Analysis of Micromotion in a Talonavicular Arthrodesis With and Without a Calcaneal Displacement Osteotomy in a Cadaver Model.

The isolated talonavicular joint arthrodesis can be beneficial to correct midfoot deformities involving the talonavicular joint, including collapsing pes planovalgus. Studies show that isolated talonavicular arthrodesis has a higher nonunion rate because of micromotion; thus, other procedures should be used in conjunction with it. We sought to determine if adding an adjunctive medial calcaneal displacement osteotomy helps to reduce the ground reactive force and, therefore, the micromotion on the talonavicular joint. We used 4 below-knee limbs to study the force placed on the joint in an isolated talonavicular arthrodesis compared with the same procedure with an adjunctive calcaneal osteotomy under weightbearing simulation. A 0.5-inch circular force sensing resistor was placed within the talonavicular and used to check the force on the joint after a 5-lb force was added to the proximal limb. The resistance was quantified with force measured as a direct inverse. This procedure was performed 3 times for each limb. The mean resistance before and after calcaneal osteotomy was analyzed with use of the paired t test. In the pre-calcaneal osteotomy sites, the mean resistance given in 200 kΩ was 388.2 ± 565.9 compared with 1016.6 ± 482.7 in the post-calcaneal osteotomy sites (p = .02). Findings from this cadaver study indicate reduction in forces to the talonavicular joint with an adjunctive calcaneal osteotomy. We conclude that it can be a beneficial adjunctive procedure for patients at a high risk of nonunion, such as those with obesity or diabetes or those who smoke. These patients could benefit from the decreased micromotion that the adjunctive procedure allows.