Computer integrated surgery systems
- Biomechanical modeling of the lower extremities for pre-operative planning
- Tissue overload prevention in surgery
- Biomechanical modeling for planning of orthodontic treatment
- The sealing effect of the native, deficient and reconstructed labrum of the hip joint. A biomechanical study of new reconstruction techniques
- Development of a multimodal real-time adaptive virtual patient modeling platform for support during catheterization procedures
- Online patient-specific finite element modeling for tissue overload prevention in surgery
Biomechanical modeling of the lower extremities for pre-operative planning
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The goal of this research is to develop a biomechanical model to be used in planning software for orthopedic hip surgery. This model will calculate the forces acting on the hip joint, based on images obtained by a CT-scan. The bone geometry is segmented from this scan, and muscle attachment regions are projected on the resulting bone by use of a database. Also, patient-specific kinematics are obtained by automatically locating anatomical features. The integration of this model into surgical planning software will allow the surgeon to gain a better understanding of the biomechanical consequences of a planned operation.
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Tissue overload prevention in surgery
Master-slave systems are a good example of robot-assisted surgery, the surgeon manipulates complex joysticks (the master), whilst following the surgery on a screen. At the patient side, the instruments are controlled by robotic arms (the slave), which follow the commands of the surgeon. Such systems enhance the accuracy due to a combination of scaling and elimination of the tremor of the surgeon. Extra degrees of freedom at the instrument tip increase the dexterity of the manipulation. Moreover, the surgeon can work in a more ergonomic position. The great drawback of this type of systems is the fact that the surgeon cannot feel what happens at the slave side. This means, for example, that the surgeon doesnt know how hard he is pulling at a tissue, and risks damaging it. This is why force feedback is an active research topic (see webpage PMA). When the instrument forces at the tip are known during an operation, an extra level of safety can be introduced into the procedure. The forces that the surgeon is exerting on the tissue can be linked to the applied damage, for which maximum allowable values can be set. By implementing adaptive threshold levels into the control strategy of the master-slave system, it is possible to limit tissue damage. In current robot-assisted surgery procedures there is, for instance, a risk of tearing an artery because of excessive pulling forces. This new method deals with this type of risks. Presently, research is conducted on experimentally setting the thresholds levels for damage, through in vitro and in vivo experimentation and functional and histological examination, and with the help of finite element modeling, integrating the concept into the master-slave system.
For more information about the Robot-Assisted Surgery group please visit their website.
The daVinci surgical system
FE-models of the clamping of an artery
Biomechanical modeling for planning of orthodontic treatment
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Biomechanical modelling of facial expressions for orthodontic treatment: The aim of the project is the development of a patient specific computer model for the simulation of important facial expressions (laughing, sadness, anger,...). It will include biomechanical modelling of the soft tissues involved and the major muscle groups around the mouth. The first objective is the prediction of esthetic outcome after orthodontic treatment. Therefore the stress within the tooth root due to an applied force should be known (see figure) and subsequently, tooth movement should be calculated. The new positions of the teeth will set new boundary conditions to the rest of the soft-tissue model and thereby define the overall appearance of the outcome. As a second objective, the inverse problem will be studied as well: "starting from an intended 'perfect smile', what is the required orthodontic treatment?"
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The sealing effect of the native, deficient and reconstructed labrum of the hip joint.
A biomechanical study of new reconstruction techniques
Damaging of the labrum and the subsequent decrease of sealing function has an important role in early degeneration of the hip joint in young adults. The decrease of sealing function causes degenerative changes in load distribution in the joint cartilage. Therefore, it is essential to repair this sealing function. As hypothesis it is stated that tears larger than 33% of the diameter of the labrum have an influence on this sealing function. The aim of this research is to provide a new reconstruction technique for the labrum combined with an assessment technique to evaluate the sealing function. To support these two techniques an intra-operative device will be designed based on a Newton-meter or a disposable pressure sensor. A parameterized CAD-model of a scaffold, designed to match the mechanical requirements of a healthy labrum, will be created and tested with finite element analysis. This is followed by a comparison of labral reconstruction while using a semi-tendinosus allogreffe versus a reconstruction with a scaffold, which results in the optimal reconstruction technique. When the optimal reconstruction technique is selected, the load in the reconstructed labrum and acetabulum during normal anatomical range of motion will be evaluated experimentally (in vitro) and by finite element analysis. At the end of this research a validation using in vivo data to create a finite element model will show the connection between the clinical and experimental data.
Modern medicine is irreversibly shifting towards less invasive surgical procedures. Conventional open surgery approaches are systematically being replaced by interventions that reduce access trauma and thereby minimize pain and hospitalization periods for patients. The downside of this approach is reduced visibility and awareness of potential critical events. The main objective of this doctoral dissertation is the development of a multi-modal real-time virtual patient modeling platform for support of catheterization procedures. It will fuse information from pre-operative imaging with intraoperatively acquired data, integrating geometrical and physical (mainly FEM based) models with tracking information. General purpose graphics processing units are used as a way to break the real time constraints of the surgical theater. This information will be provided to the interventionalist in an intuitive way, allowing him/her access to models prior(pre-operative imaging), during(real-time support) and after the intervention as an evaluation phase.
Current systems for conventional or robotic minimally invasive surgery do not measure the interaction forces between the surgical tool and the manipulated tissues. This lack of information has been known to induce unwanted tissue damage. The implementation of a force measurement system gives the information about the applied force but because safety thresholds can only be defined related to the local tissue stresses and strains, the acquired instrument forces and displacements must be translated to these local tissue stresses and strains by means of biomechanical models.
The focus lies on the generation of such models that are able to provide ‘intelligent’ and online information to the surgeon and that are based upon reliable intra-operative force and tissue deformation data. Patient-specific, intraoperative models that estimate soft tissue loading and deformation should contribute to patient safety during robot assisted minimally invasive surgical procedures. The idea is to investigate how large the interspecimen variation of material parameters will be in patients, and to develop an indexing method to classify patients into material-property groups, based on physiological data (e.g. sex, age and pathology). This information will be used to create the necessary biomechanical models.
