osteoradionecrosis

Osteonecrosis
of the sacrum following pelvic radiotherapy. T1-weighted TSE fs coronal post Gad: diffuse signal increase in the sacrum bilaterally with a centrally decreased signal area on the right side compatible with osteonecrosis.
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Osteonecrosis
of the sacrum following pelvic radiotherapy. T1-weighted TSE axial post Gad: subtle hypointense line in the left anterior massa laterale parallel to the SIJ, compatible with an insufficiency fracture.
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Tumor and
tumorlike conditions of the pleura and juxtapleural region: review of imaging findings. Diagnosis: radio-osteonecrosis and/or osteomyelitis. Technique: standard chest radiography and contrast-enhanced chest CT. Description: A 43-year-old man presented with left-sided chest pain. His medical history includes a lobectomy of the left upper lobe and radiotherapy. The postero-anterior chest radiograph (a) shows deformity and volume loss of the left hemithorax with a dense aspect of the lobectomy space. The coronal and axial CT thorax in bone window (b, c) reveals extensive periosteal reaction of the left ribs with inhomogeneous osteosclerosis and necrotic bone (with a typical denser aspect). The mediastinal window setting (d) is better to evaluate the adjacent soft tissue component and the fluid in the lobectomy space
insightsimaging.springeropen.com • CC-by-4.0
Radiopaedia • CC-by-nc-sa 3.0 • de

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.

Pathology

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) .

Location

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
  • spine
  • bony pelvis

Radiographic features

While there are general features, radiographic features can somewhat vary with the site of involvement.

Plain radiograph

With mandibular osteoradionecrosis, there can be ill-defined cortical destruction without sequestration. In osteoradionecrosis of the ribs, clavicle, scapula, and humerus, radiography may demonstrate :

  • osteopenia: typically occurs after ~1 year postirradiation
  • disorganization and coarsening of trabecular architecture
  • cortical irregularity
  • heterogenous bone density
CT

With mandibular osteoradionecrosis, CT may additionally show cortical interruptions and loss of spongiosa trabeculation. In other sites, CT may show the presence of subtle fractures, alterations in bone architecture and dystrophic soft-tissue calcification.

MRI

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 .

In osteoradionecrosis of the spine, hematopoietic cellular elements of the spinal marrow can also be replaced with fat, which then has

  • T1: high signal intensity
  • T2: intermediate signal intensity 

Treatment and prognosis

It either stabilizes or gradually worsens, which then becomes notoriously difficult to manage.

Differential diagnosis

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)

See also

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Osteoradionekrose:
Aseptische
Knochennekrose
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