Page 151 - DOS Kongressen 2012 - Abstracts

Assessment of precision in adult cadaver foot phantom model using
radiostereometric analysis
Peter Buxbom, Ragnhild í Skorini, Stig Sonne-Holm, Christian Wong
Department of Orthopaedic Surgery Hvidovre University Hospital;
Department of Orthopaedic Surgery, Hvidovre University Hospital;
Department of Orthopaedic Surgery, Hvidovre University Hospital;
Department of Orthopaedic Surgery, Hvidovre University Hospital
Radiostereometric analysis (RSA) has been used for years
particularly for identifying migration of prostheses. Its advantage is the ability
to identify complex movements with high accuracy. Prior to commencing a
new type of study a phantom validation of method is necessary assuring
accurate results.
Purpose / Aim of Study:
The aim of this study was to perform a phantom
study using standardized procedures on an adult cadaver foot after corrective
Materials and Methods:
Surgery of calcaneus lengthening and
subtaloartrodesis a.m. Grice was performed on an adult cadaver foot. 8
markers were inserted in calcaneus and 6 in talus. 3 RSA experiments with 10
examinations were then conducted: where neither phantom nor setup were
touched between examinations, where the phantom was repositioned in
between and where both setup and phantom were repositioned in between. The
translations and rotations (TR) were assessed with RSA as the precision in
each experiment; mean error of rigid body fitting (ME) was accepted if below
mm and mean condition numbers (MC) if below 150. As other RSA
studies, P-value was set at 0.01.
Findings / Results:
All markers were visible on each radiograph. ME were in
all 3 experiments below 0.09 mm and MC were all below 54. Comparisons of
TR of talus showed significant difference in 2 of 6 in the 3 axis. Precisions of
translation were all below 0.235 mm and rotation below 0.533 degrees.
Precision was not decreased when repositioning the phantom.
ME values of this study were below those typically obtained in
clinical settings, indicating an acceptable setup. Comparisons of TR mimick
movement of patients. Significant differences in two axis indicate the
importance of marker placement and procedure standardization, but since our
results were within limits in clinical settings, it seems reasonable to commence
our study.