HETEROTOPIC OSSIFICATION OF MIDLINE ABDOMINAL INCISIONS - CT AND MR-IMAGING FINDINGS

OBJECTIVE. Heterotopic ossification of a midline surgical incision is a form of myositis ossificans traumatica in which osseous, cartilagino us, and, occasionally, myelogenous elements develop within an abdomina l wound. When large amounts of internal ossification are present, the scar may demonstrate a complex radiologic appearance and potentially m ay be misinterpreted as a retained foreign body or incisional neoplast ic recurrence. This report describes the CT and MR imaging findings of this entity. SUBJECTS AND METHODS. The authors retrospectively review ed the cross-sectional imaging findings of 11 patients with ossified m idline abdominal wounds. All but one of the patients were men, and the median age at diagnosis was 40 years old (range, 20-76 years old). In itial imaging was performed 7 days to 36 months after surgery (mean, 6 .7 months). CT and MR imaging scans were reviewed, and lesion size, lo cation, distance from the xiphoid, shape, and stability were assessed. Pathologic proof was obtained in one patient. RESULTS. CT and MR imag ing examination in all patients showed ossified surgical scars, with t he attenuation or signal intensity of the ossified components equivale nt to that of the spine. Intralesional, fat-density components suggest ive of marrow were present in two patients. Ail scars were located in the upper abdomen between the anterior abdominal fascia and the perito neal surface, at the level of or inferior to the xiphoid process. Scar s ranged in length from 0.7 to 13.4 cm (mean, 6.9 cm). Distances from the inferior tip of the xiphoid to the superior aspect of the ossified scar ranged from 0 to 4.9 cm (mean, 2.2 cm). Time from surgery to the initial postoperative demonstration of scar ossification ranged from 11 days to 36 months (mean, 6.8 months). None of the five patients who underwent preoperative CT examinations had abnormalities in the locat ion of subsequent scar ossification. Of the nine patients with multipl e postoperative examinations, scar size and appearance remained stable in six. In the remaining three patients, scar size was stable but sho wed progressive internal ossification. CONCLUSION. Heterotopic ossific ation within midline abdominal scars can be diagnosed by both CT and M R imaging examination. Recognition of the imaging appearances of such ossification should help prevent diagnostic confusion when attending p ostoperative patients.