The endoscopic transnasal approach in management of the sinonasal tumor invading the anterior skull base / 中华耳鼻咽喉头颈外科杂志

Objective: To evaluate the feasibility of the endoscopic transnasal approach (ETA) and to analyze the outcomes and factors of this surgical technique in the management of the tumor invading the anterior skull base. Methods: A retrospective analysis was performed on 42 patients (31 males and 11 females, with mean age of 49 years) with sinonasal tumor invading the anterior skull base, who underwent ETA from June 2015 to April 2019 in Eye, Ear, Nose and Throat Hospital of Fudan University. Pathologically, there were 15 cases of squamous carcinoma (14 patients with T4bN0M0 and 1 patient with T4bN1M0) and 27 of olfactory neuroblastomas with Kadish stage C. Anterior skull base reconstruction was performed using the vascular pedicled nasoseptal mucoperiosteal flap and fascia lata. Brain non-contrast-enhanced CT was performed on the first postoperative day to exclude massive pneumocephalus, relevant brain edema and subarachnoid hemorrhage. Sinonasal contrast-enhanced MR was performed to assess the extent of the tumor removal. Kaplan-Meier analysis was used to calculate the overall survival (OS) and Cox multivariate regression analysis was used to determine the prognostic factors. Results: The mean duration of the surgery was 452 minutes. Total resection was performed in 36 patients (85.7%), subtotal resection in 2 patients (4.8%) with orbital involvement, partial resection in one patient (2.4%) with injury of the internal carotid artery. One patient (2.4%) underwent the second resection because of the tumor residual, two patients (4.8%) with unsure tumor residual. Mean follow-up was 20 months, with 17 months of median follow-up. One-, two-and three-year overall survival was 86.5%, 76.9% and 64.5%, respectively. For squamous carcinoma, one-, two-and three-year overall survival was 86.2%, 86.2% and 57.4%, respectively. For olfactory neuroblastomas, One-, two-and three-year overall survival was 86.9%, 75.3% and 67.8%, respectively. Multivariate analysis showed that tumor residual (P=0.001) and recurrence (P<0.01) were independent prognostic factors for survival. Conclusions: The ETA is safe and feasible in selected patients with sinonasal tumor invading the anterior skull base. Tumor residual and recurrence are independent prognostic factors for survival.

Analysis on related factors of lymph node metastasis and ovary involvement in endometrioid adenocarcinoma / 中华疾病控制杂志

Objective To investigate the related factors of lymph node metastasis and ovary involvement in endometrioid adenocarcinoma. Methods The clinicopathological data of endometrioid adenocarcinoma patients who underwent surgical treatment at the first affiliated hospital of university of science and technology of China from January 2011 to January 2018 were analyzed retrospectively. A total of 189 endometrioid adenocarcinoma were retrieved in the study. Results In the univariate analysis, D-dimer, preoperative plasma fibrinogen and CA125 levels could be elevated in endometrioid adenocarcinoma patients with ovary involvement (all P<0.05). Endometroid adenocarcinoma patients with lymph node metastasis had lower body mass index (BMI) (t=2.133, P=0.040), preoperative plasma fibrinogen, D-dimer, CA125 levels and BMI were higher in patients with lymph node metastasis (all P<0.05). In Logistic regression analysis, D-dimer levels(OR=1.448, 95% CI:1.105-1.898) and preoperative plasma fibrinogen(OR=1.925, 95% CI:1.018-3.640) were elevated in endometrioid adenocarcinoma patients with ovary involvement; Multiparity was the protective factor(OR=0.498, 95% CI: 0.253-0.982) for endometrioid adenocarcinoma patients with lymph node metastasis, but elevated preoperative plasma fibrinogen (OR=2.191, 95% CI: 1.085-4.422) was the risk factor among the patients. Conclusion Increased preoperative plasma fibrinogen or D-dimer levels could be predictors of lymph node metastasis or ovary involvement in endometrioid adenocarcinoma.

