Reliability of Intraoperative 3D-Fluoroscopic Imaging in Assessing Acetabular Fracture Reduction

OBJECTIVES: To assess image quality and reliability of intraoperative 3D fluoroscopy in assessing acetabular reduction. METHODS: Design : Retrospective chart review Setting: Academic, level 1 trauma center Patient Selection Criteria: Adult patients with acetabular fractures involving weight-bearing dome and/or posterior wall (OTA/AO 62A, 62B, 62C) between 2017-2023 with intraoperative 3D fluoroscopy and postoperative computed tomography (CT) included. Outcome Measures and Comparisons: Gap and step-off measurements made on intraoperative 3D fluoroscopy and postoperative CT by two graders using standardized technique. Assessments of image quality made using a scale of 1 (uninterpretable) to 5 (excellent). Interclass correlation coefficients (ICC) used to compare 3D fluoroscopy to CT and assessed intra/interobserver reliability for 3D fluoroscopy and CT images. Appropriate tests of significance performed. RESULTS: 54 patients with mean age of 48.4 ± 21.0 included. 72.2% of patients were male. 56/106 (52.8%) 3D fluoroscopic scans rated as 1/5 or 2/5. All CT images rated 3/5 or higher (p<0.001). 70% of CT measurements made with high confidence while 2.8% of 3D fluoroscopy measurements received this rating (p<0.001). Moderate agreement for gap (ICC=0.518, p<0.01) and step-off (ICC=0.420, p<0.01) when comparing 3D fluoroscopy to CT. CT showed good intra-reliability (ICC=0.747, 0.864; p<0.001) while 3D fluoroscopy showed moderate intra-reliability (ICC=0.638, 0.604; p<0.001). CT showed greater inter-reliability for largest gap (ICC 0.621, p<0.001) compared to fluoroscopy (ICC 0.219, p=0.05). CONCLUSIONS: When assessing acetabular fracture reduction involving the weight-bearing dome and/or posterior wall, intraoperative 3D fluoroscopy performed worse than postoperative CT on measures of image quality and confidence in reduction assessment. 3D fluoroscopy showed poor ICC across all views compared to CT and performed worse for interrater reliability. 3D fluoroscopy has limitations when making final acetabular reduction assessments; it may be advisable to acquire postoperative CT. LEVEL OF EVIDENCE: Level III, diagnostic