L5-S1 Foraminal Stenosis Degeneration after L4-5 Lumbar Spinal Stenosis for TLIF: Impact of Preoperative Spinal Muscle Quality

Abstract

Study design: Retrospective cohort analysis. Objective: Our study aimed to investigate the effect of preoperative lumbar muscle quality (including muscle cross-sectional area (CSA) and muscle fatty infiltration rate (FIR) on L5-S1 foraminal stenosis degeneration after L4-5 TLIF. Summary of Background Data: Adjacent segment degeneration (ASD) was a major spinal fusion complication. The paraspinal muscle had been proven to be an essential factor influencing the happening of ASD. However, few studies had investigated the association between paraspinal muscle and adjacent segment foraminal stenosis degeneration (ASD-FS). Methods: One hundred-thirteen patients diagnosed with lumbar spinal stenosis at L4-5 were involved. Paraspinal muscle measurements were obtained preoperatively and bilaterally from axial T2-weighted MR images. The parameters included the, psoas cross-sectional area (p-CSA), erector spinae cross-sectional area (es-CSA), multifidus cross-sectional area (m-CSA), psoas fatty infiltration rate (p-FIR), erector spinae fatty infiltration rate (es-FIR), and multifidus fatty infiltration rate(m-FIR). The foraminal parameters were obtained in the Computed Tomography system bilaterally, including posterior disc height (PDH), disc-to-facet distance (D-F), foraminal height (FH), and foraminal area (FA). The association between muscle quality and ASD-FS had also been studied. Results: At the last follow-up, the DF, FH, and FA were significantly decreased compared to pre-operation, and the decrease in FA was significantly positively related to es-FIR and m-FIR. Conclusion: FIR for lumbar muscles preoperative was a predictor for L5-S1 ASD-FS after TLIF surgery, and patients who had higher es-FIR and higher m-FIR were more inclined to develop L5-S1 ASD-FS.