Prototype Drill Research Articles

Design and Implementation of a Control System to Mitigate Osteonecrosis in Orthopedic Bone Drilling Procedures

The drilling process in orthopedic surgery can sometimes lead to an undesired increase in temperature, which can cause serious damage to bones and soft tissues. This overheating is typically identified as a temperature above 47°C, known as the critical limit, and can result in the condition known as osteonecrosis. A previous study [1] designed and manufactured a prototype drill mechanism with a cooling device and tested it on fresh bovine bones in laboratory conditions. This study aims to develop a new control system, using a proportional–integral–derivative (PID) controller, to prevent overheating and the resulting osteonecrosis. The bone temperature is constantly measured using a thermocouple and, when it reaches the critical temperature of 47°C, the cooling device is activated by the PID controlled system. This new control system makes the drill mechanism with cooling device more user-friendly and allows surgeons to set a desired temperature level manually.

Simulating Mars Drilling Mission for Searching for Life: Ground-Truthing Lipids and Other Complex Microbial Biomarkers in the Iron-Sulfur Rich Río Tinto Analog.

Sulfate and iron oxide deposits in Río Tinto (Southwestern Spain) are a terrestrial analog of early martian hematite-rich regions. Understanding the distribution and drivers of microbial life in iron-rich environments can give critical clues on how to search for biosignatures on Mars. We simulated a robotic drilling mission searching for signs of life in the martian subsurface, by using a 1m-class planetary prototype drill mounted on a full-scale mockup of NASA's Phoenix and InSight lander platforms. We demonstrated fully automated and aseptic drilling on iron and sulfur rich sediments at the Río Tinto riverbanks, and sample transfer and delivery to sterile containers and analytical instruments. As a ground-truth study, samples were analyzed in the field with the life detector chip immunoassay for searching microbial markers, and then in the laboratory with X-ray diffraction to determine mineralogy, gas chromatography/mass spectrometry for lipid composition, isotope-ratio mass spectrometry for isotopic ratios, and 16S/18S rRNA genes sequencing for biodiversity. A ubiquitous presence of microbial biomarkers distributed along the 1m-depth subsurface was influenced by the local mineralogy and geochemistry. The spatial heterogeneity of abiotic variables at local scale highlights the importance of considering drill replicates in future martian drilling missions. The multi-analytical approach provided proof of concept that molecular biomarkers varying in compositional nature, preservation potential, and taxonomic specificity can be recovered from shallow drilling on iron-rich Mars analogues by using an automated life-detection lander prototype, such as the one proposed for NASA's IceBreaker mission proposal.

Petrol, Gaz ve Madencilik Endüstrisinde Bilgi Gösterimi için Ontoloji Temelli bir Yaklaşım

Although there are some works applying semantic web technologies in oil, gas, and mining industry, most of them involve finding and analyzing the data from a variety of activities such as drilling, exploration and production. On the other hand, it is also possible to develop semantic web applications that may dramatically reduce cycle times and indirect costs. This work is a practice that bridges the gap between semantic web technologies and oil, gas, and mining industry. We propose a prototype drilling tools ontology. We populate the ontology focusing on drill bit concept as a starting point. In the population phase, we used existing spreadsheet documents, product catalogs and web pages containing product data. We document clearly what has been learned from the experience of building the ontology and how the experience can inform the work of other investigators. The same ontology population methods apply also to other products; therefore, the applicability of our work extends well beyond the specific products we are considering in our project. This ontology is also used in a prototype drill bit marketplace portal, which supports searching and comparing drill bits of different vendors.

