Introduction: Restoration of lordosis at the L5/S level is a key determinant of successful sagittal alignment in adult spinal deformity (ASD) surgery. However, advanced degeneration at this segment markedly limits mobility, making lordosis restoration particularly challenging through posterior approaches. The purpose of this study was to evaluate whether the combination of lateral interbody release (LIR) and rim cage placement (RP) facilitates effective lordosis restoration at L5/S while reducing endplate-related complications.

Methods: Among 188 consecutive patients who underwent corrective fusion surgery for ASD including L5/S interbody fusion between January 2013 and September 2024, 86 patients with preoperative L5/S lordosis ≤10° were retrospectively analyzed. All patients underwent posterior interbody fusion at L5/S as part of deformity correction. Rim placement was defined as cage positioning with the cage center located lateral to the medial border of the pedicle. Patients were divided into an LIR + RP group (n = 35) and a non-RP group (n = 52). Pre- and postoperative L5/S lordosis angles and the incidence of endplate injury were assessed using computed tomography.

Results: Preoperative L5/S lordosis did not differ significantly between the two groups (5.1° vs 5.8°). Postoperative L5/S lordosis and lordosis gain were significantly greater in the LIR + RP group compared with the non-RP group (12.5° vs 6.5°, and 7.0° vs 0.7°, respectively; p < 0.001). Endplate injury occurred in 3 patients (8.6%) in the LIR + RP group and in 23 patients (48.0%) in the non-RP group, indicating a significantly higher incidence in the non-RP group (p < 0.001).

Conclusion: The combination of lateral interbody release and rim cage placement enables substantial lordosis restoration at the rigid L5/S segment while significantly reducing endplate injury. This strategy overcomes the inherent limitations of posterior interbody fusion at the lumbosacral junction and enhances the quality and safety of sagittal correction in adult spinal deformity surgery.