title: Assessment of inducible fracture micromotion in distal radial fractures using radiostereometry.
abstract: OBJECTIVE
  This study examined the potential for measuring dynamic inducible micromotion (DIMM) between fragments in healing distal radial fractures using radiostereometry (RSA).
  
  
  METHODS
  Prospective imaging study.
  
  
  METHODS
  University teaching hospital.
  
  
  METHODS
  Nine patients with low-impact distal radial fractures.
  
  
  METHODS
  Volar locked plating of the fracture with insertion of tantalum beads into bone fragments. RSA examinations at 1 day and then 2, 6, 26, and 52 weeks. Motion at the fracture site was induced by maximal voluntary hand grip using a Jamar dynamometer. Radiographs were analyzed using locally developed and UMRSA software.
  
  
  METHODS
  DIMM and migration were calculated as translations and rotations of the main distal segment. Clinical precision was assessed under repeatability conditions.
  
  
  RESULTS
  Precision (as 95% error limit) ranged from 0.06 to 0.13 mm and 0.5 to 0.8 degrees for migration, and from 0.10 to 0.14 mm and 0.6 to 1.0 degrees for DIMM. DIMM was characterized by axial and dorsal compression with dorsiflexion. The median DIMM of patients reached a maximum at 2 weeks: mainly as 0.3 mm axial compression, 0.3 mm dorsal compression, and 2.5 degrees dorsiflexion. DIMM ceased by 26 weeks, indicating union of all fractures. Fracture collapse continued until the 26-week measurement, ranging between 0.2 and 2.8 mm axially. Instability of some intraosseous markers was observed.
  
  
  CONCLUSIONS
  The precision of this RSA method was sufficient to observe inducible movements occurring during fracture healing. This has the potential for quantifying rates of fracture union and improving understanding of the available treatments.
authors.affiliation: Orthopaedic Research Unit, Woodend Hospital, Aberdeen AB15 6XS, Scotland. m.downing@abdn.ac.uk
authors.forename: Martin R
authors.initials: MR
authors.lastname: Downing
authors.forename: P Blair
authors.initials: PB
authors.lastname: Ashcroft
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Johnstone
authors.forename: Olaf
authors.initials: O
authors.lastname: Bach
authors.forename: Suzi
authors.initials: S
authors.lastname: Mackenzie
authors.forename: G Patrick
authors.initials: GP
authors.lastname: Ashcroft