Which joint is most likely to progress to nonunion after a triple arthrodesis?

Which joint is most likely to progress to nonunion after a triple arthrodesis?

• A. Subtalar
• B. Tibiotalar
• C. Calcaneocuboid
• D. Talonavicular

Answer: (D)

The key idea is that after a triple arthrodesis, the joint most likely to fail to unite is the talonavicular joint. This joint carries a lot of stress after fusion because it sits at the hub of hindfoot motion and bears substantial weight and shear forces. Its healing surface is large, and achieving perfect apposition across that surface with solid cancellous bone contact can be challenging, especially if bone quality is poor or fixation isn’t optimal. The result is a higher risk of persistent motion at the fusion site and, consequently, nonunion. In contrast, the subtalar and calcaneocuboid joints tend to heal more reliably due to relatively better bone contact and vascular supply at those sites, provided the fixation is solid and biologic factors are favorable. So, while nonunion can occur at any fused site, the talonavicular joint is the most common weak link in a triple fusion.

The key idea is that after a triple arthrodesis, the joint most likely to fail to unite is the talonavicular joint. This joint carries a lot of stress after fusion because it sits at the hub of hindfoot motion and bears substantial weight and shear forces. Its healing surface is large, and achieving perfect apposition across that surface with solid cancellous bone contact can be challenging, especially if bone quality is poor or fixation isn’t optimal. The result is a higher risk of persistent motion at the fusion site and, consequently, nonunion.

In contrast, the subtalar and calcaneocuboid joints tend to heal more reliably due to relatively better bone contact and vascular supply at those sites, provided the fixation is solid and biologic factors are favorable. So, while nonunion can occur at any fused site, the talonavicular joint is the most common weak link in a triple fusion.