Dosimetric superiority of low melting-point lead in the radiotherapy of Gravesspi' ophthalmopathy / 解放军医学杂志

Objective To compare the dosimetric difference between the two beams formed by low melting-point lead (LML) and multileaf collimator (MLC) in orbit radiotherapy, so as to select the one with a lower lens dose for treatment of Graves' ophthalmopathy. Methods Patients with unilateral and bilateral Graves' ophthalmopathy (10 cases each) suitable for radiotherapy were selected for dosimetric comparison. The identical sketching principle of target volume was employed, and the prescribed dose of planning target volume (PTV) was 2000 cGy/10 times. The distribution of radiation field in unilateral group was 3 fields (2 X-ray fields + 1 electron field), and in bilateral group was 4 fields (2 X-ray fields + 2 electron fields), and LML and MLC were employed to form the radiation field. The conformity index (CI) and dose volume histogram (DVH) were compared between the two formation methods of radiation field; the effective penumbra area of the half radiation field formed by the two methods and its influence on the lens dose were analyzed with flushing-free film and dose analysis software. Results The average dose of the affected side lens in MLC unilateral group was 582 ± 34cGy, and of the lens of uninjured side was 160 ± 22cGy, the CI of target volume was 0.69; the average dose of the left and right lens in MLC bilateral group was 591 ± 47cGy and 585 ± 52cGy, respectively, and the CI was 0.67. The average dose of the affected side lens in LML unilateral group was 252 ± 45cGy, and that of the uninjured side lens was 148 ± 19cGy, and the CI was 0.71; the average dose of the left and right lens in LML bilateral group was 247 ± 44cGy and 256 ± 42cGy, respectively, and the CI was 0.68. When the X-ray energy was setup at 4MV and 8MV, the half radiation field was 5cm X 5cm with a depth of 4cm, and the effective penumbra area of LML was 3mm smaller than that of MLC. Conclusion A small radiation area formed by LML may be more appropriate, and it may not only diminish the penumbra of radiation field, also it significantly reduce the irradiation dose imparted to patients' affected side lens.

Assignment and verification on mechanical parameters of soft tissue in finite element analysis / 医用生物力学

Objective To obtain an optimized method of providing hyperelastic parameters of soft tissue, and to promote the simulation accuracy in explicit solution of finite element analysis (FEA) on soft tissue impact test. Methods Compressive properties of soft tissue from six fresh planta were measured. The experimental data were used to calculate the FEA material properties, which were then optimized by Poisson’s ratio. With the same loading and boundary conditions as the experiment, the FEA model was conducted for simulation. The simulation results were verified by both the experimental data and literature data. Results The force-displacement curve of soft tissue presented an exponential growth trend in the in vitro biomechanical experiment. When the compression ratio was under 45%, the FEA simulation result was consistent with the experimental data. When the compression ratio was above 45%, the closer the Poisson’s ratio up to 0.5, the higher the accuracy of FEA simulation result. However, there was a strong linear correlation between the FEA simulation results and experimental data (R2=0.9923) when the Poisson’s ratio was 0.497. Conclusions The simulation result of material parameters in FEA model is preferable in this study. With a lower compression ratio, the simulation results from FEA model are in consistency with the experimental data. Increasing the Poisson’s ratio can promote the simulation accuracy of the FEA model when the compression ratio is high.

Plantar pressure distributions during support phase under different Achilles tensile loads / 医用生物力学

Objective To investigate changes in plantar pressure distributions on forefoot and hindfoot region during the support phase under different Achilles tensile loads. Methods Six fresh frozen human below-knee specimens were used and placed on the material testing machine. The ankles were kept in neutral position and the axial load of 350 N was applied on the specimens. Achilles tensile loads varied from 0 kg to 80 kg (0, 100, 200, 300, 400, 500, 600, 700, 800 N）were applied by weights. Two scales were placed under the forefoot and hindfoot region of the specimen, respectively, to record the pressure under the Achilles tensile loads. Results With the Increasing Achilles tensile force, the pressure on forefoot region was increasing, while the pressure on the hindfoot was decreasing. The percentage of average plantar pressure in forefoot and hindfoot region over the total plantar pressures presented a linear relationship with the Achilles tensile force (P<0.01, R2=0.996). Conclusions The support phase of foot in vitro was simulated and the plantar pressure distributions on forefoot and hindfoot region was investigated in this paper. The result can provide theoretical evidences for some diseases (such as diabetic foot ulcers, metatarsalgia) caused by plantar pressure changes due to Achilles tensile contracture in clinic.

