Ulnocarpal abutment syndrome:
= Ulnar impaction syndrome, Ulnar abutment, Ulnocarpal loading
Most common cause of ulnar sided impaction
Predisposing factors:
Positive ulnar variance, distal radial malunion, unrecognised DRUJ derangement
Imaging:
Positive ulnar variance (pronation and firm grip view can increase ulnar variance by 1-2 mm)
Chondromalacia of ulnar head, lunate and triquetral, subchondral degenerative changes later
Central perforation of TFC
Lunotriquetral ligament tear
End stage: OA of ulnocarpal joint and DRUJ
Distal radioulnar impingement syndrome
= Ulnar impingement syndrome:
Causes: surgery (e.g., Madelung deformity correction), RA, trauma, negative ulnar variance
Shortened distal ulna (proximal to sigmoid notch), impinging on the distal RADIUS (not carpal bones), proximal to sigmoid notch
Erosive changes to scalloping of distal radius
Radioulnar convergence
Ulnocarpal impaction secondary to ulnar styloid non-union:
Fracture ulnar styloid
Type 1: Intact TFC and stable DRUJ
Type 2: Avulsion of ulnar attachement of TFC (Palmer IB) with DRUJ instability
Chondromaclia, subchondral changes in the triquetral bone
Ulnar styloid impaction syndrome:
Excessively long ulnar styloid more than 6 mm
Ulnar styloid process index of more than 0.28 (Length of ulnar styloid – ulnar variance/ transverse diameter of ulnar head)
Chondromaclia, subchondral changes in the triquetral and ulnar styloid
Hamatolunate impingement syndrome:
Type II lunate bone (lunate articulates with hamate)
Chondromlacia, subchondral changes in the proximal pole of hamate
Reference:
1. Cerezal et al. Imaging findings in ulnar sided writst impaction syndromes
