title: Optimizing intramedullary entry location on the proximal humerus based on variations of neck-shaft angle.
abstract: BACKGROUND
  The purpose of this study was to define the relationship between the humeral neck-shaft angle (NSA) and variations in the ideal entry portal aligned with the long axis of the intramedullary canal of the proximal humerus.
  
  
  METHODS
  Three-dimensional images of 36 cadaveric humeri with various NSAs were reconstructed by a computerized surgical simulation program. The anteroposterior, mediolateral, and linear distances between a line from the center of the proximal medullary canal to the bicipital groove were measured. Differences among humeri with various NSAs were analyzed.
  
  
  RESULTS
  The intramedullary axis line was located a mean of 9 ± 2 mm posteriorly and 11 ± 3 mm medially from the bicipital groove. The axis line was 9 ± 2 mm posterior and 11 ± 2 mm medial with a standard NSA. The axis line in humeri with a varus NSA was 8 ± 2 mm posteriorly and 9 ± 2 mm medially, whereas the axis line was 10 ± 3 mm posteriorly and 14 ± 3 mm medially with a valgus NSA. The differences in the mediolateral distances between the groups were significant (P < .00009).
  
  
  CONCLUSIONS
  Care should be taken in choosing the entry portal position in humeri with various NSAs as the entry portal position differs according to the NSA. It is recommended that the location of the entry portal be moved toward the center of the humeral head to align with the centerline of the intramedullary canal in humeri with a valgus NSA in particular.
authors.affiliation: Department of Orthopaedic Surgery, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, South Korea. Electronic address: osjeong@hotmail.com.
authors.forename: Jinyoung
authors.initials: J
authors.lastname: Jeong
authors.affiliation: Department of Orthopaedic Surgery, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, South Korea.
authors.forename: Hyun-Woo
authors.initials: HW
authors.lastname: Jung
mesh_terms: D000328:Adult; D000368:Aged; D001178:Arthroplasty; D001837:Body Weights and Measures; D002102:Cadaver; D003198:Computer Simulation; D005260:Female; D005594:Fracture Fixation, Intramedullary; D006801:Humans; D058430:Humeral Head / Q000000981:diagnostic imaging / Q000601:surgery; D006811:Humerus / Q000000981:diagnostic imaging* / Q000601:surgery*; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D011859:Radiography; D025321:Surgery, Computer-Assisted
keywords: 3-dimensional; Proximal humerus; cadaveric study; intramedullary prosthesis; neck-shaft angle; portal of entry