"Trapped periosteum is an unusual complication of Salter-Harris I, II or III growth plate fractures. A flap of torn periosteum prolapses into the tensile aspect of the growth plate fracture preventing anatomic reduction and interfering with healing."
"In rat models, the periosteum in the physis can be degraded by giant cells; however, if it is surrounded by physeal cartilage, growth continues, and it slowly migrates towards the metaphysis 5."
"The radiograph of the affected limb will demonstrate widening of the affected part of the physis. A figure of 3 mm has been suggested to define abnormal widening 4; comparison radiographs of the unaffected side help to resolve uncertainty."