Heterotopic ossification of midline abdominal incisions: CT and MR imaging findings.

OBJECTIVE: Heterotopic ossification of a midline surgical incision in a form of myositis ossificans traumatica in which osseous, cartilaginous, and, occasionally, myelogenous elements develop within an abdominal wound. When large amounts of internal ossification are present, the scar may demonstrate a complex radiologic appearance and potentially may be misinterpreted as a retained foreign body or incisional neoplastic recurrence. This report describes the CT and MR imaging findings of this entity.

SUBJECTS AND METHODS: The authors retrospectively reviewed the cross-sectional imaging findings of 11 patients with ossified midline 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). Initial imaging was performed 7 days to 36 months after surgery (mean, 6.7 months). CT and MR imaging scans were reviewed, and lesion size, location, distance from the xiphoid, shape, and stability were assessed. Pathologic proof was obtained in one patient.

RESULTS: CT and MR imaging examination in all patients showed ossified surgical scars, with the attenuation or signal intensity of the ossified components equivalent to that of the spine. Intralesional, fat-density components suggestive of marrow were present in two patients. All scars were located in the upper abdomen between the anterior abdominal fascia and the peritoneal surface, at the level of or inferior to the xiphoid process. Scars 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 location of subsequent scar ossification. Of the nine patients with multiple postoperative examinations, scar size and appearance remained stable in six. In the remaining three patients, scar size was stable but showed progressive internal ossification.

CONCLUSION: Heterotopic ossification within midline abdominal scars can be diagnosed by both CT and MR imaging examination. Recognition of the imaging appearances of such ossification should help prevent diagnostic confusion when attending postoperative patients.