Segmental analysis of radiological outcomes after one and two-level anterior cervical discectomy and fusion

Introduction: The development of cervical degenerative disc disease can lead to the loss of cervical lordosis, which negatively impacts global sagittal alignment and leads to chronic neck pain. Anterior cervical discectomy and fusion (ACDF) is a common procedure to treat cervical degenerative diseases. Previous study in the thoracolumbar spine found that increased index lordosis (vertebral level at which implant was placed) led to a reciprocal adjacent-level segmental change. However, there are no similar studies in the cervical region. We aim to determine the impact of adding lordosis or kyphosis at the index level on adjacent segmental alignment of the cervical spine.

Methods: We retrospectively reviewed one- and two-level ACDFs at a single tertiary care center between July 2019 and July 2022 with a minimum 6-month radiographic follow-up. Radiographic measurements of segmental and global alignment were collected by two reviewers using upright lateral radiographs in Nilread (diagnostic viewer). Patients were stratified into two cohorts: increased lordosis and no change in lordosis at the index level. Demographic variables, mean and standard deviations of measurements, as well as significance of variables compared between and across groups were statistically analyzed.

Results: A total of 64 patients with 107 interbody levels were identified. Increasing index lordosis led to increased global lordosis in C1-C7 (Δ= 4.83, p = 0.0354) and C2-C7 (Δ= 3.14, p = 0.041). However, C2-C7 SVA decreased (Δ= -0.19) when kyphosis was added, although not significant (p = 0.502). Increased index lordosis also led to increased index ADH (p < 0.01), index PDH (p = 0.095), and T1 slope (Δ= 3.85, p = 0.0058), indicating that more lordosis may be needed to keep the neck vertical. However, increased index lordosis had no significant change on adjacent segmental lordosis (Δ=0.33, p = 0.672), adjacent ADH (Δ= 0.082, p = 0.519), and adjacent PDH (Δ= -0.077, p = 0.461).

Conclusion : Increasing lordosis at the index level leads to an increased global alignment and T1 slope with no impact on adjacent segmental alignment. This study provides insight into the impact of cervical lordosis on adjacent segmental alignment, and the segmental differences between cervical and thoracolumbar spine.