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1.
J Prosthet Dent ; 2020 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-33349465

RESUMO

STATEMENT OF PROBLEM: The press-fit (Morse taper) implant system is commonly used to restore edentulous areas. However, abutment screws in this system may be damaged because of the 2- or 3-piece design, consequently causing complications. How these damaging situations occur is unclear. PURPOSE: The purpose of this in vitro and finite element analysis (FEA) study was to elucidate the mechanisms of the press-fit implant system underlying abutment screw damage. MATERIAL AND METHODS: The ANKYLOS implant system was used as a simulation model and for experimental test specimens. The experimental test was performed by using a material test system, and the obtained data were used to validate the FEA outcome. In the FEA simulation, the bilinear material property and nonlinear contact conditions were applied to simulate the process of tightening the abutment screw between the abutment and implant. A force of 300 N was then applied to the abutment to investigate the stress distribution and deformation of the implant system. RESULTS: In the experimental test, the fracture site of all specimens was observed at the abutment-screw thread. All implants and abutments exhibited permanent bending deformation. The results of the FEA simulation generally concurred with the experimental outcomes. CONCLUSIONS: The abutment torque used to generate the press-fit contact interface between the abutment and implant induced stresses within the implant components, substantially increasing the failure probability of the conical implant system during function.

2.
BMC Musculoskelet Disord ; 21(1): 752, 2020 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-33189156

RESUMO

BACKGROUND: Two parallel cannulated screws along with an anterior wire to construct a tension band is a popular approach in transverse patellar fractures. However, the optimal screw proximity, either deep or superficial screw placements, remains controversial. Hence, a new concept of the addition of a third screw to form a triangular configuration along with the original two parallel screws was proposed in this study. Therefore, the biomechanical effect of the additional third screw on the stability of the fractured patella was investigated with finite element (FE) simulation. METHODS: An FE knee model including the distal femur, proximal tibia, and fractured patella (type AT/OTA 34-C) was developed in this study. Four different screw configurations, including two parallel cannulated screws with superficial (5-mm proximity) and deep (10-mm proximity) placements and two parallel superficial screws plus a third deep screw, and two parallel deep screws plus a third superficial screw, with or without the anterior wire, were considered for the simulation. RESULTS: Results indicated that the addition of a third screw increased stability by reducing the dorsal gap opening when two parallel screws were deeply placed, particularly on the fractured patella without an anterior wire. However, the third screw was of little value when two parallel screws were superficially placed. In the existence of two deep parallel screws and the anterior wire, the third screw reduced the gap opening by 23.5% (from 1.15 mm to 0.88 mm) and 53.6% (from 1.21 mm to 0.61 mm) in knee flexion 45° and full extension, respectively. Furthermore, in the absence of the anterior wire, the third screw reduced the gap opening by 73.5% (from 2 mm to 0.53 mm) and 72.2% (from 1.33 mm to 0.37 mm) in knee flexion 45° and full extension, respectively. CONCLUSION: Based on the results, a third cannulated screw superficially placed (5-mm proximity) is recommended to increase stability and maintain contact of the fractured patella, fixed with two parallel cannulated screws deeply placed (10-mm proximity), particularly when an anterior wire was not used. Furthermore, the third screw deeply placed is not recommended in a fractured patella with two parallel superficial screws.

3.
J Orthop Surg Res ; 15(1): 409, 2020 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-32928260

RESUMO

BACKGROUND: Lateral hinge fracture (LHF) is associated with nonunion and plate breakage in high tibial osteotomy (HTO). Mechanical studies investigating fixation strategies for LHFs to restore stability and avoid plate breakage are absent. This study used computer simulation to compare mechanical stabilities in HTO for different LHFs fixed with medial and bilateral locking plates. METHODS: A finite element knee model was created with HTO and three types of LHF, namely T1, T2, and T3 fractures, based on the Takeuchi classification. Either medial plating or bilateral plating was used to fix the HTO with LHFs. Furthermore, the significance of the locking screw at the combi hole (D-hole) of the medial TomoFix plate was evaluated. RESULTS: The osteotomy gap shortening distance increased from 0.53 to 0.76, 0.79, and 0.72 mm after T1, T2, and T3 LHFs, respectively, with medial plating only. Bilateral plating could efficiently restore stability and maintain the osteotomy gap. Furthermore, using the D-hole screw reduced the peak stress on the medial plate by 28.7% (from 495 to 353 MPa), 26.6% (from 470 to 345 MPa), and 32.6% (from 454 to 306 MPa) in T1, T2, and T3 LHFs, respectively. CONCLUSION: Bilateral plating is a recommended strategy to restore HTO stability in LHFs. Furthermore, using a D-hole locking screw is strongly recommended to reduce the stress on the medial plate for lowering plate breakage risk.

