Abstract:Abstract: [Objective] To analyze the hidden blood loss and related factors after oblique lumbar interbody fusion for lumbar degenerative diseases. [Methods] A retrospective analysis was performed on 45 patients with lumbar degenerative disease treated by OLIF in our hospital from May 2016 to December 2019. Hematocrit, hemoglobin and intraoperative and postoperative dominant blood loss were recorded before and 2 days after operation. The hidden blood loss was calculated by Nadler and Gross equation. The patients were grouped by gender, age, body mass index, diabetes, hypertension, operation time, number of surgical levels, learning curve, type of bone graft, use of tranexamic acid, and spinal deformity. Rank-sum test was used to compare the relevant factors. [Results] In this study, the average total blood loss was (758.95±393.05)ml, the average dominant blood loss was (120.78±108.31)ml, and the average hidden blood loss was (638.17±371.75) ml, accounting for (81.09±16.54)% of the total blood loss. Postoperative hemoglobin and Hematocrit decreased to varying degrees. The rank-sum test results showed that the operative time, learning curve and use of tranexamic acid had statistical significance on hidden blood loss (P < 0.05), and multiple linear stepwise regression analysis showed that learning curve and use of tranexamic acid were the influencing factors of hidden blood loss in OLIF. [Conclusion] There is a lot of hidden blood loss in the treatment of lumbar degenerative diseases with OLIF technique. Hidden blood loss is closely related to learning curve and use of tranexamic acid, which should be paid attention to by clinicians.