Proof-of-concept prototype drill-guide for use in medial patello-femoral ligament (MPFL) reconstruction surgery

ABSTRACTFor surgical reconstruction of the medial patello-femoral ligament (MPFL) a variety of techniques are used for fixation of the graft to the medial border of the patella. The bone bridge or V-shaped tunnel technique utilises two tunnels drilled from the medial aspect of the patella that converge centrally creating a tunnel through which the graft is threaded. This technique has advantages: it avoids hardware (bone anchors) and their associated complications, creates a broad attachment of the ligament approximating normal anatomy and the tunnel does not breach the lateral cortex of the patella reducing the risk of patella fracture. In current practice the bony tunnels are created using freehand techniques. These rely on estimation of the patella centre by the surgeon and is subject to wide variation. Additionally this technique can be inefficient, inaccurate and time consuming. To address these disadvantages a new drill-guide device was developed. A prototype drill-guide was constructed using CAD and 3D printing methods. The device was designed to allow the surgeon to accurately and efficiently drill the required v-shaped bone tunnel. To assess the efficacy of the prototype drill guide, an experiment designed to assess a group of ten surgeons with an average of 4.2 years experience performing the task of creating a v-shaped bone tunnel using a free-hand technique and the drill-guide. To determine the accuracy of the tunnel placement, the angle between drill holes, distance from centre of the patella and the amount of over-drill were measured. Procedure duration was also compared. The results revealed that the prototype drill-guide created a more accurate bone bridge than the traditional free hand method. The root mean square error for the distance from centre was 0.50 mm vs 2.12 mm and the angle between tunnels was 2.6O vs 15.9O for the prototype and traditional methods respectively. There was a mean of 8.9 mm over-drill with the traditional method, which was negated when using the guide. Surgeons using the guide were approximately 25% faster than using the traditional free-hand technique. The prototype drill-guide improved the accuracy, reduced the variability, and reduced procedure duration compared to the traditional free-hand technique.

Translaminar facet joint screw insertion with a rapid prototyping guide template: a cadaver study

It is technically demanding and requires rich experience to insert the translaminar facet screw(TFS) via the paramedian mini-incision approach. It seems that it is easy to place the TFS using computer-assisted design and rapid prototyping(RP) techniques. However, the accuracy and safety of these techniques is still unknown. The aim of this study is to assess the accuracy and safety of translaminar facet screw placement in multilevel unilateral transforaminal lumbar interbody fusion using a rapid prototyping drill guide template system. A patient-matched rapid prototyping translaminar facet screw guide was examined in fourteen cadaveric lumbar spine specimens. A three-dimensional (3D) preoperative screw trajectory was constructed using spinal computed tomography scans, from which individualized guides were developed for the placement of translaminar facet screws. Following bone tunnel establishment, the 3D positioning of the entry point and trajectory of the screws was compared to the preoperative plan as found in the Mimics software.Among 60 trajectories eligible for assessment, no cases of clinically significant laminar perforation were found. The mean deviation between the planned and the actual starting points on spinous process was 1.22 mm. The mean tail and submergence angle deviation was found to be 0.68°and 1.46°, respectively. Among all the deviations, none were found to have any statistical significance. These results indicate that translaminar facet screw placement using the guide system is both accurate and safe.

Comparison of the effect of navigation template assisted spinal pedicle fixation and traditional pedicle screw fixation:a Meta-analysis

To systematically evaluate the efficacy of rapid prototyping drill navigation template-assisted pedicle screw fixation and traditional anatomic landmark-based fixation in the treatment of spinal disease by accessing and searching some relevant literatures home and abroad. Randomized Controlled Trials (RCTs) and prospective case-control studies or retrospective case-control studies about rapid prototyping drill templates-assisted pedicle screw fixation and traditional anatomic landmark-based fixation for the treatment of spinal disease were searched electronically in PubMed, The Cochrane Library(Issue 5, 2017), Clinical Trial, Google Scholar, Web of Science, CNKI, Wanfang database and VIP database before June 2017. According to the inclusion and exclusion criteria, two researchers independently screened the literatures, and extracted the data. The methodological quality of randomized controlled trials were evaluated by the Cochrane Handbook, and prospective case-control studies and retrospective case-control studies were evaluated by the NOS scale. The outcomes were analyzed using RevMan 5.3 software provided by the Cochrane information management system. A total of 7 articles were included, including 2 RCTs, 1 prospective case-control study and 4 retrospective case-control studies. A total of 237 patients were implanted with 1 688 pedicle screws, including 898 screws in the navigation template group, 790 screws in the conventional method group. Meta-analysis results showed that there was significant difference in the excellent rate of screw implantation between navigation template group and conventional method group [OR=5.05, 95% CI(3.13, 8.16), P<0.000 01], there was significant difference in operative time, intraoperative blood loss for thoracolumbar surgery [WMD=-27.19, 95% CI(-38.21, -16.17), P<0.000 01; WMD=-100.82, 95% CI(-182.26, -19.37), P=0.02]. Compared with traditional pedicle screw fixation, navigation template spine pedicle screw fixation has better clinical effect, which can improve the excellent rate of screw placement, reduce the operation time and intraoperative bleeding.

