title: Radiostereometric analysis in measurements of migration and inducible micromotion in intra-articular distal radius fractures treated with a volar plate.
abstract: OBJECTIVE
  This study examined the use of radiostereometric analysis (RSA) in the assessment of fixation stability and healing characteristics in intra-articular fractures of the distal radius treated with a volar locking plate.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Fifteen patients between 39 and 67 years of age with OTA type C distal radius fractures.
  
  
  METHODS
  All fractures were treated with a locked volar plate, and tantalum markers were inserted into fracture fragments. RSA was performed at 2, 6, 12, 18, and 52 weeks postoperatively. RSA measurements were also performed using maximal voluntary grip to create inducible micromotion at the fracture site at 6, 12, 18, and 52 weeks.
  
  
  METHODS
  Interfragmentary migration and inducible micromotion in terms of translation and rotation in 3 orthogonal axes were determined. The total translation and rotation were also calculated.
  
  
  RESULTS
  Precision of measurements along individual axes was between 0.08 and 0.17 mm and 0.70-0.94 degrees for migration and between 0.04 and 0.07 mm and 0.29 and 0.86 degrees for inducible micromotion. Fractures underwent significant translational and rotational migration (P = 0.004 for both) during the first 2 weeks after surgery. This permanent migration was not detectable on conventional radiographs. Inducible fracture micromotion, measured during maximal grip, was detectable up to 18 weeks, even after achievement of radiographic union.
  
  
  CONCLUSIONS
  RSA seems to have the potential to be a unique tool in redefining the biologic progress of fracture union. In plated fractures of the distal radius, the method is technically challenging due to difficulties in achieving a good scatter and visibility of tantalum RSA markers.
  
  
  METHODS
  Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Orthopaedic Research Unit, Department of Orthopaedic Surgery and Traumatology, Turku University Hospital and University of Turku, Turku, Finland.
authors.forename: Rami
authors.initials: R
authors.lastname: Madanat
authors.forename: Niko
authors.initials: N
authors.lastname: Strandberg
authors.forename: Niko
authors.initials: N
authors.lastname: Moritz
authors.forename: Kimmo
authors.initials: K
authors.lastname: Mattila
authors.forename: Tero
authors.initials: T
authors.lastname: Vahlberg
authors.forename: Hannu T
authors.initials: HT
authors.lastname: Aro
mesh_terms: D000328:Adult; D000368:Aged; D001860:Bone Plates; D005260:Female; D005593:Fracture Fixation, Internal; D017102:Fracture Healing; D006801:Humans; D057072:Intra-Articular Fractures / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009068:Movement; D011446:Prospective Studies; D059869:Radiostereometric Analysis; D011885:Radius Fractures / Q000503:physiopathology* / Q000601:surgery