Introduction.  Vacuum discs, the collection of gas within the intervertebral disc space, are believed to represent end-stage disc degeneration. However, the relationship between vacuum discs and pain severity is unknown. The goals of this study are to identify the prevalence of vacuum discs in patients with lumbar spinal deformities and determine whether there is an association with low back or leg pain severity.

Methods.  Patients evaluated at a single institution from 2013-2019 were included if they were aged >18 years, had a CT including the T12-S1 discs, and had a diagnosis of scoliosis, kyphosis, or flat back. Patients with prior thoracolumbar fusion or a history of spinal malignancy or inflammatory arthritis were excluded. Patient reported outcomes included numeric pain rating scales (NPRS) for back and leg pain, and the Oswestry Disability Index (ODI). CTs were evaluated for the presence and size of vacuum discs from T12-S1.

Univariate relationships between pain and the presence of vacuum discs (chi-squared/Fisher’s exact, Mann-Whitney U), number of levels with vacuum discs (Mann-Whitney U, linear regression), and maximum vacuum size (Fisher’s exact & Kruskal Wallis) were first assessed. Subsequently, multivariable GEEs were constructed to relate the presence of vacuum discs to back pain, leg pain and ODI. Analyses were performed with SAS v9.4 with a two-sided α=0.05.

Results.  The final cohort included 130 patients [62.3% female, median age=71.8 years (interquartile range (IQR))=65.5, 76.6]. 95.4% of patients had a vacuum in ≥1 disc, and 61.6% had a vacuum in ≥4 levels. The most common level was L3-L4 (72.9% of patients) (Table 1).

Vacuum discs were associated with older age, both when considered overall (p<0.006), or by individual level (p<0.037 for each). Older age was associated with a greater number of vacuum discs, with age increasing 3.5 (2.5, 4.5) years per additional vacuum (p<0.001). Older age was also associated with increased vacuum size (p<0.001). Patients with vacuum size >50% had a higher median age [72.9 (IQR: 66.8, 77.5) years] than those with a vacuum size <50% [65.9 (IQR: 62.4, 67.4), p<0.001], and those with no vacuum [43.9 (IQR: 21.0, 70.8), p<0.011].

Males were more likely to have more levels with vacuum discs [median(IQR) males=5 (3, 5), females=4 (3, 5); p=0.031]. Males also trended towards larger vacuum discs (p=0.089).

Considering all levels together, vacuum discs at L4-L5 were associated with higher NPRS back pain [+1.5 (0.2, 2.7), p=0.023] (Figure 1). Vacuum discs at L5-S1 were associated with greater leg pain [+2.1 (0.4, 3.9), p=0.016]. There was also a trend towards higher ODI (greater disability) with a vacuum at L5-S1 [+5.9, (-0.6, 12.4) p=0.071]. The number of vacuum levels and vacuum size were not associated with pain or ODI.

Discussion.  The presence, number, and severity of vacuum discs increased with age, and males had more vacuum discs than females. Vacuum discs were associated with increased pain and potentially increased disability at L4-L5 and L5-S1. These findings are pertinent to surgical planning in spinal deformity, as vacuum discs at these levels may be associated with more severe symptoms.