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Session: Poster session II
Session starts: Thursday 24 January, 16:00

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H.H. Rachmat (Department of Biomedical Engineering, University of Groningen, University Medical Center Groningen, The Netherlands)
Dennis Janssen (Orthopaedic Research Lab., Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands)
W.J. Zevenbergen (Department of Biomechanical Engineering, University of Twente, Enschede, The Netherlands)
Bart Verkerke (Rehabilitation Medicine, University of Groningen, University Medical Center Groningen, The Netherlands)
R.L. Diercks (Orthopaedics, University of Groningen, University Medical Center Groningen, The Netherlands)
Nico Verdonschot (Orthopaedic Research Lab., Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands)

Abstract:
Computational models of the human knee need information on the attachment sites of the knee ligaments, which play an important role in the knee kinematics studies. These attachment sites usually are determined based on MRI scans, guided by anatomical atlas. It is, however, unknown how accurate one is able to determine the actual insertion and origo, which may have a substantial effect on the predicted knee kinematics. In this study, we therefore evaluated the intra- and inter- observer variability when determining the knee ligaments attachment site positions on MRI scans. These MRI measurements were compared with actual physical measurements on the cadaver knee. A right knee of a 66 years old male donor was scanned in 3T MRI scan (pixel size of 0.5x0.5mm, slice thickness 0.5mm). The MRI measurements were performed by five observers, with various backgrounds (senior and junior scientific researcher, orthopaedic surgeon, orthopaedic resident), using image processing software (Mimics 14). Prior to the measurements, the observers received a short introduction to the software and were given an anatomical atlas as a guide. The observers were free to choose in which plane they measured the ligament attachment sites (sagital-coronal-transversal). We evaluated the difference in location and size of the area of the ligament attachment sites. One observer repeated the measurements 3 times, with a one week interval. We furthermore investigated the differences relative to the physical measurements, which were performed on the same cadaver, using 3Space Fastrak (Polhemus). The largest intra- and inter-observer differences were 4.3 mm (ACL origin) and 17.3 mm (superficial MCL insertion), respectively. Relative to the physical measurement, the maximum intra- and inter-observer differences were 32.6 mm (superficial MCL insertion) and 22.4 mm (deep MCL insertion), respectively. The largest area was measured for the ACL origin (73± 46mm2), while the smallest area was found for the MCL origin (13.8± 9mm2). This study demonstrates the difficulty of clearly identifying knee ligament attachments based on MRI data, which can have serious implications for computational models of the human knee.