摘要:目的:研究生物降解聚DL乳酸(PDLLA)自鎖式捆綁帶固定骨折的生物力學性能。方法:80只新西蘭大白兔隨機分為兩組,建立股骨干非負重骨折動物模型,應用生物降解自鎖式捆綁帶固定骨折為實驗組,鋼絲固定骨折為對照組,分別于術后1、4、8、12周行生物力學檢查進行比較。結果:捆綁帶組在術后4、8、12周均比鋼絲組的彎曲強度高,但4周、12周時Pgt;005,無統計學差異,8周時Plt;005,提示有統計學差異。離體同種固定物不同時間段抗拉強度自身比較:鋼絲固定術后4階段抗拉強度比較Pgt;005,任何兩兩比較都沒有統計學差異,抗拉強度未隨術后時間延長發生明顯下降。捆綁帶固定術后4周與術后1周比較Pgt;005,抗拉強度無明顯降低,但術后8周和術后12周時Plt;005,抗拉強度明顯下降。結論:生物降解自鎖式捆綁帶在非負重骨折治療中可發揮良好的固定作用。生物降解自鎖式捆綁帶降解時,應力傳導促進了骨折的愈合。Abstract: Objective: To study the biomechanics function of selflocking cerclage band made of biodegradable material polyDLlactic acid (PDLLA) in the fixation of fractures. Methods: Eighty rabbits were divided into two groups. Femur fracture models were made. Fractures were fixed using biodegradable selflocking cerclage band in experimental group and metal fixation material in control group. The biomechanics was analyzed and compared after 1, 4, 8 and 12 weeks respectively． Results: The bending strength of experimental group is more ber than that of control group after 4, 8 and 12 weeks, but it was not statistically significant at 4 and 12 weeks (Pgt;005). It was statistically significant at 8 weeks (Plt;005). The tensile strength of the same cerclage instrument was compared at different stage in vitro, and the result of the control group was not statistically significant at the four stage (〖WTBX〗P〖WTBZ〗gt;005). Regarding the changes of tensile strength of the cerclage instrument at different stage, the result of the experimental group was not statistically significant after 1 and 4 weeks (Pgt;005). However, the decrease of tensile strength was statistically significant after 8 and 12 weeks (Plt;005). Conculsion: Biodegradable selflocking cerclage band could be used in thetreatment of nonweightbearing fractures. The stress force conducting promotes healing of fracture when the selflocking biodegradable cerclage band degrades.
Objective To study the cellular biocompatibility, adhesion and proliferation of endothelial outgrowth cells (EOCs) isolated and expanded from rabbit peripheral blood cultured with aligned poly-L-lactic acid (PLLA) nanofibrous scaffolds in vitro so as to provide a basis for the applications of scaffolds biomaterials in tissue repair. Methods Nanofibrous scaffolds of PLLA by electrostatic spinning were modified by hypothermal plasmas body and type Ⅰ collagen was coated onto the materials physically. In vitro, EOCs were cultured on the modified PLLA scaffold. Adhesion and proliferation were surveyed and morphological changes and biocompatibility of seeding cells on PLLA scaffold were observed by growth curves of the cells, fluorescent microscope and scanning electron microscope respectively. Results Fibers with diameters ranging from 300 nm to 400 nm were included in the nanofibrous scaffolds, whose porosities were more than 90%. Absorbance (A) of each scaffold increased gradually after EOCs grew in the absence or presence of random, aligned, or super-aligned PLLA nanofibrous scaffold. Although there was no detectable effect of the random PLLA scaffold on the growth EOCs (Pgt;0.05), both aligned and super-aligned PLLA nanofibrous scaffold had significantly enhanced their growth since the 5th day (P＜0.05). The rates of adhesion in both aligned and super-aligned PLLA nanofibrous scaffold were significantly higher than those of random PLLA scaffold after 12 h and 24 h incubation (P＜0.01). The rates of proliferation after 1 d, 3 d and 7 d incubation in aligned and super-aligned PLLA nanofibrous scaffold were significantly higher than those of random PLLA nanofibrous scaffold (P＜0.05, P＜0.01). EOCs grew well with PLLA scaffold, yet confused and disorderly in random nanofibers. EOCs could attach, extend and proliferate following fibrous orientation in aligned and super-aligned PLLA nanofibrous scaffold, in majority of the fibers were oriented along the longitudinal axis so that a unique aligned topography was formed. Especially super-aligned PLLA nanofibrous had advantageous to keep well on cell morphology. Conclusion EOCs are ideal seeding cells for tissue engineering. EOCs can be adhered well to aligned and super-aligned PLLA nanofibrous scaffold and proliferate, keep well on cell morphology. So this type of PLLA nanofibrous scallfold is proposed to be an optimal candidate material for EOCs transplantation in tissue repair.
ObjectiveTo investigate the effect of electrospun chitosan/polylactic acid (ch/PLA) nerve conduit for repairing peripheral nerve defect in rats.
