AbstractBackgroundThe ethmoid sinus (ES) is a three-dimensional (3D) complex structure, a clear understanding of the ES anatomy is helpful to plan intranasal surgery. However, most prior studies use 2D measurements, which may not accurately depict the 3D structure. The current study measured the gender differences in ES morphology based on 3D reconstruction of computed tomography (CT) images.MethodsThe 3D models were reconstructed using CT images. Twenty-one males and 15 females were enrolled in the study. The ES dimensions, including width, height and aspect ratio (AR) of each cutting-plane section, were measured at 10% increments along with the anteroposterior axis of the ES. The gender differences in the above parameters were further evaluated by an independentt-test.ResultsThe width of the ES for males is 12.0 ± 2.1 mm, which was significantly greater than that in females (10.0 ± 2.1 mm). The average height for males is 18.4 ± 3.5 mm, and 18.2 ± 3.4 mm for females. The AR of female (male) is around 0.56 (0.63) for the anterior ES and 0.66 (0.75) for the posterior. There are significant differences between genders in the parameters of width and AR (p < 0.05).ConclusionThis study found that the aspect ratio greatly varies along the length of ES, indicating that the cross-section of the ES in the anterior is closer to an elliptical shape and turns closer to a circular shape near its posterior. There is a significant difference between genders in width and aspect ratio. The results would be helpful to know the complex anatomic details of the ethmoid sinus.

Abstract Background The ethmoid sinus (ES) is a three-dimensional (3D) complex structure, a clear understanding of the ES anatomy is helpful to plan intranasal surgery. However, most prior studies use 2D measurements, which may not accurately depict the 3D structure. The current study measured the gender differences in ES morphology based on 3D reconstruction of computed tomography (CT) images. Methods The 3D models were reconstructed using CT images. Twenty-one males and 15 females were enrolled in the study. The ES dimensions, including width, height and aspect ratio (AR) of each cutting-plane section, were measured at 10% increments along with the anteroposterior axis of the ES. The gender differences in the above parameters were further evaluated by an independent t-test. Results The width of the ES for males is 12.0±2.1mm, which was significantly greater than that in females (10.0±2.1 mm). The average height for males is 18.4±3.5mm, and 18.2±3.4mm for females. The AR of female (male) is around 0.56 (0.63) for the anterior ES and 0.66 (0.75) for the posterior. There are significant differences between genders in the parameters of width and AR (p<0.05) Conclusion This study found that the AR greatly varies along the length of ES, indicating that the cross-section of the ES in the anterior is closer to an elliptical shape and turns closer to a circular shape near its posterior. There is a significant difference between genders in width and AR. The results would be helpful to know the complex anatomic details of the ethmoid sinus.

Abstract The precise creation and control of osteotomy and distraction have been a problem in opening wedge high tibial osteotomy (OWHTO). This study aimed to investigate the impact of the cutting edge of a personalized surgical instrument (PSI) to control the distraction angle, tibial slope, and tibial twist of the distracted tibiae. This study correlated the PSI design with the results of biomechanical tests on wedge inclination (WI), saw progression (SP), and distraction site (DS) of the proximal tibiae, which were systematically varied and three-dimensionally (3D) printed as the specimens. The lateral hinge 3D orientation was determined by the WI and SP. Different DSs deviate from the hinged motion of the distracted tibiae to some extent. The coronal angle, which is the major OWHTO target, is more sensitive to the SP and DS. However, the concurrence of the sagittal and horizontal angles induces undesirable effects on knee biomechanics and potentially risks the lateral hinge. The cutting edge is a key design that serves as the cutting and sawing guide to control the initial cut on the medial tibia (i.e., WI) and the sawing path near the lateral cortex (i.e., SP). Intraoperative planning of manipulating the SP is the most effective method for adjusting the sagittal rotation. A higher WI angle is a determinant factor of the horizontal rotation that must be cautiously mitigated to reduce the risk of lateral hinge cracking and to adjust the patellofemoral contact.

