ELSA-ATP is an expandable lumbar interbody spacer engineered for the Anterior-to-Psoas lateral approach to reduce psoas retraction. Inserted at a minimal height to limit endplate impaction, it expands in place to achieve a lateral footprint with integrated fixation. The device includes a large graft chamber to support fusion and accommodates either anchors or screws for versatile stabilization. Angled instrumentation enhances access at levels such as L4–L5 where a high iliac crest may obstruct a standard lateral path. Its design supports stable fusion while minimizing approach-related morbidity.