Biomechanical Study on the Novel Biomimetic Hemi-Pelvis Prosthesis

A pelvic endoprosthesis is the primary means of pelvic reconstruction after internal hemipelvectomy. In this study, a novel biomimetic hemipelvic prosthesis, including an artificial ilium, an artificial acetabulum, and an artificial pubis, was developed. A Finite Element Method （FEM） was carried out to investigate the biomechanical performance of a pelvis reconstructed with biomimetic hemipelvic prosthesis. Two models, including the reconstructed pelvis and the original pelvis （control model）, were established according to the geometry from CT data of a human male patient with pelvic bone sarcomas. The FE models predict that the biomeehanical function of the pelvic ring can be reestablished using this prosthesis. Results show that the body force loaded on the S 1 vertebra is restored and transferred towards the sacro-iliac joint, and along the ilium onto the bearing surface of the artificial ilium, then to the artificial acetabulum and pubis. Von Mises stresses observed in this reconstructed pelvis model are still within a low and elastic range below the yielding strength of cortical bone and Ti6A14V. The values of deformation and strain of the reconstructed pelvis are close to the data obtained in the original pelvis. With the partial replacement of the pubis, little influence is found towards the pubis symphysis. However, the interface between the prosthesis and pelvic bone may become the critical part of the reconstructed pelvis due to the discontinuity in the material properties, which results in stress shielding and deformation constraining. So a biomimetic flexible connection or inter layer to release the deformation of pelvis is suggested in future designing.

Elastohydrodynamic lubrication and wear modelling of the knee joint replacements with surface topography

This numerical study predicted wear of lubricated total knee replacements with the existing of textured surfaceand the possibility of surface designs to reduce wear.In the first part,a wear model of metal-on-polyethylene total kneereplacement was developed.The medial and lateral knee compartments was accounted for separately,with the contactforce and motion during walking cycles applied.An adapted Archard wear formula was employed where the wearfactor was an exponential function of the'Lambda ratio'(film thickness to the average roughness).Wear of the softbearing surface(polyethylene insert)was simulated with regularly geometry update until a steady-state wear observed.ln the second part,the effect of surface topography of the knee replacements was investigated.The surface texturingtechniques have shown promising benefit to machine components in many areas of engineering practice.The textureparameters were designed using the Taguchi method for the geometry,size,and distribution of the micro dimples.twas observed that the lateral compartment may benefit from surface texturing if dimples were properly designed,while the texturing showed hardly advantageous effect on the medial surface in terms of lubrication enhancement andwear reduction.Some results were presented in the 6th World Tribology Conference.