Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_

Poster
Topic: General Orthopaedics
Abstract number: 23363
SIMULTANEOUS MEASUREMENTS OF KNEE MOTION USING OPTICAL
TRACKING SYSTEM AND RADIO STEREOMETRIC ANALYSIS (RSA)
Roy TRANBERG, Tuuli SAARI, Roland ZÜGNER, Johan KÄRRHOLM
Department of Orthopaedics Institute of Clinical Sciences Sahlgrenska Academy
University of Gothenburg, Göteborg (SWEDEN)
Invasive methods are more reproducible and accurate than non-invasive to record
knee joint kinematics, but are usually less accessible and less safe. Therefore, noninvasive
methods with passive markers are widely used. With these methods varying
marker-sets based upon a number of single markers, or sets of markers, known as
clusters are used to track body segments. We compared one invasive method, radio
stereometric analysis, with a non-invasive method, an optical tracking system with 15
skin mounted markers. Nine subjects (ten knees) were investigated simultaneously
with a dynamic RSA system and a motion capture system while performing an active
knee extension. For flexion/extension there was good accordance on individual basis
as well as a group. For internal/external rotations the group mean was rather similar
up to 25 degrees of flexion. Recordings of abd-/adductions revealed a systematic
mean difference of 2-4° during the measured range o f flexion. Correlation between
the two methods in the horizontal and frontal planes was poor. Our skin marker
model provided reliable data for flexion/extension. Recordings of internal/external
rotation and abduction/adduction were less accurate on individual basis than on
group level, most likely due to soft tissue motions and presence of small true motions
in these planes.
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