Expandable vs Static Cages in Transforaminal Lumbar Interbody Fusion

Neurosurgery 81:69–74, 2017

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.

OBJECTIVE: To compare changes in SL and lumbar lordosis (LL) after TLIF with nonexpandable vs expandable cages. METHODS: We performed a retrospective cohort study of patients who were ≥18 years old and underwent single-level TLIF between 2011 and 2014. Patients were categorized by cage type (static vs expandable). Primary outcome of interestwas change in SL and LL from preoperative values to those at 1 month and 1 year postoperatively.

RESULTS: A total of 89 patients were studied (48 nonexpandable group, 41 expandable group). Groups had similar baseline characteristics. For SL, median (interquartile range) improvement was 3◦ for nonexpandable and 2◦ for expandable (unadjusted, P = .09; adjusted, P = .68) at 1 month postoperatively, and 3◦ for nonexpandable and 1◦ for expandable (unadjusted, P=.41; adjusted, P=.28) at 1 year postoperatively. For LL, median improvement was 1◦ for nonexpandable and 2◦ for expandable (unadjusted, P = .20; adjusted, P = .21), and 2◦ for nonexpandable and 5◦ for expandable (unadjusted, P = .15; adjusted, P=.51) at 1 year postoperatively. After excluding parallel expandable cages, there was still no difference in SL or LL improvement at 1month or 1 year postoperatively between static and expandable cages (both unadjusted and adjusted, P > .05).

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