Exploration of different electrode types inserted in a 3D model of a patient with incomplete partition type III inner ear malformation.

BACKGROUND: Incomplete partition type III (IP III) represents a rare malformation of the inner ear, posing challenges during cochlear implantation due to inevitable cerebrospinal fluid (CSF) leaks and the potential misplacement of electrodes within the internal auditory canal (IAC). Despite the absence of a consensus on electrode selection, literature suggests both straight and perimodiolar electrodes as viable options for proper insertion. Limited implantation series contribute to the ambiguity in electrode choice. In this study, we evaluated the insertion performance of three electrode types in a 3D model simulating an IP III patient's inner ear. METHODS: A 3D model replicating the inner ear of a patient with IP III undergoing surgery was created, incorporating a canal wall up mastoidectomy and an enlarged round window approach. Insertions were carried out using a straight electrode, a perimodiolar electrode, and a slim perimodiolar electrode, inserted through a sheath in the basal turn of the cochlea. Electrode positions were assessed after each insertion, with each type being tested 20 times. RESULTS: Successful insertion rates were 95 % for the slim perimodiolar electrode, 85 % for the perimodiolar electrode, and 75 % for the slim straight electrode. Notably, the slim perimodiolar electrode required an adapted insertion technique due to the altered cochlear position in IP III cases. Statistical analysis revealed the slim perimodiolar electrode's superiority over the slim straight electrode in achieving successful insertions. CONCLUSIONS: The 3D model of the IP III inner ear proved to be an effective tool for electrode testing and insertion training prior to surgery. Following multiple insertions in the 3D model, the slim perimodiolar electrode demonstrated the highest success rate, emphasizing its potential as the preferred choice for cochlear implantation in IP III cases.

Sternal Reconstruction Using 3D-Printed Titanium Custom-Made Prosthesis for Sternal Dehiscence After Cardiac Surgery.

Sternal dehiscence is an important complication that increases mortality and morbidity in cardiac surgery. Titanium plates have been used to reconstruct the chest wall for a long time. However, with the rise of 3D printing technology, a more sophisticated method, is making a breakthrough. Custom-made 3D-printed titanium prostheses are increasingly used in chest wall reconstruction because they allow almost perfect fitting to the patient's chest wall and lead to good functional and cosmetic results. This report presents a complex anterior chest wall reconstruction using a custom-made titanium 3D-printed implant in a patient with a sternal dehiscence after coronary artery bypass surgery. At first, reconstruction of the sternum was performed using conventional methods, which failed to give adequate results. Finally, a 3D-printed titanium custom-made prosthesis was used for the first time in our center. On the short- and mid-term follow up, good functional results were achieved. In conclusion, this method is suitable for sternal reconstruction after complications in the healing process of median sternotomy wounds in cardiac surgery, especially where other methods do not provide satisfactory results.

A Holistic Approach to Cooling System Selection and Injection Molding Process Optimization Based on Non-Dominated Sorting.

This study applied a holistic approach to the problem of controlling the temperature of critical areas of tools using conformal cooling. The entire injection molding process is evaluated at the tool design stage using four criteria, one from each stage of the process cycle, to produce a tool with effective cooling that enables short cycle times and ensures good product quality. Tool manufacturing time and cost, as well as tool life, are considered in the optimization by introducing a novel tool-efficiency index. The multi-objective optimization is based on numerical simulations. The simulation results show that conformal cooling effectively cools the critical area of the tool and provides the shortest cycle times and the lowest warpage, but this comes with a trade-off in the tool-efficiency index. By using the tool-efficiency index with non-dominated sorting, the number of relevant simulation cases could be reduced to six, which greatly simplifies the decision regarding the choice of cooling system and process parameters. Based on the study, a tool with conformal cooling channels was made, and a coolant inlet temperature of 20 °C and a flow rate of 5 L/min for conformal and 7.5-9.5 L/min for conventional cooling channels were selected for production. The simulation results were validated by experimental measurements.

Physical-Mechanical Characteristics and Microstructure of Ti6Al7Nb Lattice Structures Manufactured by Selective Laser Melting.

The demand of lattice structures for medical applications is increasing due to their ability to accelerate the osseointegration process, to reduce the implant weight and the stiffness. Selective laser melting (SLM) process offers the possibility to manufacture directly complex lattice applications, but there are a few studies that have focused on biocompatible Ti6Al7Nb alloy. The purpose of this work was to investigate the physical-mechanical properties and the microstructure of three dissimilar lattice structures that were SLM-manufactured by using Ti6Al7Nb powder. In particular, the strut morphology, the fracture characterization, the metallographic structure, and the X-ray phase identification were analyzed. Additionally, the Gibson-Ashby prediction model was adapted for each lattice topology, indicating the theoretical compressive strength and Young modulus. The resulted porosity of these lattice structures was approximately 56%, and the pore size ranged from 0.40 to 0.91 mm. Under quasi-static compression test, three failure modes were recorded. Compared to fully solid specimens, the actual lattice structures reduce the elastic modulus from 104 to 6-28 GPa. The struts surfaces were covered by a large amount of partial melted grains. Some solidification defects were recorded in struts structure. The fractographs revealed a brittle rupture of struts, and their microstructure was mainly α' martensite with columnar grains. The results demonstrate the suitability of manufacturing lattice structures made of Ti6Al7Nb powder having unique physical-mechanical properties which could meet the medical requirements.

Surgical applications of three-dimensional printing in the pelvis and acetabulum: from models and tools to implants.

There are numerous orthopaedic applications of three-dimensional (3D) printing for the pelvis and acetabulum. The authors reviewed recently published articles and summarized their experience. 3D printed anatomical models are particularly useful in pelvic and acetabular fracture surgery for planning, implant templating and for anatomical assessment of pathologies such as CAM-type femoroacetabular impingement and rare deformities. Custom-made metal 3D printed patient-specific implants and instruments are increasingly being studied for pelvic oncologic resection and reconstruction of resected defects as well as for revision hip arthroplasties with favourable results. This article also discusses cost-effectiveness considerations when preparing pelvic 3D printed models from a hospital 3D printing centre.

Influence of Processing Parameters on Tensile Properties of SLS Polymer Product.

Polymer products manufactured by additive processes are today increasingly flooding the market. Given that they have broad application ranging from various consumer products to medicine and automotive industry, the products must satisfy certain mechanical properties. In the past studies of selective laser sintering (SLS) for polymer materials, the processing parameter of energy density has been confirmed which affects the tensile properties. Energy density depends on the laser beam speed, laser power and hatch distance; however, in this paper the existing mathematical model has been expanded by the overlay ratio and tests have been conducted how on the basis of the new mathematical model a product with good tensile properties (tensile strength, tensile strength at break, tensile modulus, tensile strain at break) can be manufactured. However, in parameter selection as well, the layer thickness and the manufacturing strategy also play a role, and they may shorten the time and reduce the cost necessary to manufacture a new product from the initial concept to production. The paper also provides a proposal of processing parameters (laser beam speed, laser power and energy density) depending on the manufacturing strategy and layer thickness.

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

OBJECTIVE: Free-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. METHODS: A case series study was performed on 11 patients. Seventy-two screws were implanted using multi-level 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. RESULTS: Twelve screws (17%) were placed more than 3.125 mm out of its optimal position in the centre of pedicle. The tip of the 16 screws (22%) was misplaced more than 6.25 mm 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). CONCLUSION: In 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 multi-level rapid prototyping drill guide template reduces the perforation risk of pedicle screw placement in the lumbar and sacral spine.

INTRODUCTION: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.