Objective:To analyze the application and clinical efficacy of one-stage unilateral or bilateral fenestration, debridement, interbody fusion combined with posterior internal fixation for the treatment of lumbosacral brucellosis spondylitis.Methods:All patients with lumbosacral brucellosis spondylitis were retrospectively analyzed, who underwent fenestration, debridement, interbody fusion combined with posterior internal fixation from June 2013 to June 2019. A total of 48 patients were enrolled in this study. According to the surgical method, they were divided into two groups. Unilateral fenestration group: 27 cases of one-stage posterior unilateral fenestration, debridement, interbody fusion combined with posterior internal fixation were performed, 21 males and 6 females, aged 23-71 years; Bilateral fenestration group: 21 cases of one-stage posterior bilateral fenestration, debridement, interbody fusion combined with posterior internal fixation were performed, aged 26-58 years. There were 16 males and 5 females. The preoperative and postoperative clinical symptoms, neurological function, C-reactive protein, the surgery duration time, the blood loss, and erythrocyte sedimentation rate were observed. The internal fixation device was evaluated for looseness or fracture by imaging examination. The Bridwell classification criteria were used to evaluate the bone graft fusion. Postoperative complications were also assessed.Results:All patients completed the operation successfully, and the diseased tissues were sent for pathological examination during the operation, and all of them were diagnosed as brucellosis. All patients were followed up for 12-48 months (mean 23.7 ±6.3 months). C-reactive protein, erythrocyte sedimentation rate, Visual Analogue Scale (VAS), Oswestry Disability Index (ODI) and Japanese Orthopaedic Association Scores (JOA) were significantly improved in both groups at different time points after operation. There was no significant difference in the general condition before operation between the two groups ( P>0.05). The mean operation time and mean blood loss were 120.5±34.1 min and 214.4±150.2 ml, in the unilateral fenestration group; 187.1±30.3 min and 455.8±250.5 ml in the bilateral fenestration group; and the difference was significant ( t=8.123, t=2.962, P<0.05) . The postoperative lumbar and leg pain were significantly relieved. There was no significant difference in C-reactive protein, erythrocyte sedimentation rate, VAS, ODI and JOA scores between the two groups at the same time point. In the bilateral fenestration group, one patient developed incision infection half a month after the operation, who underwent debridement and drainage, and finally cured. There was no significant difference in the time of bone graft fusion between the two groups ( t=0.542, P>0.05). At the last follow-up, all the patients were completely fused. Conclusion:Unilateral or bilateral fenestration, debridement and bone graft fusion and internal fixation for the treatment of lumbosacral brucellosis spondylitis can achieve good clinical results, and the former has the advantages of short operation time and low cost.