Track 3. Musculoskeletal systems and Performance-Joint ISB/ESB

5313 Mo-Tu, no. 7 (P57) Relationship between femoro-tibial and femoro-patellar 3D kinematics in patients with patellar lateralisation E. BrQhl 1 , H. Graichen 2, S. Hinterwimmer 3, M. Siebert 4, T. Vogl 5, R. von Eisenhart-Rothe 1 . 1Research Group for Kinematics and Biomechanics, Department of Orthopedic Surgery, University of Frankfurt, Germany, 2Asklepios Orthop#dische Klinik Lindenlohe, Schwandorf, Germany, 3Department of Surgery, Ludwig-Maximilians-Universit~t, M~nchen, Germany, 4Institute for Medical Informatics, GSF Neuherberg, Oberschleil3heim, Germany, 5Institute for Clinical and Interventional Radiology, University of Frankfurt, Germany

Introduction: The objective was to analyze (a) tibio- and patello-femoral 3D- kinematics in healthy volunteers and in patients with patellar lateralisation pre- and postoperatively and (b) whether changes in femoro-patellar kinematics correlate with alteration in femoro-tibial kinematics. Materials and Methods: The knees of 20 healthy volunteers and of 10 patients with patellar lateralisation (20-44y.) were investigated preoperatively and one year after lateral release. Kinematics analysis was performed in an open MR system (0.2-T) at different flexion angles with external loads being applied. 3D kinematics of the patello-femoral and tibio-femoral joints were analyzed by three-dimensional image postprocessing. The coefficient of correlation (r) between both parameters was determined using the correlation z-test. Results: Regarding femoro-tibial kinematics, in the patients a significant increased external rotation of the femur relative to the tibia was observed preoperatively (0°: 14.1 ±2.30 vs. healthy 5.4±3.6°; p<0.01). Due to this changes the lateral femur condyle was positioned significantly posterior (30°: 7.6 ± 2.3 mm vs. healthy: 3.0 ± 1.8 mm). No significant changes were observed between the pre- and postoperatively data. Preoperatively at 900 of flexion the patellar tilt (20.7 ± 5.80 vs. healthy: 4.6 ± 3.1°) and shift (6.1 ± 3.8 mm vs. healthy: 3.6 ± 3.2 mm) were increased significantly in the patients. Postopera- tively the patellar shift (90°: 3.7 ± 4.5 mm) and tilt (90°: 13.8 ± 4.3 °) decreased significantly, the latter still being significantly increased compared to the healthy knees. The correlation between femoral rotation and patellar tilt was high in 0 ° (r= 0.72) and 900 (r= 0.65) of flexion. Conclusions: Patients with patellar lateralisation demonstrated considerable differences in femoro-tibial and femoro-patellar kinematics. The high correlation between both parameters suggests, that the altered femoro-tibial kinematics is relevant for the patellar disorders and should therefore be considered in therapy.

5952 Mo-Tu, no. 8 (P57) Personalized finite element model of the knee joint in vivo M. Sangeux 1 , E Marin 1 , F. Charleux 2, L. DLirselen 3, M.-C. Ho Ba Thoa. 1Laboratoire de Biom~canique et G~nie Biom6dical, UMR CNRS-UTC 6600, Compiegne, France, 2Centre d'imagerie avanc6 de Compiegne, Compiegne, France, 31nstitut fE/r Unfallchirurgische Forschung und Biomechanik of UIm, UIm, Germany

The knee is a complex joint with various pathologies or injuries subjected to high mechanical conditions. As these pathologies highly depend on each patient the objective of the present study was to develop a procedure to build in vivo personalized knee finite element models. All the geometrical acquisitions of the inner structures of the knee were obtained from MRI images in order to get in vivo models non-invasively. First the kinematics of one subject's knee was acquired thanks to a dedicated MRI protocol. The continuous movement of the knee was assessed from a finite set of 4 knee positions in the range of 0 to 900 of flexion. This kinematics was then introduced in the finite element model of the knee. The finite element model was composed of the bones, the cruciate and lateral ligaments, the cartilage and the menisci. The mesh was built with the MSC. Patran algorithm. The material properties of the soft tissues were derived from the literature and the bones were considered as rigid. The model integrate the contact between bones/cartilage and ligaments, cartilage/cartilage, carti- lage/menisci and ligaments/ligament. The procedure employed show that even with the very actual tools employed in this study a lot of human manual skills and actions are still needed to built such mechanical models. The finite element model results show the evolution of the pressure distribution on the cartilage and the menisci during the movement.

