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· DOS Abstracts
Digitally reconstructed radiograph based
radiostereometric analysis: A novel method
validated on the hip joint
Sepp De Raedt, Lars Hansen, Peter Bo Jørgensen, Bjarne Mygind-Klavsen,
Maiken Stilling
Research and development, Nordisk Røntgen Teknik; Orthopedic Research
Unit, Department of Clinical Medicine, Aarhus University Hospital; Orthopedic
Research Unit, Department of Clinical Medicine, Aarhus University Hospital;
Department of Orthopedic Surgery, Aarhus University Hospital; Orthopedic
Research Unit, Department of Clinical Medicine, Aarhus University Hospital
Background:
Dynamic radiostereometric analysis (dRSA) can track 3D in-vivo
movements of bones or implants, but analysis is time consuming. Current mark-
er based RSA (MM) requires bone markers to be inserted and traditional model
based RSA (MBM) requires models to be manually matched on each radiograph.
We propose a novel digitally reconstructed radiograph based method (DRR) for
automated analysis of RSA recordings of the hip joint.
Purpose / Aim of Study:
To evaluate precision of DRR compared with MBM
(MM as gold standard).
Materials and Methods:
Seven human cadaveric hips were CT- scanned and
preprocessed for analysis. Tantalum beads were inserted in the femur and pelvis.
dRSA images were acquired at 5 fr/sec during flexion, adduction and internal
rotation. All images were analyzed by DRR, MBM and MM. Migrations were
calculated with respect to MM in 6 degrees of freedom. Precision was assessed
as systematic bias (mean difference) and random variation (Pitman’s test) with
respect to MM as gold standard.
Findings / Results:
In total 288 dRSA images were analyzed. Systematic bias
for MBM and DRR with respect to MM in translations (Δ<0.018mm) and rota-
tions (Δ<0.009°) were approximately zero and no difference between MBM
and DRR (p>0.46) was found. Random variation was lower (p<0.00) in all de-
grees of freedom for DRR compared to MBM. For the femur translations DRR
had 40% better (Δ0.07mm) precision, and for femur rotations DDR precision
was 60% better (Δ0.25°) compared to MBM. For the pelvis translations DRR
had 6 fold better (Δ0.40mm) precision, and for pelvis rotations DDR had 2 fold
better precision (Δ0.34°) compared to MBM.
Conclusions:
DRR is a novel method for analysis of dRSA and can be used clini-
cally for kinematic based diagnostic studies. It is automated, noninvasive, not
user-dependent and more precise in comparison with MBM for analysis of the
hip joint.
No conflicts of interest reported
137.