title: Navigation system for robot-assisted intra-articular lower-limb fracture surgery.
abstract: OBJECTIVE
  In the surgical treatment for lower-leg intra-articular fractures, the fragments have to be positioned and aligned to reconstruct the fractured bone as precisely as possible, to allow the joint to function correctly again. Standard procedures use 2D radiographs to estimate the desired reduction position of bone fragments. However, optimal correction in a 3D space requires 3D imaging. This paper introduces a new navigation system that uses pre-operative planning based on 3D CT data and intra-operative 3D guidance to virtually reduce lower-limb intra-articular fractures. Physical reduction in the fractures is then performed by our robotic system based on the virtual reduction.
  
  
  METHODS
  3D models of bone fragments are segmented from CT scan. Fragments are pre-operatively visualized on the screen and virtually manipulated by the surgeon through a dedicated GUI to achieve the virtual reduction in the fracture. Intra-operatively, the actual position of the bone fragments is provided by an optical tracker enabling real-time 3D guidance. The motion commands for the robot connected to the bone fragment are generated, and the fracture physically reduced based on the surgeon's virtual reduction. To test the system, four femur models were fractured to obtain four different distal femur fracture types. Each one of them was subsequently reduced 20 times by a surgeon using our system.
  
  
  RESULTS
  The navigation system allowed an orthopaedic surgeon to virtually reduce the fracture with a maximum residual positioning error of [Formula: see text] (translational) and [Formula: see text] (rotational). Correspondent physical reductions resulted in an accuracy of 1.03 ± 0.2 mm and [Formula: see text], when the robot reduced the fracture.
  
  
  CONCLUSIONS
  Experimental outcome demonstrates the accuracy and effectiveness of the proposed navigation system, presenting a fracture reduction accuracy of about 1 mm and [Formula: see text], and meeting the clinical requirements for distal femur fracture reduction procedures.
authors.affiliation: Bristol Robotics Laboratory, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK. giulio.dagnino@uwe.ac.uk.
authors.forename: Giulio
authors.initials: G
authors.lastname: Dagnino
authors.affiliation: Bristol Robotics Laboratory, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Georgilas
authors.affiliation: Bristol Robotics Laboratory, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Köhler
authors.affiliation: Bristol Robotics Laboratory, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
authors.forename: Samir
authors.initials: S
authors.lastname: Morad
authors.affiliation: Bristol Royal Infirmary, Upper Maudlin Street, Bristol, BS2 8HW, UK.
authors.forename: Roger
authors.initials: R
authors.lastname: Atkins
authors.affiliation: Bristol Robotics Laboratory, University of the West of England, Coldharbour Lane, Bristol, BS16 1QY, UK.
authors.forename: Sanja
authors.initials: S
authors.lastname: Dogramadzi
mesh_terms: D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000379:methods; D050723:Fractures, Bone / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D057072:Intra-Articular Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D000070799:Open Fracture Reduction / Q000379:methods*; D011859:Radiography; D065287:Robotic Surgical Procedures / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: 3D medical imaging; Computer-assisted surgery; Fracture reduction planning; Fracture surgery; Image guidance; Medical robotics