Expandable versus Static Cages in Transforaminal Lumbar Interbody Fusion: Radiographic—Comparison of Segmental and Lumbar Sagittal Angles

Presented at SMISS Annual Forum 2016
By Paul Park MD
With Timothy Yee , Jacob Joseph MD, Brandon Smith ,

Disclosures: Paul Park MD B; Biomet, Globus, Medtronic, Nuvasive. F; Globus Timothy Yee None, Jacob Joseph MD None, Brandon Smith None,


One criticism of transforaminal lumbar interbody fusion (TLIF) is the inability to increase segmental lordosis (SL). Expandable interbody cages are a relatively new innovation theorized to allow improvement in SL. 


To compare changes in SL and lumbar lordosis (LL) after TLIF with non-expandable versus expandable cages. 


We performed a retrospective cohort study of patients who were ≥18 years old and underwent single-level TLIF between 2011-2014. Patients were categorized by cage type (static versus expandable). Primary outcome of interest was change in SL and LL from preoperative values to those at 1 month and 1 year postoperatively. 


A total 89 patients were studied (48 non-expandable group, 41 expandable group). Groups had similar baseline characteristics. For SL, median (IQR) improvement was 3° for non-expandable and 2° for expandable (unadjusted, P=0.09; adjusted, P=0.68) at 1 month postoperatively, and 3° for non-expandable and 1° for expandable (unadjusted, P=0.41, adjusted, P=0.28) at 1 year postoperatively. For LL, median improvement was 1° for non-expandable and 2° for expandable (unadjusted, P=0.20; adjusted, P=0.21), and 2° for non-expandable and 5° for expandable (unadjusted, P=0.15; adjusted, P=0.51) at 1 year postoperatively. After excluding parallel expandable cages, there was still no difference in SL or LL improvement at 1 month or 1 year postoperatively between static and expandable cages (both unadjusted and adjusted, P>0.05). 


Patients undergoing single-level TLIF experienced similar improvements in SL and LL regardless of whether non-expandable or expandable cages were placed.