Comprehensive quantitative analysis of muscle cross-sectional area and intramuscular fat infiltration of hip using modified DIXON MRI based on chemical shift encoding technique

Purpose Noninvasive quantitative assessment of hip musculature is critically needed, as the structural integrity of hip muscles and the degree of intramuscular fat infiltration are essential determinants of hip stability and function. This study employed a modified DIXON of magnetic resonance imaging (MRI) technique to evaluate the cross sectional area (CSA) and intramuscular fat fraction (IMFF) of hip muscles. We analyzed factors influencing changes in hip muscle structure and intramuscular fat infiltration with the aim of establishing a comprehensive map of hip muscle characteristics. Methods This cross-sectional study enrolled participants from the health examination center of our research institution. All participants underwent 3.0T MRI with mDIXON Quant sequence. The CSA and IMFF of 10 muscles of hip were semi-automatically delineated and measured at four predefined anatomical levels. the effects of sex, age, and laterality on hip muscle CSA and IMFF were investigated. Multivariate analysis was also performed to identify factors influencing IMFF in the hip. Results A total of 177 participants (100 males, 77 females; age range: 18–80 years) were included. The mean age was 52.70 ± 14.36 years for males and 51.58 ± 14.85 years for females. Compared with females, males exhibited significantly smaller subcutaneous fat area (SFA)/subcutaneous fat thickness (SFT) (p < 0.001) and a larger proximal femoral area (PFA) in the hip (p < 0.001). Additionally, males demonstrated larger CSA in all muscles (p < 0.001) and lower IMFF in most muscles (p ≤ 0.001) of hip. With advancing age, the CSA of all 10 hip muscles progressively decreased, while IMFF increased. Laterality had minimal influence on hip muscle CSA and IMFF. Multivariate analyses showed that age as the predominant factor influencing IMFF. Conclusion The mDIXON QUANT sequence enables noninvasive quantification of CSA and IMFF of hip muscles, with age identified as a significant influencing factor. This technique holds promise for establishing normative reference data on hip muscle CSA and IMFF in healthy populations, thereby enhancing the understanding of degenerative changes and aiding in clinical decision-making for surgical planning and postoperative rehabilitation guidance.