Management of Osteoblastoma and Giant Osteoid Osteoma with Percutaneous Thermoablation Techniques

Abstract

Osteoblastoma (OB) is a rare, benign bone tumor, accounting for 1% of all primary bone tumors, which occurs usually in childhood and adolescence. OB is histologically and clinically similar to osteoid osteoma (OO), but it differs in size. It is biologically more aggressive and can infiltrate extraskeletal tissues. Therapy is required because of severe bone pain worsening at night. Moreover, non-steroid anti-inflammatory drugs (NSAIDs) are not a reasonable long-term treatment option in young patients. Surgical excision, considered the gold standard in the past, is no longer attractive today due to its invasiveness and the difficulty in performing a complete resection. The treatment of choice is currently represented by percutaneous thermoablation techniques. Among these, Radiofrequency ablation (RFA) is considered the gold standard treatment, even when the lesions are located in the spine. RFA is a widely available technique that has shown high efficacy and low complication rates in many studies. Other percutaneous thermoablation techniques have been used for the treatment of OB, including Cryoablation (CA) and laser-ablation (LA) with high success rates and low complications. Nevertheless, their role is limited, and further studies are necessary.

Keywords: Osteoblastoma (OB); musculo-skeletal interventional radiology; thermoablation techniques.

Figure 1

(a) Axial-CT images of intra-articular OB localized at the humeral epicondylus. The “nidus” has a rounded shape and well defined tumor margins, with high degree of internal calcifications; no presence of perilesional sclerosis. (b) Sagittal-CT images of OB localized at the femoral neck, with expansive aspect: the “nidus” is entirely radiolucent, with no sclerosis and small radio-opacities; the bone cortex is perfectly intact, although expanded and thinned.

Figure 2

Radiofrequency-ablation (RFA) of a vertebral Osteoblastoma (OB). (a) Axial-CT image of OB located in the transverse process of a lumbar vertebra, near the spinal root. (b) Axial-CT image during the treatment: under CT-guidance, an RF probe with an exposed tip is perfectly located into the nidus; it is possible to achieve the complete and radical ablation of the lesion. A safety distance of about 1cm is ensured, between the exposed tip and the adjacent critical anatomical structures.

Figure 3

Tibial OB treated with MRgFUS was successful thanks to the presence of an adequate acoustic window and the superficial position of the lesion. Specific MR-sequences, acquired during the treatment, provided real-time thermometric maps of the region of interest to avoid thermal damage of the surrounding tissues.