Radiostereometric analysis in measurements of migration and inducible micromotion in intra-articular distal radius fractures treated with a volar plate.

OBJECTIVES

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.

DESIGN

Prospective cohort study.

SETTING

University hospital.

PATIENTS: Fifteen patients between 39 and 67 years of age with OTA type C distal radius fractures.

INTERVENTION: 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.

MAIN OUTCOME MEASUREMENTS: 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.

LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.