Biomechanical comparison of Schanz screws placement modes-how can stability by external fixation be raised?

Kwang-Rim Choe; Mun-Sik Ko; Song-Gun Pak; Kwang-Myong Choe; Tong-Won Mun; Hyo Sim

Abstract

AbstractBackground: At present, external fixators are being used widely in open fractures of the long bones and also accepted as a temporary skeletal stabilization even in closed fractures. Therefore, it is essential to increase the stability which is provided by those devices for good outcomes. We hypothesized prior to the study that the greater is the distance between the Schanz screws inserted in each fracture fragment, the higher is the stability of fracture site provided by external fixation in long bone shaft fractures. Method: 3-D finite element method was undertaken to obtain biomechanical properties in external fixators and fractured long bones, and compared them in accordance with Schanz screws placement modes determined by distances between the screws in one fracture segment under anterior-posterior bending and axial compression loads. Results: Under the bending and axial compression, stiffness and displacement values at the fracture sites of the long bone shaft when treated with external fixation were decreased according to increase of distance between Schanz screws in one fracture segment. However, when the distance is increased more than a certain value, the external fixation produced greater stiffness and displacement on the contrary. Conclusion: Stability supported by external fixation can usually be enhanced by setting placement of Schanz screws further apart from each other in one fracture segment, however, decrease reversely in distances between the screws more than a certain value.Keywords: external fixator, Schanz screw, displacement, stiffness, fractureCite this ArticleKwang-Rim Choe, Mun-Sik Ko, Song-Gun Pak, Kwang-Myong Choe, Tong-Won Mun, Hyo Sim. Biomechanical Comparison of Schanz Screws Placement modes-how can Stability by External Fixation be Raised? Research & Reviews: Journal of Surgery. 2020; 9(1): 25–33p.