scholarly journals Mechanical Effects of Lag Screw Retightening in a Simulated Hindfoot Arthrodesis Model

2021 ◽  
Vol 6 (2) ◽  
pp. 247301142110152
Author(s):  
Amanda L. Rugg ◽  
Melissa R. Requist ◽  
Brooks W. Johnson ◽  
Michelle M. Son ◽  
Alicia Alvarez ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Wound Closure ◽  
Relaxation Response ◽  
Optimum Time ◽  
Level Of Evidence ◽  
Maximum Compression ◽  
Lag Screw ◽  
Average Maximum ◽  
Hindfoot Arthrodesis ◽  
Over Time

Background: Nonunion following hindfoot arthrodesis may be caused by failure to maintain compression at the arthrodesis site. The ability of lag screws, commonly used in arthrodesis, to maintain compression in hindfoot bones has not been well characterized. The aim of this work was to quantify the stress relaxation response of hindfoot bone with initial and repeated compression with a lag screw. Methods: Ten sets of 25-mm-diameter bone cylinders were cut from the talus and calcaneus in fresh-thawed cadaveric feet. A load cell was compressed between cylinders with an 8.0-mm partially threaded cannulated lag screw simulating arthrodesis. For 7 sets, screws were tightened by 3 quarter-turns, rested for 3 minutes, retightened 1 quarter-turn, and rested for 30 minutes. Three sets served as controls in which screws were not retightened. Results: Maximum compression after initial screw tightening and retightening averaged 275 and 337 N ( P = .07), respectively. Compression 3 minutes after initial screw tightening and retightening averaged 199 and 278 N ( P = .027), respectively. The compression recorded 3 minutes after screw retightening was an average of 40% higher than that recorded 3 minutes after initial tightening. The average compression 30 minutes after screw retightening was 255 N, a compression loss of 25% from the average maximum compression after retightening. Eighty percent of this compression loss happened in an average of 5.5 minutes. Conclusion: Hindfoot bones exhibit compression loss over time during simulated arthrodesis. Compression maintenance in bone is improved with screw retightening. Further work is needed to understand the mechanism of action and determine optimum time for recompression. Clinical Relevance: Retightening lag screws before wound closure may improve compression at the arthrodesis site and thereby decrease the chance of nonunion. Level of Evidence: N/A, laboratory experiment.

scholarly journals Does Lag Screw Retightening Improve Compression in Hindfoot Arthrodesis?

2020 ◽  
Vol 5 (4) ◽  
pp. 2473011420S0007
Author(s):  
Amanda Rugg ◽  
Melissa Requist ◽  
Brooks Johnson ◽  
Michelle Son ◽  
Alicia Alvarez ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Causative Factor ◽  
Delayed Union ◽  
Direct Compression ◽  
Maximum Compression ◽  
Non Union ◽  
Lag Screw ◽  
Inferior Aspect ◽  
Time Required ◽  
Hindfoot Arthrodesis

