title: Digital templating in total knee and hip replacement: an analysis of planning accuracy.
abstract: OBJECTIVE
  The aim of this study was to determine how well pre-operative size selection for total knee and hip arthroplasties based on the digital imaging with and without additional referencing correlated with the size actually implanted.
  
  
  METHODS
  Size selection planning of total knee arthroplasty by digital templating was documented in 46 cases with reference ball (group A) and in 48 cases without ball (group B). In addition, prospective analysis of pre-operative planning was conducted for 52 acetabular components with reference ball (group C) and 69 without ball (group D) as well as stem planning in 38 cases with ball (group E) and 54 cases without ball (group F). The data were analysed and compared with the size of the final component selected during surgery.
  
  
  RESULTS
  The correlation between planned and implanted size for total knee arthroplasty in group A resulted in femoral anteroposterior (AP) r = 0.8622 and lateral r = 0.8333 and in group B AP r = 0.4552 and lateral r = 0.6950. Tibial in group A was AP r = 0.9030 and lateral r = 0.9074 and in group B AP r = 0.7000 and lateral r = 0.6376. For the acetabular components, the results in group C were r = 0.5998 and group D r = 0.6923. For stems, group E was r = 0.5306 and group F r = 0.5786. No correlation between BMI and the difference between planned and implanted size was found in any of the groups.
  
  
  CONCLUSIONS
  In the case of total hip arthroplasty there was a relatively low correlation between planned and implanted sizes with or without reference ball. For total knee arthroplasties the already high precision of size planning was further improved by the additional referencing with a reference ball.
authors.affiliation: Clinic for Orthopaedic and Trauma Surgery, Hospital Bad Cannstatt, Prießnitzweg 24, 70374, Stuttgart, Germany, knieselb@yahoo.com.
authors.forename: Bettina
authors.initials: B
authors.lastname: Kniesel
authors.forename: Lukas
authors.initials: L
authors.lastname: Konstantinidis
authors.forename: Anja
authors.initials: A
authors.lastname: Hirschmüller
authors.forename: Norbert
authors.initials: N
authors.lastname: Südkamp
authors.forename: Peter
authors.initials: P
authors.lastname: Helwig
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D015992:Body Mass Index; D006621:Hip Joint / Q000000981:diagnostic imaging; D006622:Hip Prosthesis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007720:Knee Prosthesis; D017755:Prosthesis Fitting; D011859:Radiography; D012984:Software