Thermoablation (RFA)
The osteoid osteoma is a primary bone tumour and its symptoms are characteristic: pain at night which can typically be relieved rapidly by taking non-steroidal anti-inflammatory medications such as aspirin. The tumours are usually located in the long hollow bones of the legs, and less frequently in the arm bones or the spine.
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Thermoablation of benign bone tumour in childhood (osteoid osteoma / OO)
Osteoid osteomas are benign, i.e. they demonstrate no inclination to form sister growths or metastases. However the pain for the usually young patients is very burdensome and can lead to misalignment and inappropriate mechanical stress and consequent joint wear.
In the past, these patients often had to undergo extensive surgical intervention. For around 15 years, it has been possible to remove these tumours with heat. This method, known as "thermoablation" is now regarded as the standard treatment for osteoid osteoma.
(The term "ablation" actually means removal of release of tissue, however it is also used in (tumour) cell inactivation through radiogenic, thermal, electrical, biomechanical or chemical effects).
How does thermoablation work?
With this method, the cells of the osteoid osteoma are destroyed by heating them to around 60°C to 90°C, especially the cells producing prostaglandin (pain substance) in the centre (nidus) of the osteoid osteoma and the pain conduction pathways. The intention is to completely inactivate all of the cells in the ablation area (a scar develops).
The heat can be delivered to the diseased tissue minimally invasively either through radio-frequency (RFA) or laser (LA). Of all the thermal ablation methods, RFA is the most commonly used and the method that has undergone the most scientific research.
How is thermoablation carried out?
Beforehand
Generally speaking, the diagnosis is made using a conventional X-ray since it provides excellent information regarding the location and nature of the bone tumour.
If there are still any uncertainties, further investigation can be carried out with magnetic resonance imaging (MRI) or computed tomography (CT).
During
The treatment is carried out during an admission to our treatment ward 6.
Treatment is carried out under general anaesthetic, since drilling into and heating the osteoid osteoma can be very painful for the patient.
For radio-frequency ablation, a special probe is inserted into the tissue to be treated. This is generally done under CT guidance in order to ensure precise localisation of the probe in the tumour. An alternating current field at the tip of the probe heats up the tissue to the target temperature.
During laser ablation, laser energy is applied via a fibre-optic cable into the central nidus (growth core) of the osteoid osteoma. The absorption of photos (“light particles”) in the tumour tissue causes it to heat up and therefore causes thermal ablation.
After
Pain relief in the treated area occurs quickly after successful ablation in the first few days. Apart from with very specialist localisations – which we would discuss with you – you can usually also weight-bear on the region without restrictions. In most cases there is just a little subjective, limiting wound pain, although the access wound is generally very small due to the small material used.
Permanent pain relief or cure can be achieved after the first ablation in 90 per cent of patients, while the other ten per cent experience residual pain or the pain recurs, requiring further thermal ablation.
(The success (= freedom from pain) of thermal ablation is around the same for laser and radio-frequency methods).
Case example
A 7-year-old boy with severe night pain in the right shin. On the first conventional X-rays carried out there is significant swelling of the outermost bony layer of the tibia (tibia corticalis) evident in the middle third, and a typical radio-transparent tumour core (nidus) within this swelling is clearly recognisable (Figure 2). The CT scan carried out subsequently confirmed the suspicion of an osteoid osteoma with typical nidus (Figure 3A).
The patient presented to us for thermoablation of the symptomatic, i.e. painful osteoid osteoma. Under general anaesthetic, the core of the tumour (nidus) was drilled into using a bone drill. A thermoablation probe was then inserted into the nidus (Figures 3B and 3C). This thermoablation procedure took around ten minutes. The MRI image immediately after the procedure shows the ablation area with no residual tumour (Figure 3D).
In this case, successful treatment of the osteoid osteoma was carried out with complete and permanent pain relief.