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Fusion Construct Settling Down After Deformity Correction for Degenerative Sagittal Imbalance. BACKGROUND AND OBJECTIVES: To restore lumbar lordosis in the context of deformity correction for degenerative sagittal imbalance (DSI), a cage is inserted using lateral lumbar interbody fusion. Nevertheless, a reduction in lordosis can be manifested during the follow-up period. This study assessed the alterations in lumbar lordosis within the fusion construct over the patient follow-up period and identified factors linked to the reduction of lumbar lordosis after a deformity correction in cases of DSI. METHODS: This retrospective analysis encompassed 124 patients who underwent deformity correction and had a follow-up exceeding 2 years postoperatively. Based on the criterion of a lordosis reduction ≥ 5° during the follow-up, patients were stratified into a lordosis maintenance group (Group M, n = 86) and a lordosis loss group (Group L, n = 38). We examined demographic, radiological, and surgical factors influencing lordosis reduction and delineated the trajectory of lordosis reduction throughout the follow-up. RESULTS: The degree of lordosis reduction averaged 9.79° ± 4.38° in Group L and 1.42° ± 1.94° in Group M (P < .001), with most occurring within 3 months postsurgery (from 62.0° ± 8.9° to 52.2° ± 8.64°, P < .001). Radiologically, endplate injury and cage subsidence did not significantly differ between the groups (P = .146, .200). Surgically, posterior column osteotomy was significantly more prevalent in Group L in multivariate analysis (adjusted odds ratio, 3.524; P = .020). CONCLUSION: Approximately 30% (38/124) of patients experience fusion construct settling after deformity correction for DSI, predominantly within 3 months postoperation regardless of endplate injury and cage subsidence. The occurrence is notably higher in instances where a posterior column osteotomy is performed.