4.
Artigo em Inglês | MEDLINE | ID: mdl-31834586

RESUMO

Posterior lumbar interbody fusion (PLIF) with a spacer and posterior instrument (PI) via minimally invasive surgery (MIS) restores intervertebral height in degenerated disks. To align with MIS, the spacer has to be shaped with a slim geometry. However, the thin spacer increases the subsidence and migration after PLIF. This study aimed to propose a new lumbar fusion approach using bone cement to achieve a larger supporting area than that achieved by the currently used poly aryl-ether-ether-ketone (PEEK) spacer and assess the feasibility of this approach using a sawbone model. Furthermore, the mechanical responses, including the range of motion (ROM) and bone stress with the bone cement spacer were compared to those noted with the PEEK spacer by finite element (FE) simulation. An FE lumbar L3-L4 model with PEEK and bone cement spacers and PI was developed. Four fixing conditions were considered: intact lumbar L3-L4 segment, lumbar L3-L4 segment with PI, PEEK spacer plus PI, and bone cement spacer plus PI. Four kinds of 10-NM moments (flexion, extension, lateral bending, and rotation) and two different bone qualities (normal and osteoporotic) were considered. The bone cement spacer yielded smaller ROMs in extension and rotation than the PEEK spacer, while the ROMs of the bone cement spacer in flexion and lateral bending were slightly greater than with the PEEK spacer. Compared with the PEEK spacer, peak contact pressure on the superior surface of L4 with the bone cement spacer in rotation decreased by 74% (from 8.68 to 2.25 MPa) and 69.1% (from 9.1 to 2.82 MPa), respectively, in the normal and osteoporotic bone. Use of bone cement as a spacer with PI is a potential approach to decrease the bone stress in lumbar fusion and warrants further research.

5.
Zootaxa ; 4674(5): zootaxa.4674.5.1, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31715983

RESUMO

Prof. Pietro Omodeo (University of Siena, Italy), the world-renowned earthworm taxonomist and evolutionary biologist, was born in Cefalù, Sicily, Italy on the 27th September, 1919. He celebrates his 100th birthday in 2019 and members of the international community of earthworm taxonomists salute him with Petroscolex centenarius gen. et sp. nov., a new megadrile taxon discovered in 1991 by him but which has not been formally described until now. The many important contributions of Omodeo to oligochaetological research are briefly mentioned.


Assuntos
Oligoquetos , Animais , Evolução Biológica , Masculino , Sicília
6.
Zootaxa ; 4658(1): zootaxa.4658.1.4, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31716758

