[Early clinical efficacy analysis of personalized three-dimensional printing talus prosthesis in the treatment of collapse talus necrosis]

Object To examine the preliminary clinical efficacy of custom-made three-dimensional(3D) printed talus prosthesis in the treatment of collapse talus necrosis. Methods: The clinical data of 8 patients who received 3D printed custom-made talus prostheses replacement for severe collapsed necrosis of the talus at the Orthopaedic Sports Medical Center, the First Affiliated Hospital to Army Medical University were analyzed retrospectively.All patients were male,with an average age of 38.0 years (range:22 to 65 years).There were 5 cases of left talus collapse and 3 cases of right talus collapse,with the course of disease of 29.7 weeks (range:6 to 96 weeks).The CT data of contralateral healthy talus were used for mirror image design references for the prosthesis,and the electron-beam 3D printing technology was used to prepare the prosthesis.Titanium alloy (Ti6Al4V) was taken as the material for the preparation of the talus body prosthesis,and Co-Cr-Mo material was used as the material for the preparation of the tibialis talus lateral joint surface prosthesis,and the subtalar joint surface of the prosthesis was made from a microporous casting technique.The prosthesis was analyzed preoperatively by digital three-dimensional finite element analysis and solid comparison techniques to measure anatomic match of the prosthesis.A longitudinal incision on medial ankle was made.The necrotic talus was completely removed and the prosthesis was then implanted.The patient was reexamined in the outpatient department 3, 6, and 12 months after surgery.Primary outcome measures were the American Orthopaedic Foot and Ankle Society(AOFAS) ankle-hind foot score,visual analogue scale(VAS) and ankle range of motion.Changes in imaging data and plantar pressure were also assessed.Repeated measures analysis of variance and paired-t test were used to compare the data. Results: The talus prosthesis measure preoperatively was completely consistent with that contralateral healthy talus and there was no operation-related complication. All the wounds healed primarily. The patients were followed up effectively for 23.17 months (range:12 to 48 months).The preoperative dorsiflexion of patients was (7.6±5.7)°,it increased to(14.2±6.6)° at 12 month after surgery (t=-2.67,P=0.03).The plantar flexion increased from (22.0±9.9)°preoperatively to (29.2±8.7)° at 12 month after surgery (t=-8.95,P<0.01).Preoperative AOFAS ankle-hind foot score was 26.3±6.6,and it increased to 70.1±2.2,76.0±3.4 and 79.3±4.2 at 3 month,6 month and 12 month after surgery(F=56.81,P<0.01);Pre-operative VAS was[M(Q_R)]3.0(0.8),and it increased to 2.5(1.0),1.5(1.0),1.0(1.0)at 3 month,6 month and 12 month after surgery(F=20.00,P<0.01).At the last follow-up,imaging reexamination showed that the prosthesis of all patients were in stable position with no sign of subsidence.No secondary ankle fusion or revision was required.The talus height increased from (27.6±6.0)mm preoperatively to (34.6±3.5)mm (t=-2.94,P<0.01).The plantar pressure showed that the maximum pressure on the healthy ankle was(629.9±26.1)N,and that on the affected side was(521.4±14.4)N.The pressure on the healthy ankle was(350.6±29.6)N,and that on the necrotic side was (212.3±9.7)N.The load on the contralateral forefoot was(38.1±2.8)% and that on the necrotic side was(11.5±2.0)%.The load on the contralateral hindfoot was (24.6±2.5)% and that on the necrotic side was (21.1±1.8)%. Conclusions: The custom-made 3D printed talus prosthesis could restore the talus anatomy,recover the ankle joint function,relieve the pain of patients and improve the life quality of patients.The effect on plantar pressure is mainly achieved by adjusting the center of gravity of plantar pressure backwards and the increase of weight bearing of the healthy foot.

