Usefulness of Bone Scan in Heterotopic Ossification

Received 11/3/2004; revised 2/20/2005; accepted 3/5/2005. For correspondence or reprints contact: Bi-Fang Lee, M.D., Department of Nuclear Medicine, National Cheng Kung University Hospital, 138 Sheng-Li Road, Tainan 704, Taiwan. Tel: (886)6-2353535 ext. 2483, Fax: (886)6-2766609, E-mail: [email protected] Backgrounds: Heterotopic ossification (HO) is the abnormal development of bone tissue within soft tissue. Its etiology and pathology are uncertain. HO is seen most frequently with musculoskeletal trauma, spinal cord or CNS injury. Complications like loss of joint mobility or joint ankylosis may threaten function and make care of paraplegic patients difficult. The differential diagnosis of HO from cellulitis, osteomyelitis, thrombophlebitis or bone-forming tumor is crucial in its early stage. To explore the utility of bone scan for HO and its correlation with clinical findings we conducted the study. Methods: We retrospectively reviewed patients referred to our department for bone scans from April 1997 to August 2003. Clinical records, including clinical course, laboratory and imaging findings, were documented for those with scintigraphic diagnosis of HO. Results: Ten patients were proved to have HO by bone scans, other subsequent imaging studies and clinical course. Bone scans confirmed the diagnosis of HO in 5 clinically suspected patients, found HO was unexpectedly in 3 patients and changed the clinical diagnosis in 2 patients (1 clinically suspected of osteomyelitis, 1 clinically suspected of bone tumor). Totally twenty HO lesions were detected in the 10 patients. Their distributions were 9 in hip, 8 in thigh, 3 in pelvic cavity. Two patients had additional gallium scans which showed parallel findings to the findings of bone scans. The interval between the known initial event and scintigraphic diagnosis of HO was 1 month to 19 years (The median interval is was 7.5 months). Conclusion: Bone scan plays an important role in the early detection of HO formation, especially for those with clinical manifestations mimicking other diseases (such as osteomyelitis), or not evident (such as in patients with impaired sensation).