Clinical and Radiographic Analysis of Expandable versus Static Lateral Lumbar Interbody Fusion Devices with 1-Year Follow-up

Presented at SMISS Annual Forum 2016
By Joseph OBrien
With Daina Brooks BS, Ingrid Luna , Gita Joshua MA, Richard Frisch MD,

Disclosures: Joseph OBrien A; NSF (National Science Foundation); NuVasive, Inc.; RTI Surgical. B; Globus Medical, Inc.; RTI Surgical; DePuy Synthes; 4WEB Medical. D; RTI Surgical; Alphatec Spine; 4WEB Medical. F; Globus Medical Daina Brooks BS E; Globus Medical, Inc., Ingrid Luna E; Globus Medical, Inc., Gita Joshua MA E; Globus Medical, Inc., Richard Frisch MD B; Globus Medical. F; Globus Medical,


Use of static and expandable interbody cages for lateral lumbar interbody fusion (LLIF) is now widely accepted and offers favorable clinical results. However, optimal fit is difficult to achieve with static cages, and complications such as implant migration and/or subsidence may occur. Expandable cages allow in situ expansion to optimize fit and provide anterior support. 


To compare clinical and radiographic outcomes in patients following LLIF with a static versus an expandable interbody cage and to report device-related complications observed in either group.


This analysis focused on a review of 20 patients (25 levels) who underwent LLIF using a static cage and 20 patients (24 levels) using an expandable cage; all procedures were combined with supplemental transpedicular posterior stabilization. Investigators used clinical and radiographic records to assess clinical outcomes, fusion rates, and device-related complications. 


Mean patient age was 61.0 ± 11.2 years, and 65% were female. Seventy-eight percent of patients underwent one-level surgery, and 22% a two-level procedure. Surgery was most common at L4-L5 for one-level procedures, and at L3-L5 for two-level procedures. Average blood loss and hospital stay were similar in static and expandable cage groups for one-level and two-level procedures, with no significant differences reported (P < .05). Mean visual analog scale back pain scores and Oswestry Disability Index scores decreased significantly from preoperative to all postoperative time intervals for both static and expandable cage groups (6-, 12-, 26-, and 52-week assessments) (P < .05). Mean intervertebral disc height (±SD) increased significantly from 9.6 ± 2.2 mm preoperatively to 15.9 ± 2.5 mm at 12 months for static cages, and from 7.6 ± 2.2 mm preoperatively to 13.2 ± 1.9 mm at 12 months for expandable cages (P < .01). Neuroforaminal height also increased significantly from preoperative to 12-month assessment (19.3 ± 4.5 mm to 23.8 ± 3.2 mm for static cages, and 18.1 ± 2.9 mm to 21.4 ± 3.2 mm for expandable cages, P < .01). Postoperative radiographs showed no evidence of cage migration, subsidence, or collapse in either group. Fusion was observed at 96% (23/24) and 89% (17/19) of levels in static and expandable cage groups, respectively. 


Use of static and expandable cages for LLIF led to significant improvement in clinical and radiographic outcomes, and improvements were similar between groups. No significant complications were reported in static or expandable groups, and both spacers maintained height over time.