title: Computer algorithms for three-dimensional measurement of humeral anatomy: analysis of 140 paired humeri.
abstract: BACKGROUND
  In the presence of severe osteoarthritis, osteonecrosis, or proximal humeral fracture, the contralateral humerus may serve as a template for the 3-dimensional (3D) preoperative planning of reconstructive surgery. The purpose of this study was to develop algorithms for performing 3D measurements of the humeral anatomy and further to assess side-to-side (bilateral) differences in humeral head retrotorsion, humeral head inclination, humeral length, and humeral head radius and height.
  
  
  METHODS
  The 3D models of 140 paired humeri (70 cadavers) were extracted from computed tomographic data. Geometric characteristics quantifying the humeral anatomy in 3D were determined in a semiautomatic fashion using the developed computer algorithms. The results between the sides were compared for evaluating bilateral differences.
  
  
  RESULTS
  The mean bilateral difference of the humeral retrotorsion angle was 6.7° (standard deviation [SD], 5.7°; range, -15.1° to 24.0°; P = .063); the mean side difference of the humeral head inclination angle was 2.3° (SD, 1.8°; range, -5.1° to 8.4°; P = .12). The side difference in humeral length (mean, 2.9 mm; SD, 2.5 mm; range, -8.7 mm to 10.1 mm; P = .04) was significant. The mean side difference in the head sphere radius was 0.5 mm (SD, 0.6 mm; range, -3.2 mm to 2.2 mm; P = .76), and the mean side difference in humeral head height was 0.8 mm (SD, 0.6 mm; range, -2.4 mm to 2.4 mm; P = .44).
  
  
  CONCLUSIONS
  The contralateral anatomy may serve as a reliable reconstruction template for humeral length, humeral head radius, and humeral head height if it is analyzed with 3D algorithms. In contrast, determining humeral head retrotorsion and humeral head inclination from the contralateral anatomy may be more prone to error.
authors.affiliation: Computer Assisted Research and Development Group, Balgrist University Hospital, University of Zurich, Zürich, Switzerland; Computer Vision Laboratory, ETH Zürich, Switzerland. Electronic address: lvlachopoulos@card.balgrist.ch.
authors.forename: Lazaros
authors.initials: L
authors.lastname: Vlachopoulos
authors.affiliation: Computer Vision Laboratory, ETH Zürich, Switzerland.
authors.forename: Celestine
authors.initials: C
authors.lastname: Dünner
authors.affiliation: Computer Vision Laboratory, ETH Zürich, Switzerland.
authors.forename: Tobias
authors.initials: T
authors.lastname: Gass
authors.affiliation: Computer Assisted Research and Development Group, Balgrist University Hospital, University of Zurich, Zürich, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Graf
authors.affiliation: Computer Vision Laboratory, ETH Zürich, Switzerland.
authors.forename: Orcun
authors.initials: O
authors.lastname: Goksel
authors.affiliation: Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zürich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Gerber
authors.affiliation: Computer Vision Laboratory, ETH Zürich, Switzerland.
authors.forename: Gábor
authors.initials: G
authors.lastname: Székely
authors.affiliation: Computer Assisted Research and Development Group, Balgrist University Hospital, University of Zurich, Zürich, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Fürnstahl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002102:Cadaver; D005260:Female; D006801:Humans; D006811:Humerus / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Three-dimensional; algorithms; anatomy; bilateral; computer assisted; humerus