General Session: MIS-2
Presented by: A. Narain - View Audio/Video Presentation (Members Only)
A. Narain(1), F. Hijji(1), B. Mayo(1), W. Long(1), K. Kudaravalli(1), K. Yom(1), N. Shoshana(1), K. Singh(1)
(1) Rush University Medical Center, Orthopaedic Surgery, Chicago, IL, United States
Introduction: Controversy exists regarding utilization of unilateral versus bilateral interbody cages in minimally invasive transforaminal lumbar interbody fusion procedures (MIS TLIF). Bilateral cages are used in more severe cases of deformity, and are thought to provide improved biomechanical stability. However, few studies have analyzed postoperative patient reported outcomes (PROs) as they relate to the use of unilateral versus bilateral cages. In this context, the purpose of this study is to determine differences in improvements in Oswestry Disability Index (ODI), Short Form-12 Physical Composite Summary (SF-12 PCS), and back and leg pain between MIS TLIF performed with unilateral versus bilateral interbody cages.
Methods: A prospectively maintained surgical database of patients who underwent a one-level, primary MIS TLIF for degenerative pathology with either unilateral or bilateral interbody cages between 2010-2016 was reviewed. Patients were excluded if there was incomplete preoperative PRO data. Instrumentation type was tested for association with demographics, procedural characteristics. preoperative ODI, preoperative SF-12 PCS, and preoperative Visual Analog Scale (VAS) back and leg pain scores using student's t-test, chi square analysis, and Fisher's exact test for continuous, categorical, and non-parametric variables, respectively. Changes in PRO scores between instrumentation cohorts were then compared using linear (continuous) or Poisson regression with robust error variance (categorical) adjusted for patient demographics, procedural characteristics, and preoperative PRO score.
Results: After exclusion of those with incomplete preoperative data for ODI, VAS, or SF-12 PCS, 64 patients were included in this analysis. Of these, 44 (68.75%) underwent primary MIS TLIF with unilateral cages and 20 (31.25%) underwent MIS TLIF with bilateral cages. The unilateral cage cohort was older (53.02 vs 46.59 years, p=0.031), had a greater comorbidity burden (1.86 vs 1.00, p=0.031), and was more likely to have a preoperative diagnosis of degenerative spondylolisthesis (43.19% vs. 15.00%, p=0.007). The bilateral cage cohort exhibited a trend towards being more likely to have a preoperative diagnosis of isthmic spondylolisthesis (65.00% vs. 31.82%, p=0.077). There were no differences in operative time, estimated blood loss, or length of stay between cohorts (p>0.05 for each). Additionally, there were no significant differences in improvement in ODI, SF-12 PCS, VAS Back, or VAS Leg at 6-week, 12-week, and 6-month postoperative follow up (p>0.05 for each).
Conclusion: The results of this study suggest that patients who undergo MIS TLIF with bilateral cage instrumentation have increased disease severity. Despite this discrepancy in diagnosis, both cohorts experience similar improvements in PROs at all postoperative time points. Thus, practitioners and patients should expect similar improvements in disability and pain irrespective of necessity for bilateral cage instrumentation.