Osteoradionecrosis pathophysiology — ORE Part 1 MCQ
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Correct answer: E — Radiation-induced hypovascular, hypocellular and hypoxic bone has impaired healing capacity
Explanation lettering: C = shown as A · A = shown as B · D = shown as C · B = shown as D
The correct answer is E. This patient has osteoradionecrosis (ORN), a serious late complication of head and neck radiotherapy defined as exposed, nonviable bone failing to heal spontaneously beyond 3 months in the absence of tumour recurrence. Option E correctly identifies Marx's hypoxic-hypocellular-hypovascular theory, the gold-standard model of ORN pathophysiology: radiation induces endarteritis, vascular obliteration and loss of osteocytes, resulting in chronically hypoxic, acellular, poorly vascularised bone that cannot mount an effective healing response. When trauma (extraction) occurs in this tissue, the impaired microcirculation and reduced cellular activity prevent normal bone repair and epithelialisation. Options A and B are mechanistically incorrect: radiotherapy causes vasoobliteration (not hypervascularity) and osteocyte loss (not increased osteoblast activity). Option C lacks any pathophysiological basis in ORN. Option D is biologically implausible. The stem provides all necessary information: high radiation dose, post-extraction timing, 3-month duration, pain, and exclusion of recurrence.
Reference: Marx RG. Osteoradionecrosis: a new concept of its pathophysiology. Journal of Oral and Maxillofacial Surgery 1983;41(5):283–288. https://pubmed.ncbi.nlm.nih.gov/6572704/