Computer-assisted Patient-specific Prototype Template for Thoracolumbar Cortical Bone Trajectory Screw Placement: A Cadaveric Study.

The cortical bone trajectory (CBT) screw technique yields effective mechanical and clinical results, improving the holding screw strength with a less invasive exposure. Accurate and safe screw placement is crucial. A patient-specific drill template with a preplanned trajectory was considered a promising solution; however, it is critical to assess the efficacy and safety of this technique. This study aims to evaluate the accuracy of patient-specific computed tomography (CT)-based rapid prototype drill guide templates for the CBT technique. CT scanning was performed in 7 cadaveric thoracolumbar spines, and a 3-dimensional reconstruction model was generated. By using computer software, we constructed drill templates that fit onto the posterior surface of thoracolumbar vertebrae with drill guides to match the CBT. In total, 80 guide templates from T11 to L5 were created from the computer models by using rapid prototyping. The drill templates were used to guide the drilling of CBT screws without any fluoroscopic control, and CT images were obtained after fixation. The entry point and direction of the planned and inserted screws were measured and compared. In total, 80 screws were inserted from T11 to L5. No misplacement or bony perforation was observed on postoperative CT scan. The patient-specific prototype template system showed the advantage of safe and accurate cortical screw placement in the thoracolumbar spine. This method showed its ability to customize the patient-specific trajectory of the spine, based on the unique morphology of the spine. The potential use of drill templates to place CBT screws is promising.

Application of a novel 3D drill template for cervical pedicle screw tunnel design: a cadaveric study.

To develop and validate the efficacy and accuracy of a three-dimensional (3D) computed tomography (CT) reconstructive rapid prototyping drill template for cervical pedicle screw placement. CT thin-layer scans were obtained from 12 adult cadaveric cervical specimens and reconstructed. The ideal screw channels were chosen by analyzing the cross sections of the reconstructed 3D images. The navigation templates were designed and printed based on the optimal screw channels. The pedicle screws were placed on the cadaver specimens under template guidance, and the cadaver specimens were scanned and reconstructed. The pre- and post-operative models were compared. Entry point and exit point data of these two models were collected and compared using the Chi-square test. A total of 164 cervical pedicle screws were placed; among them, six punctured the cortical bone of the vertebral pedicle reaching an accuracy of 96.3%. Among the outside screws, all of the deviation distances were <2mm. The Chi-square test results showed that when a deviation of 1.2mm was used as a standard for the entry point, there was no difference between the two groups (χ 2=1.346, p=0.248); when a deviation of 2.2mm was used as a standard for the exit point, there was no difference between the two groups (χ 2=3.250, p=0.061). The 3D CT reconstructive rapid prototyping drill template combined with the screw tunnel design based on 3D cutting technique can help facilitate accurate cervical pedicle screw insertion.