Category: Hindfoot; Ankle; Ankle Arthritis Introduction/Purpose: Non-union and delayed union are common complications following hindfoot arthrodesis. The failure to obtain and maintain compression at the arthrodesis site may be a causative factor. Partially threaded cannulated ‘lag’ screws are commonly used for fixation in hindfoot arthrodesis; however, the ability of these screws to maintain compression in the hindfoot bones has not been well-characterized. The goals of this work were to: 1) quantify the stress relaxation response of hindfoot bones when compressed with a lag screw, particularly compression change upon screw retightening, and 2) compare the results to prior studies on stress relaxation in direct bone compression. Methods: 12 pairs of calcaneus, talus and tibia bone cylinders, 25mm in diameter, were cut with a keyhole saw from fresh thawed cadaveric feet. The bone cylinders were prepared for simulated arthrodesis by removing the cartilage and flattening the subchondral surface with an oscillating saw. A Futek LTH 300 donut load cell and two metal washers were sandwiched between the two bone cylinders. An 8.0mm partially threaded cannulated lag screw (Smith and Nephew) was placed from the posterior- inferior aspect of the calcaneus cylinder to the anterior-superior aspect of the talus cylinder to simulate subtalar arthrodesis, or from the superior aspect of the tibia cylinder to the inferior aspect of the talus cylinder. Compression was recorded continuously as the screws were tightened by three-quarters of a turn and left untouched for 3 minutes. Recording continued as the screws were retightened one quarter-turn and then left untouched for 30 additional minutes. Results: Both initial and subsequent compression with a lag screw demonstrated a stress relaxation pattern, with increased maximum compression and slowed decay upon retightening. Maximum compression after three quarter-turns and retightening averaged 284 N and 351 N, respectively (n=12; t=-2.55; p=0.0136). Time to decay to 80% of maximum compression after three quarter-turns and retightening averaged 34 and 528 (n=9; t=-2.59; p=0.0159) seconds, respectively, compared to 21 seconds for direct compression. Compression loss 30 minutes after retightening averaged 25.5% (SD=8.8%), compared to 34.3% for direct compression. Conclusion: The maximum compression attained following retightening was significantly greater than the maximum compression attained after initial tightening. The time required to reach 80% of maximum compression was significantly longer after subsequent compared to initial maximum compression. These findings suggest that screw retightening before surgical wound closure may slow compression loss, which could increase the likelihood of successful arthrodesis. Lag screw compression resulted in a lower percent compression loss and loss rate compared to direct compression, which was previously used to describe bone viscoelasticity.

Effect of thermal exposure on the strength and stress relaxation response of AA-7075-T6 material

2021 ◽  
pp. 124791
Author(s):  
M.Z. Butt ◽  
Samee Ullah ◽  
M. Rashid Khan ◽  
Sajjad Ahmad ◽  
Syed Zafar Ilyas
Keyword(s):  
Stress Relaxation ◽  
Thermal Exposure ◽  
Relaxation Response ◽  
Aa 7075

scholarly journals Significant increase in quantity and quality of knee arthroplasty related research in KSSTA over the past 15 years

2021 ◽  
Author(s):  
Stephanie Kirschbaum ◽  
Thilo Kakzhad ◽  
Fabian Granrath ◽  
Andrzej Jasina ◽  
Jakub Oronowicz ◽  
...  
Keyword(s):  
Knee Arthroplasty ◽  
Special Topic ◽  
Computer Assisted ◽  
Time Interval ◽  
Search Term ◽  
Level Of Evidence ◽  
The Past ◽  
Patient Reported ◽  
Over Time ◽  
Number Of Authors

Abstract Purpose This study aimed to evaluate both publication and authorship characteristics in Knee Surgery, Sports Traumatology, Arthroscopy journal (KSSTA) regarding knee arthroplasty over the past 15 years. Methods PubMed was searched for articles published in KSSTA between January 1, 2006, and December 31st, 2020, utilising the search term ‘knee arthroplasty’. 1288 articles met the inclusion criteria. The articles were evaluated using the following criteria: type of article, type of study, main topic and special topic, use of patient-reported outcome scores, number of references and citations, level of evidence (LOE), number of authors, gender of the first author and continent of origin. Three time intervals were compared: 2006–2010, 2011–2015 and 2016–2020. Results Between 2016 and 2020, publications peaked at 670 articles (52%) compared with 465 (36%) published between 2011 and 2016 and 153 articles (12%) between 2006 and 2010. While percentage of reviews (2006–2010: 0% vs. 2011–2015: 5% vs. 2016–2020: 5%) and meta-analyses (1% vs. 6% vs. 5%) increased, fewer case reports were published (13% vs. 3% vs. 1%) (p < 0.001). Interest in navigation and computer-assisted surgery decreased, whereas interest in perioperative management, robotic and individualized surgery increased over time (p < 0.001). There was an increasing number of references [26 (2–73) vs. 30 (2–158) vs. 31 (1–143), p < 0.001] while number of citations decreased [30 (0–188) vs. 22 (0–264) vs. 6 (0–106), p < 0.001]. LOE showed no significant changes (p = 0.439). The number of authors increased between each time interval (p < 0.001), while the percentage of female authors was comparable between first and last interval (p = 0.252). Europe published significantly fewer articles over time (56% vs. 47% vs. 52%), whereas the number of articles from Asia increased (35% vs. 45% vs. 37%, p = 0.005). Conclusion Increasing interest in the field of knee arthroplasty-related surgery arose within the last 15 years in KSSTA. The investigated topics showed a significant trend towards the latest techniques at each time interval. With rising number of authors, the part of female first authors also increased—but not significantly. Furthermore, publishing characteristics showed an increasing number of publications from Asia and a slightly decreasing number in Europe. Level of evidence IV.

