Abstract—The requirement of deep kneeling is common among Asians e.g. Seiza and kneeling during prayer. In this study, the sensitivity of stress in toral knee replacement (TKR) post to tibial rotation during deep flexion was analysed and its relation to design of post-cam articulation was investigated. Three dimensional (3D) finite element models of two designs of clinically used posterior stabilized (PS) type total knee arthroplasty were constructed using their computational aided drawing (CAD) data. Loaded deep flexional motion from 0 to 135 degree in neutral, 10° and 15° of tibial rotation was adapted using finite element model to characterize the effects of knee kinematics on the stress states of ultra-high molecular weight polyethylene (UHMWPE) tibial inserts and relation to post-cam design. Peak equivalent stresses in post at neutral, 10° and 15° tibial rotation were 65.22 MPa, 108.97 MPa and 134.50 MPa respectively, for Superflex, and 47.16 MPa, 45.69 MPa and 47.67 MPa respectively, for NRG. The result shows that the variation of maximum equivalent stress at different flexion angle and tibial rotation were caused by the post-cam contact geometry in sagittal plane and axial plane, respectively. Stress state of Superflex tibial post was found to be more sensitive to tibial rotation as compared to NRG. Modification on the post design based on post-cam radius of curvature ratio in both axial and sagittal has eliminated the sharp edge and provided larger contact area, hence reduce edge loading and high stress concentration area in Scorpio NRG. Stress in Scorpio NRG tibial post was found to be less sensitive to tibial rotation.

Index Terms—Deep flexion, finite element analysis, post-cam design, tibial rotation.

Interdisciplinary Graduate School of Engineering Sciences, Kyushu Univerisity, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan (email: ar-m-afzan@mms.kyushu-u.ac.jp).
Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan.
Sugioka Memorial Hospital, 3-6-1 Kashiiteruha, Higashi-ku, Fukuoka, 813-0017, Japan.
Faculty of Mechanical Engineering, 40450 Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia.

Cite: Mohd Afzan Mohd Anuar, Mitsugu Todo, Ryuji Nagamine, "Computational Model for Mechanics of Total Knee Replacement: Effect of Tibial Rotation during Deep Flexion in Relation to Post-Cam Design," International Journal of Bioscience, Biochemistry and Bioinformatics vol. 4, no. 6, pp. 428-437, 2014.