A 70-year-old woman presented to her referral hospital with a tumour on the right lateral aspect of the tongue with clinical stage T2N0M0. The biopsy was reported as squamous cell carcinoma.

The therapeutic modality decided at her hospital was external radiotherapy divided into 30 fractions (2 Gy/fraction), a total of 60 Gy for both cervical fields. The treatment was completed with brachytherapy with four Iridium 196 needles, a total of 50 Gy.
The disease completely subsided and the patient was free of the disease for one year, at which time she returned to the specialist when she presented with inflammatory symptoms in the irradiated area, with pain and fistula in the right mandibular angle.
The physical examination and the orthopantomography image were diagnostic of ORN of the right mandibular body, and it was decided to refer the patient to the Oral and Maxillofacial Surgery Department of the Hospital Universitario La Paz.

Initial treatment consisted of curettage, bone remodelling and hyperbaric oxygen treatment (Hospital Militar de Zaragoza, 17 sessions with 100% hyperbaric oxygen: 2.5 ATA-60 minutes).
Despite attempts at resolution with conservative treatment, the patient eventually developed a pathological fracture, leading to a right segmental mandibulectomy and reconstruction with a microvascularised fibula free flap.

The limits of the bone resection were determined from the radiological changes showing necrotic bone together with the intraoperative macroscopic image. The affected tissue was resected with a bone margin of 0.5-1 cm to bleeding bone, with en bloc removal of the intraoral mucosa and skin circumscribed to the extraoral fistula. The bone defect after mandibulectomy was 8 cm.
In the postoperative follow-up, 33 to 38 carious teeth with periodontal and periapical disease, which caused pain and recurrent local infections, were exodonticated. After an asymptomatic period of 8 months, the patient consulted for a fistulised inflammatory episode in the left hemimandible, which radiologically corresponded to ORN of the left mandibular body.

After attempts at conservative treatment of the new condition, the symptoms persisted and the poor evolution of the disease led to a second operation with a left mandibulectomy and a second microvascularised fibula with a cutaneous island.

In the early evolution the patient developed a midline fistula, which was resolved by removing the osteosynthesis plate that joined the anterior end of the transplanted first fibula with the right parasymphysis region.
The final evolution of the disease has been satisfactory, with adequate intra- and extraoral healing and resolution to date.

