Table 1.

Study characteristic.

		Patient number		Mean (SD or range) age, years		Sex (female/male)		Dosage and duration
Study	Country	Aspirin	LMWH	Aspirin	LMWH	Aspirin	LMWH	Aspirin	LMWH	Use of mechanical VTE prophylaxis	Routine DVT screening or symptomatic DVT	DVT diagnostic methods	Follow-up duration	Outcome of VTE risk of aspirin, RR (95% CI)
Fuente 13	Mexico	188	214	70.33	71.31	0.85	1.04	100 mg/d, for 30 days	Enoxaparin 40–60 mg, for 30 days	NA	NA	Venous ultrasonography	90 days	0.59 [0.10–3.47]
Gelfer 16	Israel	28	20	68 (10.4)	67 (8.7)	1.61	1.90	100 mg/d, duration NS	Enoxaparin 40 mg/d, duration NS	Pneumatic compression system in aspirin group only	Routine screening (5 8 days after surgery) plus any symptomatic VTE during follow-up	Venogram for screening plus venous ultrasonography for symptomatic events	90 days	0.71 [0.20–2.52]
Sidhu 11	Australia	3348	2357	67.0 (61.0–74.0)	68.0 (61.0–74.0)	1.30	1.33	100 mg/d, for 14 days	Enoxaparin 40 mg/d, for 14 days	Compression stockings in both group	Symptomatic	Venous ultrasonography	90 days	1.65 [1.23–221]
Westrich 17	USA	136	139	69.0 (12.1)	68.9 (9.6)	1.57	2.02	325 mg/d, for 28 days	Enoxaparin 40 mg/d, for 28 days	Calf compression device in both groups	Routine screening (3–5 days after surgery) plus any symptomatic VTE during follow-up	Venous ultrasonography	6 weeks	1.32 [0.76–2.29]
Zhou 12	China	60	60	66.4 (7.6)	64.1 (6.7)	1.31	1.07	100 mg/d, for 30 days	Dalteparin sodium 2500 IU/d, for 30 days	NA	Routine screening (3,7,30,60, and 90 days after surgery)	Venous ultrasonography	90 days	1.40 [0.47–4.17]
Zou 18	China	110	112	62.7 (47–79)	65.7 (54–80)	2.93	4.6	100 mg/d, for 14 days	Enoxaparin 4000 U/d, for 14 days	Elastic bandages and ankle pump in both groups	Routing screening (2 and 4 weeks after surgery)	Venous ultrasonography	4 weeks	1.31 [0.69–2.50]

DVT, deep vein thrombosis; LMWH, low-molecular-weight heparin; NA, not addressed; RR, risk ratio; VTE, venous thromboembolism.