Use of rapid prototyping drill template for the expansive open door laminoplasty: A cadaveric study

ObjectiveTrough preparation is a technically demanding yet critical procedure for successful expansive open door laminoplasty (EOLP), requiring both proper position and appropriate bone removal. We aimed to use the specific rapid prototyping drill template to achieve such requirement. MethodsThe 3D model of the cadaveric cervical spine was reconstructed using the Mimics 17.0 and Geomagic Studio 12.0 software. The drilling template was designed in the 3-Matic software. The trough position was simulated at the medial margin of the facet joint. Two holders were designed on both sides. On the open side, the holder would just allow the drill penetrate the ventral cortex of the lamina. On the hinge side, the holder was designed to keep the ventral cortex of the lamina intact. One orthopedic resident performed the surgery using the rapid prototyping drill template on four cadavers (template group). A control group of four cadavers were operated upon without the use of the template. ResultsThe deviation of the final trough position from the simulated trough position was 0.18mm±0.51mm in the template group. All the troughs in the template group and 40% of the troughs in the control group were at the medial side of the facet joint. The complete hinge fracture rate was 5% in the template group, significantly lower than that (55%) in the control group (P=0.01). ConclusionThe rapid prototyping drill template could help the surgeon accomplish proper trough position and appropriate bone removal in EOLP on the cadaveric cervical spine.

Cervical screw placement using rapid prototyping drill templates for navigation: a literature review.

Due to the high screw malposition rate and the potential risk of neurovascular injury in cervical fixation surgeries, guided tools, mainly computer-assisted surgery navigation systems and rapid prototyping drill templates (RPDTs) have increasingly been developed to help surgeons improve screw placement accuracy. Although RPDTs have been used in cervical surgeries for almost 2 decades, no specific review has been performed detailing the state of this technique. Thus, in the current review, we fully discuss the status of applying RPDTs in cervical surgeries. Studies that tested the accuracy and reliability of RPDTs in guiding cervical screw placements were included in this review. The fabrication workflow and usage of RPDTs, the accuracy and reliability of using RPDTs for screw and plate placement, the advantages and disadvantages of RPDTs and their prospects for future applications as a part of cervical fixation instrumentation are discussed. As the design of RPDTs becomes more rational, the accuracy and reliability of these devices have significantly improved in cervical fixation surgeries. Moreover, RPDTs decrease the intraoperative radiation exposure for surgeons and patients relative to conventional methods. However, some disadvantages also exist. The fabrication of RPDTs is time-consuming, and the time required to learn the related software is long. We believe that because of their merits, the RPDT technique is worth promoting for use in cervical surgeries. However, the time-consuming fabrication workflow and the long period required to learn the related software might limit its widespread use. In the future, the workflow should be simplified to reduce the extra workload for surgeons. Moreover, more clinical studies with high-level evidence are still needed to further test its accuracy and feasibility.

Error rate of multi-level rapid prototyping trajectories for pedicle screw placement in lumbar and sacral spine

ObjectiveFree-hand pedicle screw placement has a high incidence of pedicle perforation which can be reduced with fluoroscopy, navigation or an alternative rapid prototyping drill guide template. In our study the error rate of multi-level templates for pedicle screw placement in lumbar and sacral regions was evaluated. MethodsA case series study was performed on 11 patients. Seventy-two screws were implanted using multilevel drill guide templates manufactured with selective laser sintering. According to the optimal screw direction preoperatively defined, an analysis of screw misplacement was performed. Displacement, deviation and screw length difference were measured. The learning curve was also estimated. ResultsTwelve screws (17%) were placed more than 3.125mm out of its optimal position in the centre of pedicle. The tip of the 16 screws (22%) was misplaced more than 6.25mm out of the predicted optimal position. According to our predefined goal, 19 screws (26%) were implanted inaccurately. In 10 cases the screw length was selected incorrectly: 1 (1%) screw was too long and 9 (13%) were too short. No clinical signs of neurovascular lesion were observed. Learning curve was insignificantly noticeable (P=0.129). ConclusionIn our study, the procedure of manufacturing and applying multi-level drill guide templates has a 26% chance of screw misplacement. However, that rate does not coincide with pedicle perforation incidence and neurovascular injury. These facts along with a comparison to compatible studies make it possible to summarize that multi-level templates are satisfactorily accurate and allow precise screw placement with a clinically irrelevant mistake factor. Therefore templates could potentially represent a useful tool for routine pedicle screw placement.