Excessive version and inclination of the glenoid component during total shoulder arthroplasty can lead to glenohumeral instability, early loosening, and even failure. The orientation and position of the central pin determine the version and inclination of the glenoid component. The purpose of this study was to compare the differences in centerline position and orientation obtained using "3D preoperative planning based on the best-fit method for glenoid elements" and the surgeon's manipulation. Twenty-nine CT images of glenohumeral osteoarthritis of the shoulder were reconstructed into a 3D model, and a 3D printer was used to create an in vitro model for the surgeon to drill the center pin. The 3D shoulder model was also used for 3D preoperative planning (3DPP) using the best-fit method for glenoid elements. The in vitro model was scanned and the version, inclination and center position were measured to compare with the 3DPP results. The respective mean inclinations (versions) of the surgeon and 3DPP were −2.63° ± 6.60 (2.87° ± 5.97) and −1.96° ± 4.24 (−3.21° ± 4.00), respectively. There was no significant difference in the inclination and version of the surgeon and 3DPP. For surgeons, the probability of the inclination and version being greater than 10° was 13.8% (4/29) and 10.3% (3/29), respectively. Compared to the 3DPP results, the surgeon's center position was shifted down an average of 1.63 mm. There was a significant difference in the center position of the surgeon and 3DPP (p < 0.05). The central pin drilled by surgeons using general instruments was significantly lower than those defined using 3D preoperative planning and standard central definitions. 3D preoperative planning prevents the version and inclination of the centerline from exceeding safe values (± 10°).

Self-expanding sinus stents are often used in functional endoscopic sinus surgery to treat inflamed sinuses. The PROPEL self-expanding sinus stent offers mechanical support to the sinus cavity to prevent restenosis. The stent is made of a bioabsorbable material (PLGA) that disappears after wound healing. However, complications such as foreign body sensation and severe stent migration/expulsion have been reported after implantation. Little is known about the contact characteristics of self-expanding sinus stents from when the stent is crimped into the insertion device through to deployment into the sinus cavity. This current study developed a test platform to analyze the biomechanical behavior of the stent during this process. Three common bioabsorbable materials, PLGA, PCL and Mg alloy, were evaluated to understand how the choice of material affects the biomechanical characteristics of self-expanding sinus stents. The results showed that the material can have a considerable influence on the contact characteristics during crimping and deployment. When crimped, the PLGA and Mg alloy stents showed much higher plastic strain and contact stress than the PCL stent. When deployed, the PCL stent had the largest contact area (4.3 mm2) and the lowest contact pressure (0.1 MPa) on the inner surface of the sinus canal. The results indicate that PCL could be a suitable choice for self-expanding sinus stents. This current study provides a method for observing the biomechanical characteristics of sinus stents during stent crimping and deployment.

Lattice structures have proven to have excellent mechanical properties in several loading conditions for a wide range of applications and additive manufacturing enables to fabricate these intricate as well as complex structures with exceptional accuracy. However, studies of mechanical properties of these structures in response to torsional and other complex loading are very limited. In this study, three different structures namely gyroid, primitive, and vertical-inclined were designed in cylindrical shape samples and additively manufactured using MultiJet fusion technology. Torsion tests until failure of structures were performed to study mechanical properties including torsional stiffness, energy absorption, and failure modes of structures. In addition, a new method of calculating polar moment of inertia is established taking the non-uniform cross section of the structures into account for accurate calculation of torsional properties. Experimental results indicate that the surface-based gyroid and primitive structures have superior torsional stiffness, energy absorption capacity, and ultimate strength compared to the strut-based vertical-inclined structure. Gyroid structure has almost 9% higher torsional stiffness value than primitive structure and nearly two times higher stiffness than vertical-inclined structure. However, primitive structure showed superior energy absorption capacity of 8 J/mm 3 withstanding a large amount of plastic deformation. In contrast, both gyroid and vertical-inclined structures had lower energy absorption capacity values of 3.72 J/mm 3 and 2.27 J/mm 3 , respectively. Lastly, failure mode of structures revealed that both gyroid and vertical-inclined failed in a brittle manner with fractures at an angle to their longitudinal axis while primitive structure showed ductile mode of failure with fracture perpendicular to its longitudinal axis.

Cellular structures with tailored topologies can be fabricated using additive manufacturing (AM) processes to obtain the desired global and local mechanical properties, such as stiffness and energy absorption. Lattice structures usually fail from the sharp edges owing to the high stress concentration and residual stress. Therefore, it is crucial to analyze the failure mechanism of lattice structures to improve the mechanical properties. In this study, several lattice topologies with fillets were designed, and the effects of the fillets on the stiffness, energy absorption, energy return, and energy loss of an open-cell lattice structure were investigated at a constant relative density. A recently developed high-speed AM multi-jet fusion technology was employed to fabricate lattice samples with two different unit cell sizes. Nonlinear simulations using ANSYS software were performed to investigate the mechanical properties of the samples. Experimental compression and loading–unloading tests were conducted to validate the simulation results. The results showed that the stiffness and energy absorption of the lattice structures can be improved significantly by the addition of fillets and/or vertical struts, which also influence other properties such as the failure mechanism and compliance. By adding the fillets, the failure location can be shifted from the sharp edges or joints to other regions of the lattice structure, as observed by comparing the failure mechanisms of type B and C structures with that of the type A structure (without fillets). The results of this study suggest that AM software designers should consider filleted corners when developing algorithms for generating various types of lattice structures automatically. Additionally, it was found that the accumulation of unsintered powder in the sharp corners of lattice geometries can also be minimized by the addition of fillets to convert the sharp corners to curved edges.

