scholarly journals Mechanical Compromise of Partially Lacerated Flexor Tendons

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Jaclyn Kondratko ◽  
Sarah Duenwald-Kuehl ◽  
Roderic Lakes ◽  
Ray Vanderby
Keyword(s):  
Stress Concentration ◽  
Cross Section ◽  
Viscoelastic Properties ◽  
Maximum Stress ◽  
Surgical Repair ◽  
Cross Sectional ◽  
Flexor Tendons ◽  
Percent Loss ◽  
Before And After ◽  
Insight Into

Tendons function to transmit loads from muscle to move and stabilize joints and absorb impacts. Functionality of lacerated tendons is diminished, however clinical practice often considers surgical repair only after 50% or more of the tendon is lacerated, the “50% rule.” Few studies provide mechanical insight into the 50% rule. In this study cyclic and static stress relaxation tests were performed on porcine flexor tendons before and after a 0.5, 1.0, 2.0, or 2.75 mm deep transverse, midsubstance laceration. Elastic and viscoelastic properties, such as maximum stress, change in stress throughout each test, and stiffness, were measured and compared pre- and post-laceration. Nominal stress and stiffness parameters decreased, albeit disproportionately in magnitude, with increasing percent loss of cross-sectional area. Conversely, mean stress at the residual area (determined using remaining intact area at the laceration cross section) exhibited a marked increase in stress concentration beginning at 47.2% laceration using both specified load and constant strain analyses. The marked increase in stress concentration beginning near 50% laceration provides mechanical insight into the 50% rule. Additionally, a drastic decrease in viscoelastic stress parameters after only an 8.2% laceration suggests that time-dependent mechanisms protecting tissues during impact loadings are highly compromised regardless of laceration size.

Acoustic Rhinometric Assessment of the Nasal Valve

1997 ◽  
Vol 11 (5) ◽  
pp. 379-386 ◽  
Author(s):  
Renato Roithmann ◽  
Jerry Chapnik ◽  
Noe Zamel ◽  
Sergio Menna Barreto ◽  
Philip Cole
Keyword(s):  
Cross Section ◽  
Nasal Obstruction ◽  
Cross Sectional Area ◽  
Acoustic Rhinometry ◽  
Sectional Area ◽  
Nasal Valve ◽  
Cross Sectional ◽  
Nasal Cavities ◽  
Before And After ◽  
Valve Area

The aims of this study are to assess nasal valve cross-sectional areas in healthy noses and in patients with nasal obstruction after rhinoplasty and to evaluate the effect of an external nasal dilator on both healthy and obstructive nasal valves. Subjects consisted of (i) volunteers with no nasal symptoms, nasal cavities unremarkable to rhinoscopy and normal nasal resistance and (ii) patients referred to our clinic complaining of postrhinoplasty nasal obstruction. All subjects were tested before and after topical decongestion of the nasal mucosa and with an external nasal dilator. In 79 untreated healthy nasal cavities the nasal valve area showed two constrictions: the proximal constriction averaged 0.78 cm2 cross-section and was situated 1.18 cm from the nostril, the distal constriction averaged 0.70 cm2 cross-section at 2.86 cm from the nostril. Mucosal decongestion increased cross-sectional area of the distal constriction significantly (p < 0.0001) but not the proximal. External dilation increased cross-sectional area of both constrictions significantly (p < 0.0001). In 26 post-rhinoplasty obstructed nasal cavities, only a single constriction was detected, averaging 0.34 cm2 cross-section at 2.55 cm from the nostril and 0.4 cm2 at 2.46 cm from the nostril, before and after mucosal decongestion respectively. External dilation increased the minimum cross-sectional area to 0.64 cm2 in these nasal cavities (p < 0.0001). We conclude that the nasal valve area in patients with postrhinoplasty nasal obstruction is significantly smaller than in healthy nasal cavities as shown by acoustic rhinometry. Acoustic rhinometry objectively determines the structural and mucovascular components of the nasal valve area and external dilation is an effective therapeutical approach in the management of nasal valve obstruction.

