Whenever reviewing a paediatric elbow the first consideration is to establish that all the expected epiphyses are present. These appear in the order defined by the mnemonic of CRITOL (Capitellum, Radial head, Internal epicondyle, Trochlea, Olecranon, Lateral epicondyle). Epiphyses appearing out of order can be due to avulsion-dislocation of an epiphysis. In this case only the first epiphysis, the capitellum, in its correct position. However, the capitellum is the “cap” that lies over the radial head. In this case we can see that a line drawn through the medulla of the radius, through its expected head location does not meet the capitellum. Therefore, the findings reflect dislocation of the proximal radius/radial head.
The combination of a mid-ulnar fracture and proximal radius/radial head dislocation constitutes the eponymous fracture-dislocation combination of Monteggia. This type of fracture dislocation highlights the importance of imaging the joint above and below a fracture. These types of fracture-dislocations are difficult for most to remember. The commonly confused fracture-dislocation is that of Galeazzi. In Galeazzi there is a mid-radial fracture with dislocation of the distal ulnar head at the wrist joint. It can be frustrating to remember the fracture and where the dislocation is (bone and location) and there are many mnemonics to assist. My preference is to recall that the dislocation occurs in the non-fractured bone and to use the mnemonic of GRIMUS (Galeazzi, Radius #, Inferior dislocation, Monteggia, Ulna #, Superior dislocation). Recall that the fracture may simply be a greenstick injury but it is essential to look for the associated dislocation as these can be missed and result in chronic pain/dysfunction for the patient and medicolegal pain for the reporting radiologist!
Finally don’t forget the final fracture dislocation which is the Essex-Lopresti (one hyphenated British surgeon not 2 people!). This is a comminuted fracture of the radial head where force is transmitted down the interosseous ligament resulting in dissociation of the distal radio-ulnar joint at the wrist.