What Is the Reliability and Accuracy of Intraoperative Fluoroscopy in Evaluating Anterior, Lateral, and Posterior Coverage During Periacetabular Osteotomy?

BACKGROUND: Periacetabular osteotomy (PAO) is an established treatment for acetabular dysplasia in the skeletally mature individual. Fluoroscopy is used intraoperatively for osteotomy completion and to judge fragment correction. However, a comprehensive study validating fluoroscopy to judge anterior, lateral, and posterior coverage in PAO has not been reported. QUESTIONS/PURPOSES: (1) Are radiographic and fluoroscopic measures of anterior, lateral, and posterior acetabular coverage reliable? (2) Do fluoroscopic measures of fragment correction accurately measure anterior, lateral, and posterior coverage when compared with postoperative radiographs?
METHODS: We performed a retrospective study of patients undergoing PAO with a primary diagnosis of acetabular dysplasia. Between 2012 and 2014 two surgeons performed 287 PAOs with fluoroscopy. To be included in this retrospective study, patients had to be younger than 35 years old, have a primary diagnosis of dysplasia (not retroversion, Perthes, or skeletal dysplasia), have adequate radiographic and fluoroscopic imaging, be a primary PAO (not revision), and in the case of bilateral patients, only the first hip operated on in the study period was included. Based on these criteria, 46% of the PAOs performed were included here (133 of 287). A total of 109 (82%) of the patients were females (109 of 133), and the mean age of the patients represented was 24 years (SD, 7 years). Pre- and postoperative standing radiographs as well as intraoperative fluoroscopic images were reviewed and lateral center-edge angle (LCEA), Tönnis angle (TA), anterior center-edge angle (ACEA), anterior wall index (AWI), and posterior wall index (PWI) were measured. Two fellowship-trained hip preservation surgeons completed all measurements with one reader performing a randomized sample of 49 repeat measurements 4 weeks after the initial reading for purposes of calculating intraobserver reliability. Intra- and interrater reliability was assessed using an intraclass correlation coefficient (ICC) model. Agreement between intraoperative fluoroscopic and postoperative radiographic measures was determined by estimating the ICC with 95% confidence intervals and by Bland-Altman analysis.
RESULTS: Intrarater reliability was excellent (ICC > 0.75) for all measures and good for postoperative AWI (ICC = 0.72; 95% confidence interval [CI], 0.48-0.85). Interrater reliability was excellent (ICC > 0.75) for all measures except intraoperative TA (ICC = 0.72; 95% CI, 0.48-0.84). Accuracy of fluoroscopy was good (0.60 < ICC < 0.75) for LCEA (ICC = 0.73; 95% CI, 0.55-0.83), TA (ICC = 0.66; 95% CI, 0.41-0.79), AWI (ICC = 0.63; 95% CI, 0.48-0.74), and PWI (ICC = 0.72; 95% CI, 0.35-0.85) and excellent (ICC > 0.75) for ACEA (ICC = 0.80; 95% CI, 0.71-0.86). Bland-Altman analysis for systematic bias in the comparison between intraoperative fluoroscopy and postoperative radiography found the effect of such bias to be negligible (mean difference: LCEA 2°, TA 2°, ACEA 1°, AWI 0.02, PWI 0.11).
CONCLUSIONS: Fluoroscopy is accurate in measuring correction in PAO. However, surgeons should take care not to undercorrect the posterior wall. Based on our study, intraoperative fluoroscopy may be used as an alternative to an intraoperative AP pelvis radiograph to judge final acetabular fragment correction with an experienced surgeon. However, more studies are needed including a properly powered direct comparative study of intraoperative fluoroscopy and intraoperative radiographs. Moreover, the impact of radiographic correction achieved during surgery should be studied to determine the implications for patient-reported outcomes and long-term survival of the hip. LEVEL OF EVIDENCE: Level IV, diagnostic study.