Effect of Clamp Type on Type II External Fixator Stiffness

1999 ◽  
Vol 12 (04) ◽  
pp. 178-182 ◽  
Author(s):  
H. M. Wotton ◽  
K. H. Kraus
Keyword(s):  
Linear Regression ◽  
External Fixator ◽  
Model Performance ◽  
Axial Stiffness ◽  
External Fixators ◽  
Type Ii ◽  
Axial Loads ◽  
Relative Stiffness ◽  
The Mean ◽  
Frame Stiffness

SummaryIn order to investigate the effects of two clamp types on type II external fixator stiffness, models using wooden dowels were constructed and mechanically tested. Kirschner-Ehmer clamps were compared to Securos clamps in four-pin type II external fixator configurations. Increasing axial loads were applied and displacement at a gap in the centre of the model measured. Linear regression and comparison of the slope of the regression lines before yield, after yield, and throughout 700N assessed model performance. The resulting load displacement curves were linear. There was no difference in model stiffness before yield, but was greater with models constructed with Securos clamps after yield and overall. The mean relative stiffness of the models constructed with the Kirschner-Ehmer type clamps were 320 ± 53.8 Newtons/mm, and with models constructed with Securos type clamps were 425 ± 74.8 Newtons/mm. Utilizing Securos clamps resulted in significantly (p<0.05) greater frame stiffness that is attributable to higher load at yield and greater stiffness after yield. Increasing resistance to rotational moments at the clamp/connecting bar junction should result in less stress imparted to the bone/pin interface, decreasing strain and decreasing pin loosening.Axial stiffness in models of bilateral external fixators using Kirschner-Ehmer type clamps versus Securos clamps were compared. The stiffness of fixators constructed with Securos clamps was greater overall and at high loads due to a more secure fixation pin/connecting bar junction. Increased fixator stiffness would result in less stress at the bone/pin interface and may contribute to less pin loosening.

The development of lampbrush chromosome-type transcription in the early diplotene oocytes of Xenopus laevis: an electron-microscope analysis

1980 ◽  
Vol 44 (1) ◽  
pp. 87-101
Author(s):  
R.S. Hill ◽  
H.C. Macgregor
Keyword(s):  
Linear Regression ◽  
Xenopus Laevis ◽  
Linear Regression Analysis ◽  
Transcription Unit ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Significant Difference ◽  
Germinal Vesicles ◽  
The Mean

Oocytes of Xenopus laevis in pachytene and early diplotene of meiosis have been studied using the Miller spreading technique. Transcription first appears in germinal vesicles 25–40 micrometers in diameter, when the oocyte is in early diplotene. Transcription at this stage consists of arrays of short RNP transcripts, irregularly distributed along the DNP axis. Linear regression analysis has shown that many of these arrays are transcription units (Type I) with the transcripts having a common point of origin. The lengths of these early transcription units (mean = 7.06 +/− 5.06 micrometers), calculated from the linear regression data, are comparable to the lengths of transcription units from later stages, including Dumont stage 3. The polymerase granules of Type I transcription units are widely and irregularly spaced, having a mean spacing of 505 +/− 748 nm. More advanced transcription units (Type II, mean length = 8.72 +/− 3.77 micrometer) are usually found in the same chromosome set as the Type I units. Type II transcription units have closer and more regularly spaced polymerase granules than Type I transcription units (mean spacing = 92 +/− 49 nm). Both Type I and II transcription units have comparatively short RNP transcripts, the mean values for the slopes of their regression lines being 0.1336 and 0.1440 respectively. By the time the germinal vesicles are about 50–60 micrometers in diameter the transcription units have a quite different morphology (Type III). The lengths of the Type III transcription units are comparable to the Type I and II units, the mean length being 6.34 +/− 4.03 micrometers. The spacing of the polymerase granules in the Type III units is closer and more regular than the earlier stages (70 +/− 40 nm). Another significant difference between Type III and Types I and II transcription units is a decrease in the foreshortening of the Type III RNP transcripts. The mean slope of the regression lines for Type III transcription units is 0.2439. The morphological appearance of the Type III transcription unit is virtually identical to that of the transcription units from Dumont stage 3 oocytes, both with respect to the length and the spacing of the polymerase granules. However, the transcripts in Type III transcription units are still more foreshortened than those of Dumont stage 3 oocytes, having mean regression slopes of 0.4728. From the data obtained in the present study, it has been concluded that the pattern of lampbrush-type transcription is virtually fully established by the time most germinal vesicles are about 50 micrometers in diameter.

scholarly journals A Novel External Fixator to Facilitate Accurate and Efficient Fracture Treatment

