Relationship between facet joint osteoarthritis and multifidus fat infiltration in patients with lumbar spondylolisthesis

Facet joint osteoarthritis (FJOA) represents an early and prevalent indicator of lumbar degeneration, potentially impacting the adjacent multifidus muscle through mechanical and inflammatory mechanisms. Nevertheless, the association between FJOA and multifidus fat infiltration (FI) in the context of spondylolisthesis remains inadequately understood. This study retrospectively analyzed 243 patients diagnosed with either isthmic or degenerative lumbar spondylolisthesis (L2-S1) from two specialized spine centers. The severity of FJOA was assessed using Weishaupt's criteria. Parameters of the multifidus muscle, including FI, total muscle cross-sectional area (TMCSA), functional cross-sectional area (fCSA), and muscle height index (Muscle HI), were quantified utilizing ImageJ software. Spearman correlation and multivariate regression analyses were conducted to explore the relationships between FJOA and muscle parameters, adjusting for confounding variables such as age, sex, body mass index (BMI), and radiographic factors (including disc degeneration, stenosis, slippage level, and Meyerding classification etc.). The study found a significant increase in multifidus FI associated with advancing lumbar FJOA at the L2/3, L3/4, and L5/S1 levels (correlation coefficient r = 0.29-0.47, P < 0.001), which was accompanied by a decrease in fCSA (P < 0.05). FJOA emerged as an independent predictor of multifidus FI at L2/3 (β = 0.32-0.40, P < 0.001), L3/4 (β = 0.15-0.16, P < 0.05), and L5/S1 (β = 0.22-0.23, P < 0.001), whereas disc degeneration, central canal stenosis, and foraminal stenosis did not significantly contribute to multifidus FI. Additionally, age and female sex were consistently identified as positive predictors of FI (P ≤ 0.001). Although the association was less pronounced at the L4/5 level, a positive correlation was observed between the Meyerding grade and multifidus fat infiltration (P < 0.01). Lumbar FJOA is significantly and independently correlated with multifidus FI and a decrease in fCAS, a relationship that persists even in patients with spondylolisthesis. Conversely, BMI, disc degeneration, and central canal or foraminal stenosis did not exhibit a significant association with multifidus fat infiltration.