Crosstalk between osteoporosis and fat-infiltrated psoas at the upper lumbar levels

Abstract Purpose Osteoporosis is a chronic metabolic bone disease characterized by reduced bone mass, microarchitectural deterioration, and an increased risk of fractures. Alongside osteoporosis, sarcopenia—the age-related decline in skeletal muscle mass and strength—is commonly observed in the elderly, especially among women. Prior studies have linked vertebral compression fractures with impaired spinal mobility, muscle atrophy, fatty degeneration of paraspinal muscles, and balance deficits. However, the relationship between osteoporosis in the absence of vertebral fractures and the condition of paraspinal muscles remains unclear. This study aimed to investigate whether osteoporosis is associated with fatty infiltration of the paraspinal muscles in patients experiencing chronic low back pain. Methods Age- and sex-matched patients with and without osteoporosis, all presenting with chronic low back pain, were retrospectively assessed using lumbar magnetic resonance imaging. Evaluations included the degree of intervertebral disc degeneration (IVDD), Modic changes, and fat infiltration in the multifidus, erector spinae, and psoas muscles at all lumbar levels. Results No significant differences were found between osteoporotic and non-osteoporotic groups regarding the severity of IVDD or the presence of Modic changes. However, patients with lumbar spine osteoporosis exhibited significantly greater fatty infiltration in the psoas muscle at the L1–L2 (odds ratio [OR] = 6.191; p = 0.015), L2–L3 (OR = 3.205; p = 0.028), and L5–S1 (OR = 1.564; p = 0.040) levels. Additionally, those with femoral neck osteoporosis demonstrated greater fat infiltration in the psoas muscle specifically at L1–L2 (OR = 4.487; p = 0.043). Conclusion Osteoporosis appears to be associated with increased fatty infiltration of the psoas muscle, particularly at the upper lumbar levels. Therefore, detailed evaluation of the psoas muscle should be considered in osteoporotic patients. Conversely, the presence of fat-infiltrated psoas muscles at upper lumbar levels may warrant clinical suspicion for underlying osteoporosis. Management strategies for osteoporosis should incorporate interventions aimed at enhancing the quality and strength of the psoas muscle to help prevent vertebral compression fractures.