title: Alignment of the lower extremity mechanical axis by computer-aided design and application in total knee arthroplasty.
abstract: OBJECTIVE
  The success of total knee arthroplasty (TKA) depends on many factors. The position of a prosthesis is vitally important. The purpose of the present study was to evaluate the value of a computer-aided establishing lower extremity mechanical axis in TKA using digital technology.
  
  
  METHODS
  A total of 36 cases of patients with TKA were randomly divided into the computer-aided design of navigation template group (NT) and conventional intramedullary positioning group (CIP). Three-dimensional (3D) CT scanning images of the hip, knee, and ankle were obtained in NT group. X-ray images and CT scans were transferred into the 3D reconstruction software. A 3D bone model of the hip, knee, ankle, as well as the modified loading, was reconstructed and saved in a stereolithographic format. In the 3D reconstruction model, the mechanical axis of the lower limb was determined, and the navigational templates produced an accurate model using a rapid prototyping technique. The THA in CIP group was performed according to a routine operation. CT scans were performed postoperatively to evaluate the accuracy of the two TKA methods.
  
  
  RESULTS
  The averaged operative time of the NT group procedures was [Formula: see text] min shorter than those of the conventional procedures ([Formula: see text]  min). The coronal femoral angle, coronal tibial angle, posterior tibial slope were [Formula: see text], [Formula: see text], [Formula: see text] in NT group and [Formula: see text], [Formula: see text], [Formula: see text] in CIP group, respectively. Statistically significant group differences were found.
  
  
  CONCLUSIONS
  The navigation template produced through mechanical axis of lower extremity may provide a relative accurate and simple method for TKA.
authors.affiliation: Department of Orthopaedics, The Affiliated Hospital of Inner Mongolia Medical University, Hohhot, People's Republic of China. dryzzhang@163.com.
authors.forename: Yuan Z
authors.initials: YZ
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedics, Kunming General Hospital, PLA, Kunming, People's Republic of China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Lu
authors.affiliation: Department of Special Diagnosis, Inner Mongolia Unit hospital of Chinese Armed Police Force, Hohhot, People's Republic of China.
authors.forename: Hui Q
authors.initials: HQ
authors.lastname: Zhang
authors.affiliation: School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, People's Republic of China.
authors.forename: Zhong M
authors.initials: ZM
authors.lastname: Jin
authors.affiliation: Department of Orthopaedics, The Affiliated Hospital of Inner Mongolia Medical University, Hohhot, People's Republic of China.
authors.forename: Jian M
authors.initials: JM
authors.lastname: Zhao
authors.affiliation: Department of Joint surgery, The Second Affiliated Hospital of Inner Mongolia Medical University, Hohhot, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Joint surgery, The Second Affiliated Hospital of Inner Mongolia Medical University, Hohhot, People's Republic of China.
authors.forename: Zhi F
authors.initials: ZF
authors.lastname: Zhang
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000000981:diagnostic imaging; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017076:Computer-Aided Design; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D035002:Lower Extremity / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D017755:Prosthesis Fitting / Q000379:methods*; D011859:Radiography; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods; D016474:Weight-Bearing
keywords: Anatomic; Imaging; Knee; Three-dimensional