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.