Biomechanical study and clinical choice of different fixation devices to treat femoral fracture / 医用生物力学

Objective To investigate the biomechanical properties of transverse fractured femurs when fixed by TiNi shapememory alloy embracing plate (TiNi SMA), limitedcontact dynamic compression plate (LCDCP) and static interlocking intramedullary nail (SIiN), respectively, so as to provide the theoretical evidence for orthopedic surgeons in clinical application. Methods Eight pairs of cadaveric femurs were used with one side randomly fixed by TiNi SMA and SIiN and the other side fixed by LC-DCP. Then the axial compression test, threepoint bending test, and torsion test were conducted. Results For axial compression test, the strains of TiNi SMA group were greater than those of LC-DCP group and SIiN group (P0.05). The displacements of TiNi SMA group were greater than those of LC-DCP group and SIiN group (P0.05). For three-point bending test, the displacements of TiNi SMA group were greater than those of LC-DCP group and SIiN group (P0.05). For torsion test, the torsion angels of TiNi SMA group were similar to those of SIiN group (P>0.05), but the torsion angles of LC-DCP group were smaller than those of TiNi SMA group（≥3 N•m）and SIiN group (P<0.05). Conclusions When the fractured femurs are fixed by three internal fixation devices, the stability of TiNi SMA group is weakest, SIiN group being better, and LCDCP group being best. The axial micromotion in TiNi SMA group can promote the healing of fracture.

Biomechanical study of the atlantoaxial joint after artificial atlanto-odontoid joint arthroplasty / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint (AAOJ) arthroplasty by comparing with a conventional method.</p><p><b>METHODS</b>After anterior decompression, 24 human cadaveric spinal specimens of C0-C3 were randomly divided into two groups: Group A receiving artificial AAOJ arthroplasty; Group B experiencing anterior transarticular screw (ATAS) fixation. Two groups underwent flexibility test in intact and instrumented states. Rotational angle of the C0-C3 segments was measured to study the immediate stability and function of anterior decompression with AAOJ arthroplasty compared with the intact state and ATAS fixation.</p><p><b>RESULTS</b>Compared with the intact state, anterior decompression with AAOJ arthroplasty resulted in a significant decrease in the range of motion (ROM) and neutral zone (NZ) during flexion, extension and lateral bending (P less than 0.05); however, with regard to axial rotation, there was no significant difference in ROM and NZ (P larger than 0.05). Compared with anterior decompression with ATAS fixation, anterior decompression with AAOJ arthroplasty during flexion, extension and lateral bending, significant difference was found in ROM and NZ (P larger than 0.05); however, as for axial rotation, there was a significant increase in ROM and NZ (P less than 0.05).</p><p><b>CONCLUSION</b>The self-designed AAOJ has an excellent biomechanical performance, which can restore excellent instant stability and preserve the movement of the atlantoaxial joint.</p>

The biomechanical and clinical study of the percutaneous pedicle screw fixation in the treatment of thoracolumbar fractures / 中华骨科杂志

ObjectiveTo evaluate the biomechanical stability and the clinical efficacy of the percutaneous pedicle screw fixation in the treatment of thoracolumbar fractures. Methods Twelve lumbar fracture models were made on fresh calf lumbar spine specimens to compare the stability of the 4 monoaxial screws and 4 muhiaxial screws transpedicular fixation by examining the range of motion(ROM) in flexion,extension, lateral bending, and torsion. Sixty cases of thoracolumbar fractures without neuro-deficiency were treated surgically, 11 of the minimally invasive group(monoaxial screw group) and 18 of the open surgery group(multiaxial screw group) were followed up more than 12 months. ResultsThe 4 monoaxial screws transpedicular fixation specimen exhibited a smaller ROM significantly in flexion, extension compared withthe 4 multiaxial screws transpedicular fixation specimen. The 4 monoaxial screws transpedicular fixationspecimen exhibited a significantly smaller ROM in flexion and extension than the intact specimens. TheROM in the 4 multiaxial screws transpedicular fixation specimen and the intact showed on significant differences. There were no significant differences between the two groups in the preoperative and postoperative anterior fractured vertebral height (AVH) and the Cobb's angle (CA), but there were significant differences in the AVH and the CA between preoperative and postoperative in the two groups. There were significant differences in the correction loss of the AVH between the two groups at final follow-up.ConclusionThe percutaneous pedicle screw fixation using Sextant system is a good minimally invasive surgical choice for patients with thoracolumbar fractures without neuro-deficiency, but which has a loss of the AVH and worse flexion-extension stiffness in follow-up compared with the open monoaxial screws fixation.

