Clinical characteristics and role of whole-body bone scan in multifocal osteonecrosis

BACKGROUND: Multifocal osteonecrosis (ON) is defined as ON involving three or more distinct anatomical sites. We investigated the clinical characteristics and utility of whole-body bone scans (WBBS) in patients with multifocal ON. METHODS: A total of 254 patients with ON confirmed by magnetic resonance imaging (MRI) or X-rays of the hips or other anatomic regions were evaluated using WBBS and divided into those with multifocal disease and those with oligofocal disease; their clinical characteristics were then compared. All data were analyzed retrospectively both visually and quantitatively (via uptake grading and defect scoring). Associations between the MRI Association Research Circulation Osseous (ARCO) classification and bone scan photon defects and uptake grade were assessed. Factors associated with multifocal ON were identified using logistic regression. RESULTS: Of the 254 ON patients, 26 (10.2%) had multifocal ON. Their mean age (42.8 ± 14.3 years) was less than that of patients with oligofocal ON (50.9 ± 15.4 years; p = 0.011). Comorbidities, corticosteroid use, and treatment with immunosuppressive agents were more frequent in patients with multifocal ON. Age (odds ratio [OR] = 0.964, p = 0.013), the presence of a comorbidity (OR = 3.387, p = 0.006), present corticosteroid use (OR = 5.696, p < 0.001), and treatment with immunosuppressive agents (OR = 3.447, p = 0.004) were significantly associated with multifocal ON. The MRI ARCO classification was not associated with photon defects in the bone scans of those with femoral ON. However, the ARCO classification was significantly associated with uptake grade. CONCLUSIONS: WBBS may be an additional tool for evaluating ON patients with risk factors for multiple ON, such as younger age, corticosteroid use, and comorbidities.