A Miniature Surgical Drill Using Ultrasonic/Sonic Frequency Vibration

A study is presented of a miniature ultrasonic surgical drill designed for bone biopsy, based on an ultrasonic/sonic drill which converts high frequency to low frequency vibrations through a freely vibrating mass between an ultrasonic transducer-horn and a drill bit. For conventional surgical drilling using a rotary drill or an ultrasonic drill, considerable power is required to penetrate into bone and the efficiency is low. However, for ultrasonic/sonic drilling, sufficient acoustic energy is accumulated and then released through each impact to achieve precise drilling with a lower power requirement. The ultrasonic/sonic drill was originally invented for rock drilling in low gravity environments. In this study it is incorporated in a miniature ultrasonic surgical drill and the effective impulse delivered to the bone is used to evaluate the drilling performance. To develop a miniature surgical device based on maximising the effective impulse, optimisation of the ultrasonic horn and free-mass is first demonstrated. The shape and dimensions of the ultrasonic horn and free-mass are determined through FEA, which focuses on maximising the post-collision velocity of the free-mass. Then, the entire dynamic stack constituting the surgical drill device is modelled as a mass-spring-damper system to analyse the dynamic behaviour. The numerical model is validated through experiments, using a prototype drill, which record the velocity of the free-mass and the drilling force. The results of the numerical models and experiments indicate this miniature ultrasonic surgical drill can deliver sufficient impulse to penetrate bone and form the basis of an ultrasonically activated bone biopsy device.

Deviation analysis of atlantoaxial pedicle screws assisted by a drill template.

Although C1-C2 pedicle screw fixation provides an excellent fusion rate and rigid fixation, this technique has a potential risk. It is essential to develop an accurate screwing method to avoid this neurovascular injury. To develop and validate the accuracy of a novel navigational template for C1-C2 pedicle screw placement in cadaveric specimens, computed tomography scans with 1-mm-wide cuts were obtained of 32 cadaveric cervical specimens. The authors developed 64 three-dimensional full-scale templates that were created by computer modeling with a rapid prototyping technique from the computed tomography data. Drill templates were constructed with a custom trajectory for each level and side. The drill templates were used to guide the establishment of a pilot hole for screw placement. The average distances between ideal and actual entry points of the C1 pedicle screws in the x, y, and z axes were 0.16±0.46 mm, 0.11±0.52 mm, and -0.01±0.54 mm, respectively, on the left side and 0.11±0.49 mm, 0.01±0.56 mm, and -0.09±0.59 mm, respectively, on the right side. The average distances between ideal and actual entry points of the C2 pedicle screws in the x, y, and z axes were 0.05±0.54 mm, 0.20±0.59 mm, and -0.06±0.58 mm, respectively, on the left side and 0.17±0.55 mm, 0.1±0.58 mm, and -0.01±0.49 mm, respectively, on the right side. Factors related to human error and imprecision are responsible for most malpositioning of instrumentation. The rapid prototyping drill template for C1-C2 screw placement is described to minimize human error, although it introduces error related to computer software and variation in manufacturing.

Deviation analysis of C2 translaminar screw placement assisted by a novel rapid prototyping drill template: a cadaveric study

The goal of this study is to evaluate the accuracy of patient-specific CT-based rapid prototype drill templates for C2 translaminar screw insertion. Volumetric CT scanning was performed in 32 cadaveric cervical spines. Using computer software, the authors constructed drill templates that fit onto the posterior surface of the C2 vertebrae with drill guides to match the slope of the patient's lamina. Thirty-two physical templates were created from the computer models using a rapid prototyping machine. The drill templates were used to guide drilling of the lamina and post-operative CT images were obtained. The entry point and direction of the planned and inserted screws were measured and compared. Sixty-four C2 translaminar screws were placed without violating the cortical bone of a single lamina. The bilateral average transverse angle of intended and actual screw for C2TLS was 56.60 ± 2.22°, 56.38 ± 2.51°, 56.65 ± 2.24°, 56.39 ± 2.45°. The bilateral mean coronal angle of the planned and actual screw for C2TLS was 0°, 0°, -0.07 ± 0.32°, 0.12 ± 0.57°. The average displacement of the entry point of the superior and inferior C2TLS in the x, y, z axis was 0.27 ± 0.85, 0.49 ± 1.46, -0.28 ± 0.69, 0.43 ± 0.88, 0.38 ± 1.51, 0.23 ± 0.64 mm. The small deviations seen are likely due to human error in the form of small variations in the surgical technique and use of software to design the prototype. This technology improves the safety profile of this fixation technique and should be further studied in clinical applications.

