Expandable Interbody Spacers: A Two-Year Study Evaluating Radiologic and Clinical Outcomes With Patient-Reported Outcomes

Abstract

Background: Posterior and transforaminal lumbar interbody fusion (PLIF and TLIF) have gained significant popularity for management of lumbar degenerative spine over the last 3 decades. Expandable interbody spacers are a newer technology that can increase in size after placement, theoretically minimizing the operative risks of static spacers without sacrificing radiographic correction. The goal of this study is to further evaluate the radiographic and clinical outcomes of expandable spacers.Methods: This was a retrospective analysis of a prospective cohort that underwent elective 1-to 3-level PLIF/ TLIF with expandable interbody spacers from 2014 to 2020 at a single institution. Patient-reported outcome measures (PROMs) Oswestry Disability Index and Visual Analog Scale were collected at 6 weeks, 3 months, 6 months, and 12 months. Imaging was performed at 12 months, with follow up at 24 months in case of nonunion. Retrospective outcomes were computer tomography (CT) based and Bridwell-Lenke classification of fusion, radiographic parameters, and adverse events.Results: A total of 50/53 (94.3%) otherwise eligible patients had 12-month PROMs and CT imaging for analysis. Here, 50% were obese (body mass index . 30), 58% had a smoking history, and 24% had a prior lumbar procedure. Also, 46/50 (92%) patients fused by CT criteria. Significant decrease in PROMs was seen as early as 6 weeks postoperatively. The mean change in preoperative-to-postoperative global lordosis values was 3.88 6 15.68. There were 4 (8%) intraoperative durotomies and 5 (10%) patients requiring reoperation for nonunion.Conclusions: Our study demonstrates the use of expandable spacers in a high comorbidity cohort with low complications, excellent improvement in PROMs despite minimal lordotic improvement, and high rates of fusion without recombinant human bone morphogenetic protein-2 (rhBMP-2) or iliac crest bone graft.Level of Evidence: 4. Clinical Relevance: Expandable interbody fusion can significantly improve outcomes for degenerative lumbar spondylosis, with good safety profile, and high fusion rates.

Static versus Expandable Interbody Fusion Devices: A Comparison of 1-Year Clinical and Radiographic Outcomes in Minimally Invasive Transforaminal Lumbar Interbody Fusion

“…Consistent with prior studies, we noted statistically significant perioperative improvements in PROMs in both groups at 3-month and 1-year follow-up [9,[22][23][24][25]. However, there were no differences in PROMs at each time point when groups were compared.…”

“…Failure to restore lordosis adequately increases the likelihood of continued lumbago, biomechanical instability, and uneven loading across the posterior spinal column [5,6,26]. Several studies documented significant increases in segmental lordosis with expandable cages [10,12,[23][24][25]27]. Notably, one study found that using expandable devices across two levels resulted in greater segmental and regional lumbar lordosis [25].…”

“…Various studies have reported favorable radiographic results with expandable cages for MIS-TLIF [ 9 , 22 , 23 ]. Kim et al [ 22 ] assessed the radiographic outcomes in a cohort of 50 expandable cages and reported significant increases in the disk and foraminal heights that were maintained 2 years postoperatively.…”

Does the application of expandable cages in TLIF provide improved clinical and radiological results compared to static cages? A meta-analysis

“…Expandable cages were designed to alleviate these difficulties by permitting insertion in a collapsed state and expansion in situ , enhancing the ease of insertion, and reducing iatrogenic endplate damage caused by impaction ( 11 , 12 ). The design of this device may reduce neural retraction, endplate injury, implant subsidence and/or migration, and allow expansion in the interbody space, maximizing the disc space height ( 13 ).…”