Magnetic Resonance Imaging Segmentation of Soft Tissue in the Diagnosis of Chronic Low Back Pain: A Scoping Review

Background/Objectives: Despite the substantial clinical and socioeconomic burden of chronic low back pain (CLBP), objective diagnostic biomarkers remain limited. Structural alterations of the lumbosacral muscles, particularly muscle atrophy and fatty infiltration (FI), have been proposed as imaging correlates of chronic pain. This scoping review aimed to synthesize current evidence on these alterations in CLBP and characterize the imaging and segmentation methods used. Methods: The review was conducted in accordance with PRISMA-ScR guidelines and guided by the Population–Concept–Context framework. Population: adults with CLBP. Concept: MRI segmentation techniques are used to evaluate morphological soft-tissue changes. Context: clinical and research settings using MRI for CLBP evaluation. A comprehensive search of PubMed, Scopus, Embase, and Web of Science was performed for studies published between January 2014 and October 2024. Results: Twelve observational studies met the inclusion criteria. Degenerative alterations were consistently observed in CLBP and were not reported in control groups. Muscle atrophy was reported in ten studies (multifidus [MF]: 9; erector spinae [ES]: 7; psoas major [PM]: 2; paraspinal muscles [PPM]: 1; and increased FI in all studies (MF: 9; ES: 5; PM: 2; PPM: 2). Considerable heterogeneity between studies was noted. Conclusions: Lumbosacral muscles assessment may provide useful objective information for a more objective characterization of CLBP. Degenerative alterations were reported in all examined muscles except QL, with the MF most consistently affected. Changes in ES and PM may be specific for CLBP. The frequent co-occurrence of muscle atrophy and FI suggests that their combined evaluation may provide complementary information.