MethodsNerve conducts loaded with ch/PLA was made by the way of electrospun. The mechanical property, hydrophility, biocompatibility were tested, and the scanning electron microscope was used to observe the ultrastructure. The same experiments were also performed on pure PLA nerve conducts as a comparison. Then, 54 Sprague Dawley rats were divided into 3 groups randomly, 18 rats in each group. Firstly, the 10 mm defects in the right sciatic nerves were made in the rats and were respectively repaired with ch/PLA (group A), autografts (group B), and no implant (group C). At 4, 8, and 12 weeks after operation, general observations, sciatic functional index (SFI), electrophysiological evaluation, wet weight of gastrocnemius and soleus muscles, histological examination, immunohistological analysis, and transmission electron microscopy were performed to evaluate the effects.
ResultsCompared with pure PLA nerve conducts, the addition of chitosan could improve the mechanical property, hydrophility, biocompatibility, and ultrastructure of the nerve conducts. At 4 weeks postoperatively, the regenerated nerve bridged the nerve defect in group A. The SFI improved gradually in both group A and group B, showing no significant difference (P>0.05). Compound muscle action potentials and nerve conduction velocity could be detected in both group A and group B at 8 and 12 weeks after operation, and significant improvements were shown in both groups (P<0.05). The wet weight and myocyte cross section of gastrocnemius and soleus muscles showed no significant difference between group A and group B (P>0.05), but there was significant difference when compared with group C (P<0.05) at 12 weeks postoperatively. Immunohistological analysis revealed that S-100 positive Schwann cells migrated in both group A and group B, and axon also regenerated by immunohistological staining for growth associated protein 43 and neurofilaments 160. Transmission electron microscopy showed no significant difference in the diameter of nerve fiber between group A and group B (P>0.05), but the thickness of myelin sheath in group A was significantly larger than that in group B (P<0.05).
ConclusionThe electrospun ch/PLA nerve conduits can effectively promote the peripheral nerve regeneration, and may promise an alternative to nerve autograft for repairing peripheral nerve defect.
Objective To study the mechanism of ectopic osteogenesis of nacre/Polylactic acid (N/P) artificial bone combined with allogenic osteoblasts, and to explore the possibility as a scaffold material of bone tissue engineering. Methods The allogenic- osteoblasts seeded onto N/P artificial bone were co-cultured in vivo 1 week.The N/P artificial bone with allogenic osteoblasts were implanted subcutaneously into the left back sites of the New Zealand white rabbits in the experimental group and the simple N/P artificial bone into the right ones in the control group. The complexes were harvested and examined by gross observation, histologic analysis and immunohistochemical investigation 2, 4 and 8 weeks after implantation respectively.Results In experimental group, the osteoid formed after 4 weeks, and the mature bone tissue withbone medullary cavities formed after 8 weeks; but in control group there was nonew bone formation instead of abundant fibrous tissue after 4 weeks, and more fibrous tissue after 8 weeks.Conclusion N/P artificial bone can be used as an optical scaffold material of bone tissue engineering.
Objective To explore the prognostic value of early lactate clearance rate in patients with respiratory failure.Methods 117 patients with respiratory failure and elevated blood lactate, admitted into respiratory intensive care unit( RICU) between January 2010 and December 2011, were retrospectively analyzed. Arterial lactate and arterial blood gas were measured before and 12h, 24h, 48h, and 72h after treatment. Then12h lactate clearance rate was calculated. The acute physiology and chronic health evaluation Ⅱ( APACHEⅡ) score was evaluated before and after 12h treatment. The mortality were compared between subgroups with different lactate normalization time( lt;24 h, 24 ～48 h, 48 ～72 h, and gt;72h, respectively) . The clinical data was compared between subgroups with different prognosis ( survival or non-survival ) and between subgroups with different lactate clearance rate( ≥10% as high lactate clearance rate, lt;10% as low lactate clearance rate) . Results The mortality of the patients with lactate normalization time in less 24 hours was significantly lower than that of the patients with lactate normalization time more than 72 hours ( 5. 3% vs. 89. 2% , P lt; 0. 001) . The 12 hour lactate clearance rate of the survival group was significantly higher than that of the non-survival group [ ( 43. 6 ±26. 8) % vs. ( 12. 3 ±39. 1) % , P lt;0. 01] . The mortality of the patients with high lactate clearance rate was significantly lower than that of the patients with lowlactate clearance rate( 25. 8% vs. 71. 4% , P lt;0. 01) . Conclusion Early lactate clearance rate can be used as a marker for prognosis of patients with respiratory failure.
