Purpose:

The purpose of this study was to identify sagittal spinopelvic parameters predictive of adjacent segment disease (ASD) on postoperative whole spine weight-bearing stereoradiography.

Materials and methods:

A total of 84 patients with previous spinal fusion surgery and documented radiological follow-up with early weight-bearing postoperative whole spine stereoradiography (EOS® Imaging System) were retrospectively included. A pathological group of 42 patients (9 men, 33 women; mean age, 63.1±11.5 [SD] years) who developed documented ASD (mean follow-up, 76.75 months; range: 31.5-158.5 months) was compared with a control group of 42 asymptomatic patients (7 men, 35 women; mean age, 60.9±11.8 [SD] years) (mean follow-up, 115 months; range: 60-197 months) based on sagittal balance evaluation and routinely used spino-pelvic parameters. Comparisons were made using uni- and multivariate analyses.

Results:

At univariate analysis, patients with ASD had an anteriorly displaced sagittal vertical axis (CAM plumb line) and an inadequate lumbar lordosis (LL) in reference to pelvic incidence (PI) compared to controls. They also had higher C7 slope and C2-C7 offset. At multivariate analysis, C2-C7 offset (OR=1.152; 95% CI: 1.056-1.256; P=0.001) and a lack of LL (OR=5.063; 95% CI: 1.139-22.498; P=0.033) were significantly associated with ASD.

Conclusion:

Anterior cervical imbalance, reflected by an increase in C2-C7 offset and insufficient restoration of LL are postoperative predictive factors of ASD on stereoradiography.