A Comparison of Two Monofilament Suture Materials for Repair of Partial Flexor Tendon Lacerations: A Controlled In-vitro Study

2017 ◽  
Vol 22 (01) ◽  
pp. 18-22
Author(s):  
Abhinav Gulihar ◽  
Thomas Whitehead-Clarke ◽  
Ladan Hajipour ◽  
Joseph J. Dias
Keyword(s):  
Surgical Repair ◽  
Flexor Tendon ◽  
Tendon Repair ◽  
In Vitro Study ◽  
Suture Repair ◽  
Suture Materials ◽  
Flexor Tendons ◽  
Before And After ◽  
Materials Used

Background: Surgical repair is advocated for flexor tendon lacerations deeper than 70%. Repair can be undertaken with different suturing techniques and using different materials. Different materials used for tendon repair will have a different gliding resistance (GR) at the joint. Previous studies have compared strength of repair and gliding resistance for various braided suture materials and for 100% laceration of flexor tendons. We directly compare the GR of two monofilament sutures when used for a peripheral running suture repair of partially lacerated tendons. Methods: Sixteen flexor tendons and A2 pulleys were harvested from Turkey feet. They were prepared, partially lacerated to 50% depth, and then repaired with a core suture (modified Kessler technique with 4-0 Ethibond) as well as an additional superficial running suture of either 6-0 Prolene or Nylon (half randomised to each). Gliding resistance was measured for all tendons before and after repair, at different flexion angles (40 and 60 degrees) and for different loads (2N and 4N). Results: After surgical repair, gliding resistance was increased for all tendons (P < 0.01). The tendons repaired with Prolene had a higher mean gliding resistance than those repaired with Nylon (P = 0.02). Increased flexion angle and load amplified the gliding resistance (both P < 0.01). Conclusions: 6-0 Nylon was associated with a lower gliding resistance than 6-0 Prolene but the minor differences bare unknown clinical significance.

Stresses in Eccentric Stepwise Discontinuous Rings With Transition Section

1968 ◽  
Vol 12 (04) ◽  
pp. 269-278
Author(s):  
Arnold Allentuch ◽  
Joseph Kempner
Keyword(s):  
Stress Distribution ◽  
Cross Section ◽  
Maximum Stress ◽  
Circular Cylindrical Shell ◽  
Radial Line ◽  
Cross Sectional ◽  
Line Load ◽  
Transition Section ◽  
Parameter Values ◽  
Interaction Problem

The stress distribution in a ring of nonuniform cross section under the action of a uniform radial line load is obtained. The solution is an approximation to the exact interaction problem of a reinforced circular cylindrical shell under hydrostatic pressure. The ring is fabricated in three segments; one segment, whose cross-sectional area varies according to a power function, connects two uniform segments. By a proper choice of parameter values the ring geometry can be reduced to two segments, one of uniform depth, the other of continuously varying depth. Several sets of parameters are chosen for numerical calculations. Within these sets only the length of the transition section changes. Thus an appraisal of the importance of the transition section in reducing the maximum stress is made. The stress distribution in a frame with different lengths of transition section is obtained.

STRUCTURAL CHANGES OF THE CARPAL TUNNEL, MEDIAN NERVE AND FLEXOR TENDONS IN MRI BEFORE AND AFTER ENDOSCOPIC CARPAL TUNNEL RELEASE

Hand Surgery ◽  
2014 ◽  
Vol 19 (02) ◽  
pp. 193-198 ◽  
Author(s):  
Toshimitsu Momose ◽  
Shigeharu Uchiyama ◽  
Seneki Kobayashi ◽  
Hiroyuki Nakagawa ◽  
Hiroyuki Kato
Keyword(s):  
Median Nerve ◽  
Carpal Tunnel ◽  
Structural Changes ◽  
Carpal Tunnel Release ◽  
Carpal Bone ◽  
Cross Sectional ◽  
Flexor Tendons ◽  
Endoscopic Carpal Tunnel Release ◽  
Before And After ◽  
Magnetic Resonance Imaging Mri

