Design of mulitlevel OLF approach ("V"-shaped decompressive laminoplasty) based on 3D printing technology.

PURPOSE: To introduce a new surgical approach to the multilevel ossification of the ligamentum flavum (OLF) aided by three-dimensional (3D) printing technology. METHODS: A multilevel OLF patient (male, 66 years) was scanned using computed tomography (CT). His saved DICOM format data were inputted to the Mimics14.0 3D reconstruction software (Materialise, Belgium). The resulting 3D model was used to observe the anatomical features of the multilevel OLF area and to design the surgical approach. At the base of the spinous process, two channels were created using an osteotomy bilaterally to create a "V" shape to remove the bone ligamentous complex (BLC). The decompressive laminoplasty using mini-plate fixation was simulated with the computer. The physical model was manufactured using 3D printing technology. The patient was subsequently treated using the designed surgery. RESULT: The operation was completed successfully without any complications. The operative time was 90 min, and blood loss was 200 ml. One month after the operation, neurologic function was recovered well, and the JOA score was improved from 6 preoperatively to 10. Postoperative CT scanning showed that the OLF was totally removed, and the replanted BLC had not subsided. CONCLUSION: 3D printing technology is an effective, reliable, and minimally invasive method to design operations. The technique can be an option for multilevel OLF surgical treatment. This can provide sufficient decompression with minimum damage to the spine and other intact anatomical structures.

Plate versus intramedullary nail fixation in the treatment of humeral shaft fractures: an updated meta-analysis.

BACKGROUND: Regarding the treatment of humeral shaft fractures, the choice of plating or intramedullary nailing remains controversial. Previous randomized controlled trials and meta-analyses failed to draw a unanimous conclusion. To guide clinical decision making, we conducted an updated meta-analysis on the optimal treatment of humeral shaft fractures. METHODS: We identified eligible studies published from 1969 to July 2011 using the Cochrane Library; Cochrane Bone, Joint and Muscle Trauma Group; MEDLINE; Embase; OVID; and Google Scholar and manually searched the references of relevant studies. Randomized controlled trials that compared nailing and plating in the treatment of humeral shaft fractures were included. After the methodologic assessment, available data were extracted and statistically reviewed. The primary outcomes were nonunion, delayed union, postoperative infection, reoperation, and radial nerve palsy. The secondary outcomes were restriction of shoulder motion, shoulder impingement, iatrogenic fracture comminution, and implant failure. RESULTS: We included 10 studies comparing plating and nailing in patients with humeral shaft fractures, comprising 439 participants. Plating reduced the risk of shoulder impingement and shoulder restriction in comparison with nailing. Regarding reoperation risk, a secondary sensitivity analysis showed the finding favoring plating over nailing remained unstable. Otherwise, no significant differences were found in postoperative infection, nonunion, delayed union, radial nerve palsy, iatrogenic fracture comminution, and implant failure between groups. CONCLUSIONS: On the basis of current evidence, both plating and nailing can achieve a similar treatment effect on humeral shaft fractures, but plating may reduce the occurrence of shoulder problems. Randomized controlled trials with larger sample sizes using appropriate blinding methods are needed to confirm these findings. LEVEL OF EVIDENCE: Level II, Meta-analysis of prospective comparative trials.

In silico biomechanical analysis of poller screw-assisted small-diameter intramedullary nail in the treatment of distal tibial fractures.

Objective: To evaluate the biomechanical effects of Poller screws (PS) combined with small-diameter intramedullary nails in the treatment of distal tibial fractures at different locations and on different planes. Methods: Nine finite element (FE) models were used to simulate the placement of the intramedullary nail (IMN) and the PS for distal tibial fractures. Structural stiffness and interfragmentary motion (IFM) through the fracture were investigated to assess the biomechanical effects of the PS. The allowable stress method was used to evaluate the safety of the construct. Results: With the axial load of 500 N, the mean axial stiffness of IMN group was 973.38 ± 95.65 N/mm, which was smaller than that at positions A and B of the coronal group and sagittal group (p < 0.05). The shear IFM of the IMN group was 2.10 ± 0.02 mm, which were smaller than that at positions A and B of the coronal group and sagittal group (p < 0.05). Under physiological load, the stresses of all internal fixation devices and the nail-bone interface were within a safe range. Conclusion: In the treatment of distal tibial fractures, placing the PS in the proximal fracture block can obtain better biomechanical performance. The IMN fixation system can obtain higher structural stiffness and reduce the IFM of the fracture end by adding PS.