RESUMO

This study describes two new species of earthworms belonging to the genus Amynthas (Oligochaeta: Megascolecidae) from central Taiwan. They are named Amynthas luridus sp. nov. and Amynthas ruiyenensis sp. nov. Both species are octothecal with the former found at elevations of 1500-2300 m and the latter at an elevation of 2200 m from the Central Mountain Range. In addition, DNA barcodes are made available for the first time for the following species: Amynthas catenus Tsai et al., 2001, Amynthas exiguus aquilonius Tsai et al., 2001, Amynthas proasacceus Tsai et al., 2001, Amynthas hohuanmontis Tsai et al., 2002, Amynthas tessellatus Shen et al., 2002, Amynthas fenestrus Shen et al., 2003, Amynthas tantulus Shen et al., 2003, and Amynthas uvaglandularis Shen et al., 2003. Furthermore, Amynthas exiguus ssp. aquilonius Tsai et al., 2001 distributed at elevations of 2200-3000 m in the Central Mountain Range is elevated to species level, as A. aquilonius Tsai et al., 2001. The highest altitude record so far for the exotic Eukerria saltensis (Beddard, 1895) in Taiwan, 2200 m above sea level, is documented. Moreover, some recent assignments of species to Amynthas and Metaphire and synonymies of names are critically discussed. It is argued that idiosyncratic genus concepts, inadequate species comparisons, and unexplained synonymies should be avoided. A hitherto undetected and possibly monophyletic species group of mainly Korean Amynthas species in the A. tokioensis-group is indicated, characterized by numerous genital papillae around each spermathecal pore and male porophore, large ampullae, long diverticula, large prostate glands, and manicate intestinal caeca. The names A. bimaculata, A. silvatica and A. surcata (Ishizuka, 1999), as well as A. odaesanensis, A. righii, A. fasciiformis, and A. sanchongensis Hong James, 2001, previously declared as junior synonyms of A. tappensis (Ohfuchi, 1935), are revalidated.


Assuntos
Asteraceae , Oligoquetos , Animais , DNA , Masculino , Taiwan
7.
J Orthop Surg (Hong Kong) ; 27(3): 2309499019861145, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31311422

RESUMO

PURPOSE: Tibial tubercle osteotomy (TTO) is a surgical technique used in the management of severe fractures of the knee joint and revision total knee arthroplasty. Limited research discusses the performance of the osteotomy and fixation of the TTO with screws. Therefore, this study investigated the effects of fragment shape and screw configuration on the mechanical behavior in the fixation of the TTO using the finite element (FE) method. METHODS: FE TTO models with three fragment shapes and three screw configurations were developed. The three fragment shapes were a step cut, bevel cut, and straight cut. The screw configurations were two parallel horizontal and downward screws and two trapezoidal screws. A 1654-N upward tension force was applied on the tibia tubercle, and the distal end of the tibia was completely fixed. RESULTS: The results indicated that the step cut resulted in higher stability than the bevel and straight cut, but the stress was higher as well. Among the screw configurations, two parallel downward screws resulted in the highest stability, given the same fragment shape. In the horizontal configuration, the step cut tibia developed the largest contact force to achieve stability of the bone fragment under loading. CONCLUSION: The fragment shape with a step cut and fixation with two parallel horizontal or downward screws are suggested for TTO, while the trapezoidal screw configuration is not suggested. Furthermore, the downward screw configuration is a suitable strategy to reduce bone stress.


Assuntos
Parafusos Ósseos , Análise de Elementos Finitos , Fixação Interna de Fraturas/métodos , Osteotomia/métodos , Tíbia/cirurgia , Fraturas da Tíbia/cirurgia , Fenômenos Biomecânicos , Humanos , Fenômenos Mecânicos , Tíbia/diagnóstico por imagem , Tíbia/fisiopatologia , Fraturas da Tíbia/diagnóstico , Fraturas da Tíbia/fisiopatologia , Tomografia Computadorizada por Raios X
8.
Med Eng Phys ; 68: 57-64, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30975631

RESUMO

Tibial tubercle osteotomy (TTO) is commonly performed in cases of complicated juxta-articular trauma or revision total knee arthroplasty. However, strategies for firmly fixing the resulting osteotomy bone fragment are not sufficiently understood. This study aims to investigate the effect of the location of the gap between the fragment and the tibia and with various fixed screw configurations on TTO stability, contact force on the fragment, and bone stress by using the finite element method. A TTO model with a 1-mm gap, either above or below the fragment, was developed. Furthermore, five screw configurations, including two parallel horizontal screws placed at 20- and 30-mm intervals, two parallel downward screws, two trapezoid screws, and two divergent screws, were used. A vertically upward 1600-N force was applied on the tibial tubercle to mimic a worst-case condition. Placing the fragment close to the superior cutting plane (above the gap) yielded greater stability and less stress on the bone than did placing it close to the inferior cutting plane. The superior cutting plane of the tibia generated the largest contact force on the superior plane of the fragment for static balance under loading. Additionally, among all screw configurations, the configuration involving two parallel downward screws resulted in the highest stability but also the greatest stress on the cortical bone. The fragment obtains a solid barrier and support from the tibia immediately after surgery to against the patellar tension force when the fragment is close to the superior cutting plane of the tibia.


