Development and Validation of a Low-Cost Drilling Model

Background: Simulation models enable learners to have repeated practise at their own time, to master the psycho-motor and sensory acuity aspects of surgery and build their confidence in the procedure. The study aims to develop and evaluate the feasibility of a low-cost drilling model to train surgeons in the drilling task. The model targets three aspects of drilling - (1) Reduce plunge depth, (2) Ability to differentiate between bone and medullary canal and (3) Increase accuracy drilling in various angles. Methods: This cross-sectional study was conducted after obtaining ethics approval. We invited Consultants in the field of Orthopaedic or Hand Surgery to form the 'expert' group, and the 'novice' group consisted of participants who had no prior experience in bone drilling. We developed a drilling simulator model made from a polyvinyl chloride (PVC) pipe filled with liquid silicone. This model cost less than US$5. An electric Bosch drill (model GBM 10 RE) with a 1.4 mm K-wire 10 cm in length (6.5 cm outside the drill) was used for drilling. The main outcomes of the study were time taken for drilling, plunge depth, ability to penetrate the far cortex and accuracy. Results: Thirty-one participants were recruited into the study, of which 15 were experts and 16 were novices. The experts performed significantly better for plunge depth (t = -3.65, p = 0.0003) and accuracy (t = -2.07, p = 0.04). The experts required 20% less time to complete the drilling tasks, but it was not statistically significant (t = -0.79, p = 0.43). Conclusions: The low-cost drilling model could be useful in training Residents in the drilling task. It will allow Residents to practise independently at their own time and assess their own performance.

Tsetse fly inspired steerable bone drill-a proof of concept

The fixation strength of pedicle screws could be increased by fixating along the much stronger cortical bone layer, which is not possible with the current rigid and straight bone drills. Inspired by the tsetse fly, a single-plane steerable bone drill was developed. The drill has a flexible transmission using two stacked leaf springs such that the drill is flexible in one plane and can drill along the cortical bone layer utilizing wall guidance. A proof-of-principle experiment was performed which showed that the Tsetse Drill was able to successfully drill through 5, 10 and 15 PCF cancellous bone phantom which has similar mechanical properties to severe osteoporotic, osteoporotic and healthy cancellous bone. Furthermore, the Tsetse Drill was able to successfully steer and drill along the cortical wall utilizing wall guidance for an insertion angle of 5°, 10° and 15°. The experiments conclude that the tsetse fly-inspired drilling method is successful and even allows the drilling along the cortical bone layer. The Tsetse Drill can create curved tunnels utilizing wall guidance which could increase the fixation strength of bone anchors and limit the risk of cortical breach and damage to surrounding anatomy.

Tool parameters to minimize temperature changes in bone drilling

BACKGROUND

Drilling is a common technique used in orthopedic surgery procedures but causes increases in temperature that can lead to cell damage and death. The extent of this depends largely on the magnitude of the increase in temperature. The commonly accepted limit to prevent osteonecrosis is less than 47 °C for 60 s. There is controversy when it comes to the optimal drilling parameters that limit temperature increases and cell death. In addition to this, less research has been done on the drilling effects in the osteochondral area of joints. Osteochondral tissue damage can interfere with the daily lives of patients and if severe enough will need to be treated. We hypothesize that increasing tool speed and drill bit size will increase temperature that could be above the osteonecrosis limit.

METHODS

Ex-vivo experiments were conducted on porcine shoulder joints that tested the thermal effects of different tool speeds and drill bit sizes. A thermal camera was used to record and measure real time temperature changes while drilling. Three drill bit sizes and five tool speeds were used. Statistical analyses includes Welch's ANOVA with Games-Howell Post Hoc analyses, multivariate linear regression, and surface response regression were used to explore the association of tool speeds and drill bit size on temperature.

RESULTS AND CONCLUSIONS

All the tool speed and drill bit size combinations lead to an increase in temperature that were under the commonly accepted limit. The highest temperature reached was 44 °C with a tool speed of 1150 RPM and 3070 RPM and drill bit size 5.159 mm. It was found that increasing the tool speed increased the temperature change and increasing the drill bit size increased the temperature change.