Optimal Design and Biomechanical Analysis of a Biomimetic Lightweight Design Plate for Distal Tibial Fractures: A Finite Element Analysis.

The treatment of fractures of the distal tibia can be problematic due to the insubstantial soft-tissue covering this part of the anatomy. This study investigates a novel strategy for minimally invasive plate osteosynthesis of distal tibia fractures called bionic lightweight design plating. Following the structure of the animal trabecular bone, we utilized topological mathematical methods to redesign the material layout of the internal fixation device to fulfill the desired lightweight design within given boundary conditions. The results showed that this method can maintain the same stability of the construct as the original plate after a reduction in the original volume by 30%, and the differences in strain energy of plates and maximum node displacement of constructs between the constructs [RP construct vs. LP construct] were not statistically significant (p > 0.05). In the safety assessment of the constructs, the peak stress of plates between constructs was found to not be statistically significantly different under a doubled physiological load (p > 0.05). The average stress of the plates' elements exceeding the allowable stress was analyzed, and no statistically significant differences were found between the two constructs under axial compression stress conditions (p > 0.05). The average stress of the plates' elements in the redesigned plating construct under torsional stress conditions was 3.08% less than that of the locked plating construct (p < 0.05). Under the double physiological load condition, 89% of the elements of the plate in the redesigned plating construct and 85% of the elements of the plate in the locked plating construct were lower than the maximum safe stress of the plate, which was 410 MPa (secondary allowable stresses). That reminds us the topology optimization offer a possible way to improve the capacity of soft tissue protection while ensuring the safety of the RP construct by reducing the volume of the implants.

Optimal design and biomechanical analysis of sandwich composite metal locking screws for far cortical locking constructs.

In the interests of more flexible and less stiff bridge constructs to stimulate bone healing, the technique of far cortical locking has been designed to improve locked plating constructs in terms of stress concentration, stress shielding, and inhibition of issues around fracture healing. However, far cortical locking screws currently lack objective designs and anti-fatigue designs. This study investigates an optimization algorithm to form a special locking screw composed of various metals, which can theoretically achieve the maintenance of the excellent mechanical properties of far cortical locking constructs in terms of fracture internal fixation, while maintaining the biomechanical safety and fatigue resistance of the structure. The numerical results of our study indicate that the maximum von Mises stress of the optimized construct is less than the allowable stress of the material under each working condition while still achieving sufficient parallel interfragmentary motion. Numerical analysis of high cycle fatigue indicates that the optimized construct increases the safety factor to five. A high cycle fatigue test and defect analysis indicates that the sandwich locking constructs have better fatigue resistance. We conclude that the sandwich locking construct theoretically maintains its biomechanical safety and fatigue resistance while also maintaining excellent mechanical properties for fracture internal fixation.

Biomechanical assessment of screw safety between far cortical locking and locked plating constructs.

With the emerging concerns for more flexible and less stiff bridge constructs in the interest of stimulating bone healing, the technique of far cortical locking has been designed to reduce the stiffness of locked plating (LP) constructs while retaining construct strength. This study utilized simulation with diaphyseal bridge plating biomechanical models to investigate whether far cortical locking causes larger screw fracture risk than LP during rehabilitation. The fracture risk of the screws in the far cortical locking constructs increases in the non-osteoporotic and osteoporotic diaphysis compared with the screws in the LP constructs.

Upregulation of FTX Promotes Osteosarcoma Tumorigenesis by Increasing SOX4 Expression via miR-214-5p.

