Percutaneous core excision and radiofrequency thermo-coagulation for the ablation of osteoid osteoma of the spine

Abstract

Percutaneous radiofrequency ablation is the treatment of choice for osteoid osteoma of the appendicular skeleton. However, difficulties in localizing the lesion in the spine and its proximity to neural elements have yet to make it the prevalent treatment for spine. This study assesses the safety and effectiveness of two percutaneous techniques for ablating osteoid osteoma of the spine. Seven patients were treated between 1998 and 2005. Four patients underwent percutaneous radiofrequency coagulation. The lesions were located at the articular processes of L3 and L4, the lamina of L3 and in the head of the 11th rib. Three patients with lesions in close proximity to neural structures (pedicle of T9, the posterolateral inferior aspect of L3 vertebral body and the inferior articular process of C5) were subjected to percutaneous core excision. Mean follow-up was 4.2 +/- 1.6 years. Three out of four patients who underwent radiofrequency ablation had an immediate and sustained response. One patient with a lesion in the head of the rib failed to respond. The three patients in the group of pecutaneous core excisional biopsy demonstrated immediate relief of pain. However, one patient experienced relapse of symptoms 6 months after transpedicular core excision. CT scan suggested partial targeting of the lesion that corroborated with histologic examination revealing only reactive tissue. Subsequent percutaneous core excision was successful. Therefore, the overall success rate was 85.7%. Mean VAS improved dramatically from 9 +/- 1 to 2 +/- 1 after surgery (P < 0.05). No neurological or other complications were encountered. This study indicates that radiofrequency ablation of spinal osteoid osteomas is safe and reasonably effective when an intact cortical shell separates the nidus from the neural elements. Percutaneous core excision can obviate the risk of thermal damage for lesions located in close proximity to the neural elements. Effectiveness of treatment can also be evaluated by CT scan and histological examination. Difficulties in targeting the nidus can lead to treatment failure. The minimal morbidity and the effectiveness of these minimally invasive procedures make them a valid alternative in the treatment of spinal osteoid osteoma.

Fig. 1

Axial 1 mm CT scan depicting the typical nidus of an osteoid osteoma at the head of the left 11th rib

Fig. 2

a Axial CT scan depicting the nidus of an osteoid osteoma at the posterolateral inferior portion of L3 vertebral body, close to the adjacent disc. The lesion is in close proximity to the exiting nerve root and inaccessible by transpedicular approach. b Fluoroscopic image depicting percutaneous posterolateral core excisional biopsy under local anesthesia

Fig. 3

a Axial CT depicting a nidus at the inferior articular process of C5. b lateral reformatted image showing the proximity of the lesion to the neural foramen. c Postoperative axial CT scan image demonstrating the tract made by the biopsy tool used to core out the lesion. At 6 months follow-up there is evidence of sclerosis and partial filling in of excised lesion

Fig. 4

Lateral fluoroscopic image depicting the biopsy instrument at the pedicle of T9