Zhang 2014.

Methods	Study design: Randomised trial Country: China Setting: Single centre; hospital and outpatient clinic; June 2012 and May 2013 Intention‐to‐treat: Yes For the purposes of our analyses we used all participants randomised, as reported by the study authors
Participants	Number randomised: Total n = 40 (extended n = 20; short n = 20) Exclusions post randomisation: Not stated Losses to follow up: None Age mean years (range): Extended 60.1 (37 ‐ 76); short 61.3 (42 ‐ 78) Sex (F/M): Extended 11/9; Short 12/8 Inclusion criteria: All patients admitted to the Center for Bone and Joint Health between June 2012 and May 2013, who were diagnosed with osteonecrosis of the femoral head, scheduled for elective total hip replacement and provided informed consent Exclusion criteria: Had Doppler ultrasound performed 48 hrs prior to the surgery showing DVT; had undergone surgery recently, a history of active major bleeding or a tendency to bleed; had recent use of anticoagulants, antiplatelets or antifibrinogenics; were pregnant or nursing baby or did not take measures to prevent pregnancy; had severe kidney or liver dysfunction or other disease that could interfere with drug metabolism or blood coagulation
Interventions	Treatment: Oral rivaroxaban 10 mg once daily started within 6 ‐ 10 hrs after the surgery for 35 days Control: Oral rivaroxaban 10 mg once daily started within 6 ‐ 10 hrs after the surgery for 7 days followed by no treatment Duration: 35 days post surgery
Outcomes	Primary: Efficacy: haemostatic parameters including thrombin‐antithrombin complexes, prothrombin fragment 1 and 2, D‐dimer and fibrinogen Secondary: DVT Outcomes were recorded pre‐operatively (within 48 hours before surgery) and at 1, 7, and 35 days after surgery
Notes	Funding: Not reported Method of VTE evaluation/confirmation: lower limb ultrasonography
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Using random numbers generated by computer prior to the surgery
Allocation concealment (selection bias)	Unclear risk	Insufficient information provided
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No mention of blinding of participants or personnel
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No mention of blinding of outcome assessors
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants accounted for, similar numbers in groups, no missing outcome data
Selective reporting (reporting bias)	Low risk	All listed outcomes reported on
Other bias	Low risk	No indication of other bias

DVT: deep vein thrombosis
 F: female
 IU: international unit
 LMWH: low‐molecular‐weight heparin
 M: male
 NSAID: non‐steroidal anti‐inflammatory drug
 PE: pulmonary embolism
 post‐op: post‐operatively, after operation
 pre‐op: prior to operation
 VAS: visual analogue scale
 V‐Q: ventilation–perfusion
 VTE: venous thromboembolism