Bone Drilling Process Research Articles

Modeling and verification of cortical bone drilling forces based on tissue structure heterogeneity

Bone drilling mechanism study is the basis for the optimization of cortical bone drilling process and drill geometry. In this paper, a drilling force model for modified drills with thinned chisel edge is established considering the heterogeneous structure of cortical bone. The bone mineral density is embedded into the established model, the model can predict the axial thrust force change along the drilling depth direction, and the model is verified through cortical bone drilling experiments. The thrust force and torque predicted by the model are in good agreement with the drilling experimental results of cortical bone drilling. Then, the drilling performance of the modified drill and the common drill is compared through cortical bone drilling experiments. Compared with common drill bits, the maximum reduction in average thrust force of the modified drill bit during stable drilling is 21.21 % (n = 2500 rpm, Vf=60 mm/min). The maximum reduction in average roughness of the hole wall is 21.87 % (n = 500 rpm, Vf=10 mm/min). The drill chisel edge thinning design reduces the negative impact of the negative normal rake angle on the cutting lip of common drill on drilling force and stability. Therefore, the drill bit chisel edge thinning design can effectively improve the drilling performance.

An analysis of bone drilling process using finite element analysis

An analysis of bone drilling process using finite element analysis

Biomechanical Finite Element Simulation of Cochlear Implant Surgical Robot Drilling Through Direct Cochlear Access

AbstractRobotic drilling through direct cochlear access for cochlear implantation (CI) is currently a prominent area in the field of CI surgery. However, the safety of drilling remains an issue due to the limited space within the facial recess. Estimation and control of drilling force are critical to prevent drill‐bit breakthrough, excessive heat generation, and mechanical damage to the facial nerve. The bone drilling process presents a favorable application scenario for finite element (FE) analysis. In this study, a 3D FE model of temporal bone drilling is established for the first time to predict the drilling force. The self‐developed CI surgical robot validates these findings through experimental drilling. The experimental results show that the drilling process can be divided into three stages, and the corresponding force curve can be divided into six zones. The overall trend of temporal bone drilling is two force peaks and one trough in the middle. The drilling force is positively correlated with the feed rate. The FE results found to be in good agreement with the experimental results. Numerical simulation can be utilized as an invaluable tool for assisting in predicting the position of drilling tools and optimizing drilling parameters in the future.

Temperature prediction model of bone drilling considering the effect of tool wear

Biomass bone is biologically active and sensitive to heat; excessive temperatures would destroy the biological activity of the bone tissue or even cause bone necrosis. Therefore, it is vital to control the drilling temperature in clinical surgery for internal fixation of fractures. This paper focused on the influence of tool wear on the drilling temperature during the bone drilling process. The effect of three drilling parameters, the tool diameter, machine spindle speed and tool feed speed, on three dynamic characteristics, the drilling force, drilling temperature and tool wear, was investigated through bone drilling experiments. A prediction model of the bone drilling temperature considering the effect of the amount of wear was established based on Archard wear theory and the heat source method, and was in good agreement with the experimental results. The predicted results showed that worn bits produced drilling temperatures up to 3.4°C higher than those of new bits, and the maximum error in the prediction of the drilling temperature was 11.04%. The temperature model better extended the applicability of the existing temperature models.

Investigation of transient machining in the cortical bone drilling process by conventional and axial vibration-assisted drilling methods.

A temperature exceeding the safety threshold and excessive drilling force occurring during bone drilling may lead to irreversible damage to bone tissue and postoperative complications. Previous studies have shown that vibration-assisted drilling methods could have lower temperatures and drilling forces than those of the conventional drilling method; we hypothesized that the main reason for these reductions stems from the differences in the transient machining processes between conventional and vibration-assisted drilling methods. To investigate these differences, comparative experiments and two-dimensional finite element models were performed and developed. The differences in the transient machining processes were verified by experimentation and clearly exhibited by the finite element models. Compared with the steady cutting process that produced continuous-spiral chips in the conventional drilling method, transient machining in the low-frequency vibration-assisted drilling method was a periodically dynamic cutting-separation process that produced uniform petal chips with specific settings of drilling and vibration parameters. Moreover, the transient machining process in the ultrasonic vibration-assisted drilling method was transformed into a combined action with high-speed impact and negative rake angle cutting processes; this action produced a large proportion of powdery chips. Therefore, it could be concluded that the superposed axial vibration significantly changed the transient machining process and radically changed the mechanical state and thermal environment; these changes were the main reason for the apparent differences in the drilling performance levels.

