Resistência mecânica às forças de tração e flexão: proposta de novo desenho para os pinos de Schanz dos fixadores externos monolaterais

Mercadante, Marcelo Tomanik; Christian, Ralph Walter; Kojima, Kodi Edson; Hungria, José Octávio Soares; Francisco, Lúcio Nuno Favaro Lourenço; Yamaguti, Daniel Osamu; Trindade, Christiano Augusto de Castro; Sousa, Alan Robson Trigueiro de; Godoy, Guilherme Finardi; Júnior, Antônio G. de Mello; Bettarello, Flávio Jorge; Neto, Abner Cabral

doi:10.1590/s0102-36162008000600006

Cited by 2 publications

(3 citation statements)

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“…14 Oni et al 4 suggested that the use of Schanz screws made of titanium and with short shaft generates less stress and, therefore, less risk of failure. Mercadante et al 9 observed a greater resistance to flexion forces when the screw shaft was smaller (15 mm).…”

Section: Discussionmentioning

confidence: 96%

“…Studies with external fixators have shown that screws can support a large amount of flexion force, and that the thread/shaft transition is the point of least resistance of the implant. 9 , 12 , 13 …”

Section: Discussionmentioning

confidence: 99%

“…1 , 8 In the more classical technique descriptions from clinical or experimental trials, the screws are inserted manually until the thread is fixated through the cis (input) and trans (opposite) cortical bone and the shaft is fully supported in the cis cortical. 9 …”

Section: Introductionmentioning

confidence: 99%

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Finite element analysis of the equivalent stress distribution in Schanz screws during the use of a femoral fracture distractor

Giordano

Godoy‐Santos

Belangero

et al. 2017

Revista Brasileira de Ortopedia (English Edition)

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To evaluate the mechanical stress and elastic deformation exercised in the thread/shaft transition of Schanz screws in assemblies with different screw anchorage distances in the entrance to the bone cortex, through the distribution and location of tension in the samples.An analysis of 3D finite elements was performed to evaluate the distribution of the equivalent stress (triple stress state) in a Schanz screw fixed bicortically and orthogonally to a tubular bone, using two mounting patterns: (1) thread/shaft transition located 20 mm from the anchorage of the Schanz screws in the entrance to the bone cortex and (2) thread/shaft transition located 3 mm from the anchorage of the Schanz screws in entrance to the bone cortex. The simulations were performed maintaining the same direction of loading and the same distance from the force vector in relation to the center of the hypothetical bone. The load applied, its direction, and the distance to the center of the bone were constant during the simulations in order to maintain the moment of flexion equally constant. The present calculations demonstrated linear behavior during the experiment. It was found that the model with a distance of 20 mm between the Schanz screws anchorage in the entrance to the bone cortex and the thread/shaft transition reduces the risk of breakage or fatigue of the material during the application of constant static loads; in this model, the maximum forces observed were higher (350 MPa). The distance between the Schanz screws anchorage at the entrance to the bone cortex and the smooth thread/shaft transition of the screws used in a femoral distractor during acute distraction of a fracture must be farther from the entrance to the bone cortex, allowing greater degree of elastic deformation of the material, lower mechanical stress in the thread/shaft transition, and minimized breakage or fatigue. The suggested distance is 20 mm.

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Section: Discussionmentioning

confidence: 96%