This prospective agreement study will compare preoperative MRI measurements with direct surgical measurements in adults undergoing removal of gluteal tissue affected by permanent synthetic fillers. MRI will estimate affected-tissue dimensions and residual skin-flap thickness at predefined landmarks. During surgery, the same flap landmarks and the fresh excised specimen will be measured. The primary outcome is agreement between MRI and intraoperative flap thickness; postoperative ischemia, wound dehiscence, and necrosis will be followed through 30 days.
Age 18 years or older.
Gluteal permanent synthetic filler disease scheduled for elective surgical excision.
Preoperative MRI performed within 90 days before surgery using the study measurement protocol.
Planned skin/subcutaneous flap elevation that permits direct thickness measurement at predefined landmarks.
Emergency surgery or active uncontrolled infection that prevents standardized preoperative imaging or measurement.
Prior surgery causing loss of the predefined landmarks or making paired measurement impossible.
Nondiagnostic MRI or incomplete coverage of the planned operative field.
Specimen fragmentation that prevents standardized fresh-specimen dimension measurement for the secondary endpoint.
Adults scheduled for surgical excision of gluteal tissue affected by permanent synthetic fillers after preoperative MRI.
Cohort
Prospective
Preoperative MRI Morphometric Mapping
Diagnostic testThree orthogonal dimensions of the affected block and residual flap thickness at fixed surface landmarks will be measured on MRI by two trained readers. Affected-tissue volume will be estimated using segmentation when available and a prespecified geometric approximation otherwise. Linked arm/group(s): MRI-to-Surgery Agreement Cohort.
Standardized Intraoperative and Fresh-Specimen Measurement
Procedure/SurgeryBefore closure, residual flap thickness will be measured with a calibrated sterile device at the same mapped landmarks without compressing the tissue. The fresh excised block will be oriented and measured in three axes before fixation. Specimen weight will also be recorded. Linked arm/group(s): MRI-to-Surgery Agreement Cohort.
Agreement Between MRI and Intraoperative Residual Flap Thickness
Residual skin-subcutaneous flap thickness in millimeters will be measured at predefined mapped landmarks on MRI and directly during surgery. Agreement will be summarized using intraclass correlation, mean bias, 95% limits of agreement, and absolute error.
Agreement Between MRI and Fresh-Specimen Affected-Tissue Dimensions
Maximum craniocaudal, mediolateral, and anteroposterior dimensions in centimeters will be compared between MRI and the oriented fresh specimen before fixation.
Absolute Percentage Error in Predicted Affected-Tissue Volume
Absolute difference between MRI-predicted and specimen-derived volume divided by specimen-derived volume and multiplied by 100. Lower values indicate more accurate prediction.
Incidence of Ischemic Wound Complications
Proportion of participants with clinically documented flap ischemia, partial- or full-thickness tissue necrosis, or wound dehiscence judged to be related to tissue perfusion.
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