Spine 2026;51(19):1381-1389
Access to L4-L5 during single-position lumbar fusion is shaped by the relationship between the disc, iliac crest, psoas, lumbar plexus and major vessels. Huynh and colleagues compare anterior lumbar interbody fusion performed in lateral decubitus with transpsoas lateral interbody fusion, examining whether the anterior route offers a useful alternative without repositioning the patient. Their multicenter findings associate lateral-position ALIF with fewer postoperative complications and greater segmental lordosis, while highlighting the importance of anatomical selection. The study expands the discussion of available corridors, but its observational design does not establish one approach as uniformly safer or more effective.
Objective
To compare complications, reoperations, procedural efficiency and sagittal alignment after L4-L5 lateral-decubitus ALIF (L-ALIF) and transpsoas LLIF during one- or two-level lateral single-position surgery.
Methods
The authors retrospectively reviewed prospectively and consecutively enrolled patients from seven surgeons across Australia, Brazil and the United States. The reported cohort comprised 511 patients: 72 undergoing L4-L5 L-ALIF and 439 undergoing L4-L5 LLIF. Mean ages were approximately 66 and 65 years, respectively. Indications included degenerative spondylolisthesis, foraminal stenosis and postlaminectomy instability or syndrome. Previous lumbar fusion, additional TLIF/PLIF, repositioning and staged surgery were excluded.
Approach selection depended on surgeon preference and anatomy. Three surgeons contributed L-ALIF cases, whereas all seven contributed LLIF cases. Additional fusion could involve L3-L4 using LLIF or L5-S1 using L-ALIF. Both groups received posterior pedicle instrumentation without changing the lateral position.
Follow-up was at least 90 days, with radiographic assessment at 90 days. Propensity matching for age, sex, BMI, diabetes, smoking and number of fused levels generated groups of 72 patients each. Complications were classified using the Clavien-Dindo system; neurological symptoms persisting beyond six weeks were classified as major complications.
Main results
In the matched groups, postoperative complications occurred in 4.2% after L-ALIF versus 19.4% after LLIF (p = 0.004); major complications were 2.8% versus 11.1% (p = 0.049). Ninety-day reoperations did not differ significantly (2.8% versus 8.3%; p = 0.146). Operating time, blood loss and length of stay were also similar after matching. L4-L5 segmental lordosis increased by 6.6° versus 1.8° (p = 0.003). Postoperative L4-S1 lordosis was greater with L-ALIF, but its change from baseline did not differ significantly. These are matched-cohort results, distinct from the larger unmatched comparison.
Interpretation
L-ALIF provides an alternative when the transpsoas corridor is constrained, but replaces plexus-related exposure concerns with vascular mobilization considerations. The study used an access surgeon for anterior exposure and EMG-guided mapping for LLIF; unsafe transpsoas docking prompted abandonment of that approach. These safeguards are part of the reported treatment setting, not optional details that the comparison can separate from outcomes. Importantly, the three vascular injuries in the overall LLIF-labeled group occurred during accompanying L5-S1 ALIF exposure, not the L4-L5 transpsoas approach. They cannot be attributed to LLIF itself.
Limitations
Treatment was not randomized, and the anatomical reasons for choosing each corridor were not adequately captured. Propensity matching balances measured variables but cannot remove this confounding by indication or the influence of surgeon experience. Only three surgeons supplied L-ALIF cases, compared with seven for LLIF.
Two-level operations combine different approaches, limiting attribution of complications to the L4-L5 corridor. Short follow-up and the absence of patient-reported functional outcomes prevent conclusions about durable symptom relief, fusion success or long-term revision risk. Absence of vascular injury in the 72 L4-L5 L-ALIF patients does not establish absence of risk. Multiple statistical comparisons also increase the possibility of false-positive findings, particularly for borderline results.
The publication contains minor reporting discrepancies, including 438 versus 439 LLIF patients in different locations and a segmental lordosis change of 6.8° in the abstract versus 6.6° in Table 5. The figures summarized here follow the main results and matched tables. Several authors disclosed industry relationships relevant to spinal instrumentation.
Clinical takeaway
For lateral single-position L4-L5 fusion, assess both the anterior vascular corridor and the transpsoas neural corridor before choosing the approach. L-ALIF is a reasonable option in experienced hands and may improve segmental lordosis while avoiding psoas-related symptoms. This study supports individualized planning, not a blanket claim that anterior access is safer or that greater radiographic correction guarantees better clinical recovery.