Validité de la mesure peropératoire de l’antéversion de la pièce fémorale et facteurs d’erreur dans l’arthroplastie totale de hanche non cimentée par voie postéro-latérale

Abstract

BackgroundIntraoperative estimation of stem anteversion in total hip arthroplasty (THA) using postero-lateral approach is made by the surgeon's visual assessment, using the tibia as a guide, with the assumption that tibial axis is vertical to the trans-epicondylar axis. However, the accuracy of the intraoperative estimation has rarely been verified with postoperative CT-scans, with controversies regarding these measurements particularly in case of knee osteoarthritis. Therefore, we performed a prospective study to: (1) determine the accuracy of the intraoperative measurement and (2) investigate factors affecting the discrepancy between the surgeon's estimation and the real stem anteversion. HypothesisIntraoperative estimation of stem anteversion correlated with the real stem anteversion on CT scan. Patients and methodsSixty-seven THAs using cementless straight stems (65 patients) without ipsilateral total knee arthroplasty were prospectively evaluated to compare the intraoperative measurement of stem anteversion with the real stem anteversion on computed tomography (CT) scans. There were 33 men and 34 women with a mean age of 59.7 years (range, 27–84 years) at the time of surgery. Age, tibia plateau angle, native femoral anteversion, femoro-tibial angle, body mass index, operative site, gender, coronal and sagittal tilt of the stem, stem type, ipsilateral knee osteoarthritis, and preoperative diagnosis were analyzed to evaluate the factors affecting the discrepancy between the intraoperative and CT measurements. ResultsThe intraoperative estimation (mean, 21.5°±8.5°; range, 5.0°–39.0°) was greater than the CT measurement (mean, 19.5°±8.7°; range, 4.5°–38.5°) by 2.0°. The mean absolute value of discrepancy was 4.5°. The correlation coefficient between intraoperative and CT measurements was 0.837. The femoro-tibial angle was associated with the discrepancy between the two measurements. In the presence of genu varum deformity, the intraoperative measurement underestimated the stem anteversion. DiscussionAlthough intraoperative estimation of stem anteversion was slightly greater than the real stem anteversion, there was an excellent correlation between the two. The femoro-tibial angle should be considered to optimize the stem anteversion during cementless THA using postero-lateral approach. Level of evidenceIII, prospective case control study.