A novel computer-assisted drill template for atlantoaxial pedicle screw placement:a cadaveric experimental study

To validate the accuracy of atlanto-axial pedicle screw placement with a rapid prototyping drill guide template and analyze the factors of screw deviations. Computed tomography (CT) scan was performed in 16 cervical specimens. And three-dimension cervical vertebrae was reconstructed by Mimics software. The ideal trajectory for atlanto-axial pedicle screws was designed with a complementary basal template for posterior surface of atlanto-axial corresponding anatomical structure. Then drill guide template was materialized in a rapid prototyping machine. These templates were used during operation. The entry point and ideal and actual trajectories were measured after matching the positions of preoperative and postoperative specimens at designated coordinate axis. The average displacement of entry point of left and right C1 pedicle screw in x, y, z axis was (0.14 ± 0.59),(0.31 ± 1.32), (0.27 ± 0.68), (0.23 ± 0.55), (0.43 ± 1.21) and (0.30 ± 0.72) mm. And the average displacement of entry point of left and right C2 pedicle screw in m, n, p axis was (0.25 ± 0.85), (0.52 ± 1.52), (-0.27 ± 0.67), (0.44 ± 0.87), (0.38 ± 1.48), (-0.14 ± 0.62) mm.No statistically significant difference existed (P > 0.05) in deviation of entry point and between ideal and actual trajectories. Both human handling and inherent hardware and software factors are main reasons for a deviation of C1-C2 pedicle screw placement assisted by a rapid prototyping drill guide template.Ease of operation and individualized design are the advantages of drill guide template so as to greatly improve the precision of screw placement and reduce screw deviation.

A multi-level rapid prototyping drill guide template reduces the perforation risk of pedicle screw placement in the lumbar and sacral spine

The method of free-hand pedicle screw placement is generally safe although it carries potential risks. For this reason, several highly accurate computer-assisted systems were developed and are currently on the market. However, these devices have certain disadvantages. We have developed a method of pedicle screw placement in the lumbar and sacral region using a multi-level drill guide template, created with the rapid prototyping technology and have validated it in a clinical study. The aim of the study was to manufacture and evaluate the accuracy of a multi-level drill guide template for lumbar and first sacral pedicle screw placement and to compare it with the free-hand technique under fluoroscopy supervision. In 2011 and 2012, a randomized clinical trial was performed on 20 patients. 54 screws were implanted in the trial group using templates and 54 in the control group using the fluoroscopy-supervised free-hand technique. Furthermore, applicability for the first sacral level was tested. Preoperative CT-scans were taken and templates were designed using the selective laser sintering method. Postoperative evaluation and statistical analysis of pedicle violation, displacement, screw length and deviation were performed for both groups. The incidence of cortex perforation was significantly reduced in the template group; likewise, the deviation and displacement level of screws in the sagittal plane. In both groups there was no significantly important difference in deviation and displacement level in the transversal plane as not in pedicle screw length. The results for the first sacral level resembled the main investigated group. The method significantly lowers the incidence of cortex perforation and is therefore potentially applicable in clinical practice, especially in some selected cases. The applied method, however, carries a potential for errors during manufacturing and practical usage and therefore still requires further improvements.