Experimental temperature evaluation during a robotized bone drilling process

A serious problem associated with orthopedic bone drilling manipulation is the so-called thermal osteonecrosis (TO). This problem occurs because the drilling manipulation generates heat, and the amount of heat depends on the drilling conditions. This work presents the experimental evaluation of the temperature during automated bone drilling by using a handheld Orthopedic bone Drilling Robot ODRO. Up to now, such experimental results related to temperature evaluation in bone drilling by robots have not been presented. Fresh porcine and bovine femur bones were specimens in the experiments. The increase in bone temperature during drilling was measured by a thermal infrared camera. Thermographic sequence images were recorded, processed and visualized using specialized software, which allows to capture accurately the moment of drill bit penetration through the bone and its extraction when going back to initial position. The results showed that under given feed rate and drill speed, when using a new drill bit, the temperature value during porcine femur drilling exceeded the critical threshold of 50 °C for less than 2 s, and thermal osteonecrosis does not occur. When using a worn-out drill bit, the temperature value during bovine femur drilling significantly exceeded the threshold of 50 °C, and thermal osteonecrosis occurs. Thus, to guarantee bone drilling without the risk of thermal osteonecrosis, the automated drilling should be executed with the simultaneous control of speed of drill bit and feed rate. This is possible to be achieved only by robotic execution of the manipulation.

A Review of Surgical Bone Drilling and Drill Bit Heat Generation for Implantation

This study aims to summarize the current state of scientific knowledge on factors that contribute to heat generation during the bone drilling process and how these aspects can be better understood and avoided in the future through new research methodologies. Frictional pressures, mechanical trauma, and surgical methods can cause thermal damage and significant micro-fracturing, which can impede bone recovery. According to current trends in the technical growth of the dental and orthopedic industries’ 4.0 revaluation, enhancing drill bit design is one of the most feasible and cost-effective alternatives. In recent years, research on drilling bones has become important to reduce bone tissue damage, such as osteonecrosis (ON), and other problems that can happen during surgery. Reviewing the influence of feed rate, drill design, drill fatigue, drill speed, and force applied during osteotomies, all of which contribute to heat generation, was a major focus of this article. This comprehensive review can aid medical surgeons and drill bit makers in comprehending the recent improvements through optimization strategies for reducing or limiting thermal damage in bone drilling procedures used in the dental and orthopedic industries.

An in-silico bone drilling protocol to control thrust forces using finite element analysis coupled with the constitutive models

In orthopaedic surgeries, drilling through bone is most widely used to fix the plates and implants. The uncontrolled large thrust forces generated during bone drilling cause micro-crack, and fragmentation around the local host bone which further loosen the implant and fixation. Owing to the experimental limitation and the risk of infection in handling the bone specimens, conducting experiments with all possible combinations of parameter values and selecting the suitable combination is largely limited. So in this paper, finite element analysis coupled with the constitutive models was used to early predict the thrust forces generated in the surgical bone drilling process. The constitutive models developed in the earlier study, namely, Johnson–Cook, Cowper–Symonds, and Johnson–Cook combined with Cowper–Symonds that consider the strain rate dependence of plastic curve were used for the simulations. Results revealed that the trends of the thrust force values predicted from the constitutive models matched well with the experiments. However, the study showed that the Johnson–Cook model combined with the Cowper–Symonds model predicted the thrust forces with a maximum error of only 9.51% followed by the Johnson–Cook model and Cowper–Symonds model with 15.83% and 21.89%, respectively. The outcomes of the study can be used to predict the thrust forces generated in the bone drilling process, and thus, suitable parameters values can be selected to avoid the mechanical damages around the bone drilling site. The outcomes can also be used to plan and rehearse the in-silico bone drilling trials with any combinations of parameter values before performing the actual surgery.

