Expandable Versus Static Cages in Minimally Invasive Lumbar Interbody Fusion: A Systematic Review and Meta-Analysis

Expandable cages for interbody fusion allow for in situ expansion optimizing fit while mitigating endplate damage. Studies comparing outcomes after using expandable or static cages have been conflicting.

This was a meta-analysis A systematic search was performed in accordance with the Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) guidelines identifying studies reporting outcomes among patients who underwent minimally invasive lumbar interbody fusion (MIS-LIF).

Fourteen articles with 1129 patients met inclusion criteria. Compared with MIS-LIFs performed with static cages, those with expandable cages had a significantly lower incidence of graft subsidence (expandable: incidence 0.03, I² 22.50%; static: incidence 0.27, I² 51.03%, P interaction <0.001), length of hospital stay (expandable: mean difference [MD] 3.55 days, I² 97%; static: MD 7.1 days, I² 97%, P interaction <0.01), and a greater increase in disc height (expandable: MD -4.41 mm, I² 99.56%; static: MD -0.79 mm, I² 99.17%, P interaction = 0.02). There was no statistically significant difference among Oswestry Disability Index (expandable: MD -22.75, I² 98.17%; static: MD -17.11, I² 95.26%, P interaction = 0.15), fusion rate (expandable: incidence 0.94, I² 0%; static incidence 0.92, I² 0%, P interaction = 0.44), overall change in lumbar lordosis (expandable: MD 3.48 degrees, I² 59.29%; static: MD 3.67 degrees, I² 0.00%, P interaction 0.88), blood loss (expandable: MD 228.9 mL, I² 100%; static: MD 261.1 mL, I² 94%, P interaction = 0.69) and operative time (expandable: MD 184 minutes, I² 95.32%; static: MD 150.4 minutes, I² 91%, P interaction = 0.56).

Expandable interbody cages in MIS-LIF were associated with a decrease in subsidence rate, operative time and greater in increase in disc height.