Assuntos
Análise de Elementos Finitos , Osteotomia/métodos , Tíbia/cirurgia , Parafusos Ósseos , Fenômenos Mecânicos , Osteotomia/instrumentação
9.
J Prosthet Dent ; 122(4): 376-382, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30948302

RESUMO

STATEMENT OF PROBLEM: A unidiameter abutment attached to a large-diameter implant has been reported to result in an unexpectedly high failure rate, inconsistent with the general understanding of dental implant mechanics. PURPOSE: The purpose of this finite element analysis study was to investigate the mechanical mechanism underlying these unexpected failures with the hypothesis that the cold welding or interference fit interface between abutment and implant increases the failure probability of a large-diameter implant system with a unidiameter abutment. MATERIAL AND METHODS: A conical implant system with different abutment gingival heights and implant diameters was analyzed for 3 contact conditions of the abutment-implant interface (bond and frictional coefficients of 0.3 and 0.7). A computer model was created using computed tomography images, and an oblique load of 100 N was applied to the abutment to determine the mechanical effect of the implant diameter and gingival height under the 3 contact conditions. RESULTS: When the abutment-implant interface was bonded, the peak stress of the abutment increased and that of the bone decreased with increasing implant diameter. When friction was applied to the abutment-implant interface, the peak stress of the implant, screw, and bone decreased with increasing implant diameter. Furthermore, the peak stress of the implant system and bone increased when the abutment gingival height increased under all contact conditions. CONCLUSIONS: Cold wielding or interference fit at the abutment-implant interface can prevent a screw fracture; however, it puts high stress on the unidiameter abutment neck when the implant diameter is increased. Screw loosening may lead to a slide between the abutment and implant, considerably increasing the stress of the screw. A system with a narrow diameter implant may cause an implant fracture rather than an abutment fracture when friction is applied to the abutment-implant interface.


Assuntos
Implantes Dentários , Fenômenos Biomecânicos , Dente Suporte , Projeto do Implante Dentário-Pivô , Análise do Estresse Dentário , Análise de Elementos Finitos , Estresse Mecânico
10.
Biomed Eng Online ; 18(1): 49, 2019 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-31018860

RESUMO

BACKGROUND: Although use of a dynamic hip screw (DHS) for stable intertrochanteric hip fracture fixation has been successfully applied in fracture healing for more than 20 years, DHS fixation on unstable intertrochanteric fractures still has a high failure rate, especially in patients with osteoporosis. Although the wire fixation is usually incorporated with orthopedic device to treat fracture, the wiring techniques are developed through experiences. Thus, this study is objective to investigate the biomechanical property of different wire fixation methods incorporated with DHS system to provide the lesser trochanter fragment stable fixation on osteoporotic TypeA2.1 fracture for enhancing stability after bone reduction. RESULTS: Sawbone testing results demonstrated higher maximum load, stiffness, and energy in a DHS with wire fixation compared with DHS fixation only. In static biomechanical testing of a cadaver femur, we compared the stiffness of five fixation models and then tested a fatigue failure model in cycle loading with DHS fixation only. Wiring fixation can enhance stability and the cut-out failure model in the fatigue test was identical to the clinical failure model. CONCLUSIONS: Lesser trochanteric fragment fixation is a crucial concern in the stability of an A2.1 unstable fracture, and the combination of a wiring technique with a DHS seems beneficial for achieving better stability. The addition of an antirotational greater trochanter is likely to enhance stability through wiring of the greater trochanter.


