title: Measurement of migration of a humeral head resurfacing prosthesis using radiostereometry without implant marking: an experimental study.
abstract: BACKGROUND
  Standard radiostereometric analysis of prosthetic migration requires that tantalum beads are inserted into the implant. For manufacturing reasons, this is not possible for humeral head resurfacing implants. We therefore used marker-free radiostereometry, developed for metal-backed acetabular cups, on a dummy model to validate the method for a humeral head resurfacing prosthesis.
  
  
  METHODS
  3 hemispherical resurfacing prostheses of different sizes were marked with tantalum beads and mounted in a sawbone. Standard and marker-free radiostereometry was then done repeatedly with gradual shifts of position of the prosthesis between each analysis. The marker-free algorithm was then compared to the standard to determine the accuracy.
  
  
  RESULTS
  The accuracy for marker-free radiostereometry was 0.22-0.47 mm for translations and 0.92-1.56 degrees for rotations.
  
  
  CONCLUSIONS
  Based on our results, marker-free radiostereometry can be used to measure migration of humeral head resurfacing prostheses. This indicates that implant marking is not required when doing radiostereometry on humeral head resurfacing in clinical trials.
authors.affiliation: Department of Clinical Sciences at Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden. olof.skoldenberg@ds.se
authors.forename: Olof
authors.initials: O
authors.lastname: Sköldenberg
authors.forename: Magnus
authors.initials: M
authors.lastname: Odquist
mesh_terms: D015502:Absorptiometry, Photon; D019643:Arthroplasty, Replacement / Q000009:adverse effects / Q000379:methods; D058430:Humeral Head; D007595:Joint Prosthesis / Q000009:adverse effects; D019047:Phantoms, Imaging; D011474:Prosthesis Design; D011475:Prosthesis Failure; D015203:Reproducibility of Results; D012399:Rotation; D013635:Tantalum
chemical_list: D013635:Tantalum