Prospective Paired Evaluation of Conventional Versus Structured Magnetic Resonance Imaging Interpretation for Preoperative Assessment of Gluteal Permanent Synthetic Filler Disease

This prospective paired diagnostic-impact study will compare conventional qualitative MRI reporting with a new structured anatomic classification in adults undergoing surgery for gluteal permanent synthetic filler disease. The structured report will document material effects across superficial, deep, muscular, regional, lymphatic, and interstitial compartments. Standardized intraoperative mapping will serve as the reference standard. The main outcome is the difference in sensitivity for surgically confirmed compartment involvement

Inclusion Criteria: * Age 18 years or older. * History of gluteal injection with a permanent or unknown nonresorbable filler. * Preoperative pelvic/gluteal MRI performed using the study acquisition protocol. * Planned surgical removal, biopsy, or operative exploration within 90 days after MRI. * Written informed consent for paired image interpretation and use of operative findings. Exclusion Criteria: * MRI contraindication or nondiagnostic imaging caused by motion or incomplete anatomic coverage. * Prior extensive gluteal filler removal that prevents mapping of the predefined compartments. * No operative procedure within 90 days after MRI and therefore no reference-standard assessment. * Acute life-threatening infection or emergency surgery that prevents completion of the preoperative reporting sequence. * Inability to provide consent.