BACKGROUND:Vertebroplasty and kyphoplasty can effectively repair osteoporotic vertebral compression fractures, but postoperative change of stress in the fractured vertebrae and adjacent vertebrae can lead to new fractures. OBJECTIVE:To analyze the stress changes of the fractured and adjacent vertebrae with different bone cement injection volume by three-dimensional finite element method. METHODS:One healthy adult male volunteer was selected for lumbar spine CT scan. The acquired images were imported for three-dimensional reconstruction using Mimics. The three-dimensional model was smoothed, polished and denoised by Geomagic software, and then the solid mode was built under Workbench Ansys. The osteoporotic vertebral compression fracture model in L2-L4 segments was established after assignment. Bone cement of 1, 2, 4, 6 mL was injected into the L3 vertebrae respectively and distributed in the middle of the vertebrae as spherical shape. 500 N pre-load was applied on L2 surface with an additional moment of 50 N·m. The lower surface free degree of L4 was restrainted. The L2-L4 forward flexion, extension, right flexion and axial rotation on the right side were stimulated to compare the stress changes of fractured vertebrae and adjacent vertebrae before and after the bone cement injection with different volume. RESULTS AND CONCLUSION:The stresses of fractured and adjacent vertebrae after the bone cement injection were significantly increased; meanwhile, the stresses of fractured and adjacent vertebrae increased with the increase of bone cement injection volume, which may be one of the factors leading to the compression fractures of adjacent vertebrae.

BACKGROUND:Vertebroplasty and kyphoplasty can effectively repair osteoporotic vertebral compression fractures, but bone cement injection can cause the change of stress in the fractured vertebrae and adjacent vertebrae after surgery, leading to new fractures.
OBJECTIVE: To analyze the stress changes of the fractured vertebrae and adjacent vertebrae after vertebroplasty with different elastic modulus bone cement by a three-dimensional finite element method.
METHODS: One healthy adult male volunteer was selected for lumbar spine CT scan. The acquired images were imported for three-dimensional reconstruction using Mimics. The three-dimensional model was smoothed, polished and denoised by Geomagic software, and then the solid mode was built under Workbench Ansys. An osteoporotic vertebral compression fracture model in L2-4 segments was established after assignment. Bone cement (4 mL) with different elastic moduli (8 000, 4 000, 2 000 and 1 000 MPa) injected into the L3 segment distributed in the middle of the vertebrae as spherical shape. 500 N pre-load was applied on the L2 surface with an additional bending moment of 50 N?m. The lower surface free degree of L4 was restrained. The L2-4 forward flexion, posterior extension, right flexion and axial rotation on the right side were stimulated. The stress changes of the fractured vertebrae and the upper and lower adjacent vertebrae before and after bone cement injection with different elastic moduli were compared.
RESULTS AND CONCLUSION:The stress of the fractured vertebrae and adjacent vertebrae were significantly increased compared with that before operation. With the increase of elastic modulus, the stress of the fractured vertebrae increased, but there were no changes in the stress of adjacent vertebrae. These findings indicate that the elastic modulus of bone cement may be a method to reduce new fractures of the fractured and adjacent vertebrae after bone cement injection.

Objective:To investigate the reparative efficacy and mechanism of pressure-adjustable macroporous antibacterial hydrogel in the treatment of infected wounds.Methods:Staphylococcus aureus was used to establish wound infection models in healthy C57BL/6 mice. The models were divided into 3 groups subjected to 3 different treatments: a negative control group with no hydrogel treatment (group A), a control group treated by common medical hydrogel (group B) and an experiment group treated by pressure-adjustable macroporous antibacterial hydrogel (group C). On days 1, 3, 6, 9 and 12, the effects of 3 treatments were compared on the wound area and the number of bacterial colonies under scab, on the apoptosis of fibroblasts based on the changes of type Ⅰ procollagen, and on the inhibition of inflammation during wound repair by detecting the expression of interleukin-6 (IL-6) and tumor necrosis factor (TNF-α).Results:On days 1 and 3, there was no significant difference between the 3 groups in the wound area ( P>0.05), but on days 6, 9 and 12, there were significant differences between the 3 groups in the wound area ( P<0.05). On day 6, the wound areas in group B (1.23 cm 2 ± 0.16 cm 2) and in group C (1.14 cm 2 ± 0.12 cm 2) were significantly smaller than that in group A (1.56 cm 2 ± 0.16 cm 2) ( P<0.05), but there was no significant difference between groups B and C ( P>0.05). On days 9 and 12, the wound areas in group B (0.97 cm 2 ± 0.13 cm 2 and 0.76 cm 2 ± 0.10 cm 2) and in group C (0.66 cm 2 ± 0.06 cm 2 and 0.48 cm 2 ± 0.07 cm 2) were significantly smaller than those in group A (1.49 cm 2 ± 0.11 cm 2 and 1.39 cm 2 ± 0.13 cm 2), and those in group C were significantly smaller than those in group B (all P<0.05). On day 1, there was no significant difference between the 3 groups in the number of bacterial colonies under scab ( P>0.05). On days 3, 6, 9 and 12, the numbers of bacterial colonies under scab in groups B and C were significantly smaller than that in group A ( P<0.05), and that in group C was significantly smaller than that in group B ( P< 0.05). The nucleic acid electrophoresis showed that the grayscale bands in group C were significantly darker than those in groups A and B. The early apoptosis rate of the fibroblasts in group C[low-right positive fluorescence (LR%): 9.72%] was significantly lower than that in group A (43.99%) and that in group B (38.43%), and that in group B was significantly lower than that in group A ( P<0.05). On day 12, the ratio of the gray values of IL-6 and β-actin (0.64 ± 0.10) and the ratio of the gray values of TNF-α and β-actin (0.34 ± 0.05) in the fibroblasts in group C were significantly higher than those in group A (1.22 ± 0.21 and 0.60 ± 0.14) and in group B (0.88 ± 0.02 and 0.41 ± 0.06) ( P<0.01). Conclusion:The pressure-adjustable macroporous antibacterial hydrogel is an effective treatment of infected wounds and its mechanism may be related to the reduced apoptosis of fibroblasts.

