posttraumatische zystische Knochenläsion

Post-traumatic cystic bone lesions, also known as fracture cysts, are benign, transient post-fracture cysts, which are relatively uncommon and usually appear about one-to-two months after traumatic fracture.

Epidemiology

They are rare but may be under recognized, as monitoring after fracture often is only clinically. They have most often been reported in children of growing age. The most common reported site is the distal radius .

Clinical presentation

Though mostly asymptomatic in nature, patients with these transient lesions can present with moderate soft swelling .

Pathology

Characteristics of these lesions are:

  • non-expansile cyst of <1 cm in diameter
  • may be multiple
  • close proximity to former fracture site

Typically encountered at about a month after initial fracture, they have been reported to occur as late as 18 months after the initial trauma .

Etiology

There is ongoing debate whether these transient lesions represent intramedullary fat inclusions cysts (most accepted theory) or resorption cysts of excessive periosteal reaction caused by subperiosteal hematoma or intraosseous hemorrhage .

Radiographic appearance

Plain radiograph

Typical appearances are that of a subcentimeter oval or round lucency without expansivity, peripheral condensation or periosteal reaction and close proximity to the site of former fracture.

Treatment and prognosis

As all hitherto reported lesions resolved spontaneously, no treatment is needed.

Differential diagnosis

Encountering a cyst-like lesion close to a healing fracture (probably even greenstick fracture) can make the diagnosis straightforward. More challenging diagnostic scenarios, however, can comprise lack of former studies (or unawareness of their existence, unavailability at other institutions, etc), incomplete clinical information or a long period between initial fracture and lesion on actual imaging studies.

In those cases and in general differential diagnostic considerations may include:

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