BACKGROUND: Long-chain non-coding RNA (LncRNA) plays a key role in the biological processes of tumors. LncRNA-FTX has been the invasion of tumors. However, its function and mechanism in osteosarcoma have not been studied. METHODS: qRT-PCR was measured the expression levels of FTX and miR-214-5p in osteosarcoma. The protein levels of SRY-related HMG box transcription factor 4 (SOX4) were detected by Western Blot. Cholecystokinin (CCK-8) assay, cell colony formation and Transwell assay, Annexin V-FITC/PI assay were analyzed the effects of FTX and miR-214-5p on cell proliferation, cell invasion and apoptosis. The relationship between FTX, miR-214-5p and SOX4 was analyzed by bioinformatics analysis and Luciferase. The tumor changes in mice were detected by vivo experiments in nude mice. RESULTS: The expression levels of FTX were increased in osteosarcoma tissues and cell lines and negatively correlated with the expression levels of miR-214-5p. FTX could modulate the expression of miR-214-5p in osteosarcoma cell lines. sh-FTX inhibited the growth and metastasis of osteosarcoma. FTX could regulate the growth of osteosarcoma through miR-214-5p. The knockdown of miR-214-5p reversed the inhibitory effect of sh-FTX on osteosarcoma cell proliferation and growth in mice. Furthermore, FTX regulated the expression of SOX4 by acting as a sponge of miR-214-5p in osteosarcoma. CONCLUSION: FTX could promote proliferation, invasion and inhibited apoptosis by regulating miR-214-5p/SOX4 axis in osteosarcoma, suggesting that FTX might be a potential target for osteosarcoma treatment.

The effect of rotational degree and routine activity on the risk of collapse in transtrochanteric rotational osteotomy for osteonecrosis of the femoral head-a finite element analysis.

To explore the mechanical mechanism and provide preoperative planning basis for transtrochanteric rotational osteotomy (TRO) procedure, a joint-preserving procedure for osteonecrosis of the femoral head. Eleven TRO finite element femurs with the most common types of necrosis were analyzed under multi-loading conditions. Thereafter, we made a comprehensive evaluation by considering the anatomy characters, daily activities, and risk indicators contain necrosis expansion trend, necrotic blood supply pressure, and the risk of fracture. The risk of fracture (ROF) is the lowest when standing on feet and increases gradually during normal walking and walking upstairs and downstairs. Compared with posterior rotation, rotating forward keeps more elements at low risk. Additionally, the correlation analysis shows it has a strong negative correlation (R2 = 0.834) with the average modulus of the roof. TRO finally decreased the stress and energy effectively. However, the stress and strain energy arise when rotated posteriorly less than 120°. The comprehensive evaluation observed that rotating forward 90°could reduce the total risks to 64%. TRO is an effective technique to prevent collapse. For the anterior and superior large necrosis, we recommend to rotate forward 60° to 90° (more efficient) or backward 180°. The methodology followed in this study could provide accurate and personalize preoperative planning. Graphical Abstract A proximal femur was reconstructed and modified using Mimics from a series of computed tomography. The models were meshed after solidified and performed different osteotomy, and then assigned material based on the Hounsfield Unit from CT images. Finally, 44 different TRO finite element femurs were analyzed under multi-loading conditions and evaluated comprehensively.

Comparison of conventional reconstruction plate versus direct metal laser sintering plate: an in vitro mechanical characteristics study.

