Late Bone and Cartilage Reactions


The normally quoted endpoint is osteoradionecrosis. This is death of bone tissue due to loss of vascular support, and is most commonly seen in the mandible due to the frequently of head and neck treatments and its poor vascular supply.
In children, radiation of the growth plate can lead to growth arrest. It is vital to avoid these areas if possible.
In adults, radiation to cartilage can cause necrosis, although the cartilage is typically tougher than the bone.

Osteoradionecrosis of the Mandible

Clinical Features

Patients present with pain, swelling or ill fitting dentures. On examination, the alveolar bone of the mandible may be visible as a hole in the gingiva. Occasionally patients may present with a pathological fracture of the bone.


The mandible has a relatively poor blood supply, mainly derived from the inferior alveolar artery which enters posteriorly, and through capillaries at the attachment of muscles. In the elderly, the role of the inferior alveolar artery is less and most supply comes from muscle attachments. Radiation leads to eventual death of endothelial cells, narrowing and thrombosis of major vessels and loss of capillaries, with resulting hypoxia. The numbers of osteocytes are reduced. This leaves the mandible less able to withstand insults, such as infections from decaying teeth. These insults are more common in patients who receive head and neck radiotherapy, due to the concurrent loss of salivary gland function.


The best management is prevention. This is done by performing a full dental examination prior to radiotherapy commencing, with removal of diseased teeth and repair of salvageable teeth. Excellent oral care is required following radiation and patients should use fluoride trays daily to prevent further caries.

Fluoride trays look like mouthguards that are full of fluoride. Om nom nom.

If further surgery on the teeth is required, there is controversy over whether hyperbaric oxygen should be used prior and following the procedure. Good results have been shown in some studies, but the risk is thought to be sufficiently low not to warrant the expensive procedure by others. Hyperbaric oxygen has been shown to improve outcomes in patients who have established osteoradionecrosis. If unsuccessful, it can be coupled with removal of the dead bone and mandible reconstruction.

Tolerance Dose of Bone

The TD5/5 of bone is thought to be about 60 Gy with conventional fractionation. Note that the dose may be higher to bone if electrons or kilovoltage x-rays are used. For the mandible, the TD5/5 is lower, between 40 - 50 Gy. This must be considered with the significant involvement xerostomia has on the pathogenesis of osteoradionecrosis of the mandible.

Developing Bone

The developing bone is quite sensitive to radiation induced growth arrest, which may not become apparent until the next growth spurt. The TD5/5 is about 20 Gy with conventional fractionation, although there seems to be a large fractionation effect.

Adult Cartilage

Adult cartilage is relatively radioresistant, with a TD5/5 approaching 70 Gy. Most late effects are due to damage to vascular cells, in a similar way to osteoradionecrosis.

Scoring Systems

I have replicated the RTOG scale for late bone and cartilage reactions below:

Grade 0 1 2 3 4 5
Bone No late effect Reduced bone density, but asymptomatic Moderate pain, growth retardation, sclerotic changes Severe pain, arrest of growth, dense sclerosis Necrosis, pathological fracture Death
Joint No late effect Mild stiffness, mild limitation of movement Moderate findings Severe pain, limitation of movement Fixed joint, necrosis of cartilage Death


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