Patterns of intra-discal vacuum phenomenon in adult degenerative scoliosis.

Background: Degenerative scoliosis occurs with asymmetric disc and facet degeneration and vertebral wedging. Intra-discal vacuum phenomenon (IDVP) is associated with advanced disc and facet degeneration, but typically poorly visualised on radiograph or magnetic resonance imaging (MRI), and has not been reported in the context of degenerative scoliosis. This radiographic observational case-control study aims to further investigate degenerative scoliosis through evaluation and characterisation of IDVP. Methods: All scoliosis subjects were isolated from an over-60s population sample of 2020 digitalised computed tomography (CT) abdomen scans, yielding 136 subjects for analysis. One hundred and thirty-six age- and gender-matched non-scoliotic subjects with IDVP were chosen from the same cohort for comparison. The lumbar discs were analysed for severity, distribution and symmetry of IDVP. The lumbar spine was analysed for presence of scoliosis, calculation of pelvic incidence and presence of listhesis. Clinically significant back pain details were recorded and analysed. Results: Subjects with S-shape curves accounted for 80% (n=109) and C-shape curves in 20% (n=27). Ninety-four (86%) with an S-curve had multilevel contralateral IDVP compared to 15 (55%) of C-curves. IDVP position was distributed towards the upper lumbar spine and with increased asymmetry (concavity-based). Back pain was not significantly increased in scoliotic subjects (39% vs. 32%, P=0.30) and not correlated with location, severity, laterality or distribution of IDVP. Conclusions: CT analysis of degenerative scoliosis demonstrates predominantly multilevel contralateral asymmetric IDVP, with increased involvement of the upper lumbar spine and formation of S-shape curves, identifying a coronal compensatory correction in the presence of persistent degenerative mobility.