Outcomes of stand-alone anterior lumbar interbody fusion of L5-S1 using a novel implant with anterior plate fixation

Background context: Compared with other approaches, anterior lumbar interbody fusion (ALIF) is believed to be more effective at restoring segmental lordosis and reducing risks of adjacent-segment disease. It remains controversial, however, whether ALIF improves global lumbar lordosis or influences pelvic parameters, possibly because of the heterogeneity of implants and levels studied.

Purpose: To report clinical outcomes of stand-alone ALIF with anterior plate fixation for L5-S1 and to determine the effect on global lumbar lordosis and pelvic parameters.

Study design: This is a retrospective case series.

Patient sample: Patients that underwent isolated mini-ALIF with anterior plate fixation for L5-S1.

Outcome measures: Oswestry Disability Index (ODI), Short Form 12, lower back and legs pain on Visual Analog Scale, as well as spino-pelvic parameters.

Methods: The authors reviewed the records of all patients that underwent retroperitoneal mini-ALIF for single-level L5-S1 fusion between August 2012 and December 2016. A total of 129 patients were included, but 9 patients had incomplete preoperative radiographic data, and one patient had schizophrenia and was unable to respond to outcome questionnaires, leaving 119 patients eligible for outcome assessment. At a minimum follow-up of 1 year, seven patients refused to participate in the study or could not be reached, which left a final cohort of 112 patients.

Results: Nine patients were reoperated without implant removal (four pseudarthrosis, two hematomas, one sepsis, one L4-L5 disc hernia, and one L4-L5 disc degeneration). At a mean of 20±9 months, all scores improved significantly from baseline values, with net improvement in ODI of 23.3±19.9. Multivariable analyses confirmed better postoperative ODI in patients that received 18° cages (β=-9.0, p=.017), but revealed no significant trends for net improvement in ODI. Comparison of preoperative and last follow-up radiographs revealed that global lumbar lordosis increased by 4.2±7.1° (p<.001), L5-S1 segmental lordosis increased by 11.8±6.7° (p<.001), and L4-L5 segmental lordosis decreased by 1.9±3.3° (p<.001). All pelvic parameters changed: pelvic incidence increased by 0.6±2.7° (p=.003), pelvic tilt decreased by 2.5±4.1° (p<.001) and sacral slope increased by 3.3±4.7° (p<.001).

Conclusions: Stand-alone mini-ALIF with anterior plate fixation for L5-S1 can change pelvic parameters while improving global and segmental lumbar lordosis. The procedure resulted in a fusion rate of 96% and comparable improvements in ODI to other studies.