Alteration of Strain Distribution in Distal Tibia After Triple Arthrodesis: Experimental and Finite Element Investigations
Arthrodesis, or fusion of subtalar joints (STJs), is a well-accepted and a routine treatment in the end stage of ankle injuries or disorder, such as arthritis or fractures. Arthrodesis can restore daily life function quickly at the expense of limiting joint motion. A triple arthrodesis (TA) consists of the surgical fusion of the talocalcaneal (TC), talonavicular (TN), and calcaneocuboid (CC) joints in the foot. This study aimed at investigating the effects of TA on strain distribution around tibia near the ankle joint. A finite element (FE) model, generated using computed tomography (CT) images of the human ankle, was then used to estimate stress distribution on the ankle joint surface. Axial load was applied to a human cadaveric ankle before and after TA, and load patterns were determined in various anatomical positions by measuring strain distribution around the tibia. Therefore, the effects of fusion were investigated by comparing strain distribution obtained from experiment and from FE model before and following to fusion. A good agreement between the experiment and FE, for the mean value of experimentally measured strains per the strains determined by FEM was observed (1.4 ± 0.32 before TA, and 1.51 ± 0.49 after TA). Moreover, a well-accepted point-by-point comparison between FE results and experimentally measured strains was observed with a good correlation coefficient (r = 0.94). Results of this study showed that: (1) there was a significant difference in strain magnitude and strain distribution around the tibia before and after TA; (2) the strain and stress were more uniformly distributed after fusion; and (3) the peak strain and stress values were shifted to the lateral and anterolateral portion of the tibia after the fusion. Results of this investigation showed that STJs fusion reduces the average values of strains around the cortical bone through changing the pattern of load transmission at the ankle joint.