YIJOM-4218; No of Pages 6 Please cite this article in press as: Danielsson D, et al. Osteoradionecrosis, an increasing indication for microvascular head and neck reconstruction, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.06.009 Clinical Paper Reconstructive Surgery Osteoradionecrosis, an increasing indication for microvascular head and neck reconstruction D. Danielsson, C. Gahm, S. Haghdoost, E. Munck-Wikland, M. Halle: Osteoradionecrosis, an increasing indication for microvascular head and neck reconstruction. Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxx. ã 2019 Published by Elsevier Ltd on behalf of International Association of Oral and Maxillofacial Surgeons. D. Danielsson 1,2 , C. Gahm 3 , S. Haghdoost 4 , E. Munck-Wikland 3 , M. Halle 5,6 1 Department of Clinical Science, Intervention and Technology, Division of Ear, Nose and Throat Diseases, Karolinska Institute, Stockholm, Sweden; 2 Patient Area Craniofacial Diseases, Karolinska University Hospital, Stockholm, Sweden; 3 Department of Otorhinolaryngology, Head and Neck Surgery, Karolinska University Hospital and Karolinska Institute, Stockholm, Sweden; 4 Department of Molecular Bioscience, Centre for Radiation Protection Research, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden & University of Caen Normandy, Laria- Cimap, Caen, France; 5 Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden; 6 Reconstructive Plastic Surgery, Karolinska University Hospital, Stockholm, Sweden Abstract. Better cancer treatment has led to a steadily growing population of cancer survivors suffering from late adverse effects after cancer treatment. The aim of this study was to investigate whether there has been an increase in free flap reconstruction due to osteoradionecrosis (ORN). A retrospective review was conducted to identify all consecutive head and neck free flap reconstructions performed over an 18-year period (1995–2012) at Karolinska University Hospital. A total of 235 free flaps were identified. Cases were divided into two groups: head and neck cancer reconstructions and ORN reconstructions. A comparison between the two groups showed longer survival (P < 0.001) and higher rates of late complications (P < 0.001) among ORN cases. ORN as an indication for reconstruction increased over time, from 7.0% of the total number of free flaps performed in 1995–2000, to 15.2% during the period 2001–2006, and to 27.3% in 2007–2012 (P < 0.001). This, in accordance with the results of other studies, highlights the importance of the appropriate allocation of resources within the healthcare system to treat this patient group within the steadily increasing population of cancer survivors. Key words: ORN; osteoradionecrosis; free flap; head and neck; microvascular reconstruc- tion. Accepted for publication 7 June 2019 Introduction Osteoradionecrosis (ORN) is a severe side effect following radiation therapy. It is commonly described as a condition in which devitalized irradiated bone becomes exposed through a wound in the overlying skin or mucosa. Tumour recurrence must be ruled out and the wound must be present for a period ex- ceeding 3 months 1–4 . The pathophysiology of ORN remains unclear. Marx concluded that ORN should be considered a non-healing wound result- ing from a disturbance of metabolic and tissue homeostasis, and it has been stated that ORN is a result of hypoxic, hypovas- cular, and hypocellular tissues being prone to tissue breakdown, leading to a non- healing wound 3–6 . Infection, if present, is superficial rather than interstitial. More recent studies have suggested that ORN Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxx https://doi.org/10.1016/j.ijom.2019.06.009, available online at https://www.sciencedirect.com 0901-5027/000001+06 ã 2019 Published by Elsevier Ltd on behalf of International Association of Oral and Maxillofacial Surgeons.