scholarly journals Early morbidity associated with fasciotomies for acute compartment syndrome in children

2018 ◽  
Vol 12 (5) ◽  
pp. 480-487 ◽  
Author(s):  
K. B. L. Lim ◽  
T. Laine ◽  
J. Y. Chooi ◽  
W. K. Lye ◽  
B. J. Y. Lee ◽  
...  
Keyword(s):  
Hospital Stay ◽  
Compartment Syndrome ◽  
Wound Closure ◽  
Case Series ◽  
Skin Grafting ◽  
Acute Compartment Syndrome ◽  
Inpatient Stay ◽  
Wound Infections ◽  
Short Term ◽  
Level Of Evidence

Purpose Acute compartment syndrome (ACS) requires urgent fasciotomy to decompress the relevant muscle compartment/s prior to onset of irreversible myonecrosis and nerve injury. A fasciotomy is not a benign procedure. This study aims to describe and quantify early morbidity directly associated with fasciotomies for ACS in children. Methods Clinical charts of 104 children who underwent 112 fasciotomies over a 13-year period at a tertiary children’s hospital were reviewed. The following were analyzed: ACS aetiology, fasciotomy site, number of subsequent procedures, method of wound closure, short-term complications and length of hospital stay. Results Short-term complications included wound infections (6.7%) and the need for blood transfusion (7.7%). Median number of additional operations for wound closure was two (0 to 10) and median inpatient stay was 12 days (3 to 63; SD 11.7). After three unsuccessful attempts at primary closure, likelihood of needing skin grafting for coverage exceeded 80%. Analyses showed that fasciotomy-wound infections were associated with higher risk for four or more closure procedures. Number of procedures required for wound closure correlated with longer inpatient stay as did ACS associated with non-orthopaedic causes. Conclusion Fasciotomy is associated with significant early morbidity, the need for multiple closure operations, and prolonged hospital stay. The decision for fasciotomy needs careful consideration to avoid unnecessary fasciotomies, without increasing the risk of permanent injury from missed or delayed diagnosis. Skin grafting should be considered after three unsuccessful closure attempts. Less invasive tests or continuous monitoring (for high-risk patients) for compartment syndrome may help reduce unnecessary fasciotomies. Level of Evidence Level IV, Case series

Post-Fatigue Creep and Stress Relaxation Response of a Hybrid Polymer Composite

2017 ◽  
Author(s):  
Raghu V. Prakash ◽  
Monalisha Maharana
Keyword(s):  
Stress Relaxation ◽  
Polymer Composites ◽  
Polymer Composite ◽  
Fatigue Loading ◽  
Synthetic Fiber ◽  
Relaxation Response ◽  
Hybrid Polymer ◽  
Fatigue Cycling ◽  
Creep And Stress Relaxation ◽  
Hybrid Polymer Composite

