title: A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface.
abstract: BACKGROUND
  The accuracy of reconstruction is thought to impact on functional outcome following glenohumeral joint arthroplasty. The objective of this study was to define an area of minimal anatomic variation at the cartilage/metaphyseal interface of the proximal humerus to optimize the osteotomy of the humeral head, enabling accurate reconstruction with a prosthetic component.
  
  
  METHODS
  Hand held digitization and 3D surface laser scanning techniques were used to digitize 24 cadaveric arms and determine the normal geometry. Each humeral head was then examined to identify the most consistent anatomical landmarks for the ideal osteotomy plane to optimize humeral component positioning.
  
  
  RESULTS
  The novel, posterior referencing, osteotomy resulted in a mean increase in retroversion of only 0.4° when compared to the original geometry. A traditional anterior referencing osteotomy, by comparison, produced a mean increase in retroversion of 11°. In addition, the novel osteotomy only increased axial diameter by 0.71mm and head height by 0.02mm compared to an anterior referencing osteotomy (3.0mm and 2.7mm respectively).
  
  
  CONCLUSIONS
  The traditional osteotomy, referencing the anterior border of the cartilage/metaphyseal interface potentially resulted in an increase in prosthetic head size and retroversion. The novel osteotomy, referencing from the posterior cartilage/metaphyseal interface enabled a more accurate recovery of head geometry. Importantly, the increase in retroversion created by the traditional osteotomy was not replicated with the novel technique. Referencing from the posterior cartilage/metaphyseal interface produced a more reliable osteotomy, more closely matching the original humeral geometry.
  
  
  METHODS
  Basic Science, Anatomic study, Computer model.
authors.affiliation: Department of Orthopaedic and Trauma Surgery, College of Medicine, Dentistry and Nursing, University of Dundee, TORT Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK. Electronic address: Fraserharrold@doctors.org.uk.
authors.forename: Fraser
authors.initials: F
authors.lastname: Harrold
authors.affiliation: Department of Orthopaedic and Trauma Surgery, College of Medicine, Dentistry and Nursing, University of Dundee, TORT Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK.
authors.forename: Amar
authors.initials: A
authors.lastname: Malhas
authors.affiliation: Department of Orthopaedic and Trauma Surgery, College of Medicine, Dentistry and Nursing, University of Dundee, TORT Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK.
authors.forename: Carlos
authors.initials: C
authors.lastname: Wigderowitz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000033:anatomy & histology*; D019643:Arthroplasty, Replacement / Q000379:methods*; D002102:Cadaver; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D058430:Humeral Head / Q000033:anatomy & histology* / Q000601:surgery; D007595:Joint Prosthesis; D008297:Male; D010027:Osteotomy / Q000379:methods*; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery*
keywords: Anatomy; Arthroplasty; Geometry; Humerus; Osteotomy; Shoulder