Post-traumatic cystic lesions of the bone, 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.
They are rare, but may be under recognised, 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 1-3.
Though mostly asymptomatic in nature, patients with these transient lesions can present with moderate soft swelling 1.
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 1.
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 1,3.
Typical appearances are that of a subcentimetre 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.
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:
- 1. Talawadekar GD, Muller M, Zahn H. Benign self-limiting cystic lesion after lower end radius fracture in a child. Indian J Orthop. 2009;43 (1): 99-101. doi:10.4103/0019-5413.45333 - Free text at pubmed - Pubmed citation
- 2. Dürr HR, Lienemann A, Stäbler A et-al. MRI of posttraumatic cyst-like lesions of bone after a greenstick fracture. Eur Radiol. 1997;7 (8): 1218-20. Pubmed citation
- 3. Asrian A, Shahabpour M, Tajdar F et-al. Posttraumatic cyst-like lesions of cortical bone in children. Acta Orthop Belg. 2010;76 (2): 264-8. Pubmed citation
- 4. Moore TE, King AR, Travis RC, Allen BC. Post-traumatic cysts and cyst-like lesions of bone. Skeletal radiology. 18 (2): 93-7. Pubmed
- 5. Lewandowski LR, Murphey MD, Potter BK. Posttraumatic cysts after pediatric fracture. Journal of pediatric orthopedics. 33 (3): 239-43. doi:10.1097/BPO.0b013e318280a63f - Pubmed