Prediction of temperature elevation in rotary ultrasonic bone drilling using machine learning models: An in-vitro experimental study

Bone drilling is frequently used during orthopaedic surgeries to treat the fractured part of the bone. A major concern for surgeons is the increase in temperature during real-time orthopaedic bone drilling. The temperature elevation at the bone-tool interface may cause permanent death of regenerative soft tissues and cause thermal osteonecrosis. A robust predictive machine-learning model is suggested in this in-vitro research for monitoring temperature rise during surgery. The objective of the present work is to introduce different machine learning algorithms for predicting temperature elevations in rotary ultrasonic bone drilling. Different machine-learning models were compared with the standard response surface methodology. The performance and accuracy of different predictive models were compared at different error metrics. It was witnessed that support vector machines performed the best for predicting the change in temperature in comparison to other predictive models. Moreover, the error metrics for statistical response surface methodology analysis were comparatively higher than the machine learning algorithms. By using machine learning models, it is possible to predict temperature rise during bone drilling.

Functionally graded additive manufacturing for orthopedic applications

Background

Additive Manufacturing due to its benefits in developing parts with complex geometries and shapes, has evolved as an alternate manufacturing process to develop implants with desired properties. The structure of human bones being anisotropic in nature is biologically functionally graded i,e. The structure possesses different properties in different directions. Therefore, various orthopedic implants such as knee, hip and other bone plates, if functionally graded can perform better. In this context, the development of functionally graded (FG) parts for orthopedic application with tailored anisotropic properties has become easier through the use of additive manufacturing (AM).

Objectives

and Rationale: The current paper aims to study the various aspects of additively manufactured FG parts for orthopedic applications. It presents the details of various orthopedic implants such as knee, hip and other bone plates in a structured manner. A systematic literature review is conducted to study the various material and functional aspects of functionally graded parts for orthopedic applications. A section is also dedicated to discuss the mechanical properties of functionally graded parts.

Conclusion

The literature revealed that additive manufacturing can provide lot of opportunities for development of functionally graded orthopedic implants with improved properties and durability. Further, the effect of various FG parameters on the mechanical behavior of these implants needs to be studied in detail. Also, with the advent of various AM technologies, the functional grading can be achieved by various means e.g. density, porosity, microstructure, composition, etc. By varying the AM parameters. However, the current limitations of cost and material biocompatibility prevent the widespread exploitation of AM technologies for various orthopedic applications.

Novel Catalytic Ceramic Conversion Treatment of Ti6Al4V for Improved Tribological and Antibacterial Properties for Biomedical Applications

Titanium oxide layers were produced via a novel catalytic ceramic conversion treatment (CCCT, C3T) on Ti-6Al-4V. This CCCT process is carried out by applying thin catalytic films of silver and palladium onto the substrate before an already established traditional ceramic conversion treatment (CCT, C2T) is carried out. The layers were characterised using scanning electron microscopy, X-ray diffraction, transmission electron microscopy; surface micro-hardness and reciprocating tribological performance was assessed; antibacterial performance was also assessed with S. aureus. This CCCT has been shown to increase the oxide thickness from ~5 to ~100 µm, with the production of an aluminium rich layer and agglomerates of silver and palladium oxide surrounded by vanadium oxide at the surface. The wear factor was significantly reduced from ~393 to ~5 m³/N·m, and a significant reduction in the number of colony-forming units per ml of Staphylococcus aureus on the CCCT surfaces was observed. The potential of the novel C3T treatment has been demonstrated by comparing the performance of C3T treated and untreated Ti6Al4V fixation pins through inserting into simulated bone materials.

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

AbstractObjective: Understanding medical images like the human surgeon is a challenge for current surgical robots. It is still hard for surgical robots to achieve safe and stable operations with the help of priori information from preoperative images. We proposed a method to estimate drilling force information based on preoperative images, which can provide priori force information for surgical robots to perform bone drilling tasks.

