title: Native femoral anteversion should not be used as reference in cementless total hip arthroplasty with a straight, tapered stem: a retrospective clinical study.
abstract: Improper femoral and acetabular component positioning can be associated with instability, impingement, component wear and finally patient dissatisfaction in total hip arthroplasty (THA). The concept of "femur first"/"combined anteversion", incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position of the stem relative to the cup intraoperatively. In the present study we asked two questions: (1) Do native femoral anteversion and anteversion of the implant correlate? (2) Do anteversion of the final broach and implant anteversion correlate?
  
  
  
  In a secondary analysis of a prospective controlled trial, a subgroup of 55 patients, who underwent computer-assisted, cementless THA with a straight, tapered stem through an anterolateral, minimally invasive (MIS) approach in a lateral decubitus position were examined retrospectivly. Intraoperative fluoroscopy was used to verify a "best-fit" position of the final broach. An image-free navigation system was used for measurement of the native femoral version, version of the final broach and the final implant. Femoral neck resection height was measured in postoperative CT-scans. This investigation was approved by the local Ethics Commission (No.10-121-0263) and is a secondary analysis of a larger project (DRKS00000739, German Clinical Trials Register May-02-2011).
  
  
  
  The mean difference between native femoral version and final implant was 1.9° (+/- 9.5), with a range from -20.7° to 21.5° and a Spearman's correlation coefficient of 0.39 (p < 0.003). In contrast, we observed a mean difference between final broach and implant version of -1.9° (+/- 3.5), with a range from -12.7° to 8.7° and a Spearman's correlation coefficient of 0.89 (p < 0.001). In 83.6 % (46/55) final stem version was outside the normal range as defined by Tönnis (15-20°). The mean femoral neck resection height was 7.3 mm (+/- 5.6). There was no correlation between resection height and version of the implant (Spearman's correlation coefficient 0.14).
  
  
  
  Native femoral version significantly differs from the final anteversion of a cementless, straight, tapered stem and therefore is not a reliable reference in cementless THA. Measuring anteversion of the final "fit and fill" broach is a feasible assistance in order to predict final stem anteversion intraoperatively. There is no correlation between femoral neck resection height and version of the implant.
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany. michael.worlicek@gmx.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Worlicek
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Weber
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Craiovan
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Wörner
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Völlner
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany.
authors.forename: Hans R
authors.initials: HR
authors.lastname: Springorum
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.affiliation: Departement of Orthopedic Surgery, University of Regensburg, Asklepios Medical Centre, Kaiser-Karl-V-Allee 3, D-93077, Bad Abbach, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Renkawitz
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000379:methods*; D060750:Bone Anteversion / Q000150:complications*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D005471:Fluoroscopy; D006622:Hip Prosthesis; D006801:Humans; D007430:Intraoperative Care / Q000379:methods; D008875:Middle Aged; D011182:Postoperative Care / Q000379:methods; D011446:Prospective Studies; D011474:Prosthesis Design; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed
keywords: Combined anteversion; Hip arthroplasty; Imageless navigation; Stem version