2021 ◽  
Author(s):  
Mingkui Shen ◽  
Zizheng Ai ◽  
Jingna Li ◽  
Huaping Liang ◽  
Xieping Dong
Keyword(s):  
External Fixator ◽  
Biomechanical Testing ◽  
Torsional Stiffness ◽  
Axial Stiffness ◽  
External Fixators ◽  
Therapeutic Effects ◽  
Fracture Treatment ◽  
Universal Joint ◽  
Efficient Treatment ◽  
Complex Fractures

Abstract Background: The rapid popularization and application of bone external fixation technology has led to external fixators emerging as remarkable methods to treat various complex fractures. Because of their instability, assembly complexity and poor controllability, however, new external fixators are challenging to design in terms of facilitating accurate and efficient fracture treatment.Methods: We designed a novel external fixator that could feasibly treat clinical complex fractures. A prospective study was conducted on patients with various complex fractures from September 2017 to September 2019. During this period, we treated 24 patients with a universal joint external fixator and then evaluated its therapeutic effects. In this study, adult cadaver femur fracture fixations were modelled by using universal joint (UJ) and AO external fixators, and the mechanical stability was assessed by applying a biomechanical testing device.Results: The designed device not only fits the repair site but could also be conveniently installed and implanted. All patients achieved good fixation and fracture healing with the universal joint fracture external fixators. In in vitro biomechanical testing, constructs were loaded under axial compression, lateral compression and torsion. Overall axial stiffness showed no significant differences between the two groups. The lateral stiffness was 1.554 ± 0.017 mm for the UJ group and 1.342 ± 0.020 mm for the AO group (p<0.001) under a 600 N load, while the torsional stiffness was 15.727 ± 0.141° for the UJ group and 14.472 ± 0.292° for the AO group under a 40 Nm load.Conclusion: In this small and preliminary study, the universal joint external fixator, which achieved a stable mechanical structure, was capable of intensive and efficient treatment for comprehensive fractures. If these findings can be confirmed in a larger study, this external fixator may be widely used in certain situations where traditional external fixators are not a convenient option.

scholarly journals Outcome of Unstable Pertrochanteric Fractures in High-Risk Geriatric Treated with External Fixators

2021 ◽  
Vol 4 (2) ◽  
Keyword(s):  
High Risk ◽  
External Fixator ◽  
Operating Time ◽  
Healing Time ◽  
Harris Hip Score ◽  
External Fixators ◽  
Pertrochanteric Fractures ◽  
Advantages And Disadvantages ◽  
The Mean ◽  
Tract Infections

Background: To review the outcome of high-risk geriatrics with unstable pertrochanteric fractures treated with external fixator. Methods: Eighteen consecutive patients with pertrochanteric fractures were operated with external fixator by using closed reduction technique. AO type, accompanying diseases, operating time, transfused blood units, duration of hospitalization, complications, healing time and mortality were recorded. Patients were followed clinically and radiologically for two years at least. The Harris Hip Score was used to document hip function at each regular follow-up. Results: Fifteen patients with average age of 71.5 years were available for final evaluation. The mean operating time was 41.1 min and union was achieved in all cases with an average time of 16 weeks. The mean Harris Hip Score at one, three, six, twelve and twenty-four months postoperatively was 42.07 ± 8.55; 55.07 ± 11.62; 70.07 ± 10.32; 86.27 ± 9.06 and 89.27 ± 8.81 respectively. Complications included all the patients undergoing loss of some motion in the knee and four of them had to experience revision surgery because of knee stiffness, ten cases of pin-tract infections, seven cases of deep venous thrombosis, two cases of migration of the screws and two cases limb shortening Conclusions: The use of external fixator in high-risk geriatric provided a satisfactory long term efficacy, but the short term functional results were quite unsatisfactory owing to high complication rate. Therefore, the advantages and disadvantages should be fully weighed when using external fixators, which was especially suitable for those patients who could not tolerate prolonged operative time and open surgery.

Influence of the connecting rod on the biomechanical properties of five external skeletal fixation configurations

2003 ◽  
Vol 16 (02) ◽  
pp. 82-87 ◽  
Author(s):  
J. D. Ross ◽  
J. P. Toombs ◽  
R. D. Welch ◽  
D. G. Bronson
Keyword(s):  
Axial Compression ◽  
External Fixator ◽  
Biomechanical Properties ◽  
Type Ii ◽  
Connecting Rod ◽  
Size Number ◽  
Frame Stiffness ◽  
Fixation System

SummaryA recently developed external skeletal fixation system (SK™, IMEX Veterinary, Inc.) utilizes larger diameter connecting rods, therefore overcoming one of the weaknesses of the original Kirschner-Ehmer (KE) system. The purpose of the current study was to compare five typical external fixator constructs in axial compression, torsion, Cranial-Caudal (C-C) and Medial-Lateral (M-L) bending to determine the effect of the larger connecting rods on frame stiffness. The results demonstrate that the larger connecting rod has a significant effect on overall frame stiffness. The use of two or more full-pins, as in the type II and III techniques nullified the contribution of the connecting rod diameter and frame stiffness was more a factor of pin size, number and orientation.