METHODS

A visual sensing computing framework is proposed to obtain the 3D image information from the drill-tissue contact area in a one-dimensional signal format. Under this computing framework, a computed tomography (CT) image-weighted bone drilling mechanical model is built. The model 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.

RESULTS

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 minimum error of the predicted thrust force on bovine bones is 1.130.95 N, and the best normalized average prediction error on porcine bones is 0.070.08. Experiments in spinal pedicle screw placement surgery also show potential application abilities.

CONCLUSION

Our method predicts the bone drilling force well based on preoperative images, providing robots with more efficient preoperative information.

SIGNIFICANCE

This work offers a new perspective to study the interaction relationship between robot surgical instruments and tissues with the assistance of preoperative images.

Vibration-based drilling depth estimation of bone

Drilling is one of the most common forms of tissue removal procedures, and drilling to a desired depth contributes to avoid injury to the soft tissue beyond and ensure implant stability. The deformation of the human musculoskeletal system has been a common problem in many drilling processes, making it difficult to achieve accurate estimation of the drilling depth. To remedy this problem, a dynamic model is presented to describe the relationship between the axial vibration of the drill and the feed rate. During drilling process, the amplitude of the main harmonic is estimated from the high-frequency component of the acceleration signal, while the short-time integral of the low-frequency part is calculated. Both the initial contact of the drilling tool to the bone and breakthrough are identified by comparing either the harmonic amplitude or the short-time integral. The harmonic amplitude is mapped to the data from a non-contact position sensor tracking the feed rate of the drill. Multiple drilling experiments on both a handheld device and a robotic cutting system demonstrated the effectiveness, stability and accuracy of the method when estimating depth. The mean maximum error for drilling depth estimation is less than 15% of the simulated bone thickness when using the handheld device, while the mean maximum error is less than 5% for the robotic cutting system.

Surface quality and pullout strength of ultrasonically-assisted drilling cortical bone

Bone surgery is a complex process involving sustainable and healthy human recuperation, but poor surface quality and loose implant fixtures can affect the recovery time of orthopedic patients. However, it has been demonstrated that the application of ultrasonic vibration during drilling procedures can improve the success of bone remediation procedures. The focus of the present paper was on the investigation of surface quality and pullout strength of drilled holes. After analyzing the special kinematic characteristics of the ultrasonically-assisted drilling (UAD), UAD testing using fresh cortical bone was carried out and compared with the results obtained after conventional drilling (CD) procedures. Surface roughness measurements and microscope examination were used to evaluate surface quality, and an electro-mechanical tensile machine was used to measure pullout resistance. The test findings indicated that surface roughness was reduced by 17-68.7% when using UAD; the axial pullout strength of screws inserted into UAD holes was significantly increased by 4.28-30.1% compared to that of CD. It was found also that low spindle speeds and high feed rates reduced surface quality and the stability of the inserted cortical screws. The findings demonstrated that UAD produced better surface quality and higher pullout strengths, which could provide greater stability for implants and improved post-operative recovery.

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.

Surgical Drill Bit Design and Thermomechanical Damage in Bone Drilling: A Review

As drilling generates substantial bone thermomechanical damage due to inappropriate cutting tool selection, researchers have proposed various approaches to mitigate this problem. Among these, improving the drill bit design is one of the most feasible and economical solutions. The theory and applications in drill design have been progressing, and research has been published in various fields. However, pieces of information on drill design are dispersed, and no comprehensive review paper focusing on this topic. Systemizing this information is crucial and, therefore, the impetus of this review. Here, we review not only the state-of-the-art in drill bit designs-advances in surgical drill bit design-but also the influences of each drill bit geometries on bone damage. Also, this work provides future directions for this topic and guidelines for designing an improved surgical drill bit. The information in this paper would be useful as a one-stop document for clinicians, engineers, and researchers who require information related to the tool design in bone drilling surgery.