title: Humeral head sizing using extra-articular landmarks on conventional radiographs.
abstract: OBJECTIVE
  Proper humeral head (HH) sizing is critical to success in anatomic shoulder replacement for management of glenohumeral arthritis. In this study, we evaluate the accuracy and reliability of using non-articular landmarks on conventional radiographs for HH templating.
  
  
  METHODS
  Anatomic HH replacement was performed on five non-arthritic shoulders, from fresh adult cadavers. Pre-operative and post-operative radiographs and 3-D CT scans were obtained. Humeral head size was determined using the articular surface and three extra-articular landmarks (inner aspect of the lateral cortex, the medial footprint of the rotator cuff, and the medial calcar). Two independent observers performed each measurement twice to evaluate reliability. The accuracy was assessed by subtracting the mean values from both the 3D-CT and the implanted HH size measurements.
  
  
  RESULTS
  Intraclass correlation coefficient for Observer 1 and 2 for the three-point method showed excellent test-retest reliability 0.996 (95% CI 0.994-0.998) and 0.997 (95% CI 0.995-0.998), respectively. Inter-observer ICC for the three-point method was 0.996 (95% CI 0.994-0.997) showing high level of precision. The three-point method was overestimating the size of the HH (to 3D-CT) with 0.46 ± 0.61 mm on average. The three-point method predicted the size of the HH within 1 mm of the implanted head size showing very high accuracy. The center of rotation (COR) for the three-point method was within 1.34 mm of the (COR) of the articular surface.
  
  
  CONCLUSIONS
  The three-point measuring technique using conventional radiographs may be useful to predict the HH size using extra-articular landmarks within a small margin of error. This method is simple, cost effective and has high level of precision.
  
  
  METHODS
  Basic Science Study; Anatomic and Imaging Study.
authors.affiliation: Department of Orthopaedic Surgery, University of Illinois at Chicago, 835 S. Wolcott Ave., Room E270, MC 844, Chicago, IL, 60612, USA.
authors.forename: David D
authors.initials: DD
authors.lastname: Savin
authors.affiliation: Department of Orthopaedic Surgery, University of Illinois at Chicago, 835 S. Wolcott Ave., Room E270, MC 844, Chicago, IL, 60612, USA. piponov@uic.edu.
authors.forename: Hristo
authors.identifier: http://orcid.org/0000-0001-6965-609X
authors.initials: H
authors.lastname: Piponov
authors.affiliation: Illinois Bone and Joint Institute, LLC, 9000 Waukegan Road, Suite 200, Morton Grove, IL, 60053, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Goldstein
authors.affiliation: South County Orthopedic Specialists, 24331 El Toro Road, #200, Laguna Woods, CA, 92637, USA.
authors.forename: Ari R
authors.initials: AR
authors.lastname: Youderian
mesh_terms: D059925:Anatomic Landmarks; D000072228:Arthroplasty, Replacement, Shoulder / Q000379:methods*; D002102:Cadaver; D006801:Humans; D058430:Humeral Head / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D021621:Imaging, Three-Dimensional; D010003:Osteoarthritis / Q000000981:diagnostic imaging* / Q000601:surgery*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
keywords: 3-D CT scan; Anatomic shoulder replacement; Glenohumeral arthritis; Humeral head size; Humerus templating; Pre-operative templating; Shoulder arthroplasty; Sphere model