Surgeon Error in Performing Intraoperative Estimation of Stem Anteversion in Cementless Total Hip Arthroplasty Masanobu Hirata, MD, Yasuharu Nakashima, MD, PhD , Masanobu Ohishi, MD, PhD, Satoshi Hamai, MD, PhD, Daisuke Hara, MD, Yukihide Iwamoto, MD, PhD Department of Orthopaedic Surgery, Graduate school of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan abstract article info Article history: Received 23 January 2013 Accepted 12 March 2013 Keywords: femoral anteversion stem anteversion intraoperative estimation total hip arthroplasty computed tomography To examine the accuracy of intraoperative estimation of stem anteversion in total hip arthroplasty (THA), we compared the intraoperatively estimated stem anteversion (estimated prosthetic anteversion) to stem anteversion measured by postoperative computed tomography (true anteversion) in 73 hips in 73 patients. Estimated prosthetic anteversion was significantly greater than true anteversion by 5.8°, and the mean absolute value of surgeon error was 7.3° ranging from 11° underestimation to 25° overestimation. Surgeons tended to overestimate when the true anteversion was smaller. A multivariate analysis showed that advanced knee osteoarthritis significantly increased surgeon error. These results indicated that estimated prosthetic anteversion was generally larger than true anteversion and that the grade of knee osteoarthritis affected the degree of surgeon error. © 2013 Elsevier Inc. All rights reserved. Accurate component placement has been considered a prerequisite for successful total hip arthroplasty (THA) [1–7], as implant malposition directly influences postoperative stability, wear, and aseptic loosening [8,9]. The generally accepted combined anteversion of the cup and stem has been reported to be from 30° to 60° to avoid impingement and maximize hip range of motion [10,11]. The risk of dislocation is reportedly 6.9 times greater if the combined anteversion falls outside the range of 40° to 60° [12]. To achieve the appropriate combined anteversion, a method to adjust cup anteversion according to stem anteversion has been recommended in cementless THA [2,13–15]. Therefore, surgeons should understand how to achieve an accurate stem anteversion using any approach. To our knowledge, there are only two previous studies regarding the accuracy of femoral component placement during a surgical procedure utilizing postoperative computed tomography (CT) [16,17]. Both studies showed that intraoperative estimations were generally accurate with a small difference of 1.0° and 1.5° between intraoperative and postoperative femoral anteversion. However, the difference between the estimation and measurement was presented as an average value instead of an absolute value in spite of including cases with an underestimation or overestimation of the measurement. Therefore, absolute values that incorporate surgeon error should be utilized to evaluate the accuracy of intraoperative estimations. The purposes of this study were (1) to evaluate the absolute difference between the stem anteversion estimated by surgeons intraoperatively and that measured using postoperative CT and (2) to examine the factors that influence this error. Materials and Methods This prospective study was approved by the institutional review board and all patients gave their informed consent. There were 288 patients (299 hips) who underwent primary cementless THA between December 2010 and October 2012. The patients without the agreement for preoperative or postoperative CT were excluded. Cases where an intraoperative estimation was not performed were also excluded. In patients with bilateral involvement, one hip was randomly selected so that the statistical assumption of independent observation was fulfilled. The remaining 73 hips in 73 patients were evaluated. There were 17 men and 56 women. The reason for surgery was osteoarthritis (OA) in 66 hips, including 50 hips with develop- mental dysplasia of the hip (DDH) as defined by a lateral center-edge angle of Wiberg less than 20° [18], osteonecrosis of the femoral head (ONFH) in 6 hips, and rheumatoid arthritis (RA) in 1 hip. The mean age at the time of surgery was 64.3 ± 8.4 years (range, 49–79 years) (Table 1). A cementless titanium-sprayed hemispherical cup and a straight metaphyseal fit stem (AMS & PerFix HA; Japan Medical Material, Osaka, Japan) were used in all cases. All patients underwent cementless primary THA performed by four experienced surgeons using a posterolateral approach. According to the combined anteversion technique, the preparation was started on the femoral side [13–15]. When the trial stem was placed, the stem The Journal of Arthroplasty 28 (2013) 1648–1653 The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2013.03.006. Reprint requests: Yasuharu Nakashima, MD, PhD, Department of Orthopaedic Surgery, Graduate school of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan. 0883-5403/2809-0037$36.00/0 – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2013.03.006 Contents lists available at ScienceDirect The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org