Does Minimally Invasive Lumbar Spine Fusion Reduce Adjacent Segment Degeneration? A Matched-Pair Analysis With 8-Year Follow-up

Objective: This study aimed to compare the long-term radiographic incidence of adjacent segment degeneration (ASD) following minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) versus open TLIF (O-TLIF) in a matched cohort, and to identify radiographic parameters associated with the development of kyphosis-type ASD.Methods: A retrospective matched-pair analysis was conducted involving 60 patients (30 MIS-TLIF and 30 O-TLIF) who underwent single-level TLIF between 2004 and 2009 and had a minimum follow-up of 8 years. Patients were matched for age (±3 years), sex, body mass index (±2 kg/m²), and operative level. Radiographic ASD was defined as greater than 50% disc-height loss, greater than 3 mm of listhesis, or greater than 10° of kyphotic change at the adjacent segment. Continuous variables were analyzed using independent-sample t-tests or Mann-Whitney U-tests, as appropriate, and categorical variables were analyzed using chi-square or Fisher exact tests, with statistical significance set at p<0.05.Results: The mean follow-up duration was 8.9±1.2 years. The MIS-TLIF group had a significantly shorter hospital stay than the O-TLIF group (3.4±1.7 days vs 6.0±2.3 days, p<0.001). Radiographic ASD occurred significantly less frequently in the MIS-TLIF group at 2 years (3.3% vs. 23.3%, p=0.023), but no significant difference was observed at ≥8 years of follow-up (43.3% vs. 50.0%, p=0.605). An increased Cobb angle at the superior adjacent level was significantly associated with kyphosis-type ASD (p=0.017). No demographic characteristics or preoperative magnetic resonance imaging parameters were found to predict ASD occurrence.Conclusion: MIS-TLIF demonstrated an early radiographic advantage in reducing ASD compared with O-TLIF; however, this advantage diminished over time. Long-term ASD appears to be multifactorial, with sagittal imbalance playing a more prominent role in the progression of kyphosis-type ASD than the surgical approach itself.