The Impact of L4-5 Minimally Invasive Transforaminal Lumbar Interbody Fusion on Two-year Adjacent-Level Parameters

Abstract

ObjectiveThis study evaluates the impact of L4-5 minimally invasive surgery (MIS)-TLIF on adjacent-level parameters. MethodsThis is a retrospective study performed on consecutive patients between January 2015–December 2019. The index- and adjacent-level segmental lordosis (SL) and disc angle (DA) were measured. Patient-reported outcomes (PROs) were collected preoperatively and at 3–24 months postoperatively. Factors influencing changes in adjacent-level parameters and the occurrence of adjacent segment degeneration (ASDeg) were assessed. ResultsOne hundred and seventeen adult patients, averaging 65.5 years of age and slight preponderance of female (56.4%), were analyzed. L4-5 SL decreased at 2 years (p<0.05), but L4-5 DA significantly increased at all timepoints (p<0.05). While L3-4 SL and DA significantly decreased at all timepoints (p<0.05), L5-S1 SL decreased at 3 and 12 months (p<0.05) and L5-S1 DA only significantly decreased at 2 years (p<0.05). All PROs improved significantly (p<0.0001). The ASDeg rate was 19.7% at 2.2 years. Cephalad and caudal ASDeg rates were 12.0% and 10.3%, respectively. Eight patients (6.8%) required adjacent-level reoperations, mainly at L3-4 (6 cases). The use of expandable cage significantly reduced the odds of caudal ASDeg (OR 0.15, p=0.037), but had no significant effect on cephalad ASDeg.. ConclusionsL4-5 MIS-TLIF had a more consistent effect on L3-4 than L5-S1. Although adjacent-level SL and DA decreased over time, their association with ASDeg appears limited, suggesting a multifactorial etiology. L4-5 MIS-TLIF provides demonstrable clinical benefits with lasting PRO improvements and low adjacent-level reoperations.