A CT Image-Based Virtual Sensing Method to Estimate Bone Drilling Force for Surgical Robots.

Current surgical robots face challenges to understand preoperative images like human surgeons, which hindering robots from making full use of preoperative information to operate stably and efficiently. We offer a method to estimate drilling force information based on preoperative images to provide a priori force information for surgical robots performing bone drilling tasks. A visual sensing computing framework is proposed to help robots calculate drill-tissue contact area 3D image information in a one-dimensional signal format. Under this computing framework, a computed tomography (CT) image-weighted bone drilling mechanical model is built, which further considers both targets bone shape and material properties to predict the thrust force, torque, and radial force of a drilling process based on preoperative CT images. The built model can respond to multiple bone drilling process factors, such as personalized surgery plans, varying tissue densities, uneven drilling surfaces, different drilling speeds, feed rates, and drill bit geometries. The best trust force prediction error on bovine bones is 1.13 ± 0.95 N, and the best normalized average prediction error on porcine bones is 0.07 ± 0.08. Experiments in spinal pedicle screw placement surgery also show potential application abilities. Our method predicts the bone drilling force well based on preoperative images, providing robots with more efficient preoperative information. This work offers a new perspective to study the interaction relationship between robot surgical instruments and tissues with the assistance of preoperative images.

Computational analysis of cutting parameters based on gradient Voronoi model of cancellous bone.

Bone cutting is a complicated surgical operation. It is very important to establish a kind of gradient porous bone model in vitro which is close to human bone for the research of bone cutting. Due to the existing bone cutting researches are based on solid bone model, which is quite different from human bone tissue structure. Therefore, Voronoi method was used to establish a gradient porous bone model similar to real bone tissue to simulate the process of bone drilling in this paper. High temperature and large cutting force during bone drilling can cause serious damage to bone tissue. Urgent research on bone drilling parameters is necessary to reduce cutting temperature and cutting force. The finite element analysis (FEA) of Voronoi bone models with different gradients is carried out, and a Voronoi model which is similar to real bone tissue is obtained and verified by combining the cutting experiment of pig bone. Then orthogonal experiments are designed to optimize the cutting parameters of Voronoi bone model. The range method is used to analyze the influence weights of cutting speed, feed speed and tip angle on cutting temperature and cutting force, and the least square method was used to predict the cutting temperature and cutting force, respectively. The gradient porous bone model constructed by Voronoi method was studied in detail in this paper. This study can provide theoretical guidance for clinical bone drilling surgery, and the prediction model of bone drilling has practical significance.

Parametric Investigation on Different Bone Densities to avoid Thermal Necrosis during Bone Drilling Process

Bone drilling is a universal surgical procedure commonly used for internal fracture fixation, implant placement, or reconstructive surgery in orthopedics and dentistry. The increased temperature during such treatment increases the risk of thermal penetration of the bone, which may delay healing or compromise the fixation’s integrity. Thus, avoiding penetration during bone drilling is critical to ensuring the implant’s stability, which needs surgical drills with an optimized design. Bovine femur and mandible bones are chosen as the work material since human bones are not available, and they are the closest animal bone to human bone in terms of properties. In the present study, the Taguchi fractional factorial approach was used to determine the best design of surgical drills by comparing the drilling properties (i.e., signal-to-noise ratio and temperature rise). The control factors (spindle speed, drill bit diameter, drill site depth, and their levels) were arranged in an L9 orthogonal array. Drilling experiments were done using nine experimental drills with three repetitions. The findings of this study indicate that the ideal values of the surgical drill’s three parameters combination (S1D1Di2) and their percentage contribution are dependent on the drilling levels of the parameters. However, the result shows that the spindle speed has the highest temperature effect among other parameters in both (femur and mandible) bones.

