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 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.

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.

scholarly journals Annular Defects Impair the Mechanical Stability of the Intervertebral Disc

2021 ◽  
pp. 219256822110060
Author(s):  
Jun-Xin Chen ◽  
Yun-He Li ◽  
Jian Wen ◽  
Zhen Li ◽  
Bin-Sheng Yu ◽  
...  
Keyword(s):  
Intervertebral Disc ◽  
Degrees Of Freedom ◽  
Mechanical Stability ◽  
Biomechanical Testing ◽  
Bending Stiffness ◽  
Biomechanical Study ◽  
Torsional Stiffness ◽  
P Value ◽  
Lateral Bending ◽  
Flexion Extension

Study Design: A biomechanical study. Objectives: The purpose of this study was to investigate the effects of cruciform and square incisions of annulus fibrosus (AF) on the mechanical stability of bovine intervertebral disc (IVD) in multiple degrees of freedom. Methods: Eight bovine caudal IVD motion segments (bone-disc-bone) were obtained from the local abattoir. Cruciform and square incisions were made at the right side of the specimen’s annulus using a surgical scalpel. Biomechanical testing of three-dimensional 6 degrees of freedom was then performed on the bovine caudal motion segments using the mechanical testing and simulation (MTS) machine. Force, displacement, torque and angle were recorded synchronously by the MTS system. P value <.05 was considered statistically significant. Results: Cruciform and square incisions of the AF reduced both axial compressive and torsional stiffness of the IVD and were significantly lower than those of the intact specimens ( P < .01). Left-side axial torsional stiffness of the cruciform incision was significantly higher than a square incision ( P < .01). Neither incision methods impacted flexional-extensional stiffness or lateral-bending stiffness. Conclusions: The cruciform and square incisions of the AF obviously reduced axial compression and axial rotation, but they did not change the flexion-extension and lateral-bending stiffness of the bovine caudal IVD. This mechanical study will be meaningful for the development of new approaches to AF repair and the rehabilitation of the patients after receiving discectomy.

A Proximally-Adjustable Variable Length Intramedullary Nail: Ex Vivo Quasi-Static and Cyclic Loading Evaluation

2017 ◽  
Vol 11 (4) ◽  
Author(s):  
Mark J. Hedgeland ◽  
Alexander Martin Clark ◽  
Mario J. Ciani ◽  
Arthur J. Michalek ◽  
Laurel Kuxhaus
Keyword(s):  
Cyclic Loading ◽  
Mechanical Performance ◽  
Ex Vivo ◽  
Healing Process ◽  
Axial Loading ◽  
Torsional Stiffness ◽  
Axial Stiffness ◽  
Four Point Bending ◽  
Point Bend ◽  
Static And Cyclic Loading

An adjustable-length intramedullary (IM) nail may reduce both complications secondary to fracture fixation and manufacturing costs. We hypothesized that our novel nail would have suitable mechanical performance. To test this hypothesis, we manufactured three prototypes and evaluated them in quasi-static axial compression and torsion and quasi-static four-point bending. Prototypes were dynamically evaluated in both cyclic axial loading and four-point bending and torsion-to-failure. The prototypes exceeded expectations; they were comparable in both quasi-static axial stiffness (1.41 ± 0.37 N/m in cervine tibiae and 2.30 ± 0.63 in cadaver tibiae) and torsional stiffness (1.05 ± 0.26 N·m/deg in cervine tibiae) to currently used nails. The quasi-static four-point bending stiffness was 80.11 ± 09.360, greater than reported for currently used nails. A length-variance analysis indicates that moderate changes in length do not unacceptably alter bone-implant axial stiffness. After 103,000 cycles of axial loading, the prototype failed at the locking screws, comparable to locking screw failures seen clinically. The prototypes survived 1,000,000 cycles of four-point bend cyclic loading, as indicated by a consistent phase angle throughout cyclic loading. The torsion-to-failure test suggests that the prototype has adequate resistance to applied torques that might occur during the healing process. Together, these results suggest that our novel IM nail performs sufficiently well to merit further development. If brought to market, this adjustable-length IM nail could reduce both patient complications and healthcare costs.

scholarly journals A COMPARATIVE STUDY OF IN VIVO EFFECT OF PERCUTANEOUS BONE MARROW INJECTION VS WITHOUT INJECTION ON UNION OF OPEN TIBIAL SHAFT FRACTURES WITH EXTERNAL FIXATOR

2020 ◽  
pp. 1-2
Author(s):  
Hrishikesh Desai ◽  
Kirtiraj G ◽  
Abhay P
Keyword(s):  
Bone Marrow ◽  
External Fixator ◽  
Autologous Bone Marrow ◽  
Tibial Fractures ◽  
External Fixators ◽  
Open Tibial Fractures ◽  
Autologous Bone ◽  
Group 2 ◽  
Radiological Union

