Abstract
Background/Objectives: Musculoskeletal aging can clinically hardly be distinguished from degenerative disease, especially if symptoms are nonspecific, like lower back pain and reduced physical resilience. However, age-related changes are considered to be physiological until they cause osteoporotic fractures or sarcopenia-related restrictions. This radio-anatomic investigation examines whether findings in lumbar magnetic resonance imaging (MRI) mirror age- and sex-related musculoskeletal differences that help to identify the onset of sarcopenia. Methods: Lumbar MRI investigations from 101 women and 101 men were retrospectively evaluated for vertebral and muscular cross-sectional diameter sizes and T2-signal intensities ("T2-brightness") in axial sections in the L5-level. The results were correlated with the individual's age to find specific alterations that were indicative of sarcopenia or attributable to the aging process. Results: In women (average age 62.6 (34-85) years), musculoskeletal cross-sectional area sizes and diameters were significantly smaller (p < 0.00001) compared to those in men (average age 57.0 (21-90) years). The most pronounced structural age-related change was the increasing mean posterior paravertebral muscle brightness (MPPVB), which exceeded the mean vertebral brightness (MVB) earlier and to a greater extent in women than in men (p < 0.00001). The brightness difference (∆MVB - MPPVB) was found to indicate (pre-)sarcopenia at values below 25. Conclusions: Significant age-related deterioration in muscle quantity and quality was more obvious in women, correlated with the onset of menopause, and progressed to lower levels during aging.