Assuntos
Parafusos Ósseos , Fraturas do Quadril/cirurgia , Fenômenos Mecânicos , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Feminino , Fêmur/cirurgia , Humanos , Teste de Materiais
11.
BMC Musculoskelet Disord ; 20(1): 99, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30832645

RESUMO

BACKGROUND: Cannulated screws with an anterior wire are currently used for managing transverse patellar fracture. However, the addition of anterior wiring with various types of screws via open surgery to increase the mechanical stability is yet to be determined. Hence, this study aimed to compare the mechanical behaviors of a fractured patella fixed with various screws types and at various screw locations with and without the anterior wire. The present study hypothesized that using the anterior wire reduces the fracture gap formation. METHODS: A finite element (FE) model containing a fractured patella fixed with various types of cannulated screws and anterior wiring was created in this study. Three types of screws, namely partial thread, full thread, and headless compression screws, and two screw depths, namely 5 and 10 mm away from the anterior surface of the patella, were included. The effect of the anterior wire was clarified by comparing the results of surgical fixation with and without the wire. Two magnitudes and two loading directions were used to simulate and examine the mechanical responses of the fractured patella with various fixation conditions during knee flexion/extension. RESULTS: Compared with partial thread and headless compression screws, the full thread screw increased the stability of the fractured patella by reducing fragment displacement, fracture gap formation, and contact pressure while increasing the contact area at the fracture site. Under 400-N in the direction 45°, the full thread screw with 5-mm placement reduced the gap formation by 86.7% (from 2.71 to 0.36 mm) and 55.6% (from 0. 81 to 0. 36 mm) compared with the partial thread screw with 10-mm placement, respectively without and with the anterior wire. CONCLUSION: The anterior wire along with the full thread screw is preferentially recommended for maintaining the surgical fixation of the fractured patella. Without the use of anterior wiring, the full thread screw with 5-mm placement may be considered as a less invasive alternative; however, simple screw fixation at a deeper placement (10 mm) is least recommended for the fixation of transverse patellar fracture.


Assuntos
Parafusos Ósseos , Fios Ortopédicos , Análise de Elementos Finitos , Fixação Interna de Fraturas/instrumentação , Fraturas Ósseas/cirurgia , Patela/cirurgia , Fixação Interna de Fraturas/métodos , Fraturas Ósseas/diagnóstico por imagem , Humanos , Imageamento Tridimensional/métodos , Teste de Materiais/instrumentação , Teste de Materiais/métodos , Patela/diagnóstico por imagem , Patela/lesões , Suporte de Carga/fisiologia
12.
J Orthop Surg Res ; 14(1): 35, 2019 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-30691494

RESUMO

BACKGROUND: To maintain the corrected alignment after high tibial osteotomy (HTO), fixation with titanium locking plate and screws is widely used in current practice; however, screw breakage is a common complication. Thus, this study was to investigate the mechanical stability of HTO with locking plate and various screw fixations, including the length as well as the type. METHODS: A finite element (FE) model involving a distal femur, meniscus, and a proximal tibia with HTO fixed with a titanium locking plate and screws was created. The angle of the medial open wedge was 12°, and bone graft was not used. Two types of screws, namely conventional locking and far-cortical locking screws, with various lengths and configurations were used. At the proximal tibia, conventional locking screws with different lengths, 30 and 55 mm, were used; at the tibia shaft, different screw fixations including one-cortical, two-cortical, and far-cortical locking screws were used. RESULTS: The use of far-cortical locking screw generated the highest equivalent stress on the screws, which was four times (from 137.3 to 541 MPa) higher than that of the one-cortical screw. Also, it led to the maximum deformation of the tibia and a greater gap deformation at the osteotomy site, which was twice (from 0.222 to 0.442 mm) larger than that of the one-cortical screw. The effect of different locking screw length on tibia deformation and implant stress was minor. CONCLUSION: Thus, far-cortical locking screws and plates increase interfragmentary movement but the screw stress is relatively high. Increasing the protection time (partial weight duration) is suggested to decrease the risk of screw breakage in HTO through fixation with titanium far-cortical locking screws and plates.


