3D printed patient-specific fixation plates for the treatment of slipped capital femoral epiphysis: Topology optimization vs. conventional design.

Orthopedic plates are commonly used after osteotomies for temporary fixation of bones. Patient-specific plates have recently emerged as a promising fixation device. However, it is unclear how various strategies used for the design of such plates perform in comparison with each other. Here, we compare the biomechanical performance of 3D printed patient-specific bone plates designed using conventional computer-aided design (CAD) techniques with those designed with the help of topology optimization (TO) algorithms, focusing on cases involving slipped capital femoral epiphysis (SCFE). We established a biomechanical testing protocol to experimentally assess the performance of the designed plates while measuring the full-field strain using digital image correlation. We also created an experimentally validated finite element model to analyze the performance of the plates under physiologically relevant loading conditions. The results indicated that the TO construct exhibited higher ultimate load and biomechanical performance as compared to the CAD construct, suggesting that TO is a viable approach for the design of such patient-specific bone plates. The TO plate also distributed stress more evenly over the screws, likely resulting in more durable constructs and improved anatomical conformity while reducing the risk of screw and plate failure during cyclic loading. Although differences existed between finite element analysis and experimental testing, this study demonstrated that finite element modelling can be used as a reliable method for evaluating and optimizing plates for SCFE patients. In addition to enhancing the mechanical performance of patient-specific fixation plates, the utilization of TO in plate design may also improve the surgical outcome and decrease the recovery time by reducing the plate and incision sizes.

Design considerations for patient-specific bone fixation plates: a literature review.

In orthopedic surgery, patient-specific bone plates are used for fixation when conventional bone plates do not fit the specific anatomy of a patient. However, plate failure can occur due to a lack of properly established design parameters that support optimal biomechanical properties of the plate.This review provides an overview of design parameters and biomechanical properties of patient-specific bone plates, which can assist in the design of the optimal plate.A literature search was conducted through PubMed and Embase, resulting in the inclusion of 78 studies, comprising clinical studies using patient-specific bone plates for fracture fixation or experimental studies that evaluated biomechanical properties or design parameters of bone plates. Biomechanical properties of the plates, including elastic stiffness, yield strength, tensile strength, and Poisson's ratio are influenced by various factors, such as material properties, geometry, interface distance, fixation mechanism, screw pattern, working length and manufacturing techniques.Although variations within studies challenge direct translation of experimental results into clinical practice, this review serves as a useful reference guide to determine which parameters must be carefully considered during the design and manufacturing process to achieve the desired biomechanical properties of a plate for fixation of a specific type of fracture.

The development of a glucose prediction model in critically ill patients.

PURPOSE: The aim of the current study is to develop a prediction model for glucose levels applicable for all patients admitted to the ICU with an expected ICU stay of at least 24 h. This model will be incorporated in a closed-loop glucose system to continuously and automatically control glucose values. METHODS: Data from a previous single-center randomized controlled study was used. All patients received a FreeStyle Navigator II subcutaneous CGM system from Abbott during their ICU stay. The total dataset was randomly divided into a training set and a validation set. A glucose prediction model was developed based on historical glucose data. Accuracy of the prediction model was determined using the Mean Squared Difference (MSD), the Mean Absolute Difference (MAD) and a Clarke Error Grid (CEG). RESULTS: The dataset included 94 ICU patients with a total of 134,673 glucose measurements points that were used for modelling. MSD was 0.410 ± 0.495 for the model, the MAD was 5.19 ± 2.63 and in the CEG 99.8% of the data points were in the clinically acceptable regions. CONCLUSION: In this study a glucose prediction model for ICU patients is developed. This study shows that it is possible to accurately predict a patient's glucose 30 min ahead based on historical glucose data. This is the first step in the development of a closed-loop glucose system.

Healthcare failure mode effect analysis of a miniaturized extracorporeal bypass circuit.

