Introduction:. Circumferential arthrodesis of the spine may be achieved by posterior-only or anterior and posterior surgery. Posterior-based interbody fusions have significant limitations including unreliable improvement of segmental lordosis and variable rates of post-operative radiculopathy. Combined anterior and posterior surgery introduces significant cost and peri-operative morbidity. The purpose of this paper is to report the radiographic and clinical outcomes of posterior-based circumferential arthrodesis using a novel expandable interbody cage. Methods:. A prospective pilot clinical trial with one year follow-up of the only expandable cage approved by the FDA for interbody application. Clinical outcomes measured include ODI and VAS for back and leg. Radiographic outcomes include arthrodesis rates based upon CT scan. Statistical significance for change in health status was calculated using Student's t-test. Results:. 10 consecutive patients (11 levels) with lumbar degenerative pathology underwent circumferential arthrodesis with a transforaminal interbody approach. 10 of 11 levels were fused based upon CT scan. ODI scores improved a median of 37 to 20 at 6 months and 17 at one year (p = 0.0003). The VAS for back and leg pain likewise from 6 to 2 at 12 months (p = −.003). No patient reported an increase in leg pain from pre-op to post-op. One patient with a 2-level fusion had a non-union at 1 level requiring revision surgery. Conclusion:. Circumferential arthrodesis with a TLIF approach is an important technique for the management of lumbar degenerative pathology. The experience with a novel expandable TLIF cage demonstrates excellent results based upon clinical outcome and fusion rates. The expandable interbody cage allows in-situ height increase which is useful for optimizing clinical and radiographic outcomes in TLIF surgery