Incidence and Risk Factors of Anterior Longitudinal Ligament Rupture After Posterior Corrective Surgery Using Lateral Lumbar Interbody Fusion for Adult Spinal Deformity

Abstract

Study design: A retrospective single-center study.

Objective: The objective of this study was to assess the incidence of anterior longitudinal ligament rupture (ALLR) and to identify the risk factors for ALLR in patients with adult spinal deformity (ASD).

Summary of background data: Lateral lumbar interbody fusion (LIF) has been widely used for ASD surgery. However, ALLR has been occasionally identified after posterior spinal correction surgery.

Materials and methods: The study included 43 consecutive patients (8 male and 35 female patients) who underwent posterior corrective surgery involving LIF (128 levels) for ASD between 2014 and 2018. The mean age was 72±7 years (range: 62-81 y), and the minimum follow-up period was 1 year [mean: 34±15 mo (range: 12-58 mo)]. Posterior correction and fusion surgery using the cantilever technique was performed following LIF. Oblique LIF was performed in 27 patients, and extreme lateral interbody fusion (XLIF) was performed in 16 patients. The mean number of spinal fused levels was 8.9±1.8 levels (range: 8-15), and the mean number of LIF levels was 3±0.6 levels (range: 2-4). ALLR was considered if a LIF cage showed no contact with the vertebral endplates. The radiographic parameters were thoracic kyphosis, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt, and sagittal vertical axis.

Results: ALLR occurred in 10 patients (22%) and at 11 levels (8.6%). XLIF and preexisting osteoporotic vertebral fracture were identified as independent risk factors for ALLR. The change in LL was ∼10 degrees greater in the ALLR group than in the non-ALLR group (P=0.017), and overcorrection was observed in the ALLR group (PI-LL: -7.9±7 degrees). The change in the segmental lordotic angle at the ALLR level was much larger than after LIF and correction surgery. ALLR-related reoperation was performed in 2 cases (decompression surgery owing to posterior impingement and rod breakage).

Conclusions: ALLR occurred in 10 patients (22%). XLIF and preexisting osteoporotic vertebral fracture were independent risk factors for ALLR. Overcorrection was observed in patients with ALLR.