Disparity between early radiographic decompression and one-year patient satisfaction after single-level LLIF: proposal of the structural improvement score (SIS) and QOL improvement score (QIS)

SIS and QIS provide complementary information on structural and functional recovery after LLIF. QIS demonstrated a moderate association with satisfaction, whereas residual pain remained the dominant determinant. These indices should be considered exploratory and require external validation, psychometric testing, and prospective multicenter studies before routine clinical use.