Introduction: Pseudarthrosis is one of the postoperative complications of lumbar interbody fusion. The risk of pseudoarthrosis was reported 5-35%. Vertebral signal changes have been identified as predictors of bone union in compression fractures, but it remains unclear whether vertebral bone marrow edema on early postoperative MRI can predict interbody fusion. The purpose of this study is to investigate the relationship between early postoperative bone marrow edema and intervertebral bone fusion.
Methods: This study included 153 patients who underwent single-level lumbar interbody fusion surgery at our institution between April 2020 and May 2023. Fusion was assessed using CT scans taken at 3, 6, and 12 months postoperatively. We evaluated fusion rates as well as incidences of vertebral endplate cyst, trabecular bone remodeling, and cage subsidence (≥3 mm). Characteristic changes in the bone trabeculae of the adjacent vertebral bodies were defined as trabecular bone remodeling (Segi N, et al. Global Spine J 2024). Early postoperative bone marrow edema was assessed using MRI T1-weighted images taken at 3 weeks postoperatively. Low signal area around the endplate was defined as edema type. The patients were classified into two groups: no edema group and edema group.
Results: There were 22 cases in no edema group and 131 in edema group. No significant differences were found between the two groups regarding age, gender, body mass index, smoking status, and diabetes co-morbidity. Fusion rates were significantly higher in no edema group at 3, 6, and 12 months (86.3%, 86.3%, and 90.9%) compared to the edema group (37.4%, 45%, and 67.1%). Trabecular bone remodeling was observed significantly higher in the no edema group (63.6%, 68.1%, and 68.1%) than the edema group (36.6%, 40%, and 36.9%). Vertebral endplate cyst was observed significantly lower in the no edema group (0%, 0%, and 0%) than the edema group (22.9%, 24.6% and 18.5%). Cage subsidence tended to occur less frequently in the no edema group (4.5%, 4.5%, and 4.5%) than the edema group (16%, 20%, and 21.5%), but the differences were not significant.
Discussion: Fusion rate was higher in no edema group than edema group throughout the postoperative period. Bone marrow edema on early postoperative MRI might be a predictor of unsuccessful healing of interbody fusion.