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
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.
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.
Adults with prior gluteal injection of permanent synthetic fillers who undergo preoperative pelvic/gluteal MRI and are scheduled for surgical removal or exploration.
Other
Prospective
Conventional Qualitative MRI Interpretation
Diagnostic testThe report records the presence or absence of injected foreign material in the gluteal region and any routinely reported findings. A preliminary surgical plan is recorded after review of this report. Linked arm/group(s): Paired MRI Interpretation Cohort.
Structured Gluteal Filler MRI Classification
Diagnostic testThe report records material distribution and severity in predefined compartments: fat-fascia interface, subcutaneous fat, deep fascia, gluteal muscles, subcrestal region, ischial region, trochanteric region, pelvic ring, lymphatic pathways, and interstitial involvement. The final classification manual and grade definitions will be locked before enrollment. Linked arm/group(s): Paired MRI Interpretation Cohort.
Standardized Intraoperative Anatomic Mapping
Procedure/SurgeryDuring the index operation, the surgeon documents actual involvement of each predefined compartment before reviewing the imaging accuracy analysis. Operative photographs, specimen mapping, and histopathology may support the reference standard. Linked arm/group(s): Paired MRI Interpretation Cohort.
Sensitivity for Surgically Confirmed Anatomic Compartment Involvement
For each reporting method, sensitivity is the number of predefined compartments identified as involved on MRI divided by the number confirmed as involved during standardized intraoperative mapping. The structured and conventional results will be compared within the same participant.
Specificity for Surgically Uninvolved Anatomic Compartments
For each method, specificity is the number of compartments correctly identified as uninvolved on MRI divided by the number documented as uninvolved at surgery.
Change in Preoperative Surgical Plan After Structured MRI Review
Proportion of participants for whom the recorded operative plan changes after the structured report, including planned incision, extent of excision, anticipated deep-plane dissection, lymphatic evaluation, or reconstruction strategy.
Surgeon-Rated MRI Report Utility
The operating surgeon rates completeness, anatomic clarity, confidence, and usefulness for planning on prespecified 0-to-10 scales after each report. Higher scores indicate greater perceived utility.
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