title: Improvement of femoral component size prediction using a C-arm intensifier guide and our established algorithm in unicompartmental knee arthroplasty: a report from a Chinese population.
abstract: BACKGROUND
  Unicompartmental knee arthroplasty (UKA) is becoming more widely used with the recent increase in popularity of the use of minimally invasive techniques. However, it is difficult to judge about the femoral component size in UKA using preoperative templating digitally or otherwise. Even when using navigation it is impossible to control the femoral component size. The aim of this study is to develop a better pre- or intra-operative measure that will predict femoral component size.
  
  
  METHODS
  Ninety-two UKA cases were studied from June 2007 to December 2011 with a mean 26-month follow-up. We developed an intra-operative C-arm intensifier guide (CAIG) method for determining femoral size instead of pre-operative templating. The accuracy of prediction of both methods was compared from a review of post-operative radiographs. In addition, we summarized all cases and developed a Chinese algorithm to determine the femoral component size pre-operatively.
  
  
  RESULTS
  There was a significant difference between templating (59%) and CAIG (92%) method (P=0.0001). In the Chinese algorithm, height based on gender and tibial size both have greater accuracy of prediction (88% and 70.7%) than the Oxford algorithm (51.1% and 59.8%). Component size distribution and optimal tibial/femoral pairing differed from those in the Oxford report.
  
  
  CONCLUSIONS
  We conclude that the Chinese algorithm can greatly improve the accuracy of prediction of femoral component size. In addition, CAIG-assisted implantation of a UKR is a reliable intra-operative tool and can aid size selection of the femoral component.
  
  
  METHODS
  Level III.
authors.affiliation: Department of Orthopedics, Yangpu District Central Hospital affiliated to Tongji University, 450 Teng Yue Road, Shanghai 200090, China.
authors.forename: Yihui
authors.initials: Y
authors.lastname: Tu
authors.affiliation: Department of Orthopedics, Yangpu District Central Hospital affiliated to Tongji University, 450 Teng Yue Road, Shanghai 200090, China. Electronic address: x11h22m33@126.com.
authors.forename: Huaming
authors.initials: H
authors.lastname: Xue
authors.affiliation: Department of Orthopedics, Yangpu District Central Hospital affiliated to Tongji University, 450 Teng Yue Road, Shanghai 200090, China.
authors.forename: Minwei
authors.initials: M
authors.lastname: Cai
authors.affiliation: Department of Orthopedics, Yangpu District Central Hospital affiliated to Tongji University, 450 Teng Yue Road, Shanghai 200090, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Ma
authors.affiliation: Department of Orthopedics, Yangpu District Central Hospital affiliated to Tongji University, 450 Teng Yue Road, Shanghai 200090, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Liu
authors.affiliation: Botnar Research Centre, Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences, Oxford University, NOC, Headington, Oxford OX3 7LD, UK.
authors.forename: Zhidao
authors.initials: Z
authors.lastname: Xia
mesh_terms: D000465:Algorithms; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D001827:Body Height; D002681:China; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging* / Q000601:surgery; D005471:Fluoroscopy; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery; D017755:Prosthesis Fitting / Q000295:instrumentation* / Q000379:methods*; D012737:Sex Factors; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery
keywords: C-arm intensifier guide; algorithm; femoral component size; unicompartmental knee arthroplasty