Paraspinal Muscle Functional Cross-Sectional Area Alterations in Single-Level Open and Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Correlational Analysis.

Abstract

Retrospective cohort study. To compare the functional cross-sectional area (FCSA) of paraspinal muscles in patients undergoing single-level open transforaminal lumbar interbody fusion (Open-TLIF) versus minimally invasive TLIF (MIS-TLIF) and to assess correlations between muscle changes and clinical outcomes, including lumbar Visual Analogue Scale (VAS), leg VAS, and Oswestry Disability Index (ODI). Paraspinal muscle atrophy is linked to poorer outcomes after lumbar spine surgery. Minimally invasive techniques may reduce muscle damage. Understanding the degree of muscle preservation and its relationship to recovery can guide surgical decision-making. This study included 129 patients (Open-TLIF: 60; MIS-TLIF: 69) who underwent single-level TLIF between September 2020 and December 2024, with at least 1 year of follow-up. Computed tomography (CT) measured FCSA of the multifidus, erector spinae, and psoas muscles at index and adjacent levels. Correlation and regression analyses evaluated relationships between FCSA changes, surgical method, and clinical outcomes (lumbar VAS, leg VAS, ODI). Open-TLIF patients had significantly greater reductions in FCSA of the index and adjacent multifidus and index erector spinae muscles. MIS-TLIF patients showed lower lumbar VAS and ODI scores at final follow-up. Index multifidus FCSA loss correlated with worse lumbar VAS (r = -0.253, P = 0.004) and ODI (r = -0.477, P<0.001). MIS-TLIF was significantly associated with multifidus preservation (r = 0.837, P<0.001). Increased psoas FCSA correlated positively with ODI improvement (r = 0.229, P = 0.009) but negatively with erector spinae FCSA (r = -0.221, P = 0.033). MIS-TLIF is associated with significantly less paraspinal muscle atrophy and better lumbar VAS and ODI outcomes compared with Open-TLIF. Preservation of the multifidus muscle is strongly linked to clinical improvement, and increased psoas FCSA contributes to better disability outcomes. Level II.