Degenerative spondylolisthesis is a common cause of low back pain and radiculopathy, predominantly affecting the aging population. Surgical intervention is indicated when conservative management fails. Among the most frequently used interbody fusion techniques are transforaminal lumbar interbody fusion (TLIF), TLIF with expandable cage, and oblique lumbar interbody fusion (OLIF). Each method offers distinct advantages and limitations regarding biomechanical stability, indirect decompression, restoration of sagittal balance, and patient outcomes.

TLIF has long been the gold standard for lumbar fusion due to its posterior access and high fusion rates. However, it may be associated with significant muscle disruption and less optimal restoration of disc height and alignment. OLIF, on the other hand, offers a minimally invasive lateral approach, avoiding the psoas muscle and the spinal canal, with the potential for better lordosis correction and disc height restoration, while minimizing neural injury risk.

Recent innovations include the use of expandable cages in TLIF, designed to allow in situ height expansion, potentially enhancing disc height and lordosis restoration without increasing retraction-related complications. However, despite widespread clinical application, there is limited high-quality evidence directly comparing these three surgical techniques using both clinical and radiological metrics.

Multiple studies have shown superior restoration of disc and foraminal height and lower complication rates with OLIF compared to traditional TLIF[i]. Others suggest that expandable cages may provide biomechanical advantages in TLIF without substantially altering complication profiles[ii] [iii]. However, comparisons across these modalities remain scarce and often limited by sample size, heterogeneity in pathology, or lack of long-term radiological follow-up[iv] [v].

Thus, this study aims to comprehensively evaluate and compare the clinical and radiological outcomes of OLIF, TLIF, and TLIF with expandable cage in a uniform pathology setting — degenerative spondylolisthesis — through a prospective study.