title: Effect of surgical experience on imageless computer-assisted femoral component positioning in hip resurfacing--a preclinical study.
abstract: BACKGROUND
  The clinical outcome of hip resurfacing (HR) as a demanding surgical technique associated with a substantial learning curve depends on the position of the femoral component. The aim of the study was to investigate the effects of the level of surgical experience on computer-assisted imageless navigation concerning precision of femoral component positioning, notching, and oversizing rate, as well as operative time.
  
  
  METHODS
  Three surgeons with different levels of experience in both HR and computer-assisted surgery (CAS) prepared the femoral heads of 54 synthetic femurs using the Durom(TM) Hip Resurfacing (Zimmer, Warsaw, IN, USA) system. Each surgeon prepared a total of 18 proximal femurs using the Navitrack® system (ORTHOsoft Inc., Montreal, Canada) or the conventional free-hand Durom(TM) K-wire positioning jig. The differences between planned and postoperative stem shaft angle (SSA) and anteversion angle in standardized x-rays were measured and the operative time, not including the time for calibrating the CAS-system, was documented. Notching was evaluated by the three surgeons in a randomized manner. Oversizing was determined by the difference of the preoperative determined cap and the cap size advised by the CAS-system.
  
  
  RESULTS
  CAS significantly reduced the overall mean deviation between planned and postoperative SSA in comparison with the conventional procedure (mean ± SD, 1 ± 1.7° vs. 7.4 ± 4.4°, P < 0.01) regardless of the surgeon's level of experience. The incidence of either varus or valgus SSA deviations exceeding 5° were 1/27 for CAS and 15/27 for the conventional method, respectively (P < 0.001), corresponding to a reduction by 97%. Using CAS, the rate of notching was reduced by 100%.
  
  
  CONCLUSIONS
  The accuracy of femoral HR component orientation is significantly increased by use of CAS regardless of the surgeon's level of experience in our preclinical study. Thus, imageless computer-assisted navigation can be a valuable tool to improve implant positioning in HR for surgeons at any stage of their learning curve.
authors.affiliation: University Centre for Orthopaedics & Trauma Surgery, University Hospital Carl Gustav Carus at Technische Universität Dresden, Fetscherstr. 74, Building 29, D-01307, Dresden, Germany. maik.stiehler@uniklinikum-dresden.de.
authors.forename: Maik
authors.initials: M
authors.lastname: Stiehler
authors.affiliation: University Centre for Orthopaedics & Trauma Surgery, University Hospital Carl Gustav Carus at Technische Universität Dresden, Fetscherstr. 74, Building 29, D-01307, Dresden, Germany. jens.goronzy@uniklinikum-dresden.de.
authors.forename: Jens
authors.initials: J
authors.lastname: Goronzy
authors.affiliation: Department of Orthopaedics, St. Vincentius Clinic, Steinhäuserstrasse 18, 76135, Karlsruhe, Germany. stephan.kirschner@vincentius-ka.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Kirschner
authors.affiliation: University Centre for Orthopaedics & Trauma Surgery, University Hospital Carl Gustav Carus at Technische Universität Dresden, Fetscherstr. 74, Building 29, D-01307, Dresden, Germany. albrecht.hartmann@uniklinikum-dresden.de.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Hartmann
authors.affiliation: Dermatological Practice, Kirchplatz 3, 87059, Immenstadt, Germany. torsten.schaefer4@gmx.de.
authors.forename: Torsten
authors.initials: T
authors.lastname: Schäfer
authors.affiliation: University Centre for Orthopaedics & Trauma Surgery, University Hospital Carl Gustav Carus at Technische Universität Dresden, Fetscherstr. 74, Building 29, D-01307, Dresden, Germany. klaus-peter.guenther@uniklinikum-dresden.de.
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Günther
mesh_terms: D019643:Arthroplasty, Replacement / Q000193:education / Q000379:methods*; D005269:Femur / Q000601:surgery*; D006801:Humans; D066231:Surgeons / Q000193:education*; D025321:Surgery, Computer-Assisted / Q000193:education / Q000379:methods*