A RARE PRESENTATION OF IRREDUCIBLE POSTERIOR DISLOCATION OF ELBOW - RADIAL HEAD INTERPOSITION

ABSTRACT A case of irreducible dislocation of elbow with fractured radial neck (Mason type-IV) is described for its unusual presentation. A 56 year old lady from a remote rural area in Tamil nadu, India came to the outpatient clinic two weeks after trauma with pain, swelling and restricted dynamic deformity of the right elbow without any neurological deficit. In the immediate aftermath of trauma she had native treatment. The Radial head was found displaced into olecranon fossa and was preventing closed reduction. This was managed surgically by removal of radial head, closed reduction and k wire stabilization through a small posterior incision. This case is presented due to its rarity -only two cases has been reported so far in the literature. The rarity may be ascribed to the usual mechanism - the postero-lateral rotatory mechanism,which forces the radial head onto the capitellum, causing a fracture at the radial neck and the elbow dislocates posteriorly leaving the head anterior to or below the humerus. Thus radial head reaching the olecranon fossa cannot be explained this mechanism alone. The probable explanation in this case may be 1) The radial neck was fractured incompletely dragging the radial head along with it and the radial head may have got separated and stuck in the olecranon fossa on further manipulation. 2) Axial force on a flexed elbow could have caused the head fragment to displace posteriorly- but this is rare. 3) The radial neck could have got fractured entirely after the initial trauma due to the manipulation by traditional bone setters.