Does the Position of Cage Affect the Clinical Outcome of Lateral Interbody Fusion in Lumbar Spinal Stenosis?

STUDY DESIGN: A retrospective study. OBJECTIVE: This study aims to identify the ideal cage position in lateral lumbar interbody fusion (LLIF) and to investigate if the posterior instrumentation would affect the indirect decompression. METHODS: Patients underwent 2-stage surgeries: stage I was LLIF and stage II was percutaneous pedicle screws fixation after 1 week. Anterior disc height (ADH), posterior disc height (PDH), left and right foraminal height (FH), and segmental angle (SA) were measured on lateral computed tomography reconstructions. The cross-sectional area of the thecal sac (CSA) was determined by the outlined area of the thecal sac on a T2-weighted axial magnetic resonance imaging. The patients were subgroups according to the cage position: the anterior (cage located at the anterior 1/3 of disc space) and posterior groups (cage located at the posterior 2/3 of disc space). P values <.05 were considered significant. RESULTS: This study included 46 patients and 71 surgical levels. After stage I LLIF, significant increase in ADH, PDH, bilateral FH was found in both 2 subgroups, as well as the CSA (all Ps < .01). SA increased 2.84° ± 3.2° in the anterior group after stage I LLIF and increased 0.81° ± 3.1° in the posterior group (P = .013). After stage II surgery, SA was similar between the anterior and posterior groups (P = .20). CONCLUSION: The anteriorly placed cage may provide better improvement of anterior disc height and segmental angle after stand-alone LLIF surgery. After the second stage posterior instrumentation, the cage position would not affect the segmental angle or foraminal height.