ReviewOsteoradionecrosis of the jaws: current understanding of its pathophysiology and treatment
Introduction
In 1922, Regaud published what was arguably the first report about osteoradionecrosis (ORN) of the jaws after radiotherapy.1 During the past 80 years, this condition has persisted as a consequence of radiotherapy for head and neck cancer in an appreciable minority of patients. Since then several theories have been propounded to explain its cause including the release of histamine, the theory of radiation, trauma, and infection2 and, until recently, the most widely accepted theory of hypoxia, hypovascularity, and hypocellularity.3 There is a general consensus, however, about the clinical presentations of ORN, which are pain, drainage, and fistulation of the mucosa or skin that is related to exposed bone in an area that has been irradiated. Once ORN is recognised, it is irreversible and extremely difficult to treat. We explore recommendations and current theories about its aetiology, pathogenesis, and treatment.
Section snippets
Terminology and definition
Various terms and definitions of ORN are given in Table 1, Table 2. Perhaps the most widely used definition of ORN that affects the jaws is based on clinical presentation and observation: irradiated bone becomes devitalised and exposed through the overlying skin or mucosa without healing for 3 months, without recurrence of tumour.4
Although widely used, this definition is far from perfect, and can be criticised for two reasons; the duration of the bone's exposure to radiation, and the definition
Theories of the pathophysiology of osteoradionecrosis: a critical appraisal
Watson and Scarborough reported three crucial factors in the development of ORN based purely on clinical observations; exposure to radiotherapy above a critical dose; local injury; and infection.28 Early experimental models of the pathophysiology of ORN showed evidence of bacteria in tissues affected by ORN, and documented microscopic tissue changes, namely thickening of arterial and arteriolar walls, loss of osteocytes and osteoblasts, and the filling of bony cavities with inflammatory cells.29
Contemporary understanding of the pathophysiology of osteoradionecrosis: radiation-induced fibroatrophic theory
Radiation-induced fibrosis is a new theory that accounts for the damage to normal tissues, including bone, after radiotherapy.47 It was introduced in 2004 when recent advances in cellular and molecular biology explained the progression of microscopically observed ORN.
The histopathological phases of the development of ORN closely reflect those seen in chronic healing of traumatic wounds.48 Three distinct phases are seen: the initial prefibrotic phase in which changes in endothelial cells
New protocols for prevention and treatment of osteoradionecrosis
Based on current understanding of the pathophysiology of ORN, new protocols could be developed for its prevention and treatment. Previously, patients who required multiple dental extractions or extensive surgical extractions, or both, might have been given HBO before and after operation. Instead, all patients having dental extractions could be given eight weeks of pentoxifylline 400 mg twice daily with tocopherol 1000 IU, starting a week before the procedure. If ORN developed then they could be
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