Simple and multiple fractures of the radius treated with an external fixator

2002 ◽  
Vol 15 (02) ◽  
pp. 97-103 ◽  
Author(s):  
A. L. Johnson ◽  
J. P. Toombs ◽  
D. J. Schaeffer ◽  
P. H. Laverty
Keyword(s):  
Veterinary Medicine ◽  
External Fixator ◽  
Fracture Site ◽  
Type Ii ◽  
Multiple Fracture ◽  
Multiple Fractures ◽  
Diaphyseal Fractures ◽  
The Mean ◽  
Time To Fracture ◽  
Mean Time

SummaryThe medical records of 56 dogs with diaphyseal fractures of the radius and ulna treated with Type lb or Type II external skeletal fixation were reviewed. The patients were referred to the College of Veterinary Medicine University of Illinois or the Purdue University School of Veterinary Medicine during the period from 1983 to 1999. There were thirty-two “simple” fractures and twenty-four multiple fractures. Twenty-four Type II frames and eight Type lb frames were used to treat the “simple” fractures. Twenty Type II frames and four Type lb frames were used to treat the multiple fractures. Eight of the thirty-two dogs with “simple” fractures and twelve of the twenty-four dogs with multiple fractures were admitted with open fractures. Open fractures were associated with a significantly longer time to fracture “bridging” Open reduction was used more frequently for the treatment of dogs with “simple” fractures. Open reduction resulted in greater bone contact at the fracture site. Contact at the fracture site resulted in a shorter time to removal of the external fixation. Clinical union was achieved in fifty of fifty-six fractures, with a mean time to removal of the fixation of 14.2 weeks. Significant difference, in the mean time to fracture “bridging” or the mean time to fixator removal, were not found between the “simple” and multiple fracture groups. Complications occurred in 25% (14/56) of fractures. Complications of fracture healing occurred in 18% (9/56) of fracture repairs, and fracture related complications occurred in 9%. The complications occurred more frequently in dogs weighing under 5 kg. There was not any difference between the “simple” and multiple fracture groups, with respect to the type or frequency of complications experienced. The results of this study indicate that stabilization, with an External Fixator, is an appropriate treatment for both “simple” and multiple diaphyseal fractures of the radius and ulna.

Evolution of the treatment of canine radial and tibial fractures with external fixators

2008 ◽  
Vol 21 (03) ◽  
pp. 256-261 ◽  
Author(s):  
D. Schaeffer ◽  
A. Johnson
Keyword(s):  
External Fixator ◽  
Delayed Union ◽  
Tibial Fractures ◽  
External Fixators ◽  
Type Ii ◽  
The Past ◽  
Type Ia ◽  
Frame Construction ◽  
Pin Track ◽  
Hybrid Frames

Summary Objectives: To determine if indications for external fixator treatment of radial and tibial fractures, management of the fractures, or outcomes have changed over three decades. Methods: Three groups of dogs were identified from discrete time spans within three decades and the medical records and radiographs were evaluated. The groups were compared in order to determine whether indications (signalment, etiology, fracture type and configuration), reduction method, equipment and implants, frame types and pin numbers, numbers of radiographic reevaluations, use of destabilization, frequency of pin track osteolysis, frame removal times and percentage of complications remained the same over the decades. Results: The indications for external fixator treatment of radial and tibial fractures remained consistent over three decades. The equipment and implants changed over the decades. Frame construction changed from the predominately Type II frames constructed in the 1980’s and 1990’s to a variety of modified Type II, Type Ia, Type Ib and hybrid frames constructed in the 2000’s. The frequency of pin track osteolysis decreased significantly over the decades. Frame removal times have not changed significantly over the past three decades. Complications (nonunion, delayed union, osteomyelitis, implant failure and premature frame loss) have decreased over this time. Clinical significance: Improvements in techniques and equipment have led to decreased complications with external fixators.

scholarly journals A Novel External Fixator to Facilitate Accurate and Efficient Fracture Treatment

2021 ◽  
Author(s):  
Mingkui Shen ◽  
Lulu Wang ◽  
Zizheng Ai ◽  
Jingna Li ◽  
Huaping Liang ◽  
...  
Keyword(s):  
External Fixator ◽  
Biomechanical Testing ◽  
Torsional Stiffness ◽  
Axial Stiffness ◽  
External Fixators ◽  
Therapeutic Effects ◽  
Fracture Treatment ◽  
Universal Joint ◽  
Efficient Treatment ◽  
Complex Fractures

