Background contextThere is little understanding of cervical plate misalignment as a risk factor for plate failure at the plate-screw-bone interface.PurposeTo assess the torsional strength and mode of failure of cervical plates misaligned relative to the midsagittal vertical axis.Study designPlastic and foam model spine segments were tested using static compression and torsion to assess effects of misaligned and various lengths anterior cervical plate (ACPs).MethodsDifferent length ACPs and cancellous fixed angle screws underwent axial torsional testing on a servo-hydraulic test frame at a rate of 0.5°/s. A construct consisted of one ACP, four screws, one ultrahigh–molecular weight polyethylene inferior block, and one polyurethane foam superior block. Group 1 had ACPs aligned in the midsagittal vertical axis, group 2 plates were positioned 20° offset from the midline, and group 3 had the ACP shifted 5 mm away and 20° offset from midline. Torques versus angle data were recorded. The failure criterion was the first sign of pullout determined visually and graphically.ResultsGroup 1 had a more direct screw pullout during failure. For the misaligned plates, failure was a combination of the screws elongating the holes and shear forces acting between the plate and block. The misaligned plates needed more torque to failure. The failure torque was 50% reduced for the longer versus the shorter plates in the neutral position. Graphically shown initial screw slippage inside the block preceded visual identification of slippage in some cases.ConclusionsWe observed different failure mechanisms for neutral versus misaligned plates. Clinically, misalignment may have the benefit of needing more torque to fail. Misalignment was a risk factor for failure of the screw-bone interface, especially in longer plate constructs. These comparisons of angulations may be a solid platform for expansion toward a more applicable in vivo model. 相似文献
The literature regarding the management of spontaneous rupture of the Achilles tendon is controversial and confusing. The relative infrequency of the condition in any one center prohibits the completion of well-designed clinical studies. Many of the disputes could be addressed and innovations tested if an appropriate animal model were available. We present a method for evaluating Achilles tendon function from measurements of the prints, preserved in bromphenol-blue-impregnated photocopying paper, of the hindfeet of walking rats. The stimulus for this study was derived from de Medinaceli's method for assessing the functional condition of rat sciatic nerves (de Medinaceli L, Freed WJ, Wyatt RJ: An index of the functional condition of rat sciatic nerve based on measurements made from walking tracks. Exp Neurol 77:634–643, 1982). Four variables were measured from these walking tracks, and comparsions between the damaged (experimental) and intact (normal) side were converted to proportional deficits. The relative contribution of each parameter to the overall deficit was determined by multiple linear regression analysis, and the variables were weighted accordingly to obtain an “Achilles Functional Index” (AFI). A sham operation produced no functional deficit, whereas animals subjected to a 0.5-cm midsubstance Achilles tendon defect demonstrated a markedly impaired AFI. Animals with repaired transected Achilles tendons also demonstrated a significant, but less severly impaired AFI. The functional deficit in this repair group returned to control values by postoperative day 15, whereas animals with a defect remained impaired at day 15. Furthermore, an excellent correlation was found between the functional recovery and biomechanical properties (ultimate failure load) of the healing tendon (r = 0.94; p < 0.001). In summary, this method provides a relatively inexpensive, sensitive, and reproducible means of assessing the functional performance of the Achilles tendon after injury in the rat. 相似文献
Binding of mammalian spermatozoa to the zona pellucida and the induction of
the acrosome reaction are prerequisites for successful oocyte
fertilization. It has been postulated that xenobiotics that are released in
the environment as well as exposure to pharmaceutical medications may be
associated with reproductive problems in men and wildlife. Examining
physiological and non-physiological effects of particular compounds on
sperm functions requires high quality in-vitro test systems. We established
a reliable combined in-vitro test system with bovine gametes and evaluated
if aliquots of pooled post-thaw spermatozoa are suitable for examining
essential sperm functions. Using cryopreserved semen, the PSA-FITC/Hoechst
33258 staining procedure was applicable to evaluate the acrosomal status
and cell viability. In the bovine hemizona assay, hemizona indices revealed
no differences between cryopreserved and fresh semen. Treatment of
post-thaw bovine spermatozoa with progesterone (1 microM or bovine
follicular fluid (20%) induced the acrosome reaction from 12% (untreated
spermatozoa) to 25% (P < 0.001) and to 22% [corrected] (P < 0.01),
respectively. Incubation of both compounds (1 microM progesterone and 20%
follicular fluid) raised the percentage of acrosome-reacted spermatozoa to
30% (P < 0001). Our results demonstrate that cryopreserved semen can be
integrated into an in-vitro screening model for reproductive toxicology
testing. Pooled, cryopreserved bovine spermatozoa will thus permit
reproducible experiments for clinical and basic science purposes and may
also be applicable for the human system.