:- In this study, five different auxetic structures were designed into dog bone specimens and printed with approximated similar masses, intended as the constant parameter. These specimens were then simulated by Finite Element Analysis before being subjected to tensile testing. In the simulation, yield stress comparisons between auxetic structures and non-auxetic were analyzed. UTS (Ultimate Tensile Stress) and maximum strain from tensile test results were compared with 3D printed non-auxetic with concentric infill. The results showed agreement between simulation and testing in terms of deformations and failure spots. In the end, simulated auxetic structures showed extensions in yielding limit at a range of 5-20% compared to control. Meanwhile, four out of five tested auxetics were proved to gain increment in UTS value at a range of 25.14%-160.9% and additional maximum strain percentage by 4.1-31.49% compared to non-auxetic with 10.1 MPa and 2.48%, UTS and maximum strain Respectively.

Background Three-dimensional (3D) printing techniques have been used to produce anatomical models and surgical guiding instruments in orthopaedic surgery. The geometric accuracy of the 3D printed replica may affect surgical planning. This study assessed the geometric accuracy of an acrylonitrile butadiene styrene (ABS) canine tibia model printed using fused deposition modelling (FDM) and evaluated its morphological change after hydrogen peroxide (H 2 O 2 ) gas plasma sterilisation. The tibias of six canine cadavers underwent computed tomography for 3D reconstruction. Tibia models were fabricated from ABS on a 3D printer through FDM. Reverse-engineering technology was used to compare morphological errors (root mean square; RMS) between the 3D-FDM models and virtual models segmented from original tibia images (3D-CT) and between the models sterilised with H 2 O 2 gas plasma (3D-GAS) and 3D-FDM models on tibia surface and in cross-sections at: 5, 15, 25, 50, 75, 85, and 95% of the tibia length. Results The RMS mean ± standard deviation and average positive and negative deviation values for all specimens in E FDM-CT (3D-FDM vs. 3D-CT) were significantly higher than those in E GAS-FDM (3D-GAS vs. 3D-FDM; P < 0.0001). Mean RMS values for E FDM-CT at 5% bone length (proximal tibia) were significantly higher than those at the other six cross-sections ( P < 0.0001). Mean RMS differences for E GAS-FDM at all seven cross-sections were nonsignificant. Conclusions The tibia models fabricated on an FDM printer had high geometric accuracy with a low RMS value. The surface deviation in E FDM-CT indicated that larger errors occurred during manufacturing than during sterilisation. Therefore, the model may be used for surgical rehearsal and further clinically relevant applications in bone surgery. Graphical abstract

Intra-articular corrective osteotomy can be used to restore the anatomic position of knee surfaces for tibial plateau malunion (TPM) but precise restoration is not easy. The personalized surgical guide (PSG) might improve the TMP outcomes. This study developed a two-staged PSG method to provide registration and drill the bone for subsequent osteotomy. The tests were performed to compare the accuracy the proposed PSG and the conventional guide (Anterior cruciate ligament guide, ACLG). The results showed that the PSG provides better accuracy (0.50 +/- 0.19 mm) than the ACLG (1.58 +/- 0.67 mm). The results show the PSG method is a feasible alternative to the conventional ACLG procedure.

This study aimed to analyze the morphology of the anterior femoral condyle using a quantitative three-dimensional reconstruction method. The morphological data were compared between genders. Computed tomography scans of femurs were taken from 90 healthy subjects and then reconstructed in 3D modeling software. Coaxial cutting planes were created at 10° increments to measure the lateral and medial anterior condylar heights (LACH and MACH, respectively), lateral and medial trochlear groove widths (LTW and MTW, respectively), and for trochlear groove tracking. The absolute values and normalized data were compared between male and female subjects. The sulcus angle and deepest point of the trochlear groove at each cross-section were also analyzed to determine the differences in the depth of the trochlear groove. The absolute dimensions of LACH, MACH, LTW, and MTW were significantly smaller in the female subjects, by 10.5%, 36.9%, 10.3%, and 11.0%, respectively, than in the males (p < 0.05). After normalization, no significant difference was found in the condylar height between the genders. However, the female subjects had a significantly larger value of approximately 7.9% for the normalized trochlear width. Male subjects had greater condylar heights and widths than the female subjects. Although the trajectory of the trochlear groove varied greatly among the subjects, the trochlear groove appeared to be wider and shallower in the female subjects than in the male subjects. These results provide important information for the design of femoral trochlea to fit Asian female patients. III.

