Delayed Onset Postoperative Spinal Epidural Hematoma After Lumbar Spinal Surgery: Incidence, Risk Factors and Clinical Outcomes

Background: Posterior spinal epidural hematoma (PSEH) often develops after the surgery within 24 hours. On rare occasions, PSEH happened after 3 days, up to two weeks, which were classified as delayed onset PSEH. Due to its rarity, previous studies only described the clinical features, whereas risk factors cannot be able to assess. Methods: Patients who developed PSEH requiring hematoma evacuation between December 2013 and January 2020 were included and divided into early onset (Group A) and delayed onset group (Group B) based on the time of symptom onset (72 hours). For each PSEH patients, 3 controls (Group C) who did not develop the PSEH in the same period were randomly selected. Clinical features were compared among three groups and multiple logistic regression analysis was performed to identify the risk factors for group A and B. Results: 32 patients (0.35%) were identified as the early onset PSEH (occurred at 10.68  11.5h) and 15 (0.16%) patients were the delayed onset ones (occurred at 130.60  61.78h). When compare the group A and B, group A showed higher rate of multilevel procedure (Group A: 75%, Group B: 40%, p=0.02), lower drainage (Group A: 239.69±245.70, Group B: 613.67±599.83, p=0.004), lower APTT (Group A: 31.55±4.07, Group B: 35.63±7.24, p=0.018) and higher JOA score at discharge (Group A: 20.68±4.72, Group B: 17.67±4.79, p=0.039). Multiple logistic regression analysis identified multilevel procedure (OR: 5.62, 95% CI: 1.84-17.25), postoperative systolic blood pressure (SBP)(OR: 1.10, 95% CI: 1.06-1.15) and abnormal coagulation (OR: 5.68, 95% CI: 1.74-18.52) as the independent risk factors for group A, whereas for group B, postoperative SBP (OR: 1.10, 95% CI: 1.04-1.16) and previous spinal surgery (OR: 4.74, 95% CI: 1.09-20.70) at the same level were the risk factors. Conclusions: Our study revealed the overall incidence of delayed onset PSEH was 0.16% in posterior lumbar spinal surgery and the risk for it was different from early onset PSEH. For the early onset PSEH, multilevel procedure, postoperative SBP and abnormal coagulation were the risk factors and for the delayed onset PSEH, the postoperative SBP and previous spinal surgery at the same level were the independent risk factors.