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Optimal Distal Screw Alignment in the Gamma Nail

Published online by Cambridge University Press:  05 May 2011

Ching-Kong Chao*
Affiliation:
Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10672, R.O.C.
Chun-Ching Hsiao*
Affiliation:
Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10672, R.O.C.
Po-Quang Chen*
Affiliation:
Department of Orthopedic Surgery, National Taiwan University Hospital, Taipei, Taiwan 100, R.O.C.
*
* Professor
** Graduate student
** Graduate student
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Abstract

The effect of stress distribution due to the changes of the distal screw alignment in relation to the Gamma nail and the femoral shaft is thoroughly studied in this paper. Failure of the Gamma nail composite occurs through the cranial aperture of the distal screws and the insertion hole for the lag screw due to nonunion, delayed-union and continued weight-bearing. A three-dimensional finite element model was used to study the fractured femur, the Gamma nail, the lag screw and the distal locking screws. The first and the second distal screws were inserted into the Gamma nail in four different configurations. We found that the stress of the Gamma nail composite was substantially reduced with the two screws configured in the anterior to posterior direction. This alignment can bear greater loading in the more demanding fracture types. In the subtrochanteric fracture or the comminuted fractures at the proximal femur, the optimal alignment of the two distal screws was in the anterior to posterior direction.

Type
Articles
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2002

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