Effect of Using Coolant on the Formation of Microcracks, Burr and Delamination in Bone Drilling Process

Direct approach for bone fracture treatment usually involves restoring the fractured parts to their initial position and immobilizing them with plates, screws and wires. This approach needs a bone surgery drilling to produce hole for screw insertion. But this drilling process causes mechanical damages, i.e microcracks, burr formation and delamination, that can reduce the stability of the fixation. One of the ways to minimize it is by using coolant. Moreover, it is noted that bone has anisotropic microstucture. The object of this study is to understand the effect of coolant on mechanical damages that occur in bone drilling and to understand the effect of microstructure difference on microcracks that occur in the drilled walls holes. Adult bovine bones and adult goat bones were used in this study as the specimens to represent differences in cortical bone microstructure. Five consecutive holes from the distal to the proximal in each specimen were generated using manual hand-drill (spindle speed (n) = 1000 rpm; drill bit (d) = 4 mm diameter) with the use of coolant as variation. The drilling holes then stained and observed using a microscope. As the result, it was found that the use of coolant can significantly reduce the drilling temperature. Microcracks, burr formation and delamination were found to be quite large in the drilling holes without coolant. However, there is no microcrack found in the drilling holes with coolant, there is only a small number of burr formation was found. In addition, it was found that the differences in bone microstructure affect the number and length of microcracks that occur in the wall of the hole. It can be concluded from this study that the application of coolant is very effective to reduce the drilling temperature and enhancing the quality of the hole generated by bone drilling and the higher the density of osteon in cortical bone, the easier the microcrack to initiate and propagate.

Development of bone chip-vacuum system in orthopedic drilling process

Overheating occurs during the bone drilling process using drill bits in orthopedic surgery. The temperatures frequently exceed 47 °C, usually accepted as critical value, since the bones and surrounding tissues burn and then cause the necrosis during the drilling process. To prevent this, orthopedic surgeons either spray coolants to the drilling zone or pause the drilling process until the bones and tissues cool down. Such heat damage in bones and soft tissues is undesirable event for surgeons. The bone chips, sometimes, are also complicating the bone fracture fixations. In this study, an investigation is described the effects of the processing parameters on bone chip formations, temperature levels and chip-vacuuming performances during drilling. The temperature levels are also measured using thermocouple devices. A bone chip collecting system is developed as a specific device to collect the chips or fragments using vacuuming technique. The collected bone chips are stored in a pot (reservoir) and delivered to a reparative site in case of necessary. Some design parameters for the developed vacuum system are identified considering the temperature rise during the drilling process. Analyzing the effects of these parameters on chip formation and developed vacuum system statistically and some results are presented. At the end of the study, the bone chip-vacuum device was developed and performed successfully to collect the whole fragments in the bone drilling experimental tests. The chip-collecting device was also useful to remove overheat from the drilling zone. The optimal level of the processing parameters was calculated as A1B3C1 for both vacuumed and non-vacuumed conditions. The fractured powder-type chips were formed as anticipated using the cortical structure of diaphyseal part of calf bone which is helpful for chip vacuuming device.

Statistical Modeling, Optimization and Sensitivity Analysis of Tool’s Geometrical Parameters on Process Force in Automatic Cortical Bone Drilling Process

One of the most prevalent machining processes in medical treatments is bone drilling process. During bone drilling, excessive process force can cause breakage, crack initiation and severe damage to bone tissue. In this paper, a systematic study with simultaneous use of response surface method, sensitivity analysis based on Sobol method and regression analysis is performed for investigation the effect of helix angle and point angle of the tool as the most important geometrical parameters on imposed force to the bone during drilling process. Initially, using design of experiments and response surface method, imposed force to the bone is modeled and the governing second order linear regression equation is derived and verified. Then, using Sobol sensitivity analysis, with ability to quantify the sensitivity, it is attempted to investigate the effect of input parameters on drilling force. Finally, optimization of the process inputs is followed to find the best combination which yields the desired drilling force. The minimum drilling force, within the range of input parameters, coincides with point angle of 90 and helix angle of 18. This minimal force is lower than the force in surgery and standard tools. The results showed that an increasing in point angle leads to an increase in drilling force. Also, it is concluded that there is an optimum value for using the helix angle in bone drilling process with minimum imposed force.

Heat Development During Medical Drilling: Influencing Factors and Examination Methods - Overview and First Results.

