Minimally Invasive Transforaminal Lumbar Interbody Fusion: Comparison Of Isthmic Versus Degenerative Spondylolisthesis

Background: Minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) is a common surgical procedure for treatment of degenerative spondylolisthesis (DS) but remains controversial for treatment of isthmic spondylolisthesis (IS). Few studies have compared IS and DS outcomes after MIS TLIF. Therefore, the objective of the current study was to compare outcomes of patients with IS and DS after MIS TLIF.Methods: A retrospective cohort analysis was performed on a prospectively maintained database of patients who underwent a primary, 1-level MIS TLIF for grade I or II IS or DS. Grade I and II DS and grade I IS patients were treated with MIS TLIF via a unilateral tubular approach, whereas the grade II IS patients were treated via a bilateral tubular approach. Differences in patient demographics and preoperative characteristics were assessed using independent sample t tests and chi(2) tests. The type of spondylolisthesis and its effect on postoperative outcomes was analyzed using Poisson regression with robust error variance (binary outcomes) or linear regression (continuous outcomes) adjusted for preoperative characteristics. Subgroup analysis comparing grade I IS versus DS and grade II IS versus DS was performed.Results: A total of 223 patients were included (IS: 62 [27.8%]; DS: 161 [72.2%]). IS patients were younger (P<001), had a lower comorbidity burden (P<.001), and a greater incidence of grade II spondylolisthesis (P<.001) at L5-S1 (P<.001) than the DS cohort. Patients with IS experienced longer operative times (P<.001) and lower, but not statistically significant, arthrodesis rates compared to the DS cohort. No differences were observed in the remaining preoperative patient characteristics, perioperative or postoperative outcomes.Conclusions: Despite being younger and having a lower comorbidity burden than the DS cohort, similar outcomes were observed after MIS TLIF for IS patients.Level of Evidence: 3.Clinical Relevance: These results suggest MIS TLIF is an appropriate treatment option for IS patients despite the increased instability inherent with IS.