Osteoradionecrosis (ORN) refers to a severe delayed radiation-induced injury and is characterized by bone tissue necrosis and failure in healing. There is some overlap with the term radiation osteitis.
Microvascular damage is thought to result in altered blood supply to the bone. This limits the ability of the tissues to repair normal wear and tear which, in turn, eventually results in the tissue breakdown seen on imaging.
Usually, large radiation doses are required for osteoradionecrosis to occur (e.g. <3000-5000 cGy) 2.
While it can involve any bone within the irradiated field, there are specific sites in which osteoradionecrosis is more commonly seen. These include:
- mandible: mandibular osteoradionecrosis: this site is particularly prone due to its superficial location and high doses of radiation required to radically treat naso-oropharyngeal tumors
- chest wall-shoulder-humerus-scapula
- bony pelvis
While there are general features, radiographic features can somewhat vary with the site of involvement.
With mandibular osteoradionecrosis, there can be ill-defined cortical destruction without sequestration. In osteoradionecrosis of the ribs, clavicle, scapula, and humerus, radiography may demonstrate 2 :
- osteopenia: typically occurs after ~1 year postirradiation 4
- disorganization and coarsening of trabecular architecture
- cortical irregularity
- heterogenous bone density
With mandibular osteoradionecrosis, CT may additionally show cortical interruptions and loss of spongiosa trabeculation 6. In other sites, CT may show the presence of subtle fractures, alterations in bone architecture and dystrophic soft-tissue calcification.
On MRI, they can be the development of new heterogeneous signal within the marrow of an irradiated area (intermediate or low T1 signal, intermediate or high T2 signal). Osteoradionecrosis with or without osteomyelitis can be extremely difficult to differentiate from a recurrent tumor. Adjacent muscles may appear edematous and show intense enhancement, which can be difficult to differentiate from recurrent tumor if bone changes are not visible on CT 10.
In osteoradionecrosis of the spine, hematopoietic cellular elements of the spinal marrow can also be replaced with fat, which then has 2
- T1: high signal intensity
- T2: intermediate signal intensity
Treatment and prognosis
It either stabilizes or gradually worsens, which then becomes notoriously difficult to manage.
To give a meaningful differentiation, location and imaging modality needs to be taken into account. General differential consideration includes:
- original tumor recurrence
- radiation-induced secondary tumor e.g. sarcoma
- complicating infection: osteomyelitis (can also be an association) 10
- 1. Hermans R. Imaging of mandibular osteoradionecrosis. Neuroimaging Clin. N. Am. 2003;13 (3): 597-604. - Pubmed citation
- 2. Mitchell MJ, Logan PM. Radiation-induced changes in bone. Radiographics. 18 (5): 1125-36. Radiographics (citation) - Pubmed citation
- 3. Store G, Larheim TA. Mandibular osteoradionecrosis: a comparison of computed tomography with panoramic radiography. Dentomaxillofac Radiol. 1999;28 (5): 295-300. doi:10.1038/sj/dmfr/4600461 - Pubmed citation
- 4. Bluemke DA, Fishman EK, Scott WW. Skeletal complications of radiation therapy. Radiographics. 1994;14 (1): 111-21. Radiographics (citation) - Pubmed citation
- 5. Rolton DJ, Blagg SE, Hughes RJ. Osteoradionecrosis of the lumbar spine 25 years after radiotherapy. J Bone Joint Surg Br. 2011;93 (9): 1279-81. doi:10.1302/0301-620X.93B9.25991 - Pubmed citation
- 6. Hermans R, Fossion E, Ioannides C et-al. CT findings in osteoradionecrosis of the mandible. Skeletal Radiol. 1996;25 (1): 31-6. - Pubmed citation
- 7. King AD, Griffith JF, Abrigo JM et-al. Osteoradionecrosis of the upper cervical spine: MR imaging following radiotherapy for nasopharyngeal carcinoma. Eur J Radiol. 2010;73 (3): 629-35. doi:10.1016/j.ejrad.2008.12.016 - Pubmed citation
- 8. Wu LA, Liu HM, Wang CW et-al. Osteoradionecrosis of the Upper Cervical Spine after Radiation Therapy for Head and Neck Cancer: Differentiation from Recurrent or Metastatic Disease with MR Imaging. Radiology. 2012;264 (1): 136-45. doi:10.1148/radiol.12111714 - Pubmed citation
- 9. Urbaniak JR, Association AO. Osteonecrosis, etiology, diagnosis, and treatment. Amer Academy of Orthopaedic. (1997)
- 10. Glastonbury CM, Parker EE, Hoang JK. The postradiation neck: evaluating response to treatment and recognizing complications. AJR Am J Roentgenol. 2010;195 (2): W164-71. doi:10.2214/AJR.09.4122 - Pubmed citation