Imaging-guided percutaneous cryotherapy of bone and soft-tissue tumors: what is the impact on the muscles around the ablation site?

OBJECTIVE: The objectives of our study were to evaluate the incidence of muscular injury after cryoablation of bone and soft-tissue tumors, to relate MRI findings to the size of the intramuscular ice ball, and to determine the clinical significance of postcryotherapy myositis.
MATERIALS AND METHODS: Between January 2010 and October 2012, 24 bone and soft-tissue lesions (16 pelvic lesions, three shoulder lesions, and five paravertebral lesions) in 21 patients treated by imaging-guided percutaneous cryoablation and followed up with MRI were retrospectively analyzed. Muscular hyperintensity on T2 STIR images was graded as follows: grade 0, no myositis; grade 1, local myositis; grade 2, myositis in less than half of the volume of the muscle; or grade 3, myositis in half of the volume of the muscle or more. The presence of T2 STIR hyperintensity in the muscles surrounding the cryoablation site was correlated with the volume of the intramuscular ice ball.
RESULTS: Muscular T2 STIR hyperintensity was observed in 87.5% of cases (grade 0 in 12.5%, grade 1 in 45.8%, grade 2 in 20.8%, and grade 3 in 20.8%). The volume of the intramuscular ice ball and grade of myositis (mean volume: grade 0, 2.8 cm(3); grade 1, 9.2 cm(3); grade 2, 17.1 cm(3); grade 3, 42.9 cm(3)) were positively correlated in the 24 lesions in the study cohort (r = 0.64, p < 0.001). Only two cases of myositis (grade 3) were symptomatic, and antiinflammatory drugs promoted pain resolution in both cases.
CONCLUSION: Muscular injury around the cryoablation site is commonly observed and is correlated with the volume of the ice ball. When muscular injury around the cryoablation site causes pain, the symptoms differ from the initial tumoral pain and can be treated with antiinflammatory drugs.