BACKGROUND: Additive manufacturing (AM) technology has helped to achieve several advances in the medical field, particularly as far as fabrication of implants is concerned. But the application of direct metal laser sintering (DMLS) bone plate is quite limited due to the indeterminate mechanical property. The purposes of this study were to characterize the biomechanical properties of the polished DMLS reconstruction plate and to compare these with the properties of commonly applied implants and to find whether the mechanical performance of DMLS plate meets the requirements for clinical application. METHODS: In this study, we fabricated two groups of plates by DMLS and computer numerical control (CNC) techniques. After that, we polished all samples and investigated their roughness, components, hardness, static bending, and torsional performance. Moreover, cyclic bending tests and fractographic analysis were conducted. Statistical comparisons of the group by means of monotonic test data were made, and a qualitative comparison was performed to assess failures in fatigue. RESULTS: We found no differences in surface roughness or components after polishing, but the DMLS plate hardness is 7.42% (p < 0.01) greater than that of the CNC plates. Compared with the CNC plates, the DMLS plate static bending and torsional performance were significantly greater. In a dynamic test, the DMLS plates survived 106, 106, 32,731, and 33,264 cycles under 0.6, 0.8, 0.9, and 1 kN cyclic loads, respectively, while the CNC plates survived 106, 106, 106, and 283,714 cycles. CONCLUSIONS: These results indicate that the mechanical performances of the DMLS plate are stronger, and the strength under fatigue tests is sufficient. DMLS implant has great potential and may become a better choice for clinical use in the future. However, direct application of these AM instruments in the operating room requires further validation including animal and clinical experiment.

Biomechanical comparison of conventional and optimised locking plates for the fixation of intraarticular calcaneal fractures: a finite element analysis.

Intraarticular calcaneal fractures can result in poor prognosis. Although operative fixation can improve the functional outcomes in most cases, surgical complications such as loss of reduction and wound healing problems may increase the risk of reoperation. Hence, this study aimed to design calcaneal locking plate with a lower profile and better biomechanical performance   and to compare the redesigned plate with the traditional calcaneal plate via the finite element method. A Sanders' type II-C intraarticular calcaneal fracture was simulated. Two fixation models utilising the branch-like calcaneal locking plate and the full plate were constructed. Topology optimisation was conducted to generate a new calcaneal plate design. A biomechanical comparison among the three groups of plates was performed using the finite element method. For the fracture simulated in this study, the optimised plate was superior to the traditional plate in terms of fixation stability and safety but was reduced in volume by approximately 12.34%. In addition, more rational stress distributions were observed in the redesigned plate, underscoring the superiority of this new design in terms of fatigue strength. These results demonstrate that the topology optimisation can be used to design a new implant with a minimised profile and no loss of fixation stability.

Impact of spatial characteristics in the left stenotic coronary artery on the hemodynamics and visualization of 3D replica models.

Cardiovascular disease has been the major cause of death worldwide. Although the initiation and progression mechanism of the atherosclerosis are similar, the stenotic characteristics and the corresponding medical decisions are different between individuals. In the present study, we performed anatomic and hemodynamic analysis on 8 left coronary arterial trees with 10 identified stenoses. A novel boundary condition method had been implemented for fast computational fluid dynamics simulations and patient-specific three-dimensional printed models had been built for visualizations. Our results suggested that the multiple spatial characteristics (curvature of the culprit vessel multiplied by an angle of the culprit's vessel to the upstream parent branch) could be an index of hemodynamics significance (r = -0.673, P-value = 0.033). and reduction of the maximum velocity from stenosis to downstream was found correlated to the FFRCT (r = 0.480, p = 0.160). In addition, 3D printed models could provide accurate replicas of the patient-specific left coronary arterial trees compare to virtual 3D models (r = 0.987, P-value < 0.001). Therefore, the visualization of the 3D printed models could help understand the spatial distribution of the stenoses and the hand-held experience could potentially benefit the educating and preparing of medical strategies.

Naringin protects myocardial cells from doxorubicin­induced apoptosis partially by inhibiting the p38MAPK pathway.

