title: Numerical optimization of alignment reproducibility for customizable surgical guides.
abstract: OBJECTIVE
  Computer-assisted orthopedic surgery aims at minimizing invasiveness, postoperative pain, and morbidity with computer-assisted preoperative planning and intra-operative guidance techniques, of which camera-based navigation and patient-specific templates (PST) are the most common. PSTs are one-time templates that guide the surgeon initially in cutting slits or drilling holes. This method can be extended to reusable and customizable surgical guides (CSG), which can be adapted to the patients' bone. Determining the right set of CSG input parameters by hand is a challenging task, given the vast amount of input parameter combinations and the complex physical interaction between the PST/CSG and the bone.
  
  
  METHODS
  This paper introduces a novel algorithm to solve the problem of choosing the right set of input parameters. Our approach predicts how well a CSG instance is able to reproduce the planned alignment based on a physical simulation and uses a genetic optimization algorithm to determine optimal configurations. We validate our technique with a prototype of a pin-based CSG and nine rapid prototyped distal femora.
  
  
  RESULTS
  The proposed optimization technique has been compared to manual optimization by experts, as well as participants with domain experience. Using the optimization technique, the alignment errors remained within practical boundaries of 1.2 mm translation and [Formula: see text] rotation error. In all cases, the proposed method outperformed manual optimization.
  
  
  CONCLUSIONS
  Manually optimizing CSG parameters turns out to be a counterintuitive task. Even after training, subjects with and without anatomical background fail in choosing appropriate CSG configurations. Our optimization algorithm ensures that the CSG is configured correctly, and we could demonstrate that the intended alignment of the CSG is accurately reproduced on all tested bone geometries.
authors: Computer Graphics and Visualization Group, Department of Intelligent Systems, Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands. t.kroes@tudelft.nl.
authors: Thomas
authors: T
authors: Kroes
authors: Department of BioMechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, The Netherlands.|Biomechanics and Imaging Group, Department of Orthopaedics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.
authors: Edward
authors: E
authors: Valstar
authors: Computer Graphics and Visualization Group, Department of Intelligent Systems, Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands.
authors: Elmar
authors: E
authors: Eisemann
mesh_terms: D000465:Algorithms; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D008297:Male; D019637:Orthopedic Procedures / Q000379:methods*; D015203:Reproducibility of Results; D012399:Rotation; D025321:Surgery, Computer-Assisted / Q000379:methods*
keywords: Customizable surgical guide; Genetic optimization; Knee replacement surgery; Physical simulation; Surgical navigation device