5180 Mo-Tu, no. 9 (P57) Dynamics stability in landing with ACL deficient knee joint M. Kasovi~ 1 , V. Medved 1 , M. Cifrek 2, M. Mejov,~ek 1 . 1Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia, 2Faculty of Electrical Engineering and Computing, University of Zagreb, Zagreb, Croatia

The purpose of this research was to determine the effect of the controlled landing tests in dynamics stabilities of ACL deficient knee pre- and post

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reconstruction. The test protocol included experimental and control groups. The experimental group included examines with ACL deficient knee while control group consisted of healthy examines. The protocol consisted of fol- lowing testing phases: (1) testing of the knee joint muscle power (execution of the maximum voluntary contraction during which the myoelectric signals were collected) and (2) testing of the knee joint dynamic stability (execution of the test with one-legged (landings) from the 40cm and 20cm high bench, during which the kinematic and kinetic parameters were collected). Following variables were studied: kinematic (valgus and varus, inner and outer rotation and angle of the flexion and extension in the knee joint), ground reaction force and EMG signals of the four main muscle of lower extremity have been measured during execution of the maximum static contraction lasting for 10 seconds. The protocol consisted of two testing period time pre- and post reconstruction of ACL. Statistically significant difference between groups in the first measurement as well as between injured and healthy knee was observed. That was the case especially in kinematical parameters (in inner and outer rotation angle as well as valgus-varus movement). Generally, a change in landing dynamics of the injured knee was observed. The differences are reduced following the reconstruction, and that is especially the case in examinees that underwent proprioceptive treatment during rehabilitation. The test could be applicable as an indicator of readiness of athletes to sustain training workload as well as a predictor of injury occurrence in healthy people.

5864 Mo-Tu, no. 10 (P57) A movement index as proposal for an unified description in arthrokinematics

P. Klein. Universit~ Libre de Bruxelles (URTM), Brussels, Belgium

In arthrokinematics, where movements between joint surfaces are described, a wide terminology is used: rolling, gliding, sliding, spinning, translation, translational gliding, and much more. Such a terminology is purely descriptive and does not consider parameters like the curvature of joint surfaces. Based on the localization of the center of rotation (CR), the center of curvature (CC) and the mean contact point (CP), we propose for plane motion a movement index /MOV = ICR-CPI/ICC-CPI • The distance CC-CP represents the local radius of curvature of the convex surface. This gives: (1)/MOV =0 with pure rolling and CR located at CC; (2)/MOV = 1 with pure gliding and CR located on CC. (3) 0 </MOV < 1, a combination of rolling and gliding occurs and finally if/MOV > 1, rotation is combined with translation. Theoretically, when /MOV ='~', pure translation occurs. However in a clinical environment, one can consider that translation occurs if/MOV > 10. In this case, observing radiographs with the nude eye, it becomes difficult to distinguish rotation from translation. When 0</MO V < 1 (case 3), for instance /MOV =0.7, indicates that 70% of the rotation are gliding and 30% are rolling. In literature, rolling is often defined when CP migrates the same distance on both joint surfaces. If CP is stationary on one surface the motion is called gliding. It is our feeling that /MOV avoids unclear fuzzy terminology and by considering the local radius of curvature contains more information. Moreover, /MOV describes at every moment the ratio of rolling and gliding. Considering for instance the knee joint, one can immediately get inside in the variation of this ratio during flexion. The index will be slightly different in the lateral and the medial compartment accounting for the axial 'automatic' rotation during the first degrees of flexion.

7494 Mo-Tu, no. 11 (P57) A mobi le axis knee joint model for gait analysis applications E.E. Pavan, P. Taboga, C. Frigo. TBM Lab, Laboratory of Movement Biomechanics and Motor Control, Department of Bioengineering, Polytechnic of Milan, Milan, Italy

In almost all the existing protocols for gait analysis the knee joint flex- ion/extension axis is defined as the axis that passes through the medial and lateral femoral epicondyles, and is identified by markers attached to the skin. This axis is considered fixed in relation to the femur, and thus it cannot reproduce the complex combination of rotational and translational movements that occur between distal femur and tibia plateau. In addition the wide skin deformation which occurs at the knee area, can affect very erratically the flexion/extension angle. In the present work a planar model of the knee joint in which femur and tibia were constrained by length-variable cruciate ligaments was included in a three dimensional model of the lower limb. The position and orientation of the cruciate ligaments were defined on the basis of an integrated analysis of NMR and Fluoroscopic imaging. From these data a lookup table was implemented containing the cruciate ligaments length changes as a function of femur and tibia relative angles in the sagittal plane. Kinematic data from a gait analysis session were used to animate the model and to compute the relevant kinematic variables. Data obtained by a single axis knee model and by the new, mobile axis model were compared, and differences up to 8 deg in flexion/extension joint angle were obtained.