Biomechanical stability of unilateral pedicle screw fixation on cadaveric model simulated two-level posterior lumbar interbody fusion / 中华外科杂志

<p><b>OBJECTIVE</b>To analyze the biomechanical efficacy of unilateral pedicle screw fixation on human cadaveric lumbar spine model simulated by two-level posterior lumbar interbody fusion (PLIF).</p><p><b>METHODS</b>Six fresh-frozen adult human cadaveric lumbar spine motion segments (L(2)-S(2)) were simulated to unilateral/bilateral L(4)-S(1) PLIF constructs augmented by unilateral/bilateral pedicle screw fixation sequentially and respectively. All configurations were tested by MTS 858 in the following sequential construct order: the intact, UI (unilateral instability), UIUF1C (unilateral instability via unilateral pedicle screw fixation plus one cage), BIUF1C (bilateral instability via unilateral pedicle screw fixation plus one cage), BIBF1C (bilateral instability via bilateral pedicle screw fixation plus one cage) and BI (bilateral instability without pedicle screw and cage). Each specimen was nondestructively tested in flexion/extension, lateral bending, and axial rotation. An axial compressive load ranged from 40 N to 360 N and the maximum peak moment of 8 N·m was applied during testing. The range of motion (ROM) and neutral zone (NZ) of fusion segment were recorded by a 6-Eagle Motion Analysis F40 system, and then statistic comparison were performed between different simulated constructs with One Way of ANOVA and Post hoc LSD tests.</p><p><b>RESULTS</b>BIBF1C had the lowest ROM and NZ of L(4)-S(1) fusion segments in all loading models, which were significantly lower than those of any uninstrumented construct (the intact, UI and BI) (P < 0.05). In flexion/extension, lateral bending, and axial rotation, the ROM of UIUF1C was respectively 2.53 ± 1.12, 4.03 ± 2.19, 2.78 ± 1.00 and the NZ of UIUF1C was respectively 1.14 ± 0.70, 1.96 ± 1.13, 1.28 ± 0.71, which were significantly lower than those of the intact (P < 0.05). Compared to BIBF1C, the ROM and NZ were respectively increased 60.13% and 17.52% in flexion/extension, 315.46% and 243.86% in lateral bending, 8.17% and 6.20% in axial rotation, however, there were no significant differences between these two constructs (P > 0.05). In lateral-bending and axial rotation, the ROM and NZ of BIUF1C were significantly higher than those of BIBF1C (P < 0.05). In flexion/extension, the ROM and NZ of BIUF1C were higher than those of BIBF1C but there were no significant differences (P > 0.05). Compared to the intact, BIUF1C had lower ROM and NZ except for higher NZ in axial rotation, and there were significant differences only in flexion/extension (P < 0.05).</p><p><b>CONCLUSIONS</b>All tested two-level unilateral fixation on simulated human cadaveric model with unilateral PLIF can achieve similar initial biomechanical stability in comparison with two-level bilateral pedicle screw fixation. However in most test modes, two-level unilateral pedicle screw fixation on simulated human cadaveric model with bilateral PLIF can not achieve enough biomechanical efficacy in comparison with two-level bilateral pedicle screw fixation.</p>

Application of three-dimensional laser scanning-based maxillofacial soft tissue reconstruction in orthodontic treatment / 南方医科大学学报

<p><b>OBJECTIVE</b>To establish a convenient and rapid method for constructing a digital model of the maxillofacial soft tissue based on three-dimensional laser surface scanning to allow direct and accurate observation of the soft tissue changes in the course of orthodontic treatment.</p><p><b>METHODS</b>The point cloud data of three-dimensional laser scanning of the maxillofacial region were acquired from a healthy woman with Angle Class I occlusion, who maintained a horizontal Frankfort plane during scanning with the scanner placed at a distance of 80 cm. The scanning was repeated twice after wearing the dental cast for an Angle Class I occlusion. The three-dimensional digital model of the maxillofacial soft tissue was constructed based on the point cloud using GeoMagic10.0 software.</p><p><b>RESULTS</b>The high-resolution three-dimensional model of the maxillofacial soft tissue reconstructed allowed accurate observation of the distinct facial anatomical landmarks and represented directly the soft tissue changes in the process of orthodontic treatment by merging the models. Using the analytic tool provided by the software, this model also allowed direct quantitative measurement of the nasolabial angle and the distances from the esthetic plane to the upper lip, labral inferior, and mentolabial sulcus, which were 111.86°, -3.57 mm, -2.54 mm, and 3.95 mm before orthodontic treatment as compared to 114.31°, -2.73 mm, -1.06 mm, and 3.46 mm during treatment, and 116.53°, -0.15 mm, 0.64 mm, and 3.11 mm after the treatment, respectively.</p><p><b>CONCLUSION</b>Three-dimensional laser surface scanning enables accurate and rapid construction of the digital model of the facial soft tissues, which may provide valuable assistance in orthodontic treatment.</p>

