BACKGROUND: Paraspinal muscle fatty infiltration (FI) is common in lumbar degenerative disease (LDD) and is associated with pain, functional impairment, and adverse postoperative outcomes. However, the association between FI and clinical outcomes remains inconsistent across studies. These inconsistencies may partly reflect differences in how FI is measured and reported. Standardized measurement and reporting are needed. METHODS: This study was conducted as a topic-oriented narrative review. Relevant literature published between January 1, 2015, and March 31, 2026, was identified through searches of PubMed and the Web of Science Core Collection. The search terms covered the paraspinal muscles, FI, imaging-based FI measurement methods, and LDD and its major subtypes. After duplicate removal, title and abstract screening, and full-text eligibility assessment according to predefined inclusion and exclusion criteria, 35 articles were included. The included studies were narratively synthesized and classified as clinical or methodological evidence to summarize the clinical significance of FI, heterogeneity in imaging-based measurement, and the need for standardization. MAIN BODY: FI is assessed using a variety of methods, but key measurement parameters and reporting practices remain inconsistent. Across studies, substantial variation exists in imaging sequences, acquisition settings, region of interest (ROI) delineation, sampling levels, and post-processing workflows. This heterogeneity reduces reproducibility and limits comparisons across studies. In addition, FI is still most commonly quantified using manual, two-dimensional, single-slice measurements. This approach is time-consuming and fails to capture the three-dimensional heterogeneity of the paraspinal muscles. Its applicability in large-cohort and multicenter studies is therefore limited. The aim of this narrative review is to summarize the major methods used for FI assessment, outline their strengths, limitations, and appropriate applications, and propose a three-layer standardization framework, together with standardized measurement and reporting procedures, to improve reproducibility and comparability across studies. CONCLUSION: In FI-related clinical research, standardized reporting of measurement parameters and processing workflows is essential to improve reproducibility and comparability across studies. Such standardization will also provide a foundation for multicenter studies, automated segmentation, three-dimensional quantification, and broader clinical application of FI assessment.
Dai et al. (Fri,) studied this question.