Characteristics of paraspinal muscle in asymptomatic population with pelvic anteversion: correlation between bony...

Anteverted pelvis (AP) subgroup is unusual subtype in asymptomatic population characterized by low pelvic incidence (PI), high lumbar lordosis (LL), and a sloped sacrum. However, the contribution of paraspinal muscles (PSM) to this specific alignment has not been clarified. The purpose of this study was to determine if the AP subgroup was associated with different characteristics in the cross-sectional area (CSA) and fat infiltration (FI) of PSM.

A cross-sectional study was conducted with 168 asymptomatic volunteers. MRI was used to assess the CSA and FI of the multifidus (MF), erector spinae (ES), and psoas (PS), and the ES and MF were added up as lumbar extensor muscles (LEM). Sagittal parameters were measured via whole-spine radiographs, and were compared in AP and non-AP subgroup. Correlation analysis was applied between sagittal parameters and PSM. Further, an age, sex and PI matched control group of AP group was built to compare the PSM. Linear regression analysis was applied to explore the potential influence factor of PSM.

In AP subgroup, larger LL, sacral slope (SS) and smaller PI were discovered(P < 0.001). In the general cohort, PI, SS and LL were found to be positively related to the CSA and fCSA of LEM (P < 0.05). Comparing to control group, AP individuals showed significantly larger CSA and fCSA in MF (CSA 0.82 ± 0.17vs 0.7 ± 0.14, P < 0.001; fCSA 0.57 ± 0.15vs 0.47 ± 0.12, P < 0.001) and LEM (CSA 1.57 ± 0.45vs 1.36 ± 0.35, P = 0.016; fCSA 1.07 ± 0.38vs 0.89 ± 0.31, P = 0.017) at L5-S1, while no statistical significance was found in PS. Regression analysis indicated that age(β=-0.184, P = 0.014), pelvic anteversion(β = 0.293, P = 0.008), and PI(β = 0.399, P = 0.004) were independent predictive factors of LEM CSA. For LEM fCSA, pelvic anteversion (β = 0.272, P = 0.013) and PI (β = 0.356, P = 0.011) were also independent predictive factors.

Asymptomatic individuals with AP possess significantly stronger LEM at the lumbosacral junction. The findings suggest that LEM could play a critical role in maintaining lumbar curvature and pelvic rotation in AP subgroup. This study highlights the importance of considering the individualized bone-muscle match when analyzing sagittal balance.