Objective:To analyze the relationship between arch index and foot kinematic parameters and their characteristics in stress fracture of lower extremity.Methods:A case-control study was performed for 108 recruits selected from a certain army unit in 2019. Before training, the recruits′ foot print images were collected by the capacitive plantar pressure measurement system to calculate their arch indices. The kinematic characteristics of the foot were analyzed by the dynamic gait posture analysis system. Spearman rank correlation analysis between arch index and foot kinematic parameters including landing elevation angle, toe-off angle, landing speed, landing varus angle, valgus amplitude and landing valgus speed were performed. Throughout the training, orthopedic physicians followed up the recruits, among whom 10 were excluded due to other types of lower extremity injuries. The arch index and foot kinematic characteristics were analyzed and compared between the remained recruits with stress fracture of lower extremity (fracture group, n=10) and those without lower extremity injury (control group, n=79). Results:(1) For the recruits, the arch index was 0.21(0.12,0.25), with landing elevation angle for (17.31±4.02)°, toe-off angle for (63.90±5.63)°, landing speed for (176.85±24.39)°/s, landing varus angle for (13.64±4.44)°, valgus amplitude for (12.16±3.42)°, and landing valgus speed for 382.50(311.05,474.80)°/s. (2) The landing varus angle ( r=0.25, P<0.01) and valgus amplitude ( r=0.14, P<0.05) were positively related to the arch index. (3) The arch index, toe-off angle and landing valgus speed were 0.20(0.07,0.24), (61.59±5.51)° and 336.00(251.02,428.67)°/s in fracture group, significantly lower than 0.23(0.17,0.26), (64.79±4.79)° and 381.20(313.63,470.92)°/s in control group ( P<0.05 or 0.01). There were no significant differences in the landing elevation angle, landing speed, landing varus angle and valgus amplitude between the two groups (all P>0.05). Conclusions:The change of the arch index can affect the landing varus angle and valgus amplitude of the foot. Recruits who suffer from stress fracture of lower extremity have the characteristics of higher arch, lower toe-off angle and lower landing valgus speed.

Objective: To evaluate the value of cerebrospinal fluid markers expecially total-tau protein (T-tau), phosphorylated-tau protein (P-tau) in diagnosis and differentiation of sporadic Creutzfeldt-Jakob disease (sCJD). Methods: sCJD (according to 2009 Brain criteria, 2018 Neurology amended criteria), Alzheimer's disease (AD; the National Institute on Aging at National Institutes of Health and the Alzheimer's Association revised guidelines 2011 criteria) and other patients without cognitive impairment, matched for sex and age, in the Department of Neurology, Peking Union Medical College Hospital from 2018 to 2019 were enrolled. Twelve sCJD patients, 49 AD patients and 14 normal controls were enrolled. Cerebrospinal fluid (CSF) specimens were collected through gravity dropping directly, and further stored in -80 ℃ and disposed according to widely used standards. The levels of T-tau and P-tau were measured by ELISA. The data on electroencephalogram and neuroimaging findings of sCJD patients were recorded. Moreover, specimens of sCJD patients were sent to the Chinese Center for Disease Control and Prevention to test 14-3-3 protein and PRNP genotype. Results: Using Mann-Whitney U test, T-tau concentrations were found higher in patients with sCJD (1 211(448, 2 227) pg/ml) than in AD patients (549(314, 1 078) pg/ml; U=178, P=0.034 9), and both groups had higher T-tau than the control group (127(79, 192) pg/ml; U=20, 73, P<0.01). The level of P-tau was significantly increased in AD patients (72(58,109) pg/ml) compared to the control group (27(15, 42) pg/ml; U=82, P<0.01), but not in sCJD patients (32(24, 47) pg/ml). The T-tau/P-tau ratio was higher in sCJD patients (29.77(20.01, 54.53)) than in AD patients (7.45(4.79, 10.43); U=87, P<0.01). Twelve sCJD patients had cotical hyperintensity on diffusion weighted imaging and five had periodic three-phase waves on electroencephalogram. Nine sCJD patients, whose CSF samples were tested in the Chinese Center for Disease Control and Prevention, carried an M/M genotype at codon 129 and E/E at codon 219. Conclusion The CSF tau level and T-tau/P-tau ratio are significantly increased in sCJD, which may promote the diagnosis and differentiation of sCJD in routine clinical setting.