Background : Open tibial fractures are notorious fractures because the open wound leaves us with limited options and means multiple operations with long intervals for the patient. The usual method of treatment of contaminated, late presenting and complicated fractures is a temporary external fixator followed by conversion into a costly definitive procedure once the wound has healed. The secondary definitive procedure also means extra cost in an already economically stressed patient.In our set up we have to often let patients leave with a plaster cast after removing the external fixator for economic constrains. Per cetaceous autologous bone marrow injection while the patient is on external fixator is one alternative that we have tried to deal with this problem hoping for a primary union without any costly intervention. Materials and methods : We had 42 cases of open tibial fractures which were treated with external fixator and per cutaneous bone marrow injection while 38 other cases which were used as control with only the external fixator and no injections. We included open fractures of only Gustilo Anderson type II,IIIA and B for our study. Study was conducted between period of June 2012 and December 2013 at SBKS medical college . Results : In group one, 34 of the 42 patients had a radiological union before 12 weeks while another 2 in 16 weeks. For group 2 , only 16 of the 38patients had radiological union at 12 weeks and no more at 16 weeks. The average time of union for group 1 was 10 weeks while of group 2 was 12 weeks .Function of the union cases of both the groups was similar in all aspects including distance of walking and ability to carry out daily activities. Conclusion : Per cutaneous autologous bone marrow injections are cheap , easily available and successful alternative to a secondary procedure for open tibial fractures on external fixators.

Methyl methacrylate in external fixation of supracondylar humerus fractures: An experimental study

2018 ◽  
Vol 232 (10) ◽  
pp. 1025-1029
Author(s):  
Ali Güleç ◽  
Mehmet Ali Acar ◽  
Bahattin Kerem Aydin ◽  
Teyfik Demir ◽  
Mustafa Özkaya
Keyword(s):  
Methyl Methacrylate ◽  
External Fixation ◽  
External Fixator ◽  
External Fixators ◽  
Three Point Bending ◽  
Fixation Methods ◽  
Supracondylar Humerus Fractures ◽  
Methacrylate Group ◽  
Humerus Fractures ◽  
K Wires

Supracondylar humerus fractures are common fractures around the elbow. Open fractures, comminuted metaphyseal fractures and also fractures with bone loss may need to be treated with external fixators. The aim of this study is to compare two different external fixators, tubular external fixators and polymethyl methacrylate with K wires external fixators, with regard to stiffness and stability for metaphyseal-diaphyseal osteotomies of distal humerus close to the joint. Six matched pairs (24 specimens) of second-generation sawbone humerus were prepared in a standard fashion to create a metaphyseal fracture, 5 cm proximal to the distal joint line of humerus and were randomly divided into two groups of 12 specimens each. Each sawbone humerus was osteotomized transversely at the mid-olecranon fossa with a 2-mm oscillating saw to simulate a Gartland type III fracture. The osteotomy was then reduced and stabilized using two different external fixation methods: carbon tubular external fixator with Schanz screws and methyl methacrylate with multiple K wires. Three-point bending and torsion tests were performed on the specimens. Bending and torsional stiffness of specimens were obtained for the fixation methods. According to the results of the study, the methyl methacrylate group has provided higher stiffness than classical tubular fixator with Schanz screws in three-point bending test (7.79 ± 2.33 N/mm vs 3.78 ± 1.18 N/mm, p = 0.006). The methyl methacrylate group also showed better stiffness in torsion test (0.12 ± 0.042 N m/° vs 0.067 ± 0.013 N m/°, p = 0.02). We determined for the first time in literature that external fixation with methyl methacrylate was significantly superior to the classical tubular external fixator with Schanz screws with regard to stiffness and stability under three-point bending and torsional loads. Moreover, methyl methacrylate is inexpensive and easily applied.

