Comparative Stiffness Characteristics of Ilizarov- and Hexapod-type External Frame Constructs
Hemant Sharma, Carl Fenton, Daniel Henderson, Mikhail Samchukov, Alexander Cherkashin
Abstract
BACKGROUND: The Ilizarov method and fixator are clinically recognised for the treatment of fractures, limb salvage and deformity correction. There have been extensive studies determining the basic mechanism for fracture healing using this technique. It is generally accepted that circular frames optimise the mechanical environment by reducing shear strain across the fracture while maintaining axial micromotion so as to promote fracture healing. There have been several new hexapod-type frames introduced into the market over the past 20 years with little comparative research into their biomechanical properties and resultant effects on the fracture environment. QUESTIONS/PURPOSES: . METHODS: Testing was performed on standardised four-ring TSF and TL-HEX constructs matched by identical frames using Ilizarov threaded rod constructs for each set of components. All frames were tested under physiological levels of axial, bending and torsional loading. Load-deformation properties for each construct under each mode of loading were calculated and analysed statistically using ANOVA. RESULTS: Under axial loading, the Ilizarov construct utilising TL-HEX components demonstrated the greatest rigidity followed by the Ilizarov construct using TSF components. Under bending loads, the difference in rigidity between constructs was similar but less marked. Under torsional loading, both hexapod frames were seen to be significantly more rigid than the Ilizarov constructs. Overall deformation around neutral loading was much higher in the TSF frame due to an observed significant "toe-in" laxity in the strut universal joints. The remaining deformation of both hexapod frames was similar with a higher level of TL-HEX rigidity in axial loading and a higher level of TSF rigidity in bending and torsion. CONCLUSION: into clinical significance. HOW TO CITE THIS ARTICLE: Comparative Stiffness Characteristics of Ilizarov- and Hexapod-type External Frame Constructs. Strategies Trauma Limb Reconstr 2021;16(3):138-143.