Objective To evaluate the significance of lactate dehydrogenase (LDH) as a predictor of in-hospital mortality in patients with acute aortic dissection(AAD). Methods We conducted a retrospective analysis of the clinical data of 445 AAD patients who were admitted to the Second Xiangya Hospital of Central South University and the Changsha Central Hospital from January 2014 to December 2017 within a time interval of ≤14 days from the onset of symptoms to hospital admission, including 353 males and 92 females with the age of 45-61 years. LDH levels were measured on admission and the endpoint was the all-cause mortality during hospitalization. Results During hospitalization, 86 patients died and 359 patients survived. Increased level of LDH was found in non-survivors compared with that in the survived [269.50 (220.57, 362.58) U/L vs. 238.00 (191.25, 289.15) U/L, P<0.001]. A nonlinear relationship between LDH levels and in-hospital mortality was observed. Using multivariable logistic analysis, we found that LDH was an independent predictor of in-hospital mortality in the patients with AAD [OR=1.002, 95% CI (1.001 to 1.014), P=0.006]. Furthermore, using receiver operating characteristic (ROC) analysis, we observed that the best threshold of LDH level was 280.70 U/L, and the area under the curve was 0.624 (95% CI 0.556 to 0.689). Conclusion LDH level on admission is an independent predictor of in-hospital mortality in patients with AAD.
Objective Choose polylactide-co-glycolide/hydroxyapatite (PLGA/HA) and porous phosphate calcium (PPC) as the object that we will study, compare their degradabality and choose one as a suitable scaffold for rib reconstruction. Methods All the experiments were divided into PLGA/HA group and CPC group. Degradabality experiment in exvivo: put the two scaffold which have the same size into 0.9% NaCl, keep sterile, then put the container into warm cage，get out and weigh them in 2, 4, 8, 12 and 24 weeks, compare the different speed of the two scaffold. Degradability experiment in vivo: put the two scaffold which have the same size under the skin of the rabbit, and weigh them in 2, 4, 8, 12 and 24 weeks, the tissue around the scaffold was examinzed by HE and the scaffold was examined by electron scanning microscope. Results Micro-CT and Scanning electron microscopy shows that CPC group had better structure （1101.2228±0.6184 mg/ccm vs. 1072.5523±0.7442 mg/ccm）and porosity（70.26％±0.45％ vs.72.82％±0.51％）than PLGA/HA group; The result of degradabality experiment in vitro shows that the speed of the two scaffolds was slow. It is at 24 weeks that the degradability is obvious,and the PLGA/HA group degraded a lot which was 60%. The result of degradabality experiment in vivo shows that the speed of degradabality of PLGA/HA group was faster than that is in the 0.9% Nacl, also was faster than that of CPC group which was 96%.The reponse of tissue around the PLGA/HA was more sever than that of CPC group which is in favour of the growth of cells. Conclusion As for the reconstruction of large defect of rib, CPC is more suitable than PLGA/HA.
Objective
To investigate the effect of a porous calcium phosphate/bone matrix gelatin (BMG) composite cement (hereinafter referred to as the " porous composite cement”) for repairing lumbar vertebral bone defect in a rabbit model.
Methods
BMG was extracted from adult New Zealand rabbits according to the Urist’s method. Poly (lactic-co-glycolic) acid (PLGA) microsphere was prepared by W/O/W double emulsion method. The porous composite cement was developed by using calcium phosphate cement (CPC) composited with BMG and PLGA microsphere. The physicochemical characterizations of the porous composite cement were assessed by anti-washout property, porosity, and biomechanical experiment, also compared with the CPC. Thirty 2-month-old New Zealand rabbits were used to construct vertebral bone defect at L3 in size of 4 mm×3 mm×3 mm. Then, the bone defect was repaired with porous composite cement (experimental group, n=15) or CPC (control group, n=15). At 4, 8, and 12 weeks after implantation, each bone specimen was assessed by X-ray films for bone fusion, micro-CT for bone mineral density (BMD), bone volume fraction (BVF), trabecular thickness (Tb. Th.), trabecular number (Tb.N.), and trabecular spacing (Tb. Sp.), and histological section with toluidine blue staining for new-born bone formation.
Results
The study demonstrated well anti-washout property in 2 groups. The porous composite cement has 55.06%±1.18% of porosity and (51.63±6.73) MPa of compressive strength. The CPC has 49.38%±1.75% of porosity and (63.34±3.27) MPa of compressive strength. There were significant differences in porosity and compressive strength between different cements (t=4.254, P=0.006; t=2.476, P=0.034). X-ray films revealed that the zone between the cement and host bone gradually blurred with the time extending. At 12 weeks after implantation, the zone was disappeared in the experimental group, but clear in the control group. There were significant differences in BMD, BVF, Tb. Th., Tb. N., and Tb. Sp. between 2 groups at each time point (P<0.05). Histological observation revealed that there was new-born bone in the cement with the time extending in 2 groups. Among them, bony connection was observed between the new-born bone and the host in the experimental group, which was prior to the control group.
Conclusion
The porous composite cement has dual bioactivity of osteoinductivity and osteoconductivity, which are effective to promote bone defect healing and reconstruction.
OBJECTIVE To confirm membrane-guided tissue regeneration in the healing course of segmental bone defects and study the mechanism. METHODS Segmental, 1 cm osteoperiosteal defects were produced in both radii of 12 rabbits. One side was covered with hydroxyapatite/polylactic acid(HA/PLA) membrane encapsulated as a tube. The contralateral side served as an untreated control. Healing courses were detected by radiographic and histologic examinations. RESULTS All control sides showed nonunion, whereas there were consistent healing pattern in test sides. CONCLUSION Membrane technique can promote bone regeneration.
