Ultrasound imaging assessment of paraspinal and abdominal muscle quality in patients with chronic non-specific low back pain and its relationship to clinical outcomes

Objective: To evaluate the effects of abdominal and paraspinal muscle thickness and quality, assessed by ultrasonography, on quality of life (ODI), pain intensity (VAS), pain threshold (algometry), and kinesiophobia (TSK) in patients with non-specific chronic low back pain. Methods: This cross-sectional case-control study included 100 participants aged 18–75 years. Demographic and clinical characteristics were recorded, and assessments included pain intensity (VAS), pressure pain threshold (PPT), lumbar range of motion, functional disability (ODI), kinesiophobia (TSK), and muscle echogenicity (EI) measured by ultrasonography. Results: Patients exhibited restricted lumbar flexion and lateral flexion, lower bilateral PPT values, and higher ODI and TSK scores compared to controls (p<0.05–0.001). Muscle echogenicity was increased, while subcutaneous fat thickness, particularly at the left lumbar region, was higher than in controls (p<0.05). Quadratus lumborum echogenicity was significantly lower in patients (right raw p=0.028, right adjusted p=0.011, left adjusted p=0.028). Positive correlations were found between muscle echogenicity and abdominal subcutaneous fat with TSK, while negative correlations were observed with PPT (p<0.001). Conclusion: Decreased thickness and quality of abdominal and lumbar muscles are associated with functional limitations, lower pain thresholds, and kinesiophobia in patients with non-specific chronic low back pain. Future studies focusing on muscle quality and echogenicity may contribute to the development of more effective rehabilitation strategies for the management of chronic low back pain. Keywords: Abdominal muscle thickness, algometry, functional limitation, kinesiophobia, muscle echogenicity, non-specific low back pain, paraspinal muscle thickness, ultrasonography