This study describes a new way of treating benign and painful bone lesions.
The clinical results depend on patient selection: MRgFUS,
in fact,
has an important limit,
being a technique that destroys target tissue through heat generated by a high intensity focused ultrasound beam.
The penetration of the US beam in the body,
and in the lesion,
depends on the type of tissue traversed: in absence of reflection or refraction of the US beam,
the whole energy reaches the target lesion,
but if the US beam meets structures that reflect or refract the beam (i.e.
bone,
calcifications,
metal devices),
or sensitive structures that are close to the target lesion (i.e.
tendons,
ligaments or nerves),
and risk to be damaged,
the treatment can fail.
In our study,
all patients affected by osteoid osteomas who underwent the treatment had a very good acoustic window (region through which passes the US beam) and showed a good response in terms of function improvement and pain relief; moreover,
on the basis of our experience,
we can say that very low levels of energy are needed to treat these lesions (500-600J,
at maximum 800J).
Also the patients with the other types of lesions had a good acoustic window,
with two exceptions represented by one case of chondroblastoma,
where an insufficient acoustic window caused by the presence of the cortical bone allowed treatment of about 80% of the lesion (the clinical results were however good),
and one case of periosteal chondroma,
where the presence of calcification on the surface of the lesion did not permit to treat it successfully.
In all these lesions the number of sonications used depended mainly on their size,
whereas the energy employed depended mainly on their matrix,
whether it was liquid,
myxoid or mixed.
Therefore,
the level of energy employed has to be decided during the treatment.
In conclusion,
though the need of further and larger studies,
in our experience the use of MRgFUS in case of surgically untreatable lesions has proved to be a safe and effective treatment.