The evolving role of lateral lumbar interbody fusion in lumbar fusion: challenging the dominance of transforaminal interbody fusion

Introduction

Lumbar spinal fusion depends on robust interbody fusion of the anterior column. Historically, this has been achieved via a posterior approach, mandating an adequate direct neural decompression to place the interbody cages. Surgeons now have a range of approaches to the anterior column—anterior, anterolateral, lateral, posterolateral, and posterior—each with various advantages and disadvantages (1). Data from the Millennium Research Group showed that the transforaminal interbody fusion (TLIF) approach accounted for over 50% of the spinal fusion surgery market in the USA in 2019, with lateral lumbar interbody fusion (LLIF) accounting for 25%. Posterior lumbar interbody fusion (PLIF) and anterior lumbar interbody fusion (ALIF) accounted for only 15% and 10%, respectively. These figures are not dissimilar to Australian spine surgeon practices. From a growth perspective, it is projected that whilst TLIF will continue to grow at 3.6% per annum, PLIF and ALIF procedures will drop by 6.7% and 3.6% annually. However, LLIF will likely grow at 10.2%, nearly equalling TLIF by 2030 as the most common spinal interbody fusion approach (2).

Changes in fusion techniques and approaches

TLIF has recently come under scrutiny due to the push towards more complete discectomies and the placement of larger interbody cages into the anterior column (Figure 1), thereby affording more stability and improved segmental lordosis. From a biomechanical standpoint, placement of a narrow footprint interbody cage across the cancellous bony endplates creates pivoting forces and point loading, increasing rates of subsidence and lowering fusion rates, especially in the absence of bone morphogenetic protein [recombinant human bone morphogenetic protein-2 (rhBMP-2)] authorisation in Australia (3). Minimally invasive (MIS)-TLIF, while preserving the contralateral facet joint and posterior spino-ligamentous structures, limits posterior compression and thus lordosis. Bilateral approaches with posterior column osteotomies are often needed to maximise lordosis. Recent technologies such as endoscopic-assisted TLIFs and biplanar expandable cages aim to improve disc clearance, endplate preparation, and segmental lordosis (4). Nevertheless, TLIF remains the workhorse of lumbar interbody fusion (LIF) approaches and will continue to grow steadily. PLIF demands bilateral retraction of neural structures to access the disc space. While widely taught, it is physically demanding and increases patient morbidity through risks such as durotomy, motor deficits, and epidural fibrosis. Combined with extensive paraspinal muscle dissection, PLIF has fallen out of favour, declining by 6.7% per year. ALIF allows the placement of a wide-footprint cage with high fusion rates at the lumbosacral junction, making it attractive for deformity cases (5). Lateral ALIF innovations permit L5/S1 and higher levels to be accessed in a single position (6,7). However, the need for an access surgeon, and risks such as vascular injury and retrograde ejaculation, have hindered uptake. ALIF procedures are projected to halve by 2030.

Figure 1 Comparison between a TLIF (Nuvasive Inc., USA) and an ALIF cage (Redmond Ti/PEEK, A-Spine Asia, Taipei) demonstrates a significant difference: the ALIF cage provides substantially greater endplate coverage, distributing load across a larger surface area. In contrast, the TLIF cage offers minimal endplate coverage, resulting in a higher risk of subsidence. ALIF, anterior lumbar interbody fusion; TLIF, transforaminal interbody fusion.

Advances and adoption of LLIF

Initially, uptake of LLIF was low due to unfamiliarity with the retroperitoneal approach and risks to the lumbar plexus. Reports of transient sensory deficits (0–75%) and motor deficits (up to 36%) discouraged surgeons (8). Nevertheless, LLIF allows excellent disc clearance, endplate preparation, and placement of large cages spanning the apophyseal ring (Figure 2), achieving good clinical outcomes (9,10). Interfixated LLIF has also been effective for adjacent segment disease (11,12). The shift towards accessing the spine via an oblique lateral interbody fusion (OLIF) anterior to psoas (ATP) corridor purportedly decreased risks to the lumbar plexus (13). Although OLIF provided L5/S1 access, it introduced higher vascular risks and remained prone to nerve injuries (14). Neuromonitoring evolved from basic triggered electromyography (EMG) to a multimodal approach combining EMG and somatosensory evoked potentials (SSEPs), allowing real-time nerve monitoring (15-18). This shift has significantly reduced the risks of neuropraxia, especially at high-risk levels such as L4/5.

Figure 2 Comparative CT scans showing (A) TLIF (“Rise”, Globus Medical), (B) LLIF (“Hedron”, Globus Medical), and (C) ALIF (“Redmond”, A-Spine) cages, highlighting differences in endplate coverage, with LLIF providing with extension over the lateral osseodiscal rim. ALIF, anterior lumbar interbody fusion; CT, computed tomography; LLIF, lateral lumbar interbody fusion; TLIF, transforaminal interbody fusion.

Prone LLIF and the future of lumbar fusion

Performing LLIF in the prone position has led to further increases in its adoption (7,19). Prone positioning offers advantages such as posterior migration of neural structures, natural lordosis, and allows access to both anterior and posterior columns without repositioning. This enhances surgical efficiency and ergonomics. Prone LLIF is especially beneficial for spondylolisthesis and adjacent segment disease. Surgeons can first secure posterior instrumentation to reduce slips before safely placing lateral cages. Morphological changes in the psoas following slip reduction further enhance surgical safety. For revision and extension fusions, prone LLIF enables simultaneous posterior hardware release and lateral access (7). Evidence supports that lateral cages supplemented with integrated long screws can achieve robust fusion without disturbing prior posterior constructs (20). Furthermore, the prone lateral approach provides an effective method to revise failed posterior fusions, including removal of non-union cages (12,21).

Conclusions

LLIF, especially in the prone position, is reshaping the landscape of lumbar fusion surgery. It provides superior anterior access, a larger implant footprint, and improved lordosis, all within a single-position workflow. Enhanced neuromonitoring and growing surgical expertise have reduced neurological risks, supporting wider adoption. While TLIF remains the most utilised approach, the accelerating uptake and clinical advantages of LLIF indicate it is well positioned to rival TLIF as a primary interbody fusion strategy in the coming decade.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Journal of Spine Surgery. The article did not undergo external peer review.

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-2025-01/coif). R.J.M. serves as the Editor-in-Chief of Journal of Spine Surgery. G.M.M. serves as an unpaid editorial board member of Journal of Spine Surgery. Besides, R.J.M. reports royalties from Stryker Spine, Medacta Int. and AusBio Australia, consulting fees from Elliquence USA, stocks in Medtronic Int. and Johnson & Johnson Int. G.M.M. reports consulting fees from Globus Medical, Australian Biotechnology, payments from Globus Medical, Life HealthCare and Medtronic. Y.Y.W. reports consulting fees from ATec Spine, BrainLab and Matrix Medical Innovations, payments from ATec Spine and BrainLab, and he serves as the board member of Australian Pituitary Foundation and is the shareholder of ATec Spine. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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