Efficacy and accuracy of a novel rapid prototyping drill template for cervical pedicle screw placement

Objective: To develop and validate the efficacy and accuracy of a novel drill template for cervical pedicle instrumentation.Materials and Methods: A CT scan of the cervical vertebrae was performed, and a 3D model of the vertebrae was reconstructed using MIMICS 10.01 software. The 3D vertebral model was then exported in STL format, and opened in a workstation running UGS Imageware 12.0 software to determine the optimal pedicle screw size and orientation. A virtual navigational template was established according to the laminar anatomic trait, and physical navigational templates were manufactured using rapid prototyping. The navigational templates were used intraoperatively to assist in the placement of cervical pedicle screws.Results: In all, 84 pedicle screws were placed, and the accuracy of screw placement was confirmed with postoperative X-rays and CT scans. Eighty-two screws were rated as Grade 0, 2 as Grade 1, and no screws as Grade 2 or 3. Hence, safer screw positioning was accomplished with the drill template technique.Conclusions: This study demonstrates a patient-specific template technique that is easy to use, can simplify the surgical act, and generates highly accurate cervical pedicle screw placement. The advantages of this technology over traditional techniques are that it enables planning of the screw trajectory to be completed prior to surgery, and that the screw can be sized to fit the patient's anatomy.

A10 切り屑吸引ドリルの吸引性能に及ぼす影響因子(OS13 環境適応形加工(2))

An MQL method can realize ecologically-friendly machining by suppression of amount of supplied coolant. However, we must consider alternative chip control method because the MQL method has only a poor chip disposal performance. Authors proposed a novel machine tool with chip-suctioning system by use of hollow cutting tool. In this study, a prototype drill suitable for the chip-suctioning system was developed. From some experiments, the developed drill successfully functioned as chip-suctioning tool in practical drilling condition.

Delamination analysis of carbon fibre reinforced laminates: Evaluation of a special step drill

Drilling of carbon fibre/epoxy laminates is usually carried out using standard drills. However, it is necessary to adapt the processes and/or tooling as the risk of delamination, or other damages, is high. These problems can affect mechanical properties of produced parts, therefore, lower reliability. In this paper, four different drills – three commercial and a special step (prototype) – are compared in terms of thrust force during drilling and delamination. In order to evaluate damage, enhanced radiography is applied. The resulting images were then computational processed using a previously developed image processing and analysis platform. Results show that the prototype drill had encouraging results in terms of maximum thrust force and delamination reduction. Furthermore, it is possible to state that a correct choice of drill geometry, particularly the use of a pilot hole, a conservative cutting speed – 53 m/min – and a low feed rate – 0.025 mm/rev – can help to prevent delamination.

Image-based drill templates for cervical pedicle screw placement

Pedicle screws (PSs) in the cervical spine can provide fixation superior to current fixation methods; however, their implementation is challenging due to the small size of the cervical vertebrae. In this study, the authors explored and evaluated the use of patient-specific, rapid prototype drill templates for PS placement in the cervical spine. The goal of the study was to assess the accuracy of a drill template in the placement of cervical PSs at a single vertebral level. Volumetric CT scanning was performed in 4 cadaveric cervical spines. Using computer software, the authors constructed drill templates with a predefined trajectory designed to match the posterior surface of vertebrae C3-7. Twenty physical templates were created from the computer models using a rapid prototyping machine. The drill templates were used to guide pilot-hole drilling, and CT scanning was performed to assess the accuracy of the pilot holes. Pedicle screws (3.5-mm diameter) were placed in the pilot holes. The spines were then dissected to separate the vertebrae, and the trajectory of the screws was visually inspected. The feasibility of this patient-specific, rapid prototyping technique was demonstrated. Imaging and visual inspection of pilot holes and cervical PSs revealed that the majority of trajectories did not violate the pedicle cortex (19 [95%] of 20). The single cortical violation was judged as noncritical and would probably not have resulted in injury to a patient. The potential of drill templates to aid in the placement of cervical PSs is promising. The authors' methods appear to provide an accurate technique and trajectory for PS placement in the cervical spine.