ALIF offers superior outcomes to TLIF for the treatment of L5-S1 isthmic spondylolisthesis

Andrew Simpson

Anterior lumbar interbody fusion (ALIF) generates greater segmental lordosis, regional lordosis, and restoration of disc height compared to transforaminal lumbar interbody fusion (TLIF) when treating isthmic spondylolisthesis. This is according to new research published in the journal Spine by Andrew Simpson (Brigham and Women’s Hospital, Boston, USA) et al.

In addition, the researchers found that ALIF patients demonstrate significant improvements across more patient-reported outcome measures (PROMs) domains relative to TLIF patients.

The purpose of this retrospective cohort study was to compare segmental and regional radiographic parameters between ALIF and TLIF for treatment of L5-S1 isthmic spondylolisthesis, and to assess for changes in these parameters over time. The study also sought to compare clinical outcomes via PROMs between techniques and within groups over time.

The researchers reviewed preoperative and postoperative radiographs in addition to Patient-Reported Outcomes Measurement Information System (PROMIS) elements for patients who received L5-S1 interbody fusions for isthmic spondylolisthesis in the Mass General Brigham health system between 2016 and 2020.

Intraclass correlation testing was used for reliability assessments; Mann–Whitney U tests and Sign tests were employed for intercohort and intracohort comparative analyses, respectively.

The data show that ALIFs generated greater segmental and L4-S1 lordosis than TLIF, both at first postoperative visit (mean 26 days [standard error (SE) = 4]; 11.3° vs. 1.3°, p<0.001; 6.2° vs. 0.3°, p=0.005) and at final follow-up (mean 410 days [SE = 45]; 9.6° vs. 0.2°, p<0.001; 7.9° vs. 2.1°, p=0.005).

ALIF also demonstrated greater increase in disc height than TLIF at first (9.6mm vs. 5.5mm, p<0.001) and final follow-up (8.7mm vs. 3.6mm, p<0.001). Disc height was maintained in the ALIF group but decreased over time in the TLIF cohort (ALIF, 9.6mm vs. 8.7mm, p=0.1; TLIF, 5.5 vs. 3.6mm, p<0.001). Both groups demonstrated improvements in pain intensity and pain interference scores.

Speaking to Spinal News International, Simpson said: “Isthmic spondylolisthesis is one of the most common diagnoses seen by spine surgeons requiring operative treatment. Several forces have changed over the last few decades in spine surgery that effect the way in which we think about this problem. First, we have gained an increased appreciation for the role of global sagittal balance and its correlation with functional outcomes. Additionally, surgical techniques have advanced and allow surgeons to place interbody cages from a multitude of approaches with relatively low risk profiles.

“Isthmic spondylolistheses most commonly occur at the L5-S1 level, which is the lowest motion segment, wherein changes to segmental alignment can have the greatest effect on global alignment. Isthmic spondylolisthesis is also somewhat unique anatomically because there is a complete detachment of the vertebral body from the posterior elements, which allows for greater potential repositioning of the vertebrae during interbody procedures.

“Given these factors, we felt it was important to revisit the treatment of isthmic spondylolisthesis and perform a head-to-head comparison of clinical and radiographic outcomes for the two most commonly utilised modern surgical approaches, ALIF and TLIF. We looked at procedures performed across the Mass General Brigham enterprise.

“We found that ALIF, not surprisingly, generated significantly better radiographic parameters at the operative level, that were sustained at longer term follow up, with less subsidence compared to the TLIF group.  Further, we also demonstrated that regional lumbar radiographic alignment was better in the ALIF group, meaning that the benefit of the procedure goes beyond the operative segment, and may contribute to improved global alignment relative to TLIF.

“In terms of clinical outcomes, both procedures demonstrated significant improvements in reducing pain scores, but ALIF patients also showed significant improvements in physical function scores, that were not seen in TLIF patients. This seems to be in continuity with previous work demonstrating the importance of global alignment on functional outcomes.

“In brief, this work demonstrated that ALIF was superior to TLIF for the treatment of L5-S1 isthmic spondylolisthesis, both in terms of clinical and radiographic outcomes. While there are certainly other patient and procedural factors that might affect approach selection, including surgeon comfort with techniques and involvement of talented access surgeons, ALIF seems to offer a superior approach platform for this common spinal pathology.

“I would like to thank several Harvard orthopaedic residents and future spine surgeons that performed the real heavy lifting on this study, Harry Lightsey, Brendan Striano, Alexander Crawford, and Grace Xiong, all of whom are immensely talented and are undoubtedly destined to advance our field.”


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