Gender differences in ethmoid sinus morphology_ 3D reconstruction of computed tomographic images.

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 ± 2.1 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). CONCLUSION: This 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.

Accuracy of digital impressions for three-unit and four-unit implant supported fixed dental prostheses using a novel device.

Background/ purpose: Accuracy of digital implant impressions was considered questionable due to the lack of anatomical reference points between implants and the similarities in scan body morphology, which lead to the purpose of this research is to propose a simple and convenient technique to improve the accuracy of scanning. Materials and methods: Four implant analogues (teeth: 15, 17, 24, and 27) were inserted into a stone model of a partially edentulous maxilla; two implants were inserted on each side, creating a three-unit span and a four-unit span. The model was scanned using a 3Shape E4 dental laboratory scanner for reference and a TRIOS 3 intraoral scanner for testing. Each side was scanned 10 times, both with and without the novel device attached to the scan bodies. The trueness and precision of interimplant distances (linear deviations), and interimplant angulations (angle deviations) between the scan bodies were determined using software. A Mann-Whitney U test was used to determine statistical differences between subgroups. Results: Significant differences were discovered in the trueness of angular deviations (-0.20° ± 0.15° vs. -0.01° ± 0.11º) and precision of linear deviations (11.14 ± 6.35 vs. 3.10 ± 2.14 µm) for the four-unit groups. Conclusion: The novel device significantly improved scanning accuracy for a four-unit groups (approximately 22.93 mm) compared to three-unit groups.

Biomechanical characteristics of self-expanding sinus stents during crimping and deployment_A comparison between different biomaterials.

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.

Difference analysis of the glenoid centerline between 3D preoperative planning and 3D printed prosthesis manipulation in total shoulder arthroplasty.

INTRODUCTION: 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. MATERIALS AND METHODS: 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. 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). CONCLUSION: 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°).

Effect of Fillets on Mechanical Properties of Lattice Structures Fabricated Using Multi-Jet Fusion Technology.

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.

Gender differences in femoral trochlea morphology.

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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. LEVEL OF EVIDENCE: III.

Design and application of personalized surgical guides to treat complex tibial plateau malunion.

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.

How do lateral hinge and distraction affect three-dimensional rotation in open wedge high tibial osteotomy?

BACKGROUND: Open-wedge high tibial osteotomy (OWHTO) has extensively been used for the correction of medial knee osteoarthritis. The proximal tibia is osteotomized and distracted to enable the rotation of tibial fragments around the lateral hinge. Both, wedge inclination on the medial side and saw progression near the lateral cortex determine the hinge orientation. This study focused on the interaction between hinge orientation and distraction sites on the coronal, sagittal, and horizontal planes of the distracted plateau. METHODS: Three parameters of wedge inclination, saw progression, and distraction site (i.e., posterior, middle, and anterior) were systematically varied. Using a three-dimensional (3D)-printing technique, the osteotomized tibiae were manufactured as the specimens for the in vitro experiments. In total, 27 variations (3 × 3 × 3) were tested. After distraction, the specimens were scanned by computed tomography and spatially registered with the original tibia to compare the 3D angles of the distracted plateaus. RESULTS: Coronal rotation is the main purpose of OWHTO; therefore, all the values of the coronal angles were positive and significantly higher than the other two. The sagittal and horizontal angles had relatively similar values. Distraction in the middle site seems to have the least impact on sagittal rotation. Large angles of hinge orientation show the superior ability in adjusting the sagittal rotation than small angles. However, the larger the horizontal angles the greater the wedge inclination. CONCLUSIONS: The wedge inclination, saw progression, and distraction site constitute a complex mechanism that affects 3D rotations of the distracted plateau. The coronal angles are sensitive to hinge orientation and distraction site. The intraoperative planning of manipulating hinge orientation is an effective method to adjust sagittal rotation. A large angle of wedge inclination is an indicator of horizontal rotation, and it should be carefully mitigated to reduce the risk of cracking in the lateral hinge.

Geometric accuracy of an acrylonitrile butadiene styrene canine tibia model fabricated using fused deposition modelling and the effects of hydrogen peroxide gas plasma sterilisation.

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 (H2O2) 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 H2O2 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 EFDM-CT (3D-FDM vs. 3D-CT) were significantly higher than those in EGAS-FDM (3D-GAS vs. 3D-FDM; P < 0.0001). Mean RMS values for EFDM-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 EGAS-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 EFDM-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.

How do osteotomy and distraction affect distraction angles of opening wedge high tibial osteotomy?

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.

Comparison between different screening strategies to determine the statistical shape model of the pelvises for implant design.

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.

Predicting 3D pose in partially overlapped X-ray images of knee prostheses using model-based Roentgen stereophotogrammetric analysis (RSA).

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.

Biomechanical effects of cage positions and facet fixation on initial stability of the anterior lumbar interbody fusion motion segment.

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.

Clinical significance of tissue expression of interleukin-6 in colorectal carcinoma.

BACKGROUND: Although serum interleukin-6 (IL-6) has been associated with the development of colorectal cancer, IL-6 expression in cancer tissues has never been elucidated. The role of the tissue expression of IL-6 in colorectal cancer was investigated to identify any prognostic significance. MATERIALS AND METHODS: One hundred and sixty consecutive patients, whose primary lesions had been resected, were studied. Immunoreactivity of IL-6 in cancerous tissue was measured by immunohistochemical staining; the relationships between the positive expression of IL-6 and both clinicopathological factors and survival were evaluated. RESULTS: Seventy-four specimens expressed IL-6, and this expression correlated with an elevated serum carcinoembryonic antigen level, lymph node metastasis, venous invasion and advanced stage (p < 0.05). IL-6 expression correlated with poor survival (p < 0.05) and was an independent predictor of prognosis. CONCLUSION: Because tissue expression of IL-6 correlates with aggressive colorectal cancer behavior, it may be a useful predictor of prognosis.

Influence of interleukin-6 on the invasiveness of human colorectal carcinoma.

BACKGROUND: Plasma interleukin-6 (IL-6) level correlates with patient survival in colorectal carcinoma and is regarded as a prognostic factor. In this study, the role of IL-6 in colorectal carcinoma proliferation, chemotaxis and invasion was investigated. MATERIALS AND METHODS: Proliferation and invasion were measured in four colorectal carcinoma cell lines. The effect of IL-6 (10, 50, 100 ng/ml) on progression (the ability to grow, adhere, chemotax and invade) was also measured. RESULTS: Physiological (10 ng/ml) and pharmacological (50 and 100 ng/ml) concentrations of IL-6 did not significantly affect growth. However, IL-6 (10 ng/ml) significantly increased attachment to basement membrane (p < 0.05). IL-6 (50 ng/ml) significantly increased the chemotaxis, anchorage-independent growth and invasiveness of SW-480 (one of the four cell lines) (p < 0.05). IL-6 (100 ng/ml) resulted in negative feedback inhibition of these effects. CONCLUSION: IL-6 plays an important role in the progression of colorectal carcinoma.