Augmented finite-element method for arbitrary cracking and crack interaction in solids under thermo-mechanical loadings

In this paper, a thermal-mechanical augmented finite-element method (TM-AFEM) has been proposed, implemented and validated for steady-state and transient, coupled thermal-mechanical analyses of complex materials with explicit consideration of arbitrary evolving cracks. The method permits the derivation of explicit, fully condensed thermal-mechanical equilibrium equations which are of mathematical exactness in the piece-wise linear sense. The method has been implemented with a 4-node quadrilateral two-dimensional (2D) element and a 4-node tetrahedron three-dimensional (3D) element. It has been demonstrated, through several numerical examples that the new TM-AFEM can provide significantly improved numerical accuracy and efficiency when dealing with crack propagation problems in 2D and 3D solids under coupled thermal-mechanical loading conditions. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

No association of C-1019G promoter polymorphism of 5-HT1A receptor gene with migraine

It is well known that migraine has a strong genetic component, although the type and number of genes involved remains unclear. There is evidence to suggest that serotonin-related genes may be involved in the pathogenesis of migraine. To investigate whether the 5-HT1A receptor gene contributes to the risk of migraine we performed an association study of C-1019G promoter polymorphism of the gene in 102 migraineurs and 93 controls. Subjects were of Han Chinese origin. No significant differences in allele (P=0.82) or genotype frequencies (P=0.71) were seen in migraineurs compared with the controls. When migraine with aura, without aura, with family history, without family history were analyzed separately, the frequencies did not vary significantly. Our results suggest that C-1019G in 5-HT1A is not a major genetic risk factor for migraine.

Re-evaluating the toughness of human cortical bone

Data for fracture in human humeral cortical bone are re-analyzed to assess the validity for this material of linear-elastic fracture mechanics (LEFM), which is the standard method of analyzing toughness and one basis for analyzing clinical data relating to bone quality. A nonlinear fracture model, which is based on representing the damage zone in the bone by a cohesive model, is calibrated against a number of sets of test data for normal (not diseased or aged) human cortical bone taken from cadavers. The data consist of load vs. load-point displacement measurements from standard compact-tension fracture tests. Conventional LEFM is unable to account for the shape of the load-displacement curves, but the nonlinear model overcomes this deficiency. Calibration of the nonlinear model against one data curve leads to predictions of the peak load and the displacement to peak load for two other data curves that are, for this limited test set, more accurate than those made using LEFM. Furthermore, prior observations of damage mechanisms in bone are incompatible with the modeling assumption of LEFM that all nonlinearity is confined to a zone much smaller than the specimen and the crack length. The predictions of the cohesive model and the prior observations concur that the length of the nonlinear zone in human cortical bone varies in the range 3-10 mm, which is comparable to or larger than naturally-occurring bones and the specimens used to test them. We infer that LEFM is not an accurate model for cortical bone. The fracture toughness of bone deduced via LEFM from test data will not generally be a material constant, but will take different values for different crack lengths and test configurations. The accuracy of using LEFM or single-parameter fracture toughness for analyzing the significance of data from clinical studies is called into question. The nonlinear cohesive zone model is proposed to be a more accurate model of bone and the traction-displacement or cohesive law is hypothesized to be a material property. The cohesive law contains a more complete representation of the mechanics of material failure than the single-parameter fracture toughness and may therefore provide a superior measure of bone quality, e.g., for assessing the efficacy of therapy for osteoporosis.

Fracture length scales in human cortical bone: The necessity of nonlinear fracture models

