Age / Sex : 76 / M

Heterotopic ossification of abdominal scar

Discussion

Findings:

Vertically oriented, mineralized mass in the incision scar on the anterior abdominal wall

Irregular-shaped ossification consisting of cortical and medullary components of mature bone

Diagnosis: Heterotopic ossification

Discussion:

Heterotopic ossification of abdominal scars represents a subtype of myositis ossificans traumatica in which osseous, cartilaginous, and, occasionally, myelogenous elements form within a surgical incision. Grossly, the scar ossification resembles that of rib. Histologically, the ossified scars are composed of mature bone with marrow and cartilaginous elements surrounded by fibrous tissue.

Although the etiology of heterotopic scar ossification is uncertain, possible causes include (1) metaplasia of multipotent, undifferentiated, embryonic connective tissue cells secondary to trauma; (2) excessive suture line tension (which may lead to intramuscular implantation and ossification of periosteal particles torn from sites of muscular insertion into bone), with or without associated fascial margin necrosis; and (3) intraoperative seeding of perichondrial cells from the xiphoid

In one study, heterotopic ossifications were identified in 39 (25.7%) of 152 consecutive patients who underwent abdominal incisions. CT and MR imaging show ossified surgical scars, with the attenuation or signal intensity of the ossified components equivalent to that of bone. Intralesional, fat-density components suggestive of marrow can be seen in mature lesions of heterotopic ossification.

References:

1. Jacobs JE, Birnbaum BA, Siegelman ES. Heterotopic ossification of midline abdominal incisions: CT and MR imaging findings. AJR 1996;166:579-584


2. Gurzu S, Bara T, Bara T Jr, Jung I. Metaplastic bone formation in the abdominal wall--an incidental finding in a patient with gastric cancer. Case report and hypothesis about its histogenesis. Am J Dermatopathol 2013;35:844-846


3. Kim J, Kim Y, Jeong WK, Song SY, Cho OK. Heterotopic ossification developing in surgical incisions of the abdomen: analysis of its incidence and possible factors associated with its development. J Comput Assist Tomogr 2008;32:872-876