The purpose of this study is to investigate the structural changes of the carpal tunnel, median nerve, and flexor tendons in magnetic resonance imaging (MRI) before and after endoscopic carpal tunnel release (ECTR). We studied 36 hands undergoing ECTR. In MRI, the cross-sectional area of the carpal tunnel and the median nerve at the hamate and the pisiform levels were measured. The distance from the volar side of carpal bone to the median nerve or tendons and the volar displacement were measured. In post-operative MRI, the transverse carpal ligament could not be well delineated and the carpal tunnel was significantly enlarged both at the hamate and pisiform levels. The median nerve was enlarged at the hamate level. The median nerve and flexor tendons significantly moved to the volar side. The volar displacement of the median nerve and flexor digitorum superficialis in the long and ring fingers was greater than the other tendons.

Reinforced Elliptical Holes in Stressed Plates

1957 ◽  
Vol 61 (562) ◽  
pp. 688-693 ◽  
Author(s):  
Raymond Hicks
Keyword(s):  
Stress Distribution ◽  
Cross Section ◽  
Maximum Stress ◽  
Elliptical Hole ◽  
Pressure Vessels ◽  
Stress System ◽  
Sectional Area ◽  
Principal Stresses ◽  
Cross Sectional ◽  
Elliptical Holes

SummaryThis paper considers the problem of a reinforced elliptical hole in a plate under the action of a principal stress system of the type found in cylindrical and ellipsoidal pressure vessels. That is, stress systems in which the ratio of the principal stresses is not greater than two to one. It is shown that when the ratio of the major and minor axes of the ellipse can be chosen arbitrarily, practical reinforcements can be designed to give a maximum stress around the hole which is only slightly greater than the maximum stress in a similarly loaded plate with no hole. General expressions are obtained for the stress distribution in the plate around the hole, for the stress acting on a normal cross section of the reinforcement, and for the cross-sectional area of a reinforcement which gives a small stress concentration. These are used to find the variation in the stress distribution around the hole due to reinforcements having different cross-sectional areas when the applied principal stresses are in the ratio of two to one and Poisson's ratio for the material of the plate and reinforcement has practical values.

Partial Lacerations of Flexor Tendons in Children

1997 ◽  
Vol 22 (3) ◽  
pp. 377-380 ◽  
Author(s):  
S. STAHL ◽  
T. KAUFMAN ◽  
V. BIALIK
Keyword(s):  
Surgical Repair ◽  
Flexor Tendon ◽  
Early Mobilization ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Tendon Tear ◽  
Cross Sectional ◽  
Flexor Tendons ◽  
Partial Division

We compared the outcome of 17 partially lacerated (less than 75% of cross-sectional area) flexor tendons in children treated by surgical repair to that of 19 tendons treated conservatively by early mobilization. The outcome of both groups was similarly favourable. No complications, such as triggering or complete tendon tear, were found in either group. We advocate early mobilization in children in whom a partial division of the flexor tendon is diagnosed clinically. Exploration should be carried out only in doubtful cases to exclude complete division of the tendon.

Finite Element Analysis of Stress for Nozzle Zone at Channel of Pressure Vessel

2012 ◽  
Vol 490-495 ◽  
pp. 2165-2168 ◽  
Author(s):  
Xiao Lv ◽  
Shi Jie Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Pressure Vessel ◽  
Maximum Stress ◽  
Concentration Region ◽  
Element Analysis ◽  
Stress Concentration Region ◽  
Before And After ◽  
The Status