Pullout test in expansive unilateral open-door laminoplasty of the cervical spine with OsteoMed M3 plate and screws: the screw orientation matters / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the impact of screw orientation on the pullout strength of OsteoMed M3 titanium screws in expansive unilateral open-door laminoplasty of the cervical spine.</p><p><b>METHODS</b>Six fresh human cervical spine specimens were randomly numbered and OsteoMed M3 plate and screws were used for an expansive unilateral open-door laminoplasty. The screws were inserted in the lateral mass at different extraversion angles (0°, 30° and 45°). The maximum pullout strength was tested on the ElectroForce material testing machine.</p><p><b>RESULTS</b>The maximum pullout strength was 81.60∓7.33 N, 150.05∓15.57 N, and 160.08∓17.77 N in extraversion angle 0°, 30°, and 45° groups, respectively. The maximum pullout strength was significantly less in extraversion angle 0° group than in 30° and 45° groups (P<0.05), but similar in the latter two groups.</p><p><b>CONCLUSION</b>The pullout strength of the screws inserted at an extraversion angle over 30° provides stronger fixation than an angle of 0° in the unilateral open-door laminoplasty using OsteoMed M3 titanium plate and screws.</p>

Six degree-of-freedom acquisition and analysis of jaw opening and closing with motion capture system / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore the six degrees of freedom of jaw opening and closing movement with motion capture and analysis system to establish a quantitative method for studying mandibular movement and a digital basis for virtual reality study of mandibular movement.</p><p><b>METHODS</b>In a male adult with normal dentition without temporomandibular joint disorders, 3 fluorescent markers were pasted in the upper dentition and 4 in the lower dentition. Six cameras of the motion capture system were arranged in a semi-circular fashion. The subject sat in front of the camera at an 80-cm distance with the Frankfort plane kept parallel to the horizontal plane. The degree-of-freedom (3 linear displacement and 3 angular displacement) of jaw opening and closing movement was obtained by collecting the marker motion.</p><p><b>RESULTS</b>Six degrees of freedom of jaw opening and closing were obtained using the motion capture system. The maximum linear displacements of X, Y and Z axes were 5.888 089 cm, 0.782 269 cm, and 0.138 931 cm, and the minimum linear displacements were -3.649 83 cm, -35.961 2 cm, -5.818 63 cm, respectively. The maximum angular displacements of X, Y and Z axes were 0.760 088°, 2.803 753°, and 0.786 493°, with the minimum angular displacements of -2.526 18°, -0.625 94°, and -25.429 8°, respectively. Variations of linear displacements during jaw opening and closing occurred mainly in the Y axis, and those of angular displacement occurred mainly in the Z axis.</p><p><b>CONCLUSION</b>The six degree-of-freedom of mandibular movement can be accurately obtained with the motion capture system to allow quantitative examination of the mandibular movement.</p>

2D/3D registration system based on single X ray image and CT data / 医用生物力学

Objective To build a 2D/3D registration system based on the compute unified device architecture(CUDA) frame with single X-ray image and CT data of knee joints and apply it in the research of knee motion and stability of implanted prosthesis. Method The digital radiography(DR) equipment used in the study was calibrated by the Zhang zhengyou Calibration Method, and then digitally rendered radiographs(DRR) images were generated in the CUDA frame with light tracing algorithm, and the best 2D/3D registration parameters were calculated with a similarity operator of cross correlation; finally, the results were evaluated by using the method of 3D/3D registration with data obtained from a 3D laser scanner. Results With knee specimen X-ray images and CT data, in 6 degrees of freedom, the average errors of transform were below 1 mm, and those of rotation were below 1°. Conclusions The 2D/3D registration system can meet the precision requirement of motion detection and be used to study the knee motion and prosthesis location.

