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OBJECTIVE@#To establish the finite element model of varus-type ankle arthritis and to implement the finite element mechanical analysis of different correction models for tibial anterior surface angle (TAS) in supramalleolar osteotomy.@*METHODS@#A female patient with left varus-type ankle arthritis (Takakura stage Ⅱ, TAS 78°) was taken as the study object. Based on the CT data, the three-dimensional model of varus-type ankle arthritis (TAS 78°) and different TAS correction models [normal (TAS 89°), 5° valgus (TAS 94°), and 10° valgus (TAS 99°)] were created by software Mimics 21.0, Geomagic Wrap 2021, Solidworks 2017, and Workbench 17.0. The 290 N vertical downward force was applied to the upper surface of the tibia and 60 N vertical downward force to the upper surface of the fibula. Von Mises stress distribution and stress peak were calculated.@*RESULTS@#The finite element model of normal TAS was basically consistent with biomechanics of the foot. According to biomechanical analysis, the maximum stress of the varus model appeared in the medial tibiotalar joint surface and the medial part of the top tibiotalar joint surface. The stress distribution of talofibular joint surface and the lateral part of the top tibiotalar joint surface were uniform. In the normal model, the stress distributions of the talofibular joint surface and the tibiotalar joint surface were uniform, and no obvious stress concentration was observed. The maximum stress in the 5° valgus model appeared at the posterior part of the talofibular joint surface and the lateral part of the top tibiotalar joint surface. The stress distribution of medial tibiotalar joint surface was uniform. The maximum stress of the 10° valgus model appeared at the posterior part of the talofibular joint surface and the lateral part of the top tibiotalar joint surface. The stress on the medial tibiotalar joint surface increased.@*CONCLUSION@#With the increase of valgus, the stress of ankle joint gradually shift outwards, and the stress concentration tends to appear. There was no obvious obstruction of fibula with 10° TAS correction. However, when TAS correction exceeds 10° and continues to increase, the obstruction effect of fibula becomes increasingly significant.
Sujets)
Humains , Femelle , Tibia/chirurgie , Analyse des éléments finis , Cheville , Arthrite , Fibula/chirurgie , Articulation talocrurale/chirurgieRésumé
@#AIM:To investigate the distribution of corneal spherical aberration in age-related cataract.<p>METHODS: Retrospective study. Totally 217 cases of age related cataract(217 eyes)were collected in the Central Hospital of Kaifeng from August 2017 to August 2018. Patients were divided into 3 groups according to age: 50-60 years(63 eyes)in group Ⅰ, 61-70 years(107 eyes)in group Ⅱ, 71-80 years(47 eyes)in group Ⅲ. Pentacam anterior segment analysis was used to measure the anterior and posterior corneal K-readings. The corneal spherical aberration of anterior, posterior and total were calculated on an area of 6mm diameter by Zernike analysis and a descriptive study was used.<p>RESULTS:The Mean±SD of total corneal spherical aberration was 0.311±0.098μm for all the patients. Statically significant were found for the anterior and total corneal spherical aberration(<i>F</i>=34.434, 32.896; <i>P</i><0.05). The anterior, posterior corneal K-readings and posterior corneal spherical aberration had no correlation with age(<i>r</i>=0.040, 0.066, 0.097, <i>P</i>>0.05). The anterior and total corneal spherical aberration were positively correlated with age(<i>r</i>=0.506, 0.509, <i>P</i><0.05).<p>CONCLUSION:The total corneal spherical aberration in age-related cataract was slightly higher than that before. The anterior and total corneal spherical aberration increased with age, and then the posterior corneal spherical aberration was not.
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AIM: To analyze the effect of myopic adolescents wearing orthokeratology lens on the corneal surface curvature radius and anterior chamber depth.METHODS: Totally 120 cases of adolescent myopia were selected, among them 58 cases with 116 eyes were divided into 11-14 years old group and 62 cases with 124 eyes were 15-18 years old group according to the age.They were treated with long-term orthokeratology lens treatment, and two groups of patients were observed before wearing lens(T0), wearing for 6mo (T1), 12mo (T2) for uncorrected visual acuity, the average refractive degree improvement, the central corneal thickness, corneal curvature changes and the incidence of complications.RESULTS: The uncorrected visual acuity of the two groups at 12mo after wearing were better than that at 6mo which was better than that before wearing;the diopter had the same trend.The uncorrected visual acuity and the diopter of the 11-14 years old group at 6 and 12mo was better than those of 15-18 years old group with significant difference (P0.05).The corneal anterior surface curvature of the two groups at 12mo after wearing were more than that at 6mo which was more than that before wearing.The axial length of the 11-14 years old group was longer than that of the 15-18 years old group with significant difference (P0.05).There was no significant difference on the anterior chamber depth between the two groups at different time or between before and after wearing (P>0.05).CONCLUSION: Long-term wearing orthokeratology lenses have a significant effect for control ling juvenile myopia, and can improve the corneal anterior surface curvature, especially in the lower age group, and has no significant effect on the anterior chamber depth.
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A 28-year-old man visited the emergency department of our hospital with a chief complaint of palpitation and chest pain. The patient had undergone 4 operations at other hospitals for tetralogy of Fallot (TOF), left pulmonary atresia, an aberrant right coronary artery, and a right aortic arch. As a result of thorough investigations, we suspected that the cause of the patient's symptoms was an excess of the right ventricular pressure over the left ventricular pressure, which was caused by right ventricular compression resulted from an abnormal mass on the anterior surface of the right ventricle, and by pulmonary stenosis (PS) associated with right ventricular outflow tract stenosis (RVOTS). Excision of the mass, right ventricular outflow restoration (RVOTR), and pulmonary valve replacement (PVR) were indicated. The mass on the anterior surface of the right ventricular was found to have been caused by retention of serous fluid in the interstice formed by a folded expanded polytetrafluoroethylene (ePTFE) pericardial sheet. An ePTFE pericardial sheet, which is used to supplement the pericardium, has been reported to have advantages with respect to prevention of adhesion, denaturation of pericardial substitutes, and inflammatory thickening and adhesion of the epicardium, compared with other materials used as pericardial substitutes. However, epicardial thickening has been noted with the use of ePTFE pericardial sheets, and hence, its use is currently avoided in many cases. This case presents an extremely rare pathology in which the inflammatory reaction of the epicardium caused by an ePTFE pericardial sheet is suspected to have caused serous components to become tightly encapsulated in the interstice formed by the folded patch ; no definite cause was identified. Thus far, no other such case has been reported, and ePTFE pericardial sheets should be used with caution.
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Para convertir las mediciones obtenidas de la superficie corneal a un valor dióptrico, el keratómetro de Bausch & Lomb Optical Company utiliza la fórmula (n n)/ R y asume un índice n de 1,3375 (diferente al índice real de la córnea de 1,376). Este valor ficticio incluye una compensación para contrarrestar el pequeño pero significativo poder negativo de la superficie posterior de la córnea. Esto permite hacer la lectura directamente tanto del radio de curvatura como del poder dióptrico de la córnea.
To convert the measurements obtained from the corneal surface into dioptric value, the B&L keratometer uses the general lens formula (n-n/R) and assumes an n of 1,3375 (compared to the actual corneal refractive index of n=1,376). This is afictional value, which includes an allowance for the small, yet significant, negative power of the posterior corneal surface.