Minimally Invasive Transforaminal Lumbar Interbody Fusion: Comparison of Low versus High-Grade Isthmic Spondylolisthesis

Presented at SMISS Annual Forum 2016
By Kern Singh MD
With Dustin Massel BS, Benjamin Mayo BA, Ankur Narain BA, Fady Hijji BS, Krishna Kudaravalli BS, Kelly Yom BA,

Disclosures: Kern Singh MD A; CSRS Resident Grant. B; DePuy, Zimmer, Stryker, CSRS, ISASS, AAOS, SRS, Vertebral Column - ISASS. D; Avaz Surgical, LLC, Vital 5, LLC. F; Zimmer, Stryker, Pioneer, Lippincott Williams & Wilkins, Th Dustin Massel BS None, Benjamin Mayo BA A; CSRS Resident Grant., Ankur Narain BA None, Fady Hijji BS None, Krishna Kudaravalli BS None, Kelly Yom BA None,


Minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) is often used to treat low-grade isthmic spondylolisthesis (IS). No studies have compared surgical outcomes
for low and high-grade isthmic spondylolisthesis following an MIS TLIF.


To compare surgical outcomes between low (grade 1) and high-grade (grade 2 and above) isthmic spondylolisthesis following a minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).


A prospectively maintained surgical database of patients who underwent a primary 1-level MIS TLIF for the treatment of IS between 2007-2015 was reviewed. Low-grade IS (grade 1) patients underwent a unilateral tubular approach with a single interbody cage and bilateral pedicle screw instrumentation, whereas high-grade IS (grade 2 and above) patients underwent a bilateral tubular approach with bilateral interbody cage placement. Baseline patient demographics and characteristics were compared between cohorts using Student’s t-test and Chi-square analysis. Differences in peri- and postoperative outcomes between cohorts were assessed using Poisson regression with robust error variance or linear regression adjusted for preoperative and procedural characteristics. 


A total of 65 patients underwent MIS TLIF for IS. Of these, 22 (33.8%) were low-grade while 43 (66.2%) were high-grade. The low-grade cohort was younger (41.8 vs 50.5 years, p=0.016) and had a higher percentage of patients with a BMI <25 or ≥35 (p=0.030) when compared to the high-grade cohort. There were no other differences in preoperative variables. No significant differences in operative time, estimated blood loss (EBL), length of hospital stay, postoperative VAS scores, or complication and revision rates were demonstrated between the two cohorts. Arthrodesis rate was slightly lower in the low-grade IS cohort, though not statistically significant.


Despite the low-grade IS cohort being younger and having a less severe diagnosis, the high-grade IS cohort experienced similar improvements and clinical outcomes. This finding may be due to the high-grade IS cohort receiving bilateral interbody cages, potentially providing a better fusion environment. The results of this study suggest that MIS TLIF provides sufficient stabilization and fusion for the treatment of high-grade IS in spite of the increased preoperative vertebral body slipping.