Operative Fluoroscopic Correction Is Reliable and Correlates With Postoperative Radiographic Correction in Periacetabular Osteotomy

Background Intraoperative fluoroscopy is commonly used to both guide the osteotomy and judge correction of the acetabular fragment in periacetabular osteotomy (PAO). Prior studies that have compared intraoperative fluoroscopic correction with postoperative radiographic correction were small studies that did not report intra- or interreader reliability. Questions/purposes (1) What is the correlation between intraoperative fluoroscopic correction in PAO compared with the correction seen on postoperative radiographs? (2) What is the reliability of radiographic measures of correction in PAO? Methods We performed a retrospective study of 121 patients (141 hips) who underwent PAO for symptomatic hip dysplasia at a tertiary referral center. Patients were included in the study if they had preoperative radiographs, intraoperative fluoroscopy, and minimum 6-week postoperative radiographs. Of the 272 PAO procedures performed in this time period, 61 patients who underwent PAO for retroversion and five patients with a history of Perthes disease were excluded as a result of the inability for these radiographic measures to judge fragment correction in PAOs for retroversion and the difficulty in measurement in post-Perthes deformity. Of the 206 PAOs performed for symptomatic acetabular dysplasia, 65 (32%) could not be analyzed because they lacked appropriate preoperative films, leaving 141 PAOs in 121 patients for analysis. The patients lacking appropriate preoperative films had them performed at an outside facility or had plain films that have since been destroyed. The lateral center-edge angle (LCEA) and acetabular index (AI) on the fluoroscopic views and postoperative radiographs were measured by two authors. The concordance between the amount of correction on intraoperative fluoroscopy and minimum 6-week postoperative measurements was analyzed using the concordance correlation coefficient (r(c)) and a Bland-Altman analysis. Intra-and interrater reliability was calculated between measurements. Results The amount of intraoperative correction of LCEA as measured on fluoroscopic images demonstrated substantial agreement with postoperative radiographs (r(c) = 0.79; 95% confidence interval [CI], 0.73-0.85; p < 0.001) as did the AI (r(c) = 0.77; 95% CI, 0.70-0.84; p < 0.001). The mean difference between intraoperative correction was only -0.38 degrees (SD 3.6 degrees) for LCEA and -0.84 degrees (SD 3.4 degrees) for AI. Interrater reliability for both LCEA and AI also demonstrated substantial agreement (all, r(c) = 0.70-0.90) for preoperative, operative, and postoperative imaging. Furthermore, intrarater reliability for both LCEA and AI demonstrated almost perfect agreement for all measures (all, r(c) > 0.81). Conclusions Intraoperative fluoroscopy is an accurate and reliable measure of correction of lateral coverage of the acetabular fragment during PAO. Further studies on measures of anterior coverage and acetabular version are needed to validate intraoperative fluoroscopic correction in these planes.