Comparison 16. Orthopaedic (spinal) (subgroup: timing).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
16.1 Transfusions	3	194	Risk Ratio (M‐H, Random, 95% CI)	0.44 [0.31, 0.63]
16.1.1 Intraoperative	2	144	Risk Ratio (M‐H, Random, 95% CI)	0.43 [0.26, 0.71]
16.1.2 Postoperative	1	50	Risk Ratio (M‐H, Random, 95% CI)	0.50 [0.05, 5.17]
16.2 Volume of transfusion (units) (PPR)	3	208	Mean Difference (IV, Random, 95% CI)	‐0.99 [‐2.49, 0.50]
16.2.1 Intraoperative	2	145	Mean Difference (IV, Random, 95% CI)	‐1.39 [‐3.48, 0.71]
16.2.2 Postoperative	1	63	Mean Difference (IV, Random, 95% CI)	‐0.21 [‐0.63, 0.21]
16.3 Volume of transfusion (units) (PPT)	1		Mean Difference (IV, Random, 95% CI)	Totals not selected
16.3.1 Intraoperative	1		Mean Difference (IV, Random, 95% CI)	Totals not selected
16.4 Blood loss (mL)	3	208	Mean Difference (IV, Random, 95% CI)	‐121.37 [‐245.90, 3.15]
16.4.1 Intraoperative	2	145	Mean Difference (IV, Random, 95% CI)	‐111.92 [‐238.45, 14.60]
16.4.2 Postoperative	1	63	Mean Difference (IV, Random, 95% CI)	‐413.00 [‐1115.93, 289.93]
16.5 Infection	1		Risk Difference (M‐H, Random, 95% CI)	Totals not selected
16.5.1 Postoperative	1		Risk Difference (M‐H, Random, 95% CI)	Totals not selected
16.6 Wound complication	1		Risk Ratio (M‐H, Random, 95% CI)	Totals not selected
16.6.1 Intraoperative	1		Risk Ratio (M‐H, Random, 95% CI)	Totals not selected
16.7 PE	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected
16.7.1 Postoperative	1		Peto Odds Ratio (Peto, Fixed, 95% CI)	Totals not selected