Quantitative assessment of lumbar posterior anatomy on axial t2-weighted MR imaging: a comprehensive analysis of muscle-bone interval and spinous process muscle-ligaments complex.

OBJECTIVE

To quantitatively evaluate the lumbar posterior anatomy, specifically the muscle-bone interval (MBI) and spinous process muscle-ligament complex, using magnetic resonance imaging (MRI) and investigate their clinical significance in surgical approaches.

METHODS

140 patients (70 males and 70 females, aged 20 to 90 years) underwent lumbar spine MRI. Measurements of the MBI and spinous process, including length, width, height, and cross-sectional area, were taken at each lumbar level from L2 to L5 using ImageJ open-source software.

RESULTS

The MBI was confirmed along the midline plane of the spinous processes at the L2-L5 levels. The mean values for the MBI's length, width, height, and cross-sectional area were 20.43 ± 4.44 mm, 10.63 ± 3.18 mm, 12.81 ± 2.99 mm, and 77.57 ± 47.89 mm², respectively. Notably, multifidus muscle (MFM) decreases with age, while MBI increases, with males showing larger MFM and smaller MBI than females. These anatomical features exhibited a gradual increase from L2 to L5.

CONCLUSIONS

We identified the MBI as a significant anatomical space between the MFM, lamina, and the spinous processes, with its prominence increasing in the lower lumbar regions. The MBI expands with age, particularly its cross-sectional area, while the MFM cross-sectional area diminishes. These anatomical changes have notable implications for surgical approaches, including the potential refinement of posterior midline approaches to enhance muscle preservation and surgical outcomes.