Ilizarov wire tensioning - The ring deflection phenomenon

Abstract

Background and aims: Gavril Ilizarov pioneered the use of fine wire circular ring fixators within Soviet Russia in the early 1950's and advocated a wire tension within the range of 980 N–1275 N. Ilizarov used a technique known as “Russian tensioning” whereby a wire is subtended around the fixation bolt in order to produce wire tension across the frame. The use of a mechanical tensioning device was conceived to elongate the wire and impart tension on the wire.This biomechanical study compares these two techniques at achieving adequate tension and aims to quantify how initial wire tension is affected by the addition of a second, orthogonal wire. Methods: In this in vitro series of experiments, a stabilised, testing rig utilised an initial wire passed across a 160mm stainless-steel ring. A Russian tensioning method and mechanical tensioning device was used. A calibrated tensiometer was used to record spoke deflection which was then converted to Newtons of tension. Results: When Russian tensioning, adequate tension was only achieved at 90° of bolt rotation. Notably the first wire tensioned did not achieve a suitable tension until the 2nd wire was added across all angles of bolt rotation.Only at 110 and 130KgF was initial wire tension adequate. Following the addition of an orthogonal wire at both of these settings wire tension was maintained within the acceptable range. Conclusion: Both methods of tensioning are an effective method of tensioning in Ilizarov constructs. A ''ring deflection phenomenon'' may cause an initial loss of tension but the addition of an orthogonal wire ensures adequate wire tension, provided there is 90° of bolt rotation with Russian tensioning or at least 110 KgF with a mechanical tensioner.

Keywords

• Ilizarov
• Biomechanics
• Wire-tensioning