title: Dorsal apex curve of the proximal ulna.
abstract: OBJECTIVE
  To analyze the apexes and angulations along the curvature in the posterior border of the proximal ulna-termed the "dorsal apex curve" (DAC)-using the computer-aided design software.
  
  
  METHODS
  Eight pairs of normal cadaveric ulnae were analyzed. The ulnar Cartesian coordinate system was standardized using a user-defined coordinate systems feature. DAC was defined by the best-fit curvature of serial apexes in the posterior border in axial cross-sections along the ulna, whereas the best-fit curvature was obtained using polynomials interpolation method. DAC apexes in three different planes were determined by calculating the second derivative value of curve function, and subsequently, DAC angulations were calculated. Statistical analysis was performed using analysis of variance with repeated measures with significance level set as 0.001.
  
  
  RESULTS
  The average ulnar length was 246±15 mm (224-274 mm). The average ratios of dorsal apex, varus apex, and edge point were 23±3% (17-27%), 33±4% (27-43%), and 10±1% (8-13%), respectively, relative to the ulnar length. The average amount of varus, dorsal, hook, and torsion angulation were 167±4° (157-172°), 176±1° (175-178°), 90±0°, and 31±10° (15-49°), respectively. We found no significant differences between left and right ulnae or between male and female ulnae.
  
  
  CONCLUSIONS
  Dorsal apexes and angulations are important landmarks for surgeons when applying plates and attempting total elbow replacement surgery. This curve provides valuable information to medical manufacturers for modeling both plates and ulna components of artificial elbow joints.
authors: Asan Medical Center, College of Medicine, University of Ulsan, Department of Orthopaedic Surgery, Seoul, Korea.
authors: Arnold
authors: A
authors: Adikrishna
authors: Sanggye Paik Hospital, Inje University, Department of Pediatrics, Seoul, Korea.
authors: Je Yeon
authors: JY
authors: Kim
authors: Asan Medical Center, College of Medicine, University of Ulsan, Department of Orthopaedic Surgery, Seoul, Korea.
authors: Aashay L
authors: AL
authors: Kekatpure
authors: Kyungpook National University Hospital, Department of Orthopedic Surgery, Daegu, Korea.
authors: Hyun Joo
authors: HJ
authors: Lee
authors: Asan Medical Center, College of Medicine, University of Ulsan, Department of Orthopaedic Surgery, Seoul, Korea.
authors: Minjae
authors: M
authors: Kim
authors: Asan Medical Center, College of Medicine, University of Ulsan, Department of Orthopaedic Surgery, Seoul, Korea.
authors: In Ho
authors: IH
authors: Jeon
mesh_terms: D001837:Body Weights and Measures / Q000379:methods*; D001860:Bone Plates; D061827:Dimensional Measurement Accuracy; D004867:Equipment Design / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014457:Ulna / Q000033:anatomy & histology / Q000473:pathology