Effects of spondylolysis on mechanical stability of upper lumbar vertebrae / 医用生物力学

Objective To study the stability of upper lumbar vertebra in spondylolysis by measuring the upper vertebra pressure on lumbar spondylolysis models. Method Nine fresh frozen human lumbar spinal specimens were used as experimental models. The pressure on upper vertebral discs of lumbar vertebrae was measured by the material testing machine (MTS 858 Bionix test system)with extension, flexion and axial, bilateral compression being applied on two groups of specimens: 1) intact spine; 2) lumbar spondylolysis. Results Compared with the intact specimens, the pressure of upper lumbar vertebra in spondylolysis was increased by 1.3％，1.5％，1.7％ in axial compression with 600, 800, 1 000 N (the differences were not significant (P＞0.05)), by 20.97％，24.45％，28.79％ in 15°of extension with 300, 500, 700N (the differences were significant (P < 0.01)), by 14.15％，17.86％，24.92％ in 15°of flexion with 300, 500, 700N (the differences were significant (P < 0.01)), by 3.54％，2.12％，1.14％ in 15°of bilateral compression with 300, 500, 700N (the differences were not significant (P＞0.05)). Conclusions Lumbar spondylolysis has a significant mechanical influence on lumbar spine not only at the involved level but also at the upper adjacent level, which can affect the stability of lumbar spine correspondingly.

Effect of Coflex interspinous stabilization and vertebral arch pedicle screw implantation on the stability of three-dimensional motions of the lumbar spine / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate the effect of Coflex interspinous stabilization and vertebral arch pedicle screw implant on the stability and motion of the lumbar spine.</p><p><b>METHODS</b>The range of motion (ROM) of 6 fresh adult human cadaver lumbar spine specimens (L(1) approximately S(1)) was biomechanically tested in forward flexion/extension stretch, left/right lateral bending and left/right axial rotation. The ROM and neutral zone (NZ) of the segments L(2/3), L(3/4), and L(4/5) were measured and compared in 3 conditions, namely intact condition (a), rigid fixation of the segment L(4/5) with vertebral arch pedicle screw (b), and condition b plus L(3/4) stabilization with Coflex device (c).</p><p><b>RESULTS</b>The ROM of segment L(4/5) was significantly smaller in conditions b and c than in condition a in all the directions (P<0.05). The ROM of segment L(3/4) was significantly smaller in conditions a and c than in condition b in extension stretch (P<0.01), smaller in condition a than in conditions b and c in left/right lateral bending (P<0.01), and decreased significantly in the order of a<c<b in forward flexion stretch and left/right axial rotation (P<0.05). The ROM of segment L(2/3) was significantly smaller in conditions a and b than in condition c in extension stretch (P<0.01), but showed no significant differences between the 3 conditions in the other directions (P>0.05).</p><p><b>CONCLUSIONS</b>The ROM of the segment superior to the lumbar spine with rigid fixation increases in all the directions, but can be reduced with Coflex device implanted in the superior segment, which results in only increased ROM of the segment superior to Coflex device in extension stretch.</p>

Effect of microwave plasma parameters on the surface modification of denture base resins / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore the working parameters of the microwave plasma for surface modification of denture base resins.</p><p><b>METHODS</b>Using orthogonal test method, 80 specimens of denture material were divided into 16 groups for testing. At the gas flow of 13.7 cm3/min, the specimens were tested under the working condition of different microwave powers (100, 150, 200 and 250 W), different gasses (oxygen, air, argon, oxygen and argon mixture), different gas pressure (0.4, 0.6, 0.8, and 1 kPa), and varying processing time (1, 2, 5, and 8 min). Each group of specimens was treated with the microwave plasma and the contact angles were confirmed by scanning electron microscopy.</p><p><b>RESULTS</b>The pictures of instantaneous droplet morphology were obtained from each group of samples, and the values of contact angle were measured. The contact angle was 68.86 degrees in the untreated group, and the angles of several treated groups were 48.15 degrees , 40.7 degrees and 32.76 degrees, showing a statistically significant variation of the contact angle after the treatment.</p><p><b>CONCLUSION</b>Processing time of 8 min, microwave power at 100 W, total pressure in the chamber at 0.8 kPa, and the presence of oxygen constitute the optimal condition of microwave plasma for surface modification of denture base resins. Under these conditions, the smallest contact angle of the denture base resins is 34.58 degrees, suggesting a good effect of surface modification.</p>