BACKGROUNDS:Trigonometric formulae have been derived to correlate the distraction angle (height) and tibial specifications. However, the assumption-induced simplifications are inherent in the formulae such as the rigid tibia and the specific orientations of cutting plane and lateral hinge. This study aimed to evaluated the accuracy of the trigonometric formulae.METHODS:The 3D printed tibiae were used as the specimens for which the hinge orientations and distraction sites were systematically varied. Hinge orientation was determined by wedge inclination of the bone saw into the medial tibia and saw progression near the lateral cortex. The specimens were distracted at different distraction sites to measure the distraction angles that were compared with literature formulae.FINDINGS:In cases of the same distraction height, the wedge inclination, saw progression, and distraction site had various impacts on the coronal angles, indicating that the ideal formula should consider these parameters. Averagely, the predicted angles of the literature formulae were 15% higher than the testing results. The differences in these results may be attributed to the deformable property of the specimen material, non-ideal hinge orientation, and differences in distraction sites. Saw progression and distraction site had greater impacts than wedge inclination on the distraction angle.INTERPRETATION:Variations in three surgical indices constitute a complicated mechanism that affects the 3D hinged rotation of the distracted plateau. The non-middle distraction further deforms the tibial rotation and reduces the accuracy of the trigonometric formulae. The trigonometric formulae might underestimate the distraction angle; thus. Appropriate corrections are necessary for clinical application.

BACKGROUND AND OBJECTIVES:The statistical shape model (SSM) of numerous bones has been used to determine the anatomical representative of the population- or race-specific design for periarticular implants. Whether to include size- and profile-mismatched bones in the SSM calculation is debatable. Therefore, the objective of this study was to characterize the screening strategies for the mismatched bones to improve the SSM calculation.METHODS:The bone database used in this study consisted of 20 pelvises. A systematic four-staged SSM calculation was used to evaluate the accuracy of the predicted SSM shape among the four size- and profile-screening strategies. Additionally, the surface-smoothing effects on the SSM results were investigated. Two comparison indices were used in terms of profile difference and surface smoothness.RESULTS:Significant variations in size and profile existed for the collected bones. By normalizing the aspect ratio of all bones, exclusion of the size-mismatched bones reduced the maximum and root mean square (RMS) error values of the profile difference by 18.9% and 17.5%, respectively. After further excluding the profile-improper bones, normalization reduced the RMS profile difference by 24.1% compared with the non-normalized strategy. Exclusion of the size-improper bones for non-normalized strategy would have reduced the RMS profile difference by 15.4%. After smoothness, the RMS profile difference of SSM was only 6.1% higher than that of the non-smoothness SSM.CONCLUSIONS:The four-stage calculation showed that the most favorable strategy was to normalize bones to the same aspect ratio and exclude improperly shaped bones. The model permitted inclusion of the original characteristics of the bones and preserved their shapes and excluded only significantly improper bones. After SSM calculation, the smoothed process provided satisfaction in quality with a statistically insignificant loss in bone morphology for population- or race-specific designs of implants.

The radiostereometric analysis (RSA) technique has been used to monitor intercomponent position and polyethylene wear after total knee arthroplasty. RSA uses anteroposterior (AP) and mediolateral (ML) X-ray images to predict the three-dimensional (3D) relationship of prostheses. However, overlapping images can potentially reduce the accuracy of the predicted RSA results. Overlapping images often occur from improper poses of the lower limb. This study evaluates the pose-induced errors of knee, ankle and hip joints by taking simulated X-ray images of knee prosthesis. The poses include knee flexion only, knee/dorsal flexion, knee flexion and hip abduction and knee/dorsal flexion and hip abduction. Predicted RSA accuracy and pose-induced effects on the overlapping images are evaluated. Two comparison indices are chosen among the poses: percentage of image overlap and rotational and translational RSA errors. The results show that dorsal flexion induces more image overlap than knee flexion. Hip abduction induces image overlap on the ML rather than on AP view. Knee/dorsal flexion and hip abduction induce the worst image overlap and least RSA accuracy. If dorsal flexion is over 10 degrees, the overlap on images gradually increases and the coverage begins to converge at 30 degrees. RSA accuracy substantially decreases when the coverage is over 20%. Furthermore, RSA error increases by 0.3-10 times when overlapping images occurs on the AP and ML views. In conclusion, dorsal flexion is the predominant factor to induce overlap image and decrease RSA accuracy. During taking X-ray images, the ankle should be kept vertical and only knee flexion allowed to ensure the quality of the projected images and RSA results.

