Abstract

Stabilization of fractures by external fixator is based on the mechanical connecting of the pins, screwed into the proximal and distal bone fragment. Site of fracture is left without any foreign materials, which is essential for prevention of infections. Aim of this work is to compare stability of constructs bone model-external fixators of different types (Ortofix, Mitković, Charneley and Ilizarov). Stability is estimated under compression and bending (vertical and horizontal forces of 100 kg magnitudes, with distances between pins of 4 cm). Methodology: The mathematical-computer software (Tower, Planet and Planet Pro) was used in the laboratory for accurate measurements of MDP “Jelšingrad” company, Banjaluka. Interfragmental motions in millimeters at the appliance of vertical and horizontal forces were 2.80/2.56 at Ortofix (uniplanar fixator), 1.57/1.56 and fixator by Mitković-M20 (uniplanar fixator with convergent oriented pins), 0.16/0.28 at Charnely’s external fixator (biplanar fixator), and 4.49/0.114 mm at Ilizarov’s external fixator (fixator with two proximal and two distal rings, each attached on the 6 Kirschner wires). Results and discussion: It has confirmed that uniplanar fixation is easier and provides sufficient biomechanics circumstances in the site of fracture for bone healing, especially if the pins are oriented convergently. Ilizarov’s fixator is multiplanar fixator, but its stability is dependent of tightness of wires, and provides adequate stability only in transversal plane. By other words, each fixator has its indications; selection of the fixator should be based on theirs mechanic characteristics, fracture geometry, and potential of bone healing, with permanent simplification of treatment, which has to be safe and acceptable for the patient. The main advantage of this study is its nature–the comparison of four most used external fixators, by the only one possible way–on the bone model. Each other way of comparison would result with much more questions than answers, due to unacceptable high bias of other parameters, which significantly influences on the results of the study.

Key words: external fixator, biomechanics, stability, Ilizarov, Ortofix.