Traditional and cortical trajectory screws of static and dynamic lumbar fixation- a finite element study.

BACKGROUND: Two types of screw trajectories are commonly used in lumbar surgery. Both traditional trajectory (TT) and cortical bone trajectory (CBT) were shown to provide equivalent pull-out strengths of a screw. CBT utilizing a laterally-directed trajectory engaging only cortical bone in the pedicle is widely used in minimal invasive spine posterior fusion surgery. It has been demonstrated that CBT exerts a lower likelihood of violating the facet joint, and superior pull-out strength than the TT screws, especially in osteoporotic vertebral body. No design yet to apply this trajectory to dynamic fixation. To evaluate kinetic and kinematic behavior in both static and dynamic CBT fixation a finite element study was designed. This study aimed to simulate the biomechanics of CBT-based dynamic system for an evaluation of CBT dynamization. METHODS: A validated nonlinearly lumbosacral finite-element model was used to simulate four variations of screw fixation. Responses of both implant (screw stress) and tissues (disc motion, disc stress, and facet force) at the upper adjacent (L3-L4) and fixed (L4-L5) segments were used as the evaluation indices. Flexion, extension, bending, and rotation of both TT and CBT screws were simulated in this study for comparison. RESULTS: The results showed that the TT static was the most effective stabilizer to the L4-L5 segment, followed by CBT static, TT dynamic, and the CBT dynamic, which was the least effective. Dynamization of the TT and CBT fixators decreased stability of the fixed segment and alleviate adjacent segment stress compensation. The 3.5-mm diameter CBT screw deteriorated stress distribution and rendered it vulnerable to bone-screw loosening and fatigue cracking. CONCLUSIONS: Modeling the effects of TT and CBT fixation in a full lumbosacral model suggest that dynamic TT provide slightly superior stability compared with dynamic CBT especially in bending and rotation. In dynamic CBT design, large diameter screws might avoid issues with loosening and cracking.

Derivation and characterization of matched cell lines from primary and recurrent serous ovarian cancer.

BACKGROUND: Cell line models have proven to be effective tools to investigate a variety of ovarian cancer features. Due to the limited number of cell lines, particularly of the serous subtype, the heterogeneity of the disease, and the lack of cell lines that model disease progression, there is a need to further develop cell line resources available for research. This study describes nine cell lines derived from three ovarian cancer cases that were established at initial diagnosis and at subsequent relapse after chemotherapy. METHODS: The cell lines from three women diagnosed with high-grade serous ovarian cancer (1369, 2295 and 3133) were derived from solid tumor (TOV) and ascites (OV), at specific time points at diagnosis and relapse (R). Primary treatment was a combination of paclitaxel/carboplatin (1369, 3133), or cisplatin/topotecan (2295). Second line treatment included doxorubicin, gemcitabine and topotecan. In addition to molecular characterization (p53, HER2), the cell lines were characterized based on cell growth characteristics including spheroid growth, migration potential, and anchorage independence. The in vivo tumorigenicity potential of the cell lines was measured. Response to paclitaxel and carboplatin was assessed using a clonogenic assay. RESULTS: All cell lines had either a nonsense or missense TP53 mutations. The ability to form compact spheroids or aggregates was observed in six of nine cell lines. Limited ability for migration and anchorage independence was observed. The OV3133(R) cell line, formed tumors at subcutaneous sites in SCID mice. Based on IC50 values and dose response curves, there was clear evidence of acquired resistance to carboplatin for TOV2295(R) and OV2295(R2) cell lines. CONCLUSION: The study identified nine new high-grade serous ovarian cancer cell lines, derived before and after chemotherapy that provides a unique resource for investigating the evolution of this common histopathological subtype of ovarian cancer.

Experimental research into using bone-strengthening pill to treat ischemic necrosis of femoral head.

OBJECTIVE: To study the use of a bone-strengthening pill to treat ischemic necrosis of the femoral head. METHODS: A model of castration in rats with osteoporosis and a model of ischemic necrosis in the bilateral femoral heads of young rats were used to detect bone density, bone formation measurements, lipid deposition in the femoral head, the distribution of capillaries in the femoral head and other relevant biochemical indices. RESULTS: In model rats, bone-strengthening pills were able to increase the bone density, the unit volume of bony trabeculae, the width of bony trabeculae, and the unit volume of the bony cortex. They could also enhance the mineral apposition rate in the femoral head and the seam width of osteoid deposition. Furthermore, there was a reduction in lipid deposition in the femoral head, and enriched distribution of arteries in the femoral head. Bone-related biochemical detections showed an increase in alkaline phosphatase staining and a decrease in tartaric acidic phosphatase staining. CONCLUSION: The results show that bone-strengthening pills can obviously promote bony growth, cause an increase in bone density, restore blood circulation, inhibit the occurrence and development of bony necrosis, and accelerate the repair of necrotic bones, with no toxic side-effects.

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.

The Role of Follow-up Evaluation in the Diagnostic Algorithm of Idiopathic Interstitial Pneumonia: A Retrospective Study.

We aimed to evaluate the alteration of diagnosis of individual expert and multidisciplinary discussion (MDD) team in the longitudinal diagnostic assessment of idiopathic interstitial pneumonia (IIP). The retrospective analysis included 56 patients diagnosed as IIP by The First Affiliated Hospital of Guangzhou Medical University with follow-up visits during Jan 1st to Aug 31st 2014. Each expert was provided information in a sequential manner and was asked to assign an individual diagnosis and an MDD diagnosis after group discussion. The level of agreement among individual experts and between different visits was calculated by kappa and the agreement between individual specialist and MDD team with different consensus levels was measured by weighted-kappa coefficients. Follow-up data changed the original clinical diagnosis and MDD diagnosis in 24.1% and 10.7% of all cases, respectively, and clinician and MDD consensus level in 55.4% and 25.0%, respectively. The diagnostic performance of individual clinicians or radiologist was closer to that of the MDD compared with the pathologist, and follow-up further increased the agreement. The longitudinal evaluation of patients with IIP improved the inter-observer agreement in a multidisciplinary team. The performance of individual clinicians or radiologist was approaching the accuracy of multidisciplinary team when provided with follow-up data.

A computational mechanistic study of Pd(ii)-catalyzed γ-C(sp3)-H olefination/cyclization of amines: the roles of bicarbonate and ligand effect.

The detailed mechanism of palladium-catalyzed γ-C(sp3)-H olefination/cyclization of triflyl-protected amines was investigated by density functional theory (DFT) calculations. The olefinated intermediate was initially formed in the first catalytic cycle involving ligand exchange, bicarbonate-assisted C(sp3)-H bond cleavage, alkene insertion and 'reductive ß-hydride elimination'. The following syn-addition and reductive elimination furnish the aza-Wacker product. The first step of reductive elimination is the rate-determining step. The mechanism unveils the important roles of bicarbonate: aiding the C-H activation and abstracting the ß-proton in the second step of reductive elimination. The parallel bridging mode in the metal-olefin intermediate facilitates the syn-addition, explaining the experimentally observed stereoselectivity. The effect of the monodentate pyridine-based ligands is also discussed.