Recently published data for fracture in human humeral cortical bone are analyzed using cohesive-zone models to deal with the nonlinear processes of material failure. Such models represent the nonlinear deformation processes involved in fracture by cohesive tractions exerted by the failing material along a fracture process zone, rather than attributing all damage to a process occurring at a single point, as in conventional linear-elastic fracture mechanics (LEFM). The relationship between the tractions and the net displacement discontinuity across the process zone is hypothesized to be a material property for bone. To test this hypothesis, the cohesive law was evaluated by analyzing published load vs. load-point displacement data from one laboratory; the calibrated law was then used to predict similar data taken for a different source of bone using a different specimen geometry in a different laboratory. Further model calculations are presented to illustrate more general characteristics of the nonlinear fracture of bone and to demonstrate in particular that LEFM is not internally consistent for all cases of interest. For example, the fracture toughness of bone deduced via LEFM from test data is not necessarily a material constant, but will take different values for different crack lengths and test configurations. LEFM is valid when the crack is much longer than a certain length scale, representative of the length of the process zone in the cohesive model, which for human cortical bone ranges from 3 to 10mm. Since naturally occurring bones and the specimens used to test them are not much larger than this dimension for most relevant orientations, it is apparent that only nonlinear fracture models can give an internally consistent account of their fracture. The cohesive law is thus a more complete representation of the mechanics of material failure than the single-parameter fracture toughness and may therefore provide a superior measure of bone quality. The analysis of fracture data also requires proper representation of the approximately orthotropic elasticity of the bone specimen; if the specimen is incorrectly assumed to be isotropic, the initial measured compliance cannot be reproduced to within a factor of four and the fracture toughness deduced from the measured work of fracture will be overestimated by approximately 30%.

[Kindling model of SD rats induced by injection of PTX intraperitoneally]

OBJECTIVE

To observe the kindling model of Sprague-Dawley (SD) rats induced by injection of different doses of picrotoxin (PTX) intraperitoneally, and to evaluate the effect of the drug on the model.

METHODS

SD rats were devided randomly into four groups: control group, epilepsy Group I (PTX, 1.5 mg.kg-1.d-1), epilepsy Group II (PTX, 2 mg.kg-1.d-1) and the phenobarbital group. The kindling model of rats was induced by daily injection of PTX intraperitoneally. The seizures in the rats were observed, and the results of electroencephalography (EEG) were recorded.

RESULTS

On the 20th day after injection of PTX, 71% SD rats were kindled in epilepsy Group I; 4 rats were dead, 2 rats were at stage IV of convulsions, and 2 rats were at stage V of convulsions in epilepsy Group II; 17% rats were kindled in the phenobarbital group. The EEG demonstrated spike discharges in the kindled rats.

CONCLUSIONS

In this models, the better dose of PTX is 1.5 mg.kg-1.d-1, and phenobarbital sodium can protect SD rats injected PTX intraperitoneally from seizure.

[Study on p53 gene expression following transient ischemia in the gerbil]

OBJECTIVE

To study the expression of p53 gene after transient ischemia in the gerbil.

METHODS

Northern blot was used to detect the expression of the p53 mRNA in the forebrain during different periods after post-ischemic reperfusion in the gerbil.

RESULTS

The expression of p53 mRNA increased in the forebrain during the 6th hour to the 3rd day of reperfusion following 6 min of ischemia (P < 0.05).

CONCLUSION

The high level expression of p53 might induce neuronal apoptosis after ischemia.

[Heat shock protein 70 expression following transient ischemia in the gerbil]

OBJECTIVE

To study the expression of heat shock protein 70(HSP70) following transient ischemia in the gerbil.

METHODS

Immunohistochemistry(IHC) was used to determine the expression of the HSP70 protein in the forebrain during different periods after post-ischemic reperfusion in the gerbil, and the neuronal damage was examined with microscope.

RESULTS

The HSP70 protein was only expressed at the 1st day of reperfusion(P < 0.01); and most of the neurons showed damage on the 7th day of reperfusion; heat-preconditioning could increase the expression of HSP70 protein(P < 0.01) and decrease the neuronal damage(P < 0.001) after 6 min of ischemia.

CONCLUSION

Heat-preconditioning could protect neural cells from damage by increasing the expression of the HSP70 protein.

[Relationship between insulin resistance and clustering of risk factors of cerebrovascular disease]

OBJECTIVE

To study the relationship between insulin resistance and clustering of risk factors of cerebrovascular disease.

