title: Visual intraoperative estimation of range of motion is misleading in minimally invasive total hip arthroplasty.
abstract: BACKGROUND
  Generally range of motion (ROM) in total hip arthroplasty (THA) is intraoperatively assessed by eye. Can we assume that visual estimation of ROM is reliable?
  
  
  METHODS
  60 patients underwent cementless THA in a subgroup analysis of a clinical prospective trial using a minimally invasive anterolateral approach in lateral decubitus position. Four experienced surgeons intraoperatively estimated ROM visually by assessment of the femur relative to the alignment of the patient's pelvis. These estimations were compared with computer navigation measurements.
  
  
  RESULTS
  We found a mean difference between navigation measurements and intraoperative estimations by eye of -5.6° (±10.9°; -17° to 30°) for flexion, respectively, -0.4° (±10.7°; -24° to 30°) for extension, 8.7° (±9.0°; -10° to 34°) for abduction, 5.9° (±18.3°; -58° to 68°) for external rotation and -5.8° (±12.1°; -38° to 22°) for internal rotation. Multivariate analysis showed no association between the visual accuracy of estimation of ROM and patient characteristics, such as BMI, sex, grade of osteoarthritis and treatment side except for a significant correlation of visual accuracy of estimation of extension and the level of professional experience. Otherwise, the level of professional experience had no impact on the accuracy of estimation of ROM by eye.
  
  
  CONCLUSIONS
  Even the experienced surgeon's intraoperative estimation of ROM by eye is not reliable and differs up to 30° compared to objective measurements in minimally invasive THA. For accurate intraoperative assessment of ROM, the use of technical devices is recommended.
  
  
  BACKGROUND
  DRKS00000739.
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany. mw2905@web.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Woerner
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Weber
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany.
authors.forename: Ernst
authors.initials: E
authors.lastname: Sendtner
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Springorum
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Worlicek
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Craiovan
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.affiliation: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077, Bad Abbach, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Renkawitz
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D005269:Femur; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D015207:Osteoarthritis, Hip / Q000601:surgery*; D010388:Pelvis; D010808:Physical Examination / Q000379:methods; D011446:Prospective Studies; D016059:Range of Motion, Articular
keywords: Arthroplasty; Hip; Measurement; Navigation; ROM; Visual estimation