Doxorubicin (DOX) has been widely used to treat cancers as a first­line antitumor drug. However, it causes severe, irreversible, dose­dependent cardiotoxicity. To evaluate the protective effects of naringin (NRG) on cardiotoxicity, the authors investigated the molecular mechanism of the p38MAPK signaling pathway. H9c2 cells were treated for 24 h by using 5 µmol/l DOX without or with being pretreated by 1 µM NRG for 150 min or by 3 µM SB203580 for 60 min. Cell viability was detected by cell counting kit­8 assay. Intracellular reactive oxygen species (ROS) levels were detected based on the oxidative conversion of 2',7'­dichlorfluorescein­diacetate (cell­permeable) to dichlorofluorescein (fluorescent). The expression of p38MAPK was determined by western blotting. The expression level of p­p38MAPK in H9c2 cells, which was significantly increased by exposure to 5 µM DOX for 60 min (P<0.01), was significantly decreased by pretreatment with 1 µM NRG for 150 min beforehand (P<0.01). The viability of H9c2 cells pretreated for 150 min with 1 µM NRG was significantly enhanced compared with that using DOX directly (P<0.01). Intracellular ROS levels were significantly reduced by being pretreated with 1 µM NRG for 150 min or with 3 µM SB203580 for 60 min before the cells were exposed to 5 µM DOX. Collectively, NRG protected H9c2 cells against the cardiotoxicity induced by DOX through suppressing the expression and activity of the p38MAPK pathway. The findings provided valuable evidence for the possible use of NRG to relieve DOX­induced cardiotoxicity.

[Finite element modeling of material property assignment based on CT gray value and its application in simulation of osteotomy for deformities].

OBJECTIVE: To explore a new method for finite element modeling to achieve material property assignment based on in situ CT gray value in simulated osteotomies for deformities. METHODS: A CT scan dataset of the lower limb of a patient with extorsion deformity was obtained for three-dimensional reconstruction using Mimics software and preparing a solid model. In the CAD software, the parameters for osteotomy simulation were defined including the navigation axis, rotation angle and reference plane. The tibia model was imported to the FEA pre-processing software for meshing procedure and then exported to Mimics. All the segments of the tibia meshed model were assigned uneven material properties based on the relationship between CT gray values and material properties in the Mimics software. Finally, all the segments of the tibia model, reference axis and reference plane were assembled in the pre-processing software to form a full finite element model of a corrected tibia, which was submitted to resolver for biomechanical analysis. RESULTS: The tibia model established using our modeling method had inhomogeneous material properties based on CT gray values, and was available for finite element analysis for the simulation of osteotomy. CONCLUSIONS: The proposed finite element modeling method, which retains the accuracy of the material property assignment based on CT gray value, can solve the reposition problem commonly seen in modeling via the routine method of property assignment and provides an efficient, flexible and accurate computational biomechanical analysis method for orthopedic surgery.

Patient-specific geometrical modeling of orthopedic structures with high efficiency and accuracy for finite element modeling and 3D printing.

We improved the geometrical modeling procedure for fast and accurate reconstruction of orthopedic structures. This procedure consists of medical image segmentation, three-dimensional geometrical reconstruction, and assignment of material properties. The patient-specific orthopedic structures reconstructed by this improved procedure can be used in the virtual surgical planning, 3D printing of real orthopedic structures and finite element analysis. A conventional modeling consists of: image segmentation, geometrical reconstruction, mesh generation, and assignment of material properties. The present study modified the conventional method to enhance software operating procedures. Patient's CT images of different bones were acquired and subsequently reconstructed to give models. The reconstruction procedures were three-dimensional image segmentation, modification of the edge length and quantity of meshes, and the assignment of material properties according to the intensity of gravy value. We compared the performance of our procedures to the conventional procedures modeling in terms of software operating time, success rate and mesh quality. Our proposed framework has the following improvements in the geometrical modeling: (1) processing time: (femur: 87.16 ± 5.90 %; pelvis: 80.16 ± 7.67 %; thoracic vertebra: 17.81 ± 4.36 %; P < 0.05); (2) least volume reduction (femur: 0.26 ± 0.06 %; pelvis: 0.70 ± 0.47, thoracic vertebra: 3.70 ± 1.75 %; P < 0.01) and (3) mesh quality in terms of aspect ratio (femur: 8.00 ± 7.38 %; pelvis: 17.70 ± 9.82 %; thoracic vertebra: 13.93 ± 9.79 %; P < 0.05) and maximum angle (femur: 4.90 ± 5.28 %; pelvis: 17.20 ± 19.29 %; thoracic vertebra: 3.86 ± 3.82 %; P < 0.05). Our proposed patient-specific geometrical modeling requires less operating time and workload, but the orthopedic structures were generated at a higher rate of success as compared with the conventional method. It is expected to benefit the surgical planning of orthopedic structures with less operating time and high accuracy of modeling.

