A modified Cryo-Jaw for in vitro biomechanical testing of tendons

The purpose of this study was to develop a new device, which represents a modification of the Cryo-Jaw described by Riemersa and Schamhardt and modified by Hamner et al., for in vitro biomechanical testing of tendons which allows the lower clamp to move in every direction and thus simulate a pathological dislocation of the knee. Tendons are fixed to the device by freezing the clamped part with dry ice. After fixation of their free ends. the lower clamp was rotated 45, translated 1 em, and angled 40 to simulate a knee sprain, Various configurations of bundles were tested: parallel, twisted, and braided. Tests were performed on 10 paired bovine bifurcated digital extensor tendons and 6 paired human hamstring tendons. Grafts were then tested to failure subjected to impulsive load, using a servohydraulic machine. The highest ultimate load recorded for parallel bundles was 4662 +/- 565.71 N for bovine bifurcated digital extensor tendons, and 3057 +/- 475.44 N for human hamstring tendons. In any case, the tendons ruptured midway, well clear of the frozen part; in no case was slippage of the tendons observed. Thus the device proposed allows one to test what happens to the graft of an ACL reconstructed knee during physiological and pathological movements because it can be easily displaced in every direction

Biomechanics of anterior cruciate ligament reconstruction using twisted doubled hamstring tendons

We studied the biomechanical properties of a twisted doubled semitendinosus and gracilis graft. We applied an un-axial load in order to reproduce the kinematics of a reconstructed anterior cruciate ligament (ACL). A modified cryo-jaw clamp system was used to minimize soft tissue slippage. The lower grip, after fixation of the free ends of the tendons, was rotated 45degrees, translated 1 cm, and bent 40degrees, simulating a knee sprain. The graft was tested to failure using a servohydraulic machine. The specimen from one knee of seven unembalmed cadavers was assigned to the untwisted (parallel) bundles group, while its pair was assigned to the twisted group. For the parallel bundles group, the mean maximum load was 1709.3+/-581.9 N, for the twisted group 2428.3+/-475.4 N (P<0.05). The mean stiffness was respectively 213.6+/-72.4 N/mm and 310.3+/-97.3 N/mm (P=0.08). Although caution should be used in extrapolating the results to clinical estimates of the strength of hamstring grafts, the results of the present study could justify the use of twisted semitendinosus and gracilis bundles in ACL reconstruction

Safety, maintenance and nanotechnologies: an introductory state of art about the risk assessment methodologies and the potentialities

Nanotechnology is a science still in process of research and development. Different challenges are still to be solved for their full evaluation especially from the safety and maintenability point of view. The ambition of the present work is a rationalized state of the art of the scientific publications and of the industrial applications, in order to offer a general and critical view and orient possible future applied researches

Single-stance posture analysis by means of a contact resistance variation pressure array sensor

Padov

Decline of physical and cognitive conditions in the elderly measured through the functional reach test and the mini-mental state examination

There are several tests used to evaluate the psychophysical characteristics of the elderly and, of these, the most suitable are the functional reach (FR) test, an index of the aptitude to maintain balance in an upright position, and the mini-mental state examination (MMSE), a global index of cognitive abilities. The sample of elderly people we analyzed involved 50 healthy subjects divided into three age-groups (15 subjects from 55 to 64 years, 19 from 65 to 74 years, and 16 over 75 years of age); they underwent an FR test, which consists first in the measurement of the anthropometric characteristics, then in the execution of the test itself, and finally in the study of the upright posture by the analysis of the center of pressure (COP) trend; they underwent an MMSE as well to evaluate the main areas of the cognitive function concerning space-time orientation, short-term memory, attention ability, calculation ability and constructive praxis. The results of these tests show, according to the age of the subject, a loss of physical performance (FR, FR related to height, and COP displacement), as well as a loss of cognitive abilities; however, in all cases the only significant changes are those between the first and the other two age-groups. Finally, a comparison between FR and MMSE shows a more rapid decline of physical performance compared to cognitive performance. (C) 2009 Elsevier Ireland Ltd. All rights reserved

Stall inception, evolution and control in a low speed axial fan with variable pitch in motion

Obtaining the right pitch in turbomachinery blading is crucial to efficient and successful operations. Engineers adjust the rotor's pitch angle to control the production or absorption of power. Even for low speed fans this is a promising tool. This paper focuses on the inception and the evolution of the flow instabilities in the tip region which drive the stall onset in low speed axial fans. The authors conducted an experimental study to investigate the inception patterns of rotating stall evolution at different rotor blade stagger-angle settings with the aim of speculating on stable operating margin. The authors drove the fan to stall at the design stagger-angle setting and then operated the variable pitch mechanism in order to recover the unstable operation. They measured pressure fluctuations in the tip region of the low-speed axial-flow fan fitted with a variable pitch in motion mechanism, with flush mounted probes. The authors studied the flow mechanisms for spike and modal stall inceptions in this low-speed axial-flow fan which showed relatively small tip clearance. The authors cross-correlated the pressure fluctuations and analyzed the cross-spectra in order to clarify blade pitch, end wall flow, and tip-leakage flow influences on stall inception during the transient at the rotor blades' different stagger-angle settings. The authors observed a rotating instability near the maximum pressure-rise point at both design and low stagger-angle settings. The stall inception patterns were a spike type at the design stagger-angle setting as a result of the interaction between the incoming flow, tip-leakage flow and end wall backflow. © 2012 American Society of Mechanical Engineers

“A modified cryo-jaw for in vitro biomechanical testing of tendons”

The purpose of this study was to develop a new device, which represents a modification of the Cryo-Jaw described by Riemersa and Schamhardt and modified by Hamner et al., for in vitro biomechanical testing of tendons which allows the lower clamp to move in every direction and thus simulate a pathological dislocation of the knee. Tendons are fixed to the device by freezing the clamped part with dry ice. After fixation of their free ends. the lower clamp was rotated 45, translated 1 em, and angled 40 to simulate a knee sprain, Various configurations of bundles were tested: parallel, twisted, and braided. Tests were performed on 10 paired bovine bifurcated digital extensor tendons and 6 paired human hamstring tendons. Grafts were then tested to failure subjected to impulsive load, using a servohydraulic machine. The highest ultimate load recorded for parallel bundles was 4662 +/- 565.71 N for bovine bifurcated digital extensor tendons, and 3057 +/- 475.44 N for human hamstring tendons. In any case, the tendons ruptured midway, well clear of the frozen part; in no case was slippage of the tendons observed. Thus the device proposed allows one to test what happens to the graft of an ACL reconstructed knee during physiological and pathological movements because it can be easily displaced in every direction

Biomechanics of ACL Reconstruction using twisted D-stg; a preliminary report

Montecatini Term