Assuntos
Modelos Biológicos , Osteotomia/instrumentação , Tíbia/cirurgia , Fenômenos Biomecânicos , Placas Ósseas , Parafusos Ósseos , Análise de Elementos Finitos , Humanos , Osteoartrite do Joelho/cirurgia , Estresse Mecânico , Tíbia/fisiologia , Titânio
13.
Injury ; 50(2): 263-271, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30554895

RESUMO

INTRODUCTION: To date, the effects of various screw configurations on the stability of tibial tubercle osteotomy (TTO) are not completely understood. Hence, the first aim of this study is to evaluate the stability of TTO under various screw configurations. The second aim is to evaluate the internal stresses in the bone and the contact forces on the bone fragment that are developed by the tibia and screws in response to the applied load after the equilibrant is revealed. METHODS: To calculate the biomechanical responses of the bone and screw under loading, finite element (FE) method was used in this study. Six types of screw configurations were studied in the simulation: two parallel horizontal screws placed at a 20 mm interval, two parallel horizontal screws placed at a 30 mm interval, two parallel upward screws, two parallel downward screws, two trapezoid screws, and two divergent screws. The displacement of the bone fragment, contact forces on the fragment, and the internal stress in the bone were used as indices for comparison. RESULTS: Among all configurations, the configuration of two parallel downward screws yielded the highest stability with the lowest fragment displacement and gap opening. Although the maximum displacement of the TTO with the configuration of two parallel horizontal screws was slightly higher than that of the downward configuration, the difference was only 0.2 mm. The configuration of two upward screws resulted in the highest fragment displacement and gap deformation between the fragment and tibia. The stress of the osteotomized bone fragment was highest with the configuration of two upward screws. CONCLUSION: Based on the present model, the current configuration of two parallel horizontal screws is recommended for TTO. If this is inappropriate in a specific clinical scenario, then the downward screw configuration may be used as an alternative. By contrast, the configuration of two parallel upward screws is least suggested for the fixation of TTO.


Assuntos
Fixação Interna de Fraturas/métodos , Teste de Materiais/métodos , Osteotomia/métodos , Tíbia/cirurgia , Fenômenos Biomecânicos , Placas Ósseas , Parafusos Ósseos , Análise de Elementos Finitos , Humanos , Estresse Mecânico , Tíbia/anatomia & histologia
14.
Materials (Basel) ; 11(11)2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30388864

RESUMO

Elastic nails made of the nickel-titanium shape memory alloy (Nitinol) have been reported to control bone modeling in animal studies. However, the mechanical stability of the Nitinol nail in the fixation of long bone fractures remains unclear. This study compared mechanical stability among nails made of three materials, namely Nitinol, titanium, and stainless steel, in the fixation of long bone fractures. These three materials had identical shapes (arc length: π/2 and radius: 260 mm). A cylindrical sawbone with a 10-mm gap and fixed with two C-shaped elastic nails was used to examine the stability of the nails. A finite element (FE) model was developed based on the sawbone model. The end cap for elastic nails was not used in the sawbone test but was considered based on a constraint equation in FE simulation. The results of stability tests appeared to depend on the presence or absence of the end cap. In the sawbone test, the titanium nail yielded a higher ultimate force against the applied load than did the stainless steel and Nitinol nails before the gap completely closed; the difference in linear stiffness between the nails was nonsignificant. In FE simulation, the titanium nail produced smaller gap shortening than did stainless steel and Nitinol nails without the end cap; the difference in gap shortening between the nails was minor with the end cap. The titanium elastic nail should be a better choice in managing diaphyseal long bone fractures when the end cap is not used. For Nitinol and stainless steel nails, the end cap should be used to stop the nail from dropping out and to stabilize the fractured bone.

15.
Zootaxa ; 4496(1): 302-312, 2018 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-30313705

RESUMO

This study describes two new species of earthworms belonging to the genus Drawida (Oligochaeta: Moniligastridae) from southwestern Taiwan. They are Drawida alishanensis sp. nov. and Drawida fenqihuensis sp. nov. The two species were found at elevations of 1407-1661 m in the Alishan area, Chiayi County. DNA barcodes from type specimens of the new species are reported. This is the first time that new species of Drawida are discovered from the island of Taiwan. In addition, Drawida keikiensis Kobayashi, 1938 from Korea is found to be synonymous with Drawida syringa Chen, 1933 from central China. The synonymy of Drawida glabella Chen, 1938 with Drawida barwelli (Beddard, 1886) is rejected.


