L1–S1 Posterior Paraspinal Muscle Fatty Infiltration and a Radiomics Signature Predict Prolonged Length of Stay After Lumbar Spine Surgery in Older Adults

In older adults undergoing lumbar fusion, global multilevel paraspinal degeneration measured by conventional FI provides major incremental value for predicting prolonged LOS beyond clinical and geriatric factors, while posterior paraspinal radiomics offers an additional but more modest improvement. Leakage-free validation supports the robustness and clinical relevance of integrating automated muscle quantification with imaging-based risk stratification.