Spinal Sarcopenia in Patients with Spinal Osteoarthritis Across Different Age Groups: Clinical and MRI Characteristics

IntroductionSarcopenia of the spinal stabilizing muscles is one of the components of age-related sarcopenia and often associated with chronic back pain (CBP), including spinal osteoarthritis (OA). The age dynamics of paraspinal muscle mass in spinal OA is not sufficiently studied to date, although it is key in developing rehabilitation and prevention strategies. The aim of studyis to identify spinal sarcopenia in individuals with spinal OA by assessing paraspinal muscles mass and analyzing its relationship to degenerative spinal changes in different age groups using magnetic resonance imaging (MRI). Materials and methodsThe study included 90 patients with spinal OA classified as stages 4 and 5 of degenerative disc disease according to the Pfirrmann grading system. Participants were evenly distributed across three age groups: young adults (Me: 36.00 [30.00-42.00]), middle age (Me: 50.00 [46.50-56.25]), and elderly (Me: 66.00 [62.50-71.00]). All participants underwent lumbar spine MRI in two sections - sagittal and axial - in T1- and T2-weighted images. Clinical assessments included evaluating the functional status of the lumbar spine using the Backache Index (BAI). Paraspinal muscle mass analysis was performed on axial sections at the level of the third lumbar vertebra (L3) for the following muscles: musculus psoas major, musculus erector spinae, and musculus quadratus lumborum. To comparatively assess spinal muscle mass, the musculovertebral index (MVI) was calculated by dividing the total cross-sectional area of the three pair muscles (Sm, cm{superscript 2}) by the cross-sectional area of the third lumbar vertebra (Sv, cm{superscript 2}) at the upper endplate level: MVI = (Sm dextra + Sm sinistra) / Sv. To identify the asymmetries of the paraspinal muscles, the ratio of the cross-sectional areas of the three muscles on the left and right sides was calculated. Additionally, the transverse torso thickness at L3 level was measured on sagittal sections. ResultsThe mean MVI values demonstrated that paraspinal muscle mass was significantly lower in elderly (p = 0.0001) and middle-aged (p = 0.025) groups compared to the young group, which indicates its decrease with age in patients. Statistically significant increase in the lumbar vertebra area with age (p=0.0003 young vs elderly) is explained by the spondylosis development and age-related marginal osteophyte growth as manifestations of spinal OA. The reduction in muscle cross-sectional area was evident for three right paraspinal muscle groups with age (p = 0.0252). Asymmetry for each pair of muscles was observed across all age groups, the right side always being larger than the left, particularly in the quadratus lumborum, where it was most pronounced in middle-aged (p = 2.762 x 10-6) and young individuals (p = 0.0009). The elderly persons demonstrated a tendency toward higher body mass index, a higher percentage of obese individuals, and increased torso thickness compared to the middle-aged and young groups (p = 0.067), suggesting a possible decline in abdominal muscle tone with age alongside body weight gain. ConclusionsMRI findings reveal an age-related decline in paraspinal muscle mass among patients with CBP, indicating the development of spinal sarcopenia, which likely contributes to the clinical course of spinal OA in the elderly. All three groups of muscles show asymmetry in all age groups, with the right side always being larger than the left. Torso thickness and body weight increase with age in patients with spinal OA potentially exacerbate the diseases clinical progression. These findings highlight the need to include exercises targeting paraspinal and abdominal muscles in rehabilitation programs for patients with spinal OA in all age groups. Preventing spinal spinal sarcopenia by maintaining axial muscle stability is essential for preserving the spinal muscle framework and is an integral component of managing patients with CBP.