease, and/or cerebrovascular disease
• clinically relevant disease of the cardiovascular system, severe hepatic dysfunction (serum albumin <25 g/l or Child-Pugh score ≥10), severe renal dysfunction (estimated renal creatinine clearance <30 ml/min, clinical relevant disease of the nervous system, the endocrinium or another severe systematic disease
• Systemic lupus erythematodes or mixed connective tissue disease
• Inflammatory bowel disease
• alcohol or drug abuse during the last past 3 months
• Patients with hypertension BP persistently > 140/90mmHG) and has not been adequately controlled
• life expectancy <6 months
• state of mind which does not enable the patient to understand the nature of the study, its importance and possible consequences
• evidence that the respective person will not cooperate with the study protocoll
• participation of the patient in another clinical trial during the past 4 weeks before inclusion
• prior participation in this clinical trial