title: [Design and experimental study of computer-assisted orthopaedic system for distal locking of intramedullary nails].
abstract: OBJECTIVE
  To test the safety and accuracy of the computer-assisted orthopaedic system for distal locking of intramedullary nails and apply it to internal fixation with intramedullary nails in the lower limb.
  
  
  METHODS
  According to the theory of mechanical arms stereotactic localization in computer-assisted orthopaedic surgery (CAOS), we design a CAOS system for distal locking of intramedullary nails. The system comprised 2 independent modules: computer-assisted imaging and registration workstation; mechanical stereotactic framework. Ten plastic tibia models, 20 plastic femur models (Synbone AG, Malans, Switzerland) and 6 human cadaver lower limbs were randomly divided into 2 groups undergoing internal fixation with intramedullary nails (Orthofix, Germany). The first group (CAOS group with 5 plastic tibia models, 10 plastic femur models, 6 human cadaver tibia, 6 human cadaver femur; each nail had 2 holes, and 2 distal locking screws were inserted in each bone, which gave a total number of 54 holes) used a computer-assisted orthopaedic system, the second group (CONTROL GROUP is the same as CAOS group) used Orthofix mechanical targeting device for distal locking. Comparison between 2 groups was made in radiation exposure time, operating time, percentage of correctly placed screws.
  
  
  RESULTS
  CAOS group: operating time was (4.44 +/- 2.99) min; radiation exposure time was (1.16 +/- 0.38) min; correctly placed screws rate was (100 +/- 0)%.
  
  
  METHODS
  operating time was (10.42 +/- 4.18) min; radiation exposure time was (4.71 +/- 3.86) min; correctly placed screws rate was (94.44 +/- 0.36)%. Operating time and radiation exposure time in CAOS group were significantly shorter than those in control group (P < 0.05), no differences were found between 2 groups in relation to the percentage of correctly placed screws.
  
  
  CONCLUSIONS
  By using CAOS system for distal locking of intramedullary nails, the locking holes can be drilled accurately and safely. Radiation exposure significantly reduced.
authors.affiliation: Department of Orthopaedics and Traumatology, Jishuitan Hospital, Beijing 100035, China.
authors.forename: Jun-qiang
authors.initials: JQ
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Hu
authors.forename: Lei
authors.initials: L
authors.lastname: Sun
authors.forename: Wen-yong
authors.initials: WY
authors.lastname: Liu
authors.forename: Li-dan
authors.initials: LD
authors.lastname: Zhang
authors.forename: Tian-miao
authors.initials: TM
authors.lastname: Wang
authors.forename: Man-yi
authors.initials: MY
authors.lastname: Wang
mesh_terms: D002102:Cadaver; D004867:Equipment Design; D005269:Femur / Q000601:surgery; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D006801:Humans; D008953:Models, Anatomic; D011897:Random Allocation; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D013977:Tibia / Q000601:surgery