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Background. The clinical results of implantable cardioverter-defibrillator (ICD) implantation in the elderly have received limited documentation. As the longevity of the U.S. population has increased, so has the need for ICD implantation in the elderly. We evaluated the efficacy and outcome of ICD implantation in elderly patients (>70 years) compared with younger patients.
Methods. The case records of all consecutive patients who underwent ICD implantation at our institution between 1986 and 1994 were reviewed. Of a total of 238 patients, 78 patients were 70 years of age or older and 160 patients were younger than 70 years of age.
Results. The mean age of the younger group was 58 years and that of the elderly group was 74 years. There were no statistical differences in the presence of coronary artery disease, left ventricular systolic function, the inducibility of arrhythmias, or the history of sudden cardiac death. The hospital morbidity rate was similar in both groups (6.9% in the younger group and 7.7% in the elderly group; p = not significant). The operative mortality rate was 1.9% for the younger group and 1.3% for the elderly group (p = not significant). At a mean follow-up of 33 ± 26 months, Kaplan-Meier survival curves demonstrated similar survival rates, with 93%, 82%, and 65% of the patients alive at 1, 3, and 6 years, respectively.
Conclusions. Implantable cardioverter-defibrillator implantation was equally effective in the treatment of patients older than 70 years as in younger patients. No differences in theoretic survival or morbidity were observed. 相似文献
Background: This article describes an action research project aimed at examining the accessibility of a child and adolescent mental health service to its ethnic minority populations. Method: A Child and Adolescent Mental Health Service was involved in a process of inquiry, deciding first to compare rate of referral and treatment outcomes for the four largest ethnic groups amongst the client population. Following discussion of findings throughout the service, groups of Bangladeshi service users and professionals were interviewed about low rates of referral amongst this community. Results: By highlighting the different referral rates and profiles of different ethnic groups, the study elicited an increasingly shared commitment across the service to addressing issues of accessibility to ethnic minority communities. Conclusions: The study is presented as one possible model of response to the challenge to all public services made by Macpherson (1999), to examine the 'appropriateness' of the service offered to different ethnic populations. 相似文献
Foodborne parasitic diseases are an important cause of illness and economic loss world‐wide. The public health burden imposed by parasitic diseases such as toxoplasmosis, trichinellosis, cysticercosis and trematodosis are substantial even in developed countries. The rising concern generally over food safety is causing a reappraisal of the significance of foodborne parasites and the strategies to control them. It is clear that public trust in food production systems will depend on the development of more effective safeguards, which in turn will require much greater understanding of the nature and epidemiology of these zoonoses. The complexities of these parasite's life histories, and the close association of infection risk with entrenched cultural and agricultural practices make solutions difficult. The application of the Hazard Analysis Critical Control Point (HACCP) approach will require more information on parasite epidemiology, particularly factors which regulate survival and transmission. Control strategies must address the complete sequence of events encompassed by the food production chain. This will also require more effective detection technologies. More concerted efforts to educate consumers, industry, government, and public health workers of the hazards of foodborne parasites is also needed. Coupled with this is the demand for implementation of international guidelines and codes established by WHO and FAO for the production of food, especially fish and fish products. This review will present our current understanding of the biology and epidemiology of the major foodborne parasite zoonoses, and recommendations for research and control. 相似文献