Radiation Osteitis Osteonecrosis

The term radiation osteitis was originally coined by Ewing (1926) to describe a series of pathological changes that occur in bone after irradiation. Irradiation of bone may result in immediate or delayed arrest of cell division, cell death with reduced matrix production, metaplasia, or neoplasia. The irradiated bones manifest ischemic necrosis, sclerosis, and occasional infection of radionecrosis. These changes occur as secondary reactions to the destruction of osteoblasts and microvascular occlusion (King et al. 1979). The radiation effects on bone are dose-dependent. The threshold radiation dose for the bone changes is estimated to be 30 Gy, and cell death occurs at 50 Gy (Bragg et al. 1970). In a study of 100 patients with radiation osteitis, Bragg and associates (1970) noted involvement in decreasing order of the mandible (32%), clavicle (18%), humeral head (14%), ribs (9%), and femur (9%). The mandible is more commonly affected than the maxilla because of the compactness of bone and poor blood supply (Guttenberg 1974) and is more vulnerable when the irradiated tumor is located close to it (Bedwinek et al. 1976) (Fig. 7.14). Unlike most radionecrosis the mandibular lesion starts early after the completion of irradiation.

Radiographically, altered bones are irregularly mottled due to the mixture of porosis, coarsened trabeculae, and sclerosis (DeSantos

Mandibular Radionecrosis

Fig. 7.16A-C Initial and follow-up radiation osteitis. A Conventional X-ray tomograph of the sternum taken in a 48-year-old female 1 year after completion of 50 Gy 6 MeV irradiation for sarcoma in the medial aspect of the right clavicle shows chronic radiation osteitis with irregular sclerosis and osteonecroses (three arrows) and left clavicle (two arrows) (arrowheads altered sternal notch and joints). B The initial pinhole scan taken at the same time as the tomograph shows intense uptake in the medial aspect of the right clavicle and also in the left clavicular end. C Follow-up pinhole scan taken 6 years later shows persistent uptake with further intensification in the right clavicle that bore the sarcoma and improved uptake in the left clavicle that did not bear the tumor

Fig. 7.16A-C Initial and follow-up radiation osteitis. A Conventional X-ray tomograph of the sternum taken in a 48-year-old female 1 year after completion of 50 Gy 6 MeV irradiation for sarcoma in the medial aspect of the right clavicle shows chronic radiation osteitis with irregular sclerosis and osteonecroses (three arrows) and left clavicle (two arrows) (arrowheads altered sternal notch and joints). B The initial pinhole scan taken at the same time as the tomograph shows intense uptake in the medial aspect of the right clavicle and also in the left clavicular end. C Follow-up pinhole scan taken 6 years later shows persistent uptake with further intensification in the right clavicle that bore the sarcoma and improved uptake in the left clavicle that did not bear the tumor

Osteonecrosis The Sacrum
Fig. 7.17 Suppressed tracer uptake in irradiated adult bone. Posterior pinhole scan of the sacrum in a 56-year-old female irradiated 2 years previously for stage II cervical cancer after hysterectomy shows a large area of photo-penia in the main body of the sacrum

and Libshitz 1979) (Fig. 7.15A). New bones gradually form, replacing irradiated bones in the course of years (Fig. 7.16). Computed or conventional tomography (Fig. 7.16A) and MRI (Fig. 7.14A) demonstrate osteosclerosis mixed with lucent areas of fibrosis as well as atrophied bone marrow at this stage.

Scintigraphy of radiation osteitis resulting from a large-dose irradiation (50 Gy or more) reveals intense uptake (Figs. 7.14B and 7.15B), contrasting with the well-known suppressed uptake in bones irradiated with a lower dose and without osteitis (Fig. 7.17). The uptake is typically uniform and well defined in the early phase, denoting subacute inflammation (Fig. 7.14B). However, it is gradually transfigured to a mottled pattern in the chronic phase due to irregular mixing of osteonecrosis, regeneration, and sclerosis (Fig. 7.15B and 7.16B), and eventually returning to a uniform appearance in the late reparative phase now due to extended new bone formation (Fig. 7.16C). On the other hand, avascular necrosis (Rosenthall 1987) and fibrous replacement are indicated by "cold" defects or photopenia when they are sufficiently large (Fig. 7.15).

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Responses

  • LILY
    Does irradiated bones sow up on scans?
    8 years ago
  • adelmo
    What is radiation osteitis?
    8 years ago

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