PERCUTANEOUS RADIO-FREQUENCY (RF) THERMAL ABLATION OF OSTEOID OSTEOMAS

Souftas VD1, Hantzidis P2, Filippidis A1, Atsalou Μ3, Panidis G2, Tsitouridis I1

Radiology1/Orthopaedics2/Anaesthesiology3 Departments, General Hospital «Papageorgiou», Thessaloniki, Greece

SUMMARY

Osteoid osteoma is a small painful benign osteogenic tumor most frequently observed in the first 3 decades of life. Treatment of choice used to be complete surgical excision.

We treated percutaneously a female 19 years old for an osteoid osteoma in the inner aspect of the right humeral anatomical neck, by using RF thermal ablation, under Computed Tomographic (CT) guidance.

We present the case and review the literature.

Index terms: Bone neoplasms, therapy; CT-guidance; RF ablation; Osteoid osteoma.

INTRODUCTION

The osteoid osteoma is a relatively common small benign osteoblastic bony neoplasm (10% of benign bone tumors), slow-growing, round or oval, that radiologicaly is characterized by a central region of translucency of up to 30 mm (the so called “nidus”) and a prominent perifocal sclerotic zone. The lesion can provoke severe pain, related to prostagladin production within the cells of the nidus, mostly at night, which may be controlled by analgesics (aspirin). Other possible symptoms include growth disturbances, bone deformity, painful scoliosis, and, if located within (or close to) a joint capsule, joint swelling, synovitis, restricted joint or limp motion, and contracture1-3.

Pain can subside after several years of conservative treatment4. However, the common curative treatment of osteoid osteoma is en bloc surgical excision of the nidus. Surgical removal of the tumor often necessitates significant bone resection, internal fixation and/or bone grafting. In small percentage of cases, the nidus may be missed even in surgery4.

In recent years, several CT-guided percutaneous techniques have been employed to achieve removal or destruction of the nidus with minimal invasiveness, including percutaneous drill resection (with or without ethanol injection), and thermal destruction (laser photoagulation or RF ablation) 2-5.

RF ablation of osteoid osteoma is a promising technique of interventional radiology, very simple to be performed, minimally invasive, safe and highly effective for treatment of osteoid osteoma.

CASE PRESENTATION

19 year old woman with severe pain and restriction of movement of her right shoulder for 2 years. Administration of large doses of NSAD had no effect, while local injections of steroids along with xylocain provided relief of pain for 24 hours.

The diagnosis of osteoid osteoma of the upper epiphysis of the humerous was made after radiological and CT-scan of the shoulder.

We performed percutaneous RF thermal ablation, under CT guidance. The procedure was performed under local anaesthesia with continuous monitoring of vital signs. For the RF ablation we used the volumetric system RITA-1500 (RITA Medical Inc., USA), a 14 F bone biopsy needle (trocar), and a 5 prong electrode. We opened the electrode prongs to cover a global area of 15 mm in diameter, and conducted the system at a mean temperature of 100ο C for 10 min.

The patient experienced tolerable pain during the operation and mild-burning sensation for 12 hours postoperatively. After 18 hours there was no discomfort at all with full range of movement of the upper limp.

Hospitalization was for 1 day.

Two months after the operation she is doing very well, without the slightest disturbance in her right shoulder.

DISCUSSION

The first report in the literature of technical and clinical success with RF thermal ablation in the treatment of osteoid osteoma by Rosenthal et al. 5 appeared in 1992.

RF thermal ablation is a form of electrosurgery in which an alternating current of high –frequency radio waves (>10 KHz) passes from an electrode tip in the body tissue and dissipates its energy as heat. A radiofrequency generator forms an electric current that flows from the generator through the electrode into the patient, and out through a grounding electrode or pad to the generator. Resistance of biologic structures causes local ions to vibrate. This ionic agitation results in friction around the electrode tip as ions attempt to pursue changes in direction of the alternating current and create heat to the point of desiccation-hence, the term “thermal ablation” 2. RF thermal ablation differs from electrocautery in that the tissue around the electrode, rather than electrode itself, is the primary source of heat2.

CT guidance affords the best available visualization of needle and probe placement in the lesion nidus2,4,6,7.

A general anesthetic allows a pain-free procedure and absolutely stable patient position, although a spinal anesthetic is an option for patients with lower limb lesions. Stem anesthesia is another helpful option. Local anesthetic proved unsuccessful because of inadequate pain control, in spite of adequate anesthetic infiltration in soft tissue and overlying periosteum. Entering the nidus itself elicits extreme pain, in most cases resulting in patient movement and loss of position2,4.

Althought this technique is minimally invasive, potential complications that may occur during needle passage include bleeding and nerve injury. These can be avoided by knowledge of anatomic structures in the region of needle and an alteration in the approach neurovascular bundles2,4,6.

Thermal RF ablation of osteoid osteoma requires creation of only a small osseous access to the nidus to allow insertion of the electrode. Loss of bone substance is therefore minimal and does not result in significant structural weakening. For this reason, patients are encouraged to return to normal activity immediately and sports activity is not restricted2,4. There is a risk of skin necrosis in osteoid osteomas in superficially located bone, in which extra care is required3. No other significant complications have been reported in the literature2-8. Burns of soft tissues close to the intervention site and ground-pad skin burns, described in cases of RF thermal ablation procedures in other organs, such as liver9. Elevation of cardiac and respiratory rates at biopsy needle entry into the nidus were also observed10.

The curative treatment of osteoid osteomas by this method after one session has been reported to have a success rate of 76%3-96%2,4-7, and after a second session a rate of 92%3-100%2,4-7.

The main disadvantage in patients with suspected osteoid osteoma is the limited possibility of histological verification. Although biopsy (aspiration of the nidus) can easily be accomplished during the initial puncture, this is not routinely able, for various reasons2-4,7.

In conclusion, percutaneous RF thermal ablation for the treatment of osteoid osteomas is a simple, safe and effective minimally invasive interventional radiologic procedure, alternative to the surgical resection. It needs very short hospitalization time and has a very low cost. The method is better to be performed under general, epidural or stem anesthesia.

REFERENCES

  1. Adler C-P (2000) Bone diseases. Springer-Verlag, Berlin, pp 260-263.
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