Polymer composites have a characteristic, composition specific visco-elastic property which influences the damage progression during fatigue cycling. While some researchers have studied the time dependent constitutive response of polymer composites during the first cycle of fatigue loading, very few have experimentally investigated the dependence of visco-elastic response of built-up polymer composite materials at various stages of fatigue cycling [1]. Our earlier studies on fatigue response of polymer composites focused primarily on the stiffness degradation as a function of applied cycles of loading, which represents the gross response of the material [2]. While doing such an experiment, complimentary experimental techniques to measure the temperature evolution was attempted through the use of infrared thermal imaging technique, which gave some insight into the change in temperature response as a function of fatigue cycling. However, there was no systematic measurement of creep and stress relaxation response of the composite material as a function of induced fatigue damage. The present paper describes the results of creep and stress-relaxation obtained during uni-axial fatigue loading of a hybrid polymer composite material. For this purpose, a woven carbon fiber mat was chosen as the synthetic fiber and Flax fiber in the unidirectional form was chosen as the natural fiber that is laid between the two layers of woven carbon fiber mat. Epoxy LY 556 and hardener Araldite® was used for building up of composite laminate by hand-lay-up technique. Dog-bone shaped tensile specimens with a gage width of 13 mm and gage length of 57 mm were extracted from the 250 × 250 mm sq. plate laminate of 2.1 mm thickness using a numerical controlled milling machine. The specimens were tested at 35% of their median tensile strengths under fatigue at a positive stress ratio (Pmin/Pmax) of 0.1 in tension-tension loading. Prior to start of fatigue loading, the specimens were held in load control and the strain in the gage length was measured for understanding the creep response over 2500 seconds. For stress-relaxation characterization, the specimens were held in extensometer control over a period of 2500 sec. The creep and stress relaxation tests were carried out after periodic intervals of fatigue cycling. It was observed that in the case of un-impacted specimens, the creep rate is consistent with the stiffness variation, which in turn, is dependent on the number of fatigue cycles - till it showed signs of de-lamination. Thereafter it was governed by the woven synthetic fiber response. Similarly, the stress relaxation response was found to decrease with increasing fatigue cycles. In case of impacted specimens, the local deformation had a prominent role in terms of creep and stress relaxation response.

Performance of self-centering steel moment frame considering stress relaxation in prestressed cables

2020 ◽  
Vol 23 (9) ◽  
pp. 1813-1822
Author(s):  
Seyyed Morteza Asadolahi ◽  
Nader Fanaie
Keyword(s):  
Stress Relaxation ◽  
Stress Reduction ◽  
Original Position ◽  
Dissipated Energy ◽  
Moment Frame ◽  
Steel Moment Frame ◽  
Moment Resisting Frames ◽  
Moment Resisting Frame ◽  
Moment Resisting ◽  
Over Time

Buildings can be designed to limit the earthquake-induced damage to members that can easily be repaired. Self-centering moment-resisting frames can be used as effective structural systems for this purpose. Self-centering moment-resisting frames with prestressed cables are able to return the structure to its original position after the earthquake. The internal forces in self-centering moment-resisting frames are transferred between the beam and the column by post-tensioned cables. As a main member of self-centering connections, prestressed cables play a significant role in such systems. Cable tension decreases over time due to the effect of stress relaxation on the performance of the system. Stress relaxation is a time-dependent phenomenon causing stress reduction over time in the members prestressed at a constant strain. Therefore, the effect of stress relaxation on the performance of self-centering moment-resisting frames can be significant. In this article, after simulating and validating a moment-resisting frame with self-centering connections, stiffness and moment–rotation hysteresis diagrams were analyzed after 0, 1, 5, 10, and 20 years of cable prestressing. According to the results, two equations were presented to estimate the reduction in the connection stiffness and dissipated energy by the system based on prestressing level and the time after prestressing. The proposed equations could be used to model semi-rigid connections.

Continuous suturing as a wound closure technique for circumcisions

2019 ◽  
Vol 12 (6) ◽  
pp. 470-473
Author(s):  
Manoj Ravindraanandan ◽  
Herman Fernando ◽  
Shahjahan Aslam
Keyword(s):  
Male Circumcision ◽  
Wound Closure ◽  
Suture Technique ◽  
Complication Rates ◽  
Continuous Suture ◽  
Single Institution ◽  
Closure Technique ◽  
Level Of Evidence ◽  
Operative Complications ◽  
Low Incidence

Male circumcision is an extremely common urological procedure worldwide, with many variations in technique. Despite the large volume there is a low incidence of complications associated with circumcisions, with the majority being Clavien-Dindo I or II. In this study, we analyse the outcomes and complication rates associated with a continuous wound closure following a male circumcision. Methods: In a urology department from a single institution, 201 male circumcisions with a continuous wound closure were performed in a 4-year period. Outcomes were analysed retrospectively looking at postoperative complications and readmissions to hospital via our clinical portal. Results: No patients had complications that required admission or re-operation at our institution. Conclusion: No major post-operative complications were observed from our cohort. There were also no documented admissions back to our institution with wound healing complications. However, a limitation is that Clavien-Dindo I and II complications and treatment at general practitioner surgeries were not captured and may not accurately represent our complication rates quoted. Nevertheless, we can conclude from these data that closure for a circumcision using a continuous suture technique gives favourable outcomes with acceptable complication rates. Level of evidence: Not applicable for this multicentre audit.

