title: Novel measurement method on plain radiographs to predict postoperative stem anteversion in cementless THA.
abstract: Preoperative knowledge of femoral stem anteversion can reduce instability and impingement especially using the standard "cup first" technique in cementless total hip arthroplasty (THA). In this study, we asked whether stems at risk of retroversion or high anteversion (>20°) can be detected preoperatively using hip radiographs in two planes (anteroposterior and Lauenstein). In 123 patients undergoing cementless THA using a non-anatomic, non-modular, straight stem, low centered hip radiographs in two planes were obtained preoperatively and three-dimensional computed tomography (3D-CT) 6 week postoperatively. The novel developed Isthmus Ratio (iRatio) as the relation between canal isthmus and calcar isthmus in the anteroposterior and Lauenstein view was calculated by two observers twice in a 6-week interval. iRatio was compared to postoperative 3D-CT stem version measured by an independent and blinded, external institute. We found a correlation between mean radiographic iRatio and 3D-CT stem torsion of r = 0.578 (p < 0.0001). The observers had excellent agreements within (ICC ≥0.918) and between (mean CCC = 0.967) radiographic iRatio measurements. Eighty-one percent (21/26) of the retroverted cementless stems had a preoperative iRatio below 0.35 and 91% (10/11) of stems with an anteversion exceeding 20° an iRatio above 0.55, respectively. The novel iRatio represents a feasible and reliable method for analyzing anteversion of the final stem on plain radiographs before cementless THA with a straight, tapered stem. iRatios below 0.35 and above 0.55 represent a warning of retroversion and anteversion more than 20° of the final stem, respectively. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2025-2030, 2016.
authors.affiliation: Department of Orthopedic Surgery, Regensburg University, Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, Bad Abbach 93077, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Weber
authors.affiliation: Department of Orthopedic Surgery, Regensburg University, Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, Bad Abbach 93077, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Messmer
authors.affiliation: Department of Orthopedic Surgery, Regensburg University, Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, Bad Abbach 93077, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Woerner
authors.affiliation: Department of Orthopedic Surgery, Regensburg University, Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, Bad Abbach 93077, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.affiliation: Department of Orthopedic Surgery, Regensburg University, Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, Bad Abbach 93077, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Renkawitz
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D011859:Radiography / Q000379:methods*; D012189:Retrospective Studies
keywords: femoral anatomy; radiography; stem version; total hip arthroplasty