Real-time simulation of soft tissue deformation for surgical simulation

Surgical simulation plays an important role in the training, planning and evaluation of many surgical procedures. It requires realistic and real-time simulation of soft tissue deformation under interaction with surgical tools. However, it is challenging to satisfy both of these conflicting requirements. On one hand, biological soft tissues are complex in terms of material compositions, structural formations, and mechanical behaviours, resulting in nonlinear deformation characteristics under an external load. Due to the involvement of both material and geometric nonlinearities, the use of nonlinear elasticity causes a highly expensive computational load, leading to the difficulty to achieve the real-time computational performance required by surgical simulation. On the other hand, in order to satisfy the real-time computational requirement, most of the existing methods are mainly based on linear elasticity under the assumptions of small deformation and homogeneity to describe deformation of soft tissues. Such simplifications allow reduced runtime computation; however, they are inadequate for modelling nonlinear material properties such as anisotropy, heterogeneity and large deformation of soft tissues. In general, the two conflicting requirements of surgical simulation raise immense complexity in modelling of soft tissue deformation. This thesis focuses on establishment of new methodologies for modelling of soft tissue deformation for surgical simulation. Due to geometric and material nonlinearities in soft tissue deformation, the existing methods have only limited capabilities in achieving nonlinear soft tissue deformation in real-time. In this thesis, the main focus is devoted to the real-time and realistic modelling of nonlinear soft tissue deformation for surgical simulation. New methodologies, namely new ChainMail algorithms, energy propagation method, and energy balance method, are proposed to address soft tissue deformation. Results demonstrate that the proposed methods can simulate the typical soft tissue mechanical properties, accommodate isotropic and homogeneous, anisotropic and heterogeneous materials, handle incompressibility and viscoelastic behaviours, conserve system energy, and achieve realistic, real-time and stable deformation. In the future, it is projected to extend the proposed methodologies to handle surgical operations, such as cutting, joining and suturing, for topology changes occurred in surgical simulation

Stem cell based therapy retards the progression of osteoarthritis and promotes repair of meniscus injury of sheep model knee joint

ABSTRACT The aim of this study to determine if intra-articular injection of autologous bone marrow mesenchymal stem cells (ABMSCs) could repair surgically induced osteoarthritis in sheep model. Eighteen male healthy sheep (weighed 18-20kg) were divided into two test groups and one control group. The control groups were not different from the test groups with respect to age and weight, but the test animals underwent a bone marrow aspira- tion for cell preparation in the same time of osteoarthritis induction. ABMSCs were isolated from sheep bone marrow and divided into two groups, namely test group A; ABMSCs cultured in FD medium supplemented with 10% fetal bovine serum (FBS), Test group B; ABMSCs were cultured in FD medium supplimented with 1% FBS and 10 ng/ml TGFβ-3 for three weeks. OA was induced by complete excision of the medial meniscus and resection of the anterior cruciate ligament (ACL). Sheep were subjected to exercise for three weeks post OA induction. After 6 weeks post-operation, test groups received direct intra-articular injection of a single dose 10x106 cells suspended in basal medium into injured sheep knee joint. Con- trol animals received basal medium alone. Six weeks post- cel injection, the femoral condyle and the tibial plateau from test and control groups were removed,fixed,photographed, and assessed by two blinded evaluators based on ICRS grading system, decalcified. Specimens were sectioned into 5 µm and stained with H & E and Safranin O. The result demonstrated that Gross observation of femoral condyle and tibia plaetue of the operated knee joint had OA. The severe OA was clearly observed in in control group knee joints. Test group received intra-articular injection of ABMSCs alone showed moderate OA. Interestingly test group B that received intra-articularinjection of TGF-β3 induced ABMSCs showed mild OA. The histological examination showed clear evidence of articular cartilage and menicscus regeneration in test group B of sheep injured knee joint that received TGF-β3 induced ABMSCs when compared with other groups