Assuntos
Oligoquetos , Animais , China , República da Coreia , Taiwan
16.
J Orthop Surg (Hong Kong) ; 26(3): 2309499018789705, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30037293

RESUMO

PURPOSE: Clinical and biomechanical studies have reported that using supportive screws and a wire instead of the common Kirschner wires for modified tension band wiring improves the stability of fractured patellae. However, the effect of screw proximity on the fixation of a fractured patella remains unclear. Therefore a numerical study was conducted to examine the effects of screw proximity on biomechanical responses in a simulated patellar fracture fixed using two parallel cannulated screws and anterior tension band wiring. METHODS: A patellar model with a transverse fracture and loads simulating patellar tendon forces applied on the patella were used in the present simulation. The surgical fixation consisted of two 4.0-mm parallel partially threaded cannulated screws with a figure-of-eight tension band made using a 1.25-mm stainless steel wire. Biomechanical responses at two screw proximities, 5 and 10 mm from the leading edge of the patella, were investigated. RESULTS: Superficial screw placement (5 mm) yielded higher stability, lower wire loads, and lower bone contact pressures than the deep placement (10 mm). The deep placement of screws exerted a higher load on the wire but a lower force on the screw than superficial placement did. CONCLUSION: This is the first numerical study to examine the effects of screw location on the fixation of a fractured patella using cannulated screws and tension band wiring. Considering the favorable biomechanical responses, superficial placement (5 mm below the leading edge of the patella) is recommended for screw insertion when treating a transverse fractured patella.


Assuntos
Parafusos Ósseos , Fios Ortopédicos , Fixação Interna de Fraturas/instrumentação , Fraturas Ósseas/cirurgia , Patela/lesões , Análise de Elementos Finitos , Humanos , Ligamento Patelar , Amplitude de Movimento Articular , Suporte de Carga
17.
Oecologia ; 188(1): 237-250, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29948315

RESUMO

In temperate deciduous forests of eastern USA, most earthworm communities are dominated by invasive species. Their structure and functional group composition have critical impacts on ecological properties and processes. However, the factors determining their community structure are still poorly understood, and little is known regarding their dynamics during forest succession and the mechanisms leading to these changes. Earthworm communities are usually assumed to be stable and driven by vegetation. In contrast, the importance of dispersal and ecological drift is seldom acknowledged. By analyzing a 19-year dataset collected from forest stands in eastern USA, we demonstrated that on a decadal timescale, earthworm community dynamics are shaped by the interplay of selection, dispersal, and ecological drift. We highlighted that forests at different successional stages have distinct earthworm species and functional groups as a result of environmental filtering through leaf litter quality. Specifically, young forests are characterized by soil-feeding species that rely on relatively fresh soil organic matter derived from fast-decomposing litter, whereas old forests are characterized by those feeding on highly processed soil organic matter derived from slow-decomposing litter. In addition, year-to-year species gains and losses are primarily driven by dispersal from regional to local species pools, and by local extinction resulted from competition and ecological drift. We concluded that with continued dispersal of European species and the recent "second wave" of earthworm invasion by Asian species from the surrounding landscape, earthworms at the investigated forests are well-established, and will remain as the major drivers of soil development for the foreseeable future.


Assuntos
Oligoquetos , Animais , Florestas , Espécies Introduzidas , Folhas de Planta , Solo
19.
Int J Mol Med ; 41(4): 2252-2262, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29336466

