Comparative Effectiveness of Laterally Placed Expandable versus Static Interbody Spacers: A 1-Year Follow-Up Radiographic and Clinical Outcomes Study

Abstract

This study compared the clinical and radiographic outcomes of patients treated with expandable and static interbody spacers following minimally invasive lateral lumbar interbody fusion (MIS-LLIF) with 12-month follow-up. Overview of Literature: A common surgical option for the treatment of degenerative disk disease (DDD) is MIS-LLIF using static or expandable spacers to restore disk height (DH), neuroforaminal height (NH), and segmental lordosis. Static spacers may require excessive trialing and aggressive impaction, potentially leading to endplate disruption and subsidence. Expandable spacers allow for in situ expansion to help address complications associated with static spacers. Methods: This is an Institutional Review Board-exempt review of 69 patients (static, n=32; expandable, n=37) diagnosed with DDD who underwent MIS-LLIF at 1-2 contiguous level(s) using static or expandable spacers. Radiographic and clinical outcomes were collected and compared at pre-and postoperative time points up to 12 months. Results: The expandable group had a significantly higher mean change in Visual Analog Scale (VAS) scores at 6 weeks, 6 months, and 12 months vs. static (∆VAS at 12 months: expandable, 6.7±1.3; static, 5.1±2.6). Mean improvement of Oswestry Disability Index (ODI) scores at 3, 6, and 12 months were significantly better for the expandable group vs. static (∆ODI at 12 months: expandable, 63.2±13.2; static, 29.8±23.4). Mean DH and NH significantly increased at final follow-up for both groups, with no significant difference in DH improvement between groups. The expandable mean NH improvement at 6 weeks and 6 months was significantly greater vs. static. Segmental lordosis significantly improved in the expandable group at all time intervals vs static. Subsidence rate at 12 months was significantly lower in the expandable group (1/46, 2.2%) vs. static (12/37, 32.4%). Conclusions: Expandable spacers resulted in a significantly lower subsidence rate, improve segmental lordosis, and VAS and ODI outcomes at 12 months vs. static.

Poor Bone Quality, Multilevel Surgery, and Narrow and Tall Cages Are Associated with Intraoperative Endplate Injuries and Late-onset Cage Subsidence in Lateral Lumbar Interbody Fusion: A Systematic Review

“…According to Marchi's criteria [25], Grades 0 and I were considered low-grade and mild subsidence, respectively, while Grades II and III were considered highgrade and severe subsidence, respectively. (2) Ten studies defined cage subsidence as disc space loss more than a specific distance on a postoperative radiograph or CT image [4,9,10,12,13,15,21,36,37,42]. Disc space loss of 1 mm, 2 mm, 3 mm, and 4 mm was applied to evaluate cage subsidence in a specific cohort.…”

Utilization of Dual Expandable Cages in Lateral Lumbar Interbody Fusion Surgery

“…In 2020, Li et al completed a similar study with a one-year follow-up on 37 dual expandable cage spaces via the LLIF approach. This study was limited in that it offered no control group; however, it did note an association with mild postoperative osteopenia [ 18 ]. In 2023, Huo et al reported 48 patients receiving expandable cages with the expandable cage group notably having significantly higher rates of interbody fusion and reduced subsidence rates [ 19 ].…”

Expandable vs Static Interbody Devices for Lateral Lumbar Interbody Fusion

“…In studies by Frisch et al and Li et al, there was no statistically significant difference between static and expandable devices in increasing neuroforaminal height. 8,15 In the study by Frisch et al, the final intervertebral disc height after implant placement in the static group was about 4 mm more than that of the expandable group, suggesting that the static devices were possibly oversized. This alters the validity of the results because had the static devices been properly sized, the neuroforaminal area may have been significantly smaller in the static compared to the expandable group.…”

“…High-grade device subsidence in lateral static devices is a known potential complication and has been reported between 6% and 32%. 14,15 However, several studies have shown a significant decrease in the device subsidence rate when using lateral expandable devices. In a study by Frisch et al, there was 0% subsidence in the expandable group and 16% subsidence in the static group.…”

“…8 Li et al found similar results, with a 2-year subsidence rate of 6.7% in the expandable group and 16% in the static group. 15 Several possible explanations exist to explain these findings.…”