Geometric and Mechanical Characterization of Human Carpal Bones – a Preliminary Study

Human hand injuries account for a significant number of accidents of young adults (mostly sports injuries) and elderly people. The most vulnerable part of the hand is the wrist, a construct consisting of numerous bones and ligaments. The hand is a complex structure, the mechanical behavior is hard to describe, and also it is sometimes hard to correctly diagnose the injuries. The goal of the present research is to create a quickly and inexpensive measurement method to characterize the geometrical and mechanical properties of carpal bones.The method presented is suitable to properly characterize the intact and damaged geometries of different carpal bones (capitate scaphoid, trapezium, pisiform). 3D models of intact and failed bones are determined by a 3D scanner, mechanical properties are determined with high-speed compression load (700 mm/min), which represents the fracture by falling down. According to the test results, the 3D scanning technique provided valuable geometrical data for cross-section calculation (scan before the test) and for analysis of the failure mode of the bones (scan after the test). The modulus of elasticity data for finite element simulation can be determined by the high-speed compression tests

A gamma-sugárzás hatása különféle ínak mechanikai tulajdonságaira – statikus vizsgálatok

Az allográftok szerepe a szalagok pótlásában fokozatosan nő. Fontos kérdés azonban, hogy a sterilizáció és a tárolás hogyan befolyásolja a fizikai és a mechanikai tulajdonságokat. A mechanikai tulajdonságokat a statikus és dinamikus szakítóvizsgálatokkal különböző biomechanikai paraméterek, mint például húzó rugalmassági modulus, szakadási nyúlás, maximális erő határozható meg. Jelen kutatás célja annak elemzése, hogy 5 különböző fajta ín (Achilles, quadriceps, semitendinosus + gracilis - STG), tibialis anterior - TA, peroneus longus - PL) esetében a különböző sterilizációs módszerek (fagyasztás, fagyasztás+ alacsony dózisú gamma sugárzás, fagyasztás+ magas dózisú gamma sugárzás) hogyan változtatják meg a statikus mechanikai vizsgálatból kapott húzó rugalmassági modulus, maximális erő, nyúlás a maximális erőnél és a szakadási nyúlás értékeit, illetve korábbi dinamikus eredményekhez képest milyen eltérés figyelhető meg. A vizsgálatba 152 darab ínt vontunk be. Az eredmények alapján megállapítható, hogy a dinamikus vizsgálat eredményei nem térnek el a statikus vizsgálat eredményeitől. Az eredmények azt is jól mutatják, hogy a magas dózisú gamma-sugárzás nem alkalmas a sterilizálásra, valamint az Achilles, a quadriceps és az STG ín típusokat nem célszerű a jövőben vizsgálni, mivel a mechanikai paraméterei a sterilizálás következtében szignifikánsan romlanak. Jelen vizsgálat eredményei alapján a sterilizálás a PL és TA ínak maximális erő és a rugalmassági modulus paramétereit változtatják meg a legkisebb mértékben.&nbsp

Stiffening effect of human tendons during strain controlled fatigue loading

The goals of our study were to evaluate the biomechanical differences between five tendons and the changes in biomechanical properties caused by low cycle fatigue loading. Achilles, quadriceps, semitendinosus + gracilis (STG), tibialis anterior (TA) and the peroneus longus (PL) were harvested from 8 donors. The grafts were removed and placed in a radio-cryoprotectant solution and slowly cooled and stored at -78 ° C. The load was defined as a sinusoid function, the starting values are assigned to a peak load of 250 N and a minimum load of 0 N. Data was recorded in the 2th, 4th, 8th, 16th, 32nd, 64th, 128th, 256th, 515th and 1000th cycle. In the given cycles the whole measured waveform was registered. Young modulus of elasticity was calculated. To compare the biomechanical behavior of the different tendons the Young’s modulus values were evaluated in the 64th, 128th, 256th, 512th and 1000th cycles. While in case of PL and STG tendons the change is apperantly linear in the investigated range, in case of the Achilles, quadriceps and TA tendons there is a region where a significant change in modulus occurs

Modulation of cortical resting state functional connectivity during a visuospatial attention task in Parkinson's disease

Visual dysfunction is a recognized early symptom of Parkinson's disease (PD) that partly scales motor symptoms, yet its background is heterogeneous. With additional deficits in visuospatial attention, the two systems are hard to disentangle and it is not known whether impaired functional connectivity in the visual cortex is translative in nature or disrupted attentional modulation also contributes. In this study, we investigate functional connectivity modulation during a visuospatial attention task in patients with PD. In total, 15 PD and 16 age-matched healthy controls performed a visuospatial attention task while undergoing fMRI, in addition to a resting-state fMRI scan. Tensorial independent component analysis was used to investigate task-related network activity patterns. Independently, an atlas-based connectivity modulation analysis was performed using the task potency method. Spearman's rank correlation was calculated between task-related network expression, connectivity modulation, and clinical characteristics. Task-related networks including mostly visual, parietal, and prefrontal cortices were expressed to a significantly lesser degree in patients with PD (p < 0.027). Resting-state functional connectivity did not differ between the healthy and diseased cohorts. Connectivity between the precuneus and ventromedial prefrontal cortex was modulated to a higher degree in patients with PD (p < 0.004), while connections between the posterior parietal cortex and primary visual cortex, and also the superior frontal gyrus and opercular cortex were modulated to a lesser degree (p < 0.001 and p < 0.011). Task-related network expression and superior frontal gyrus-opercular cortex connectivity modulation were significantly associated with UPDRSIII motor scores and the Hoehn-Yahr stages (R = -0.72, p < 0.006 and R = -0.90, p < 0.001; R = -0.68, p < 0.01 and R = -0.71, p < 0.007). Task-related networks function differently in patients with PD in association with motor symptoms, whereas impaired modulation of visual and default-mode network connectivity was not correlated with motor function