RESUMO

In the present study, the neuroprotective potential of magnolol against ischemia-reperfusion brain injury was examined via in vivo and in vitro experiments. Magnolol exhibited strong radical scavenging and antioxidant activity, and significantly inhibited the production of interleukin­6, tumor necrosis factor­a and nitrite/nitrate (NOX) in lipopolysaccharide-stimulated BV2 and RAW 264.7 cells when applied at concentrations of 10 and 50 µM, respectively. Magnolol (100 µM) also significantly attenuated oxygen­glucose deprivation­induced damage in neonatal rat hippocampal slice cultures, when administered up to 4 h following the insult. In a rat model of stable ischemia, compared with a vehicle­treated ischemic control, pretreatment with magnolol (0.01­1 mg/kg, intravenously) significantly reduced brain infarction following ischemic stroke, and post­treatment with magnolol (1 mg/kg) remained effective and significantly reduced infarction when administered 2 h following the onset of ischemia. Additionally, magnolol (0.3 and 1 mg/kg) significantly reduced the accumulation of superoxide anions at the border zones of infarction and reduced oxidative damage in the ischemic brain. This was assessed by measuring the levels of NOX, malondialdehyde and myeloperoxidase, the ratio of glutathione/oxidized glutathione and the immunoreactions of 8­hydroxy­2'­deoxyguanosine and 4­hydroxynonenal. Thus, magnolol was revealed to protect against ischemia­reperfusion brain damage. This may be partly attributed to its antioxidant, radical scavenging and anti­inflammatory effects.


Assuntos
Antioxidantes/uso terapêutico , Compostos de Bifenilo/uso terapêutico , Isquemia Encefálica/tratamento farmacológico , Encéfalo/efeitos dos fármacos , Lignanas/uso terapêutico , Fármacos Neuroprotetores/uso terapêutico , Traumatismo por Reperfusão/tratamento farmacológico , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Isquemia Encefálica/metabolismo , Isquemia Encefálica/patologia , Linhagem Celular , Glucose/metabolismo , Masculino , Camundongos , Estresse Oxidativo/efeitos dos fármacos , Oxigênio/metabolismo , Células RAW 264.7 , Ratos Sprague-Dawley , Traumatismo por Reperfusão/metabolismo , Traumatismo por Reperfusão/patologia
20.
Neurol Res ; 40(2): 130-138, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29262766

RESUMO

Objectives Focal cerebral ischemia may induce synaptic, electrophysiological, and metabolic dysfunction in remote areas. We have shown that the remote dendritic spine density changes and electrophysiological diaschisis in the acute and subacute stages after stroke previously. Here, we further evaluated electrophysiological outcomes and synapto-dendritic plasticity in long-term recovery in the contralateral cortex following focal cerebral ischemia. Methods Male Sprague-Dawley rats were subjected to intraluminal suture occlusion for 90 min or sham-occlusion. Somatosensory electrophysiological recordings (SSEPs) and neurobehavioral tests were recorded each day for 28 days. Postmortem brains were sectioned and subjected to Nissl staining and Golgi-Cox impregnation through a 28-day period following ischemic stroke. Results In the ipsilateral cortex, infarct size in the cortex and striatum was decreased after the subacute stage; the brains showed reduced swelling in the cortex and stratum 3 days after ischemic insults. Dendritic spine density and SSEP amplitude decreased significantly during a 28-day recovery period. In the contralateral cortex, dendritic spine density and SSEP amplitude decreased significantly for 21 days after ischemic stroke, but recovered to baseline by day 28. The deterioration of the dendritic spine (density reduction) in the ischemic cortex was observed; however, this increased neuroplasticity in the contralateral cortex in the subacute stage. Discussion Focal cerebral ischemia-reperfusion induces time-dependent reduction of dendritic spine density and electrophysiological depression in both the ipsilateral and contralateral cortices and intact brain. This neuroanatomical and electrophysiological evidence suggests that neuroplasticity and functional re-organization in the contralateral cortex is possible following focal cerebral ischemia.


Assuntos
Córtex Cerebral/patologia , Córtex Cerebral/fisiopatologia , Lateralidade Funcional , Ataque Isquêmico Transitório/patologia , Ataque Isquêmico Transitório/fisiopatologia , Recuperação de Função Fisiológica , Animais , Corpo Estriado/patologia , Corpo Estriado/fisiopatologia , Espinhas Dendríticas/patologia , Espinhas Dendríticas/fisiologia , Modelos Animais de Doenças , Potenciais Somatossensoriais Evocados , Masculino , Plasticidade Neuronal/fisiologia , Distribuição Aleatória , Ratos Sprague-Dawley , Recuperação de Função Fisiológica/fisiologia
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