Mechanism Analysis And Damage Research Of Cortical Bone Grinding In Craniotomy

With the rapid development of science and technology today neurosurgery is still the most extreme challenge for human treatment itself.During craniotomy,surgeons use tools such as drills,milling cutters,and diamond grinding bits to open the skull and complete the neurosurgical procedure.Grinding is an important part of craniotomy,where the skull consists of two layers of dense cortical bone and a middle layer of elastic cancellous bone.When the diamond grinding bit rotates at high speed and contacts with the hard cortical bone,the bone tissue is removed and subjected to stress and heat damage.Excessive grinding force produces bone microcracks and excessive temperature causes bone thermal necrosis.It is very important to study the mechanism of cortical bone grinding and to select the grinding parameters,which will not only reduce the damage,but also ensure the grinding efficiency and minimize the patient’s pain.Therefore,this paper took cortical bone as the research object and studied the mechanism of cortical bone grinding microcrack generation and material removal mechanism from the grinding mechanism.A theoretical model of grinding force was established,and the influence of different processing parameters on the grinding force and grinding temperature was investigated by means of finite element simulation and experiments.The main research contents are as follows.(1)Firstly,the bone grinding mechanism was investigated,and the formation mechanism of microcracks and material removal mechanism of grinding process were analyzed from the microstructure of cortical bone.The kinematics and grinding mechanism of single abrasive grain on the grinding head were analyzed,and finally a theoretical model of grinding force was established based on the calculation equations of specific energy and friction force.(2)The finite element simulation of single grain cortical bone grinding was carried out by simplifying the grinding grain into a triangle,establishing the grinding grain and cortical bone model.By designing a single-factor test,the process of grinding bone tissue with abrasive grains was analyzed,and the effects of different grinding speed of abrasive grains,feed rate and front angle of abrasive grains on grinding force were explored.(3)Fresh porcine cortical bone was selected for the grinding test,and the grinding test platform was firstly constructed,and the full factorial test with different processing parameters(rotational speed,feed rate and grinding depth)was designed by Minitab software.The quality of the ground bone surface was observed by scanning electron microscope and surface roughness meter.The reasons for the influence of different grinding parameters on grinding force and grinding temperature were analyzed based on the grinding mechanism and theoretical model of grinding force.(4)The particle swarm algorithm and the expectation function method were introduced.The regression equations of grinding force and material removal rate were obtained based on the theory of cortical bone grinding and experimental results,and a multi-objective optimization problem with the purpose of minimizing grinding force and maximizing material removal rate was established.The multi-objective optimization problem was transformed into a single-objective optimization by the expectation function method,and the parameters were optimized based on the particle swarm algorithm.Finally,the optimized parameters were selected for experimental results verification.The parameter optimization results can provide theoretical guidance for the selection of cortical bone grinding parameters in actual craniotomy.