The healing pattern of osteoid osteomas on computed tomography and magnetic resonance imaging after thermocoagulation

Abstract

Objective To compare the healing pattern of osteoid osteomas on computed tomography (CT) and magnetic resonance imaging (MRI) after successful and unsuccessful thermocoagulation. Materials and methods Eighty-six patients were examined by CT and 18 patients by dynamic gadolinium-enhanced MRI before and after thermocoagulation for osteoid osteoma. Thermocoagulation was successful in 73% (63/86) and unsuccessful in 27% (23/86) of patients followed by CT. Thermocoagulation was successful in 72% (13/18) of patients followed by MRI. After treatment, the healing of the nidus on CT was evaluated using different healing patterns (complete ossification, minimal nidus rest, decreased size, unchanged size or thermonecrosis). On MRI the presence of reactive changes (joint effusion, "oedema-like" changes of bone marrow and soft tissue oedema) and the delay time (between arterial and nidus enhancement) were assessed and compared before and after thermocoagulation. Results Complete ossification or a minimal nidus rest was observed on CT in 58% (16/28) of treatment successes (with > 12 months follow-up), but not in treatment failures. "Oedema-like" changes of bone marrow and/or soft tissue oedema were seen on MR in all patients before thermocoagulation and in all treatment failures. However, residual "oedema-like" changes of bone marrow were also found in 69% (9/13) of treatment successes. An increased delay time was observed in 62% (8/13) of treatment successes and in 1/5 of treatment failures. Conclusion Complete, or almost complete, ossification of the treated nidus on CT correlated with successful treatment. Absence of this ossification pattern, however, did not correlate with treatment failure. CT could not be used to identify the activity of the nidus following treatment. The value of MR parameters to assess residual activity of the nidus was limited in this study.

CT-guided radiofrequency ablation of osteoid osteoma: correlation of clinical outcome and imaging features

“…Thus, neither pre-or postprocedural nidus size nor location or nidus morphology should influence the therapy decision-making or be used as an outcome predictor. This result is supported by the data of Vanderschueren et al (37), who found that the nidus size was not correlated with unsuccessful coagulation. PostRFA MRI changes that are supposed to indicate healing (decrease in contrast enhancement, diminished/ vanished edema) were accompanied by a marked reduction in the VAS pain score.…”

“…To prove this hypothesis, a prospective study with a quantitative assessment of the enhancement and the inclusion of relapsed patients would be desirable. However, our findings show that even a persistence of those signs of potential activity (edema, contrast enhancement) are not necessarily correlated with the clinical symptoms, thus supporting the previous findings of Vanderschueren et al (37), who described a persistent "edema-like" pattern in 5/5 unsuccessfully treated patients and also in 9/13 successfully treated patients.…”

“…These results also support the previous findings of Barei et al (36), who investigated similar items in a small series of patients. Our relatively uniform CT and preprocedural MRI patterns were in agreement with the literature (16,(37)(38)(39)(40)(41)(42), but the follow-up (mean, 3.4±2.2 months) MRI varied considerably. In Figure 4.…”

Combined dynamic contrast-enhancement and serial 3D-subtraction analysis in magnetic resonance imaging of osteoid osteomas

“…3). Brodie's abscess may be morphologically indistinguishable from a nidus in MR [8] as well as in CT images [5,6,16,18,19]. In our experience, the contrast enhancement in chronic osteomyelitis increases more gradually than in osteoid osteomas and shows no clear-cut decrease (wash-out effect) in the late phase.…”

“…As open surgery has been increasingly replaced by minimally invasive procedures and as the lesion may also be treated with prostaglandin E2 inhibitors, a histological confirmation is usually not obtained. Therefore, diagnosis depends entirely on radiological imaging [3][4][5][6].…”