Final answer:
The correct answer is C. I87.011, L97.414, with the postthrombotic syndrome coded first, followed by the specific ulcer code.
Step-by-step explanation:
The correct coding and sequencing for a case involving a nonhealing skin ulcer of the right heel with bone necrosis due to postthrombotic syndrome are I87.011, for postthrombotic syndrome with ulcer of lower extremity, followed by L97.414, for ulcer of heel and midfoot with necrosis of bone. This sequence places the underlying condition, postthrombotic syndrome, first, followed by the specific location and complication of the ulcer as per coding guidelines. It is essential to accurately code such cases to ensure appropriate patient treatment, billing, and statistical tracking.