The difficult diagnosis of cartilaginous tibial eminence fractures in young children

Purpose Anterior tibial eminence fracture is the main mode of ACL failure in patients with open physes. In young children, purely cartilaginous avulsions of the tibial ACL insertion are possible. The aim of this study was to focus on patients referred for misdiagnosed cartilaginous tibial eminence fractures. Methods Ten young patients with cartilaginous tibial eminence fractures were identified in the hospital database. Six of them were misdiagnosed and included in this retrospective case series. Clinical data at the time of injury, radiographs and MRI were analysed in order to evaluate the causes which could have led to inappropriate management. Results The patients’ median age at the time of injury was 7 years (5–8.5). The main cause of injury was a low-energy domestic accident ( n = 4). Radiographs at the time of injury were normal ( n = 4) or showed a very thin ossification ( n = 2). The traditional MRI findings of ACL injuries were all negative. On T2 sequences, an epiphyseal fluid signal allowed for a retrospective diagnosis. Cartilaginous tibial eminence fractures were regularly prolonged posteriorly giving a ‘double-PCL sign’ in 4 of the 6 patients. On a median of 6 months (2.5–48) after the injury, patients were referred for repeat giving ways ( n = 5) and/or limitation of extension or hyperextension ( n = 4). Symptoms were related to non-union, ossification and secondary enlargement of the avulsed fragment. Conclusions Post-traumatic knee joint effusions in children aged 9 or younger, even occurring after a low energy trauma and with normal radiographs, should suggest a cartilaginous tibial eminence fracture. Systematic MRI examinations should be mandatory in these patients in whom the avulsed fragment may appear as a double-PCL sign. During follow-up, new radiographs are recommended. A better knowledge of this rare entity should allow us to avoid misdiagnosis and to perform an early refixation of the avulsed fragment. Level of evidence III.