Keywords:
Trauma, Diagnostic procedure, Plain radiographic studies, MR, CT, Musculoskeletal bone
Authors:
G. Freire1, R. Cruz2, M. H. Valentim3, C. Silva1, T. G. Marques1, P. D. Afonso4; 1Loures/PT, 2PT, 3Lisboa/PT, 4Lisbon/PT
DOI:
10.1594/essr2018/P-0077
Background
Post-traumatic cyst-like lesions are an infrequent complication of fractures in children.
To our knowledge,
no more than 30 cases have been reported.1-4 They most commonly affect the distal radius following a greenstick or torus fracture.1 They are usually asymptomatic,
are not associated with pathologic fractures and typically resolve spontaneously in 1 to 3 years.2 Most are found in the distal radius,
with an age range of 2.5 to 15 years.1
Although etiology is still controversial,
the most accepted theory involves the transcortical leakage of intramedullary fat.3 During the fracture,
the elastic and loosely attached periosteum of children is easily lifted away from the cortex without disruption.
With the breaking of cortical and trabecular bone,
there is release of blood and intramedullary fat,
which collects under the unbreached periosteum within the subperiosteal haematoma.5 Posterior reabsorption and ossification of this haematoma enables the entrapped fat to become visible on plain radiographs.
This explains the time-lag of at least 3-4 weeks before their first appearance and the absence of growth of these lesions.5
Differential diagnosis should include,
amongst other entities,
osteomyelitis (Brodie abscess),
eosinophilic granuloma and aneurysmal bone cyst.1,3 Clinical history,
physical examination and review of previous radiographs are essential to exclude unrecognized pre-existing lesions or pathologic fractures.