Middle aged female patient without history of known trauma. She complained of ulnar sided wrist pain. Review the radiograph and MR image to see if you can make the diagnosis. Then, scroll down for the case answer.
Ulnolunate Impaction Syndrome
The differential diagnosis for wrist pain is long. To narrow the list, it is helpful to triangulate the pain to the radial or ulnar side. Along the ulnar side, several common pathologic processes may occur including ulnolunate impaction syndrome, tears of the triangular fibrocartilage complex, arthritis, tedinopathy/tenosynovitis and fractures. Other findings, such as tumors, Kienböck’s disease, ulnar neurovascular bundle injury and ulnar impingement syndrome could be considered.
Ulnolunate impaction syndrome is usually associated with an ulna that is too long – a term called positive ulnar variance. Positive ulnar variance is defined when looking at a PA radiograph of the wrist in neutral position. A line parallel to the ulnar edge of the radial articular surface is drawn from radial to ulnar (lateral to medial). If the ulnar articular surface projects past this line (some use at least 2 mm as a distance), this is positive ulnar variance. It should be noted that forearm pronation and gripping will increase ulnar variance.
Ulnolunate impaction syndrome results from repetitive impaction of the ulna against the ulnar proximal side of the lunate and/or the radial proximal side of the triquetrum. Radiographically, this may manifest as cystic change and sclerosis in these regions (as seen on the radiographs). MRI will show loss of cartilage over the same regions with underlying bone marrow edema signal or cystic change on fluid sensitive fat suppressed images (red arrow). There may also be an associated tear of the triangular fibrocartilage complex and an effusion of the distal radioulnar joint.
When conservative management fails, common surgical procedures aim to shorten the ulnar length (in setting of positive ulnar variance). Such shortening procedures include an ulnar shortening osteotomy and a wafer procedure. For more information, see the link from orthobullets below:
Ulnolunate Impaction Syndrome Orthopedics: Click Here
