Osteoradionecrosis (ORN) is a condition that results from the damaging effects of ionizing radiation therapy. Although an uncommon side effect of radiation treatment for cancers arising in the mouth, the oropharynx and the paranasal sinuses, when it occurs ORN can have devastating consequences for the patient. ORN is defined as destruction of the bone, associated with pain and bone exposure, either inside the mouth or through the external skin. Radiation results in a decreased blood supply to the bone that predisposes it to secondary infection. This condition affects three to five percent of patients who undergo radiation treatment to the head and neck area, with the lower jaw being far more sensitive to radiation damage than the upper jaw.
There are different grades of severity of ORN, depending on the amount of bone destruction that has occurred. Symptoms include pain, and in the most severe form a pathologic fracture may develop, leading to the development of a fistula through which saliva drains.
The prevention of osteoradionecrosis is accomplished through meticulous dental care and the avoidance of oral surgery following radiation therapy. Ideally patients will undergo a thorough dental evaluation before radiation treatment, and any dental procedures should be performed before therapy. Once radiation therapy has been given, hyperbaric oxygen may protect the bone if it’s administered prior to dental procedures that are performed in the area that was exposed to radiation therapy.
The development of osteoradionecrosis appears to be related to the total dose of radiation that is administered to the bone. Patients who receive secondary courses of radiation therapy are at greater risk. The surgeons who are performing operations in patients who have been exposed to radiation therapy must be very meticulous in designing the operation in order to avoid making cuts in the bone that may lead to bone destruction.
The treatment depends on the severity of the condition. In the early stages of the disease, the removal of exposed, nonviable bone with closure of the lining of the oral cavity can arrest the condition and prevent further progression. In more severe cases, the options are limited and require more definitive procedures. In these cases, the use of hyperbaric oxygen to improve the condition is most often not successful.
The best option for a predictable outcome is the removal of the portion of the diseased bone and replacement with new vascularized bone using microvascular surgery. Transfer of sections of new bone can come from the fibula, scapula and the iliac crest. The procedure may also require importing healthy soft tissue to reline the oral cavity and the overlying skin. The blood supply to the bone is restored by microscopic attachment of the nutrient artery and vein to a recipient artery and vein in the neck. This technique has proven to be reliable and predictable in this condition. The full extent of the damaged native bone must be determined during the surgery in an effort to avoid the progression of this process in the native mandible after importing the healthy bone into the defect created by removing the diseased segment.
Patients who undergo this procedure can enjoy resolution of pain and reestablishment of the structure of the lower third of the face. These patients are also candidates for dental rehabilitation and may include implants that can give them a fully functioning jaw as a result.