Orthopaedic and traumatologic implants
In general, the large group of orthopaedic and traumatologic implants contains medical devices for the use in human body and covers parts such as screws, plates and nails for the treatment of bone fractures as well as prostheses for the replacement of pathologic joint functions (hip, knee, elbow, shoulder).
Object of a numerical analysis is the prediction of the static strength and life time of an implant and its optimisation, the determination of the influence of initial stresses or friction on deformation and stress distribution in an implant consisting of several parts as well as the characterisation of the bone-implant-interaction and the effects on the bone structure.
To apply the method of finite element analysis, a complex three-dimensional model of the implant with or without the surrounding bone structure is generated. The boundary and load conditions are defined according to DIN/ISO/ASTM test standards for such implants. Cyclic or physiological loads (as from gait analyses) can be taken into account. Bone is modelled with its specific characteristics (see bone modelling).
As result of the simulation, the distribution of stresses and deformations are available for the entire implant. They are used to assess the static strength and the fatigue behaviour and present the basis for an efficiently performed optimisation cycle. On the basis of the calculated contact stresses and the relative motion between implant and bone, the heat transfer at the interface during the insertion process of a bone screw can be predicted.The simulations also give insights into the loosening behaviour of a prostheses or the thermal and mechanical bone damage potential.
- FE model of a bone plate - definition of boundary conditions
- Equivalent stresses in a bone plate on a midfoot bone by a typical load of the foot in a straight plane (moment in a plate plane)
- Stress distribution on a screw thread under torsional load
