Table 2 Summary of key outcomes, findings, and strength of evidence. Abbreviations: RCT, randomized controlled trial; SMD, standardized mean difference; CI, confidence interval; TXA, tranexamic acid; tTXA, topical use of TXA

 Postoperative drainage output

RCT: 9 (569)

Non-RCT: 3 (213)

RCTs with sufficient sample sizes and non-RCTs with low risks of study limitations found a consistent effect that tTXA reduced postoperative drainage output more than placebo, with overall SMD − 160.62 (− 302.41, − 117.83).

High

 Postoperative drainage duration

RCT: 3 (198)

Non-RCT: 3 (213)

RCTs and non-RCTs with medium-level study limitations found a consistent and precise effect that tTXA reduced postoperative drainage duration more than placebo, with overall SMD − 0.75 (− 1.09, − 0.40).

Moderate

 Hidden blood loss

RCT: 2 (141)

Non-RCT: 1 (100)

Consistent and precise effect was found in studies with medium-level study limitations that tTXA reduced perioperative hidden blood loss more than placebo by SMD − 91.18 (− 121.42, − 60.94).

Moderate

 Hemoglobin level drop

RCT: 3 (179)

Non-RCT: 1 (40)

Few studies included. Direction of effect in non-RCT conflicted with that in RCTs, yielding an overall SMD − 0.65 (− 1.36, 0.05) with a wide (imprecise) CI.

Insufficient

Other patient-centered outcomes

 Length of hospital stay (LOH)

RCT: 7 (467)

Non-RCT: 3 (213)

Studies with medium-level study limitations yielded consistent and precise effect that tTXA reduced LOH more than placebo by SMD − 1.32 (− 1.90, − 0.74).

Moderate

 Rod fracture

Non-RCT: 1(40)

Only a single event was reported in one small non-RCT.

Insufficient

 Wound infection

RCT: 2 (110)

Non-RCT: 1(40)

Three events were reported in a few small RCT and non-RCTs, finding no significant difference in wound infection rate.

Insufficient

 Myocardial infarction

RCT: 1 (29)

Only a single event was reported in one small RCT.

Insufficient