The Cool-tip RF Tissue Ablation System is designed to allow treatment of a range of RFA suitable conditions. This review is restricted to its use in the treatment of osteoid osteoma and only needles suitable for this indication will be discussed. The needle consists of a diamond tipped shaft and a plastic handle through which an RF electrical lead and a twin bore perfusion channel both enter the needle. The perfusion channel is not used in osteoid osteoma treatment unless increased tissue impedance becomes problematic. Needles are available with various lengths of exposed RF tips, the remainder of the shaft being insulated. Tip lengths may be 0.7cm, 1.0cm, 2.0cm or 3.0cm. Various needle lengths are also available (10cm, 15cm, 20cm) although the 0.7cm and 1.0cm tip lengths are only available in the 15cm needle size, and this combination is almost always the most suitable choice for ablation of a standard osteoid osteoma. All needles are 17 gauge (1.5mm, 4.5F).
The needle is not designed for primary introduction into bone and the electrical elements would be damaged if forced through a hard surface. It there requires a separate bone needle to allow access to the nidus. The Cool-tip needle is entirely compatible with the Bonopty bone biopsy system (see review of this product) and may be introduced in a co-axial fashion once the osteoid osteoma nidus have been entered by the Bonopty drill or biopsy needle.
Each Cool-tip needle comes with the connection leads, two disposable grounding pads and perfusion tubing. The RF generator must be purchased or rented separately.
Combined with the Bonopty system to access the nidus, the Cool-tip needle works splendidly and is easy to introduce. A little resistance is sometimes encountered as the tip passes beyond the outer Bonopty needle and/or into the nidus if the Bonopty needle terminates proximal to the lesion. If this is not passed readily, it is worth re-inserting the Bonopty drill to clear any remaining debris to avoid damage to the Cool-tip. When treating a small nidus, drilling 2-3mm beyond the nidus allows the Cool-tip to be sited straddling the lesion ensuring the treatment field is centred on the nidus rather than eccentrically at its tip. Such eccentric positioning may occasionally be desirable for superficial lesions to minimize thermal damage to periosteum and overlying soft tissues.
Prior to commencing ablation, it is imperative to withdraw the Bonopty needle over the shaft of the Cool-tip until the tip of the Bonopty is no longer in contact with the conducting end of the Cool-tip and now covers only the insulated part of the shaft. Failure to perform this action converts the entire Bonopty needle into a conducting RF device and will cause thermal injury along the entire needle track.
Treatment is rapid, requiring 6 minutes at 90 degrees centigrade.
In our current series of 21 extremity cases, we have had considerable technical success with complete pain relief in all patients.
An excellent RFA needle for treatment of osteoid osteomas.
No Conflict
Dr Geoff Hide
Consultant Musculoskeletal Radiologist
Freeman Hospital
Newcastle upon Tyne, UK