Abstract Background: The rapid popularization and application of bone external fixation technology has led to external fixators emerging as remarkable methods to treat various complex fractures. Because of their instability, assembly complexity and poor controllability, however, new external fixators are challenging to design in terms of facilitating accurate and efficient fracture treatment.Methods: We designed a novel external fixator that could feasibly treat clinical complex fractures. A prospective study was conducted on patients with various complex fractures from September 2017 to September 2019. During this period, we treated 24 patients with a universal joint external fixator and then evaluated its therapeutic effects. In this study, adult cadaver femur fracture fixations were modelled by using universal joint (UJ) and AO external fixators, and the mechanical stability was assessed by applying a biomechanical testing device.Results: The designed device not only fits the repair site but could also be conveniently installed and implanted. All patients achieved good fixation and fracture healing with the universal joint fracture external fixators. In in vitro biomechanical testing, constructs were loaded under axial compression, lateral compression and torsion. Overall axial stiffness showed no significant differences between the two groups. The lateral stiffness was 1.554 ± 0.017 mm for the UJ group and 1.342 ± 0.020 mm for the AO group (p<0.001) under a 600 N load, while the torsional stiffness was 15.727 ± 0.141° for the UJ group and 14.472 ± 0.292° for the AO group under a 40 Nm load.Conclusion: In this small and preliminary study, the universal joint external fixator, which achieved a stable mechanical structure, was capable of intensive and efficient treatment for comprehensive fractures. If these findings can be confirmed in a larger study, this external fixator may be widely used in certain situations where traditional external fixators are not a convenient option.

scholarly journals Outcome of unstable pertrochanteric fractures in high-risk geriatric treated with external fixators

2021 ◽  
Author(s):  
Yu Liang ◽  
Shaojiang Liu ◽  
Fenglin Zhong
Keyword(s):  
High Risk ◽  
External Fixator ◽  
Close Contact ◽  
Operating Time ◽  
Healing Time ◽  
Harris Hip Score ◽  
External Fixators ◽  
Pertrochanteric Fractures ◽  
The Mean ◽  
Tract Infections

Abstract Background: To review the outcome of high-risk geriatrics with unstable pertrochanteric fractures treated with external fixator.Methods: Eighteen consecutive patients with pertrochanteric fractures were operated with external fixator by using closed reduction technique. AO type (A2.2, A2.3, A3.1, A.3.2 and A.3.3)) fractures were included in the study. Accompanying diseases, operating time, transfused blood units, duration of hospitalization, complications, healing time and mortality were recorded. Patients were followed clinically and radiologically for two years at least. The Harris Hip Score was used to document hip function at each regular follow-up.Results: Fifteen patients with average age of 71.5 years were available for final evaluation. The mean operating time was 41.1 min and union was achieved in all cases with an average time of 16 weeks. The mean Harris Hip Score at one, three, six, twelve and twenty-four month postoperatively was 42.07 ± 8.55; 55.07 ± 11.62; 70.07 ± 10.32; 86.27 ± 9.06 and 89.27 ± 8.81 respectively. Complications included fifteen of patients undergoing loss of some motion in the knee and four of them had to experience revision surgery because of knee stiffness, ten cases of pin-tract infections, seven cases of deep venous thrombosis, two cases of migration of the screws and two cases limb shorteningConclusions: It was of paramount importance that a comprehensive, multidisciplinary cooperation was consistently implemented and medical personnel provided detailed rehabilitation training plan and kept close contact with patients to make these high-risk geriatrics with unstable perotrochanteric fractures achieve satisfactory long-term effect owing to short-term functional results are quite unsatisfactory.

The global dynamics of stochastic Holling type II predator-prey models with non constant mortality rate

Filomat ◽  
2017 ◽  
Vol 31 (18) ◽  
pp. 5811-5825
Author(s):  
Xinhong Zhang
Keyword(s):  
Mortality Rate ◽  
Stochastic Model ◽  
Sufficient Conditions ◽  
Positive Periodic Solution ◽  
Global Dynamics ◽  
Type Ii ◽  
Predator Prey ◽  
Persistence In The Mean ◽  
The Mean ◽  
Predator Prey Models

In this paper we study the global dynamics of stochastic predator-prey models with non constant mortality rate and Holling type II response. Concretely, we establish sufficient conditions for the extinction and persistence in the mean of autonomous stochastic model and obtain a critical value between them. Then by constructing appropriate Lyapunov functions, we prove that there is a nontrivial positive periodic solution to the non-autonomous stochastic model. Finally, numerical examples are introduced to illustrate the results developed.

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