Toe ulcers affect which part of P3?

• A. Flexor tuberosity
• B. Apex
• C. Dorsal ridge
• D. Proximal articular surface

Answer: (B)

The concept here is that toe ulcers occur on the solar surface of the coffin bone at the apex because this is the point that directly bears ground contact and the focal load during weight-bearing. Persistent pressure at the apex concentrates stress on the thin sole over the distal phalanx, predisposing to localized necrosis and ulceration. The flexor tuberosity is simply where the deep digital flexor tendon attaches on the palmar/sole aspect, not a typical ulcer site. The dorsal ridge sits on the dorsal surface, away from the sole, and the proximal articular surface is near the top of the bone where it meets the previous phalanx, not involved in toe ulcers. Therefore, the apex of P3 best explains toe ulcers.