Impairment of vascular function is associated with an age-related increase of lipid peroxidation in rats

1996 ◽  
Vol 271 (6) ◽  
pp. R1625-R1631 ◽  
Author(s):  
S. T. Davidge ◽  
C. A. Hubel ◽  
M. K. McLaughlin
Keyword(s):  
Nitric Oxide ◽  
Lipid Peroxidation ◽  
Vascular Function ◽  
Mesenteric Arteries ◽  
Relaxation Response ◽  
Female Rat ◽  
Cyclooxygenase Inhibition ◽  
Age Related ◽  
Old Rats ◽  
Over Time

We tested the hypothesis that an increase in endogenous lipid peroxidation over time is associated with an impairment of endothelium-dependent vascular function in resistance-sized mesenteric arteries that is due in part to alterations of arachidonate metabolism. Susceptibility to red blood cell hemolysis and sera levels of malondialdehyde were increased (P < 0.05) from 20 wk (n = 12) to 40 wk (n = 12) in female Sprague-Dawley rats. Arteries were studied in a myograph by examining the endothelial modification of phenylephrine vasoconstriction and the relaxation responses of the mesenteric arteries to methacholine. We observed the following. 1) An increase in sensitivity to alpha 1-adrenergic stimulation occurred between 20 and 40 wk of age. Cyclooxygenase inhibition decreased the sensitivity to phenylephrine only in the arteries from the 40-wk-old rats, indicating that a cyclooxygenase-dependent vasoconstrictor was modifying the phenylephrine response. 2) Nitric oxide synthase inhibition caused a greater increase in phenylephrine sensitivity in the arteries from the 20-wk-old rats than those from the 40-wk-old rats, indicating that nitric oxide modification of phenylephrine sensitivity decreased with age. 3) Endothelium-independent relaxations were not affected between 20 and 40 wk of age. 4) At 40 wk, the sensitivity to the methacholine-mediated relaxation response decreased without impairing the maximal relaxation response. This reduced sensitivity was removed with cyclooxygenase inhibition or thromboxane A2/prostaglandin H2 (PGH2) receptor blockade. 5) Aortas from the 40-wk-old rats had an increased expression of PGH synthase. Collectively, these observations indicate that, in the female rat, an increase in lipid peroxidation over time is associated with changes in endothelium-dependent vascular function that were due in part to a cyclooxygenase-dependent vasoconstrictor.

Modeling the Effects of Mixed Flowing Gas (MFG) Corrosion and Stress Relaxation on Contact Interface Resistance

1993 ◽  
Vol 115 (4) ◽  
pp. 404-409 ◽  
Author(s):  
Shrikar Bhagath ◽  
Michael G. Pecht
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Stress Relaxation ◽  
Contact Resistance ◽  
Time Dependence ◽  
Normal Force ◽  
Operating Temperature ◽  
Contact Interface ◽  
Time Stress ◽  
Over Time

This paper presents the development of an initial, “first-cut”, mathematical model for the prediction of electrical interface reliability trends. The model pertains to gold plated contacts subject to loss of normal force and environmental corrosion with time. Stress relaxation over time and temperature in the base metal of the contact is accounted for. Utilizing the results of Mixed Flowing Gas (MFG) tests, the model can be used to estimate the statistical contact resistance at a particular load (normal force), aging and operating temperature in the class II and III environments. An attempt is made to correlate experimental data with the classical Holm’s equation and to introduce time dependence into the equation. Further work is proposed to correlate results with experimental connector performance data.

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