After total knee replacement, the model-based Roentgen stereophotogrammetric analysis (RSA) technique has been used to monitor the status of prosthetic wear, misalignment, and even failure. However, the overlap of the prosthetic outlines inevitably increases errors in the estimation of prosthetic poses due to the limited amount of available outlines. In the literature, quite a few studies have investigated the problems induced by the overlapped outlines, and manual adjustment is still the mainstream. This study proposes two methods to automate the image processing of overlapped outlines prior to the pose registration of prosthetic models. The outline-separated method defines the intersected points and segments the overlapped outlines. The feature-recognized method uses the point and line features of the remaining outlines to initiate registration. Overlap percentage is defined as the ratio of overlapped to non-overlapped outlines. The simulated images with five overlapping percentages are used to evaluate the robustness and accuracy of the proposed methods. Compared with non-overlapped images, overlapped images reduce the number of outlines available for model-based RSA calculation. The maximum and root mean square errors for a prosthetic outline are 0.35 and 0.04 mm, respectively. The mean translation and rotation errors are 0.11 mm and 0.18°, respectively. The errors of the model-based RSA results are increased when the overlap percentage is beyond about 9%. In conclusion, both outline-separated and feature-recognized methods can be seamlessly integrated to automate the calculation of rough registration. This can significantly increase the clinical practicability of the model-based RSA technique.

STUDY DESIGN:An in vitro biomechanical study using porcine lumbar segments as specimens.OBJECTIVE:To evaluate the effects of interbody cage support and endplate strength on the stability of instrumented segments.SUMMARY OF BACKGROUND DATA:The anterior lumbar interbody fusion (ALIF) cage is widely used to restore disc height and support the anterior column. Transpedicle or posterior spinal fusion or facet screw fixation (FSF) can improve the stability of the vertebra-instrumented segments. The cage position can affect the anterior support and initial stability of the ALIF region, but there is no consistent data on its biomechanical effects on ALIF and ALIF/FSF segments.METHODS:Nine variations of 3 instrumentation modes (intact, ALIF, ALIF/FSF) and 3 cage positions (type I, anterolateral; type II, mediolateral; and type III, posteromedial) are tested under 5 lumbar motions. The range of motion and axial displacement are used as comparison indices for the different variations.RESULTS:The cage placement serves as support for the intervertebral loads while the posterior fixation behaves as lever to further enhance the anterior support. At the endplate-cage interfaces, the endplate strength directly affects the cage subsidence. Type III exhibits higher stability for standing due to the greater strength of the endplate in the posterior region. Otherwise, type I consistently has higher stability for all other types of motion.CONCLUSION:The initial stability of the ALIF region is affected by the moment arm and the mechanical strength of the engaged endplates. Type I has greater moment arm and provides more efficient support to the instrumented segments. Endplate strength provides an ability to withstand lumbar loads and suppress the cage subsidence. Bone quality at the endplate-cage interfaces must therefore be cautiously evaluated preoperatively.LEVEL OF EVIDENCE:N/A.

In considering an engineer’s opinion in optimizing a multiresponse problem, attention must be paid to vagueness and hesitancy in revealing his or her perceptions of a fuzzy concept such as “importance” or “excellence.” Recently, the notion of intuitionistic fuzzy sets has been found to be more effective than that of fuzzy sets for dealing with vagueness and hesitancy. However, little research has been done on optimizing multiresponse problems using intuitionistic fuzzy sets. This article focuses on state systems and explores optimization of multiresponse problems with intuitionistic fuzzy sets, in which the importance of each response is given by an engineer as intuitionistic fuzzy set. A novel optimization procedure is proposed that is based on a measure of similarity between intuitionistic fuzzy sets. To demonstrate the efficiency and effectiveness of the proposed method, two case studies are provided–one of plasma-enhanced chemical vapor deposition and the other the copper chemical mechanical polishing.