A Change in Lumbar Sagittal Alignment After Single-level Anterior Lumbar Interbody Fusion for Lumbar Degenerative Spondylolisthesis With Normal Sagittal Balance.

STUDY DESIGN: Retrospective analysis.

OBJECTIVE: The object is to assess the correlation between whole lumbar lordosis (LL) and the segmental angle (SA) after single-level anterior lumbar interbody fusion for degenerative lumbar spondylolisthesis.

SUMMARY OF BACKGROUND DATA: The restoration of the SA at lower lumbar spine is meaningful, considering it contributes approximately 60% of LL, and revision surgery due to flat back or adjacent segment pathology was necessary decades after the initial surgery. However, little is known about the change of whole lumbar curvature after single-level lower lumbar fusion surgery, especially for balanced spine.

MATERIALS AND METHODS: We included 41 consecutive patients (M:F=9:32; mean age, 59.8±9.3 y) with a single-level anterior lumbar interbody fusion surgery for low-grade degenerative spinal spondylolisthesis, with C7 plumb line of <5 cm and ≥2-year follow-up period. The operated levels were L4-L5 in 34 patients and L5-S1 in 7 patients. Whole LL, SA, pelvic tilt, and sacral slope were compared.

RESULTS: According to the Macnab criteria, a favorable outcome (excellent, 21; good, 15) was achieved in 36/41 (88%; excellent, 21; good, 15) patients. LL and SA were significantly changed from -50.8±9.9 to -54.6±11.1 degrees and -15.6±6.1 to -18.7±5.1 degrees (P<0.01), and a positive correlation (r=0.43, P=0.01) was observed between LL and SA at postoperative month 24. The changes to the pelvic tilt and sacral slope were not significant.

CONCLUSIONS: Whole lumbar sagittal alignment was influenced by single SA. Therefore, obtaining adequate segmental lordosis is desirable considering the effect on the whole spine for a long time.