Purpose: To assess the MDCT features of bone lesions that mimic
osteoid osteoma (OO-like lesions) and evaluate their treatment by
radiofrequency (RF) ablation.
Methods and materials: All percutaneous RF ablations performed
between May 2002 and June 2009 for a presumed (clinical and MDCT
features) diagnosis of OO were retrospectively reviewed. Per-procedural
biopsies were always performed and histopathological diagnoses were
noted. The following MDCT features of all bone lesions were assessed
by two musculoskeletal radiologists in consensus: skeletal distribution
and location within the bone, size, central calcification, surrounding
osteosclerosis and periosteal reaction. Clinical success was also
evaluated.
Results: Eighty patients (54 males, 26 females, mean age 24.1 years,
range 5-48) underwent RF ablation. The histopathological diagnoses
were: 54 non-contributory biopsies, 16 OO, 10 OO-like lesions
(5 chronic osteomyelitis, 3 chondroblastoma, 1 eosinophilic granuloma,
1 fibrous dysplasia). The OO-like lesions were significantly greater in
size (p = 0.001) and exhibited trends toward medullary location within
the bone, moderate surrounding osteosclerosis and less periosteal
reaction, compared to OO. Primary clinical success for OO-like lesions
was 100% at 1 month, 85.7% at 6 and 12 months, and 66.7% at
24 months. Secondary success was 100%.
Conclusion: Greater size, medullary location within the bone, lesser
surrounding osteosclerosis and periosteal reaction on MDCT may help
differentiate OO-like lesions from OO. OO-like lesions are safely and
successfully treated by RF ablation.