ULNAR & ULNOSTYLOD ABUTMENT

The abutment syndromes form another group of potential causes of ulnar sided symptoms.

Most commonly, the abutment refers to that of the distal ulna on the lunate or adjacent triquetral.

Usually the consequence of an elongated ulna compared with the radius (positive ulnar variance).

The TFC is convex in shape as it is pushed distally

Secondary changes are present in the articular cartilage of the adjacent lunate and proximal triquetral with changes also evident in the subchondral bone.

Ulnarstyloid abutment is a variation.

In this the ulnar styloid is prominent, either congenitally or following prior injury

Secondary impingement changes are generally confined to the triquetral and do not involve the lunate.

Combinations do occur and sometimes these conditions can be difficult to differentiate between degenerative

disease of the radiocarpal joint.

LOOK FOR

Positive ulnar variance Lunate chondromalacia Cartilage loss on the distal ulnar surface DRUJ joint effusions

Subchondral cysts Late arthropathy

Ulnar impaction syndrome is a different entiity.

This generally arises as a result of arthropathy of the distal radioulnar joint where the articular surface of the ulna impinges against the radius.

It can be mimiced by congenital abnormalities such as Negative ulnar variance and Madelungs deformity