BACKGROUND: The introduction of new and more advanced technology in healthcare occurs with an increasing speed. Therefore, more attention is needed for safety evaluation of new devices or techniques from an end-user perspective, especially when (inter-) national perfusion safety standards are lacking. A recently increased awareness of the safety risks as a consequence of technical or human error has provoked interest in optimisation of perfusion methodology and devices. To prevent or reduce the severity or likelihood of failures of new technology, 'failure mode effect analysis' is a proven proactive technique. When it is used as a qualitative analysis for possible hazards in patient treatment associated with the use of medical devices, it's called healthcare failure mode effect analysis (hFMEA). METHODS: To evaluate the safety of the Extra Corporeal Circulation Optimized (ECCO, Sorin Group, Mirandola, Italy) miniaturized bypass circuit, hFMEA was used. A multi disciplinary team that consisted of two clinical perfusionists, a clinical physicist, a clinical physicist trainee and a technician has performed this analysis. RESULTS: The hFMEA demonstrated that failure of the bubble sensor for the electric remote clamping system on the arterial line (Figure 1), activated by air passing the venous bubble trap, had the highest risk score of all failure modes. This has led to the implementation of an extra low-level sensor in the system to prevent air passing through into the centrifugal pump. The hFMEA has also indicated that extra individual simulation training is needed for handling critical failures during the use of the miniature bypass system. CONCLUSION: Early identification of possible technology failures in any process or device can avoid adverse patient outcomes. The technique of hFMEA is a valuable tool in evaluating the use of high-risk apparatus, such as an extracorporeal bypass system, in patient treatment in order to increase patient safety.

Application of current guidelines for chest compression depth on different surfaces and using feedback devices: a randomized cross-over study.

BACKGROUND: Current cardiopulmonary resuscitation (CPR)-guidelines recommend an increased chest compression depth and rate compared to previous guidelines, and the use of automatic feedback devices is encouraged. However, it is unclear whether this compression depth can be maintained at an increased frequency. Moreover, the underlying surface may influence accuracy of feedback devices. We investigated compression depths over time and evaluated the accuracy of a feedback device on different surfaces. METHODS: Twenty-four volunteers performed four two-minute blocks of CPR targeting at current guideline recommendations on different surfaces (floor, mattress, 2 backboards) on a patient simulator. Participants rested for 2 minutes between blocks. Influences of time and different surfaces on chest compression depth (ANOVA, mean [95% CI]) and accuracy of a feedback device to determine compression depth (Bland-Altman) were assessed. RESULTS: Mean compression depth did not reach recommended depth and decreased over time during all blocks (first block: from 42 mm [39-46 mm] to 39 mm [37-42 mm]). A two-minute resting period was insufficient to restore compression depth to baseline. No differences in compression depth were observed on different surfaces. The feedback device slightly underestimated compression depth on the floor (bias -3.9 mm), but markedly overestimated on the mattress (bias +12.6 mm). This overestimation was eliminated after correcting compression depth by a second sensor between manikin and mattress. CONCLUSION: Strategies are needed to improve chest compression depth, and more than two providers should alternate with chest compressions. The underlying surface does not necessarily adversely affect CPR performance but influences accuracy of feedback devices. Accuracy is improved by a second, posterior, sensor.

Simulation of the artefact of an iodine seed placed at the needle tip in MRI-guided prostate brachytherapy.

The purpose of this research is to study the influence of different needle materials on the artefact of a prostate brachytherapy iodine seed, placed at the needle tip, in MRI (magnetic resonance imaging)-guided prostate brachytherapy. For this research simulations were performed. The simulations showed that with the currently available MRI compatible titanium needles, determination of the exact seed position is difficult, because of the large artefact at the needle tip. This hampers accurate MRI-guided seed delivery. When a plastic needle is used, the image disturbance is caused by the artefact of the iodine seed alone. When a gradient echo sequence is used, the middle of the seed artefact corresponds well with to middle of the real seed position. With the scan parameters we used this deviation was less than 0.4 mm compared to 1.5 mm when a titanium needle is used.

Development of a tapping device: a new needle insertion method for prostate brachytherapy.

The purpose of this study is to develop and test a tapping device for needle insertion for prostate brachytherapy. This device will tap the needle into the prostate with a certain, well-defined, amount of momentum, instead of the currently used method of pushing the needle. Because of the high needle insertion velocity, we expect prostate motion and deformation to be less compared to current methods. We measured the momentum that is applied when manually tapping the needle into the prostate and found a mean momentum of 0.50 +/- 0.07 N s. The tapping device is pneumatically driven and we found that the delivered momentum increased linearly with the applied air pressure. The efficacy of the tapping device was tested on a piece of beef, placed on a freely moving and rotating platform. A significant correlation was found between the applied pressure and the rotation and displacement of the beef. Displacements and rotations were minimal for the highest pressure (4 bar) and amounted to only 2 mm and 6 degrees, respectively. Higher air pressures will further reduce displacements and rotations.