LLIF / XLIF / DLIF

These are all names for lateral lumbar interbody fusion: reaching the disc through a small incision in the side of the body, passing through or around the psoas muscle in a retroperitoneal corridor, and placing a large cage across the disc space. XLIF and DLIF describe particular versions of the transpsoas lateral approach; the closely related oblique approach, OLIF, reaches the disc from a slightly more forward angle. What they share is the corridor from the side, which avoids opening the back muscles and avoids the vessels at the front, and which lets me seat a broad cage on the strong bony rim of the vertebra. It is usually combined with posterior screws and rods to complete the fixation.

The lateral approach lets me place a cage with a very large footprint, spanning the disc from side to side and resting on the dense outer ring of bone. That does three things I value. It restores disc height and segmental lordosis, helping me rebuild the shape of the spine. It corrects side-to-side, coronal, tilt — which makes it especially useful in adult degenerative scoliosis and in restoring both coronal and sagittal balance. And it achieves indirect decompression: by pulling the disc space back up to height, it tensions the ligaments and reopens the canal and foramina, taking pressure off the nerves without my needing to operate directly on them. All of this is delivered through a minimally invasive corridor that spares the back muscles. For a deformity-focused, alignment-first practice like mine, the lateral approach is a valuable way to correct alignment across one or several levels with relatively little disruption.

The distinctive consideration with the transpsoas lateral approach is that the corridor passes through the psoas muscle, close to the nerves of the lumbar plexus that supply the front of the thigh. This is worked around carefully, with nerve monitoring, but it can cause temporary symptoms in the thigh — pain, numbness or hip-flexor weakness — in a proportion of people. These are usually transient and settle over a few months, with only a minority having any persistent symptom. The oblique approach, OLIF, is designed to pass in front of the psoas and reduce that plexus risk, at the cost of working nearer the vessels. Which corridor suits a given person depends on the level and the anatomy, and is part of the planning.

The evidence supports lateral interbody fusion as an effective, minimally invasive way to restore alignment and decompress indirectly. Studies show reliable restoration of disc and foraminal height with indirect neural decompression via ligament tensioning, and meaningful correction of coronal and sagittal alignment, which is why it features prominently in the staged correction of adult degenerative scoliosis. Fusion rates are generally high, better with posterior instrumentation than with a stand-alone cage, and one-year data show significant improvement in back and leg pain and disability. The best-documented risk is from the transpsoas corridor — anterior thigh symptoms and hip-flexor weakness in a reported range that is usually transient — and subsidence of the cage into the bone is recognised and planned against. Comparative studies find the oblique approach broadly similar in radiographic and fusion outcomes with a somewhat different risk profile.

Because the muscles of the back are spared, recovery from the lateral part of the operation is often comfortable, and people are usually up and moving quickly. Some temporary thigh discomfort or a feeling of weakness in the hip flexor on the operated side is common in the early weeks and typically settles. Where posterior screws are added, recovery follows that of a lumbar fusion — home within a few days, and a graded return to activity over the following weeks and months while the fusion becomes solid. Many people notice better posture once disc height and alignment have been restored. The spine is followed up over the longer term.

• —Phan K, et al. Lateral transpsoas lumbar interbody fusion: outcomes and deformity correction. (PMID 24703453)
• —Rodgers WB. Postoperative complications within the first year after extreme lateral interbody fusion. (PMID 27007791)
• —The effect of retroperitoneal transpsoas lateral interbody fusion on segmental and regional lumbar lordosis. (PMID 22919332)
• —Predictors of indirect neural decompression in transpsoas lateral lumbar interbody fusion. (PMID 33930860)
• —Cahill KS, et al. Systematic review of thigh symptoms after lateral transpsoas interbody fusion. (PMID 26767154)
• —Macki M, et al. Subsidence rates after lateral lumbar interbody fusion: a systematic review. (PMID 30476670)
• —Fusion rate for stand-alone lateral lumbar interbody fusion: a systematic review. (PMID 32535072)
• —Extreme lateral interbody fusion for the treatment of adult degenerative scoliosis. (PMID 23906522)
• —Contribution of lateral interbody fusion in staged correction of adult degenerative scoliosis. (PMID 30396244)
• —Management of sagittal balance in adult spinal deformity with minimally invasive anterolateral interbody fusion. (PMID 24628129)
• —Clinical results and complications associated with the oblique lumbar interbody fusion technique. (PMID 33553309)
• —Comparison of outcomes and spino-pelvic sagittal balance in degenerative spondylolisthesis: OLIF versus TLIF. (PMID 33545942)