OLF is a primary reason for thoracic myelopathy, and it can result in paralysis of the lower extremities in severe cases. It usually causes blunt spinal compression, and conservative treatment is usually ineffective. Surgery is the only effective method to treat OLF . However, surgical intervention of the thoracic spine has high incidence of complications [16, 17]. SSI after posterior thoracic spine surgery is the most common complication and the reason for revision surgery. The incidence of postoperative SSI ranges from less than 3% in discectomy and laminectomy to approximately 12% in instrument fusion surgery. The effect of SSI on morbidity and clinical outcome cannot be ignored [19, 20]. Our study found that intraoperative administration of 500 mg MP accelerated the 2-week neurological recovery of patients with thoracic myelopathy due to OLF. However, an increase in infection rate was also observed in those who received intraoperative 500 mg MP.
Steroids can alleviate inflammatory responses by inhibiting chemotactic accumulation of inflammatory cells, adhesion of leukocytes, and release of histamine and kinins. Steroids have been shown to reduce phospholipase A2 activity, inhibit nociceptive C fiber conduction, stabilize cell membranes, and inhibit prostaglandin synthesis . MP is the least irritant and the most effective steroids, with the longest time . There is an evidence that in spinal surgery, steroids reduce neuropathic pain by preventing spontaneous nerve discharge from injured nerves . In addition, preoperative steroids can repair systemic inflammatory responses and inhibit iatrogenic defects . Furthermore, it has been reported that steroids protect neurons from inflammation without impairing the composition of circulating immune cells, thereby reducing perioperative neurological complications following cervical decompression surgery . The mechanism of action of steroids is not fully understood. Thus, future studies are required to advance our understanding of this mechanism .
Although the effect of management with intraoperative steroids on postoperative complications and prognosis of spinal surgery is still unclear, some spine studies found no correlation between steroid use and better postoperative outcomes. For example, a prospective study by Bednar et al.  indicated that patients treated with and without intraoperative steroid showed no significant difference in wound healing or infection rate. In fact, some studies have shown negative postoperative prognosis associated with intraoperative steroid treatment. Christian et al.  found that intraoperative steroid management had no effect on the postoperative outcome of cervical spine surgery, and that it increased the rate of wound infection. Similarly, our study confirmed that intraoperative steroid administration had no effect on the long-term outcome of thoracic spine surgery, and that SSI rate was higher in patients who received intraoperative steroid than in those who did not. However, unlike previous studies, the present study also found that steroids promoted the recovery of neurological function within two weeks.
On the contrary, perioperative and intraoperative applications of steroids were found to be effective in several studies. For example, a prospective study reported that patients treated with perioperative steroids showed significant improvement in short-term and long-term functional outcomes . In addition, Song et al.  indicated that short-term use of systemic MP after anterior cervical discectomy and fusion was effective in reducing dysphagia and reducing prevertebral soft tissue swelling. Moreover, short-term application of MP was not associated with postoperative infection. Furthermore, Anders et al. found that steroid treatment reduced pain and improved functional outcome and prolonged hospital stay after microscopic disc surgery. An analogous study showed that patients receiving steroids for lumbar decompression or cervical radiculopathy had shorter hospital stay and less postoperative pain . Similarly, our study showed that the recovery of neurological function in patients treated with intraoperative MP was accelerated within two weeks.
In our study, better neurological outcomes were found in MP group at short-term follow-up, but no significant differences were observed between the two groups at long-term follow-up, indicating that MP may only contribute to short-term recovery of spinal cord function. This phenomenon could be partially explained by the short half-life of MP [11, 29]. In a meta-analysis of MP in spinal cord injury, the authors enrolled two RCTs and concluded that MP was associated with a significant motor score improvement at short-term follow-up but not at long-term follow-up . However, for observational studies subgroup analysis, no positive associations were found between MP and motor score improvement at short-term or long-term follow-up . In addition, for postoperative neurologic worsening in our study, no statistical difference was found between the two groups, making this short-term effect of neurological recovery of MP more limited.
Nevertheless, this study had several limitations. First, owing to the retrospective nature of this study, all items were retrospectively collected and analyzed; thus, the analysis was weak. Second, the small sample size could have generated selection bias. Despite these limitations, however, our study indicated that intraoperative MP administration accelerated the recovery of spinal cord function within two weeks after posterior approach surgery for OLF, but also increased postoperative infection rate.