With the development of petrochemical industry, the status of pressure vessel has become increasingly important, and higher requirements are introduced for the security of nozzle zone at the pressure bearing region of pressure vessel. In order to study the stress status of nozzle zone at the channel of pressure vessel, solid modeling for channel and straight pipe was performed with ANSYS software. Through finite element analysis and calculation, the stress concentration region of channel was determined and the reason was analyzed. In addition, the nozzle zones of the model before and after loading were compared. The result reveals that symmetrical stress concentration region lies at the junction of channel and pipe. The maximum stress is located at the inside of nozzle zone of channel and less than the yield stress of material.

scholarly journals Changes in the structure of earnings of informal street traders

2014 ◽  
Vol 14 (1) ◽  
Author(s):  
Chris W. Callaghan
Keyword(s):  
Regression Analysis ◽  
Inner City ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Potential Influence ◽  
Cross Sectional ◽  
Before And After ◽  
Chi Squared ◽  
Using Data ◽  
Insight Into

Purpose/objective: The purpose of this research is to investigate the influence of the 2008 xenophobic events on the structure of earnings of street traders in inner-city Johannesburg and to provide recommendations to policymakers.Problem investigated: The xenophobic events of 2008 are well documented, but absent from the literature is the potential influence on the earnings of foreign street traders. This study investigates this influence through analysis of data from before and after the events.Design and methodology: The study applies an exploratory cross-sectional research design using data from three different samples. Mann-Whitney and Chi-squared measures are applied together with exploratory multiple linear regression analysis to generate insight into the relationships between earnings and differences by origin.Findings and implications: In 2009 the earnings structure of the sector changed. In 2008 and 2010, the earnings of foreign traders are higher, whereas in 2009 these traders earned less than local traders. It is argued that the xenophobic events might have resulted in a temporary restructuring of earnings.Originality or value of the research: This study makes a contribution through exploratory findings that document a change in the structure of earnings of foreign street traders.Conclusion: A change in the structure of earnings of foreign street traders occurred after the xenophobic events of 2008. Although association cannot ascribe causality, it is argued that this change may be related to these events.

Study on the Stress Distribution of the Piston Rod Fillet Based on the Nonlinear Finite Element Method

2014 ◽  
Vol 1070-1072 ◽  
pp. 1848-1851
Author(s):  
Xiao Yu Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Concentration ◽  
Stress Distribution ◽  
Cross Section ◽  
Maximum Stress ◽  
Nonlinear Finite Element ◽  
Nonlinear Finite Element Method ◽  
Fillet Radius ◽  
Element Method

Because of discontinuity of the shape, the piston rod of rapping device is liable to occur stress concentration phenomenon, leading to fracture of the piston rod. At work, the maximum stress of piston rod which took place in the cross section of the geometric mutations varied with the change of the fillet radius, under the same load, it analyzed the influence of different fillet radius on fracture of the piston rod via ANSYS/LS-DYNA finite element. The results showed that it can meet the requirements when the fillet radius was 5 mm.

Mass Determination by Direct Measurement of Electron Scattering

1975 ◽  
Vol 33 ◽  
pp. 240-241
Author(s):  
M. K. Lamvik ◽  
A. V. Crewe
Keyword(s):  
Cross Section ◽  
Electron Scattering ◽  
Mass Density ◽  
Variable Mass ◽  
Scattering Cross Section ◽  
Mass Determination ◽  
Number Density ◽  
Cross Sectional ◽  
Thin Slice ◽  
Scattering Cross

If a molecule or atom of material has molecular weight A, the number density of such units is given by n=Nρ/A, where N is Avogadro's number and ρ is the mass density of the material. The amount of scattering from each unit can be written by assigning an imaginary cross-sectional area σ to each unit. If the current I0 is incident on a thin slice of material of thickness z and the current I remains unscattered, then the scattering cross-section σ is defined by I=IOnσz. For a specimen that is not thin, the definition must be applied to each imaginary thin slice and the result I/I0 =exp(-nσz) is obtained by integrating over the whole thickness. It is useful to separate the variable mass-thickness w=ρz from the other factors to yield I/I0 =exp(-sw), where s=Nσ/A is the scattering cross-section per unit mass.

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