Aim: The purpose of this study was to assess morphological changes in the paravertebral muscles in patients with ankylosing spondylitis.
Materials and methods: Fifty-one patients diagnosed with ankylosing spondylitis and a 50 member control group were included in the study. The surface area of the multifidus and erector spinae muscles was measured at four levels between L1 and L5, and fatty degeneration in these muscles was scored. Lumbosacral and lumbar lordotic angles were determined for the patient and control groups.
Results: Loss of muscle cross-sectional area compatible with atrophy was present at all four levels in the paraspinal muscles in patients with ankylosing spondylitis. A negative correlation was observed between paravertebral muscle area and duration of disease at three levels, but not at L1-2. Although muscle area decreased with the duration of disease at the L1-2 level, this was not statistically significant (r= -0.195, p = 0.171). Comparison of intramuscular fatty degeneration between the groups revealed increased intramuscular fat at all levels in patients with ankylosing spondylitis, with the exception of L3-4, and a positive correlation between fatty degeneration and duration of disease was determined at all levels.
Conclusion: Chronic inflammation, cytokine-mediated fibrosis, immobilization, and postural changes in ankylosing spondylitis contribute to fatty degeneration and atrophy in the paravertebral muscles.
Keywords: Ankylosing spondylitis; Fatty degeneration; Paravertebral muscle.