METHODS

The serum concentrations of fasting glucose, insulin, lipids, the activities of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1(PAI-1), and the level of blood pressure were measured in 159 patients with stroke and 40 healthy control subjects.

RESULTS

All subjects were divided into 4 groups in the light of number of risk factors of cerebrovascular disease. As the number of risk factors increased, the insulin sensitivity index (ISI) in four groups gradually decreased. The ISI in the patients with cerebrovascular disease was negatively associated with increased levels of SBP, DBP, TG, APOB, and PAI-1 activity (P < 0.01) and positively with decreased level of HDL (P < 0.01).

CONCLUSION

Insulin resistance is associated with clustering of risk factors of cerebrovascular disease, the more resistant, the more clustered.

[The model and results of intervention trial of stroke risk factors in Changsha]

To develop an effective method for minimizing the incidence and mortality of cerebrovascular disease, we studied the sample population of intervention community (8,052 subjects) and control community (8,065 subjects) in Changsha. 2,631 subjects in the intervention community and 2,733 subjects in the control community with age more than 35 years were enrolled for a cohort study from January 1, 1986 to December 31, 1990. The annual incidence of stroke was 315/10(5) in the control community and 220/10(5) in the intervention community. The annual incidence of stroke was significantly lower in the intervention community than in the control community (P < 0.01). The incidence of stroke in 1990 dropped by 66.4% compared to that in 1986 in the intervention community. But, in the control community it dropped by 9.7%. The change of the mortality and incidence of stroke in the two communities was similar.

Retinal changes in a mutant form of goldfish with megalophthalmia

The retinal changes of a mutant strain of goldfish with megalophthalmia were studied by histology, electron microscopy and biochemistry. Changes in the morphology of the pigment epithelium, decrease in number of photoreceptors, thinning out of retinal layers and the existence of spaces in the retina were all features as the eyes grew in size. Invasion of macrophages was also evident in the retina. A decrease in leucine uptake per milligram of retina was also detected as the eye grew beyond 0.8 millilitre in volume. These changes, although related to volume changes (i.e., growth) of the eyes, were found to have little relationship with increase of intraocular pressure as intraocular pressures in the growing eyes of the mutant strain did not change much. Goldfish from a control strain with similar eye volumes and sizes (ages) were used for comparison and similar changes as in the mutant were not apparent.

Bilateral retinal responses after traumatic injury of one eye in mice. A histopathologic and immunohistochemical study

Iron wires (0.3 mm in diameter and 1.2 mm in length) were lodged in the left eyes of albino mice. 4 weeks after the experiment, the left and right eyes were sectioned and observed by light microscopy for any histopathology. Immunohistochemical techniques were also employed to identify macrophages and T cells. In the first case, both left (wire-lodged) and right eyes of experimental animals demonstrated pathological changes. The left eyes showed degeneration of photoreceptors and infiltration of lymphocytes at the vicinity of the pigment epithelium. The right eyes also showed degeneration of the pigment epithelium with infiltration of macrophages and lymphocytes around these areas. Immunohistochemistry revealed the presence of macrophages (44%), helper/inducer T cells (37%) and cytotoxic/suppressor T cells (19%) in the pigment epithelia and retinae of both eyes. Our results indicate that, following traumatic injury of one eye, not only the lesioned eye undergoes degeneration, but the other nonlesioned eye is affected as well, and immunologic cells are involved.

Risk factors for stroke in rural areas of the People's Republic of China: results of a case-control study

A case-control study on stroke was carried out in 1985 in conjunction with a prevalence survey on neurologic disorders in 22 rural communities of the People's Republic of China. 585 cases of stroke, detected from the survey, together with an equal number of matched controls were investigated. The statistically significant factors associated with stroke in this study were: hypertension (history, findings at examination); high salt intake; family member(s) with cerebrovascular disease and/or hypertension; heart disease (history, abnormal findings at examination); history of transient ischemic attacks, and arteriosclerotic funduscopic findings. These factors were analyzed separately for hemorrhagic and ischemic strokes.