The effect of contouring the connecting bar in an acrylic-pin external fixator

2001 ◽  
Vol 14 (04) ◽  
pp. 190-195 ◽  
Author(s):  
E. L. Egger ◽  
G. D. Herndon
Keyword(s):  
Ultimate Strength ◽  
Axial Compression ◽  
External Fixator ◽  
Testing Machine ◽  
Biomechanical Testing ◽  
Catastrophic Failure ◽  
High Stiffness

This studies the effects of contouring of acrylic column when placed in axial compression. Six different angles were studied, 0°, 30°, 45°, 60°, 90° and a 90° with a 2.0 mm connecting bar. Each column was then placed under axial compression using a biomechanical testing machine. As the angle of the contour increased there was a significant decrease in the ultimate stiffness and ultimate strength of the columns. However, the amount of force required to cause catastrophic failure in any of the group was still high (stiffness 300 N/mm ± 70, ultimate strength 1032 N ± 139) which may not be reached in a physiological setting. When using a severe angulation of the column the using of a connecting bar will significantly increase both stiffness and strength of the acrylic.

scholarly journals Biomechanical comparison of medial sustainable nail and proximal femoral nail antirotation in the treatment of an unstable intertrochanteric fracture

2020 ◽  
Vol 9 (12) ◽  
pp. 840-847
Author(s):  
Shaobo Nie ◽  
Ming Li ◽  
Hui Ji ◽  
Zhirui Li ◽  
Wenwen Li ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Torsional Stiffness ◽  
Proximal Femoral Nail ◽  
Axial Stiffness ◽  
Intertrochanteric Fractures ◽  
Loading Test ◽  
Cyclic Loading Test ◽  
Femoral Nail ◽  
Unstable Intertrochanteric Fracture ◽  
The Mean

Aims Restoration of proximal medial femoral support is the keystone in the treatment of intertrochanteric fractures. None of the available implants are effective in constructing the medial femoral support. Medial sustainable nail (MSN-II) is a novel cephalomedullary nail designed for this. In this study, biomechanical difference between MSN-II and proximal femoral nail anti-rotation (PFNA-II) was compared to determine whether or not MSN-II can effectively reconstruct the medial femoral support. Methods A total of 36 synthetic femur models with simulated intertrochanteric fractures without medial support (AO/OTA 31-A2.3) were assigned to two groups with 18 specimens each for stabilization with MSN-II or PFNA-II. Each group was further divided into three subgroups of six specimens according to different experimental conditions respectively as follows: axial loading test; static torsional test; and cyclic loading test. Results The mean axial stiffness, vertical displacement, and maximum failure load of MSN-II were 258.47 N/mm (SD 42.27), 2.99 mm (SD 0.56), and 4,886 N (SD 525.31), respectively, while those of PFNA-II were 170.28 N/mm (SD 64.63), 4.86 mm (SD 1.66), and 3,870.87 N (SD 552.21), respectively. The mean torsional stiffness and failure torque of MSN-II were 1.72 N m/° (SD 0.61) and 16.54 N m (SD 7.06), respectively, while those of PFNA-II were 0.61 N m/° (SD 0.39) and 6.6 N m (SD 6.65), respectively. The displacement of MSN-II in each cycle point was less than that of PFNA-II in cyclic loading test. Significantly higher stiffness and less displacement were detected in the MSN-II group (p < 0.05). Conclusion The biomechanical performance of MSN-II was better than that of PFNA-II, suggesting that MSN-II may provide more effective mechanical support in the treatment of unstable intertrochanteric fractures. Cite this article: Bone Joint Res 2020;9(12):840–847.

scholarly journals A Wear Simulation Method for Mechanical Face Seals under Friction Instability Conditions

2020 ◽  
Vol 10 (8) ◽  
pp. 2875
Author(s):  
Wentao He ◽  
Shaoping Wang ◽  
Chao Zhang ◽  
Xi Wang ◽  
Di Liu
Keyword(s):  
Contact Pressure ◽  
Torsional Stiffness ◽  
Frictional Heat ◽  
Axial Stiffness ◽  
Asperity Contact ◽  
Wear Simulation ◽  
Time Rate ◽  
Wear Time ◽  
Face Seals ◽  
Non Gaussian

Mechanical face seals are crucial components of automotive cooling water pumps and affect the safe operation of the pump. This article focuses on the effect of friction instabilities on the wear of the seals. Friction instabilities, such as stick-slip, occur when the axle is decelerated or operated at a low speed. Based on previous studies, a simulation model is proposed of a mechanical face seal that considers the interaction of asperities of non-Gaussian surfaces and the heat transfer between the sealing rings. According to the Archard wear equation, a numerical wear simulation is performed, and the wear distance rate and wear time rate are obtained. A comparison of the contact pressure of the Gaussian and non-Gaussian surfaces indicates that the latter is more likely to generate high contact pressure, thereby producing more significant wear. The viscous shear heat and frictional heat due to asperity contact decrease with an increase in the thickness of the tapered film. As the shaft decelerates, the wear distance rate increases with an increase in the axial stiffness. The axial damping only affects the duration of the oscillations. The wear time rate decreases with an increase in the torsional stiffness and torsional damping. The results of this research provide guidelines for estimating the wear of mechanical seals when friction instabilities occur.

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