[Internal fixation surgery planning for complex tibial plateau fracture based on digital design and 3D printing].

OBJECTIVE: To investigate the application of 3D printing and digital technology in preoperative assessment and planning of internal fixation surgery for complex tibial plateau fracture. METHODS: Complex tibial plateau fractures and commonly used plates for tibial plateau were imaged using computed tomography (CT) to reconstruct the 3D fracture and plate models. The 3D models were used to perform virtual reduction and preoperative planning of internal fixation surgery with the most appropriate plates assisted by the 3D library of plates. According to the optimal plan, the 3D physical models of tibial plateau fractures and plates were 3D printed to simulate internal fixation operation. The effects of internal fixation were compared between the virtual surgery and the simulated surgery based on the 3D models. RESULTS: The effects of internal fixation in the simulated surgery based on the 3D models were consistent with those of the virtual surgery. No significant difference was found in the screw length between the two surgeries. CONCLUSION: The combination of 3D printing and digital design can improve the effects of internal fixation for complex tibial plateau fractures.

Improved accuracy of 3D-printed navigational template during complicated tibial plateau fracture surgery.

This study was aimed to improve the surgical accuracy of plating and screwing for complicated tibial plateau fracture assisted by 3D implants library and 3D-printed navigational template. Clinical cases were performed whereby complicated tibial plateau fractures were imaged using computed tomography and reconstructed into 3D fracture prototypes. The preoperative planning of anatomic matching plate with appropriate screw trajectories was performed with the help of the library of 3D models of implants. According to the optimal planning, patient-specific navigational templates produced by 3D printer were used to accurately guide the real surgical implantation. The fixation outcomes in term of the deviations of screw placement between preoperative and postoperative screw trajectories were measured and compared, including the screw lengths, entry point locations and screw directions. With virtual preoperative planning, we have achieved optimal and accurate fixation outcomes in the real clinical surgeries. The deviations of screw length was 1.57 ± 5.77 mm, P > 0.05. The displacements of the entry points in the x-, y-, and z-axis were 0.23 ± 0.62, 0.83 ± 1.91, and 0.46 ± 0.67 mm, respectively, P > 0.05. The deviations of projection angle in the coronal (x-y) and transverse (x-z) planes were 6.34 ± 3.42° and 4.68 ± 3.94°, respectively, P > 0.05. There was no significant difference in the deviations of screw length, entry point and projection angle between the ideal and real screw trajectories. The ideal and accurate preoperative planning of plating and screwing can be achieved in the real surgery assisted by the 3D models library of implants and the patient-specific navigational template. This technology improves the accuracy and efficiency of personalized internal fixation surgery and we have proved this in our clinical applications.

[Finite element analysis of the initial stability of subtalar arthrodesis with double-screw fixation].

OBJECTIVE: To assess the optimal configuration of double-screw fixation for subtalar arthrodesis using finite element analysis. METHODS: Three-dimensional finite element double-screw models of subtalar arthrodesis were reconstructed using Mimics 13.0, Geomagic 10.0 and solid works software based on the 3-D images of the volunteer's right foot. The external and internal rotation torques of 4 N·m were applied, and the micromotion at the bone-to-bone interface were measured to evaluate the initial stability of subtalar arthrodesis. RESULTS: A neck screw plus an anterolateral dome screw was the most stable model. The peak micromotion at the fusion site of this fixation configuration were 41.67mnplus;0.49 and 42.64mnplus;0.75 µm in response to the respectively. A neck screw plus a posteromedial dome screw was the least stable model, with peak micromotion at the bone-to-bone interface of 61.76mnplus;1.00 and 62.32mnplus;0.90 µm, respectively. CONCLUSION: A neck screw plus an anterolateral dome screw is the best fixation configuration while a neck screw plus a posteromedial screw provides the least stability of subtalar arthrodesis. Three-dimensional finite element models allow effective preoperative planning of the screw number and placement.