Fig. 4

Associations between multifidus gene expression and pre-operative morphological measures. Raw Ct-values were quantile normalized to the mean Ct-value; lower Ct-values representing higher gene expression and vice versa. Individuals with greater fat fraction demonstrated (a) Increased expression of adipogenic/metabolic gene PPARD (p = 0.018, r = -0.346) and (b) decreased expression of fibrogenic gene COL3A1 (p = 0.047, r = 0.386). Individuals with lower multifidus cross-sectional area demonstrated (c) decreased expression of myogenic gene mTOR (p = 0.045, r = 0.388). Multifidus muscle biopsies were collected intra-operatively (n = 59) and gene expression was assessed using qPCR. Morphological measures were evaluated using pre-operative T2-weighted MRI of the lumbar spine at the level of multifidus biopsy (n = 54). Univariate analyses were performed between each gene and MRI measure, and p-values were adjusted for multiple comparison using the Benjamini & Hochberg method with an adjusted p-value threshold of p < 0.05, and trends were defined as adjusted p-values < 0.1