title: Geometrical analysis results of 42 resurfacing shoulder prostheses: A CT scan study.
abstract: BACKGROUND
  Shoulder resurfacing arthroplasty was introduced in Scandinavia in the early 1980s then developed by SA Copeland.
  
  
  OBJECTIVE
  Resurfacing prostheses restore the normal anatomy of the proximal humerus. Here, our objective was to evaluate humeral resurfacing prosthesis position on radiographs and computed tomography (CT) images.
  
  
  METHODS
  We retrospectively reviewed 42 consecutive cases seen at a single centre between 2004 and 2009. Mean patient age was 65 years. CT was performed routinely before prosthesis implantation and at re-evaluation. The Copeland Mark III(®) (Biomet France SARL, 26903 Valence, France) implant was used in 32 cases and the Aequalis Resurfacing Head(®) (Tornier France, 38334 Saint-Ismier, France) in 10 cases. The post-implantation CT images were used to measure the angle of inclination, medial humeral offset, lateral glenohumeral offset, and version of the implant.
  
  
  RESULTS
  Mean follow-up was 18 months. Compared to baseline, no significant changes were found at re-evaluation for the angle of inclination or lateral glenohumeral offset. In contrast, medial humeral offset increased by 3.47mm, and excessive anteversion of 4.23° compared to the bicondylar line was noted.
  
  
  CONCLUSIONS
  Humeral head resurfacing prostheses restore the overall anatomy of the proximal humeral head. Our CT scan evaluation protocol seems reproducible and enables an evaluation of implant geometry. In our experience, resurfacing arthroplasty restored the native humeral offset. Inadequate retroversion was noted and was probably related to insufficient exposure during surgery.
  
  
  METHODS
  Level IV, retrospective study.
authors.affiliation: Department of Orthopaedic Surgery A, Lille University Regional Hospital Center, R.-Salengro Hospital, rue Emile-Laine, 59037 Lille cedex, France. jean-yves.deladerriere@wanadoo.fr
authors.forename: J-Y
authors.initials: JY
authors.lastname: Deladerrière
authors.forename: C
authors.initials: C
authors.lastname: Szymanski
authors.forename: T
authors.initials: T
authors.lastname: Vervoort
authors.forename: J-F
authors.initials: JF
authors.lastname: Budzik
authors.forename: C
authors.initials: C
authors.lastname: Maynou
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019643:Arthroplasty, Replacement; D005260:Female; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008433:Mathematics / Q000379:methods*; D008875:Middle Aged; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000601:surgery*; D019736:Prostheses and Implants; D011474:Prosthesis Design; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed / Q000379:methods*