In many medical disciplines, the process of drilling into the bone plays a crucial role for the implantation or fixation of implants or reconstruction plates. During the bone drilling process, heat is generated on the drill head and within the surrounding tissue. As a result, the increased temperature can lead to thermal damage and related necrosis of the (bone) tissue. This tissue damage is dependent on different drilling parameters and can have important influence on the following tissue healing cascade and finally on implant surveillance. In this context, the present short review elucidates the current state of scientific knowledge with regard to the heat-triggering factors during the bony drilling process and how these factors can be better understood and prevented, now and in the future, through new research approaches. External and internal influencing factors during the drilling process are distinguished and methods to examine the temperature changes are compared. This mini-review further demonstrates first preliminary results of the inflammatory tissue reactions to inadequate drilling processes. Furthermore, possible solutions of new standardized ex vivo-measurement methods to better understand the factors influencing the development of heat and to reduce animal experiments are herein discussed.

Feed rate control in robotic bone drilling process.

The bone drilling process is characterised by various parameters, the most important of which are the feed rate (mm/s) and the drill speed (rpm). They highly reflect the final effects and results of the drilling process, such as mechanical and thermal damages of bone tissue and hole quality. During manual drilling, these parameters are controlled by the surgeon based on his practical skills. But automatic drilling can assure an optimal result of the manipulation where such parameters are under control. During bicortical automatic bone drilling such a process consists of several stages: searching the contact with the first cortex, cortex drilling and automatic stop; searching the contact with the second cortex, cortex drilling and automatic stop; drill bit extraction. This work presents a way to control the feed rate during different stages of the bone drilling process (an original feed rate control algorithm) using the orthopaedic drilling robot (ODRO). The feed rate control is based on a proposed algorithm created and realised by specific software. During bicortical bone drilling process the feed rate takes various values in any stage in the range 0.5-6 mm/s. These values depend on drill bit position and real time force sensor data. The novelty of this work is the synthesis of an original feed rate control algorithm to solve the main problems of bone drilling in orthopaedic surgery - minimisation the drilling time (the heat generation); eliminating of the drill bit slip at the first (near) cortex and the drill bit bending at the second (far) cortex; minimising the risk of micro cracks which causes Traumatic Osteonecrosis; improving hole quality of the drilled holes; eliminating of the drill bit slip and the drill bit bending at the second cortex; minimising the value of the second cortex drill bit penetration by bicortical bone drilling.

Finding the optimal drill bit material and proper drilling condition for utilization in the programming of robot-assisted drilling of bone

Most of the orthopedic surgeries require bone drilling, and accurate control of optimal values of parameters influencing the process of bone drilling in robot-assisted orthopedic surgery is important. Bone drilling process including three materials and three diameters of the drill bit, and three drilling depths, four cooling modes, and ten drilling angles were simulated on the tibia and femur bones using the finite element method (FEM). After ensuring the correctness of FEM simulation results using comparison with experimental data, the impact of the above variables on the changes of three parameters of maximum temperature, thrust force and torque, and temperature durability was assessed. The increase of drill bit diameter and drilling depth, and decrease in the drilling angels led to an increase in the aforementioned parameters, and bone drilling conditions become less favorable. The drill bit with stainless steel material and with gas coolants (especially CO2 coolant) resulted in more optimal bone drilling conditions even in higher drill bit diameter and depth of drilling. The equations between temperature, thrust force, and torque with drilling angles in various cooling modes have been calculated for the programming of drilling robots during orthopedic surgeries to obtain the optimal accurate angle during surgeries.

Biomechanical Evaluation of Temperature Rising and Applied Force in Controlled Cortical Bone Drilling: an Animal in Vitro Study.

