Radiostereometric analysis at Biomatlab

Radiostereometric Analysis (RSA)

RSA X-ray of a Persona TKA
X-ray showing a Persona TKA implant (Zimmer Biomet) with tantalum bead markers, necessary for the RSA measurement of migration and rotation
Sindre Zachariassen (copyright owner, KiH) on behalf of Irene O. Moldestad for Biomatlab-Helse Bergen

Main content

Biomatlab is responsible for the analysis of x-rays in several clinical trials of hip- and knee prostheses, using Radiostereometric Analysis (RSA).

  • The Persona vs. NextGen RSA knee-study is underway at Kysthopitalet i Hagevik and at Sjukehuset i Lærdal (project started 2017).
  • Total hip replacements study: RSA and DXA 60 patients with Polar-stems versus Corail-stems. A randomized clinical trial with five year follow-up. Organised by Orthopedic clinic at Haukeland University Hosptal (project started 2016)
  • A comparative randomized study of 5 articulations in total hip replacements - 10 years of follow up with RSA, metal ion levels in blood, CT and MRI scans. Organised by Orthopedic clinic at Haukeland University Hosptal

The software we use is UmRSA from RSA Biomedical (Umeå). 

About the method:

•RSA is a highly accurate and precise method of evaluating e.g. implant migration and polyethylene wear.

•The precision usually is about 0.1mm (translational migration) and 0.1 degrees (rotation). 

•Postoperatively, two simultaneous exposures of the knee and a co-ordinate system are taken. This pair of x-rays allow 3D-definition of the implant and bone relative to the co-ordinate system. Implant migration and rotation are measured on repeat examinations over time.