Construction of the digital models of masseter and temporal muscles with three-dimensional laser scanning / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore a new method for establishing digital models of the masseter and temporal muscles and superficial soft tissue using three-dimensional laser scanning technique.</p><p><b>METHODS</b>One adult male cadaveric head without malformation was dissected to expose the superficial portion of the masseter and temporalis. Multiple aspects of the sample were scanned with three-dimensional laser scanning system, and the point clouds of the masseter and temporal muscles were generated. The specimen was scanned again after the masseter and temporal muscles had been removed. The digital model of the muscles was reconstructed with the point clouds using Geomagic software, and the morphology of the muscle model was observed and measured.</p><p><b>RESULTS</b>The 3-D digital models of the masseter and temporal muscles with the anatomical characteristics were reconstructed based on the point clouds using Geomagic 8.0 software.</p><p><b>CONCLUSION</b>The digital model of the muscles can vividly demonstrate the muscle contours, which provides a basis for morphological study and biomechanical analysis of the muscles.</p>

Biomechanical evaluation of the U shape lumbar biological dynamic fixation system / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate biomechanical characteristics of a new U-shaped lumbar bioelastic internal fixation deuice (UBD).</p><p><b>METHODS</b>Six fresh calf lumbar (L2-L5) samples were divided into 4 groups, namely the normal group, traumatic instability group, instability group with rigid internal fixation and instability group with UBD fixation. The vertebral 3-dimensional range of motion (ROM) and rigidity of the 4 group were tested.</p><p><b>RESULTS</b>Elastic fixation and rigid fixation both significantly increased vertebral segment stability for flexion, extension, lateral curvature and rotations. Compared with rigid fixation, elastic fixation obviously increased the ROM by 2.22 degrees in flexion and extension, but significantly decreased the rigidity in forward bending and backward bending and compression (P<0.01).</p><p><b>CONCLUSION</b>The UBD may enhance the load sharing and decrease stress-shielding and stress concentration without sacrificing lumbar stability.</p>

Biomechanical evaluation of asymmetrical posterior internal fixation for transforaminal lumbar interbody fusion with transfacetopedicular screws / 南方医科大学学报

<p><b>OBJECTIVE</b>To assess the biomechanical stability of asymmetrical posterior internal fixation for transforaminal lumbar interbody fusion (TLIF) with transfacetopedicular screws (TFPS).</p><p><b>METHODS</b>Range of motion (ROM) testing was performed in 7 fresh-frozen human cadaveric lumbar spine motion segments in flexion/extension, lateral bending, and axial rotation using 10.0 Nm torques at the L3-4 motion segment. The sequential test configurations included intact motion segment, TLIF and ipsilateral pedicle screw (PS), TLIF and ipsilateral PS plus contralateral TFPS according to Boucher technique, and TLIF and bilateral PS. The ROM was determined to assess the construct stability.</p><p><b>RESULTS</b>In flexion/extension, lateral bending, and axial rotation, no measureable difference was found in the ROM between the standard bilateral pedicle screw and the novel asymmetric posterior internal fixation after TLIF. After TLIF, the ipsilateral PS construct provided less segment stability than the novel asymmetric construct with TFPS in flexion, left bending and left rotation. In rotation, the novel asymmetric construct allowed for significant off-axial rotation motions detrimental to the stability and fusion.</p><p><b>CONCLUSION</b>Ipsilateral PS placement plus contralateral TFPS provides stability comparable to that of TLIF with bilateral PS, and can be an alternative in minimal invasive surgery.</p>

Finite element analysis of the biomechanics of human mandible in response to impact force / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore the biomechanical mechanism of impact force-induced mandibular fractures and its finite element analysis.</p><p><b>METHODS</b>Three mandibular impact fracture models were prepared using intact human mandibular specimens and simulated maxillary models according to the Hanau principle of articulator and a MTS-858 biological material testing machine. Mandibular impact was delivered in the direction of the chin level at the mandibular postural position (MPP) on MTS. The computerized mandibular model was then established from 3-dimensional laser scanning images for finite element analysis using ANSYS7.0.</p><p><b>RESULTS</b>The 3 mandibular specimens were fractured at the chin, where the maximum force was 2151.10-/+ 125.18 N with response time of 17.3-/+2.3 ms. Impact simulation with ANSYS mimicking stress changes in the internal jaw suggested the chin as place where maximum stress occurred. According to the stress curve, the maximum stress of 3201.35 kPa occurred at the point 1.92 cm from the upper edge of the chin.</p><p><b>CONCLUSION</b>The combination of mandibular impact experiments and finite element analysis allows quantification of several parameters of the jaw and provides clues for understanding the biomechanical mechanism of mandibular impact fractures.</p>