LAUSR

PURPOSE To examine the diagnostic yield of intraprocedural percutaneous biopsy performed at the time of radiofrequency ablation of suspected Osteoid Osteoma (OO) and identify technical and nidus-specific factors associated with diagnostic adequacy. MATERIALS AND METHODS Following IRB approval, a total of 42 patients (male: 28, female: 14; mean age: 29 years) who underwent intraprocedural biopsy immediately prior to RFA between June 2010 and June 2017 were retrospectively identified. The nidi were located in various locations. The nidi had a mean size of 6.3 mm (range: 3-11 mm, Standard deviation (SD): 2.26). Core biopsies were performed by one of 15 operators. Biopsies were performed with two needle types ranging from 11-G to 15-G with a mean number of samples of 1.8 (range: 1-5, SD: 1.01). Electronic records and imaging were reviewed for demographics, nidus characteristics, biopsy details and diagnostic yield. Multivariate logistic regression of nidus-specific and biopsy-specific factors was performed. RESULTS A total of 22/42 (52.3%) of the biopsies were adequate for histological diagnosis of OO. For the two experienced operators, the diagnostic yield was 67% (6/9) and 80% (8/10). Biopsy adequacy was significantly correlated with presence of an osteoid matrix (p = 0.03), obtaining >1 core sample (p = 0.03), the needle track passing through the nidus (p = 0.0003) and thinner (2.5 mm) intraprocedural CT slices (p = 0.03). On multivariate analysis, use of thinner intraprocedural CT slices was found to be associated with adequate biopsy (p = 0.02). CONCLUSION Intraprocedural percutaneous biopsy samples of nidi highly-suspected to be OO at the time of RFA were diagnostic in 52% of patients. Multivariate analysis shows thinner intraprocedural CT slices to be a significantly associated with biopsy adequacy.