title: Analysis of the micro-migration of sliding hip screws by using point-based registration.
abstract: OBJECTIVE
  The favored treatment for many hip fractures is a sliding hip screw, and its usage is expected to increase in the future. Failures can be reduced, and complications detected earlier by semi-automated CT image analysis. The most frequent failure is due to the screw cut-out from the femoral head.
  
  
  METHODS
  An image-based method was developed for early detection of complications and assessment of anchorage quality relative to implant model, bone quality or tip-apex distance (TAD). This method evaluates micro-migration using CT images acquired at different time points (immediately post-op and 3-month later). Serial CT image registration and transformation methods were applied, including point-based registration, to achieve semi-automated evaluations.
  
  
  RESULTS
  Qualitative and quantitative validation of the image registration was performed with measurement mean error determination by different observers. The micro-migration evaluation by clinicians compared favorably with semi-automated image-based results.
  
  
  CONCLUSIONS
  Semi-automatic evaluation of hip screw micro-migration using CT images is feasible and can aid observation of convalescence. The method may be amenable to full automation, a future goal for this work.
authors.affiliation: Institute for Biomedical Image Analysis, University for Health Informatics and Technology Tyrol, Hall in Tyrol, Austria. patrik.raudaschl@umit.at
authors.forename: Patrik
authors.initials: P
authors.lastname: Raudaschl
authors.forename: Karl
authors.initials: K
authors.lastname: Fritscher
authors.forename: Tobias
authors.initials: T
authors.lastname: Roth
authors.forename: Christian
authors.initials: C
authors.lastname: Kammerlander
authors.forename: Rainer
authors.initials: R
authors.lastname: Schubert
mesh_terms: D001863:Bone Screws / Q000009:adverse effects*; D003937:Diagnosis, Differential; D005548:Foreign-Body Migration / Q000175:diagnosis*; D005593:Fracture Fixation, Internal / Q000009:adverse effects / Q000295:instrumentation*; D006620:Hip Fractures / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D011475:Prosthesis Failure; D014057:Tomography, X-Ray Computed / Q000379:methods*