Absence of Bone Marrow Edema on Early Postoperative MRI Predicts Fusion Outcome After Single-Level Lumbar Interbody Fusion

Purpose: This study aimed to investigate whether bone marrow edema observed on MRI at three-postoperative week can predict fusion status in a single-level lumbar interbody fusion. Methods: This retrospective study included 152 patients who had undergone a single-level lumbar interbody fusion with a minimum of one-year follow-up. All patients underwent MRI at three weeks after surgery and CT scans at 3, 6, and 12 postoperative months. CT scans were used to evaluate fusion status, presence of vertebral endplate cyst (VEC), trabecular bone remodeling (TBR), and cage subsidence. Patients were divided into two groups based on MRI findings: those with bone marrow edema (edema group) and those without (non-edema group). Bone marrow edema was defined as a low-intensity area within the adjacent vertebral bodies on T1-weighted images. Clinical and radiographic outcomes were compared between groups. Results: Of 152 patients, 117 were assigned to the edema group and 35 to the non-edema group. The non-edema group demonstrated significantly higher fusion rates at 3, 6, and 12 months postoperatively. Additionally, the non-edema group showed a significantly lower incidence of VEC and a higher frequency of TBR. Cage subsidence was not observed in any patients in the non-edema group, whereas 22.2% of patients in the edema group exhibited cage subsidence at 12 months. Conclusion: Absence of bone marrow edema on MRI assessment at three postoperative week was associated with significantly higher fusion rates. These results suggest that absence of early bone marrow edema may serve as a predictor of successful fusion after single-level lumbar interbody fusion.