The sling apparatus inserts on which structure?

• A. Distal phalanx
• B. Navicular bone
• C. Middle phalanx
• D. Proximal phalanx

Answer: (A)

The sling apparatus is the component of the distal navicular (sesamoidean) system that helps suspend and stabilize the distal end of the digit. Its job is to form a supportive sling around the distal phalanx so the deep digital flexor tendon can function smoothly as the toe bears weight. Because of this role, the attachment point (insertion) is on the distal phalanx, not on the navicular bone or the more proximal phalanges. The navicular bone and the proximal/distal joints contribute to the sling’s structure, but the actual insertion site for this apparatus is the distal phalanx.