The present study was conducted to quantify the relationships between bone drilling process parameters (i.e., feed rate, resting time, exit rate, and drill bit diameter) and drilling outcome parameters (i.e., thrust force and maximum temperature). This study utilized 10-cm cortical bovine samples to evaluate the effects of four independent parameters, including drill bit diameters, six different feed rates, three various resting times, and three different exit rates on thrust force and maximum temperature (MT). A total of 28 stainless steel orthopedic drill bits with a diameter of 2.5 and 3.2 mm, as well as an orthopedic handpiece were attached to the 500N load cell and an accurate linear variable differential transformer to obtain forces. Moreover, two k-type thermocouples were utilized to record the temperature-time curve near the drilling site. The data were analyzed using the two-way analysis of variance and post hoc Tukey-Kramer Honest test. Maximum thrust force (MTF) decreased by almost 230% as the drill bit diameter increased from 2.5 to 3.2 mm in the lowest feed rate. The MTF showed a 335% increase, whereas a decrease of 69% was observed as the feed rates rose from 0.5 to 3 mm/sec. Moreover, the MT decreased to 67% with an increasing exit rate from 1 to 3 mm/sec. Furthermore, a slight increase was observed in MT when the resting time increased from 0 to 2 seconds (P>0.05). The desired drilling is drilling with lower thrust force and lower final temperature of bone. Increasing feed rate can cause an increase and decline in thrust force and final temperature, respectively. The highest rates of MT were 0.5 and 1 mm/min, and the optimum feed rate would be 1.5 mm/min due to the averaged thrust force. Moreover, the resting time had no significant effects on the final temperature. Attentions to resting time would be useful to provide a more accurate, efficient, and uniform drill hole.

An Experimental Investigation of Forces on Cortical Bone in Deep-Hole Bone Drilling

Abstract Deep-hole bone drilling is critical in many surgical implantation procedures. Unlike most common bone-drilling processes, deep-hole bone drilling is performed using a high drilling depth to drill-bit diameter ratio, which can lead to undesirable mechanical and thermal damage during surgical procedures. The objective of this study was to investigate the thrust force and torque generated in deep-hole bone drilling. Drilling tests were performed on bovine cortical bones at a drilling hole depth of 36 mm using a 2.5 mm diameter twist drill bit with a spindle speed of 3000 rpm and feed rates of 0.05, 0.075, and 0.1 mm/rev. Bone chips were collected at different depths and examined using a fiber-optic microscope. Not only are drilling forces a good indicator to assess drilling performances but also chip formation and morphology are important aspects for understanding bone-drilling behaviors. The force signals revealed two distinct states, which were referred to as normal and abnormal states in this study. In the normal state, the force signals remained constant once the drill tip became fully engaged in bone cutting, whereas after a certain drilling depth, the forces considerably increased in the abnormal state. The results of this study indicate that the rapid increase in the force in the abnormal state is mainly attributed to chip clogging inside the flutes as the drilling depth increases. This study also demonstrated that the chip morphology varies with respect to drilling depth, where fragmented chips are produced at shallow drilling depths and powdery chips are produced at deeper drilling depths.

Effects of rotary ultrasonic bone drilling on cutting force and temperature in the human bones.

Efficacy and outcomes of osteosynthesis depend on various factors including types of injury and repair, host factors, characteristics of implant materials and type of implantation. One of the most important host factors appears to be the extent of bone damage due to the mechanical force and thermal injury which are produced at cutting site during bone drilling. The temperature above the critical temperature (47 °C) produces thermal osteonecrosis in the bones. In the present work, experimental investigations were performed to determine the effect of drilling parameters (rotational speed, feed rate and drill diameter) and techniques (conventional surgical bone drilling and rotary ultrasonic bone drilling) on cutting force and temperature generated during bone drilling. The drilling experiments were performed by a newly developed bone drilling machine on different types of human bones (femur, tibia and fibula) having different biological structure and mechanical behaviour. The bone samples were procured from male cadavers with the age of second to fourth decades. The results revealed that there was a significant difference (p < 0.05) in cutting force and temperature rise for rotary ultrasonic bone drilling and conventional surgical bone drilling. The cutting force obtained in rotary ultrasonic bone drilling was 30%-40%, whereas temperature generated was 50%-55% lesser than conventional surgical bone drilling process for drilling in all types of bones. It was also found that the cutting force increased with increasing feed rate, drill diameter and decrease in rotational speed, whereas increasing rotational speed, drill diameter and feed rate resulted in higher heat generation during bone drilling. Both the techniques revealed that the axial cutting force and the temperature rise were significantly higher in femur and tibia compared with the fibula for all combinations of process parameters.